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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/fs/namei.c
4 *
5 * Copyright (C) 1991, 1992 Linus Torvalds
6 */
7
8/*
9 * Some corrections by tytso.
10 */
11
12/* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
13 * lookup logic.
14 */
15/* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.
16 */
17
18#include <linux/init.h>
19#include <linux/export.h>
20#include <linux/kernel.h>
21#include <linux/slab.h>
22#include <linux/fs.h>
23#include <linux/filelock.h>
24#include <linux/namei.h>
25#include <linux/pagemap.h>
26#include <linux/sched/mm.h>
27#include <linux/fsnotify.h>
28#include <linux/personality.h>
29#include <linux/security.h>
30#include <linux/ima.h>
31#include <linux/syscalls.h>
32#include <linux/mount.h>
33#include <linux/audit.h>
34#include <linux/capability.h>
35#include <linux/file.h>
36#include <linux/fcntl.h>
37#include <linux/device_cgroup.h>
38#include <linux/fs_struct.h>
39#include <linux/posix_acl.h>
40#include <linux/hash.h>
41#include <linux/bitops.h>
42#include <linux/init_task.h>
43#include <linux/uaccess.h>
44
45#include "internal.h"
46#include "mount.h"
47
48/* [Feb-1997 T. Schoebel-Theuer]
49 * Fundamental changes in the pathname lookup mechanisms (namei)
50 * were necessary because of omirr. The reason is that omirr needs
51 * to know the _real_ pathname, not the user-supplied one, in case
52 * of symlinks (and also when transname replacements occur).
53 *
54 * The new code replaces the old recursive symlink resolution with
55 * an iterative one (in case of non-nested symlink chains). It does
56 * this with calls to <fs>_follow_link().
57 * As a side effect, dir_namei(), _namei() and follow_link() are now
58 * replaced with a single function lookup_dentry() that can handle all
59 * the special cases of the former code.
60 *
61 * With the new dcache, the pathname is stored at each inode, at least as
62 * long as the refcount of the inode is positive. As a side effect, the
63 * size of the dcache depends on the inode cache and thus is dynamic.
64 *
65 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
66 * resolution to correspond with current state of the code.
67 *
68 * Note that the symlink resolution is not *completely* iterative.
69 * There is still a significant amount of tail- and mid- recursion in
70 * the algorithm. Also, note that <fs>_readlink() is not used in
71 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
72 * may return different results than <fs>_follow_link(). Many virtual
73 * filesystems (including /proc) exhibit this behavior.
74 */
75
76/* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
77 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
78 * and the name already exists in form of a symlink, try to create the new
79 * name indicated by the symlink. The old code always complained that the
80 * name already exists, due to not following the symlink even if its target
81 * is nonexistent. The new semantics affects also mknod() and link() when
82 * the name is a symlink pointing to a non-existent name.
83 *
84 * I don't know which semantics is the right one, since I have no access
85 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
86 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
87 * "old" one. Personally, I think the new semantics is much more logical.
88 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
89 * file does succeed in both HP-UX and SunOs, but not in Solaris
90 * and in the old Linux semantics.
91 */
92
93/* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
94 * semantics. See the comments in "open_namei" and "do_link" below.
95 *
96 * [10-Sep-98 Alan Modra] Another symlink change.
97 */
98
99/* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
100 * inside the path - always follow.
101 * in the last component in creation/removal/renaming - never follow.
102 * if LOOKUP_FOLLOW passed - follow.
103 * if the pathname has trailing slashes - follow.
104 * otherwise - don't follow.
105 * (applied in that order).
106 *
107 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
108 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
109 * During the 2.4 we need to fix the userland stuff depending on it -
110 * hopefully we will be able to get rid of that wart in 2.5. So far only
111 * XEmacs seems to be relying on it...
112 */
113/*
114 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
115 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
116 * any extra contention...
117 */
118
119/* In order to reduce some races, while at the same time doing additional
120 * checking and hopefully speeding things up, we copy filenames to the
121 * kernel data space before using them..
122 *
123 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
124 * PATH_MAX includes the nul terminator --RR.
125 */
126
127#define EMBEDDED_NAME_MAX (PATH_MAX - offsetof(struct filename, iname))
128
129struct filename *
130getname_flags(const char __user *filename, int flags, int *empty)
131{
132 struct filename *result;
133 char *kname;
134 int len;
135
136 result = audit_reusename(filename);
137 if (result)
138 return result;
139
140 result = __getname();
141 if (unlikely(!result))
142 return ERR_PTR(-ENOMEM);
143
144 /*
145 * First, try to embed the struct filename inside the names_cache
146 * allocation
147 */
148 kname = (char *)result->iname;
149 result->name = kname;
150
151 len = strncpy_from_user(kname, filename, EMBEDDED_NAME_MAX);
152 if (unlikely(len < 0)) {
153 __putname(result);
154 return ERR_PTR(len);
155 }
156
157 /*
158 * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a
159 * separate struct filename so we can dedicate the entire
160 * names_cache allocation for the pathname, and re-do the copy from
161 * userland.
162 */
163 if (unlikely(len == EMBEDDED_NAME_MAX)) {
164 const size_t size = offsetof(struct filename, iname[1]);
165 kname = (char *)result;
166
167 /*
168 * size is chosen that way we to guarantee that
169 * result->iname[0] is within the same object and that
170 * kname can't be equal to result->iname, no matter what.
171 */
172 result = kzalloc(size, GFP_KERNEL);
173 if (unlikely(!result)) {
174 __putname(kname);
175 return ERR_PTR(-ENOMEM);
176 }
177 result->name = kname;
178 len = strncpy_from_user(kname, filename, PATH_MAX);
179 if (unlikely(len < 0)) {
180 __putname(kname);
181 kfree(result);
182 return ERR_PTR(len);
183 }
184 if (unlikely(len == PATH_MAX)) {
185 __putname(kname);
186 kfree(result);
187 return ERR_PTR(-ENAMETOOLONG);
188 }
189 }
190
191 atomic_set(&result->refcnt, 1);
192 /* The empty path is special. */
193 if (unlikely(!len)) {
194 if (empty)
195 *empty = 1;
196 if (!(flags & LOOKUP_EMPTY)) {
197 putname(result);
198 return ERR_PTR(-ENOENT);
199 }
200 }
201
202 result->uptr = filename;
203 result->aname = NULL;
204 audit_getname(result);
205 return result;
206}
207
208struct filename *
209getname_uflags(const char __user *filename, int uflags)
210{
211 int flags = (uflags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
212
213 return getname_flags(filename, flags, NULL);
214}
215
216struct filename *
217getname(const char __user * filename)
218{
219 return getname_flags(filename, 0, NULL);
220}
221
222struct filename *
223getname_kernel(const char * filename)
224{
225 struct filename *result;
226 int len = strlen(filename) + 1;
227
228 result = __getname();
229 if (unlikely(!result))
230 return ERR_PTR(-ENOMEM);
231
232 if (len <= EMBEDDED_NAME_MAX) {
233 result->name = (char *)result->iname;
234 } else if (len <= PATH_MAX) {
235 const size_t size = offsetof(struct filename, iname[1]);
236 struct filename *tmp;
237
238 tmp = kmalloc(size, GFP_KERNEL);
239 if (unlikely(!tmp)) {
240 __putname(result);
241 return ERR_PTR(-ENOMEM);
242 }
243 tmp->name = (char *)result;
244 result = tmp;
245 } else {
246 __putname(result);
247 return ERR_PTR(-ENAMETOOLONG);
248 }
249 memcpy((char *)result->name, filename, len);
250 result->uptr = NULL;
251 result->aname = NULL;
252 atomic_set(&result->refcnt, 1);
253 audit_getname(result);
254
255 return result;
256}
257EXPORT_SYMBOL(getname_kernel);
258
259void putname(struct filename *name)
260{
261 if (IS_ERR(name))
262 return;
263
264 if (WARN_ON_ONCE(!atomic_read(&name->refcnt)))
265 return;
266
267 if (!atomic_dec_and_test(&name->refcnt))
268 return;
269
270 if (name->name != name->iname) {
271 __putname(name->name);
272 kfree(name);
273 } else
274 __putname(name);
275}
276EXPORT_SYMBOL(putname);
277
278/**
279 * check_acl - perform ACL permission checking
280 * @idmap: idmap of the mount the inode was found from
281 * @inode: inode to check permissions on
282 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC ...)
283 *
284 * This function performs the ACL permission checking. Since this function
285 * retrieve POSIX acls it needs to know whether it is called from a blocking or
286 * non-blocking context and thus cares about the MAY_NOT_BLOCK bit.
287 *
288 * If the inode has been found through an idmapped mount the idmap of
289 * the vfsmount must be passed through @idmap. This function will then take
290 * care to map the inode according to @idmap before checking permissions.
291 * On non-idmapped mounts or if permission checking is to be performed on the
292 * raw inode simply pass @nop_mnt_idmap.
293 */
294static int check_acl(struct mnt_idmap *idmap,
295 struct inode *inode, int mask)
296{
297#ifdef CONFIG_FS_POSIX_ACL
298 struct posix_acl *acl;
299
300 if (mask & MAY_NOT_BLOCK) {
301 acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS);
302 if (!acl)
303 return -EAGAIN;
304 /* no ->get_inode_acl() calls in RCU mode... */
305 if (is_uncached_acl(acl))
306 return -ECHILD;
307 return posix_acl_permission(idmap, inode, acl, mask);
308 }
309
310 acl = get_inode_acl(inode, ACL_TYPE_ACCESS);
311 if (IS_ERR(acl))
312 return PTR_ERR(acl);
313 if (acl) {
314 int error = posix_acl_permission(idmap, inode, acl, mask);
315 posix_acl_release(acl);
316 return error;
317 }
318#endif
319
320 return -EAGAIN;
321}
322
323/**
324 * acl_permission_check - perform basic UNIX permission checking
325 * @idmap: idmap of the mount the inode was found from
326 * @inode: inode to check permissions on
327 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC ...)
328 *
329 * This function performs the basic UNIX permission checking. Since this
330 * function may retrieve POSIX acls it needs to know whether it is called from a
331 * blocking or non-blocking context and thus cares about the MAY_NOT_BLOCK bit.
332 *
333 * If the inode has been found through an idmapped mount the idmap of
334 * the vfsmount must be passed through @idmap. This function will then take
335 * care to map the inode according to @idmap before checking permissions.
336 * On non-idmapped mounts or if permission checking is to be performed on the
337 * raw inode simply pass @nop_mnt_idmap.
338 */
339static int acl_permission_check(struct mnt_idmap *idmap,
340 struct inode *inode, int mask)
341{
342 unsigned int mode = inode->i_mode;
343 vfsuid_t vfsuid;
344
345 /* Are we the owner? If so, ACL's don't matter */
346 vfsuid = i_uid_into_vfsuid(idmap, inode);
347 if (likely(vfsuid_eq_kuid(vfsuid, current_fsuid()))) {
348 mask &= 7;
349 mode >>= 6;
350 return (mask & ~mode) ? -EACCES : 0;
351 }
352
353 /* Do we have ACL's? */
354 if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
355 int error = check_acl(idmap, inode, mask);
356 if (error != -EAGAIN)
357 return error;
358 }
359
360 /* Only RWX matters for group/other mode bits */
361 mask &= 7;
362
363 /*
364 * Are the group permissions different from
365 * the other permissions in the bits we care
366 * about? Need to check group ownership if so.
367 */
368 if (mask & (mode ^ (mode >> 3))) {
369 vfsgid_t vfsgid = i_gid_into_vfsgid(idmap, inode);
370 if (vfsgid_in_group_p(vfsgid))
371 mode >>= 3;
372 }
373
374 /* Bits in 'mode' clear that we require? */
375 return (mask & ~mode) ? -EACCES : 0;
376}
377
378/**
379 * generic_permission - check for access rights on a Posix-like filesystem
380 * @idmap: idmap of the mount the inode was found from
381 * @inode: inode to check access rights for
382 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC,
383 * %MAY_NOT_BLOCK ...)
384 *
385 * Used to check for read/write/execute permissions on a file.
386 * We use "fsuid" for this, letting us set arbitrary permissions
387 * for filesystem access without changing the "normal" uids which
388 * are used for other things.
389 *
390 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
391 * request cannot be satisfied (eg. requires blocking or too much complexity).
392 * It would then be called again in ref-walk mode.
393 *
394 * If the inode has been found through an idmapped mount the idmap of
395 * the vfsmount must be passed through @idmap. This function will then take
396 * care to map the inode according to @idmap before checking permissions.
397 * On non-idmapped mounts or if permission checking is to be performed on the
398 * raw inode simply pass @nop_mnt_idmap.
399 */
400int generic_permission(struct mnt_idmap *idmap, struct inode *inode,
401 int mask)
402{
403 int ret;
404
405 /*
406 * Do the basic permission checks.
407 */
408 ret = acl_permission_check(idmap, inode, mask);
409 if (ret != -EACCES)
410 return ret;
411
412 if (S_ISDIR(inode->i_mode)) {
413 /* DACs are overridable for directories */
414 if (!(mask & MAY_WRITE))
415 if (capable_wrt_inode_uidgid(idmap, inode,
416 CAP_DAC_READ_SEARCH))
417 return 0;
418 if (capable_wrt_inode_uidgid(idmap, inode,
419 CAP_DAC_OVERRIDE))
420 return 0;
421 return -EACCES;
422 }
423
424 /*
425 * Searching includes executable on directories, else just read.
426 */
427 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
428 if (mask == MAY_READ)
429 if (capable_wrt_inode_uidgid(idmap, inode,
430 CAP_DAC_READ_SEARCH))
431 return 0;
432 /*
433 * Read/write DACs are always overridable.
434 * Executable DACs are overridable when there is
435 * at least one exec bit set.
436 */
437 if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
438 if (capable_wrt_inode_uidgid(idmap, inode,
439 CAP_DAC_OVERRIDE))
440 return 0;
441
442 return -EACCES;
443}
444EXPORT_SYMBOL(generic_permission);
445
446/**
447 * do_inode_permission - UNIX permission checking
448 * @idmap: idmap of the mount the inode was found from
449 * @inode: inode to check permissions on
450 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC ...)
451 *
452 * We _really_ want to just do "generic_permission()" without
453 * even looking at the inode->i_op values. So we keep a cache
454 * flag in inode->i_opflags, that says "this has not special
455 * permission function, use the fast case".
456 */
457static inline int do_inode_permission(struct mnt_idmap *idmap,
458 struct inode *inode, int mask)
459{
460 if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) {
461 if (likely(inode->i_op->permission))
462 return inode->i_op->permission(idmap, inode, mask);
463
464 /* This gets set once for the inode lifetime */
465 spin_lock(&inode->i_lock);
466 inode->i_opflags |= IOP_FASTPERM;
467 spin_unlock(&inode->i_lock);
468 }
469 return generic_permission(idmap, inode, mask);
470}
471
472/**
473 * sb_permission - Check superblock-level permissions
474 * @sb: Superblock of inode to check permission on
475 * @inode: Inode to check permission on
476 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
477 *
478 * Separate out file-system wide checks from inode-specific permission checks.
479 */
480static int sb_permission(struct super_block *sb, struct inode *inode, int mask)
481{
482 if (unlikely(mask & MAY_WRITE)) {
483 umode_t mode = inode->i_mode;
484
485 /* Nobody gets write access to a read-only fs. */
486 if (sb_rdonly(sb) && (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
487 return -EROFS;
488 }
489 return 0;
490}
491
492/**
493 * inode_permission - Check for access rights to a given inode
494 * @idmap: idmap of the mount the inode was found from
495 * @inode: Inode to check permission on
496 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
497 *
498 * Check for read/write/execute permissions on an inode. We use fs[ug]id for
499 * this, letting us set arbitrary permissions for filesystem access without
500 * changing the "normal" UIDs which are used for other things.
501 *
502 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
503 */
504int inode_permission(struct mnt_idmap *idmap,
505 struct inode *inode, int mask)
506{
507 int retval;
508
509 retval = sb_permission(inode->i_sb, inode, mask);
510 if (retval)
511 return retval;
512
513 if (unlikely(mask & MAY_WRITE)) {
514 /*
515 * Nobody gets write access to an immutable file.
516 */
517 if (IS_IMMUTABLE(inode))
518 return -EPERM;
519
520 /*
521 * Updating mtime will likely cause i_uid and i_gid to be
522 * written back improperly if their true value is unknown
523 * to the vfs.
524 */
525 if (HAS_UNMAPPED_ID(idmap, inode))
526 return -EACCES;
527 }
528
529 retval = do_inode_permission(idmap, inode, mask);
530 if (retval)
531 return retval;
532
533 retval = devcgroup_inode_permission(inode, mask);
534 if (retval)
535 return retval;
536
537 return security_inode_permission(inode, mask);
538}
539EXPORT_SYMBOL(inode_permission);
540
541/**
542 * path_get - get a reference to a path
543 * @path: path to get the reference to
544 *
545 * Given a path increment the reference count to the dentry and the vfsmount.
546 */
547void path_get(const struct path *path)
548{
549 mntget(path->mnt);
550 dget(path->dentry);
551}
552EXPORT_SYMBOL(path_get);
553
554/**
555 * path_put - put a reference to a path
556 * @path: path to put the reference to
557 *
558 * Given a path decrement the reference count to the dentry and the vfsmount.
559 */
560void path_put(const struct path *path)
561{
562 dput(path->dentry);
563 mntput(path->mnt);
564}
565EXPORT_SYMBOL(path_put);
566
567#define EMBEDDED_LEVELS 2
568struct nameidata {
569 struct path path;
570 struct qstr last;
571 struct path root;
572 struct inode *inode; /* path.dentry.d_inode */
573 unsigned int flags, state;
574 unsigned seq, next_seq, m_seq, r_seq;
575 int last_type;
576 unsigned depth;
577 int total_link_count;
578 struct saved {
579 struct path link;
580 struct delayed_call done;
581 const char *name;
582 unsigned seq;
583 } *stack, internal[EMBEDDED_LEVELS];
584 struct filename *name;
585 struct nameidata *saved;
586 unsigned root_seq;
587 int dfd;
588 vfsuid_t dir_vfsuid;
589 umode_t dir_mode;
590} __randomize_layout;
591
592#define ND_ROOT_PRESET 1
593#define ND_ROOT_GRABBED 2
594#define ND_JUMPED 4
595
596static void __set_nameidata(struct nameidata *p, int dfd, struct filename *name)
597{
598 struct nameidata *old = current->nameidata;
599 p->stack = p->internal;
600 p->depth = 0;
601 p->dfd = dfd;
602 p->name = name;
603 p->path.mnt = NULL;
604 p->path.dentry = NULL;
605 p->total_link_count = old ? old->total_link_count : 0;
606 p->saved = old;
607 current->nameidata = p;
608}
609
610static inline void set_nameidata(struct nameidata *p, int dfd, struct filename *name,
611 const struct path *root)
612{
613 __set_nameidata(p, dfd, name);
614 p->state = 0;
615 if (unlikely(root)) {
616 p->state = ND_ROOT_PRESET;
617 p->root = *root;
618 }
619}
620
621static void restore_nameidata(void)
622{
623 struct nameidata *now = current->nameidata, *old = now->saved;
624
625 current->nameidata = old;
626 if (old)
627 old->total_link_count = now->total_link_count;
628 if (now->stack != now->internal)
629 kfree(now->stack);
630}
631
632static bool nd_alloc_stack(struct nameidata *nd)
633{
634 struct saved *p;
635
636 p= kmalloc_array(MAXSYMLINKS, sizeof(struct saved),
637 nd->flags & LOOKUP_RCU ? GFP_ATOMIC : GFP_KERNEL);
638 if (unlikely(!p))
639 return false;
640 memcpy(p, nd->internal, sizeof(nd->internal));
641 nd->stack = p;
642 return true;
643}
644
645/**
646 * path_connected - Verify that a dentry is below mnt.mnt_root
647 * @mnt: The mountpoint to check.
648 * @dentry: The dentry to check.
649 *
650 * Rename can sometimes move a file or directory outside of a bind
651 * mount, path_connected allows those cases to be detected.
652 */
653static bool path_connected(struct vfsmount *mnt, struct dentry *dentry)
654{
655 struct super_block *sb = mnt->mnt_sb;
656
657 /* Bind mounts can have disconnected paths */
658 if (mnt->mnt_root == sb->s_root)
659 return true;
660
661 return is_subdir(dentry, mnt->mnt_root);
662}
663
664static void drop_links(struct nameidata *nd)
665{
666 int i = nd->depth;
667 while (i--) {
668 struct saved *last = nd->stack + i;
669 do_delayed_call(&last->done);
670 clear_delayed_call(&last->done);
671 }
672}
673
674static void leave_rcu(struct nameidata *nd)
675{
676 nd->flags &= ~LOOKUP_RCU;
677 nd->seq = nd->next_seq = 0;
678 rcu_read_unlock();
679}
680
681static void terminate_walk(struct nameidata *nd)
682{
683 drop_links(nd);
684 if (!(nd->flags & LOOKUP_RCU)) {
685 int i;
686 path_put(&nd->path);
687 for (i = 0; i < nd->depth; i++)
688 path_put(&nd->stack[i].link);
689 if (nd->state & ND_ROOT_GRABBED) {
690 path_put(&nd->root);
691 nd->state &= ~ND_ROOT_GRABBED;
692 }
693 } else {
694 leave_rcu(nd);
695 }
696 nd->depth = 0;
697 nd->path.mnt = NULL;
698 nd->path.dentry = NULL;
699}
700
701/* path_put is needed afterwards regardless of success or failure */
702static bool __legitimize_path(struct path *path, unsigned seq, unsigned mseq)
703{
704 int res = __legitimize_mnt(path->mnt, mseq);
705 if (unlikely(res)) {
706 if (res > 0)
707 path->mnt = NULL;
708 path->dentry = NULL;
709 return false;
710 }
711 if (unlikely(!lockref_get_not_dead(&path->dentry->d_lockref))) {
712 path->dentry = NULL;
713 return false;
714 }
715 return !read_seqcount_retry(&path->dentry->d_seq, seq);
716}
717
718static inline bool legitimize_path(struct nameidata *nd,
719 struct path *path, unsigned seq)
720{
721 return __legitimize_path(path, seq, nd->m_seq);
722}
723
724static bool legitimize_links(struct nameidata *nd)
725{
726 int i;
727 if (unlikely(nd->flags & LOOKUP_CACHED)) {
728 drop_links(nd);
729 nd->depth = 0;
730 return false;
731 }
732 for (i = 0; i < nd->depth; i++) {
733 struct saved *last = nd->stack + i;
734 if (unlikely(!legitimize_path(nd, &last->link, last->seq))) {
735 drop_links(nd);
736 nd->depth = i + 1;
737 return false;
738 }
739 }
740 return true;
741}
742
743static bool legitimize_root(struct nameidata *nd)
744{
745 /* Nothing to do if nd->root is zero or is managed by the VFS user. */
746 if (!nd->root.mnt || (nd->state & ND_ROOT_PRESET))
747 return true;
748 nd->state |= ND_ROOT_GRABBED;
749 return legitimize_path(nd, &nd->root, nd->root_seq);
750}
751
752/*
753 * Path walking has 2 modes, rcu-walk and ref-walk (see
754 * Documentation/filesystems/path-lookup.txt). In situations when we can't
755 * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
756 * normal reference counts on dentries and vfsmounts to transition to ref-walk
757 * mode. Refcounts are grabbed at the last known good point before rcu-walk
758 * got stuck, so ref-walk may continue from there. If this is not successful
759 * (eg. a seqcount has changed), then failure is returned and it's up to caller
760 * to restart the path walk from the beginning in ref-walk mode.
761 */
762
763/**
764 * try_to_unlazy - try to switch to ref-walk mode.
765 * @nd: nameidata pathwalk data
766 * Returns: true on success, false on failure
767 *
768 * try_to_unlazy attempts to legitimize the current nd->path and nd->root
769 * for ref-walk mode.
770 * Must be called from rcu-walk context.
771 * Nothing should touch nameidata between try_to_unlazy() failure and
772 * terminate_walk().
773 */
774static bool try_to_unlazy(struct nameidata *nd)
775{
776 struct dentry *parent = nd->path.dentry;
777
778 BUG_ON(!(nd->flags & LOOKUP_RCU));
779
780 if (unlikely(!legitimize_links(nd)))
781 goto out1;
782 if (unlikely(!legitimize_path(nd, &nd->path, nd->seq)))
783 goto out;
784 if (unlikely(!legitimize_root(nd)))
785 goto out;
786 leave_rcu(nd);
787 BUG_ON(nd->inode != parent->d_inode);
788 return true;
789
790out1:
791 nd->path.mnt = NULL;
792 nd->path.dentry = NULL;
793out:
794 leave_rcu(nd);
795 return false;
796}
797
798/**
799 * try_to_unlazy_next - try to switch to ref-walk mode.
800 * @nd: nameidata pathwalk data
801 * @dentry: next dentry to step into
802 * Returns: true on success, false on failure
803 *
804 * Similar to try_to_unlazy(), but here we have the next dentry already
805 * picked by rcu-walk and want to legitimize that in addition to the current
806 * nd->path and nd->root for ref-walk mode. Must be called from rcu-walk context.
807 * Nothing should touch nameidata between try_to_unlazy_next() failure and
808 * terminate_walk().
809 */
810static bool try_to_unlazy_next(struct nameidata *nd, struct dentry *dentry)
811{
812 int res;
813 BUG_ON(!(nd->flags & LOOKUP_RCU));
814
815 if (unlikely(!legitimize_links(nd)))
816 goto out2;
817 res = __legitimize_mnt(nd->path.mnt, nd->m_seq);
818 if (unlikely(res)) {
819 if (res > 0)
820 goto out2;
821 goto out1;
822 }
823 if (unlikely(!lockref_get_not_dead(&nd->path.dentry->d_lockref)))
824 goto out1;
825
826 /*
827 * We need to move both the parent and the dentry from the RCU domain
828 * to be properly refcounted. And the sequence number in the dentry
829 * validates *both* dentry counters, since we checked the sequence
830 * number of the parent after we got the child sequence number. So we
831 * know the parent must still be valid if the child sequence number is
832 */
833 if (unlikely(!lockref_get_not_dead(&dentry->d_lockref)))
834 goto out;
835 if (read_seqcount_retry(&dentry->d_seq, nd->next_seq))
836 goto out_dput;
837 /*
838 * Sequence counts matched. Now make sure that the root is
839 * still valid and get it if required.
840 */
841 if (unlikely(!legitimize_root(nd)))
842 goto out_dput;
843 leave_rcu(nd);
844 return true;
845
846out2:
847 nd->path.mnt = NULL;
848out1:
849 nd->path.dentry = NULL;
850out:
851 leave_rcu(nd);
852 return false;
853out_dput:
854 leave_rcu(nd);
855 dput(dentry);
856 return false;
857}
858
859static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
860{
861 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE))
862 return dentry->d_op->d_revalidate(dentry, flags);
863 else
864 return 1;
865}
866
867/**
868 * complete_walk - successful completion of path walk
869 * @nd: pointer nameidata
870 *
871 * If we had been in RCU mode, drop out of it and legitimize nd->path.
872 * Revalidate the final result, unless we'd already done that during
873 * the path walk or the filesystem doesn't ask for it. Return 0 on
874 * success, -error on failure. In case of failure caller does not
875 * need to drop nd->path.
876 */
877static int complete_walk(struct nameidata *nd)
878{
879 struct dentry *dentry = nd->path.dentry;
880 int status;
881
882 if (nd->flags & LOOKUP_RCU) {
883 /*
884 * We don't want to zero nd->root for scoped-lookups or
885 * externally-managed nd->root.
886 */
887 if (!(nd->state & ND_ROOT_PRESET))
888 if (!(nd->flags & LOOKUP_IS_SCOPED))
889 nd->root.mnt = NULL;
890 nd->flags &= ~LOOKUP_CACHED;
891 if (!try_to_unlazy(nd))
892 return -ECHILD;
893 }
894
895 if (unlikely(nd->flags & LOOKUP_IS_SCOPED)) {
896 /*
897 * While the guarantee of LOOKUP_IS_SCOPED is (roughly) "don't
898 * ever step outside the root during lookup" and should already
899 * be guaranteed by the rest of namei, we want to avoid a namei
900 * BUG resulting in userspace being given a path that was not
901 * scoped within the root at some point during the lookup.
902 *
903 * So, do a final sanity-check to make sure that in the
904 * worst-case scenario (a complete bypass of LOOKUP_IS_SCOPED)
905 * we won't silently return an fd completely outside of the
906 * requested root to userspace.
907 *
908 * Userspace could move the path outside the root after this
909 * check, but as discussed elsewhere this is not a concern (the
910 * resolved file was inside the root at some point).
911 */
912 if (!path_is_under(&nd->path, &nd->root))
913 return -EXDEV;
914 }
915
916 if (likely(!(nd->state & ND_JUMPED)))
917 return 0;
918
919 if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE)))
920 return 0;
921
922 status = dentry->d_op->d_weak_revalidate(dentry, nd->flags);
923 if (status > 0)
924 return 0;
925
926 if (!status)
927 status = -ESTALE;
928
929 return status;
930}
931
932static int set_root(struct nameidata *nd)
933{
934 struct fs_struct *fs = current->fs;
935
936 /*
937 * Jumping to the real root in a scoped-lookup is a BUG in namei, but we
938 * still have to ensure it doesn't happen because it will cause a breakout
939 * from the dirfd.
940 */
941 if (WARN_ON(nd->flags & LOOKUP_IS_SCOPED))
942 return -ENOTRECOVERABLE;
943
944 if (nd->flags & LOOKUP_RCU) {
945 unsigned seq;
946
947 do {
948 seq = read_seqcount_begin(&fs->seq);
949 nd->root = fs->root;
950 nd->root_seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
951 } while (read_seqcount_retry(&fs->seq, seq));
952 } else {
953 get_fs_root(fs, &nd->root);
954 nd->state |= ND_ROOT_GRABBED;
955 }
956 return 0;
957}
958
959static int nd_jump_root(struct nameidata *nd)
960{
961 if (unlikely(nd->flags & LOOKUP_BENEATH))
962 return -EXDEV;
963 if (unlikely(nd->flags & LOOKUP_NO_XDEV)) {
964 /* Absolute path arguments to path_init() are allowed. */
965 if (nd->path.mnt != NULL && nd->path.mnt != nd->root.mnt)
966 return -EXDEV;
967 }
968 if (!nd->root.mnt) {
969 int error = set_root(nd);
970 if (error)
971 return error;
972 }
973 if (nd->flags & LOOKUP_RCU) {
974 struct dentry *d;
975 nd->path = nd->root;
976 d = nd->path.dentry;
977 nd->inode = d->d_inode;
978 nd->seq = nd->root_seq;
979 if (read_seqcount_retry(&d->d_seq, nd->seq))
980 return -ECHILD;
981 } else {
982 path_put(&nd->path);
983 nd->path = nd->root;
984 path_get(&nd->path);
985 nd->inode = nd->path.dentry->d_inode;
986 }
987 nd->state |= ND_JUMPED;
988 return 0;
989}
990
991/*
992 * Helper to directly jump to a known parsed path from ->get_link,
993 * caller must have taken a reference to path beforehand.
994 */
995int nd_jump_link(const struct path *path)
996{
997 int error = -ELOOP;
998 struct nameidata *nd = current->nameidata;
999
1000 if (unlikely(nd->flags & LOOKUP_NO_MAGICLINKS))
1001 goto err;
1002
1003 error = -EXDEV;
1004 if (unlikely(nd->flags & LOOKUP_NO_XDEV)) {
1005 if (nd->path.mnt != path->mnt)
1006 goto err;
1007 }
1008 /* Not currently safe for scoped-lookups. */
1009 if (unlikely(nd->flags & LOOKUP_IS_SCOPED))
1010 goto err;
1011
1012 path_put(&nd->path);
1013 nd->path = *path;
1014 nd->inode = nd->path.dentry->d_inode;
1015 nd->state |= ND_JUMPED;
1016 return 0;
1017
1018err:
1019 path_put(path);
1020 return error;
1021}
1022
1023static inline void put_link(struct nameidata *nd)
1024{
1025 struct saved *last = nd->stack + --nd->depth;
1026 do_delayed_call(&last->done);
1027 if (!(nd->flags & LOOKUP_RCU))
1028 path_put(&last->link);
1029}
1030
1031static int sysctl_protected_symlinks __read_mostly;
1032static int sysctl_protected_hardlinks __read_mostly;
1033static int sysctl_protected_fifos __read_mostly;
1034static int sysctl_protected_regular __read_mostly;
1035
1036#ifdef CONFIG_SYSCTL
1037static struct ctl_table namei_sysctls[] = {
1038 {
1039 .procname = "protected_symlinks",
1040 .data = &sysctl_protected_symlinks,
1041 .maxlen = sizeof(int),
1042 .mode = 0644,
1043 .proc_handler = proc_dointvec_minmax,
1044 .extra1 = SYSCTL_ZERO,
1045 .extra2 = SYSCTL_ONE,
1046 },
1047 {
1048 .procname = "protected_hardlinks",
1049 .data = &sysctl_protected_hardlinks,
1050 .maxlen = sizeof(int),
1051 .mode = 0644,
1052 .proc_handler = proc_dointvec_minmax,
1053 .extra1 = SYSCTL_ZERO,
1054 .extra2 = SYSCTL_ONE,
1055 },
1056 {
1057 .procname = "protected_fifos",
1058 .data = &sysctl_protected_fifos,
1059 .maxlen = sizeof(int),
1060 .mode = 0644,
1061 .proc_handler = proc_dointvec_minmax,
1062 .extra1 = SYSCTL_ZERO,
1063 .extra2 = SYSCTL_TWO,
1064 },
1065 {
1066 .procname = "protected_regular",
1067 .data = &sysctl_protected_regular,
1068 .maxlen = sizeof(int),
1069 .mode = 0644,
1070 .proc_handler = proc_dointvec_minmax,
1071 .extra1 = SYSCTL_ZERO,
1072 .extra2 = SYSCTL_TWO,
1073 },
1074};
1075
1076static int __init init_fs_namei_sysctls(void)
1077{
1078 register_sysctl_init("fs", namei_sysctls);
1079 return 0;
1080}
1081fs_initcall(init_fs_namei_sysctls);
1082
1083#endif /* CONFIG_SYSCTL */
1084
1085/**
1086 * may_follow_link - Check symlink following for unsafe situations
1087 * @nd: nameidata pathwalk data
1088 * @inode: Used for idmapping.
1089 *
1090 * In the case of the sysctl_protected_symlinks sysctl being enabled,
1091 * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
1092 * in a sticky world-writable directory. This is to protect privileged
1093 * processes from failing races against path names that may change out
1094 * from under them by way of other users creating malicious symlinks.
1095 * It will permit symlinks to be followed only when outside a sticky
1096 * world-writable directory, or when the uid of the symlink and follower
1097 * match, or when the directory owner matches the symlink's owner.
1098 *
1099 * Returns 0 if following the symlink is allowed, -ve on error.
1100 */
1101static inline int may_follow_link(struct nameidata *nd, const struct inode *inode)
1102{
1103 struct mnt_idmap *idmap;
1104 vfsuid_t vfsuid;
1105
1106 if (!sysctl_protected_symlinks)
1107 return 0;
1108
1109 idmap = mnt_idmap(nd->path.mnt);
1110 vfsuid = i_uid_into_vfsuid(idmap, inode);
1111 /* Allowed if owner and follower match. */
1112 if (vfsuid_eq_kuid(vfsuid, current_fsuid()))
1113 return 0;
1114
1115 /* Allowed if parent directory not sticky and world-writable. */
1116 if ((nd->dir_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH))
1117 return 0;
1118
1119 /* Allowed if parent directory and link owner match. */
1120 if (vfsuid_valid(nd->dir_vfsuid) && vfsuid_eq(nd->dir_vfsuid, vfsuid))
1121 return 0;
1122
1123 if (nd->flags & LOOKUP_RCU)
1124 return -ECHILD;
1125
1126 audit_inode(nd->name, nd->stack[0].link.dentry, 0);
1127 audit_log_path_denied(AUDIT_ANOM_LINK, "follow_link");
1128 return -EACCES;
1129}
1130
1131/**
1132 * safe_hardlink_source - Check for safe hardlink conditions
1133 * @idmap: idmap of the mount the inode was found from
1134 * @inode: the source inode to hardlink from
1135 *
1136 * Return false if at least one of the following conditions:
1137 * - inode is not a regular file
1138 * - inode is setuid
1139 * - inode is setgid and group-exec
1140 * - access failure for read and write
1141 *
1142 * Otherwise returns true.
1143 */
1144static bool safe_hardlink_source(struct mnt_idmap *idmap,
1145 struct inode *inode)
1146{
1147 umode_t mode = inode->i_mode;
1148
1149 /* Special files should not get pinned to the filesystem. */
1150 if (!S_ISREG(mode))
1151 return false;
1152
1153 /* Setuid files should not get pinned to the filesystem. */
1154 if (mode & S_ISUID)
1155 return false;
1156
1157 /* Executable setgid files should not get pinned to the filesystem. */
1158 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP))
1159 return false;
1160
1161 /* Hardlinking to unreadable or unwritable sources is dangerous. */
1162 if (inode_permission(idmap, inode, MAY_READ | MAY_WRITE))
1163 return false;
1164
1165 return true;
1166}
1167
1168/**
1169 * may_linkat - Check permissions for creating a hardlink
1170 * @idmap: idmap of the mount the inode was found from
1171 * @link: the source to hardlink from
1172 *
1173 * Block hardlink when all of:
1174 * - sysctl_protected_hardlinks enabled
1175 * - fsuid does not match inode
1176 * - hardlink source is unsafe (see safe_hardlink_source() above)
1177 * - not CAP_FOWNER in a namespace with the inode owner uid mapped
1178 *
1179 * If the inode has been found through an idmapped mount the idmap of
1180 * the vfsmount must be passed through @idmap. This function will then take
1181 * care to map the inode according to @idmap before checking permissions.
1182 * On non-idmapped mounts or if permission checking is to be performed on the
1183 * raw inode simply pass @nop_mnt_idmap.
1184 *
1185 * Returns 0 if successful, -ve on error.
1186 */
1187int may_linkat(struct mnt_idmap *idmap, const struct path *link)
1188{
1189 struct inode *inode = link->dentry->d_inode;
1190
1191 /* Inode writeback is not safe when the uid or gid are invalid. */
1192 if (!vfsuid_valid(i_uid_into_vfsuid(idmap, inode)) ||
1193 !vfsgid_valid(i_gid_into_vfsgid(idmap, inode)))
1194 return -EOVERFLOW;
1195
1196 if (!sysctl_protected_hardlinks)
1197 return 0;
1198
1199 /* Source inode owner (or CAP_FOWNER) can hardlink all they like,
1200 * otherwise, it must be a safe source.
1201 */
1202 if (safe_hardlink_source(idmap, inode) ||
1203 inode_owner_or_capable(idmap, inode))
1204 return 0;
1205
1206 audit_log_path_denied(AUDIT_ANOM_LINK, "linkat");
1207 return -EPERM;
1208}
1209
1210/**
1211 * may_create_in_sticky - Check whether an O_CREAT open in a sticky directory
1212 * should be allowed, or not, on files that already
1213 * exist.
1214 * @idmap: idmap of the mount the inode was found from
1215 * @nd: nameidata pathwalk data
1216 * @inode: the inode of the file to open
1217 *
1218 * Block an O_CREAT open of a FIFO (or a regular file) when:
1219 * - sysctl_protected_fifos (or sysctl_protected_regular) is enabled
1220 * - the file already exists
1221 * - we are in a sticky directory
1222 * - we don't own the file
1223 * - the owner of the directory doesn't own the file
1224 * - the directory is world writable
1225 * If the sysctl_protected_fifos (or sysctl_protected_regular) is set to 2
1226 * the directory doesn't have to be world writable: being group writable will
1227 * be enough.
1228 *
1229 * If the inode has been found through an idmapped mount the idmap of
1230 * the vfsmount must be passed through @idmap. This function will then take
1231 * care to map the inode according to @idmap before checking permissions.
1232 * On non-idmapped mounts or if permission checking is to be performed on the
1233 * raw inode simply pass @nop_mnt_idmap.
1234 *
1235 * Returns 0 if the open is allowed, -ve on error.
1236 */
1237static int may_create_in_sticky(struct mnt_idmap *idmap,
1238 struct nameidata *nd, struct inode *const inode)
1239{
1240 umode_t dir_mode = nd->dir_mode;
1241 vfsuid_t dir_vfsuid = nd->dir_vfsuid;
1242
1243 if ((!sysctl_protected_fifos && S_ISFIFO(inode->i_mode)) ||
1244 (!sysctl_protected_regular && S_ISREG(inode->i_mode)) ||
1245 likely(!(dir_mode & S_ISVTX)) ||
1246 vfsuid_eq(i_uid_into_vfsuid(idmap, inode), dir_vfsuid) ||
1247 vfsuid_eq_kuid(i_uid_into_vfsuid(idmap, inode), current_fsuid()))
1248 return 0;
1249
1250 if (likely(dir_mode & 0002) ||
1251 (dir_mode & 0020 &&
1252 ((sysctl_protected_fifos >= 2 && S_ISFIFO(inode->i_mode)) ||
1253 (sysctl_protected_regular >= 2 && S_ISREG(inode->i_mode))))) {
1254 const char *operation = S_ISFIFO(inode->i_mode) ?
1255 "sticky_create_fifo" :
1256 "sticky_create_regular";
1257 audit_log_path_denied(AUDIT_ANOM_CREAT, operation);
1258 return -EACCES;
1259 }
1260 return 0;
1261}
1262
1263/*
1264 * follow_up - Find the mountpoint of path's vfsmount
1265 *
1266 * Given a path, find the mountpoint of its source file system.
1267 * Replace @path with the path of the mountpoint in the parent mount.
1268 * Up is towards /.
1269 *
1270 * Return 1 if we went up a level and 0 if we were already at the
1271 * root.
1272 */
1273int follow_up(struct path *path)
1274{
1275 struct mount *mnt = real_mount(path->mnt);
1276 struct mount *parent;
1277 struct dentry *mountpoint;
1278
1279 read_seqlock_excl(&mount_lock);
1280 parent = mnt->mnt_parent;
1281 if (parent == mnt) {
1282 read_sequnlock_excl(&mount_lock);
1283 return 0;
1284 }
1285 mntget(&parent->mnt);
1286 mountpoint = dget(mnt->mnt_mountpoint);
1287 read_sequnlock_excl(&mount_lock);
1288 dput(path->dentry);
1289 path->dentry = mountpoint;
1290 mntput(path->mnt);
1291 path->mnt = &parent->mnt;
1292 return 1;
1293}
1294EXPORT_SYMBOL(follow_up);
1295
1296static bool choose_mountpoint_rcu(struct mount *m, const struct path *root,
1297 struct path *path, unsigned *seqp)
1298{
1299 while (mnt_has_parent(m)) {
1300 struct dentry *mountpoint = m->mnt_mountpoint;
1301
1302 m = m->mnt_parent;
1303 if (unlikely(root->dentry == mountpoint &&
1304 root->mnt == &m->mnt))
1305 break;
1306 if (mountpoint != m->mnt.mnt_root) {
1307 path->mnt = &m->mnt;
1308 path->dentry = mountpoint;
1309 *seqp = read_seqcount_begin(&mountpoint->d_seq);
1310 return true;
1311 }
1312 }
1313 return false;
1314}
1315
1316static bool choose_mountpoint(struct mount *m, const struct path *root,
1317 struct path *path)
1318{
1319 bool found;
1320
1321 rcu_read_lock();
1322 while (1) {
1323 unsigned seq, mseq = read_seqbegin(&mount_lock);
1324
1325 found = choose_mountpoint_rcu(m, root, path, &seq);
1326 if (unlikely(!found)) {
1327 if (!read_seqretry(&mount_lock, mseq))
1328 break;
1329 } else {
1330 if (likely(__legitimize_path(path, seq, mseq)))
1331 break;
1332 rcu_read_unlock();
1333 path_put(path);
1334 rcu_read_lock();
1335 }
1336 }
1337 rcu_read_unlock();
1338 return found;
1339}
1340
1341/*
1342 * Perform an automount
1343 * - return -EISDIR to tell follow_managed() to stop and return the path we
1344 * were called with.
1345 */
1346static int follow_automount(struct path *path, int *count, unsigned lookup_flags)
1347{
1348 struct dentry *dentry = path->dentry;
1349
1350 /* We don't want to mount if someone's just doing a stat -
1351 * unless they're stat'ing a directory and appended a '/' to
1352 * the name.
1353 *
1354 * We do, however, want to mount if someone wants to open or
1355 * create a file of any type under the mountpoint, wants to
1356 * traverse through the mountpoint or wants to open the
1357 * mounted directory. Also, autofs may mark negative dentries
1358 * as being automount points. These will need the attentions
1359 * of the daemon to instantiate them before they can be used.
1360 */
1361 if (!(lookup_flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
1362 LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
1363 dentry->d_inode)
1364 return -EISDIR;
1365
1366 if (count && (*count)++ >= MAXSYMLINKS)
1367 return -ELOOP;
1368
1369 return finish_automount(dentry->d_op->d_automount(path), path);
1370}
1371
1372/*
1373 * mount traversal - out-of-line part. One note on ->d_flags accesses -
1374 * dentries are pinned but not locked here, so negative dentry can go
1375 * positive right under us. Use of smp_load_acquire() provides a barrier
1376 * sufficient for ->d_inode and ->d_flags consistency.
1377 */
1378static int __traverse_mounts(struct path *path, unsigned flags, bool *jumped,
1379 int *count, unsigned lookup_flags)
1380{
1381 struct vfsmount *mnt = path->mnt;
1382 bool need_mntput = false;
1383 int ret = 0;
1384
1385 while (flags & DCACHE_MANAGED_DENTRY) {
1386 /* Allow the filesystem to manage the transit without i_mutex
1387 * being held. */
1388 if (flags & DCACHE_MANAGE_TRANSIT) {
1389 ret = path->dentry->d_op->d_manage(path, false);
1390 flags = smp_load_acquire(&path->dentry->d_flags);
1391 if (ret < 0)
1392 break;
1393 }
1394
1395 if (flags & DCACHE_MOUNTED) { // something's mounted on it..
1396 struct vfsmount *mounted = lookup_mnt(path);
1397 if (mounted) { // ... in our namespace
1398 dput(path->dentry);
1399 if (need_mntput)
1400 mntput(path->mnt);
1401 path->mnt = mounted;
1402 path->dentry = dget(mounted->mnt_root);
1403 // here we know it's positive
1404 flags = path->dentry->d_flags;
1405 need_mntput = true;
1406 continue;
1407 }
1408 }
1409
1410 if (!(flags & DCACHE_NEED_AUTOMOUNT))
1411 break;
1412
1413 // uncovered automount point
1414 ret = follow_automount(path, count, lookup_flags);
1415 flags = smp_load_acquire(&path->dentry->d_flags);
1416 if (ret < 0)
1417 break;
1418 }
1419
1420 if (ret == -EISDIR)
1421 ret = 0;
1422 // possible if you race with several mount --move
1423 if (need_mntput && path->mnt == mnt)
1424 mntput(path->mnt);
1425 if (!ret && unlikely(d_flags_negative(flags)))
1426 ret = -ENOENT;
1427 *jumped = need_mntput;
1428 return ret;
1429}
1430
1431static inline int traverse_mounts(struct path *path, bool *jumped,
1432 int *count, unsigned lookup_flags)
1433{
1434 unsigned flags = smp_load_acquire(&path->dentry->d_flags);
1435
1436 /* fastpath */
1437 if (likely(!(flags & DCACHE_MANAGED_DENTRY))) {
1438 *jumped = false;
1439 if (unlikely(d_flags_negative(flags)))
1440 return -ENOENT;
1441 return 0;
1442 }
1443 return __traverse_mounts(path, flags, jumped, count, lookup_flags);
1444}
1445
1446int follow_down_one(struct path *path)
1447{
1448 struct vfsmount *mounted;
1449
1450 mounted = lookup_mnt(path);
1451 if (mounted) {
1452 dput(path->dentry);
1453 mntput(path->mnt);
1454 path->mnt = mounted;
1455 path->dentry = dget(mounted->mnt_root);
1456 return 1;
1457 }
1458 return 0;
1459}
1460EXPORT_SYMBOL(follow_down_one);
1461
1462/*
1463 * Follow down to the covering mount currently visible to userspace. At each
1464 * point, the filesystem owning that dentry may be queried as to whether the
1465 * caller is permitted to proceed or not.
1466 */
1467int follow_down(struct path *path, unsigned int flags)
1468{
1469 struct vfsmount *mnt = path->mnt;
1470 bool jumped;
1471 int ret = traverse_mounts(path, &jumped, NULL, flags);
1472
1473 if (path->mnt != mnt)
1474 mntput(mnt);
1475 return ret;
1476}
1477EXPORT_SYMBOL(follow_down);
1478
1479/*
1480 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
1481 * we meet a managed dentry that would need blocking.
1482 */
1483static bool __follow_mount_rcu(struct nameidata *nd, struct path *path)
1484{
1485 struct dentry *dentry = path->dentry;
1486 unsigned int flags = dentry->d_flags;
1487
1488 if (likely(!(flags & DCACHE_MANAGED_DENTRY)))
1489 return true;
1490
1491 if (unlikely(nd->flags & LOOKUP_NO_XDEV))
1492 return false;
1493
1494 for (;;) {
1495 /*
1496 * Don't forget we might have a non-mountpoint managed dentry
1497 * that wants to block transit.
1498 */
1499 if (unlikely(flags & DCACHE_MANAGE_TRANSIT)) {
1500 int res = dentry->d_op->d_manage(path, true);
1501 if (res)
1502 return res == -EISDIR;
1503 flags = dentry->d_flags;
1504 }
1505
1506 if (flags & DCACHE_MOUNTED) {
1507 struct mount *mounted = __lookup_mnt(path->mnt, dentry);
1508 if (mounted) {
1509 path->mnt = &mounted->mnt;
1510 dentry = path->dentry = mounted->mnt.mnt_root;
1511 nd->state |= ND_JUMPED;
1512 nd->next_seq = read_seqcount_begin(&dentry->d_seq);
1513 flags = dentry->d_flags;
1514 // makes sure that non-RCU pathwalk could reach
1515 // this state.
1516 if (read_seqretry(&mount_lock, nd->m_seq))
1517 return false;
1518 continue;
1519 }
1520 if (read_seqretry(&mount_lock, nd->m_seq))
1521 return false;
1522 }
1523 return !(flags & DCACHE_NEED_AUTOMOUNT);
1524 }
1525}
1526
1527static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry,
1528 struct path *path)
1529{
1530 bool jumped;
1531 int ret;
1532
1533 path->mnt = nd->path.mnt;
1534 path->dentry = dentry;
1535 if (nd->flags & LOOKUP_RCU) {
1536 unsigned int seq = nd->next_seq;
1537 if (likely(__follow_mount_rcu(nd, path)))
1538 return 0;
1539 // *path and nd->next_seq might've been clobbered
1540 path->mnt = nd->path.mnt;
1541 path->dentry = dentry;
1542 nd->next_seq = seq;
1543 if (!try_to_unlazy_next(nd, dentry))
1544 return -ECHILD;
1545 }
1546 ret = traverse_mounts(path, &jumped, &nd->total_link_count, nd->flags);
1547 if (jumped) {
1548 if (unlikely(nd->flags & LOOKUP_NO_XDEV))
1549 ret = -EXDEV;
1550 else
1551 nd->state |= ND_JUMPED;
1552 }
1553 if (unlikely(ret)) {
1554 dput(path->dentry);
1555 if (path->mnt != nd->path.mnt)
1556 mntput(path->mnt);
1557 }
1558 return ret;
1559}
1560
1561/*
1562 * This looks up the name in dcache and possibly revalidates the found dentry.
1563 * NULL is returned if the dentry does not exist in the cache.
1564 */
1565static struct dentry *lookup_dcache(const struct qstr *name,
1566 struct dentry *dir,
1567 unsigned int flags)
1568{
1569 struct dentry *dentry = d_lookup(dir, name);
1570 if (dentry) {
1571 int error = d_revalidate(dentry, flags);
1572 if (unlikely(error <= 0)) {
1573 if (!error)
1574 d_invalidate(dentry);
1575 dput(dentry);
1576 return ERR_PTR(error);
1577 }
1578 }
1579 return dentry;
1580}
1581
1582/*
1583 * Parent directory has inode locked exclusive. This is one
1584 * and only case when ->lookup() gets called on non in-lookup
1585 * dentries - as the matter of fact, this only gets called
1586 * when directory is guaranteed to have no in-lookup children
1587 * at all.
1588 */
1589struct dentry *lookup_one_qstr_excl(const struct qstr *name,
1590 struct dentry *base,
1591 unsigned int flags)
1592{
1593 struct dentry *dentry = lookup_dcache(name, base, flags);
1594 struct dentry *old;
1595 struct inode *dir = base->d_inode;
1596
1597 if (dentry)
1598 return dentry;
1599
1600 /* Don't create child dentry for a dead directory. */
1601 if (unlikely(IS_DEADDIR(dir)))
1602 return ERR_PTR(-ENOENT);
1603
1604 dentry = d_alloc(base, name);
1605 if (unlikely(!dentry))
1606 return ERR_PTR(-ENOMEM);
1607
1608 old = dir->i_op->lookup(dir, dentry, flags);
1609 if (unlikely(old)) {
1610 dput(dentry);
1611 dentry = old;
1612 }
1613 return dentry;
1614}
1615EXPORT_SYMBOL(lookup_one_qstr_excl);
1616
1617static struct dentry *lookup_fast(struct nameidata *nd)
1618{
1619 struct dentry *dentry, *parent = nd->path.dentry;
1620 int status = 1;
1621
1622 /*
1623 * Rename seqlock is not required here because in the off chance
1624 * of a false negative due to a concurrent rename, the caller is
1625 * going to fall back to non-racy lookup.
1626 */
1627 if (nd->flags & LOOKUP_RCU) {
1628 dentry = __d_lookup_rcu(parent, &nd->last, &nd->next_seq);
1629 if (unlikely(!dentry)) {
1630 if (!try_to_unlazy(nd))
1631 return ERR_PTR(-ECHILD);
1632 return NULL;
1633 }
1634
1635 /*
1636 * This sequence count validates that the parent had no
1637 * changes while we did the lookup of the dentry above.
1638 */
1639 if (read_seqcount_retry(&parent->d_seq, nd->seq))
1640 return ERR_PTR(-ECHILD);
1641
1642 status = d_revalidate(dentry, nd->flags);
1643 if (likely(status > 0))
1644 return dentry;
1645 if (!try_to_unlazy_next(nd, dentry))
1646 return ERR_PTR(-ECHILD);
1647 if (status == -ECHILD)
1648 /* we'd been told to redo it in non-rcu mode */
1649 status = d_revalidate(dentry, nd->flags);
1650 } else {
1651 dentry = __d_lookup(parent, &nd->last);
1652 if (unlikely(!dentry))
1653 return NULL;
1654 status = d_revalidate(dentry, nd->flags);
1655 }
1656 if (unlikely(status <= 0)) {
1657 if (!status)
1658 d_invalidate(dentry);
1659 dput(dentry);
1660 return ERR_PTR(status);
1661 }
1662 return dentry;
1663}
1664
1665/* Fast lookup failed, do it the slow way */
1666static struct dentry *__lookup_slow(const struct qstr *name,
1667 struct dentry *dir,
1668 unsigned int flags)
1669{
1670 struct dentry *dentry, *old;
1671 struct inode *inode = dir->d_inode;
1672 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
1673
1674 /* Don't go there if it's already dead */
1675 if (unlikely(IS_DEADDIR(inode)))
1676 return ERR_PTR(-ENOENT);
1677again:
1678 dentry = d_alloc_parallel(dir, name, &wq);
1679 if (IS_ERR(dentry))
1680 return dentry;
1681 if (unlikely(!d_in_lookup(dentry))) {
1682 int error = d_revalidate(dentry, flags);
1683 if (unlikely(error <= 0)) {
1684 if (!error) {
1685 d_invalidate(dentry);
1686 dput(dentry);
1687 goto again;
1688 }
1689 dput(dentry);
1690 dentry = ERR_PTR(error);
1691 }
1692 } else {
1693 old = inode->i_op->lookup(inode, dentry, flags);
1694 d_lookup_done(dentry);
1695 if (unlikely(old)) {
1696 dput(dentry);
1697 dentry = old;
1698 }
1699 }
1700 return dentry;
1701}
1702
1703static struct dentry *lookup_slow(const struct qstr *name,
1704 struct dentry *dir,
1705 unsigned int flags)
1706{
1707 struct inode *inode = dir->d_inode;
1708 struct dentry *res;
1709 inode_lock_shared(inode);
1710 res = __lookup_slow(name, dir, flags);
1711 inode_unlock_shared(inode);
1712 return res;
1713}
1714
1715static inline int may_lookup(struct mnt_idmap *idmap,
1716 struct nameidata *nd)
1717{
1718 if (nd->flags & LOOKUP_RCU) {
1719 int err = inode_permission(idmap, nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
1720 if (!err) // success, keep going
1721 return 0;
1722 if (!try_to_unlazy(nd))
1723 return -ECHILD; // redo it all non-lazy
1724 if (err != -ECHILD) // hard error
1725 return err;
1726 }
1727 return inode_permission(idmap, nd->inode, MAY_EXEC);
1728}
1729
1730static int reserve_stack(struct nameidata *nd, struct path *link)
1731{
1732 if (unlikely(nd->total_link_count++ >= MAXSYMLINKS))
1733 return -ELOOP;
1734
1735 if (likely(nd->depth != EMBEDDED_LEVELS))
1736 return 0;
1737 if (likely(nd->stack != nd->internal))
1738 return 0;
1739 if (likely(nd_alloc_stack(nd)))
1740 return 0;
1741
1742 if (nd->flags & LOOKUP_RCU) {
1743 // we need to grab link before we do unlazy. And we can't skip
1744 // unlazy even if we fail to grab the link - cleanup needs it
1745 bool grabbed_link = legitimize_path(nd, link, nd->next_seq);
1746
1747 if (!try_to_unlazy(nd) || !grabbed_link)
1748 return -ECHILD;
1749
1750 if (nd_alloc_stack(nd))
1751 return 0;
1752 }
1753 return -ENOMEM;
1754}
1755
1756enum {WALK_TRAILING = 1, WALK_MORE = 2, WALK_NOFOLLOW = 4};
1757
1758static const char *pick_link(struct nameidata *nd, struct path *link,
1759 struct inode *inode, int flags)
1760{
1761 struct saved *last;
1762 const char *res;
1763 int error = reserve_stack(nd, link);
1764
1765 if (unlikely(error)) {
1766 if (!(nd->flags & LOOKUP_RCU))
1767 path_put(link);
1768 return ERR_PTR(error);
1769 }
1770 last = nd->stack + nd->depth++;
1771 last->link = *link;
1772 clear_delayed_call(&last->done);
1773 last->seq = nd->next_seq;
1774
1775 if (flags & WALK_TRAILING) {
1776 error = may_follow_link(nd, inode);
1777 if (unlikely(error))
1778 return ERR_PTR(error);
1779 }
1780
1781 if (unlikely(nd->flags & LOOKUP_NO_SYMLINKS) ||
1782 unlikely(link->mnt->mnt_flags & MNT_NOSYMFOLLOW))
1783 return ERR_PTR(-ELOOP);
1784
1785 if (!(nd->flags & LOOKUP_RCU)) {
1786 touch_atime(&last->link);
1787 cond_resched();
1788 } else if (atime_needs_update(&last->link, inode)) {
1789 if (!try_to_unlazy(nd))
1790 return ERR_PTR(-ECHILD);
1791 touch_atime(&last->link);
1792 }
1793
1794 error = security_inode_follow_link(link->dentry, inode,
1795 nd->flags & LOOKUP_RCU);
1796 if (unlikely(error))
1797 return ERR_PTR(error);
1798
1799 res = READ_ONCE(inode->i_link);
1800 if (!res) {
1801 const char * (*get)(struct dentry *, struct inode *,
1802 struct delayed_call *);
1803 get = inode->i_op->get_link;
1804 if (nd->flags & LOOKUP_RCU) {
1805 res = get(NULL, inode, &last->done);
1806 if (res == ERR_PTR(-ECHILD) && try_to_unlazy(nd))
1807 res = get(link->dentry, inode, &last->done);
1808 } else {
1809 res = get(link->dentry, inode, &last->done);
1810 }
1811 if (!res)
1812 goto all_done;
1813 if (IS_ERR(res))
1814 return res;
1815 }
1816 if (*res == '/') {
1817 error = nd_jump_root(nd);
1818 if (unlikely(error))
1819 return ERR_PTR(error);
1820 while (unlikely(*++res == '/'))
1821 ;
1822 }
1823 if (*res)
1824 return res;
1825all_done: // pure jump
1826 put_link(nd);
1827 return NULL;
1828}
1829
1830/*
1831 * Do we need to follow links? We _really_ want to be able
1832 * to do this check without having to look at inode->i_op,
1833 * so we keep a cache of "no, this doesn't need follow_link"
1834 * for the common case.
1835 *
1836 * NOTE: dentry must be what nd->next_seq had been sampled from.
1837 */
1838static const char *step_into(struct nameidata *nd, int flags,
1839 struct dentry *dentry)
1840{
1841 struct path path;
1842 struct inode *inode;
1843 int err = handle_mounts(nd, dentry, &path);
1844
1845 if (err < 0)
1846 return ERR_PTR(err);
1847 inode = path.dentry->d_inode;
1848 if (likely(!d_is_symlink(path.dentry)) ||
1849 ((flags & WALK_TRAILING) && !(nd->flags & LOOKUP_FOLLOW)) ||
1850 (flags & WALK_NOFOLLOW)) {
1851 /* not a symlink or should not follow */
1852 if (nd->flags & LOOKUP_RCU) {
1853 if (read_seqcount_retry(&path.dentry->d_seq, nd->next_seq))
1854 return ERR_PTR(-ECHILD);
1855 if (unlikely(!inode))
1856 return ERR_PTR(-ENOENT);
1857 } else {
1858 dput(nd->path.dentry);
1859 if (nd->path.mnt != path.mnt)
1860 mntput(nd->path.mnt);
1861 }
1862 nd->path = path;
1863 nd->inode = inode;
1864 nd->seq = nd->next_seq;
1865 return NULL;
1866 }
1867 if (nd->flags & LOOKUP_RCU) {
1868 /* make sure that d_is_symlink above matches inode */
1869 if (read_seqcount_retry(&path.dentry->d_seq, nd->next_seq))
1870 return ERR_PTR(-ECHILD);
1871 } else {
1872 if (path.mnt == nd->path.mnt)
1873 mntget(path.mnt);
1874 }
1875 return pick_link(nd, &path, inode, flags);
1876}
1877
1878static struct dentry *follow_dotdot_rcu(struct nameidata *nd)
1879{
1880 struct dentry *parent, *old;
1881
1882 if (path_equal(&nd->path, &nd->root))
1883 goto in_root;
1884 if (unlikely(nd->path.dentry == nd->path.mnt->mnt_root)) {
1885 struct path path;
1886 unsigned seq;
1887 if (!choose_mountpoint_rcu(real_mount(nd->path.mnt),
1888 &nd->root, &path, &seq))
1889 goto in_root;
1890 if (unlikely(nd->flags & LOOKUP_NO_XDEV))
1891 return ERR_PTR(-ECHILD);
1892 nd->path = path;
1893 nd->inode = path.dentry->d_inode;
1894 nd->seq = seq;
1895 // makes sure that non-RCU pathwalk could reach this state
1896 if (read_seqretry(&mount_lock, nd->m_seq))
1897 return ERR_PTR(-ECHILD);
1898 /* we know that mountpoint was pinned */
1899 }
1900 old = nd->path.dentry;
1901 parent = old->d_parent;
1902 nd->next_seq = read_seqcount_begin(&parent->d_seq);
1903 // makes sure that non-RCU pathwalk could reach this state
1904 if (read_seqcount_retry(&old->d_seq, nd->seq))
1905 return ERR_PTR(-ECHILD);
1906 if (unlikely(!path_connected(nd->path.mnt, parent)))
1907 return ERR_PTR(-ECHILD);
1908 return parent;
1909in_root:
1910 if (read_seqretry(&mount_lock, nd->m_seq))
1911 return ERR_PTR(-ECHILD);
1912 if (unlikely(nd->flags & LOOKUP_BENEATH))
1913 return ERR_PTR(-ECHILD);
1914 nd->next_seq = nd->seq;
1915 return nd->path.dentry;
1916}
1917
1918static struct dentry *follow_dotdot(struct nameidata *nd)
1919{
1920 struct dentry *parent;
1921
1922 if (path_equal(&nd->path, &nd->root))
1923 goto in_root;
1924 if (unlikely(nd->path.dentry == nd->path.mnt->mnt_root)) {
1925 struct path path;
1926
1927 if (!choose_mountpoint(real_mount(nd->path.mnt),
1928 &nd->root, &path))
1929 goto in_root;
1930 path_put(&nd->path);
1931 nd->path = path;
1932 nd->inode = path.dentry->d_inode;
1933 if (unlikely(nd->flags & LOOKUP_NO_XDEV))
1934 return ERR_PTR(-EXDEV);
1935 }
1936 /* rare case of legitimate dget_parent()... */
1937 parent = dget_parent(nd->path.dentry);
1938 if (unlikely(!path_connected(nd->path.mnt, parent))) {
1939 dput(parent);
1940 return ERR_PTR(-ENOENT);
1941 }
1942 return parent;
1943
1944in_root:
1945 if (unlikely(nd->flags & LOOKUP_BENEATH))
1946 return ERR_PTR(-EXDEV);
1947 return dget(nd->path.dentry);
1948}
1949
1950static const char *handle_dots(struct nameidata *nd, int type)
1951{
1952 if (type == LAST_DOTDOT) {
1953 const char *error = NULL;
1954 struct dentry *parent;
1955
1956 if (!nd->root.mnt) {
1957 error = ERR_PTR(set_root(nd));
1958 if (error)
1959 return error;
1960 }
1961 if (nd->flags & LOOKUP_RCU)
1962 parent = follow_dotdot_rcu(nd);
1963 else
1964 parent = follow_dotdot(nd);
1965 if (IS_ERR(parent))
1966 return ERR_CAST(parent);
1967 error = step_into(nd, WALK_NOFOLLOW, parent);
1968 if (unlikely(error))
1969 return error;
1970
1971 if (unlikely(nd->flags & LOOKUP_IS_SCOPED)) {
1972 /*
1973 * If there was a racing rename or mount along our
1974 * path, then we can't be sure that ".." hasn't jumped
1975 * above nd->root (and so userspace should retry or use
1976 * some fallback).
1977 */
1978 smp_rmb();
1979 if (__read_seqcount_retry(&mount_lock.seqcount, nd->m_seq))
1980 return ERR_PTR(-EAGAIN);
1981 if (__read_seqcount_retry(&rename_lock.seqcount, nd->r_seq))
1982 return ERR_PTR(-EAGAIN);
1983 }
1984 }
1985 return NULL;
1986}
1987
1988static const char *walk_component(struct nameidata *nd, int flags)
1989{
1990 struct dentry *dentry;
1991 /*
1992 * "." and ".." are special - ".." especially so because it has
1993 * to be able to know about the current root directory and
1994 * parent relationships.
1995 */
1996 if (unlikely(nd->last_type != LAST_NORM)) {
1997 if (!(flags & WALK_MORE) && nd->depth)
1998 put_link(nd);
1999 return handle_dots(nd, nd->last_type);
2000 }
2001 dentry = lookup_fast(nd);
2002 if (IS_ERR(dentry))
2003 return ERR_CAST(dentry);
2004 if (unlikely(!dentry)) {
2005 dentry = lookup_slow(&nd->last, nd->path.dentry, nd->flags);
2006 if (IS_ERR(dentry))
2007 return ERR_CAST(dentry);
2008 }
2009 if (!(flags & WALK_MORE) && nd->depth)
2010 put_link(nd);
2011 return step_into(nd, flags, dentry);
2012}
2013
2014/*
2015 * We can do the critical dentry name comparison and hashing
2016 * operations one word at a time, but we are limited to:
2017 *
2018 * - Architectures with fast unaligned word accesses. We could
2019 * do a "get_unaligned()" if this helps and is sufficiently
2020 * fast.
2021 *
2022 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
2023 * do not trap on the (extremely unlikely) case of a page
2024 * crossing operation.
2025 *
2026 * - Furthermore, we need an efficient 64-bit compile for the
2027 * 64-bit case in order to generate the "number of bytes in
2028 * the final mask". Again, that could be replaced with a
2029 * efficient population count instruction or similar.
2030 */
2031#ifdef CONFIG_DCACHE_WORD_ACCESS
2032
2033#include <asm/word-at-a-time.h>
2034
2035#ifdef HASH_MIX
2036
2037/* Architecture provides HASH_MIX and fold_hash() in <asm/hash.h> */
2038
2039#elif defined(CONFIG_64BIT)
2040/*
2041 * Register pressure in the mixing function is an issue, particularly
2042 * on 32-bit x86, but almost any function requires one state value and
2043 * one temporary. Instead, use a function designed for two state values
2044 * and no temporaries.
2045 *
2046 * This function cannot create a collision in only two iterations, so
2047 * we have two iterations to achieve avalanche. In those two iterations,
2048 * we have six layers of mixing, which is enough to spread one bit's
2049 * influence out to 2^6 = 64 state bits.
2050 *
2051 * Rotate constants are scored by considering either 64 one-bit input
2052 * deltas or 64*63/2 = 2016 two-bit input deltas, and finding the
2053 * probability of that delta causing a change to each of the 128 output
2054 * bits, using a sample of random initial states.
2055 *
2056 * The Shannon entropy of the computed probabilities is then summed
2057 * to produce a score. Ideally, any input change has a 50% chance of
2058 * toggling any given output bit.
2059 *
2060 * Mixing scores (in bits) for (12,45):
2061 * Input delta: 1-bit 2-bit
2062 * 1 round: 713.3 42542.6
2063 * 2 rounds: 2753.7 140389.8
2064 * 3 rounds: 5954.1 233458.2
2065 * 4 rounds: 7862.6 256672.2
2066 * Perfect: 8192 258048
2067 * (64*128) (64*63/2 * 128)
2068 */
2069#define HASH_MIX(x, y, a) \
2070 ( x ^= (a), \
2071 y ^= x, x = rol64(x,12),\
2072 x += y, y = rol64(y,45),\
2073 y *= 9 )
2074
2075/*
2076 * Fold two longs into one 32-bit hash value. This must be fast, but
2077 * latency isn't quite as critical, as there is a fair bit of additional
2078 * work done before the hash value is used.
2079 */
2080static inline unsigned int fold_hash(unsigned long x, unsigned long y)
2081{
2082 y ^= x * GOLDEN_RATIO_64;
2083 y *= GOLDEN_RATIO_64;
2084 return y >> 32;
2085}
2086
2087#else /* 32-bit case */
2088
2089/*
2090 * Mixing scores (in bits) for (7,20):
2091 * Input delta: 1-bit 2-bit
2092 * 1 round: 330.3 9201.6
2093 * 2 rounds: 1246.4 25475.4
2094 * 3 rounds: 1907.1 31295.1
2095 * 4 rounds: 2042.3 31718.6
2096 * Perfect: 2048 31744
2097 * (32*64) (32*31/2 * 64)
2098 */
2099#define HASH_MIX(x, y, a) \
2100 ( x ^= (a), \
2101 y ^= x, x = rol32(x, 7),\
2102 x += y, y = rol32(y,20),\
2103 y *= 9 )
2104
2105static inline unsigned int fold_hash(unsigned long x, unsigned long y)
2106{
2107 /* Use arch-optimized multiply if one exists */
2108 return __hash_32(y ^ __hash_32(x));
2109}
2110
2111#endif
2112
2113/*
2114 * Return the hash of a string of known length. This is carfully
2115 * designed to match hash_name(), which is the more critical function.
2116 * In particular, we must end by hashing a final word containing 0..7
2117 * payload bytes, to match the way that hash_name() iterates until it
2118 * finds the delimiter after the name.
2119 */
2120unsigned int full_name_hash(const void *salt, const char *name, unsigned int len)
2121{
2122 unsigned long a, x = 0, y = (unsigned long)salt;
2123
2124 for (;;) {
2125 if (!len)
2126 goto done;
2127 a = load_unaligned_zeropad(name);
2128 if (len < sizeof(unsigned long))
2129 break;
2130 HASH_MIX(x, y, a);
2131 name += sizeof(unsigned long);
2132 len -= sizeof(unsigned long);
2133 }
2134 x ^= a & bytemask_from_count(len);
2135done:
2136 return fold_hash(x, y);
2137}
2138EXPORT_SYMBOL(full_name_hash);
2139
2140/* Return the "hash_len" (hash and length) of a null-terminated string */
2141u64 hashlen_string(const void *salt, const char *name)
2142{
2143 unsigned long a = 0, x = 0, y = (unsigned long)salt;
2144 unsigned long adata, mask, len;
2145 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
2146
2147 len = 0;
2148 goto inside;
2149
2150 do {
2151 HASH_MIX(x, y, a);
2152 len += sizeof(unsigned long);
2153inside:
2154 a = load_unaligned_zeropad(name+len);
2155 } while (!has_zero(a, &adata, &constants));
2156
2157 adata = prep_zero_mask(a, adata, &constants);
2158 mask = create_zero_mask(adata);
2159 x ^= a & zero_bytemask(mask);
2160
2161 return hashlen_create(fold_hash(x, y), len + find_zero(mask));
2162}
2163EXPORT_SYMBOL(hashlen_string);
2164
2165/*
2166 * Calculate the length and hash of the path component, and
2167 * return the "hash_len" as the result.
2168 */
2169static inline u64 hash_name(const void *salt, const char *name)
2170{
2171 unsigned long a = 0, b, x = 0, y = (unsigned long)salt;
2172 unsigned long adata, bdata, mask, len;
2173 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
2174
2175 len = 0;
2176 goto inside;
2177
2178 do {
2179 HASH_MIX(x, y, a);
2180 len += sizeof(unsigned long);
2181inside:
2182 a = load_unaligned_zeropad(name+len);
2183 b = a ^ REPEAT_BYTE('/');
2184 } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants)));
2185
2186 adata = prep_zero_mask(a, adata, &constants);
2187 bdata = prep_zero_mask(b, bdata, &constants);
2188 mask = create_zero_mask(adata | bdata);
2189 x ^= a & zero_bytemask(mask);
2190
2191 return hashlen_create(fold_hash(x, y), len + find_zero(mask));
2192}
2193
2194#else /* !CONFIG_DCACHE_WORD_ACCESS: Slow, byte-at-a-time version */
2195
2196/* Return the hash of a string of known length */
2197unsigned int full_name_hash(const void *salt, const char *name, unsigned int len)
2198{
2199 unsigned long hash = init_name_hash(salt);
2200 while (len--)
2201 hash = partial_name_hash((unsigned char)*name++, hash);
2202 return end_name_hash(hash);
2203}
2204EXPORT_SYMBOL(full_name_hash);
2205
2206/* Return the "hash_len" (hash and length) of a null-terminated string */
2207u64 hashlen_string(const void *salt, const char *name)
2208{
2209 unsigned long hash = init_name_hash(salt);
2210 unsigned long len = 0, c;
2211
2212 c = (unsigned char)*name;
2213 while (c) {
2214 len++;
2215 hash = partial_name_hash(c, hash);
2216 c = (unsigned char)name[len];
2217 }
2218 return hashlen_create(end_name_hash(hash), len);
2219}
2220EXPORT_SYMBOL(hashlen_string);
2221
2222/*
2223 * We know there's a real path component here of at least
2224 * one character.
2225 */
2226static inline u64 hash_name(const void *salt, const char *name)
2227{
2228 unsigned long hash = init_name_hash(salt);
2229 unsigned long len = 0, c;
2230
2231 c = (unsigned char)*name;
2232 do {
2233 len++;
2234 hash = partial_name_hash(c, hash);
2235 c = (unsigned char)name[len];
2236 } while (c && c != '/');
2237 return hashlen_create(end_name_hash(hash), len);
2238}
2239
2240#endif
2241
2242/*
2243 * Name resolution.
2244 * This is the basic name resolution function, turning a pathname into
2245 * the final dentry. We expect 'base' to be positive and a directory.
2246 *
2247 * Returns 0 and nd will have valid dentry and mnt on success.
2248 * Returns error and drops reference to input namei data on failure.
2249 */
2250static int link_path_walk(const char *name, struct nameidata *nd)
2251{
2252 int depth = 0; // depth <= nd->depth
2253 int err;
2254
2255 nd->last_type = LAST_ROOT;
2256 nd->flags |= LOOKUP_PARENT;
2257 if (IS_ERR(name))
2258 return PTR_ERR(name);
2259 while (*name=='/')
2260 name++;
2261 if (!*name) {
2262 nd->dir_mode = 0; // short-circuit the 'hardening' idiocy
2263 return 0;
2264 }
2265
2266 /* At this point we know we have a real path component. */
2267 for(;;) {
2268 struct mnt_idmap *idmap;
2269 const char *link;
2270 u64 hash_len;
2271 int type;
2272
2273 idmap = mnt_idmap(nd->path.mnt);
2274 err = may_lookup(idmap, nd);
2275 if (err)
2276 return err;
2277
2278 hash_len = hash_name(nd->path.dentry, name);
2279
2280 type = LAST_NORM;
2281 if (name[0] == '.') switch (hashlen_len(hash_len)) {
2282 case 2:
2283 if (name[1] == '.') {
2284 type = LAST_DOTDOT;
2285 nd->state |= ND_JUMPED;
2286 }
2287 break;
2288 case 1:
2289 type = LAST_DOT;
2290 }
2291 if (likely(type == LAST_NORM)) {
2292 struct dentry *parent = nd->path.dentry;
2293 nd->state &= ~ND_JUMPED;
2294 if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
2295 struct qstr this = { { .hash_len = hash_len }, .name = name };
2296 err = parent->d_op->d_hash(parent, &this);
2297 if (err < 0)
2298 return err;
2299 hash_len = this.hash_len;
2300 name = this.name;
2301 }
2302 }
2303
2304 nd->last.hash_len = hash_len;
2305 nd->last.name = name;
2306 nd->last_type = type;
2307
2308 name += hashlen_len(hash_len);
2309 if (!*name)
2310 goto OK;
2311 /*
2312 * If it wasn't NUL, we know it was '/'. Skip that
2313 * slash, and continue until no more slashes.
2314 */
2315 do {
2316 name++;
2317 } while (unlikely(*name == '/'));
2318 if (unlikely(!*name)) {
2319OK:
2320 /* pathname or trailing symlink, done */
2321 if (!depth) {
2322 nd->dir_vfsuid = i_uid_into_vfsuid(idmap, nd->inode);
2323 nd->dir_mode = nd->inode->i_mode;
2324 nd->flags &= ~LOOKUP_PARENT;
2325 return 0;
2326 }
2327 /* last component of nested symlink */
2328 name = nd->stack[--depth].name;
2329 link = walk_component(nd, 0);
2330 } else {
2331 /* not the last component */
2332 link = walk_component(nd, WALK_MORE);
2333 }
2334 if (unlikely(link)) {
2335 if (IS_ERR(link))
2336 return PTR_ERR(link);
2337 /* a symlink to follow */
2338 nd->stack[depth++].name = name;
2339 name = link;
2340 continue;
2341 }
2342 if (unlikely(!d_can_lookup(nd->path.dentry))) {
2343 if (nd->flags & LOOKUP_RCU) {
2344 if (!try_to_unlazy(nd))
2345 return -ECHILD;
2346 }
2347 return -ENOTDIR;
2348 }
2349 }
2350}
2351
2352/* must be paired with terminate_walk() */
2353static const char *path_init(struct nameidata *nd, unsigned flags)
2354{
2355 int error;
2356 const char *s = nd->name->name;
2357
2358 /* LOOKUP_CACHED requires RCU, ask caller to retry */
2359 if ((flags & (LOOKUP_RCU | LOOKUP_CACHED)) == LOOKUP_CACHED)
2360 return ERR_PTR(-EAGAIN);
2361
2362 if (!*s)
2363 flags &= ~LOOKUP_RCU;
2364 if (flags & LOOKUP_RCU)
2365 rcu_read_lock();
2366 else
2367 nd->seq = nd->next_seq = 0;
2368
2369 nd->flags = flags;
2370 nd->state |= ND_JUMPED;
2371
2372 nd->m_seq = __read_seqcount_begin(&mount_lock.seqcount);
2373 nd->r_seq = __read_seqcount_begin(&rename_lock.seqcount);
2374 smp_rmb();
2375
2376 if (nd->state & ND_ROOT_PRESET) {
2377 struct dentry *root = nd->root.dentry;
2378 struct inode *inode = root->d_inode;
2379 if (*s && unlikely(!d_can_lookup(root)))
2380 return ERR_PTR(-ENOTDIR);
2381 nd->path = nd->root;
2382 nd->inode = inode;
2383 if (flags & LOOKUP_RCU) {
2384 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
2385 nd->root_seq = nd->seq;
2386 } else {
2387 path_get(&nd->path);
2388 }
2389 return s;
2390 }
2391
2392 nd->root.mnt = NULL;
2393
2394 /* Absolute pathname -- fetch the root (LOOKUP_IN_ROOT uses nd->dfd). */
2395 if (*s == '/' && !(flags & LOOKUP_IN_ROOT)) {
2396 error = nd_jump_root(nd);
2397 if (unlikely(error))
2398 return ERR_PTR(error);
2399 return s;
2400 }
2401
2402 /* Relative pathname -- get the starting-point it is relative to. */
2403 if (nd->dfd == AT_FDCWD) {
2404 if (flags & LOOKUP_RCU) {
2405 struct fs_struct *fs = current->fs;
2406 unsigned seq;
2407
2408 do {
2409 seq = read_seqcount_begin(&fs->seq);
2410 nd->path = fs->pwd;
2411 nd->inode = nd->path.dentry->d_inode;
2412 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
2413 } while (read_seqcount_retry(&fs->seq, seq));
2414 } else {
2415 get_fs_pwd(current->fs, &nd->path);
2416 nd->inode = nd->path.dentry->d_inode;
2417 }
2418 } else {
2419 /* Caller must check execute permissions on the starting path component */
2420 struct fd f = fdget_raw(nd->dfd);
2421 struct dentry *dentry;
2422
2423 if (!f.file)
2424 return ERR_PTR(-EBADF);
2425
2426 dentry = f.file->f_path.dentry;
2427
2428 if (*s && unlikely(!d_can_lookup(dentry))) {
2429 fdput(f);
2430 return ERR_PTR(-ENOTDIR);
2431 }
2432
2433 nd->path = f.file->f_path;
2434 if (flags & LOOKUP_RCU) {
2435 nd->inode = nd->path.dentry->d_inode;
2436 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
2437 } else {
2438 path_get(&nd->path);
2439 nd->inode = nd->path.dentry->d_inode;
2440 }
2441 fdput(f);
2442 }
2443
2444 /* For scoped-lookups we need to set the root to the dirfd as well. */
2445 if (flags & LOOKUP_IS_SCOPED) {
2446 nd->root = nd->path;
2447 if (flags & LOOKUP_RCU) {
2448 nd->root_seq = nd->seq;
2449 } else {
2450 path_get(&nd->root);
2451 nd->state |= ND_ROOT_GRABBED;
2452 }
2453 }
2454 return s;
2455}
2456
2457static inline const char *lookup_last(struct nameidata *nd)
2458{
2459 if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
2460 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
2461
2462 return walk_component(nd, WALK_TRAILING);
2463}
2464
2465static int handle_lookup_down(struct nameidata *nd)
2466{
2467 if (!(nd->flags & LOOKUP_RCU))
2468 dget(nd->path.dentry);
2469 nd->next_seq = nd->seq;
2470 return PTR_ERR(step_into(nd, WALK_NOFOLLOW, nd->path.dentry));
2471}
2472
2473/* Returns 0 and nd will be valid on success; Returns error, otherwise. */
2474static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path)
2475{
2476 const char *s = path_init(nd, flags);
2477 int err;
2478
2479 if (unlikely(flags & LOOKUP_DOWN) && !IS_ERR(s)) {
2480 err = handle_lookup_down(nd);
2481 if (unlikely(err < 0))
2482 s = ERR_PTR(err);
2483 }
2484
2485 while (!(err = link_path_walk(s, nd)) &&
2486 (s = lookup_last(nd)) != NULL)
2487 ;
2488 if (!err && unlikely(nd->flags & LOOKUP_MOUNTPOINT)) {
2489 err = handle_lookup_down(nd);
2490 nd->state &= ~ND_JUMPED; // no d_weak_revalidate(), please...
2491 }
2492 if (!err)
2493 err = complete_walk(nd);
2494
2495 if (!err && nd->flags & LOOKUP_DIRECTORY)
2496 if (!d_can_lookup(nd->path.dentry))
2497 err = -ENOTDIR;
2498 if (!err) {
2499 *path = nd->path;
2500 nd->path.mnt = NULL;
2501 nd->path.dentry = NULL;
2502 }
2503 terminate_walk(nd);
2504 return err;
2505}
2506
2507int filename_lookup(int dfd, struct filename *name, unsigned flags,
2508 struct path *path, struct path *root)
2509{
2510 int retval;
2511 struct nameidata nd;
2512 if (IS_ERR(name))
2513 return PTR_ERR(name);
2514 set_nameidata(&nd, dfd, name, root);
2515 retval = path_lookupat(&nd, flags | LOOKUP_RCU, path);
2516 if (unlikely(retval == -ECHILD))
2517 retval = path_lookupat(&nd, flags, path);
2518 if (unlikely(retval == -ESTALE))
2519 retval = path_lookupat(&nd, flags | LOOKUP_REVAL, path);
2520
2521 if (likely(!retval))
2522 audit_inode(name, path->dentry,
2523 flags & LOOKUP_MOUNTPOINT ? AUDIT_INODE_NOEVAL : 0);
2524 restore_nameidata();
2525 return retval;
2526}
2527
2528/* Returns 0 and nd will be valid on success; Returns error, otherwise. */
2529static int path_parentat(struct nameidata *nd, unsigned flags,
2530 struct path *parent)
2531{
2532 const char *s = path_init(nd, flags);
2533 int err = link_path_walk(s, nd);
2534 if (!err)
2535 err = complete_walk(nd);
2536 if (!err) {
2537 *parent = nd->path;
2538 nd->path.mnt = NULL;
2539 nd->path.dentry = NULL;
2540 }
2541 terminate_walk(nd);
2542 return err;
2543}
2544
2545/* Note: this does not consume "name" */
2546static int __filename_parentat(int dfd, struct filename *name,
2547 unsigned int flags, struct path *parent,
2548 struct qstr *last, int *type,
2549 const struct path *root)
2550{
2551 int retval;
2552 struct nameidata nd;
2553
2554 if (IS_ERR(name))
2555 return PTR_ERR(name);
2556 set_nameidata(&nd, dfd, name, root);
2557 retval = path_parentat(&nd, flags | LOOKUP_RCU, parent);
2558 if (unlikely(retval == -ECHILD))
2559 retval = path_parentat(&nd, flags, parent);
2560 if (unlikely(retval == -ESTALE))
2561 retval = path_parentat(&nd, flags | LOOKUP_REVAL, parent);
2562 if (likely(!retval)) {
2563 *last = nd.last;
2564 *type = nd.last_type;
2565 audit_inode(name, parent->dentry, AUDIT_INODE_PARENT);
2566 }
2567 restore_nameidata();
2568 return retval;
2569}
2570
2571static int filename_parentat(int dfd, struct filename *name,
2572 unsigned int flags, struct path *parent,
2573 struct qstr *last, int *type)
2574{
2575 return __filename_parentat(dfd, name, flags, parent, last, type, NULL);
2576}
2577
2578/* does lookup, returns the object with parent locked */
2579static struct dentry *__kern_path_locked(int dfd, struct filename *name, struct path *path)
2580{
2581 struct dentry *d;
2582 struct qstr last;
2583 int type, error;
2584
2585 error = filename_parentat(dfd, name, 0, path, &last, &type);
2586 if (error)
2587 return ERR_PTR(error);
2588 if (unlikely(type != LAST_NORM)) {
2589 path_put(path);
2590 return ERR_PTR(-EINVAL);
2591 }
2592 inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
2593 d = lookup_one_qstr_excl(&last, path->dentry, 0);
2594 if (IS_ERR(d)) {
2595 inode_unlock(path->dentry->d_inode);
2596 path_put(path);
2597 }
2598 return d;
2599}
2600
2601struct dentry *kern_path_locked(const char *name, struct path *path)
2602{
2603 struct filename *filename = getname_kernel(name);
2604 struct dentry *res = __kern_path_locked(AT_FDCWD, filename, path);
2605
2606 putname(filename);
2607 return res;
2608}
2609
2610struct dentry *user_path_locked_at(int dfd, const char __user *name, struct path *path)
2611{
2612 struct filename *filename = getname(name);
2613 struct dentry *res = __kern_path_locked(dfd, filename, path);
2614
2615 putname(filename);
2616 return res;
2617}
2618EXPORT_SYMBOL(user_path_locked_at);
2619
2620int kern_path(const char *name, unsigned int flags, struct path *path)
2621{
2622 struct filename *filename = getname_kernel(name);
2623 int ret = filename_lookup(AT_FDCWD, filename, flags, path, NULL);
2624
2625 putname(filename);
2626 return ret;
2627
2628}
2629EXPORT_SYMBOL(kern_path);
2630
2631/**
2632 * vfs_path_parent_lookup - lookup a parent path relative to a dentry-vfsmount pair
2633 * @filename: filename structure
2634 * @flags: lookup flags
2635 * @parent: pointer to struct path to fill
2636 * @last: last component
2637 * @type: type of the last component
2638 * @root: pointer to struct path of the base directory
2639 */
2640int vfs_path_parent_lookup(struct filename *filename, unsigned int flags,
2641 struct path *parent, struct qstr *last, int *type,
2642 const struct path *root)
2643{
2644 return __filename_parentat(AT_FDCWD, filename, flags, parent, last,
2645 type, root);
2646}
2647EXPORT_SYMBOL(vfs_path_parent_lookup);
2648
2649/**
2650 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
2651 * @dentry: pointer to dentry of the base directory
2652 * @mnt: pointer to vfs mount of the base directory
2653 * @name: pointer to file name
2654 * @flags: lookup flags
2655 * @path: pointer to struct path to fill
2656 */
2657int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
2658 const char *name, unsigned int flags,
2659 struct path *path)
2660{
2661 struct filename *filename;
2662 struct path root = {.mnt = mnt, .dentry = dentry};
2663 int ret;
2664
2665 filename = getname_kernel(name);
2666 /* the first argument of filename_lookup() is ignored with root */
2667 ret = filename_lookup(AT_FDCWD, filename, flags, path, &root);
2668 putname(filename);
2669 return ret;
2670}
2671EXPORT_SYMBOL(vfs_path_lookup);
2672
2673static int lookup_one_common(struct mnt_idmap *idmap,
2674 const char *name, struct dentry *base, int len,
2675 struct qstr *this)
2676{
2677 this->name = name;
2678 this->len = len;
2679 this->hash = full_name_hash(base, name, len);
2680 if (!len)
2681 return -EACCES;
2682
2683 if (unlikely(name[0] == '.')) {
2684 if (len < 2 || (len == 2 && name[1] == '.'))
2685 return -EACCES;
2686 }
2687
2688 while (len--) {
2689 unsigned int c = *(const unsigned char *)name++;
2690 if (c == '/' || c == '\0')
2691 return -EACCES;
2692 }
2693 /*
2694 * See if the low-level filesystem might want
2695 * to use its own hash..
2696 */
2697 if (base->d_flags & DCACHE_OP_HASH) {
2698 int err = base->d_op->d_hash(base, this);
2699 if (err < 0)
2700 return err;
2701 }
2702
2703 return inode_permission(idmap, base->d_inode, MAY_EXEC);
2704}
2705
2706/**
2707 * try_lookup_one_len - filesystem helper to lookup single pathname component
2708 * @name: pathname component to lookup
2709 * @base: base directory to lookup from
2710 * @len: maximum length @len should be interpreted to
2711 *
2712 * Look up a dentry by name in the dcache, returning NULL if it does not
2713 * currently exist. The function does not try to create a dentry.
2714 *
2715 * Note that this routine is purely a helper for filesystem usage and should
2716 * not be called by generic code.
2717 *
2718 * The caller must hold base->i_mutex.
2719 */
2720struct dentry *try_lookup_one_len(const char *name, struct dentry *base, int len)
2721{
2722 struct qstr this;
2723 int err;
2724
2725 WARN_ON_ONCE(!inode_is_locked(base->d_inode));
2726
2727 err = lookup_one_common(&nop_mnt_idmap, name, base, len, &this);
2728 if (err)
2729 return ERR_PTR(err);
2730
2731 return lookup_dcache(&this, base, 0);
2732}
2733EXPORT_SYMBOL(try_lookup_one_len);
2734
2735/**
2736 * lookup_one_len - filesystem helper to lookup single pathname component
2737 * @name: pathname component to lookup
2738 * @base: base directory to lookup from
2739 * @len: maximum length @len should be interpreted to
2740 *
2741 * Note that this routine is purely a helper for filesystem usage and should
2742 * not be called by generic code.
2743 *
2744 * The caller must hold base->i_mutex.
2745 */
2746struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
2747{
2748 struct dentry *dentry;
2749 struct qstr this;
2750 int err;
2751
2752 WARN_ON_ONCE(!inode_is_locked(base->d_inode));
2753
2754 err = lookup_one_common(&nop_mnt_idmap, name, base, len, &this);
2755 if (err)
2756 return ERR_PTR(err);
2757
2758 dentry = lookup_dcache(&this, base, 0);
2759 return dentry ? dentry : __lookup_slow(&this, base, 0);
2760}
2761EXPORT_SYMBOL(lookup_one_len);
2762
2763/**
2764 * lookup_one - filesystem helper to lookup single pathname component
2765 * @idmap: idmap of the mount the lookup is performed from
2766 * @name: pathname component to lookup
2767 * @base: base directory to lookup from
2768 * @len: maximum length @len should be interpreted to
2769 *
2770 * Note that this routine is purely a helper for filesystem usage and should
2771 * not be called by generic code.
2772 *
2773 * The caller must hold base->i_mutex.
2774 */
2775struct dentry *lookup_one(struct mnt_idmap *idmap, const char *name,
2776 struct dentry *base, int len)
2777{
2778 struct dentry *dentry;
2779 struct qstr this;
2780 int err;
2781
2782 WARN_ON_ONCE(!inode_is_locked(base->d_inode));
2783
2784 err = lookup_one_common(idmap, name, base, len, &this);
2785 if (err)
2786 return ERR_PTR(err);
2787
2788 dentry = lookup_dcache(&this, base, 0);
2789 return dentry ? dentry : __lookup_slow(&this, base, 0);
2790}
2791EXPORT_SYMBOL(lookup_one);
2792
2793/**
2794 * lookup_one_unlocked - filesystem helper to lookup single pathname component
2795 * @idmap: idmap of the mount the lookup is performed from
2796 * @name: pathname component to lookup
2797 * @base: base directory to lookup from
2798 * @len: maximum length @len should be interpreted to
2799 *
2800 * Note that this routine is purely a helper for filesystem usage and should
2801 * not be called by generic code.
2802 *
2803 * Unlike lookup_one_len, it should be called without the parent
2804 * i_mutex held, and will take the i_mutex itself if necessary.
2805 */
2806struct dentry *lookup_one_unlocked(struct mnt_idmap *idmap,
2807 const char *name, struct dentry *base,
2808 int len)
2809{
2810 struct qstr this;
2811 int err;
2812 struct dentry *ret;
2813
2814 err = lookup_one_common(idmap, name, base, len, &this);
2815 if (err)
2816 return ERR_PTR(err);
2817
2818 ret = lookup_dcache(&this, base, 0);
2819 if (!ret)
2820 ret = lookup_slow(&this, base, 0);
2821 return ret;
2822}
2823EXPORT_SYMBOL(lookup_one_unlocked);
2824
2825/**
2826 * lookup_one_positive_unlocked - filesystem helper to lookup single
2827 * pathname component
2828 * @idmap: idmap of the mount the lookup is performed from
2829 * @name: pathname component to lookup
2830 * @base: base directory to lookup from
2831 * @len: maximum length @len should be interpreted to
2832 *
2833 * This helper will yield ERR_PTR(-ENOENT) on negatives. The helper returns
2834 * known positive or ERR_PTR(). This is what most of the users want.
2835 *
2836 * Note that pinned negative with unlocked parent _can_ become positive at any
2837 * time, so callers of lookup_one_unlocked() need to be very careful; pinned
2838 * positives have >d_inode stable, so this one avoids such problems.
2839 *
2840 * Note that this routine is purely a helper for filesystem usage and should
2841 * not be called by generic code.
2842 *
2843 * The helper should be called without i_mutex held.
2844 */
2845struct dentry *lookup_one_positive_unlocked(struct mnt_idmap *idmap,
2846 const char *name,
2847 struct dentry *base, int len)
2848{
2849 struct dentry *ret = lookup_one_unlocked(idmap, name, base, len);
2850
2851 if (!IS_ERR(ret) && d_flags_negative(smp_load_acquire(&ret->d_flags))) {
2852 dput(ret);
2853 ret = ERR_PTR(-ENOENT);
2854 }
2855 return ret;
2856}
2857EXPORT_SYMBOL(lookup_one_positive_unlocked);
2858
2859/**
2860 * lookup_one_len_unlocked - filesystem helper to lookup single pathname component
2861 * @name: pathname component to lookup
2862 * @base: base directory to lookup from
2863 * @len: maximum length @len should be interpreted to
2864 *
2865 * Note that this routine is purely a helper for filesystem usage and should
2866 * not be called by generic code.
2867 *
2868 * Unlike lookup_one_len, it should be called without the parent
2869 * i_mutex held, and will take the i_mutex itself if necessary.
2870 */
2871struct dentry *lookup_one_len_unlocked(const char *name,
2872 struct dentry *base, int len)
2873{
2874 return lookup_one_unlocked(&nop_mnt_idmap, name, base, len);
2875}
2876EXPORT_SYMBOL(lookup_one_len_unlocked);
2877
2878/*
2879 * Like lookup_one_len_unlocked(), except that it yields ERR_PTR(-ENOENT)
2880 * on negatives. Returns known positive or ERR_PTR(); that's what
2881 * most of the users want. Note that pinned negative with unlocked parent
2882 * _can_ become positive at any time, so callers of lookup_one_len_unlocked()
2883 * need to be very careful; pinned positives have ->d_inode stable, so
2884 * this one avoids such problems.
2885 */
2886struct dentry *lookup_positive_unlocked(const char *name,
2887 struct dentry *base, int len)
2888{
2889 return lookup_one_positive_unlocked(&nop_mnt_idmap, name, base, len);
2890}
2891EXPORT_SYMBOL(lookup_positive_unlocked);
2892
2893#ifdef CONFIG_UNIX98_PTYS
2894int path_pts(struct path *path)
2895{
2896 /* Find something mounted on "pts" in the same directory as
2897 * the input path.
2898 */
2899 struct dentry *parent = dget_parent(path->dentry);
2900 struct dentry *child;
2901 struct qstr this = QSTR_INIT("pts", 3);
2902
2903 if (unlikely(!path_connected(path->mnt, parent))) {
2904 dput(parent);
2905 return -ENOENT;
2906 }
2907 dput(path->dentry);
2908 path->dentry = parent;
2909 child = d_hash_and_lookup(parent, &this);
2910 if (IS_ERR_OR_NULL(child))
2911 return -ENOENT;
2912
2913 path->dentry = child;
2914 dput(parent);
2915 follow_down(path, 0);
2916 return 0;
2917}
2918#endif
2919
2920int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
2921 struct path *path, int *empty)
2922{
2923 struct filename *filename = getname_flags(name, flags, empty);
2924 int ret = filename_lookup(dfd, filename, flags, path, NULL);
2925
2926 putname(filename);
2927 return ret;
2928}
2929EXPORT_SYMBOL(user_path_at_empty);
2930
2931int __check_sticky(struct mnt_idmap *idmap, struct inode *dir,
2932 struct inode *inode)
2933{
2934 kuid_t fsuid = current_fsuid();
2935
2936 if (vfsuid_eq_kuid(i_uid_into_vfsuid(idmap, inode), fsuid))
2937 return 0;
2938 if (vfsuid_eq_kuid(i_uid_into_vfsuid(idmap, dir), fsuid))
2939 return 0;
2940 return !capable_wrt_inode_uidgid(idmap, inode, CAP_FOWNER);
2941}
2942EXPORT_SYMBOL(__check_sticky);
2943
2944/*
2945 * Check whether we can remove a link victim from directory dir, check
2946 * whether the type of victim is right.
2947 * 1. We can't do it if dir is read-only (done in permission())
2948 * 2. We should have write and exec permissions on dir
2949 * 3. We can't remove anything from append-only dir
2950 * 4. We can't do anything with immutable dir (done in permission())
2951 * 5. If the sticky bit on dir is set we should either
2952 * a. be owner of dir, or
2953 * b. be owner of victim, or
2954 * c. have CAP_FOWNER capability
2955 * 6. If the victim is append-only or immutable we can't do antyhing with
2956 * links pointing to it.
2957 * 7. If the victim has an unknown uid or gid we can't change the inode.
2958 * 8. If we were asked to remove a directory and victim isn't one - ENOTDIR.
2959 * 9. If we were asked to remove a non-directory and victim isn't one - EISDIR.
2960 * 10. We can't remove a root or mountpoint.
2961 * 11. We don't allow removal of NFS sillyrenamed files; it's handled by
2962 * nfs_async_unlink().
2963 */
2964static int may_delete(struct mnt_idmap *idmap, struct inode *dir,
2965 struct dentry *victim, bool isdir)
2966{
2967 struct inode *inode = d_backing_inode(victim);
2968 int error;
2969
2970 if (d_is_negative(victim))
2971 return -ENOENT;
2972 BUG_ON(!inode);
2973
2974 BUG_ON(victim->d_parent->d_inode != dir);
2975
2976 /* Inode writeback is not safe when the uid or gid are invalid. */
2977 if (!vfsuid_valid(i_uid_into_vfsuid(idmap, inode)) ||
2978 !vfsgid_valid(i_gid_into_vfsgid(idmap, inode)))
2979 return -EOVERFLOW;
2980
2981 audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE);
2982
2983 error = inode_permission(idmap, dir, MAY_WRITE | MAY_EXEC);
2984 if (error)
2985 return error;
2986 if (IS_APPEND(dir))
2987 return -EPERM;
2988
2989 if (check_sticky(idmap, dir, inode) || IS_APPEND(inode) ||
2990 IS_IMMUTABLE(inode) || IS_SWAPFILE(inode) ||
2991 HAS_UNMAPPED_ID(idmap, inode))
2992 return -EPERM;
2993 if (isdir) {
2994 if (!d_is_dir(victim))
2995 return -ENOTDIR;
2996 if (IS_ROOT(victim))
2997 return -EBUSY;
2998 } else if (d_is_dir(victim))
2999 return -EISDIR;
3000 if (IS_DEADDIR(dir))
3001 return -ENOENT;
3002 if (victim->d_flags & DCACHE_NFSFS_RENAMED)
3003 return -EBUSY;
3004 return 0;
3005}
3006
3007/* Check whether we can create an object with dentry child in directory
3008 * dir.
3009 * 1. We can't do it if child already exists (open has special treatment for
3010 * this case, but since we are inlined it's OK)
3011 * 2. We can't do it if dir is read-only (done in permission())
3012 * 3. We can't do it if the fs can't represent the fsuid or fsgid.
3013 * 4. We should have write and exec permissions on dir
3014 * 5. We can't do it if dir is immutable (done in permission())
3015 */
3016static inline int may_create(struct mnt_idmap *idmap,
3017 struct inode *dir, struct dentry *child)
3018{
3019 audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE);
3020 if (child->d_inode)
3021 return -EEXIST;
3022 if (IS_DEADDIR(dir))
3023 return -ENOENT;
3024 if (!fsuidgid_has_mapping(dir->i_sb, idmap))
3025 return -EOVERFLOW;
3026
3027 return inode_permission(idmap, dir, MAY_WRITE | MAY_EXEC);
3028}
3029
3030// p1 != p2, both are on the same filesystem, ->s_vfs_rename_mutex is held
3031static struct dentry *lock_two_directories(struct dentry *p1, struct dentry *p2)
3032{
3033 struct dentry *p = p1, *q = p2, *r;
3034
3035 while ((r = p->d_parent) != p2 && r != p)
3036 p = r;
3037 if (r == p2) {
3038 // p is a child of p2 and an ancestor of p1 or p1 itself
3039 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT);
3040 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT2);
3041 return p;
3042 }
3043 // p is the root of connected component that contains p1
3044 // p2 does not occur on the path from p to p1
3045 while ((r = q->d_parent) != p1 && r != p && r != q)
3046 q = r;
3047 if (r == p1) {
3048 // q is a child of p1 and an ancestor of p2 or p2 itself
3049 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
3050 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT2);
3051 return q;
3052 } else if (likely(r == p)) {
3053 // both p2 and p1 are descendents of p
3054 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
3055 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT2);
3056 return NULL;
3057 } else { // no common ancestor at the time we'd been called
3058 mutex_unlock(&p1->d_sb->s_vfs_rename_mutex);
3059 return ERR_PTR(-EXDEV);
3060 }
3061}
3062
3063/*
3064 * p1 and p2 should be directories on the same fs.
3065 */
3066struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
3067{
3068 if (p1 == p2) {
3069 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
3070 return NULL;
3071 }
3072
3073 mutex_lock(&p1->d_sb->s_vfs_rename_mutex);
3074 return lock_two_directories(p1, p2);
3075}
3076EXPORT_SYMBOL(lock_rename);
3077
3078/*
3079 * c1 and p2 should be on the same fs.
3080 */
3081struct dentry *lock_rename_child(struct dentry *c1, struct dentry *p2)
3082{
3083 if (READ_ONCE(c1->d_parent) == p2) {
3084 /*
3085 * hopefully won't need to touch ->s_vfs_rename_mutex at all.
3086 */
3087 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT);
3088 /*
3089 * now that p2 is locked, nobody can move in or out of it,
3090 * so the test below is safe.
3091 */
3092 if (likely(c1->d_parent == p2))
3093 return NULL;
3094
3095 /*
3096 * c1 got moved out of p2 while we'd been taking locks;
3097 * unlock and fall back to slow case.
3098 */
3099 inode_unlock(p2->d_inode);
3100 }
3101
3102 mutex_lock(&c1->d_sb->s_vfs_rename_mutex);
3103 /*
3104 * nobody can move out of any directories on this fs.
3105 */
3106 if (likely(c1->d_parent != p2))
3107 return lock_two_directories(c1->d_parent, p2);
3108
3109 /*
3110 * c1 got moved into p2 while we were taking locks;
3111 * we need p2 locked and ->s_vfs_rename_mutex unlocked,
3112 * for consistency with lock_rename().
3113 */
3114 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT);
3115 mutex_unlock(&c1->d_sb->s_vfs_rename_mutex);
3116 return NULL;
3117}
3118EXPORT_SYMBOL(lock_rename_child);
3119
3120void unlock_rename(struct dentry *p1, struct dentry *p2)
3121{
3122 inode_unlock(p1->d_inode);
3123 if (p1 != p2) {
3124 inode_unlock(p2->d_inode);
3125 mutex_unlock(&p1->d_sb->s_vfs_rename_mutex);
3126 }
3127}
3128EXPORT_SYMBOL(unlock_rename);
3129
3130/**
3131 * vfs_prepare_mode - prepare the mode to be used for a new inode
3132 * @idmap: idmap of the mount the inode was found from
3133 * @dir: parent directory of the new inode
3134 * @mode: mode of the new inode
3135 * @mask_perms: allowed permission by the vfs
3136 * @type: type of file to be created
3137 *
3138 * This helper consolidates and enforces vfs restrictions on the @mode of a new
3139 * object to be created.
3140 *
3141 * Umask stripping depends on whether the filesystem supports POSIX ACLs (see
3142 * the kernel documentation for mode_strip_umask()). Moving umask stripping
3143 * after setgid stripping allows the same ordering for both non-POSIX ACL and
3144 * POSIX ACL supporting filesystems.
3145 *
3146 * Note that it's currently valid for @type to be 0 if a directory is created.
3147 * Filesystems raise that flag individually and we need to check whether each
3148 * filesystem can deal with receiving S_IFDIR from the vfs before we enforce a
3149 * non-zero type.
3150 *
3151 * Returns: mode to be passed to the filesystem
3152 */
3153static inline umode_t vfs_prepare_mode(struct mnt_idmap *idmap,
3154 const struct inode *dir, umode_t mode,
3155 umode_t mask_perms, umode_t type)
3156{
3157 mode = mode_strip_sgid(idmap, dir, mode);
3158 mode = mode_strip_umask(dir, mode);
3159
3160 /*
3161 * Apply the vfs mandated allowed permission mask and set the type of
3162 * file to be created before we call into the filesystem.
3163 */
3164 mode &= (mask_perms & ~S_IFMT);
3165 mode |= (type & S_IFMT);
3166
3167 return mode;
3168}
3169
3170/**
3171 * vfs_create - create new file
3172 * @idmap: idmap of the mount the inode was found from
3173 * @dir: inode of @dentry
3174 * @dentry: pointer to dentry of the base directory
3175 * @mode: mode of the new file
3176 * @want_excl: whether the file must not yet exist
3177 *
3178 * Create a new file.
3179 *
3180 * If the inode has been found through an idmapped mount the idmap of
3181 * the vfsmount must be passed through @idmap. This function will then take
3182 * care to map the inode according to @idmap before checking permissions.
3183 * On non-idmapped mounts or if permission checking is to be performed on the
3184 * raw inode simply pass @nop_mnt_idmap.
3185 */
3186int vfs_create(struct mnt_idmap *idmap, struct inode *dir,
3187 struct dentry *dentry, umode_t mode, bool want_excl)
3188{
3189 int error;
3190
3191 error = may_create(idmap, dir, dentry);
3192 if (error)
3193 return error;
3194
3195 if (!dir->i_op->create)
3196 return -EACCES; /* shouldn't it be ENOSYS? */
3197
3198 mode = vfs_prepare_mode(idmap, dir, mode, S_IALLUGO, S_IFREG);
3199 error = security_inode_create(dir, dentry, mode);
3200 if (error)
3201 return error;
3202 error = dir->i_op->create(idmap, dir, dentry, mode, want_excl);
3203 if (!error)
3204 fsnotify_create(dir, dentry);
3205 return error;
3206}
3207EXPORT_SYMBOL(vfs_create);
3208
3209int vfs_mkobj(struct dentry *dentry, umode_t mode,
3210 int (*f)(struct dentry *, umode_t, void *),
3211 void *arg)
3212{
3213 struct inode *dir = dentry->d_parent->d_inode;
3214 int error = may_create(&nop_mnt_idmap, dir, dentry);
3215 if (error)
3216 return error;
3217
3218 mode &= S_IALLUGO;
3219 mode |= S_IFREG;
3220 error = security_inode_create(dir, dentry, mode);
3221 if (error)
3222 return error;
3223 error = f(dentry, mode, arg);
3224 if (!error)
3225 fsnotify_create(dir, dentry);
3226 return error;
3227}
3228EXPORT_SYMBOL(vfs_mkobj);
3229
3230bool may_open_dev(const struct path *path)
3231{
3232 return !(path->mnt->mnt_flags & MNT_NODEV) &&
3233 !(path->mnt->mnt_sb->s_iflags & SB_I_NODEV);
3234}
3235
3236static int may_open(struct mnt_idmap *idmap, const struct path *path,
3237 int acc_mode, int flag)
3238{
3239 struct dentry *dentry = path->dentry;
3240 struct inode *inode = dentry->d_inode;
3241 int error;
3242
3243 if (!inode)
3244 return -ENOENT;
3245
3246 switch (inode->i_mode & S_IFMT) {
3247 case S_IFLNK:
3248 return -ELOOP;
3249 case S_IFDIR:
3250 if (acc_mode & MAY_WRITE)
3251 return -EISDIR;
3252 if (acc_mode & MAY_EXEC)
3253 return -EACCES;
3254 break;
3255 case S_IFBLK:
3256 case S_IFCHR:
3257 if (!may_open_dev(path))
3258 return -EACCES;
3259 fallthrough;
3260 case S_IFIFO:
3261 case S_IFSOCK:
3262 if (acc_mode & MAY_EXEC)
3263 return -EACCES;
3264 flag &= ~O_TRUNC;
3265 break;
3266 case S_IFREG:
3267 if ((acc_mode & MAY_EXEC) && path_noexec(path))
3268 return -EACCES;
3269 break;
3270 }
3271
3272 error = inode_permission(idmap, inode, MAY_OPEN | acc_mode);
3273 if (error)
3274 return error;
3275
3276 /*
3277 * An append-only file must be opened in append mode for writing.
3278 */
3279 if (IS_APPEND(inode)) {
3280 if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
3281 return -EPERM;
3282 if (flag & O_TRUNC)
3283 return -EPERM;
3284 }
3285
3286 /* O_NOATIME can only be set by the owner or superuser */
3287 if (flag & O_NOATIME && !inode_owner_or_capable(idmap, inode))
3288 return -EPERM;
3289
3290 return 0;
3291}
3292
3293static int handle_truncate(struct mnt_idmap *idmap, struct file *filp)
3294{
3295 const struct path *path = &filp->f_path;
3296 struct inode *inode = path->dentry->d_inode;
3297 int error = get_write_access(inode);
3298 if (error)
3299 return error;
3300
3301 error = security_file_truncate(filp);
3302 if (!error) {
3303 error = do_truncate(idmap, path->dentry, 0,
3304 ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
3305 filp);
3306 }
3307 put_write_access(inode);
3308 return error;
3309}
3310
3311static inline int open_to_namei_flags(int flag)
3312{
3313 if ((flag & O_ACCMODE) == 3)
3314 flag--;
3315 return flag;
3316}
3317
3318static int may_o_create(struct mnt_idmap *idmap,
3319 const struct path *dir, struct dentry *dentry,
3320 umode_t mode)
3321{
3322 int error = security_path_mknod(dir, dentry, mode, 0);
3323 if (error)
3324 return error;
3325
3326 if (!fsuidgid_has_mapping(dir->dentry->d_sb, idmap))
3327 return -EOVERFLOW;
3328
3329 error = inode_permission(idmap, dir->dentry->d_inode,
3330 MAY_WRITE | MAY_EXEC);
3331 if (error)
3332 return error;
3333
3334 return security_inode_create(dir->dentry->d_inode, dentry, mode);
3335}
3336
3337/*
3338 * Attempt to atomically look up, create and open a file from a negative
3339 * dentry.
3340 *
3341 * Returns 0 if successful. The file will have been created and attached to
3342 * @file by the filesystem calling finish_open().
3343 *
3344 * If the file was looked up only or didn't need creating, FMODE_OPENED won't
3345 * be set. The caller will need to perform the open themselves. @path will
3346 * have been updated to point to the new dentry. This may be negative.
3347 *
3348 * Returns an error code otherwise.
3349 */
3350static struct dentry *atomic_open(struct nameidata *nd, struct dentry *dentry,
3351 struct file *file,
3352 int open_flag, umode_t mode)
3353{
3354 struct dentry *const DENTRY_NOT_SET = (void *) -1UL;
3355 struct inode *dir = nd->path.dentry->d_inode;
3356 int error;
3357
3358 if (nd->flags & LOOKUP_DIRECTORY)
3359 open_flag |= O_DIRECTORY;
3360
3361 file->f_path.dentry = DENTRY_NOT_SET;
3362 file->f_path.mnt = nd->path.mnt;
3363 error = dir->i_op->atomic_open(dir, dentry, file,
3364 open_to_namei_flags(open_flag), mode);
3365 d_lookup_done(dentry);
3366 if (!error) {
3367 if (file->f_mode & FMODE_OPENED) {
3368 if (unlikely(dentry != file->f_path.dentry)) {
3369 dput(dentry);
3370 dentry = dget(file->f_path.dentry);
3371 }
3372 } else if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) {
3373 error = -EIO;
3374 } else {
3375 if (file->f_path.dentry) {
3376 dput(dentry);
3377 dentry = file->f_path.dentry;
3378 }
3379 if (unlikely(d_is_negative(dentry)))
3380 error = -ENOENT;
3381 }
3382 }
3383 if (error) {
3384 dput(dentry);
3385 dentry = ERR_PTR(error);
3386 }
3387 return dentry;
3388}
3389
3390/*
3391 * Look up and maybe create and open the last component.
3392 *
3393 * Must be called with parent locked (exclusive in O_CREAT case).
3394 *
3395 * Returns 0 on success, that is, if
3396 * the file was successfully atomically created (if necessary) and opened, or
3397 * the file was not completely opened at this time, though lookups and
3398 * creations were performed.
3399 * These case are distinguished by presence of FMODE_OPENED on file->f_mode.
3400 * In the latter case dentry returned in @path might be negative if O_CREAT
3401 * hadn't been specified.
3402 *
3403 * An error code is returned on failure.
3404 */
3405static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
3406 const struct open_flags *op,
3407 bool got_write)
3408{
3409 struct mnt_idmap *idmap;
3410 struct dentry *dir = nd->path.dentry;
3411 struct inode *dir_inode = dir->d_inode;
3412 int open_flag = op->open_flag;
3413 struct dentry *dentry;
3414 int error, create_error = 0;
3415 umode_t mode = op->mode;
3416 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
3417
3418 if (unlikely(IS_DEADDIR(dir_inode)))
3419 return ERR_PTR(-ENOENT);
3420
3421 file->f_mode &= ~FMODE_CREATED;
3422 dentry = d_lookup(dir, &nd->last);
3423 for (;;) {
3424 if (!dentry) {
3425 dentry = d_alloc_parallel(dir, &nd->last, &wq);
3426 if (IS_ERR(dentry))
3427 return dentry;
3428 }
3429 if (d_in_lookup(dentry))
3430 break;
3431
3432 error = d_revalidate(dentry, nd->flags);
3433 if (likely(error > 0))
3434 break;
3435 if (error)
3436 goto out_dput;
3437 d_invalidate(dentry);
3438 dput(dentry);
3439 dentry = NULL;
3440 }
3441 if (dentry->d_inode) {
3442 /* Cached positive dentry: will open in f_op->open */
3443 return dentry;
3444 }
3445
3446 /*
3447 * Checking write permission is tricky, bacuse we don't know if we are
3448 * going to actually need it: O_CREAT opens should work as long as the
3449 * file exists. But checking existence breaks atomicity. The trick is
3450 * to check access and if not granted clear O_CREAT from the flags.
3451 *
3452 * Another problem is returing the "right" error value (e.g. for an
3453 * O_EXCL open we want to return EEXIST not EROFS).
3454 */
3455 if (unlikely(!got_write))
3456 open_flag &= ~O_TRUNC;
3457 idmap = mnt_idmap(nd->path.mnt);
3458 if (open_flag & O_CREAT) {
3459 if (open_flag & O_EXCL)
3460 open_flag &= ~O_TRUNC;
3461 mode = vfs_prepare_mode(idmap, dir->d_inode, mode, mode, mode);
3462 if (likely(got_write))
3463 create_error = may_o_create(idmap, &nd->path,
3464 dentry, mode);
3465 else
3466 create_error = -EROFS;
3467 }
3468 if (create_error)
3469 open_flag &= ~O_CREAT;
3470 if (dir_inode->i_op->atomic_open) {
3471 dentry = atomic_open(nd, dentry, file, open_flag, mode);
3472 if (unlikely(create_error) && dentry == ERR_PTR(-ENOENT))
3473 dentry = ERR_PTR(create_error);
3474 return dentry;
3475 }
3476
3477 if (d_in_lookup(dentry)) {
3478 struct dentry *res = dir_inode->i_op->lookup(dir_inode, dentry,
3479 nd->flags);
3480 d_lookup_done(dentry);
3481 if (unlikely(res)) {
3482 if (IS_ERR(res)) {
3483 error = PTR_ERR(res);
3484 goto out_dput;
3485 }
3486 dput(dentry);
3487 dentry = res;
3488 }
3489 }
3490
3491 /* Negative dentry, just create the file */
3492 if (!dentry->d_inode && (open_flag & O_CREAT)) {
3493 file->f_mode |= FMODE_CREATED;
3494 audit_inode_child(dir_inode, dentry, AUDIT_TYPE_CHILD_CREATE);
3495 if (!dir_inode->i_op->create) {
3496 error = -EACCES;
3497 goto out_dput;
3498 }
3499
3500 error = dir_inode->i_op->create(idmap, dir_inode, dentry,
3501 mode, open_flag & O_EXCL);
3502 if (error)
3503 goto out_dput;
3504 }
3505 if (unlikely(create_error) && !dentry->d_inode) {
3506 error = create_error;
3507 goto out_dput;
3508 }
3509 return dentry;
3510
3511out_dput:
3512 dput(dentry);
3513 return ERR_PTR(error);
3514}
3515
3516static const char *open_last_lookups(struct nameidata *nd,
3517 struct file *file, const struct open_flags *op)
3518{
3519 struct dentry *dir = nd->path.dentry;
3520 int open_flag = op->open_flag;
3521 bool got_write = false;
3522 struct dentry *dentry;
3523 const char *res;
3524
3525 nd->flags |= op->intent;
3526
3527 if (nd->last_type != LAST_NORM) {
3528 if (nd->depth)
3529 put_link(nd);
3530 return handle_dots(nd, nd->last_type);
3531 }
3532
3533 if (!(open_flag & O_CREAT)) {
3534 if (nd->last.name[nd->last.len])
3535 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
3536 /* we _can_ be in RCU mode here */
3537 dentry = lookup_fast(nd);
3538 if (IS_ERR(dentry))
3539 return ERR_CAST(dentry);
3540 if (likely(dentry))
3541 goto finish_lookup;
3542
3543 if (WARN_ON_ONCE(nd->flags & LOOKUP_RCU))
3544 return ERR_PTR(-ECHILD);
3545 } else {
3546 /* create side of things */
3547 if (nd->flags & LOOKUP_RCU) {
3548 if (!try_to_unlazy(nd))
3549 return ERR_PTR(-ECHILD);
3550 }
3551 audit_inode(nd->name, dir, AUDIT_INODE_PARENT);
3552 /* trailing slashes? */
3553 if (unlikely(nd->last.name[nd->last.len]))
3554 return ERR_PTR(-EISDIR);
3555 }
3556
3557 if (open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
3558 got_write = !mnt_want_write(nd->path.mnt);
3559 /*
3560 * do _not_ fail yet - we might not need that or fail with
3561 * a different error; let lookup_open() decide; we'll be
3562 * dropping this one anyway.
3563 */
3564 }
3565 if (open_flag & O_CREAT)
3566 inode_lock(dir->d_inode);
3567 else
3568 inode_lock_shared(dir->d_inode);
3569 dentry = lookup_open(nd, file, op, got_write);
3570 if (!IS_ERR(dentry) && (file->f_mode & FMODE_CREATED))
3571 fsnotify_create(dir->d_inode, dentry);
3572 if (open_flag & O_CREAT)
3573 inode_unlock(dir->d_inode);
3574 else
3575 inode_unlock_shared(dir->d_inode);
3576
3577 if (got_write)
3578 mnt_drop_write(nd->path.mnt);
3579
3580 if (IS_ERR(dentry))
3581 return ERR_CAST(dentry);
3582
3583 if (file->f_mode & (FMODE_OPENED | FMODE_CREATED)) {
3584 dput(nd->path.dentry);
3585 nd->path.dentry = dentry;
3586 return NULL;
3587 }
3588
3589finish_lookup:
3590 if (nd->depth)
3591 put_link(nd);
3592 res = step_into(nd, WALK_TRAILING, dentry);
3593 if (unlikely(res))
3594 nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
3595 return res;
3596}
3597
3598/*
3599 * Handle the last step of open()
3600 */
3601static int do_open(struct nameidata *nd,
3602 struct file *file, const struct open_flags *op)
3603{
3604 struct mnt_idmap *idmap;
3605 int open_flag = op->open_flag;
3606 bool do_truncate;
3607 int acc_mode;
3608 int error;
3609
3610 if (!(file->f_mode & (FMODE_OPENED | FMODE_CREATED))) {
3611 error = complete_walk(nd);
3612 if (error)
3613 return error;
3614 }
3615 if (!(file->f_mode & FMODE_CREATED))
3616 audit_inode(nd->name, nd->path.dentry, 0);
3617 idmap = mnt_idmap(nd->path.mnt);
3618 if (open_flag & O_CREAT) {
3619 if ((open_flag & O_EXCL) && !(file->f_mode & FMODE_CREATED))
3620 return -EEXIST;
3621 if (d_is_dir(nd->path.dentry))
3622 return -EISDIR;
3623 error = may_create_in_sticky(idmap, nd,
3624 d_backing_inode(nd->path.dentry));
3625 if (unlikely(error))
3626 return error;
3627 }
3628 if ((nd->flags & LOOKUP_DIRECTORY) && !d_can_lookup(nd->path.dentry))
3629 return -ENOTDIR;
3630
3631 do_truncate = false;
3632 acc_mode = op->acc_mode;
3633 if (file->f_mode & FMODE_CREATED) {
3634 /* Don't check for write permission, don't truncate */
3635 open_flag &= ~O_TRUNC;
3636 acc_mode = 0;
3637 } else if (d_is_reg(nd->path.dentry) && open_flag & O_TRUNC) {
3638 error = mnt_want_write(nd->path.mnt);
3639 if (error)
3640 return error;
3641 do_truncate = true;
3642 }
3643 error = may_open(idmap, &nd->path, acc_mode, open_flag);
3644 if (!error && !(file->f_mode & FMODE_OPENED))
3645 error = vfs_open(&nd->path, file);
3646 if (!error)
3647 error = ima_file_check(file, op->acc_mode);
3648 if (!error && do_truncate)
3649 error = handle_truncate(idmap, file);
3650 if (unlikely(error > 0)) {
3651 WARN_ON(1);
3652 error = -EINVAL;
3653 }
3654 if (do_truncate)
3655 mnt_drop_write(nd->path.mnt);
3656 return error;
3657}
3658
3659/**
3660 * vfs_tmpfile - create tmpfile
3661 * @idmap: idmap of the mount the inode was found from
3662 * @parentpath: pointer to the path of the base directory
3663 * @file: file descriptor of the new tmpfile
3664 * @mode: mode of the new tmpfile
3665 *
3666 * Create a temporary file.
3667 *
3668 * If the inode has been found through an idmapped mount the idmap of
3669 * the vfsmount must be passed through @idmap. This function will then take
3670 * care to map the inode according to @idmap before checking permissions.
3671 * On non-idmapped mounts or if permission checking is to be performed on the
3672 * raw inode simply pass @nop_mnt_idmap.
3673 */
3674static int vfs_tmpfile(struct mnt_idmap *idmap,
3675 const struct path *parentpath,
3676 struct file *file, umode_t mode)
3677{
3678 struct dentry *child;
3679 struct inode *dir = d_inode(parentpath->dentry);
3680 struct inode *inode;
3681 int error;
3682 int open_flag = file->f_flags;
3683
3684 /* we want directory to be writable */
3685 error = inode_permission(idmap, dir, MAY_WRITE | MAY_EXEC);
3686 if (error)
3687 return error;
3688 if (!dir->i_op->tmpfile)
3689 return -EOPNOTSUPP;
3690 child = d_alloc(parentpath->dentry, &slash_name);
3691 if (unlikely(!child))
3692 return -ENOMEM;
3693 file->f_path.mnt = parentpath->mnt;
3694 file->f_path.dentry = child;
3695 mode = vfs_prepare_mode(idmap, dir, mode, mode, mode);
3696 error = dir->i_op->tmpfile(idmap, dir, file, mode);
3697 dput(child);
3698 if (error)
3699 return error;
3700 /* Don't check for other permissions, the inode was just created */
3701 error = may_open(idmap, &file->f_path, 0, file->f_flags);
3702 if (error)
3703 return error;
3704 inode = file_inode(file);
3705 if (!(open_flag & O_EXCL)) {
3706 spin_lock(&inode->i_lock);
3707 inode->i_state |= I_LINKABLE;
3708 spin_unlock(&inode->i_lock);
3709 }
3710 ima_post_create_tmpfile(idmap, inode);
3711 return 0;
3712}
3713
3714/**
3715 * kernel_tmpfile_open - open a tmpfile for kernel internal use
3716 * @idmap: idmap of the mount the inode was found from
3717 * @parentpath: path of the base directory
3718 * @mode: mode of the new tmpfile
3719 * @open_flag: flags
3720 * @cred: credentials for open
3721 *
3722 * Create and open a temporary file. The file is not accounted in nr_files,
3723 * hence this is only for kernel internal use, and must not be installed into
3724 * file tables or such.
3725 */
3726struct file *kernel_tmpfile_open(struct mnt_idmap *idmap,
3727 const struct path *parentpath,
3728 umode_t mode, int open_flag,
3729 const struct cred *cred)
3730{
3731 struct file *file;
3732 int error;
3733
3734 file = alloc_empty_file_noaccount(open_flag, cred);
3735 if (IS_ERR(file))
3736 return file;
3737
3738 error = vfs_tmpfile(idmap, parentpath, file, mode);
3739 if (error) {
3740 fput(file);
3741 file = ERR_PTR(error);
3742 }
3743 return file;
3744}
3745EXPORT_SYMBOL(kernel_tmpfile_open);
3746
3747static int do_tmpfile(struct nameidata *nd, unsigned flags,
3748 const struct open_flags *op,
3749 struct file *file)
3750{
3751 struct path path;
3752 int error = path_lookupat(nd, flags | LOOKUP_DIRECTORY, &path);
3753
3754 if (unlikely(error))
3755 return error;
3756 error = mnt_want_write(path.mnt);
3757 if (unlikely(error))
3758 goto out;
3759 error = vfs_tmpfile(mnt_idmap(path.mnt), &path, file, op->mode);
3760 if (error)
3761 goto out2;
3762 audit_inode(nd->name, file->f_path.dentry, 0);
3763out2:
3764 mnt_drop_write(path.mnt);
3765out:
3766 path_put(&path);
3767 return error;
3768}
3769
3770static int do_o_path(struct nameidata *nd, unsigned flags, struct file *file)
3771{
3772 struct path path;
3773 int error = path_lookupat(nd, flags, &path);
3774 if (!error) {
3775 audit_inode(nd->name, path.dentry, 0);
3776 error = vfs_open(&path, file);
3777 path_put(&path);
3778 }
3779 return error;
3780}
3781
3782static struct file *path_openat(struct nameidata *nd,
3783 const struct open_flags *op, unsigned flags)
3784{
3785 struct file *file;
3786 int error;
3787
3788 file = alloc_empty_file(op->open_flag, current_cred());
3789 if (IS_ERR(file))
3790 return file;
3791
3792 if (unlikely(file->f_flags & __O_TMPFILE)) {
3793 error = do_tmpfile(nd, flags, op, file);
3794 } else if (unlikely(file->f_flags & O_PATH)) {
3795 error = do_o_path(nd, flags, file);
3796 } else {
3797 const char *s = path_init(nd, flags);
3798 while (!(error = link_path_walk(s, nd)) &&
3799 (s = open_last_lookups(nd, file, op)) != NULL)
3800 ;
3801 if (!error)
3802 error = do_open(nd, file, op);
3803 terminate_walk(nd);
3804 }
3805 if (likely(!error)) {
3806 if (likely(file->f_mode & FMODE_OPENED))
3807 return file;
3808 WARN_ON(1);
3809 error = -EINVAL;
3810 }
3811 fput(file);
3812 if (error == -EOPENSTALE) {
3813 if (flags & LOOKUP_RCU)
3814 error = -ECHILD;
3815 else
3816 error = -ESTALE;
3817 }
3818 return ERR_PTR(error);
3819}
3820
3821struct file *do_filp_open(int dfd, struct filename *pathname,
3822 const struct open_flags *op)
3823{
3824 struct nameidata nd;
3825 int flags = op->lookup_flags;
3826 struct file *filp;
3827
3828 set_nameidata(&nd, dfd, pathname, NULL);
3829 filp = path_openat(&nd, op, flags | LOOKUP_RCU);
3830 if (unlikely(filp == ERR_PTR(-ECHILD)))
3831 filp = path_openat(&nd, op, flags);
3832 if (unlikely(filp == ERR_PTR(-ESTALE)))
3833 filp = path_openat(&nd, op, flags | LOOKUP_REVAL);
3834 restore_nameidata();
3835 return filp;
3836}
3837
3838struct file *do_file_open_root(const struct path *root,
3839 const char *name, const struct open_flags *op)
3840{
3841 struct nameidata nd;
3842 struct file *file;
3843 struct filename *filename;
3844 int flags = op->lookup_flags;
3845
3846 if (d_is_symlink(root->dentry) && op->intent & LOOKUP_OPEN)
3847 return ERR_PTR(-ELOOP);
3848
3849 filename = getname_kernel(name);
3850 if (IS_ERR(filename))
3851 return ERR_CAST(filename);
3852
3853 set_nameidata(&nd, -1, filename, root);
3854 file = path_openat(&nd, op, flags | LOOKUP_RCU);
3855 if (unlikely(file == ERR_PTR(-ECHILD)))
3856 file = path_openat(&nd, op, flags);
3857 if (unlikely(file == ERR_PTR(-ESTALE)))
3858 file = path_openat(&nd, op, flags | LOOKUP_REVAL);
3859 restore_nameidata();
3860 putname(filename);
3861 return file;
3862}
3863
3864static struct dentry *filename_create(int dfd, struct filename *name,
3865 struct path *path, unsigned int lookup_flags)
3866{
3867 struct dentry *dentry = ERR_PTR(-EEXIST);
3868 struct qstr last;
3869 bool want_dir = lookup_flags & LOOKUP_DIRECTORY;
3870 unsigned int reval_flag = lookup_flags & LOOKUP_REVAL;
3871 unsigned int create_flags = LOOKUP_CREATE | LOOKUP_EXCL;
3872 int type;
3873 int err2;
3874 int error;
3875
3876 error = filename_parentat(dfd, name, reval_flag, path, &last, &type);
3877 if (error)
3878 return ERR_PTR(error);
3879
3880 /*
3881 * Yucky last component or no last component at all?
3882 * (foo/., foo/.., /////)
3883 */
3884 if (unlikely(type != LAST_NORM))
3885 goto out;
3886
3887 /* don't fail immediately if it's r/o, at least try to report other errors */
3888 err2 = mnt_want_write(path->mnt);
3889 /*
3890 * Do the final lookup. Suppress 'create' if there is a trailing
3891 * '/', and a directory wasn't requested.
3892 */
3893 if (last.name[last.len] && !want_dir)
3894 create_flags = 0;
3895 inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
3896 dentry = lookup_one_qstr_excl(&last, path->dentry,
3897 reval_flag | create_flags);
3898 if (IS_ERR(dentry))
3899 goto unlock;
3900
3901 error = -EEXIST;
3902 if (d_is_positive(dentry))
3903 goto fail;
3904
3905 /*
3906 * Special case - lookup gave negative, but... we had foo/bar/
3907 * From the vfs_mknod() POV we just have a negative dentry -
3908 * all is fine. Let's be bastards - you had / on the end, you've
3909 * been asking for (non-existent) directory. -ENOENT for you.
3910 */
3911 if (unlikely(!create_flags)) {
3912 error = -ENOENT;
3913 goto fail;
3914 }
3915 if (unlikely(err2)) {
3916 error = err2;
3917 goto fail;
3918 }
3919 return dentry;
3920fail:
3921 dput(dentry);
3922 dentry = ERR_PTR(error);
3923unlock:
3924 inode_unlock(path->dentry->d_inode);
3925 if (!err2)
3926 mnt_drop_write(path->mnt);
3927out:
3928 path_put(path);
3929 return dentry;
3930}
3931
3932struct dentry *kern_path_create(int dfd, const char *pathname,
3933 struct path *path, unsigned int lookup_flags)
3934{
3935 struct filename *filename = getname_kernel(pathname);
3936 struct dentry *res = filename_create(dfd, filename, path, lookup_flags);
3937
3938 putname(filename);
3939 return res;
3940}
3941EXPORT_SYMBOL(kern_path_create);
3942
3943void done_path_create(struct path *path, struct dentry *dentry)
3944{
3945 dput(dentry);
3946 inode_unlock(path->dentry->d_inode);
3947 mnt_drop_write(path->mnt);
3948 path_put(path);
3949}
3950EXPORT_SYMBOL(done_path_create);
3951
3952inline struct dentry *user_path_create(int dfd, const char __user *pathname,
3953 struct path *path, unsigned int lookup_flags)
3954{
3955 struct filename *filename = getname(pathname);
3956 struct dentry *res = filename_create(dfd, filename, path, lookup_flags);
3957
3958 putname(filename);
3959 return res;
3960}
3961EXPORT_SYMBOL(user_path_create);
3962
3963/**
3964 * vfs_mknod - create device node or file
3965 * @idmap: idmap of the mount the inode was found from
3966 * @dir: inode of @dentry
3967 * @dentry: pointer to dentry of the base directory
3968 * @mode: mode of the new device node or file
3969 * @dev: device number of device to create
3970 *
3971 * Create a device node or file.
3972 *
3973 * If the inode has been found through an idmapped mount the idmap of
3974 * the vfsmount must be passed through @idmap. This function will then take
3975 * care to map the inode according to @idmap before checking permissions.
3976 * On non-idmapped mounts or if permission checking is to be performed on the
3977 * raw inode simply pass @nop_mnt_idmap.
3978 */
3979int vfs_mknod(struct mnt_idmap *idmap, struct inode *dir,
3980 struct dentry *dentry, umode_t mode, dev_t dev)
3981{
3982 bool is_whiteout = S_ISCHR(mode) && dev == WHITEOUT_DEV;
3983 int error = may_create(idmap, dir, dentry);
3984
3985 if (error)
3986 return error;
3987
3988 if ((S_ISCHR(mode) || S_ISBLK(mode)) && !is_whiteout &&
3989 !capable(CAP_MKNOD))
3990 return -EPERM;
3991
3992 if (!dir->i_op->mknod)
3993 return -EPERM;
3994
3995 mode = vfs_prepare_mode(idmap, dir, mode, mode, mode);
3996 error = devcgroup_inode_mknod(mode, dev);
3997 if (error)
3998 return error;
3999
4000 error = security_inode_mknod(dir, dentry, mode, dev);
4001 if (error)
4002 return error;
4003
4004 error = dir->i_op->mknod(idmap, dir, dentry, mode, dev);
4005 if (!error)
4006 fsnotify_create(dir, dentry);
4007 return error;
4008}
4009EXPORT_SYMBOL(vfs_mknod);
4010
4011static int may_mknod(umode_t mode)
4012{
4013 switch (mode & S_IFMT) {
4014 case S_IFREG:
4015 case S_IFCHR:
4016 case S_IFBLK:
4017 case S_IFIFO:
4018 case S_IFSOCK:
4019 case 0: /* zero mode translates to S_IFREG */
4020 return 0;
4021 case S_IFDIR:
4022 return -EPERM;
4023 default:
4024 return -EINVAL;
4025 }
4026}
4027
4028static int do_mknodat(int dfd, struct filename *name, umode_t mode,
4029 unsigned int dev)
4030{
4031 struct mnt_idmap *idmap;
4032 struct dentry *dentry;
4033 struct path path;
4034 int error;
4035 unsigned int lookup_flags = 0;
4036
4037 error = may_mknod(mode);
4038 if (error)
4039 goto out1;
4040retry:
4041 dentry = filename_create(dfd, name, &path, lookup_flags);
4042 error = PTR_ERR(dentry);
4043 if (IS_ERR(dentry))
4044 goto out1;
4045
4046 error = security_path_mknod(&path, dentry,
4047 mode_strip_umask(path.dentry->d_inode, mode), dev);
4048 if (error)
4049 goto out2;
4050
4051 idmap = mnt_idmap(path.mnt);
4052 switch (mode & S_IFMT) {
4053 case 0: case S_IFREG:
4054 error = vfs_create(idmap, path.dentry->d_inode,
4055 dentry, mode, true);
4056 if (!error)
4057 ima_post_path_mknod(idmap, dentry);
4058 break;
4059 case S_IFCHR: case S_IFBLK:
4060 error = vfs_mknod(idmap, path.dentry->d_inode,
4061 dentry, mode, new_decode_dev(dev));
4062 break;
4063 case S_IFIFO: case S_IFSOCK:
4064 error = vfs_mknod(idmap, path.dentry->d_inode,
4065 dentry, mode, 0);
4066 break;
4067 }
4068out2:
4069 done_path_create(&path, dentry);
4070 if (retry_estale(error, lookup_flags)) {
4071 lookup_flags |= LOOKUP_REVAL;
4072 goto retry;
4073 }
4074out1:
4075 putname(name);
4076 return error;
4077}
4078
4079SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,
4080 unsigned int, dev)
4081{
4082 return do_mknodat(dfd, getname(filename), mode, dev);
4083}
4084
4085SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev)
4086{
4087 return do_mknodat(AT_FDCWD, getname(filename), mode, dev);
4088}
4089
4090/**
4091 * vfs_mkdir - create directory
4092 * @idmap: idmap of the mount the inode was found from
4093 * @dir: inode of @dentry
4094 * @dentry: pointer to dentry of the base directory
4095 * @mode: mode of the new directory
4096 *
4097 * Create a directory.
4098 *
4099 * If the inode has been found through an idmapped mount the idmap of
4100 * the vfsmount must be passed through @idmap. This function will then take
4101 * care to map the inode according to @idmap before checking permissions.
4102 * On non-idmapped mounts or if permission checking is to be performed on the
4103 * raw inode simply pass @nop_mnt_idmap.
4104 */
4105int vfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
4106 struct dentry *dentry, umode_t mode)
4107{
4108 int error;
4109 unsigned max_links = dir->i_sb->s_max_links;
4110
4111 error = may_create(idmap, dir, dentry);
4112 if (error)
4113 return error;
4114
4115 if (!dir->i_op->mkdir)
4116 return -EPERM;
4117
4118 mode = vfs_prepare_mode(idmap, dir, mode, S_IRWXUGO | S_ISVTX, 0);
4119 error = security_inode_mkdir(dir, dentry, mode);
4120 if (error)
4121 return error;
4122
4123 if (max_links && dir->i_nlink >= max_links)
4124 return -EMLINK;
4125
4126 error = dir->i_op->mkdir(idmap, dir, dentry, mode);
4127 if (!error)
4128 fsnotify_mkdir(dir, dentry);
4129 return error;
4130}
4131EXPORT_SYMBOL(vfs_mkdir);
4132
4133int do_mkdirat(int dfd, struct filename *name, umode_t mode)
4134{
4135 struct dentry *dentry;
4136 struct path path;
4137 int error;
4138 unsigned int lookup_flags = LOOKUP_DIRECTORY;
4139
4140retry:
4141 dentry = filename_create(dfd, name, &path, lookup_flags);
4142 error = PTR_ERR(dentry);
4143 if (IS_ERR(dentry))
4144 goto out_putname;
4145
4146 error = security_path_mkdir(&path, dentry,
4147 mode_strip_umask(path.dentry->d_inode, mode));
4148 if (!error) {
4149 error = vfs_mkdir(mnt_idmap(path.mnt), path.dentry->d_inode,
4150 dentry, mode);
4151 }
4152 done_path_create(&path, dentry);
4153 if (retry_estale(error, lookup_flags)) {
4154 lookup_flags |= LOOKUP_REVAL;
4155 goto retry;
4156 }
4157out_putname:
4158 putname(name);
4159 return error;
4160}
4161
4162SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
4163{
4164 return do_mkdirat(dfd, getname(pathname), mode);
4165}
4166
4167SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode)
4168{
4169 return do_mkdirat(AT_FDCWD, getname(pathname), mode);
4170}
4171
4172/**
4173 * vfs_rmdir - remove directory
4174 * @idmap: idmap of the mount the inode was found from
4175 * @dir: inode of @dentry
4176 * @dentry: pointer to dentry of the base directory
4177 *
4178 * Remove a directory.
4179 *
4180 * If the inode has been found through an idmapped mount the idmap of
4181 * the vfsmount must be passed through @idmap. This function will then take
4182 * care to map the inode according to @idmap before checking permissions.
4183 * On non-idmapped mounts or if permission checking is to be performed on the
4184 * raw inode simply pass @nop_mnt_idmap.
4185 */
4186int vfs_rmdir(struct mnt_idmap *idmap, struct inode *dir,
4187 struct dentry *dentry)
4188{
4189 int error = may_delete(idmap, dir, dentry, 1);
4190
4191 if (error)
4192 return error;
4193
4194 if (!dir->i_op->rmdir)
4195 return -EPERM;
4196
4197 dget(dentry);
4198 inode_lock(dentry->d_inode);
4199
4200 error = -EBUSY;
4201 if (is_local_mountpoint(dentry) ||
4202 (dentry->d_inode->i_flags & S_KERNEL_FILE))
4203 goto out;
4204
4205 error = security_inode_rmdir(dir, dentry);
4206 if (error)
4207 goto out;
4208
4209 error = dir->i_op->rmdir(dir, dentry);
4210 if (error)
4211 goto out;
4212
4213 shrink_dcache_parent(dentry);
4214 dentry->d_inode->i_flags |= S_DEAD;
4215 dont_mount(dentry);
4216 detach_mounts(dentry);
4217
4218out:
4219 inode_unlock(dentry->d_inode);
4220 dput(dentry);
4221 if (!error)
4222 d_delete_notify(dir, dentry);
4223 return error;
4224}
4225EXPORT_SYMBOL(vfs_rmdir);
4226
4227int do_rmdir(int dfd, struct filename *name)
4228{
4229 int error;
4230 struct dentry *dentry;
4231 struct path path;
4232 struct qstr last;
4233 int type;
4234 unsigned int lookup_flags = 0;
4235retry:
4236 error = filename_parentat(dfd, name, lookup_flags, &path, &last, &type);
4237 if (error)
4238 goto exit1;
4239
4240 switch (type) {
4241 case LAST_DOTDOT:
4242 error = -ENOTEMPTY;
4243 goto exit2;
4244 case LAST_DOT:
4245 error = -EINVAL;
4246 goto exit2;
4247 case LAST_ROOT:
4248 error = -EBUSY;
4249 goto exit2;
4250 }
4251
4252 error = mnt_want_write(path.mnt);
4253 if (error)
4254 goto exit2;
4255
4256 inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT);
4257 dentry = lookup_one_qstr_excl(&last, path.dentry, lookup_flags);
4258 error = PTR_ERR(dentry);
4259 if (IS_ERR(dentry))
4260 goto exit3;
4261 if (!dentry->d_inode) {
4262 error = -ENOENT;
4263 goto exit4;
4264 }
4265 error = security_path_rmdir(&path, dentry);
4266 if (error)
4267 goto exit4;
4268 error = vfs_rmdir(mnt_idmap(path.mnt), path.dentry->d_inode, dentry);
4269exit4:
4270 dput(dentry);
4271exit3:
4272 inode_unlock(path.dentry->d_inode);
4273 mnt_drop_write(path.mnt);
4274exit2:
4275 path_put(&path);
4276 if (retry_estale(error, lookup_flags)) {
4277 lookup_flags |= LOOKUP_REVAL;
4278 goto retry;
4279 }
4280exit1:
4281 putname(name);
4282 return error;
4283}
4284
4285SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
4286{
4287 return do_rmdir(AT_FDCWD, getname(pathname));
4288}
4289
4290/**
4291 * vfs_unlink - unlink a filesystem object
4292 * @idmap: idmap of the mount the inode was found from
4293 * @dir: parent directory
4294 * @dentry: victim
4295 * @delegated_inode: returns victim inode, if the inode is delegated.
4296 *
4297 * The caller must hold dir->i_mutex.
4298 *
4299 * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and
4300 * return a reference to the inode in delegated_inode. The caller
4301 * should then break the delegation on that inode and retry. Because
4302 * breaking a delegation may take a long time, the caller should drop
4303 * dir->i_mutex before doing so.
4304 *
4305 * Alternatively, a caller may pass NULL for delegated_inode. This may
4306 * be appropriate for callers that expect the underlying filesystem not
4307 * to be NFS exported.
4308 *
4309 * If the inode has been found through an idmapped mount the idmap of
4310 * the vfsmount must be passed through @idmap. This function will then take
4311 * care to map the inode according to @idmap before checking permissions.
4312 * On non-idmapped mounts or if permission checking is to be performed on the
4313 * raw inode simply pass @nop_mnt_idmap.
4314 */
4315int vfs_unlink(struct mnt_idmap *idmap, struct inode *dir,
4316 struct dentry *dentry, struct inode **delegated_inode)
4317{
4318 struct inode *target = dentry->d_inode;
4319 int error = may_delete(idmap, dir, dentry, 0);
4320
4321 if (error)
4322 return error;
4323
4324 if (!dir->i_op->unlink)
4325 return -EPERM;
4326
4327 inode_lock(target);
4328 if (IS_SWAPFILE(target))
4329 error = -EPERM;
4330 else if (is_local_mountpoint(dentry))
4331 error = -EBUSY;
4332 else {
4333 error = security_inode_unlink(dir, dentry);
4334 if (!error) {
4335 error = try_break_deleg(target, delegated_inode);
4336 if (error)
4337 goto out;
4338 error = dir->i_op->unlink(dir, dentry);
4339 if (!error) {
4340 dont_mount(dentry);
4341 detach_mounts(dentry);
4342 }
4343 }
4344 }
4345out:
4346 inode_unlock(target);
4347
4348 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
4349 if (!error && dentry->d_flags & DCACHE_NFSFS_RENAMED) {
4350 fsnotify_unlink(dir, dentry);
4351 } else if (!error) {
4352 fsnotify_link_count(target);
4353 d_delete_notify(dir, dentry);
4354 }
4355
4356 return error;
4357}
4358EXPORT_SYMBOL(vfs_unlink);
4359
4360/*
4361 * Make sure that the actual truncation of the file will occur outside its
4362 * directory's i_mutex. Truncate can take a long time if there is a lot of
4363 * writeout happening, and we don't want to prevent access to the directory
4364 * while waiting on the I/O.
4365 */
4366int do_unlinkat(int dfd, struct filename *name)
4367{
4368 int error;
4369 struct dentry *dentry;
4370 struct path path;
4371 struct qstr last;
4372 int type;
4373 struct inode *inode = NULL;
4374 struct inode *delegated_inode = NULL;
4375 unsigned int lookup_flags = 0;
4376retry:
4377 error = filename_parentat(dfd, name, lookup_flags, &path, &last, &type);
4378 if (error)
4379 goto exit1;
4380
4381 error = -EISDIR;
4382 if (type != LAST_NORM)
4383 goto exit2;
4384
4385 error = mnt_want_write(path.mnt);
4386 if (error)
4387 goto exit2;
4388retry_deleg:
4389 inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT);
4390 dentry = lookup_one_qstr_excl(&last, path.dentry, lookup_flags);
4391 error = PTR_ERR(dentry);
4392 if (!IS_ERR(dentry)) {
4393
4394 /* Why not before? Because we want correct error value */
4395 if (last.name[last.len] || d_is_negative(dentry))
4396 goto slashes;
4397 inode = dentry->d_inode;
4398 ihold(inode);
4399 error = security_path_unlink(&path, dentry);
4400 if (error)
4401 goto exit3;
4402 error = vfs_unlink(mnt_idmap(path.mnt), path.dentry->d_inode,
4403 dentry, &delegated_inode);
4404exit3:
4405 dput(dentry);
4406 }
4407 inode_unlock(path.dentry->d_inode);
4408 if (inode)
4409 iput(inode); /* truncate the inode here */
4410 inode = NULL;
4411 if (delegated_inode) {
4412 error = break_deleg_wait(&delegated_inode);
4413 if (!error)
4414 goto retry_deleg;
4415 }
4416 mnt_drop_write(path.mnt);
4417exit2:
4418 path_put(&path);
4419 if (retry_estale(error, lookup_flags)) {
4420 lookup_flags |= LOOKUP_REVAL;
4421 inode = NULL;
4422 goto retry;
4423 }
4424exit1:
4425 putname(name);
4426 return error;
4427
4428slashes:
4429 if (d_is_negative(dentry))
4430 error = -ENOENT;
4431 else if (d_is_dir(dentry))
4432 error = -EISDIR;
4433 else
4434 error = -ENOTDIR;
4435 goto exit3;
4436}
4437
4438SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
4439{
4440 if ((flag & ~AT_REMOVEDIR) != 0)
4441 return -EINVAL;
4442
4443 if (flag & AT_REMOVEDIR)
4444 return do_rmdir(dfd, getname(pathname));
4445 return do_unlinkat(dfd, getname(pathname));
4446}
4447
4448SYSCALL_DEFINE1(unlink, const char __user *, pathname)
4449{
4450 return do_unlinkat(AT_FDCWD, getname(pathname));
4451}
4452
4453/**
4454 * vfs_symlink - create symlink
4455 * @idmap: idmap of the mount the inode was found from
4456 * @dir: inode of @dentry
4457 * @dentry: pointer to dentry of the base directory
4458 * @oldname: name of the file to link to
4459 *
4460 * Create a symlink.
4461 *
4462 * If the inode has been found through an idmapped mount the idmap of
4463 * the vfsmount must be passed through @idmap. This function will then take
4464 * care to map the inode according to @idmap before checking permissions.
4465 * On non-idmapped mounts or if permission checking is to be performed on the
4466 * raw inode simply pass @nop_mnt_idmap.
4467 */
4468int vfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
4469 struct dentry *dentry, const char *oldname)
4470{
4471 int error;
4472
4473 error = may_create(idmap, dir, dentry);
4474 if (error)
4475 return error;
4476
4477 if (!dir->i_op->symlink)
4478 return -EPERM;
4479
4480 error = security_inode_symlink(dir, dentry, oldname);
4481 if (error)
4482 return error;
4483
4484 error = dir->i_op->symlink(idmap, dir, dentry, oldname);
4485 if (!error)
4486 fsnotify_create(dir, dentry);
4487 return error;
4488}
4489EXPORT_SYMBOL(vfs_symlink);
4490
4491int do_symlinkat(struct filename *from, int newdfd, struct filename *to)
4492{
4493 int error;
4494 struct dentry *dentry;
4495 struct path path;
4496 unsigned int lookup_flags = 0;
4497
4498 if (IS_ERR(from)) {
4499 error = PTR_ERR(from);
4500 goto out_putnames;
4501 }
4502retry:
4503 dentry = filename_create(newdfd, to, &path, lookup_flags);
4504 error = PTR_ERR(dentry);
4505 if (IS_ERR(dentry))
4506 goto out_putnames;
4507
4508 error = security_path_symlink(&path, dentry, from->name);
4509 if (!error)
4510 error = vfs_symlink(mnt_idmap(path.mnt), path.dentry->d_inode,
4511 dentry, from->name);
4512 done_path_create(&path, dentry);
4513 if (retry_estale(error, lookup_flags)) {
4514 lookup_flags |= LOOKUP_REVAL;
4515 goto retry;
4516 }
4517out_putnames:
4518 putname(to);
4519 putname(from);
4520 return error;
4521}
4522
4523SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
4524 int, newdfd, const char __user *, newname)
4525{
4526 return do_symlinkat(getname(oldname), newdfd, getname(newname));
4527}
4528
4529SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
4530{
4531 return do_symlinkat(getname(oldname), AT_FDCWD, getname(newname));
4532}
4533
4534/**
4535 * vfs_link - create a new link
4536 * @old_dentry: object to be linked
4537 * @idmap: idmap of the mount
4538 * @dir: new parent
4539 * @new_dentry: where to create the new link
4540 * @delegated_inode: returns inode needing a delegation break
4541 *
4542 * The caller must hold dir->i_mutex
4543 *
4544 * If vfs_link discovers a delegation on the to-be-linked file in need
4545 * of breaking, it will return -EWOULDBLOCK and return a reference to the
4546 * inode in delegated_inode. The caller should then break the delegation
4547 * and retry. Because breaking a delegation may take a long time, the
4548 * caller should drop the i_mutex before doing so.
4549 *
4550 * Alternatively, a caller may pass NULL for delegated_inode. This may
4551 * be appropriate for callers that expect the underlying filesystem not
4552 * to be NFS exported.
4553 *
4554 * If the inode has been found through an idmapped mount the idmap of
4555 * the vfsmount must be passed through @idmap. This function will then take
4556 * care to map the inode according to @idmap before checking permissions.
4557 * On non-idmapped mounts or if permission checking is to be performed on the
4558 * raw inode simply pass @nop_mnt_idmap.
4559 */
4560int vfs_link(struct dentry *old_dentry, struct mnt_idmap *idmap,
4561 struct inode *dir, struct dentry *new_dentry,
4562 struct inode **delegated_inode)
4563{
4564 struct inode *inode = old_dentry->d_inode;
4565 unsigned max_links = dir->i_sb->s_max_links;
4566 int error;
4567
4568 if (!inode)
4569 return -ENOENT;
4570
4571 error = may_create(idmap, dir, new_dentry);
4572 if (error)
4573 return error;
4574
4575 if (dir->i_sb != inode->i_sb)
4576 return -EXDEV;
4577
4578 /*
4579 * A link to an append-only or immutable file cannot be created.
4580 */
4581 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
4582 return -EPERM;
4583 /*
4584 * Updating the link count will likely cause i_uid and i_gid to
4585 * be writen back improperly if their true value is unknown to
4586 * the vfs.
4587 */
4588 if (HAS_UNMAPPED_ID(idmap, inode))
4589 return -EPERM;
4590 if (!dir->i_op->link)
4591 return -EPERM;
4592 if (S_ISDIR(inode->i_mode))
4593 return -EPERM;
4594
4595 error = security_inode_link(old_dentry, dir, new_dentry);
4596 if (error)
4597 return error;
4598
4599 inode_lock(inode);
4600 /* Make sure we don't allow creating hardlink to an unlinked file */
4601 if (inode->i_nlink == 0 && !(inode->i_state & I_LINKABLE))
4602 error = -ENOENT;
4603 else if (max_links && inode->i_nlink >= max_links)
4604 error = -EMLINK;
4605 else {
4606 error = try_break_deleg(inode, delegated_inode);
4607 if (!error)
4608 error = dir->i_op->link(old_dentry, dir, new_dentry);
4609 }
4610
4611 if (!error && (inode->i_state & I_LINKABLE)) {
4612 spin_lock(&inode->i_lock);
4613 inode->i_state &= ~I_LINKABLE;
4614 spin_unlock(&inode->i_lock);
4615 }
4616 inode_unlock(inode);
4617 if (!error)
4618 fsnotify_link(dir, inode, new_dentry);
4619 return error;
4620}
4621EXPORT_SYMBOL(vfs_link);
4622
4623/*
4624 * Hardlinks are often used in delicate situations. We avoid
4625 * security-related surprises by not following symlinks on the
4626 * newname. --KAB
4627 *
4628 * We don't follow them on the oldname either to be compatible
4629 * with linux 2.0, and to avoid hard-linking to directories
4630 * and other special files. --ADM
4631 */
4632int do_linkat(int olddfd, struct filename *old, int newdfd,
4633 struct filename *new, int flags)
4634{
4635 struct mnt_idmap *idmap;
4636 struct dentry *new_dentry;
4637 struct path old_path, new_path;
4638 struct inode *delegated_inode = NULL;
4639 int how = 0;
4640 int error;
4641
4642 if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0) {
4643 error = -EINVAL;
4644 goto out_putnames;
4645 }
4646 /*
4647 * To use null names we require CAP_DAC_READ_SEARCH
4648 * This ensures that not everyone will be able to create
4649 * handlink using the passed filedescriptor.
4650 */
4651 if (flags & AT_EMPTY_PATH && !capable(CAP_DAC_READ_SEARCH)) {
4652 error = -ENOENT;
4653 goto out_putnames;
4654 }
4655
4656 if (flags & AT_SYMLINK_FOLLOW)
4657 how |= LOOKUP_FOLLOW;
4658retry:
4659 error = filename_lookup(olddfd, old, how, &old_path, NULL);
4660 if (error)
4661 goto out_putnames;
4662
4663 new_dentry = filename_create(newdfd, new, &new_path,
4664 (how & LOOKUP_REVAL));
4665 error = PTR_ERR(new_dentry);
4666 if (IS_ERR(new_dentry))
4667 goto out_putpath;
4668
4669 error = -EXDEV;
4670 if (old_path.mnt != new_path.mnt)
4671 goto out_dput;
4672 idmap = mnt_idmap(new_path.mnt);
4673 error = may_linkat(idmap, &old_path);
4674 if (unlikely(error))
4675 goto out_dput;
4676 error = security_path_link(old_path.dentry, &new_path, new_dentry);
4677 if (error)
4678 goto out_dput;
4679 error = vfs_link(old_path.dentry, idmap, new_path.dentry->d_inode,
4680 new_dentry, &delegated_inode);
4681out_dput:
4682 done_path_create(&new_path, new_dentry);
4683 if (delegated_inode) {
4684 error = break_deleg_wait(&delegated_inode);
4685 if (!error) {
4686 path_put(&old_path);
4687 goto retry;
4688 }
4689 }
4690 if (retry_estale(error, how)) {
4691 path_put(&old_path);
4692 how |= LOOKUP_REVAL;
4693 goto retry;
4694 }
4695out_putpath:
4696 path_put(&old_path);
4697out_putnames:
4698 putname(old);
4699 putname(new);
4700
4701 return error;
4702}
4703
4704SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
4705 int, newdfd, const char __user *, newname, int, flags)
4706{
4707 return do_linkat(olddfd, getname_uflags(oldname, flags),
4708 newdfd, getname(newname), flags);
4709}
4710
4711SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
4712{
4713 return do_linkat(AT_FDCWD, getname(oldname), AT_FDCWD, getname(newname), 0);
4714}
4715
4716/**
4717 * vfs_rename - rename a filesystem object
4718 * @rd: pointer to &struct renamedata info
4719 *
4720 * The caller must hold multiple mutexes--see lock_rename()).
4721 *
4722 * If vfs_rename discovers a delegation in need of breaking at either
4723 * the source or destination, it will return -EWOULDBLOCK and return a
4724 * reference to the inode in delegated_inode. The caller should then
4725 * break the delegation and retry. Because breaking a delegation may
4726 * take a long time, the caller should drop all locks before doing
4727 * so.
4728 *
4729 * Alternatively, a caller may pass NULL for delegated_inode. This may
4730 * be appropriate for callers that expect the underlying filesystem not
4731 * to be NFS exported.
4732 *
4733 * The worst of all namespace operations - renaming directory. "Perverted"
4734 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
4735 * Problems:
4736 *
4737 * a) we can get into loop creation.
4738 * b) race potential - two innocent renames can create a loop together.
4739 * That's where 4.4BSD screws up. Current fix: serialization on
4740 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
4741 * story.
4742 * c) we may have to lock up to _four_ objects - parents and victim (if it exists),
4743 * and source (if it's a non-directory or a subdirectory that moves to
4744 * different parent).
4745 * And that - after we got ->i_mutex on parents (until then we don't know
4746 * whether the target exists). Solution: try to be smart with locking
4747 * order for inodes. We rely on the fact that tree topology may change
4748 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
4749 * move will be locked. Thus we can rank directories by the tree
4750 * (ancestors first) and rank all non-directories after them.
4751 * That works since everybody except rename does "lock parent, lookup,
4752 * lock child" and rename is under ->s_vfs_rename_mutex.
4753 * HOWEVER, it relies on the assumption that any object with ->lookup()
4754 * has no more than 1 dentry. If "hybrid" objects will ever appear,
4755 * we'd better make sure that there's no link(2) for them.
4756 * d) conversion from fhandle to dentry may come in the wrong moment - when
4757 * we are removing the target. Solution: we will have to grab ->i_mutex
4758 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
4759 * ->i_mutex on parents, which works but leads to some truly excessive
4760 * locking].
4761 */
4762int vfs_rename(struct renamedata *rd)
4763{
4764 int error;
4765 struct inode *old_dir = rd->old_dir, *new_dir = rd->new_dir;
4766 struct dentry *old_dentry = rd->old_dentry;
4767 struct dentry *new_dentry = rd->new_dentry;
4768 struct inode **delegated_inode = rd->delegated_inode;
4769 unsigned int flags = rd->flags;
4770 bool is_dir = d_is_dir(old_dentry);
4771 struct inode *source = old_dentry->d_inode;
4772 struct inode *target = new_dentry->d_inode;
4773 bool new_is_dir = false;
4774 unsigned max_links = new_dir->i_sb->s_max_links;
4775 struct name_snapshot old_name;
4776 bool lock_old_subdir, lock_new_subdir;
4777
4778 if (source == target)
4779 return 0;
4780
4781 error = may_delete(rd->old_mnt_idmap, old_dir, old_dentry, is_dir);
4782 if (error)
4783 return error;
4784
4785 if (!target) {
4786 error = may_create(rd->new_mnt_idmap, new_dir, new_dentry);
4787 } else {
4788 new_is_dir = d_is_dir(new_dentry);
4789
4790 if (!(flags & RENAME_EXCHANGE))
4791 error = may_delete(rd->new_mnt_idmap, new_dir,
4792 new_dentry, is_dir);
4793 else
4794 error = may_delete(rd->new_mnt_idmap, new_dir,
4795 new_dentry, new_is_dir);
4796 }
4797 if (error)
4798 return error;
4799
4800 if (!old_dir->i_op->rename)
4801 return -EPERM;
4802
4803 /*
4804 * If we are going to change the parent - check write permissions,
4805 * we'll need to flip '..'.
4806 */
4807 if (new_dir != old_dir) {
4808 if (is_dir) {
4809 error = inode_permission(rd->old_mnt_idmap, source,
4810 MAY_WRITE);
4811 if (error)
4812 return error;
4813 }
4814 if ((flags & RENAME_EXCHANGE) && new_is_dir) {
4815 error = inode_permission(rd->new_mnt_idmap, target,
4816 MAY_WRITE);
4817 if (error)
4818 return error;
4819 }
4820 }
4821
4822 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry,
4823 flags);
4824 if (error)
4825 return error;
4826
4827 take_dentry_name_snapshot(&old_name, old_dentry);
4828 dget(new_dentry);
4829 /*
4830 * Lock children.
4831 * The source subdirectory needs to be locked on cross-directory
4832 * rename or cross-directory exchange since its parent changes.
4833 * The target subdirectory needs to be locked on cross-directory
4834 * exchange due to parent change and on any rename due to becoming
4835 * a victim.
4836 * Non-directories need locking in all cases (for NFS reasons);
4837 * they get locked after any subdirectories (in inode address order).
4838 *
4839 * NOTE: WE ONLY LOCK UNRELATED DIRECTORIES IN CROSS-DIRECTORY CASE.
4840 * NEVER, EVER DO THAT WITHOUT ->s_vfs_rename_mutex.
4841 */
4842 lock_old_subdir = new_dir != old_dir;
4843 lock_new_subdir = new_dir != old_dir || !(flags & RENAME_EXCHANGE);
4844 if (is_dir) {
4845 if (lock_old_subdir)
4846 inode_lock_nested(source, I_MUTEX_CHILD);
4847 if (target && (!new_is_dir || lock_new_subdir))
4848 inode_lock(target);
4849 } else if (new_is_dir) {
4850 if (lock_new_subdir)
4851 inode_lock_nested(target, I_MUTEX_CHILD);
4852 inode_lock(source);
4853 } else {
4854 lock_two_nondirectories(source, target);
4855 }
4856
4857 error = -EPERM;
4858 if (IS_SWAPFILE(source) || (target && IS_SWAPFILE(target)))
4859 goto out;
4860
4861 error = -EBUSY;
4862 if (is_local_mountpoint(old_dentry) || is_local_mountpoint(new_dentry))
4863 goto out;
4864
4865 if (max_links && new_dir != old_dir) {
4866 error = -EMLINK;
4867 if (is_dir && !new_is_dir && new_dir->i_nlink >= max_links)
4868 goto out;
4869 if ((flags & RENAME_EXCHANGE) && !is_dir && new_is_dir &&
4870 old_dir->i_nlink >= max_links)
4871 goto out;
4872 }
4873 if (!is_dir) {
4874 error = try_break_deleg(source, delegated_inode);
4875 if (error)
4876 goto out;
4877 }
4878 if (target && !new_is_dir) {
4879 error = try_break_deleg(target, delegated_inode);
4880 if (error)
4881 goto out;
4882 }
4883 error = old_dir->i_op->rename(rd->new_mnt_idmap, old_dir, old_dentry,
4884 new_dir, new_dentry, flags);
4885 if (error)
4886 goto out;
4887
4888 if (!(flags & RENAME_EXCHANGE) && target) {
4889 if (is_dir) {
4890 shrink_dcache_parent(new_dentry);
4891 target->i_flags |= S_DEAD;
4892 }
4893 dont_mount(new_dentry);
4894 detach_mounts(new_dentry);
4895 }
4896 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) {
4897 if (!(flags & RENAME_EXCHANGE))
4898 d_move(old_dentry, new_dentry);
4899 else
4900 d_exchange(old_dentry, new_dentry);
4901 }
4902out:
4903 if (!is_dir || lock_old_subdir)
4904 inode_unlock(source);
4905 if (target && (!new_is_dir || lock_new_subdir))
4906 inode_unlock(target);
4907 dput(new_dentry);
4908 if (!error) {
4909 fsnotify_move(old_dir, new_dir, &old_name.name, is_dir,
4910 !(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry);
4911 if (flags & RENAME_EXCHANGE) {
4912 fsnotify_move(new_dir, old_dir, &old_dentry->d_name,
4913 new_is_dir, NULL, new_dentry);
4914 }
4915 }
4916 release_dentry_name_snapshot(&old_name);
4917
4918 return error;
4919}
4920EXPORT_SYMBOL(vfs_rename);
4921
4922int do_renameat2(int olddfd, struct filename *from, int newdfd,
4923 struct filename *to, unsigned int flags)
4924{
4925 struct renamedata rd;
4926 struct dentry *old_dentry, *new_dentry;
4927 struct dentry *trap;
4928 struct path old_path, new_path;
4929 struct qstr old_last, new_last;
4930 int old_type, new_type;
4931 struct inode *delegated_inode = NULL;
4932 unsigned int lookup_flags = 0, target_flags = LOOKUP_RENAME_TARGET;
4933 bool should_retry = false;
4934 int error = -EINVAL;
4935
4936 if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
4937 goto put_names;
4938
4939 if ((flags & (RENAME_NOREPLACE | RENAME_WHITEOUT)) &&
4940 (flags & RENAME_EXCHANGE))
4941 goto put_names;
4942
4943 if (flags & RENAME_EXCHANGE)
4944 target_flags = 0;
4945
4946retry:
4947 error = filename_parentat(olddfd, from, lookup_flags, &old_path,
4948 &old_last, &old_type);
4949 if (error)
4950 goto put_names;
4951
4952 error = filename_parentat(newdfd, to, lookup_flags, &new_path, &new_last,
4953 &new_type);
4954 if (error)
4955 goto exit1;
4956
4957 error = -EXDEV;
4958 if (old_path.mnt != new_path.mnt)
4959 goto exit2;
4960
4961 error = -EBUSY;
4962 if (old_type != LAST_NORM)
4963 goto exit2;
4964
4965 if (flags & RENAME_NOREPLACE)
4966 error = -EEXIST;
4967 if (new_type != LAST_NORM)
4968 goto exit2;
4969
4970 error = mnt_want_write(old_path.mnt);
4971 if (error)
4972 goto exit2;
4973
4974retry_deleg:
4975 trap = lock_rename(new_path.dentry, old_path.dentry);
4976 if (IS_ERR(trap)) {
4977 error = PTR_ERR(trap);
4978 goto exit_lock_rename;
4979 }
4980
4981 old_dentry = lookup_one_qstr_excl(&old_last, old_path.dentry,
4982 lookup_flags);
4983 error = PTR_ERR(old_dentry);
4984 if (IS_ERR(old_dentry))
4985 goto exit3;
4986 /* source must exist */
4987 error = -ENOENT;
4988 if (d_is_negative(old_dentry))
4989 goto exit4;
4990 new_dentry = lookup_one_qstr_excl(&new_last, new_path.dentry,
4991 lookup_flags | target_flags);
4992 error = PTR_ERR(new_dentry);
4993 if (IS_ERR(new_dentry))
4994 goto exit4;
4995 error = -EEXIST;
4996 if ((flags & RENAME_NOREPLACE) && d_is_positive(new_dentry))
4997 goto exit5;
4998 if (flags & RENAME_EXCHANGE) {
4999 error = -ENOENT;
5000 if (d_is_negative(new_dentry))
5001 goto exit5;
5002
5003 if (!d_is_dir(new_dentry)) {
5004 error = -ENOTDIR;
5005 if (new_last.name[new_last.len])
5006 goto exit5;
5007 }
5008 }
5009 /* unless the source is a directory trailing slashes give -ENOTDIR */
5010 if (!d_is_dir(old_dentry)) {
5011 error = -ENOTDIR;
5012 if (old_last.name[old_last.len])
5013 goto exit5;
5014 if (!(flags & RENAME_EXCHANGE) && new_last.name[new_last.len])
5015 goto exit5;
5016 }
5017 /* source should not be ancestor of target */
5018 error = -EINVAL;
5019 if (old_dentry == trap)
5020 goto exit5;
5021 /* target should not be an ancestor of source */
5022 if (!(flags & RENAME_EXCHANGE))
5023 error = -ENOTEMPTY;
5024 if (new_dentry == trap)
5025 goto exit5;
5026
5027 error = security_path_rename(&old_path, old_dentry,
5028 &new_path, new_dentry, flags);
5029 if (error)
5030 goto exit5;
5031
5032 rd.old_dir = old_path.dentry->d_inode;
5033 rd.old_dentry = old_dentry;
5034 rd.old_mnt_idmap = mnt_idmap(old_path.mnt);
5035 rd.new_dir = new_path.dentry->d_inode;
5036 rd.new_dentry = new_dentry;
5037 rd.new_mnt_idmap = mnt_idmap(new_path.mnt);
5038 rd.delegated_inode = &delegated_inode;
5039 rd.flags = flags;
5040 error = vfs_rename(&rd);
5041exit5:
5042 dput(new_dentry);
5043exit4:
5044 dput(old_dentry);
5045exit3:
5046 unlock_rename(new_path.dentry, old_path.dentry);
5047exit_lock_rename:
5048 if (delegated_inode) {
5049 error = break_deleg_wait(&delegated_inode);
5050 if (!error)
5051 goto retry_deleg;
5052 }
5053 mnt_drop_write(old_path.mnt);
5054exit2:
5055 if (retry_estale(error, lookup_flags))
5056 should_retry = true;
5057 path_put(&new_path);
5058exit1:
5059 path_put(&old_path);
5060 if (should_retry) {
5061 should_retry = false;
5062 lookup_flags |= LOOKUP_REVAL;
5063 goto retry;
5064 }
5065put_names:
5066 putname(from);
5067 putname(to);
5068 return error;
5069}
5070
5071SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname,
5072 int, newdfd, const char __user *, newname, unsigned int, flags)
5073{
5074 return do_renameat2(olddfd, getname(oldname), newdfd, getname(newname),
5075 flags);
5076}
5077
5078SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
5079 int, newdfd, const char __user *, newname)
5080{
5081 return do_renameat2(olddfd, getname(oldname), newdfd, getname(newname),
5082 0);
5083}
5084
5085SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
5086{
5087 return do_renameat2(AT_FDCWD, getname(oldname), AT_FDCWD,
5088 getname(newname), 0);
5089}
5090
5091int readlink_copy(char __user *buffer, int buflen, const char *link)
5092{
5093 int len = PTR_ERR(link);
5094 if (IS_ERR(link))
5095 goto out;
5096
5097 len = strlen(link);
5098 if (len > (unsigned) buflen)
5099 len = buflen;
5100 if (copy_to_user(buffer, link, len))
5101 len = -EFAULT;
5102out:
5103 return len;
5104}
5105
5106/**
5107 * vfs_readlink - copy symlink body into userspace buffer
5108 * @dentry: dentry on which to get symbolic link
5109 * @buffer: user memory pointer
5110 * @buflen: size of buffer
5111 *
5112 * Does not touch atime. That's up to the caller if necessary
5113 *
5114 * Does not call security hook.
5115 */
5116int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen)
5117{
5118 struct inode *inode = d_inode(dentry);
5119 DEFINE_DELAYED_CALL(done);
5120 const char *link;
5121 int res;
5122
5123 if (unlikely(!(inode->i_opflags & IOP_DEFAULT_READLINK))) {
5124 if (unlikely(inode->i_op->readlink))
5125 return inode->i_op->readlink(dentry, buffer, buflen);
5126
5127 if (!d_is_symlink(dentry))
5128 return -EINVAL;
5129
5130 spin_lock(&inode->i_lock);
5131 inode->i_opflags |= IOP_DEFAULT_READLINK;
5132 spin_unlock(&inode->i_lock);
5133 }
5134
5135 link = READ_ONCE(inode->i_link);
5136 if (!link) {
5137 link = inode->i_op->get_link(dentry, inode, &done);
5138 if (IS_ERR(link))
5139 return PTR_ERR(link);
5140 }
5141 res = readlink_copy(buffer, buflen, link);
5142 do_delayed_call(&done);
5143 return res;
5144}
5145EXPORT_SYMBOL(vfs_readlink);
5146
5147/**
5148 * vfs_get_link - get symlink body
5149 * @dentry: dentry on which to get symbolic link
5150 * @done: caller needs to free returned data with this
5151 *
5152 * Calls security hook and i_op->get_link() on the supplied inode.
5153 *
5154 * It does not touch atime. That's up to the caller if necessary.
5155 *
5156 * Does not work on "special" symlinks like /proc/$$/fd/N
5157 */
5158const char *vfs_get_link(struct dentry *dentry, struct delayed_call *done)
5159{
5160 const char *res = ERR_PTR(-EINVAL);
5161 struct inode *inode = d_inode(dentry);
5162
5163 if (d_is_symlink(dentry)) {
5164 res = ERR_PTR(security_inode_readlink(dentry));
5165 if (!res)
5166 res = inode->i_op->get_link(dentry, inode, done);
5167 }
5168 return res;
5169}
5170EXPORT_SYMBOL(vfs_get_link);
5171
5172/* get the link contents into pagecache */
5173const char *page_get_link(struct dentry *dentry, struct inode *inode,
5174 struct delayed_call *callback)
5175{
5176 char *kaddr;
5177 struct page *page;
5178 struct address_space *mapping = inode->i_mapping;
5179
5180 if (!dentry) {
5181 page = find_get_page(mapping, 0);
5182 if (!page)
5183 return ERR_PTR(-ECHILD);
5184 if (!PageUptodate(page)) {
5185 put_page(page);
5186 return ERR_PTR(-ECHILD);
5187 }
5188 } else {
5189 page = read_mapping_page(mapping, 0, NULL);
5190 if (IS_ERR(page))
5191 return (char*)page;
5192 }
5193 set_delayed_call(callback, page_put_link, page);
5194 BUG_ON(mapping_gfp_mask(mapping) & __GFP_HIGHMEM);
5195 kaddr = page_address(page);
5196 nd_terminate_link(kaddr, inode->i_size, PAGE_SIZE - 1);
5197 return kaddr;
5198}
5199
5200EXPORT_SYMBOL(page_get_link);
5201
5202void page_put_link(void *arg)
5203{
5204 put_page(arg);
5205}
5206EXPORT_SYMBOL(page_put_link);
5207
5208int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
5209{
5210 DEFINE_DELAYED_CALL(done);
5211 int res = readlink_copy(buffer, buflen,
5212 page_get_link(dentry, d_inode(dentry),
5213 &done));
5214 do_delayed_call(&done);
5215 return res;
5216}
5217EXPORT_SYMBOL(page_readlink);
5218
5219int page_symlink(struct inode *inode, const char *symname, int len)
5220{
5221 struct address_space *mapping = inode->i_mapping;
5222 const struct address_space_operations *aops = mapping->a_ops;
5223 bool nofs = !mapping_gfp_constraint(mapping, __GFP_FS);
5224 struct page *page;
5225 void *fsdata = NULL;
5226 int err;
5227 unsigned int flags;
5228
5229retry:
5230 if (nofs)
5231 flags = memalloc_nofs_save();
5232 err = aops->write_begin(NULL, mapping, 0, len-1, &page, &fsdata);
5233 if (nofs)
5234 memalloc_nofs_restore(flags);
5235 if (err)
5236 goto fail;
5237
5238 memcpy(page_address(page), symname, len-1);
5239
5240 err = aops->write_end(NULL, mapping, 0, len-1, len-1,
5241 page, fsdata);
5242 if (err < 0)
5243 goto fail;
5244 if (err < len-1)
5245 goto retry;
5246
5247 mark_inode_dirty(inode);
5248 return 0;
5249fail:
5250 return err;
5251}
5252EXPORT_SYMBOL(page_symlink);
5253
5254const struct inode_operations page_symlink_inode_operations = {
5255 .get_link = page_get_link,
5256};
5257EXPORT_SYMBOL(page_symlink_inode_operations);
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/fs/namei.c
4 *
5 * Copyright (C) 1991, 1992 Linus Torvalds
6 */
7
8/*
9 * Some corrections by tytso.
10 */
11
12/* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
13 * lookup logic.
14 */
15/* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.
16 */
17
18#include <linux/init.h>
19#include <linux/export.h>
20#include <linux/kernel.h>
21#include <linux/slab.h>
22#include <linux/fs.h>
23#include <linux/namei.h>
24#include <linux/pagemap.h>
25#include <linux/sched/mm.h>
26#include <linux/fsnotify.h>
27#include <linux/personality.h>
28#include <linux/security.h>
29#include <linux/ima.h>
30#include <linux/syscalls.h>
31#include <linux/mount.h>
32#include <linux/audit.h>
33#include <linux/capability.h>
34#include <linux/file.h>
35#include <linux/fcntl.h>
36#include <linux/device_cgroup.h>
37#include <linux/fs_struct.h>
38#include <linux/posix_acl.h>
39#include <linux/hash.h>
40#include <linux/bitops.h>
41#include <linux/init_task.h>
42#include <linux/uaccess.h>
43
44#include "internal.h"
45#include "mount.h"
46
47/* [Feb-1997 T. Schoebel-Theuer]
48 * Fundamental changes in the pathname lookup mechanisms (namei)
49 * were necessary because of omirr. The reason is that omirr needs
50 * to know the _real_ pathname, not the user-supplied one, in case
51 * of symlinks (and also when transname replacements occur).
52 *
53 * The new code replaces the old recursive symlink resolution with
54 * an iterative one (in case of non-nested symlink chains). It does
55 * this with calls to <fs>_follow_link().
56 * As a side effect, dir_namei(), _namei() and follow_link() are now
57 * replaced with a single function lookup_dentry() that can handle all
58 * the special cases of the former code.
59 *
60 * With the new dcache, the pathname is stored at each inode, at least as
61 * long as the refcount of the inode is positive. As a side effect, the
62 * size of the dcache depends on the inode cache and thus is dynamic.
63 *
64 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
65 * resolution to correspond with current state of the code.
66 *
67 * Note that the symlink resolution is not *completely* iterative.
68 * There is still a significant amount of tail- and mid- recursion in
69 * the algorithm. Also, note that <fs>_readlink() is not used in
70 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
71 * may return different results than <fs>_follow_link(). Many virtual
72 * filesystems (including /proc) exhibit this behavior.
73 */
74
75/* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
76 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
77 * and the name already exists in form of a symlink, try to create the new
78 * name indicated by the symlink. The old code always complained that the
79 * name already exists, due to not following the symlink even if its target
80 * is nonexistent. The new semantics affects also mknod() and link() when
81 * the name is a symlink pointing to a non-existent name.
82 *
83 * I don't know which semantics is the right one, since I have no access
84 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
85 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
86 * "old" one. Personally, I think the new semantics is much more logical.
87 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
88 * file does succeed in both HP-UX and SunOs, but not in Solaris
89 * and in the old Linux semantics.
90 */
91
92/* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
93 * semantics. See the comments in "open_namei" and "do_link" below.
94 *
95 * [10-Sep-98 Alan Modra] Another symlink change.
96 */
97
98/* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
99 * inside the path - always follow.
100 * in the last component in creation/removal/renaming - never follow.
101 * if LOOKUP_FOLLOW passed - follow.
102 * if the pathname has trailing slashes - follow.
103 * otherwise - don't follow.
104 * (applied in that order).
105 *
106 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
107 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
108 * During the 2.4 we need to fix the userland stuff depending on it -
109 * hopefully we will be able to get rid of that wart in 2.5. So far only
110 * XEmacs seems to be relying on it...
111 */
112/*
113 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
114 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
115 * any extra contention...
116 */
117
118/* In order to reduce some races, while at the same time doing additional
119 * checking and hopefully speeding things up, we copy filenames to the
120 * kernel data space before using them..
121 *
122 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
123 * PATH_MAX includes the nul terminator --RR.
124 */
125
126#define EMBEDDED_NAME_MAX (PATH_MAX - offsetof(struct filename, iname))
127
128struct filename *
129getname_flags(const char __user *filename, int flags, int *empty)
130{
131 struct filename *result;
132 char *kname;
133 int len;
134
135 result = audit_reusename(filename);
136 if (result)
137 return result;
138
139 result = __getname();
140 if (unlikely(!result))
141 return ERR_PTR(-ENOMEM);
142
143 /*
144 * First, try to embed the struct filename inside the names_cache
145 * allocation
146 */
147 kname = (char *)result->iname;
148 result->name = kname;
149
150 len = strncpy_from_user(kname, filename, EMBEDDED_NAME_MAX);
151 if (unlikely(len < 0)) {
152 __putname(result);
153 return ERR_PTR(len);
154 }
155
156 /*
157 * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a
158 * separate struct filename so we can dedicate the entire
159 * names_cache allocation for the pathname, and re-do the copy from
160 * userland.
161 */
162 if (unlikely(len == EMBEDDED_NAME_MAX)) {
163 const size_t size = offsetof(struct filename, iname[1]);
164 kname = (char *)result;
165
166 /*
167 * size is chosen that way we to guarantee that
168 * result->iname[0] is within the same object and that
169 * kname can't be equal to result->iname, no matter what.
170 */
171 result = kzalloc(size, GFP_KERNEL);
172 if (unlikely(!result)) {
173 __putname(kname);
174 return ERR_PTR(-ENOMEM);
175 }
176 result->name = kname;
177 len = strncpy_from_user(kname, filename, PATH_MAX);
178 if (unlikely(len < 0)) {
179 __putname(kname);
180 kfree(result);
181 return ERR_PTR(len);
182 }
183 if (unlikely(len == PATH_MAX)) {
184 __putname(kname);
185 kfree(result);
186 return ERR_PTR(-ENAMETOOLONG);
187 }
188 }
189
190 result->refcnt = 1;
191 /* The empty path is special. */
192 if (unlikely(!len)) {
193 if (empty)
194 *empty = 1;
195 if (!(flags & LOOKUP_EMPTY)) {
196 putname(result);
197 return ERR_PTR(-ENOENT);
198 }
199 }
200
201 result->uptr = filename;
202 result->aname = NULL;
203 audit_getname(result);
204 return result;
205}
206
207struct filename *
208getname_uflags(const char __user *filename, int uflags)
209{
210 int flags = (uflags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
211
212 return getname_flags(filename, flags, NULL);
213}
214
215struct filename *
216getname(const char __user * filename)
217{
218 return getname_flags(filename, 0, NULL);
219}
220
221struct filename *
222getname_kernel(const char * filename)
223{
224 struct filename *result;
225 int len = strlen(filename) + 1;
226
227 result = __getname();
228 if (unlikely(!result))
229 return ERR_PTR(-ENOMEM);
230
231 if (len <= EMBEDDED_NAME_MAX) {
232 result->name = (char *)result->iname;
233 } else if (len <= PATH_MAX) {
234 const size_t size = offsetof(struct filename, iname[1]);
235 struct filename *tmp;
236
237 tmp = kmalloc(size, GFP_KERNEL);
238 if (unlikely(!tmp)) {
239 __putname(result);
240 return ERR_PTR(-ENOMEM);
241 }
242 tmp->name = (char *)result;
243 result = tmp;
244 } else {
245 __putname(result);
246 return ERR_PTR(-ENAMETOOLONG);
247 }
248 memcpy((char *)result->name, filename, len);
249 result->uptr = NULL;
250 result->aname = NULL;
251 result->refcnt = 1;
252 audit_getname(result);
253
254 return result;
255}
256
257void putname(struct filename *name)
258{
259 if (IS_ERR(name))
260 return;
261
262 BUG_ON(name->refcnt <= 0);
263
264 if (--name->refcnt > 0)
265 return;
266
267 if (name->name != name->iname) {
268 __putname(name->name);
269 kfree(name);
270 } else
271 __putname(name);
272}
273
274/**
275 * check_acl - perform ACL permission checking
276 * @mnt_userns: user namespace of the mount the inode was found from
277 * @inode: inode to check permissions on
278 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC ...)
279 *
280 * This function performs the ACL permission checking. Since this function
281 * retrieve POSIX acls it needs to know whether it is called from a blocking or
282 * non-blocking context and thus cares about the MAY_NOT_BLOCK bit.
283 *
284 * If the inode has been found through an idmapped mount the user namespace of
285 * the vfsmount must be passed through @mnt_userns. This function will then take
286 * care to map the inode according to @mnt_userns before checking permissions.
287 * On non-idmapped mounts or if permission checking is to be performed on the
288 * raw inode simply passs init_user_ns.
289 */
290static int check_acl(struct user_namespace *mnt_userns,
291 struct inode *inode, int mask)
292{
293#ifdef CONFIG_FS_POSIX_ACL
294 struct posix_acl *acl;
295
296 if (mask & MAY_NOT_BLOCK) {
297 acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS);
298 if (!acl)
299 return -EAGAIN;
300 /* no ->get_inode_acl() calls in RCU mode... */
301 if (is_uncached_acl(acl))
302 return -ECHILD;
303 return posix_acl_permission(mnt_userns, inode, acl, mask);
304 }
305
306 acl = get_inode_acl(inode, ACL_TYPE_ACCESS);
307 if (IS_ERR(acl))
308 return PTR_ERR(acl);
309 if (acl) {
310 int error = posix_acl_permission(mnt_userns, inode, acl, mask);
311 posix_acl_release(acl);
312 return error;
313 }
314#endif
315
316 return -EAGAIN;
317}
318
319/**
320 * acl_permission_check - perform basic UNIX permission checking
321 * @mnt_userns: user namespace of the mount the inode was found from
322 * @inode: inode to check permissions on
323 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC ...)
324 *
325 * This function performs the basic UNIX permission checking. Since this
326 * function may retrieve POSIX acls it needs to know whether it is called from a
327 * blocking or non-blocking context and thus cares about the MAY_NOT_BLOCK bit.
328 *
329 * If the inode has been found through an idmapped mount the user namespace of
330 * the vfsmount must be passed through @mnt_userns. This function will then take
331 * care to map the inode according to @mnt_userns before checking permissions.
332 * On non-idmapped mounts or if permission checking is to be performed on the
333 * raw inode simply passs init_user_ns.
334 */
335static int acl_permission_check(struct user_namespace *mnt_userns,
336 struct inode *inode, int mask)
337{
338 unsigned int mode = inode->i_mode;
339 vfsuid_t vfsuid;
340
341 /* Are we the owner? If so, ACL's don't matter */
342 vfsuid = i_uid_into_vfsuid(mnt_userns, inode);
343 if (likely(vfsuid_eq_kuid(vfsuid, current_fsuid()))) {
344 mask &= 7;
345 mode >>= 6;
346 return (mask & ~mode) ? -EACCES : 0;
347 }
348
349 /* Do we have ACL's? */
350 if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
351 int error = check_acl(mnt_userns, inode, mask);
352 if (error != -EAGAIN)
353 return error;
354 }
355
356 /* Only RWX matters for group/other mode bits */
357 mask &= 7;
358
359 /*
360 * Are the group permissions different from
361 * the other permissions in the bits we care
362 * about? Need to check group ownership if so.
363 */
364 if (mask & (mode ^ (mode >> 3))) {
365 vfsgid_t vfsgid = i_gid_into_vfsgid(mnt_userns, inode);
366 if (vfsgid_in_group_p(vfsgid))
367 mode >>= 3;
368 }
369
370 /* Bits in 'mode' clear that we require? */
371 return (mask & ~mode) ? -EACCES : 0;
372}
373
374/**
375 * generic_permission - check for access rights on a Posix-like filesystem
376 * @mnt_userns: user namespace of the mount the inode was found from
377 * @inode: inode to check access rights for
378 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC,
379 * %MAY_NOT_BLOCK ...)
380 *
381 * Used to check for read/write/execute permissions on a file.
382 * We use "fsuid" for this, letting us set arbitrary permissions
383 * for filesystem access without changing the "normal" uids which
384 * are used for other things.
385 *
386 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
387 * request cannot be satisfied (eg. requires blocking or too much complexity).
388 * It would then be called again in ref-walk mode.
389 *
390 * If the inode has been found through an idmapped mount the user namespace of
391 * the vfsmount must be passed through @mnt_userns. This function will then take
392 * care to map the inode according to @mnt_userns before checking permissions.
393 * On non-idmapped mounts or if permission checking is to be performed on the
394 * raw inode simply passs init_user_ns.
395 */
396int generic_permission(struct user_namespace *mnt_userns, struct inode *inode,
397 int mask)
398{
399 int ret;
400
401 /*
402 * Do the basic permission checks.
403 */
404 ret = acl_permission_check(mnt_userns, inode, mask);
405 if (ret != -EACCES)
406 return ret;
407
408 if (S_ISDIR(inode->i_mode)) {
409 /* DACs are overridable for directories */
410 if (!(mask & MAY_WRITE))
411 if (capable_wrt_inode_uidgid(mnt_userns, inode,
412 CAP_DAC_READ_SEARCH))
413 return 0;
414 if (capable_wrt_inode_uidgid(mnt_userns, inode,
415 CAP_DAC_OVERRIDE))
416 return 0;
417 return -EACCES;
418 }
419
420 /*
421 * Searching includes executable on directories, else just read.
422 */
423 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
424 if (mask == MAY_READ)
425 if (capable_wrt_inode_uidgid(mnt_userns, inode,
426 CAP_DAC_READ_SEARCH))
427 return 0;
428 /*
429 * Read/write DACs are always overridable.
430 * Executable DACs are overridable when there is
431 * at least one exec bit set.
432 */
433 if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
434 if (capable_wrt_inode_uidgid(mnt_userns, inode,
435 CAP_DAC_OVERRIDE))
436 return 0;
437
438 return -EACCES;
439}
440EXPORT_SYMBOL(generic_permission);
441
442/**
443 * do_inode_permission - UNIX permission checking
444 * @mnt_userns: user namespace of the mount the inode was found from
445 * @inode: inode to check permissions on
446 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC ...)
447 *
448 * We _really_ want to just do "generic_permission()" without
449 * even looking at the inode->i_op values. So we keep a cache
450 * flag in inode->i_opflags, that says "this has not special
451 * permission function, use the fast case".
452 */
453static inline int do_inode_permission(struct user_namespace *mnt_userns,
454 struct inode *inode, int mask)
455{
456 if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) {
457 if (likely(inode->i_op->permission))
458 return inode->i_op->permission(mnt_userns, inode, mask);
459
460 /* This gets set once for the inode lifetime */
461 spin_lock(&inode->i_lock);
462 inode->i_opflags |= IOP_FASTPERM;
463 spin_unlock(&inode->i_lock);
464 }
465 return generic_permission(mnt_userns, inode, mask);
466}
467
468/**
469 * sb_permission - Check superblock-level permissions
470 * @sb: Superblock of inode to check permission on
471 * @inode: Inode to check permission on
472 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
473 *
474 * Separate out file-system wide checks from inode-specific permission checks.
475 */
476static int sb_permission(struct super_block *sb, struct inode *inode, int mask)
477{
478 if (unlikely(mask & MAY_WRITE)) {
479 umode_t mode = inode->i_mode;
480
481 /* Nobody gets write access to a read-only fs. */
482 if (sb_rdonly(sb) && (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
483 return -EROFS;
484 }
485 return 0;
486}
487
488/**
489 * inode_permission - Check for access rights to a given inode
490 * @mnt_userns: User namespace of the mount the inode was found from
491 * @inode: Inode to check permission on
492 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
493 *
494 * Check for read/write/execute permissions on an inode. We use fs[ug]id for
495 * this, letting us set arbitrary permissions for filesystem access without
496 * changing the "normal" UIDs which are used for other things.
497 *
498 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
499 */
500int inode_permission(struct user_namespace *mnt_userns,
501 struct inode *inode, int mask)
502{
503 int retval;
504
505 retval = sb_permission(inode->i_sb, inode, mask);
506 if (retval)
507 return retval;
508
509 if (unlikely(mask & MAY_WRITE)) {
510 /*
511 * Nobody gets write access to an immutable file.
512 */
513 if (IS_IMMUTABLE(inode))
514 return -EPERM;
515
516 /*
517 * Updating mtime will likely cause i_uid and i_gid to be
518 * written back improperly if their true value is unknown
519 * to the vfs.
520 */
521 if (HAS_UNMAPPED_ID(mnt_userns, inode))
522 return -EACCES;
523 }
524
525 retval = do_inode_permission(mnt_userns, inode, mask);
526 if (retval)
527 return retval;
528
529 retval = devcgroup_inode_permission(inode, mask);
530 if (retval)
531 return retval;
532
533 return security_inode_permission(inode, mask);
534}
535EXPORT_SYMBOL(inode_permission);
536
537/**
538 * path_get - get a reference to a path
539 * @path: path to get the reference to
540 *
541 * Given a path increment the reference count to the dentry and the vfsmount.
542 */
543void path_get(const struct path *path)
544{
545 mntget(path->mnt);
546 dget(path->dentry);
547}
548EXPORT_SYMBOL(path_get);
549
550/**
551 * path_put - put a reference to a path
552 * @path: path to put the reference to
553 *
554 * Given a path decrement the reference count to the dentry and the vfsmount.
555 */
556void path_put(const struct path *path)
557{
558 dput(path->dentry);
559 mntput(path->mnt);
560}
561EXPORT_SYMBOL(path_put);
562
563#define EMBEDDED_LEVELS 2
564struct nameidata {
565 struct path path;
566 struct qstr last;
567 struct path root;
568 struct inode *inode; /* path.dentry.d_inode */
569 unsigned int flags, state;
570 unsigned seq, next_seq, m_seq, r_seq;
571 int last_type;
572 unsigned depth;
573 int total_link_count;
574 struct saved {
575 struct path link;
576 struct delayed_call done;
577 const char *name;
578 unsigned seq;
579 } *stack, internal[EMBEDDED_LEVELS];
580 struct filename *name;
581 struct nameidata *saved;
582 unsigned root_seq;
583 int dfd;
584 vfsuid_t dir_vfsuid;
585 umode_t dir_mode;
586} __randomize_layout;
587
588#define ND_ROOT_PRESET 1
589#define ND_ROOT_GRABBED 2
590#define ND_JUMPED 4
591
592static void __set_nameidata(struct nameidata *p, int dfd, struct filename *name)
593{
594 struct nameidata *old = current->nameidata;
595 p->stack = p->internal;
596 p->depth = 0;
597 p->dfd = dfd;
598 p->name = name;
599 p->path.mnt = NULL;
600 p->path.dentry = NULL;
601 p->total_link_count = old ? old->total_link_count : 0;
602 p->saved = old;
603 current->nameidata = p;
604}
605
606static inline void set_nameidata(struct nameidata *p, int dfd, struct filename *name,
607 const struct path *root)
608{
609 __set_nameidata(p, dfd, name);
610 p->state = 0;
611 if (unlikely(root)) {
612 p->state = ND_ROOT_PRESET;
613 p->root = *root;
614 }
615}
616
617static void restore_nameidata(void)
618{
619 struct nameidata *now = current->nameidata, *old = now->saved;
620
621 current->nameidata = old;
622 if (old)
623 old->total_link_count = now->total_link_count;
624 if (now->stack != now->internal)
625 kfree(now->stack);
626}
627
628static bool nd_alloc_stack(struct nameidata *nd)
629{
630 struct saved *p;
631
632 p= kmalloc_array(MAXSYMLINKS, sizeof(struct saved),
633 nd->flags & LOOKUP_RCU ? GFP_ATOMIC : GFP_KERNEL);
634 if (unlikely(!p))
635 return false;
636 memcpy(p, nd->internal, sizeof(nd->internal));
637 nd->stack = p;
638 return true;
639}
640
641/**
642 * path_connected - Verify that a dentry is below mnt.mnt_root
643 *
644 * Rename can sometimes move a file or directory outside of a bind
645 * mount, path_connected allows those cases to be detected.
646 */
647static bool path_connected(struct vfsmount *mnt, struct dentry *dentry)
648{
649 struct super_block *sb = mnt->mnt_sb;
650
651 /* Bind mounts can have disconnected paths */
652 if (mnt->mnt_root == sb->s_root)
653 return true;
654
655 return is_subdir(dentry, mnt->mnt_root);
656}
657
658static void drop_links(struct nameidata *nd)
659{
660 int i = nd->depth;
661 while (i--) {
662 struct saved *last = nd->stack + i;
663 do_delayed_call(&last->done);
664 clear_delayed_call(&last->done);
665 }
666}
667
668static void leave_rcu(struct nameidata *nd)
669{
670 nd->flags &= ~LOOKUP_RCU;
671 nd->seq = nd->next_seq = 0;
672 rcu_read_unlock();
673}
674
675static void terminate_walk(struct nameidata *nd)
676{
677 drop_links(nd);
678 if (!(nd->flags & LOOKUP_RCU)) {
679 int i;
680 path_put(&nd->path);
681 for (i = 0; i < nd->depth; i++)
682 path_put(&nd->stack[i].link);
683 if (nd->state & ND_ROOT_GRABBED) {
684 path_put(&nd->root);
685 nd->state &= ~ND_ROOT_GRABBED;
686 }
687 } else {
688 leave_rcu(nd);
689 }
690 nd->depth = 0;
691 nd->path.mnt = NULL;
692 nd->path.dentry = NULL;
693}
694
695/* path_put is needed afterwards regardless of success or failure */
696static bool __legitimize_path(struct path *path, unsigned seq, unsigned mseq)
697{
698 int res = __legitimize_mnt(path->mnt, mseq);
699 if (unlikely(res)) {
700 if (res > 0)
701 path->mnt = NULL;
702 path->dentry = NULL;
703 return false;
704 }
705 if (unlikely(!lockref_get_not_dead(&path->dentry->d_lockref))) {
706 path->dentry = NULL;
707 return false;
708 }
709 return !read_seqcount_retry(&path->dentry->d_seq, seq);
710}
711
712static inline bool legitimize_path(struct nameidata *nd,
713 struct path *path, unsigned seq)
714{
715 return __legitimize_path(path, seq, nd->m_seq);
716}
717
718static bool legitimize_links(struct nameidata *nd)
719{
720 int i;
721 if (unlikely(nd->flags & LOOKUP_CACHED)) {
722 drop_links(nd);
723 nd->depth = 0;
724 return false;
725 }
726 for (i = 0; i < nd->depth; i++) {
727 struct saved *last = nd->stack + i;
728 if (unlikely(!legitimize_path(nd, &last->link, last->seq))) {
729 drop_links(nd);
730 nd->depth = i + 1;
731 return false;
732 }
733 }
734 return true;
735}
736
737static bool legitimize_root(struct nameidata *nd)
738{
739 /* Nothing to do if nd->root is zero or is managed by the VFS user. */
740 if (!nd->root.mnt || (nd->state & ND_ROOT_PRESET))
741 return true;
742 nd->state |= ND_ROOT_GRABBED;
743 return legitimize_path(nd, &nd->root, nd->root_seq);
744}
745
746/*
747 * Path walking has 2 modes, rcu-walk and ref-walk (see
748 * Documentation/filesystems/path-lookup.txt). In situations when we can't
749 * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
750 * normal reference counts on dentries and vfsmounts to transition to ref-walk
751 * mode. Refcounts are grabbed at the last known good point before rcu-walk
752 * got stuck, so ref-walk may continue from there. If this is not successful
753 * (eg. a seqcount has changed), then failure is returned and it's up to caller
754 * to restart the path walk from the beginning in ref-walk mode.
755 */
756
757/**
758 * try_to_unlazy - try to switch to ref-walk mode.
759 * @nd: nameidata pathwalk data
760 * Returns: true on success, false on failure
761 *
762 * try_to_unlazy attempts to legitimize the current nd->path and nd->root
763 * for ref-walk mode.
764 * Must be called from rcu-walk context.
765 * Nothing should touch nameidata between try_to_unlazy() failure and
766 * terminate_walk().
767 */
768static bool try_to_unlazy(struct nameidata *nd)
769{
770 struct dentry *parent = nd->path.dentry;
771
772 BUG_ON(!(nd->flags & LOOKUP_RCU));
773
774 if (unlikely(!legitimize_links(nd)))
775 goto out1;
776 if (unlikely(!legitimize_path(nd, &nd->path, nd->seq)))
777 goto out;
778 if (unlikely(!legitimize_root(nd)))
779 goto out;
780 leave_rcu(nd);
781 BUG_ON(nd->inode != parent->d_inode);
782 return true;
783
784out1:
785 nd->path.mnt = NULL;
786 nd->path.dentry = NULL;
787out:
788 leave_rcu(nd);
789 return false;
790}
791
792/**
793 * try_to_unlazy_next - try to switch to ref-walk mode.
794 * @nd: nameidata pathwalk data
795 * @dentry: next dentry to step into
796 * Returns: true on success, false on failure
797 *
798 * Similar to try_to_unlazy(), but here we have the next dentry already
799 * picked by rcu-walk and want to legitimize that in addition to the current
800 * nd->path and nd->root for ref-walk mode. Must be called from rcu-walk context.
801 * Nothing should touch nameidata between try_to_unlazy_next() failure and
802 * terminate_walk().
803 */
804static bool try_to_unlazy_next(struct nameidata *nd, struct dentry *dentry)
805{
806 int res;
807 BUG_ON(!(nd->flags & LOOKUP_RCU));
808
809 if (unlikely(!legitimize_links(nd)))
810 goto out2;
811 res = __legitimize_mnt(nd->path.mnt, nd->m_seq);
812 if (unlikely(res)) {
813 if (res > 0)
814 goto out2;
815 goto out1;
816 }
817 if (unlikely(!lockref_get_not_dead(&nd->path.dentry->d_lockref)))
818 goto out1;
819
820 /*
821 * We need to move both the parent and the dentry from the RCU domain
822 * to be properly refcounted. And the sequence number in the dentry
823 * validates *both* dentry counters, since we checked the sequence
824 * number of the parent after we got the child sequence number. So we
825 * know the parent must still be valid if the child sequence number is
826 */
827 if (unlikely(!lockref_get_not_dead(&dentry->d_lockref)))
828 goto out;
829 if (read_seqcount_retry(&dentry->d_seq, nd->next_seq))
830 goto out_dput;
831 /*
832 * Sequence counts matched. Now make sure that the root is
833 * still valid and get it if required.
834 */
835 if (unlikely(!legitimize_root(nd)))
836 goto out_dput;
837 leave_rcu(nd);
838 return true;
839
840out2:
841 nd->path.mnt = NULL;
842out1:
843 nd->path.dentry = NULL;
844out:
845 leave_rcu(nd);
846 return false;
847out_dput:
848 leave_rcu(nd);
849 dput(dentry);
850 return false;
851}
852
853static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
854{
855 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE))
856 return dentry->d_op->d_revalidate(dentry, flags);
857 else
858 return 1;
859}
860
861/**
862 * complete_walk - successful completion of path walk
863 * @nd: pointer nameidata
864 *
865 * If we had been in RCU mode, drop out of it and legitimize nd->path.
866 * Revalidate the final result, unless we'd already done that during
867 * the path walk or the filesystem doesn't ask for it. Return 0 on
868 * success, -error on failure. In case of failure caller does not
869 * need to drop nd->path.
870 */
871static int complete_walk(struct nameidata *nd)
872{
873 struct dentry *dentry = nd->path.dentry;
874 int status;
875
876 if (nd->flags & LOOKUP_RCU) {
877 /*
878 * We don't want to zero nd->root for scoped-lookups or
879 * externally-managed nd->root.
880 */
881 if (!(nd->state & ND_ROOT_PRESET))
882 if (!(nd->flags & LOOKUP_IS_SCOPED))
883 nd->root.mnt = NULL;
884 nd->flags &= ~LOOKUP_CACHED;
885 if (!try_to_unlazy(nd))
886 return -ECHILD;
887 }
888
889 if (unlikely(nd->flags & LOOKUP_IS_SCOPED)) {
890 /*
891 * While the guarantee of LOOKUP_IS_SCOPED is (roughly) "don't
892 * ever step outside the root during lookup" and should already
893 * be guaranteed by the rest of namei, we want to avoid a namei
894 * BUG resulting in userspace being given a path that was not
895 * scoped within the root at some point during the lookup.
896 *
897 * So, do a final sanity-check to make sure that in the
898 * worst-case scenario (a complete bypass of LOOKUP_IS_SCOPED)
899 * we won't silently return an fd completely outside of the
900 * requested root to userspace.
901 *
902 * Userspace could move the path outside the root after this
903 * check, but as discussed elsewhere this is not a concern (the
904 * resolved file was inside the root at some point).
905 */
906 if (!path_is_under(&nd->path, &nd->root))
907 return -EXDEV;
908 }
909
910 if (likely(!(nd->state & ND_JUMPED)))
911 return 0;
912
913 if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE)))
914 return 0;
915
916 status = dentry->d_op->d_weak_revalidate(dentry, nd->flags);
917 if (status > 0)
918 return 0;
919
920 if (!status)
921 status = -ESTALE;
922
923 return status;
924}
925
926static int set_root(struct nameidata *nd)
927{
928 struct fs_struct *fs = current->fs;
929
930 /*
931 * Jumping to the real root in a scoped-lookup is a BUG in namei, but we
932 * still have to ensure it doesn't happen because it will cause a breakout
933 * from the dirfd.
934 */
935 if (WARN_ON(nd->flags & LOOKUP_IS_SCOPED))
936 return -ENOTRECOVERABLE;
937
938 if (nd->flags & LOOKUP_RCU) {
939 unsigned seq;
940
941 do {
942 seq = read_seqcount_begin(&fs->seq);
943 nd->root = fs->root;
944 nd->root_seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
945 } while (read_seqcount_retry(&fs->seq, seq));
946 } else {
947 get_fs_root(fs, &nd->root);
948 nd->state |= ND_ROOT_GRABBED;
949 }
950 return 0;
951}
952
953static int nd_jump_root(struct nameidata *nd)
954{
955 if (unlikely(nd->flags & LOOKUP_BENEATH))
956 return -EXDEV;
957 if (unlikely(nd->flags & LOOKUP_NO_XDEV)) {
958 /* Absolute path arguments to path_init() are allowed. */
959 if (nd->path.mnt != NULL && nd->path.mnt != nd->root.mnt)
960 return -EXDEV;
961 }
962 if (!nd->root.mnt) {
963 int error = set_root(nd);
964 if (error)
965 return error;
966 }
967 if (nd->flags & LOOKUP_RCU) {
968 struct dentry *d;
969 nd->path = nd->root;
970 d = nd->path.dentry;
971 nd->inode = d->d_inode;
972 nd->seq = nd->root_seq;
973 if (read_seqcount_retry(&d->d_seq, nd->seq))
974 return -ECHILD;
975 } else {
976 path_put(&nd->path);
977 nd->path = nd->root;
978 path_get(&nd->path);
979 nd->inode = nd->path.dentry->d_inode;
980 }
981 nd->state |= ND_JUMPED;
982 return 0;
983}
984
985/*
986 * Helper to directly jump to a known parsed path from ->get_link,
987 * caller must have taken a reference to path beforehand.
988 */
989int nd_jump_link(const struct path *path)
990{
991 int error = -ELOOP;
992 struct nameidata *nd = current->nameidata;
993
994 if (unlikely(nd->flags & LOOKUP_NO_MAGICLINKS))
995 goto err;
996
997 error = -EXDEV;
998 if (unlikely(nd->flags & LOOKUP_NO_XDEV)) {
999 if (nd->path.mnt != path->mnt)
1000 goto err;
1001 }
1002 /* Not currently safe for scoped-lookups. */
1003 if (unlikely(nd->flags & LOOKUP_IS_SCOPED))
1004 goto err;
1005
1006 path_put(&nd->path);
1007 nd->path = *path;
1008 nd->inode = nd->path.dentry->d_inode;
1009 nd->state |= ND_JUMPED;
1010 return 0;
1011
1012err:
1013 path_put(path);
1014 return error;
1015}
1016
1017static inline void put_link(struct nameidata *nd)
1018{
1019 struct saved *last = nd->stack + --nd->depth;
1020 do_delayed_call(&last->done);
1021 if (!(nd->flags & LOOKUP_RCU))
1022 path_put(&last->link);
1023}
1024
1025static int sysctl_protected_symlinks __read_mostly;
1026static int sysctl_protected_hardlinks __read_mostly;
1027static int sysctl_protected_fifos __read_mostly;
1028static int sysctl_protected_regular __read_mostly;
1029
1030#ifdef CONFIG_SYSCTL
1031static struct ctl_table namei_sysctls[] = {
1032 {
1033 .procname = "protected_symlinks",
1034 .data = &sysctl_protected_symlinks,
1035 .maxlen = sizeof(int),
1036 .mode = 0644,
1037 .proc_handler = proc_dointvec_minmax,
1038 .extra1 = SYSCTL_ZERO,
1039 .extra2 = SYSCTL_ONE,
1040 },
1041 {
1042 .procname = "protected_hardlinks",
1043 .data = &sysctl_protected_hardlinks,
1044 .maxlen = sizeof(int),
1045 .mode = 0644,
1046 .proc_handler = proc_dointvec_minmax,
1047 .extra1 = SYSCTL_ZERO,
1048 .extra2 = SYSCTL_ONE,
1049 },
1050 {
1051 .procname = "protected_fifos",
1052 .data = &sysctl_protected_fifos,
1053 .maxlen = sizeof(int),
1054 .mode = 0644,
1055 .proc_handler = proc_dointvec_minmax,
1056 .extra1 = SYSCTL_ZERO,
1057 .extra2 = SYSCTL_TWO,
1058 },
1059 {
1060 .procname = "protected_regular",
1061 .data = &sysctl_protected_regular,
1062 .maxlen = sizeof(int),
1063 .mode = 0644,
1064 .proc_handler = proc_dointvec_minmax,
1065 .extra1 = SYSCTL_ZERO,
1066 .extra2 = SYSCTL_TWO,
1067 },
1068 { }
1069};
1070
1071static int __init init_fs_namei_sysctls(void)
1072{
1073 register_sysctl_init("fs", namei_sysctls);
1074 return 0;
1075}
1076fs_initcall(init_fs_namei_sysctls);
1077
1078#endif /* CONFIG_SYSCTL */
1079
1080/**
1081 * may_follow_link - Check symlink following for unsafe situations
1082 * @nd: nameidata pathwalk data
1083 *
1084 * In the case of the sysctl_protected_symlinks sysctl being enabled,
1085 * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
1086 * in a sticky world-writable directory. This is to protect privileged
1087 * processes from failing races against path names that may change out
1088 * from under them by way of other users creating malicious symlinks.
1089 * It will permit symlinks to be followed only when outside a sticky
1090 * world-writable directory, or when the uid of the symlink and follower
1091 * match, or when the directory owner matches the symlink's owner.
1092 *
1093 * Returns 0 if following the symlink is allowed, -ve on error.
1094 */
1095static inline int may_follow_link(struct nameidata *nd, const struct inode *inode)
1096{
1097 struct user_namespace *mnt_userns;
1098 vfsuid_t vfsuid;
1099
1100 if (!sysctl_protected_symlinks)
1101 return 0;
1102
1103 mnt_userns = mnt_user_ns(nd->path.mnt);
1104 vfsuid = i_uid_into_vfsuid(mnt_userns, inode);
1105 /* Allowed if owner and follower match. */
1106 if (vfsuid_eq_kuid(vfsuid, current_fsuid()))
1107 return 0;
1108
1109 /* Allowed if parent directory not sticky and world-writable. */
1110 if ((nd->dir_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH))
1111 return 0;
1112
1113 /* Allowed if parent directory and link owner match. */
1114 if (vfsuid_valid(nd->dir_vfsuid) && vfsuid_eq(nd->dir_vfsuid, vfsuid))
1115 return 0;
1116
1117 if (nd->flags & LOOKUP_RCU)
1118 return -ECHILD;
1119
1120 audit_inode(nd->name, nd->stack[0].link.dentry, 0);
1121 audit_log_path_denied(AUDIT_ANOM_LINK, "follow_link");
1122 return -EACCES;
1123}
1124
1125/**
1126 * safe_hardlink_source - Check for safe hardlink conditions
1127 * @mnt_userns: user namespace of the mount the inode was found from
1128 * @inode: the source inode to hardlink from
1129 *
1130 * Return false if at least one of the following conditions:
1131 * - inode is not a regular file
1132 * - inode is setuid
1133 * - inode is setgid and group-exec
1134 * - access failure for read and write
1135 *
1136 * Otherwise returns true.
1137 */
1138static bool safe_hardlink_source(struct user_namespace *mnt_userns,
1139 struct inode *inode)
1140{
1141 umode_t mode = inode->i_mode;
1142
1143 /* Special files should not get pinned to the filesystem. */
1144 if (!S_ISREG(mode))
1145 return false;
1146
1147 /* Setuid files should not get pinned to the filesystem. */
1148 if (mode & S_ISUID)
1149 return false;
1150
1151 /* Executable setgid files should not get pinned to the filesystem. */
1152 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP))
1153 return false;
1154
1155 /* Hardlinking to unreadable or unwritable sources is dangerous. */
1156 if (inode_permission(mnt_userns, inode, MAY_READ | MAY_WRITE))
1157 return false;
1158
1159 return true;
1160}
1161
1162/**
1163 * may_linkat - Check permissions for creating a hardlink
1164 * @mnt_userns: user namespace of the mount the inode was found from
1165 * @link: the source to hardlink from
1166 *
1167 * Block hardlink when all of:
1168 * - sysctl_protected_hardlinks enabled
1169 * - fsuid does not match inode
1170 * - hardlink source is unsafe (see safe_hardlink_source() above)
1171 * - not CAP_FOWNER in a namespace with the inode owner uid mapped
1172 *
1173 * If the inode has been found through an idmapped mount the user namespace of
1174 * the vfsmount must be passed through @mnt_userns. This function will then take
1175 * care to map the inode according to @mnt_userns before checking permissions.
1176 * On non-idmapped mounts or if permission checking is to be performed on the
1177 * raw inode simply passs init_user_ns.
1178 *
1179 * Returns 0 if successful, -ve on error.
1180 */
1181int may_linkat(struct user_namespace *mnt_userns, const struct path *link)
1182{
1183 struct inode *inode = link->dentry->d_inode;
1184
1185 /* Inode writeback is not safe when the uid or gid are invalid. */
1186 if (!vfsuid_valid(i_uid_into_vfsuid(mnt_userns, inode)) ||
1187 !vfsgid_valid(i_gid_into_vfsgid(mnt_userns, inode)))
1188 return -EOVERFLOW;
1189
1190 if (!sysctl_protected_hardlinks)
1191 return 0;
1192
1193 /* Source inode owner (or CAP_FOWNER) can hardlink all they like,
1194 * otherwise, it must be a safe source.
1195 */
1196 if (safe_hardlink_source(mnt_userns, inode) ||
1197 inode_owner_or_capable(mnt_userns, inode))
1198 return 0;
1199
1200 audit_log_path_denied(AUDIT_ANOM_LINK, "linkat");
1201 return -EPERM;
1202}
1203
1204/**
1205 * may_create_in_sticky - Check whether an O_CREAT open in a sticky directory
1206 * should be allowed, or not, on files that already
1207 * exist.
1208 * @mnt_userns: user namespace of the mount the inode was found from
1209 * @nd: nameidata pathwalk data
1210 * @inode: the inode of the file to open
1211 *
1212 * Block an O_CREAT open of a FIFO (or a regular file) when:
1213 * - sysctl_protected_fifos (or sysctl_protected_regular) is enabled
1214 * - the file already exists
1215 * - we are in a sticky directory
1216 * - we don't own the file
1217 * - the owner of the directory doesn't own the file
1218 * - the directory is world writable
1219 * If the sysctl_protected_fifos (or sysctl_protected_regular) is set to 2
1220 * the directory doesn't have to be world writable: being group writable will
1221 * be enough.
1222 *
1223 * If the inode has been found through an idmapped mount the user namespace of
1224 * the vfsmount must be passed through @mnt_userns. This function will then take
1225 * care to map the inode according to @mnt_userns before checking permissions.
1226 * On non-idmapped mounts or if permission checking is to be performed on the
1227 * raw inode simply passs init_user_ns.
1228 *
1229 * Returns 0 if the open is allowed, -ve on error.
1230 */
1231static int may_create_in_sticky(struct user_namespace *mnt_userns,
1232 struct nameidata *nd, struct inode *const inode)
1233{
1234 umode_t dir_mode = nd->dir_mode;
1235 vfsuid_t dir_vfsuid = nd->dir_vfsuid;
1236
1237 if ((!sysctl_protected_fifos && S_ISFIFO(inode->i_mode)) ||
1238 (!sysctl_protected_regular && S_ISREG(inode->i_mode)) ||
1239 likely(!(dir_mode & S_ISVTX)) ||
1240 vfsuid_eq(i_uid_into_vfsuid(mnt_userns, inode), dir_vfsuid) ||
1241 vfsuid_eq_kuid(i_uid_into_vfsuid(mnt_userns, inode), current_fsuid()))
1242 return 0;
1243
1244 if (likely(dir_mode & 0002) ||
1245 (dir_mode & 0020 &&
1246 ((sysctl_protected_fifos >= 2 && S_ISFIFO(inode->i_mode)) ||
1247 (sysctl_protected_regular >= 2 && S_ISREG(inode->i_mode))))) {
1248 const char *operation = S_ISFIFO(inode->i_mode) ?
1249 "sticky_create_fifo" :
1250 "sticky_create_regular";
1251 audit_log_path_denied(AUDIT_ANOM_CREAT, operation);
1252 return -EACCES;
1253 }
1254 return 0;
1255}
1256
1257/*
1258 * follow_up - Find the mountpoint of path's vfsmount
1259 *
1260 * Given a path, find the mountpoint of its source file system.
1261 * Replace @path with the path of the mountpoint in the parent mount.
1262 * Up is towards /.
1263 *
1264 * Return 1 if we went up a level and 0 if we were already at the
1265 * root.
1266 */
1267int follow_up(struct path *path)
1268{
1269 struct mount *mnt = real_mount(path->mnt);
1270 struct mount *parent;
1271 struct dentry *mountpoint;
1272
1273 read_seqlock_excl(&mount_lock);
1274 parent = mnt->mnt_parent;
1275 if (parent == mnt) {
1276 read_sequnlock_excl(&mount_lock);
1277 return 0;
1278 }
1279 mntget(&parent->mnt);
1280 mountpoint = dget(mnt->mnt_mountpoint);
1281 read_sequnlock_excl(&mount_lock);
1282 dput(path->dentry);
1283 path->dentry = mountpoint;
1284 mntput(path->mnt);
1285 path->mnt = &parent->mnt;
1286 return 1;
1287}
1288EXPORT_SYMBOL(follow_up);
1289
1290static bool choose_mountpoint_rcu(struct mount *m, const struct path *root,
1291 struct path *path, unsigned *seqp)
1292{
1293 while (mnt_has_parent(m)) {
1294 struct dentry *mountpoint = m->mnt_mountpoint;
1295
1296 m = m->mnt_parent;
1297 if (unlikely(root->dentry == mountpoint &&
1298 root->mnt == &m->mnt))
1299 break;
1300 if (mountpoint != m->mnt.mnt_root) {
1301 path->mnt = &m->mnt;
1302 path->dentry = mountpoint;
1303 *seqp = read_seqcount_begin(&mountpoint->d_seq);
1304 return true;
1305 }
1306 }
1307 return false;
1308}
1309
1310static bool choose_mountpoint(struct mount *m, const struct path *root,
1311 struct path *path)
1312{
1313 bool found;
1314
1315 rcu_read_lock();
1316 while (1) {
1317 unsigned seq, mseq = read_seqbegin(&mount_lock);
1318
1319 found = choose_mountpoint_rcu(m, root, path, &seq);
1320 if (unlikely(!found)) {
1321 if (!read_seqretry(&mount_lock, mseq))
1322 break;
1323 } else {
1324 if (likely(__legitimize_path(path, seq, mseq)))
1325 break;
1326 rcu_read_unlock();
1327 path_put(path);
1328 rcu_read_lock();
1329 }
1330 }
1331 rcu_read_unlock();
1332 return found;
1333}
1334
1335/*
1336 * Perform an automount
1337 * - return -EISDIR to tell follow_managed() to stop and return the path we
1338 * were called with.
1339 */
1340static int follow_automount(struct path *path, int *count, unsigned lookup_flags)
1341{
1342 struct dentry *dentry = path->dentry;
1343
1344 /* We don't want to mount if someone's just doing a stat -
1345 * unless they're stat'ing a directory and appended a '/' to
1346 * the name.
1347 *
1348 * We do, however, want to mount if someone wants to open or
1349 * create a file of any type under the mountpoint, wants to
1350 * traverse through the mountpoint or wants to open the
1351 * mounted directory. Also, autofs may mark negative dentries
1352 * as being automount points. These will need the attentions
1353 * of the daemon to instantiate them before they can be used.
1354 */
1355 if (!(lookup_flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
1356 LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
1357 dentry->d_inode)
1358 return -EISDIR;
1359
1360 if (count && (*count)++ >= MAXSYMLINKS)
1361 return -ELOOP;
1362
1363 return finish_automount(dentry->d_op->d_automount(path), path);
1364}
1365
1366/*
1367 * mount traversal - out-of-line part. One note on ->d_flags accesses -
1368 * dentries are pinned but not locked here, so negative dentry can go
1369 * positive right under us. Use of smp_load_acquire() provides a barrier
1370 * sufficient for ->d_inode and ->d_flags consistency.
1371 */
1372static int __traverse_mounts(struct path *path, unsigned flags, bool *jumped,
1373 int *count, unsigned lookup_flags)
1374{
1375 struct vfsmount *mnt = path->mnt;
1376 bool need_mntput = false;
1377 int ret = 0;
1378
1379 while (flags & DCACHE_MANAGED_DENTRY) {
1380 /* Allow the filesystem to manage the transit without i_mutex
1381 * being held. */
1382 if (flags & DCACHE_MANAGE_TRANSIT) {
1383 ret = path->dentry->d_op->d_manage(path, false);
1384 flags = smp_load_acquire(&path->dentry->d_flags);
1385 if (ret < 0)
1386 break;
1387 }
1388
1389 if (flags & DCACHE_MOUNTED) { // something's mounted on it..
1390 struct vfsmount *mounted = lookup_mnt(path);
1391 if (mounted) { // ... in our namespace
1392 dput(path->dentry);
1393 if (need_mntput)
1394 mntput(path->mnt);
1395 path->mnt = mounted;
1396 path->dentry = dget(mounted->mnt_root);
1397 // here we know it's positive
1398 flags = path->dentry->d_flags;
1399 need_mntput = true;
1400 continue;
1401 }
1402 }
1403
1404 if (!(flags & DCACHE_NEED_AUTOMOUNT))
1405 break;
1406
1407 // uncovered automount point
1408 ret = follow_automount(path, count, lookup_flags);
1409 flags = smp_load_acquire(&path->dentry->d_flags);
1410 if (ret < 0)
1411 break;
1412 }
1413
1414 if (ret == -EISDIR)
1415 ret = 0;
1416 // possible if you race with several mount --move
1417 if (need_mntput && path->mnt == mnt)
1418 mntput(path->mnt);
1419 if (!ret && unlikely(d_flags_negative(flags)))
1420 ret = -ENOENT;
1421 *jumped = need_mntput;
1422 return ret;
1423}
1424
1425static inline int traverse_mounts(struct path *path, bool *jumped,
1426 int *count, unsigned lookup_flags)
1427{
1428 unsigned flags = smp_load_acquire(&path->dentry->d_flags);
1429
1430 /* fastpath */
1431 if (likely(!(flags & DCACHE_MANAGED_DENTRY))) {
1432 *jumped = false;
1433 if (unlikely(d_flags_negative(flags)))
1434 return -ENOENT;
1435 return 0;
1436 }
1437 return __traverse_mounts(path, flags, jumped, count, lookup_flags);
1438}
1439
1440int follow_down_one(struct path *path)
1441{
1442 struct vfsmount *mounted;
1443
1444 mounted = lookup_mnt(path);
1445 if (mounted) {
1446 dput(path->dentry);
1447 mntput(path->mnt);
1448 path->mnt = mounted;
1449 path->dentry = dget(mounted->mnt_root);
1450 return 1;
1451 }
1452 return 0;
1453}
1454EXPORT_SYMBOL(follow_down_one);
1455
1456/*
1457 * Follow down to the covering mount currently visible to userspace. At each
1458 * point, the filesystem owning that dentry may be queried as to whether the
1459 * caller is permitted to proceed or not.
1460 */
1461int follow_down(struct path *path)
1462{
1463 struct vfsmount *mnt = path->mnt;
1464 bool jumped;
1465 int ret = traverse_mounts(path, &jumped, NULL, 0);
1466
1467 if (path->mnt != mnt)
1468 mntput(mnt);
1469 return ret;
1470}
1471EXPORT_SYMBOL(follow_down);
1472
1473/*
1474 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
1475 * we meet a managed dentry that would need blocking.
1476 */
1477static bool __follow_mount_rcu(struct nameidata *nd, struct path *path)
1478{
1479 struct dentry *dentry = path->dentry;
1480 unsigned int flags = dentry->d_flags;
1481
1482 if (likely(!(flags & DCACHE_MANAGED_DENTRY)))
1483 return true;
1484
1485 if (unlikely(nd->flags & LOOKUP_NO_XDEV))
1486 return false;
1487
1488 for (;;) {
1489 /*
1490 * Don't forget we might have a non-mountpoint managed dentry
1491 * that wants to block transit.
1492 */
1493 if (unlikely(flags & DCACHE_MANAGE_TRANSIT)) {
1494 int res = dentry->d_op->d_manage(path, true);
1495 if (res)
1496 return res == -EISDIR;
1497 flags = dentry->d_flags;
1498 }
1499
1500 if (flags & DCACHE_MOUNTED) {
1501 struct mount *mounted = __lookup_mnt(path->mnt, dentry);
1502 if (mounted) {
1503 path->mnt = &mounted->mnt;
1504 dentry = path->dentry = mounted->mnt.mnt_root;
1505 nd->state |= ND_JUMPED;
1506 nd->next_seq = read_seqcount_begin(&dentry->d_seq);
1507 flags = dentry->d_flags;
1508 // makes sure that non-RCU pathwalk could reach
1509 // this state.
1510 if (read_seqretry(&mount_lock, nd->m_seq))
1511 return false;
1512 continue;
1513 }
1514 if (read_seqretry(&mount_lock, nd->m_seq))
1515 return false;
1516 }
1517 return !(flags & DCACHE_NEED_AUTOMOUNT);
1518 }
1519}
1520
1521static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry,
1522 struct path *path)
1523{
1524 bool jumped;
1525 int ret;
1526
1527 path->mnt = nd->path.mnt;
1528 path->dentry = dentry;
1529 if (nd->flags & LOOKUP_RCU) {
1530 unsigned int seq = nd->next_seq;
1531 if (likely(__follow_mount_rcu(nd, path)))
1532 return 0;
1533 // *path and nd->next_seq might've been clobbered
1534 path->mnt = nd->path.mnt;
1535 path->dentry = dentry;
1536 nd->next_seq = seq;
1537 if (!try_to_unlazy_next(nd, dentry))
1538 return -ECHILD;
1539 }
1540 ret = traverse_mounts(path, &jumped, &nd->total_link_count, nd->flags);
1541 if (jumped) {
1542 if (unlikely(nd->flags & LOOKUP_NO_XDEV))
1543 ret = -EXDEV;
1544 else
1545 nd->state |= ND_JUMPED;
1546 }
1547 if (unlikely(ret)) {
1548 dput(path->dentry);
1549 if (path->mnt != nd->path.mnt)
1550 mntput(path->mnt);
1551 }
1552 return ret;
1553}
1554
1555/*
1556 * This looks up the name in dcache and possibly revalidates the found dentry.
1557 * NULL is returned if the dentry does not exist in the cache.
1558 */
1559static struct dentry *lookup_dcache(const struct qstr *name,
1560 struct dentry *dir,
1561 unsigned int flags)
1562{
1563 struct dentry *dentry = d_lookup(dir, name);
1564 if (dentry) {
1565 int error = d_revalidate(dentry, flags);
1566 if (unlikely(error <= 0)) {
1567 if (!error)
1568 d_invalidate(dentry);
1569 dput(dentry);
1570 return ERR_PTR(error);
1571 }
1572 }
1573 return dentry;
1574}
1575
1576/*
1577 * Parent directory has inode locked exclusive. This is one
1578 * and only case when ->lookup() gets called on non in-lookup
1579 * dentries - as the matter of fact, this only gets called
1580 * when directory is guaranteed to have no in-lookup children
1581 * at all.
1582 */
1583static struct dentry *__lookup_hash(const struct qstr *name,
1584 struct dentry *base, unsigned int flags)
1585{
1586 struct dentry *dentry = lookup_dcache(name, base, flags);
1587 struct dentry *old;
1588 struct inode *dir = base->d_inode;
1589
1590 if (dentry)
1591 return dentry;
1592
1593 /* Don't create child dentry for a dead directory. */
1594 if (unlikely(IS_DEADDIR(dir)))
1595 return ERR_PTR(-ENOENT);
1596
1597 dentry = d_alloc(base, name);
1598 if (unlikely(!dentry))
1599 return ERR_PTR(-ENOMEM);
1600
1601 old = dir->i_op->lookup(dir, dentry, flags);
1602 if (unlikely(old)) {
1603 dput(dentry);
1604 dentry = old;
1605 }
1606 return dentry;
1607}
1608
1609static struct dentry *lookup_fast(struct nameidata *nd)
1610{
1611 struct dentry *dentry, *parent = nd->path.dentry;
1612 int status = 1;
1613
1614 /*
1615 * Rename seqlock is not required here because in the off chance
1616 * of a false negative due to a concurrent rename, the caller is
1617 * going to fall back to non-racy lookup.
1618 */
1619 if (nd->flags & LOOKUP_RCU) {
1620 dentry = __d_lookup_rcu(parent, &nd->last, &nd->next_seq);
1621 if (unlikely(!dentry)) {
1622 if (!try_to_unlazy(nd))
1623 return ERR_PTR(-ECHILD);
1624 return NULL;
1625 }
1626
1627 /*
1628 * This sequence count validates that the parent had no
1629 * changes while we did the lookup of the dentry above.
1630 */
1631 if (read_seqcount_retry(&parent->d_seq, nd->seq))
1632 return ERR_PTR(-ECHILD);
1633
1634 status = d_revalidate(dentry, nd->flags);
1635 if (likely(status > 0))
1636 return dentry;
1637 if (!try_to_unlazy_next(nd, dentry))
1638 return ERR_PTR(-ECHILD);
1639 if (status == -ECHILD)
1640 /* we'd been told to redo it in non-rcu mode */
1641 status = d_revalidate(dentry, nd->flags);
1642 } else {
1643 dentry = __d_lookup(parent, &nd->last);
1644 if (unlikely(!dentry))
1645 return NULL;
1646 status = d_revalidate(dentry, nd->flags);
1647 }
1648 if (unlikely(status <= 0)) {
1649 if (!status)
1650 d_invalidate(dentry);
1651 dput(dentry);
1652 return ERR_PTR(status);
1653 }
1654 return dentry;
1655}
1656
1657/* Fast lookup failed, do it the slow way */
1658static struct dentry *__lookup_slow(const struct qstr *name,
1659 struct dentry *dir,
1660 unsigned int flags)
1661{
1662 struct dentry *dentry, *old;
1663 struct inode *inode = dir->d_inode;
1664 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
1665
1666 /* Don't go there if it's already dead */
1667 if (unlikely(IS_DEADDIR(inode)))
1668 return ERR_PTR(-ENOENT);
1669again:
1670 dentry = d_alloc_parallel(dir, name, &wq);
1671 if (IS_ERR(dentry))
1672 return dentry;
1673 if (unlikely(!d_in_lookup(dentry))) {
1674 int error = d_revalidate(dentry, flags);
1675 if (unlikely(error <= 0)) {
1676 if (!error) {
1677 d_invalidate(dentry);
1678 dput(dentry);
1679 goto again;
1680 }
1681 dput(dentry);
1682 dentry = ERR_PTR(error);
1683 }
1684 } else {
1685 old = inode->i_op->lookup(inode, dentry, flags);
1686 d_lookup_done(dentry);
1687 if (unlikely(old)) {
1688 dput(dentry);
1689 dentry = old;
1690 }
1691 }
1692 return dentry;
1693}
1694
1695static struct dentry *lookup_slow(const struct qstr *name,
1696 struct dentry *dir,
1697 unsigned int flags)
1698{
1699 struct inode *inode = dir->d_inode;
1700 struct dentry *res;
1701 inode_lock_shared(inode);
1702 res = __lookup_slow(name, dir, flags);
1703 inode_unlock_shared(inode);
1704 return res;
1705}
1706
1707static inline int may_lookup(struct user_namespace *mnt_userns,
1708 struct nameidata *nd)
1709{
1710 if (nd->flags & LOOKUP_RCU) {
1711 int err = inode_permission(mnt_userns, nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
1712 if (err != -ECHILD || !try_to_unlazy(nd))
1713 return err;
1714 }
1715 return inode_permission(mnt_userns, nd->inode, MAY_EXEC);
1716}
1717
1718static int reserve_stack(struct nameidata *nd, struct path *link)
1719{
1720 if (unlikely(nd->total_link_count++ >= MAXSYMLINKS))
1721 return -ELOOP;
1722
1723 if (likely(nd->depth != EMBEDDED_LEVELS))
1724 return 0;
1725 if (likely(nd->stack != nd->internal))
1726 return 0;
1727 if (likely(nd_alloc_stack(nd)))
1728 return 0;
1729
1730 if (nd->flags & LOOKUP_RCU) {
1731 // we need to grab link before we do unlazy. And we can't skip
1732 // unlazy even if we fail to grab the link - cleanup needs it
1733 bool grabbed_link = legitimize_path(nd, link, nd->next_seq);
1734
1735 if (!try_to_unlazy(nd) || !grabbed_link)
1736 return -ECHILD;
1737
1738 if (nd_alloc_stack(nd))
1739 return 0;
1740 }
1741 return -ENOMEM;
1742}
1743
1744enum {WALK_TRAILING = 1, WALK_MORE = 2, WALK_NOFOLLOW = 4};
1745
1746static const char *pick_link(struct nameidata *nd, struct path *link,
1747 struct inode *inode, int flags)
1748{
1749 struct saved *last;
1750 const char *res;
1751 int error = reserve_stack(nd, link);
1752
1753 if (unlikely(error)) {
1754 if (!(nd->flags & LOOKUP_RCU))
1755 path_put(link);
1756 return ERR_PTR(error);
1757 }
1758 last = nd->stack + nd->depth++;
1759 last->link = *link;
1760 clear_delayed_call(&last->done);
1761 last->seq = nd->next_seq;
1762
1763 if (flags & WALK_TRAILING) {
1764 error = may_follow_link(nd, inode);
1765 if (unlikely(error))
1766 return ERR_PTR(error);
1767 }
1768
1769 if (unlikely(nd->flags & LOOKUP_NO_SYMLINKS) ||
1770 unlikely(link->mnt->mnt_flags & MNT_NOSYMFOLLOW))
1771 return ERR_PTR(-ELOOP);
1772
1773 if (!(nd->flags & LOOKUP_RCU)) {
1774 touch_atime(&last->link);
1775 cond_resched();
1776 } else if (atime_needs_update(&last->link, inode)) {
1777 if (!try_to_unlazy(nd))
1778 return ERR_PTR(-ECHILD);
1779 touch_atime(&last->link);
1780 }
1781
1782 error = security_inode_follow_link(link->dentry, inode,
1783 nd->flags & LOOKUP_RCU);
1784 if (unlikely(error))
1785 return ERR_PTR(error);
1786
1787 res = READ_ONCE(inode->i_link);
1788 if (!res) {
1789 const char * (*get)(struct dentry *, struct inode *,
1790 struct delayed_call *);
1791 get = inode->i_op->get_link;
1792 if (nd->flags & LOOKUP_RCU) {
1793 res = get(NULL, inode, &last->done);
1794 if (res == ERR_PTR(-ECHILD) && try_to_unlazy(nd))
1795 res = get(link->dentry, inode, &last->done);
1796 } else {
1797 res = get(link->dentry, inode, &last->done);
1798 }
1799 if (!res)
1800 goto all_done;
1801 if (IS_ERR(res))
1802 return res;
1803 }
1804 if (*res == '/') {
1805 error = nd_jump_root(nd);
1806 if (unlikely(error))
1807 return ERR_PTR(error);
1808 while (unlikely(*++res == '/'))
1809 ;
1810 }
1811 if (*res)
1812 return res;
1813all_done: // pure jump
1814 put_link(nd);
1815 return NULL;
1816}
1817
1818/*
1819 * Do we need to follow links? We _really_ want to be able
1820 * to do this check without having to look at inode->i_op,
1821 * so we keep a cache of "no, this doesn't need follow_link"
1822 * for the common case.
1823 *
1824 * NOTE: dentry must be what nd->next_seq had been sampled from.
1825 */
1826static const char *step_into(struct nameidata *nd, int flags,
1827 struct dentry *dentry)
1828{
1829 struct path path;
1830 struct inode *inode;
1831 int err = handle_mounts(nd, dentry, &path);
1832
1833 if (err < 0)
1834 return ERR_PTR(err);
1835 inode = path.dentry->d_inode;
1836 if (likely(!d_is_symlink(path.dentry)) ||
1837 ((flags & WALK_TRAILING) && !(nd->flags & LOOKUP_FOLLOW)) ||
1838 (flags & WALK_NOFOLLOW)) {
1839 /* not a symlink or should not follow */
1840 if (nd->flags & LOOKUP_RCU) {
1841 if (read_seqcount_retry(&path.dentry->d_seq, nd->next_seq))
1842 return ERR_PTR(-ECHILD);
1843 if (unlikely(!inode))
1844 return ERR_PTR(-ENOENT);
1845 } else {
1846 dput(nd->path.dentry);
1847 if (nd->path.mnt != path.mnt)
1848 mntput(nd->path.mnt);
1849 }
1850 nd->path = path;
1851 nd->inode = inode;
1852 nd->seq = nd->next_seq;
1853 return NULL;
1854 }
1855 if (nd->flags & LOOKUP_RCU) {
1856 /* make sure that d_is_symlink above matches inode */
1857 if (read_seqcount_retry(&path.dentry->d_seq, nd->next_seq))
1858 return ERR_PTR(-ECHILD);
1859 } else {
1860 if (path.mnt == nd->path.mnt)
1861 mntget(path.mnt);
1862 }
1863 return pick_link(nd, &path, inode, flags);
1864}
1865
1866static struct dentry *follow_dotdot_rcu(struct nameidata *nd)
1867{
1868 struct dentry *parent, *old;
1869
1870 if (path_equal(&nd->path, &nd->root))
1871 goto in_root;
1872 if (unlikely(nd->path.dentry == nd->path.mnt->mnt_root)) {
1873 struct path path;
1874 unsigned seq;
1875 if (!choose_mountpoint_rcu(real_mount(nd->path.mnt),
1876 &nd->root, &path, &seq))
1877 goto in_root;
1878 if (unlikely(nd->flags & LOOKUP_NO_XDEV))
1879 return ERR_PTR(-ECHILD);
1880 nd->path = path;
1881 nd->inode = path.dentry->d_inode;
1882 nd->seq = seq;
1883 // makes sure that non-RCU pathwalk could reach this state
1884 if (read_seqretry(&mount_lock, nd->m_seq))
1885 return ERR_PTR(-ECHILD);
1886 /* we know that mountpoint was pinned */
1887 }
1888 old = nd->path.dentry;
1889 parent = old->d_parent;
1890 nd->next_seq = read_seqcount_begin(&parent->d_seq);
1891 // makes sure that non-RCU pathwalk could reach this state
1892 if (read_seqcount_retry(&old->d_seq, nd->seq))
1893 return ERR_PTR(-ECHILD);
1894 if (unlikely(!path_connected(nd->path.mnt, parent)))
1895 return ERR_PTR(-ECHILD);
1896 return parent;
1897in_root:
1898 if (read_seqretry(&mount_lock, nd->m_seq))
1899 return ERR_PTR(-ECHILD);
1900 if (unlikely(nd->flags & LOOKUP_BENEATH))
1901 return ERR_PTR(-ECHILD);
1902 nd->next_seq = nd->seq;
1903 return nd->path.dentry;
1904}
1905
1906static struct dentry *follow_dotdot(struct nameidata *nd)
1907{
1908 struct dentry *parent;
1909
1910 if (path_equal(&nd->path, &nd->root))
1911 goto in_root;
1912 if (unlikely(nd->path.dentry == nd->path.mnt->mnt_root)) {
1913 struct path path;
1914
1915 if (!choose_mountpoint(real_mount(nd->path.mnt),
1916 &nd->root, &path))
1917 goto in_root;
1918 path_put(&nd->path);
1919 nd->path = path;
1920 nd->inode = path.dentry->d_inode;
1921 if (unlikely(nd->flags & LOOKUP_NO_XDEV))
1922 return ERR_PTR(-EXDEV);
1923 }
1924 /* rare case of legitimate dget_parent()... */
1925 parent = dget_parent(nd->path.dentry);
1926 if (unlikely(!path_connected(nd->path.mnt, parent))) {
1927 dput(parent);
1928 return ERR_PTR(-ENOENT);
1929 }
1930 return parent;
1931
1932in_root:
1933 if (unlikely(nd->flags & LOOKUP_BENEATH))
1934 return ERR_PTR(-EXDEV);
1935 return dget(nd->path.dentry);
1936}
1937
1938static const char *handle_dots(struct nameidata *nd, int type)
1939{
1940 if (type == LAST_DOTDOT) {
1941 const char *error = NULL;
1942 struct dentry *parent;
1943
1944 if (!nd->root.mnt) {
1945 error = ERR_PTR(set_root(nd));
1946 if (error)
1947 return error;
1948 }
1949 if (nd->flags & LOOKUP_RCU)
1950 parent = follow_dotdot_rcu(nd);
1951 else
1952 parent = follow_dotdot(nd);
1953 if (IS_ERR(parent))
1954 return ERR_CAST(parent);
1955 error = step_into(nd, WALK_NOFOLLOW, parent);
1956 if (unlikely(error))
1957 return error;
1958
1959 if (unlikely(nd->flags & LOOKUP_IS_SCOPED)) {
1960 /*
1961 * If there was a racing rename or mount along our
1962 * path, then we can't be sure that ".." hasn't jumped
1963 * above nd->root (and so userspace should retry or use
1964 * some fallback).
1965 */
1966 smp_rmb();
1967 if (__read_seqcount_retry(&mount_lock.seqcount, nd->m_seq))
1968 return ERR_PTR(-EAGAIN);
1969 if (__read_seqcount_retry(&rename_lock.seqcount, nd->r_seq))
1970 return ERR_PTR(-EAGAIN);
1971 }
1972 }
1973 return NULL;
1974}
1975
1976static const char *walk_component(struct nameidata *nd, int flags)
1977{
1978 struct dentry *dentry;
1979 /*
1980 * "." and ".." are special - ".." especially so because it has
1981 * to be able to know about the current root directory and
1982 * parent relationships.
1983 */
1984 if (unlikely(nd->last_type != LAST_NORM)) {
1985 if (!(flags & WALK_MORE) && nd->depth)
1986 put_link(nd);
1987 return handle_dots(nd, nd->last_type);
1988 }
1989 dentry = lookup_fast(nd);
1990 if (IS_ERR(dentry))
1991 return ERR_CAST(dentry);
1992 if (unlikely(!dentry)) {
1993 dentry = lookup_slow(&nd->last, nd->path.dentry, nd->flags);
1994 if (IS_ERR(dentry))
1995 return ERR_CAST(dentry);
1996 }
1997 if (!(flags & WALK_MORE) && nd->depth)
1998 put_link(nd);
1999 return step_into(nd, flags, dentry);
2000}
2001
2002/*
2003 * We can do the critical dentry name comparison and hashing
2004 * operations one word at a time, but we are limited to:
2005 *
2006 * - Architectures with fast unaligned word accesses. We could
2007 * do a "get_unaligned()" if this helps and is sufficiently
2008 * fast.
2009 *
2010 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
2011 * do not trap on the (extremely unlikely) case of a page
2012 * crossing operation.
2013 *
2014 * - Furthermore, we need an efficient 64-bit compile for the
2015 * 64-bit case in order to generate the "number of bytes in
2016 * the final mask". Again, that could be replaced with a
2017 * efficient population count instruction or similar.
2018 */
2019#ifdef CONFIG_DCACHE_WORD_ACCESS
2020
2021#include <asm/word-at-a-time.h>
2022
2023#ifdef HASH_MIX
2024
2025/* Architecture provides HASH_MIX and fold_hash() in <asm/hash.h> */
2026
2027#elif defined(CONFIG_64BIT)
2028/*
2029 * Register pressure in the mixing function is an issue, particularly
2030 * on 32-bit x86, but almost any function requires one state value and
2031 * one temporary. Instead, use a function designed for two state values
2032 * and no temporaries.
2033 *
2034 * This function cannot create a collision in only two iterations, so
2035 * we have two iterations to achieve avalanche. In those two iterations,
2036 * we have six layers of mixing, which is enough to spread one bit's
2037 * influence out to 2^6 = 64 state bits.
2038 *
2039 * Rotate constants are scored by considering either 64 one-bit input
2040 * deltas or 64*63/2 = 2016 two-bit input deltas, and finding the
2041 * probability of that delta causing a change to each of the 128 output
2042 * bits, using a sample of random initial states.
2043 *
2044 * The Shannon entropy of the computed probabilities is then summed
2045 * to produce a score. Ideally, any input change has a 50% chance of
2046 * toggling any given output bit.
2047 *
2048 * Mixing scores (in bits) for (12,45):
2049 * Input delta: 1-bit 2-bit
2050 * 1 round: 713.3 42542.6
2051 * 2 rounds: 2753.7 140389.8
2052 * 3 rounds: 5954.1 233458.2
2053 * 4 rounds: 7862.6 256672.2
2054 * Perfect: 8192 258048
2055 * (64*128) (64*63/2 * 128)
2056 */
2057#define HASH_MIX(x, y, a) \
2058 ( x ^= (a), \
2059 y ^= x, x = rol64(x,12),\
2060 x += y, y = rol64(y,45),\
2061 y *= 9 )
2062
2063/*
2064 * Fold two longs into one 32-bit hash value. This must be fast, but
2065 * latency isn't quite as critical, as there is a fair bit of additional
2066 * work done before the hash value is used.
2067 */
2068static inline unsigned int fold_hash(unsigned long x, unsigned long y)
2069{
2070 y ^= x * GOLDEN_RATIO_64;
2071 y *= GOLDEN_RATIO_64;
2072 return y >> 32;
2073}
2074
2075#else /* 32-bit case */
2076
2077/*
2078 * Mixing scores (in bits) for (7,20):
2079 * Input delta: 1-bit 2-bit
2080 * 1 round: 330.3 9201.6
2081 * 2 rounds: 1246.4 25475.4
2082 * 3 rounds: 1907.1 31295.1
2083 * 4 rounds: 2042.3 31718.6
2084 * Perfect: 2048 31744
2085 * (32*64) (32*31/2 * 64)
2086 */
2087#define HASH_MIX(x, y, a) \
2088 ( x ^= (a), \
2089 y ^= x, x = rol32(x, 7),\
2090 x += y, y = rol32(y,20),\
2091 y *= 9 )
2092
2093static inline unsigned int fold_hash(unsigned long x, unsigned long y)
2094{
2095 /* Use arch-optimized multiply if one exists */
2096 return __hash_32(y ^ __hash_32(x));
2097}
2098
2099#endif
2100
2101/*
2102 * Return the hash of a string of known length. This is carfully
2103 * designed to match hash_name(), which is the more critical function.
2104 * In particular, we must end by hashing a final word containing 0..7
2105 * payload bytes, to match the way that hash_name() iterates until it
2106 * finds the delimiter after the name.
2107 */
2108unsigned int full_name_hash(const void *salt, const char *name, unsigned int len)
2109{
2110 unsigned long a, x = 0, y = (unsigned long)salt;
2111
2112 for (;;) {
2113 if (!len)
2114 goto done;
2115 a = load_unaligned_zeropad(name);
2116 if (len < sizeof(unsigned long))
2117 break;
2118 HASH_MIX(x, y, a);
2119 name += sizeof(unsigned long);
2120 len -= sizeof(unsigned long);
2121 }
2122 x ^= a & bytemask_from_count(len);
2123done:
2124 return fold_hash(x, y);
2125}
2126EXPORT_SYMBOL(full_name_hash);
2127
2128/* Return the "hash_len" (hash and length) of a null-terminated string */
2129u64 hashlen_string(const void *salt, const char *name)
2130{
2131 unsigned long a = 0, x = 0, y = (unsigned long)salt;
2132 unsigned long adata, mask, len;
2133 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
2134
2135 len = 0;
2136 goto inside;
2137
2138 do {
2139 HASH_MIX(x, y, a);
2140 len += sizeof(unsigned long);
2141inside:
2142 a = load_unaligned_zeropad(name+len);
2143 } while (!has_zero(a, &adata, &constants));
2144
2145 adata = prep_zero_mask(a, adata, &constants);
2146 mask = create_zero_mask(adata);
2147 x ^= a & zero_bytemask(mask);
2148
2149 return hashlen_create(fold_hash(x, y), len + find_zero(mask));
2150}
2151EXPORT_SYMBOL(hashlen_string);
2152
2153/*
2154 * Calculate the length and hash of the path component, and
2155 * return the "hash_len" as the result.
2156 */
2157static inline u64 hash_name(const void *salt, const char *name)
2158{
2159 unsigned long a = 0, b, x = 0, y = (unsigned long)salt;
2160 unsigned long adata, bdata, mask, len;
2161 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
2162
2163 len = 0;
2164 goto inside;
2165
2166 do {
2167 HASH_MIX(x, y, a);
2168 len += sizeof(unsigned long);
2169inside:
2170 a = load_unaligned_zeropad(name+len);
2171 b = a ^ REPEAT_BYTE('/');
2172 } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants)));
2173
2174 adata = prep_zero_mask(a, adata, &constants);
2175 bdata = prep_zero_mask(b, bdata, &constants);
2176 mask = create_zero_mask(adata | bdata);
2177 x ^= a & zero_bytemask(mask);
2178
2179 return hashlen_create(fold_hash(x, y), len + find_zero(mask));
2180}
2181
2182#else /* !CONFIG_DCACHE_WORD_ACCESS: Slow, byte-at-a-time version */
2183
2184/* Return the hash of a string of known length */
2185unsigned int full_name_hash(const void *salt, const char *name, unsigned int len)
2186{
2187 unsigned long hash = init_name_hash(salt);
2188 while (len--)
2189 hash = partial_name_hash((unsigned char)*name++, hash);
2190 return end_name_hash(hash);
2191}
2192EXPORT_SYMBOL(full_name_hash);
2193
2194/* Return the "hash_len" (hash and length) of a null-terminated string */
2195u64 hashlen_string(const void *salt, const char *name)
2196{
2197 unsigned long hash = init_name_hash(salt);
2198 unsigned long len = 0, c;
2199
2200 c = (unsigned char)*name;
2201 while (c) {
2202 len++;
2203 hash = partial_name_hash(c, hash);
2204 c = (unsigned char)name[len];
2205 }
2206 return hashlen_create(end_name_hash(hash), len);
2207}
2208EXPORT_SYMBOL(hashlen_string);
2209
2210/*
2211 * We know there's a real path component here of at least
2212 * one character.
2213 */
2214static inline u64 hash_name(const void *salt, const char *name)
2215{
2216 unsigned long hash = init_name_hash(salt);
2217 unsigned long len = 0, c;
2218
2219 c = (unsigned char)*name;
2220 do {
2221 len++;
2222 hash = partial_name_hash(c, hash);
2223 c = (unsigned char)name[len];
2224 } while (c && c != '/');
2225 return hashlen_create(end_name_hash(hash), len);
2226}
2227
2228#endif
2229
2230/*
2231 * Name resolution.
2232 * This is the basic name resolution function, turning a pathname into
2233 * the final dentry. We expect 'base' to be positive and a directory.
2234 *
2235 * Returns 0 and nd will have valid dentry and mnt on success.
2236 * Returns error and drops reference to input namei data on failure.
2237 */
2238static int link_path_walk(const char *name, struct nameidata *nd)
2239{
2240 int depth = 0; // depth <= nd->depth
2241 int err;
2242
2243 nd->last_type = LAST_ROOT;
2244 nd->flags |= LOOKUP_PARENT;
2245 if (IS_ERR(name))
2246 return PTR_ERR(name);
2247 while (*name=='/')
2248 name++;
2249 if (!*name) {
2250 nd->dir_mode = 0; // short-circuit the 'hardening' idiocy
2251 return 0;
2252 }
2253
2254 /* At this point we know we have a real path component. */
2255 for(;;) {
2256 struct user_namespace *mnt_userns;
2257 const char *link;
2258 u64 hash_len;
2259 int type;
2260
2261 mnt_userns = mnt_user_ns(nd->path.mnt);
2262 err = may_lookup(mnt_userns, nd);
2263 if (err)
2264 return err;
2265
2266 hash_len = hash_name(nd->path.dentry, name);
2267
2268 type = LAST_NORM;
2269 if (name[0] == '.') switch (hashlen_len(hash_len)) {
2270 case 2:
2271 if (name[1] == '.') {
2272 type = LAST_DOTDOT;
2273 nd->state |= ND_JUMPED;
2274 }
2275 break;
2276 case 1:
2277 type = LAST_DOT;
2278 }
2279 if (likely(type == LAST_NORM)) {
2280 struct dentry *parent = nd->path.dentry;
2281 nd->state &= ~ND_JUMPED;
2282 if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
2283 struct qstr this = { { .hash_len = hash_len }, .name = name };
2284 err = parent->d_op->d_hash(parent, &this);
2285 if (err < 0)
2286 return err;
2287 hash_len = this.hash_len;
2288 name = this.name;
2289 }
2290 }
2291
2292 nd->last.hash_len = hash_len;
2293 nd->last.name = name;
2294 nd->last_type = type;
2295
2296 name += hashlen_len(hash_len);
2297 if (!*name)
2298 goto OK;
2299 /*
2300 * If it wasn't NUL, we know it was '/'. Skip that
2301 * slash, and continue until no more slashes.
2302 */
2303 do {
2304 name++;
2305 } while (unlikely(*name == '/'));
2306 if (unlikely(!*name)) {
2307OK:
2308 /* pathname or trailing symlink, done */
2309 if (!depth) {
2310 nd->dir_vfsuid = i_uid_into_vfsuid(mnt_userns, nd->inode);
2311 nd->dir_mode = nd->inode->i_mode;
2312 nd->flags &= ~LOOKUP_PARENT;
2313 return 0;
2314 }
2315 /* last component of nested symlink */
2316 name = nd->stack[--depth].name;
2317 link = walk_component(nd, 0);
2318 } else {
2319 /* not the last component */
2320 link = walk_component(nd, WALK_MORE);
2321 }
2322 if (unlikely(link)) {
2323 if (IS_ERR(link))
2324 return PTR_ERR(link);
2325 /* a symlink to follow */
2326 nd->stack[depth++].name = name;
2327 name = link;
2328 continue;
2329 }
2330 if (unlikely(!d_can_lookup(nd->path.dentry))) {
2331 if (nd->flags & LOOKUP_RCU) {
2332 if (!try_to_unlazy(nd))
2333 return -ECHILD;
2334 }
2335 return -ENOTDIR;
2336 }
2337 }
2338}
2339
2340/* must be paired with terminate_walk() */
2341static const char *path_init(struct nameidata *nd, unsigned flags)
2342{
2343 int error;
2344 const char *s = nd->name->name;
2345
2346 /* LOOKUP_CACHED requires RCU, ask caller to retry */
2347 if ((flags & (LOOKUP_RCU | LOOKUP_CACHED)) == LOOKUP_CACHED)
2348 return ERR_PTR(-EAGAIN);
2349
2350 if (!*s)
2351 flags &= ~LOOKUP_RCU;
2352 if (flags & LOOKUP_RCU)
2353 rcu_read_lock();
2354 else
2355 nd->seq = nd->next_seq = 0;
2356
2357 nd->flags = flags;
2358 nd->state |= ND_JUMPED;
2359
2360 nd->m_seq = __read_seqcount_begin(&mount_lock.seqcount);
2361 nd->r_seq = __read_seqcount_begin(&rename_lock.seqcount);
2362 smp_rmb();
2363
2364 if (nd->state & ND_ROOT_PRESET) {
2365 struct dentry *root = nd->root.dentry;
2366 struct inode *inode = root->d_inode;
2367 if (*s && unlikely(!d_can_lookup(root)))
2368 return ERR_PTR(-ENOTDIR);
2369 nd->path = nd->root;
2370 nd->inode = inode;
2371 if (flags & LOOKUP_RCU) {
2372 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
2373 nd->root_seq = nd->seq;
2374 } else {
2375 path_get(&nd->path);
2376 }
2377 return s;
2378 }
2379
2380 nd->root.mnt = NULL;
2381
2382 /* Absolute pathname -- fetch the root (LOOKUP_IN_ROOT uses nd->dfd). */
2383 if (*s == '/' && !(flags & LOOKUP_IN_ROOT)) {
2384 error = nd_jump_root(nd);
2385 if (unlikely(error))
2386 return ERR_PTR(error);
2387 return s;
2388 }
2389
2390 /* Relative pathname -- get the starting-point it is relative to. */
2391 if (nd->dfd == AT_FDCWD) {
2392 if (flags & LOOKUP_RCU) {
2393 struct fs_struct *fs = current->fs;
2394 unsigned seq;
2395
2396 do {
2397 seq = read_seqcount_begin(&fs->seq);
2398 nd->path = fs->pwd;
2399 nd->inode = nd->path.dentry->d_inode;
2400 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
2401 } while (read_seqcount_retry(&fs->seq, seq));
2402 } else {
2403 get_fs_pwd(current->fs, &nd->path);
2404 nd->inode = nd->path.dentry->d_inode;
2405 }
2406 } else {
2407 /* Caller must check execute permissions on the starting path component */
2408 struct fd f = fdget_raw(nd->dfd);
2409 struct dentry *dentry;
2410
2411 if (!f.file)
2412 return ERR_PTR(-EBADF);
2413
2414 dentry = f.file->f_path.dentry;
2415
2416 if (*s && unlikely(!d_can_lookup(dentry))) {
2417 fdput(f);
2418 return ERR_PTR(-ENOTDIR);
2419 }
2420
2421 nd->path = f.file->f_path;
2422 if (flags & LOOKUP_RCU) {
2423 nd->inode = nd->path.dentry->d_inode;
2424 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
2425 } else {
2426 path_get(&nd->path);
2427 nd->inode = nd->path.dentry->d_inode;
2428 }
2429 fdput(f);
2430 }
2431
2432 /* For scoped-lookups we need to set the root to the dirfd as well. */
2433 if (flags & LOOKUP_IS_SCOPED) {
2434 nd->root = nd->path;
2435 if (flags & LOOKUP_RCU) {
2436 nd->root_seq = nd->seq;
2437 } else {
2438 path_get(&nd->root);
2439 nd->state |= ND_ROOT_GRABBED;
2440 }
2441 }
2442 return s;
2443}
2444
2445static inline const char *lookup_last(struct nameidata *nd)
2446{
2447 if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
2448 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
2449
2450 return walk_component(nd, WALK_TRAILING);
2451}
2452
2453static int handle_lookup_down(struct nameidata *nd)
2454{
2455 if (!(nd->flags & LOOKUP_RCU))
2456 dget(nd->path.dentry);
2457 nd->next_seq = nd->seq;
2458 return PTR_ERR(step_into(nd, WALK_NOFOLLOW, nd->path.dentry));
2459}
2460
2461/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
2462static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path)
2463{
2464 const char *s = path_init(nd, flags);
2465 int err;
2466
2467 if (unlikely(flags & LOOKUP_DOWN) && !IS_ERR(s)) {
2468 err = handle_lookup_down(nd);
2469 if (unlikely(err < 0))
2470 s = ERR_PTR(err);
2471 }
2472
2473 while (!(err = link_path_walk(s, nd)) &&
2474 (s = lookup_last(nd)) != NULL)
2475 ;
2476 if (!err && unlikely(nd->flags & LOOKUP_MOUNTPOINT)) {
2477 err = handle_lookup_down(nd);
2478 nd->state &= ~ND_JUMPED; // no d_weak_revalidate(), please...
2479 }
2480 if (!err)
2481 err = complete_walk(nd);
2482
2483 if (!err && nd->flags & LOOKUP_DIRECTORY)
2484 if (!d_can_lookup(nd->path.dentry))
2485 err = -ENOTDIR;
2486 if (!err) {
2487 *path = nd->path;
2488 nd->path.mnt = NULL;
2489 nd->path.dentry = NULL;
2490 }
2491 terminate_walk(nd);
2492 return err;
2493}
2494
2495int filename_lookup(int dfd, struct filename *name, unsigned flags,
2496 struct path *path, struct path *root)
2497{
2498 int retval;
2499 struct nameidata nd;
2500 if (IS_ERR(name))
2501 return PTR_ERR(name);
2502 set_nameidata(&nd, dfd, name, root);
2503 retval = path_lookupat(&nd, flags | LOOKUP_RCU, path);
2504 if (unlikely(retval == -ECHILD))
2505 retval = path_lookupat(&nd, flags, path);
2506 if (unlikely(retval == -ESTALE))
2507 retval = path_lookupat(&nd, flags | LOOKUP_REVAL, path);
2508
2509 if (likely(!retval))
2510 audit_inode(name, path->dentry,
2511 flags & LOOKUP_MOUNTPOINT ? AUDIT_INODE_NOEVAL : 0);
2512 restore_nameidata();
2513 return retval;
2514}
2515
2516/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
2517static int path_parentat(struct nameidata *nd, unsigned flags,
2518 struct path *parent)
2519{
2520 const char *s = path_init(nd, flags);
2521 int err = link_path_walk(s, nd);
2522 if (!err)
2523 err = complete_walk(nd);
2524 if (!err) {
2525 *parent = nd->path;
2526 nd->path.mnt = NULL;
2527 nd->path.dentry = NULL;
2528 }
2529 terminate_walk(nd);
2530 return err;
2531}
2532
2533/* Note: this does not consume "name" */
2534static int filename_parentat(int dfd, struct filename *name,
2535 unsigned int flags, struct path *parent,
2536 struct qstr *last, int *type)
2537{
2538 int retval;
2539 struct nameidata nd;
2540
2541 if (IS_ERR(name))
2542 return PTR_ERR(name);
2543 set_nameidata(&nd, dfd, name, NULL);
2544 retval = path_parentat(&nd, flags | LOOKUP_RCU, parent);
2545 if (unlikely(retval == -ECHILD))
2546 retval = path_parentat(&nd, flags, parent);
2547 if (unlikely(retval == -ESTALE))
2548 retval = path_parentat(&nd, flags | LOOKUP_REVAL, parent);
2549 if (likely(!retval)) {
2550 *last = nd.last;
2551 *type = nd.last_type;
2552 audit_inode(name, parent->dentry, AUDIT_INODE_PARENT);
2553 }
2554 restore_nameidata();
2555 return retval;
2556}
2557
2558/* does lookup, returns the object with parent locked */
2559static struct dentry *__kern_path_locked(struct filename *name, struct path *path)
2560{
2561 struct dentry *d;
2562 struct qstr last;
2563 int type, error;
2564
2565 error = filename_parentat(AT_FDCWD, name, 0, path, &last, &type);
2566 if (error)
2567 return ERR_PTR(error);
2568 if (unlikely(type != LAST_NORM)) {
2569 path_put(path);
2570 return ERR_PTR(-EINVAL);
2571 }
2572 inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
2573 d = __lookup_hash(&last, path->dentry, 0);
2574 if (IS_ERR(d)) {
2575 inode_unlock(path->dentry->d_inode);
2576 path_put(path);
2577 }
2578 return d;
2579}
2580
2581struct dentry *kern_path_locked(const char *name, struct path *path)
2582{
2583 struct filename *filename = getname_kernel(name);
2584 struct dentry *res = __kern_path_locked(filename, path);
2585
2586 putname(filename);
2587 return res;
2588}
2589
2590int kern_path(const char *name, unsigned int flags, struct path *path)
2591{
2592 struct filename *filename = getname_kernel(name);
2593 int ret = filename_lookup(AT_FDCWD, filename, flags, path, NULL);
2594
2595 putname(filename);
2596 return ret;
2597
2598}
2599EXPORT_SYMBOL(kern_path);
2600
2601/**
2602 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
2603 * @dentry: pointer to dentry of the base directory
2604 * @mnt: pointer to vfs mount of the base directory
2605 * @name: pointer to file name
2606 * @flags: lookup flags
2607 * @path: pointer to struct path to fill
2608 */
2609int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
2610 const char *name, unsigned int flags,
2611 struct path *path)
2612{
2613 struct filename *filename;
2614 struct path root = {.mnt = mnt, .dentry = dentry};
2615 int ret;
2616
2617 filename = getname_kernel(name);
2618 /* the first argument of filename_lookup() is ignored with root */
2619 ret = filename_lookup(AT_FDCWD, filename, flags, path, &root);
2620 putname(filename);
2621 return ret;
2622}
2623EXPORT_SYMBOL(vfs_path_lookup);
2624
2625static int lookup_one_common(struct user_namespace *mnt_userns,
2626 const char *name, struct dentry *base, int len,
2627 struct qstr *this)
2628{
2629 this->name = name;
2630 this->len = len;
2631 this->hash = full_name_hash(base, name, len);
2632 if (!len)
2633 return -EACCES;
2634
2635 if (unlikely(name[0] == '.')) {
2636 if (len < 2 || (len == 2 && name[1] == '.'))
2637 return -EACCES;
2638 }
2639
2640 while (len--) {
2641 unsigned int c = *(const unsigned char *)name++;
2642 if (c == '/' || c == '\0')
2643 return -EACCES;
2644 }
2645 /*
2646 * See if the low-level filesystem might want
2647 * to use its own hash..
2648 */
2649 if (base->d_flags & DCACHE_OP_HASH) {
2650 int err = base->d_op->d_hash(base, this);
2651 if (err < 0)
2652 return err;
2653 }
2654
2655 return inode_permission(mnt_userns, base->d_inode, MAY_EXEC);
2656}
2657
2658/**
2659 * try_lookup_one_len - filesystem helper to lookup single pathname component
2660 * @name: pathname component to lookup
2661 * @base: base directory to lookup from
2662 * @len: maximum length @len should be interpreted to
2663 *
2664 * Look up a dentry by name in the dcache, returning NULL if it does not
2665 * currently exist. The function does not try to create a dentry.
2666 *
2667 * Note that this routine is purely a helper for filesystem usage and should
2668 * not be called by generic code.
2669 *
2670 * The caller must hold base->i_mutex.
2671 */
2672struct dentry *try_lookup_one_len(const char *name, struct dentry *base, int len)
2673{
2674 struct qstr this;
2675 int err;
2676
2677 WARN_ON_ONCE(!inode_is_locked(base->d_inode));
2678
2679 err = lookup_one_common(&init_user_ns, name, base, len, &this);
2680 if (err)
2681 return ERR_PTR(err);
2682
2683 return lookup_dcache(&this, base, 0);
2684}
2685EXPORT_SYMBOL(try_lookup_one_len);
2686
2687/**
2688 * lookup_one_len - filesystem helper to lookup single pathname component
2689 * @name: pathname component to lookup
2690 * @base: base directory to lookup from
2691 * @len: maximum length @len should be interpreted to
2692 *
2693 * Note that this routine is purely a helper for filesystem usage and should
2694 * not be called by generic code.
2695 *
2696 * The caller must hold base->i_mutex.
2697 */
2698struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
2699{
2700 struct dentry *dentry;
2701 struct qstr this;
2702 int err;
2703
2704 WARN_ON_ONCE(!inode_is_locked(base->d_inode));
2705
2706 err = lookup_one_common(&init_user_ns, name, base, len, &this);
2707 if (err)
2708 return ERR_PTR(err);
2709
2710 dentry = lookup_dcache(&this, base, 0);
2711 return dentry ? dentry : __lookup_slow(&this, base, 0);
2712}
2713EXPORT_SYMBOL(lookup_one_len);
2714
2715/**
2716 * lookup_one - filesystem helper to lookup single pathname component
2717 * @mnt_userns: user namespace of the mount the lookup is performed from
2718 * @name: pathname component to lookup
2719 * @base: base directory to lookup from
2720 * @len: maximum length @len should be interpreted to
2721 *
2722 * Note that this routine is purely a helper for filesystem usage and should
2723 * not be called by generic code.
2724 *
2725 * The caller must hold base->i_mutex.
2726 */
2727struct dentry *lookup_one(struct user_namespace *mnt_userns, const char *name,
2728 struct dentry *base, int len)
2729{
2730 struct dentry *dentry;
2731 struct qstr this;
2732 int err;
2733
2734 WARN_ON_ONCE(!inode_is_locked(base->d_inode));
2735
2736 err = lookup_one_common(mnt_userns, name, base, len, &this);
2737 if (err)
2738 return ERR_PTR(err);
2739
2740 dentry = lookup_dcache(&this, base, 0);
2741 return dentry ? dentry : __lookup_slow(&this, base, 0);
2742}
2743EXPORT_SYMBOL(lookup_one);
2744
2745/**
2746 * lookup_one_unlocked - filesystem helper to lookup single pathname component
2747 * @mnt_userns: idmapping of the mount the lookup is performed from
2748 * @name: pathname component to lookup
2749 * @base: base directory to lookup from
2750 * @len: maximum length @len should be interpreted to
2751 *
2752 * Note that this routine is purely a helper for filesystem usage and should
2753 * not be called by generic code.
2754 *
2755 * Unlike lookup_one_len, it should be called without the parent
2756 * i_mutex held, and will take the i_mutex itself if necessary.
2757 */
2758struct dentry *lookup_one_unlocked(struct user_namespace *mnt_userns,
2759 const char *name, struct dentry *base,
2760 int len)
2761{
2762 struct qstr this;
2763 int err;
2764 struct dentry *ret;
2765
2766 err = lookup_one_common(mnt_userns, name, base, len, &this);
2767 if (err)
2768 return ERR_PTR(err);
2769
2770 ret = lookup_dcache(&this, base, 0);
2771 if (!ret)
2772 ret = lookup_slow(&this, base, 0);
2773 return ret;
2774}
2775EXPORT_SYMBOL(lookup_one_unlocked);
2776
2777/**
2778 * lookup_one_positive_unlocked - filesystem helper to lookup single
2779 * pathname component
2780 * @mnt_userns: idmapping of the mount the lookup is performed from
2781 * @name: pathname component to lookup
2782 * @base: base directory to lookup from
2783 * @len: maximum length @len should be interpreted to
2784 *
2785 * This helper will yield ERR_PTR(-ENOENT) on negatives. The helper returns
2786 * known positive or ERR_PTR(). This is what most of the users want.
2787 *
2788 * Note that pinned negative with unlocked parent _can_ become positive at any
2789 * time, so callers of lookup_one_unlocked() need to be very careful; pinned
2790 * positives have >d_inode stable, so this one avoids such problems.
2791 *
2792 * Note that this routine is purely a helper for filesystem usage and should
2793 * not be called by generic code.
2794 *
2795 * The helper should be called without i_mutex held.
2796 */
2797struct dentry *lookup_one_positive_unlocked(struct user_namespace *mnt_userns,
2798 const char *name,
2799 struct dentry *base, int len)
2800{
2801 struct dentry *ret = lookup_one_unlocked(mnt_userns, name, base, len);
2802
2803 if (!IS_ERR(ret) && d_flags_negative(smp_load_acquire(&ret->d_flags))) {
2804 dput(ret);
2805 ret = ERR_PTR(-ENOENT);
2806 }
2807 return ret;
2808}
2809EXPORT_SYMBOL(lookup_one_positive_unlocked);
2810
2811/**
2812 * lookup_one_len_unlocked - filesystem helper to lookup single pathname component
2813 * @name: pathname component to lookup
2814 * @base: base directory to lookup from
2815 * @len: maximum length @len should be interpreted to
2816 *
2817 * Note that this routine is purely a helper for filesystem usage and should
2818 * not be called by generic code.
2819 *
2820 * Unlike lookup_one_len, it should be called without the parent
2821 * i_mutex held, and will take the i_mutex itself if necessary.
2822 */
2823struct dentry *lookup_one_len_unlocked(const char *name,
2824 struct dentry *base, int len)
2825{
2826 return lookup_one_unlocked(&init_user_ns, name, base, len);
2827}
2828EXPORT_SYMBOL(lookup_one_len_unlocked);
2829
2830/*
2831 * Like lookup_one_len_unlocked(), except that it yields ERR_PTR(-ENOENT)
2832 * on negatives. Returns known positive or ERR_PTR(); that's what
2833 * most of the users want. Note that pinned negative with unlocked parent
2834 * _can_ become positive at any time, so callers of lookup_one_len_unlocked()
2835 * need to be very careful; pinned positives have ->d_inode stable, so
2836 * this one avoids such problems.
2837 */
2838struct dentry *lookup_positive_unlocked(const char *name,
2839 struct dentry *base, int len)
2840{
2841 return lookup_one_positive_unlocked(&init_user_ns, name, base, len);
2842}
2843EXPORT_SYMBOL(lookup_positive_unlocked);
2844
2845#ifdef CONFIG_UNIX98_PTYS
2846int path_pts(struct path *path)
2847{
2848 /* Find something mounted on "pts" in the same directory as
2849 * the input path.
2850 */
2851 struct dentry *parent = dget_parent(path->dentry);
2852 struct dentry *child;
2853 struct qstr this = QSTR_INIT("pts", 3);
2854
2855 if (unlikely(!path_connected(path->mnt, parent))) {
2856 dput(parent);
2857 return -ENOENT;
2858 }
2859 dput(path->dentry);
2860 path->dentry = parent;
2861 child = d_hash_and_lookup(parent, &this);
2862 if (!child)
2863 return -ENOENT;
2864
2865 path->dentry = child;
2866 dput(parent);
2867 follow_down(path);
2868 return 0;
2869}
2870#endif
2871
2872int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
2873 struct path *path, int *empty)
2874{
2875 struct filename *filename = getname_flags(name, flags, empty);
2876 int ret = filename_lookup(dfd, filename, flags, path, NULL);
2877
2878 putname(filename);
2879 return ret;
2880}
2881EXPORT_SYMBOL(user_path_at_empty);
2882
2883int __check_sticky(struct user_namespace *mnt_userns, struct inode *dir,
2884 struct inode *inode)
2885{
2886 kuid_t fsuid = current_fsuid();
2887
2888 if (vfsuid_eq_kuid(i_uid_into_vfsuid(mnt_userns, inode), fsuid))
2889 return 0;
2890 if (vfsuid_eq_kuid(i_uid_into_vfsuid(mnt_userns, dir), fsuid))
2891 return 0;
2892 return !capable_wrt_inode_uidgid(mnt_userns, inode, CAP_FOWNER);
2893}
2894EXPORT_SYMBOL(__check_sticky);
2895
2896/*
2897 * Check whether we can remove a link victim from directory dir, check
2898 * whether the type of victim is right.
2899 * 1. We can't do it if dir is read-only (done in permission())
2900 * 2. We should have write and exec permissions on dir
2901 * 3. We can't remove anything from append-only dir
2902 * 4. We can't do anything with immutable dir (done in permission())
2903 * 5. If the sticky bit on dir is set we should either
2904 * a. be owner of dir, or
2905 * b. be owner of victim, or
2906 * c. have CAP_FOWNER capability
2907 * 6. If the victim is append-only or immutable we can't do antyhing with
2908 * links pointing to it.
2909 * 7. If the victim has an unknown uid or gid we can't change the inode.
2910 * 8. If we were asked to remove a directory and victim isn't one - ENOTDIR.
2911 * 9. If we were asked to remove a non-directory and victim isn't one - EISDIR.
2912 * 10. We can't remove a root or mountpoint.
2913 * 11. We don't allow removal of NFS sillyrenamed files; it's handled by
2914 * nfs_async_unlink().
2915 */
2916static int may_delete(struct user_namespace *mnt_userns, struct inode *dir,
2917 struct dentry *victim, bool isdir)
2918{
2919 struct inode *inode = d_backing_inode(victim);
2920 int error;
2921
2922 if (d_is_negative(victim))
2923 return -ENOENT;
2924 BUG_ON(!inode);
2925
2926 BUG_ON(victim->d_parent->d_inode != dir);
2927
2928 /* Inode writeback is not safe when the uid or gid are invalid. */
2929 if (!vfsuid_valid(i_uid_into_vfsuid(mnt_userns, inode)) ||
2930 !vfsgid_valid(i_gid_into_vfsgid(mnt_userns, inode)))
2931 return -EOVERFLOW;
2932
2933 audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE);
2934
2935 error = inode_permission(mnt_userns, dir, MAY_WRITE | MAY_EXEC);
2936 if (error)
2937 return error;
2938 if (IS_APPEND(dir))
2939 return -EPERM;
2940
2941 if (check_sticky(mnt_userns, dir, inode) || IS_APPEND(inode) ||
2942 IS_IMMUTABLE(inode) || IS_SWAPFILE(inode) ||
2943 HAS_UNMAPPED_ID(mnt_userns, inode))
2944 return -EPERM;
2945 if (isdir) {
2946 if (!d_is_dir(victim))
2947 return -ENOTDIR;
2948 if (IS_ROOT(victim))
2949 return -EBUSY;
2950 } else if (d_is_dir(victim))
2951 return -EISDIR;
2952 if (IS_DEADDIR(dir))
2953 return -ENOENT;
2954 if (victim->d_flags & DCACHE_NFSFS_RENAMED)
2955 return -EBUSY;
2956 return 0;
2957}
2958
2959/* Check whether we can create an object with dentry child in directory
2960 * dir.
2961 * 1. We can't do it if child already exists (open has special treatment for
2962 * this case, but since we are inlined it's OK)
2963 * 2. We can't do it if dir is read-only (done in permission())
2964 * 3. We can't do it if the fs can't represent the fsuid or fsgid.
2965 * 4. We should have write and exec permissions on dir
2966 * 5. We can't do it if dir is immutable (done in permission())
2967 */
2968static inline int may_create(struct user_namespace *mnt_userns,
2969 struct inode *dir, struct dentry *child)
2970{
2971 audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE);
2972 if (child->d_inode)
2973 return -EEXIST;
2974 if (IS_DEADDIR(dir))
2975 return -ENOENT;
2976 if (!fsuidgid_has_mapping(dir->i_sb, mnt_userns))
2977 return -EOVERFLOW;
2978
2979 return inode_permission(mnt_userns, dir, MAY_WRITE | MAY_EXEC);
2980}
2981
2982/*
2983 * p1 and p2 should be directories on the same fs.
2984 */
2985struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
2986{
2987 struct dentry *p;
2988
2989 if (p1 == p2) {
2990 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
2991 return NULL;
2992 }
2993
2994 mutex_lock(&p1->d_sb->s_vfs_rename_mutex);
2995
2996 p = d_ancestor(p2, p1);
2997 if (p) {
2998 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT);
2999 inode_lock_nested(p1->d_inode, I_MUTEX_CHILD);
3000 return p;
3001 }
3002
3003 p = d_ancestor(p1, p2);
3004 if (p) {
3005 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
3006 inode_lock_nested(p2->d_inode, I_MUTEX_CHILD);
3007 return p;
3008 }
3009
3010 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
3011 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT2);
3012 return NULL;
3013}
3014EXPORT_SYMBOL(lock_rename);
3015
3016void unlock_rename(struct dentry *p1, struct dentry *p2)
3017{
3018 inode_unlock(p1->d_inode);
3019 if (p1 != p2) {
3020 inode_unlock(p2->d_inode);
3021 mutex_unlock(&p1->d_sb->s_vfs_rename_mutex);
3022 }
3023}
3024EXPORT_SYMBOL(unlock_rename);
3025
3026/**
3027 * mode_strip_umask - handle vfs umask stripping
3028 * @dir: parent directory of the new inode
3029 * @mode: mode of the new inode to be created in @dir
3030 *
3031 * Umask stripping depends on whether or not the filesystem supports POSIX
3032 * ACLs. If the filesystem doesn't support it umask stripping is done directly
3033 * in here. If the filesystem does support POSIX ACLs umask stripping is
3034 * deferred until the filesystem calls posix_acl_create().
3035 *
3036 * Returns: mode
3037 */
3038static inline umode_t mode_strip_umask(const struct inode *dir, umode_t mode)
3039{
3040 if (!IS_POSIXACL(dir))
3041 mode &= ~current_umask();
3042 return mode;
3043}
3044
3045/**
3046 * vfs_prepare_mode - prepare the mode to be used for a new inode
3047 * @mnt_userns: user namespace of the mount the inode was found from
3048 * @dir: parent directory of the new inode
3049 * @mode: mode of the new inode
3050 * @mask_perms: allowed permission by the vfs
3051 * @type: type of file to be created
3052 *
3053 * This helper consolidates and enforces vfs restrictions on the @mode of a new
3054 * object to be created.
3055 *
3056 * Umask stripping depends on whether the filesystem supports POSIX ACLs (see
3057 * the kernel documentation for mode_strip_umask()). Moving umask stripping
3058 * after setgid stripping allows the same ordering for both non-POSIX ACL and
3059 * POSIX ACL supporting filesystems.
3060 *
3061 * Note that it's currently valid for @type to be 0 if a directory is created.
3062 * Filesystems raise that flag individually and we need to check whether each
3063 * filesystem can deal with receiving S_IFDIR from the vfs before we enforce a
3064 * non-zero type.
3065 *
3066 * Returns: mode to be passed to the filesystem
3067 */
3068static inline umode_t vfs_prepare_mode(struct user_namespace *mnt_userns,
3069 const struct inode *dir, umode_t mode,
3070 umode_t mask_perms, umode_t type)
3071{
3072 mode = mode_strip_sgid(mnt_userns, dir, mode);
3073 mode = mode_strip_umask(dir, mode);
3074
3075 /*
3076 * Apply the vfs mandated allowed permission mask and set the type of
3077 * file to be created before we call into the filesystem.
3078 */
3079 mode &= (mask_perms & ~S_IFMT);
3080 mode |= (type & S_IFMT);
3081
3082 return mode;
3083}
3084
3085/**
3086 * vfs_create - create new file
3087 * @mnt_userns: user namespace of the mount the inode was found from
3088 * @dir: inode of @dentry
3089 * @dentry: pointer to dentry of the base directory
3090 * @mode: mode of the new file
3091 * @want_excl: whether the file must not yet exist
3092 *
3093 * Create a new file.
3094 *
3095 * If the inode has been found through an idmapped mount the user namespace of
3096 * the vfsmount must be passed through @mnt_userns. This function will then take
3097 * care to map the inode according to @mnt_userns before checking permissions.
3098 * On non-idmapped mounts or if permission checking is to be performed on the
3099 * raw inode simply passs init_user_ns.
3100 */
3101int vfs_create(struct user_namespace *mnt_userns, struct inode *dir,
3102 struct dentry *dentry, umode_t mode, bool want_excl)
3103{
3104 int error = may_create(mnt_userns, dir, dentry);
3105 if (error)
3106 return error;
3107
3108 if (!dir->i_op->create)
3109 return -EACCES; /* shouldn't it be ENOSYS? */
3110
3111 mode = vfs_prepare_mode(mnt_userns, dir, mode, S_IALLUGO, S_IFREG);
3112 error = security_inode_create(dir, dentry, mode);
3113 if (error)
3114 return error;
3115 error = dir->i_op->create(mnt_userns, dir, dentry, mode, want_excl);
3116 if (!error)
3117 fsnotify_create(dir, dentry);
3118 return error;
3119}
3120EXPORT_SYMBOL(vfs_create);
3121
3122int vfs_mkobj(struct dentry *dentry, umode_t mode,
3123 int (*f)(struct dentry *, umode_t, void *),
3124 void *arg)
3125{
3126 struct inode *dir = dentry->d_parent->d_inode;
3127 int error = may_create(&init_user_ns, dir, dentry);
3128 if (error)
3129 return error;
3130
3131 mode &= S_IALLUGO;
3132 mode |= S_IFREG;
3133 error = security_inode_create(dir, dentry, mode);
3134 if (error)
3135 return error;
3136 error = f(dentry, mode, arg);
3137 if (!error)
3138 fsnotify_create(dir, dentry);
3139 return error;
3140}
3141EXPORT_SYMBOL(vfs_mkobj);
3142
3143bool may_open_dev(const struct path *path)
3144{
3145 return !(path->mnt->mnt_flags & MNT_NODEV) &&
3146 !(path->mnt->mnt_sb->s_iflags & SB_I_NODEV);
3147}
3148
3149static int may_open(struct user_namespace *mnt_userns, const struct path *path,
3150 int acc_mode, int flag)
3151{
3152 struct dentry *dentry = path->dentry;
3153 struct inode *inode = dentry->d_inode;
3154 int error;
3155
3156 if (!inode)
3157 return -ENOENT;
3158
3159 switch (inode->i_mode & S_IFMT) {
3160 case S_IFLNK:
3161 return -ELOOP;
3162 case S_IFDIR:
3163 if (acc_mode & MAY_WRITE)
3164 return -EISDIR;
3165 if (acc_mode & MAY_EXEC)
3166 return -EACCES;
3167 break;
3168 case S_IFBLK:
3169 case S_IFCHR:
3170 if (!may_open_dev(path))
3171 return -EACCES;
3172 fallthrough;
3173 case S_IFIFO:
3174 case S_IFSOCK:
3175 if (acc_mode & MAY_EXEC)
3176 return -EACCES;
3177 flag &= ~O_TRUNC;
3178 break;
3179 case S_IFREG:
3180 if ((acc_mode & MAY_EXEC) && path_noexec(path))
3181 return -EACCES;
3182 break;
3183 }
3184
3185 error = inode_permission(mnt_userns, inode, MAY_OPEN | acc_mode);
3186 if (error)
3187 return error;
3188
3189 /*
3190 * An append-only file must be opened in append mode for writing.
3191 */
3192 if (IS_APPEND(inode)) {
3193 if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
3194 return -EPERM;
3195 if (flag & O_TRUNC)
3196 return -EPERM;
3197 }
3198
3199 /* O_NOATIME can only be set by the owner or superuser */
3200 if (flag & O_NOATIME && !inode_owner_or_capable(mnt_userns, inode))
3201 return -EPERM;
3202
3203 return 0;
3204}
3205
3206static int handle_truncate(struct user_namespace *mnt_userns, struct file *filp)
3207{
3208 const struct path *path = &filp->f_path;
3209 struct inode *inode = path->dentry->d_inode;
3210 int error = get_write_access(inode);
3211 if (error)
3212 return error;
3213
3214 error = security_file_truncate(filp);
3215 if (!error) {
3216 error = do_truncate(mnt_userns, path->dentry, 0,
3217 ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
3218 filp);
3219 }
3220 put_write_access(inode);
3221 return error;
3222}
3223
3224static inline int open_to_namei_flags(int flag)
3225{
3226 if ((flag & O_ACCMODE) == 3)
3227 flag--;
3228 return flag;
3229}
3230
3231static int may_o_create(struct user_namespace *mnt_userns,
3232 const struct path *dir, struct dentry *dentry,
3233 umode_t mode)
3234{
3235 int error = security_path_mknod(dir, dentry, mode, 0);
3236 if (error)
3237 return error;
3238
3239 if (!fsuidgid_has_mapping(dir->dentry->d_sb, mnt_userns))
3240 return -EOVERFLOW;
3241
3242 error = inode_permission(mnt_userns, dir->dentry->d_inode,
3243 MAY_WRITE | MAY_EXEC);
3244 if (error)
3245 return error;
3246
3247 return security_inode_create(dir->dentry->d_inode, dentry, mode);
3248}
3249
3250/*
3251 * Attempt to atomically look up, create and open a file from a negative
3252 * dentry.
3253 *
3254 * Returns 0 if successful. The file will have been created and attached to
3255 * @file by the filesystem calling finish_open().
3256 *
3257 * If the file was looked up only or didn't need creating, FMODE_OPENED won't
3258 * be set. The caller will need to perform the open themselves. @path will
3259 * have been updated to point to the new dentry. This may be negative.
3260 *
3261 * Returns an error code otherwise.
3262 */
3263static struct dentry *atomic_open(struct nameidata *nd, struct dentry *dentry,
3264 struct file *file,
3265 int open_flag, umode_t mode)
3266{
3267 struct dentry *const DENTRY_NOT_SET = (void *) -1UL;
3268 struct inode *dir = nd->path.dentry->d_inode;
3269 int error;
3270
3271 if (nd->flags & LOOKUP_DIRECTORY)
3272 open_flag |= O_DIRECTORY;
3273
3274 file->f_path.dentry = DENTRY_NOT_SET;
3275 file->f_path.mnt = nd->path.mnt;
3276 error = dir->i_op->atomic_open(dir, dentry, file,
3277 open_to_namei_flags(open_flag), mode);
3278 d_lookup_done(dentry);
3279 if (!error) {
3280 if (file->f_mode & FMODE_OPENED) {
3281 if (unlikely(dentry != file->f_path.dentry)) {
3282 dput(dentry);
3283 dentry = dget(file->f_path.dentry);
3284 }
3285 } else if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) {
3286 error = -EIO;
3287 } else {
3288 if (file->f_path.dentry) {
3289 dput(dentry);
3290 dentry = file->f_path.dentry;
3291 }
3292 if (unlikely(d_is_negative(dentry)))
3293 error = -ENOENT;
3294 }
3295 }
3296 if (error) {
3297 dput(dentry);
3298 dentry = ERR_PTR(error);
3299 }
3300 return dentry;
3301}
3302
3303/*
3304 * Look up and maybe create and open the last component.
3305 *
3306 * Must be called with parent locked (exclusive in O_CREAT case).
3307 *
3308 * Returns 0 on success, that is, if
3309 * the file was successfully atomically created (if necessary) and opened, or
3310 * the file was not completely opened at this time, though lookups and
3311 * creations were performed.
3312 * These case are distinguished by presence of FMODE_OPENED on file->f_mode.
3313 * In the latter case dentry returned in @path might be negative if O_CREAT
3314 * hadn't been specified.
3315 *
3316 * An error code is returned on failure.
3317 */
3318static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
3319 const struct open_flags *op,
3320 bool got_write)
3321{
3322 struct user_namespace *mnt_userns;
3323 struct dentry *dir = nd->path.dentry;
3324 struct inode *dir_inode = dir->d_inode;
3325 int open_flag = op->open_flag;
3326 struct dentry *dentry;
3327 int error, create_error = 0;
3328 umode_t mode = op->mode;
3329 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
3330
3331 if (unlikely(IS_DEADDIR(dir_inode)))
3332 return ERR_PTR(-ENOENT);
3333
3334 file->f_mode &= ~FMODE_CREATED;
3335 dentry = d_lookup(dir, &nd->last);
3336 for (;;) {
3337 if (!dentry) {
3338 dentry = d_alloc_parallel(dir, &nd->last, &wq);
3339 if (IS_ERR(dentry))
3340 return dentry;
3341 }
3342 if (d_in_lookup(dentry))
3343 break;
3344
3345 error = d_revalidate(dentry, nd->flags);
3346 if (likely(error > 0))
3347 break;
3348 if (error)
3349 goto out_dput;
3350 d_invalidate(dentry);
3351 dput(dentry);
3352 dentry = NULL;
3353 }
3354 if (dentry->d_inode) {
3355 /* Cached positive dentry: will open in f_op->open */
3356 return dentry;
3357 }
3358
3359 /*
3360 * Checking write permission is tricky, bacuse we don't know if we are
3361 * going to actually need it: O_CREAT opens should work as long as the
3362 * file exists. But checking existence breaks atomicity. The trick is
3363 * to check access and if not granted clear O_CREAT from the flags.
3364 *
3365 * Another problem is returing the "right" error value (e.g. for an
3366 * O_EXCL open we want to return EEXIST not EROFS).
3367 */
3368 if (unlikely(!got_write))
3369 open_flag &= ~O_TRUNC;
3370 mnt_userns = mnt_user_ns(nd->path.mnt);
3371 if (open_flag & O_CREAT) {
3372 if (open_flag & O_EXCL)
3373 open_flag &= ~O_TRUNC;
3374 mode = vfs_prepare_mode(mnt_userns, dir->d_inode, mode, mode, mode);
3375 if (likely(got_write))
3376 create_error = may_o_create(mnt_userns, &nd->path,
3377 dentry, mode);
3378 else
3379 create_error = -EROFS;
3380 }
3381 if (create_error)
3382 open_flag &= ~O_CREAT;
3383 if (dir_inode->i_op->atomic_open) {
3384 dentry = atomic_open(nd, dentry, file, open_flag, mode);
3385 if (unlikely(create_error) && dentry == ERR_PTR(-ENOENT))
3386 dentry = ERR_PTR(create_error);
3387 return dentry;
3388 }
3389
3390 if (d_in_lookup(dentry)) {
3391 struct dentry *res = dir_inode->i_op->lookup(dir_inode, dentry,
3392 nd->flags);
3393 d_lookup_done(dentry);
3394 if (unlikely(res)) {
3395 if (IS_ERR(res)) {
3396 error = PTR_ERR(res);
3397 goto out_dput;
3398 }
3399 dput(dentry);
3400 dentry = res;
3401 }
3402 }
3403
3404 /* Negative dentry, just create the file */
3405 if (!dentry->d_inode && (open_flag & O_CREAT)) {
3406 file->f_mode |= FMODE_CREATED;
3407 audit_inode_child(dir_inode, dentry, AUDIT_TYPE_CHILD_CREATE);
3408 if (!dir_inode->i_op->create) {
3409 error = -EACCES;
3410 goto out_dput;
3411 }
3412
3413 error = dir_inode->i_op->create(mnt_userns, dir_inode, dentry,
3414 mode, open_flag & O_EXCL);
3415 if (error)
3416 goto out_dput;
3417 }
3418 if (unlikely(create_error) && !dentry->d_inode) {
3419 error = create_error;
3420 goto out_dput;
3421 }
3422 return dentry;
3423
3424out_dput:
3425 dput(dentry);
3426 return ERR_PTR(error);
3427}
3428
3429static const char *open_last_lookups(struct nameidata *nd,
3430 struct file *file, const struct open_flags *op)
3431{
3432 struct dentry *dir = nd->path.dentry;
3433 int open_flag = op->open_flag;
3434 bool got_write = false;
3435 struct dentry *dentry;
3436 const char *res;
3437
3438 nd->flags |= op->intent;
3439
3440 if (nd->last_type != LAST_NORM) {
3441 if (nd->depth)
3442 put_link(nd);
3443 return handle_dots(nd, nd->last_type);
3444 }
3445
3446 if (!(open_flag & O_CREAT)) {
3447 if (nd->last.name[nd->last.len])
3448 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
3449 /* we _can_ be in RCU mode here */
3450 dentry = lookup_fast(nd);
3451 if (IS_ERR(dentry))
3452 return ERR_CAST(dentry);
3453 if (likely(dentry))
3454 goto finish_lookup;
3455
3456 BUG_ON(nd->flags & LOOKUP_RCU);
3457 } else {
3458 /* create side of things */
3459 if (nd->flags & LOOKUP_RCU) {
3460 if (!try_to_unlazy(nd))
3461 return ERR_PTR(-ECHILD);
3462 }
3463 audit_inode(nd->name, dir, AUDIT_INODE_PARENT);
3464 /* trailing slashes? */
3465 if (unlikely(nd->last.name[nd->last.len]))
3466 return ERR_PTR(-EISDIR);
3467 }
3468
3469 if (open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
3470 got_write = !mnt_want_write(nd->path.mnt);
3471 /*
3472 * do _not_ fail yet - we might not need that or fail with
3473 * a different error; let lookup_open() decide; we'll be
3474 * dropping this one anyway.
3475 */
3476 }
3477 if (open_flag & O_CREAT)
3478 inode_lock(dir->d_inode);
3479 else
3480 inode_lock_shared(dir->d_inode);
3481 dentry = lookup_open(nd, file, op, got_write);
3482 if (!IS_ERR(dentry) && (file->f_mode & FMODE_CREATED))
3483 fsnotify_create(dir->d_inode, dentry);
3484 if (open_flag & O_CREAT)
3485 inode_unlock(dir->d_inode);
3486 else
3487 inode_unlock_shared(dir->d_inode);
3488
3489 if (got_write)
3490 mnt_drop_write(nd->path.mnt);
3491
3492 if (IS_ERR(dentry))
3493 return ERR_CAST(dentry);
3494
3495 if (file->f_mode & (FMODE_OPENED | FMODE_CREATED)) {
3496 dput(nd->path.dentry);
3497 nd->path.dentry = dentry;
3498 return NULL;
3499 }
3500
3501finish_lookup:
3502 if (nd->depth)
3503 put_link(nd);
3504 res = step_into(nd, WALK_TRAILING, dentry);
3505 if (unlikely(res))
3506 nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
3507 return res;
3508}
3509
3510/*
3511 * Handle the last step of open()
3512 */
3513static int do_open(struct nameidata *nd,
3514 struct file *file, const struct open_flags *op)
3515{
3516 struct user_namespace *mnt_userns;
3517 int open_flag = op->open_flag;
3518 bool do_truncate;
3519 int acc_mode;
3520 int error;
3521
3522 if (!(file->f_mode & (FMODE_OPENED | FMODE_CREATED))) {
3523 error = complete_walk(nd);
3524 if (error)
3525 return error;
3526 }
3527 if (!(file->f_mode & FMODE_CREATED))
3528 audit_inode(nd->name, nd->path.dentry, 0);
3529 mnt_userns = mnt_user_ns(nd->path.mnt);
3530 if (open_flag & O_CREAT) {
3531 if ((open_flag & O_EXCL) && !(file->f_mode & FMODE_CREATED))
3532 return -EEXIST;
3533 if (d_is_dir(nd->path.dentry))
3534 return -EISDIR;
3535 error = may_create_in_sticky(mnt_userns, nd,
3536 d_backing_inode(nd->path.dentry));
3537 if (unlikely(error))
3538 return error;
3539 }
3540 if ((nd->flags & LOOKUP_DIRECTORY) && !d_can_lookup(nd->path.dentry))
3541 return -ENOTDIR;
3542
3543 do_truncate = false;
3544 acc_mode = op->acc_mode;
3545 if (file->f_mode & FMODE_CREATED) {
3546 /* Don't check for write permission, don't truncate */
3547 open_flag &= ~O_TRUNC;
3548 acc_mode = 0;
3549 } else if (d_is_reg(nd->path.dentry) && open_flag & O_TRUNC) {
3550 error = mnt_want_write(nd->path.mnt);
3551 if (error)
3552 return error;
3553 do_truncate = true;
3554 }
3555 error = may_open(mnt_userns, &nd->path, acc_mode, open_flag);
3556 if (!error && !(file->f_mode & FMODE_OPENED))
3557 error = vfs_open(&nd->path, file);
3558 if (!error)
3559 error = ima_file_check(file, op->acc_mode);
3560 if (!error && do_truncate)
3561 error = handle_truncate(mnt_userns, file);
3562 if (unlikely(error > 0)) {
3563 WARN_ON(1);
3564 error = -EINVAL;
3565 }
3566 if (do_truncate)
3567 mnt_drop_write(nd->path.mnt);
3568 return error;
3569}
3570
3571/**
3572 * vfs_tmpfile - create tmpfile
3573 * @mnt_userns: user namespace of the mount the inode was found from
3574 * @dentry: pointer to dentry of the base directory
3575 * @mode: mode of the new tmpfile
3576 * @open_flag: flags
3577 *
3578 * Create a temporary file.
3579 *
3580 * If the inode has been found through an idmapped mount the user namespace of
3581 * the vfsmount must be passed through @mnt_userns. This function will then take
3582 * care to map the inode according to @mnt_userns before checking permissions.
3583 * On non-idmapped mounts or if permission checking is to be performed on the
3584 * raw inode simply passs init_user_ns.
3585 */
3586static int vfs_tmpfile(struct user_namespace *mnt_userns,
3587 const struct path *parentpath,
3588 struct file *file, umode_t mode)
3589{
3590 struct dentry *child;
3591 struct inode *dir = d_inode(parentpath->dentry);
3592 struct inode *inode;
3593 int error;
3594 int open_flag = file->f_flags;
3595
3596 /* we want directory to be writable */
3597 error = inode_permission(mnt_userns, dir, MAY_WRITE | MAY_EXEC);
3598 if (error)
3599 return error;
3600 if (!dir->i_op->tmpfile)
3601 return -EOPNOTSUPP;
3602 child = d_alloc(parentpath->dentry, &slash_name);
3603 if (unlikely(!child))
3604 return -ENOMEM;
3605 file->f_path.mnt = parentpath->mnt;
3606 file->f_path.dentry = child;
3607 mode = vfs_prepare_mode(mnt_userns, dir, mode, mode, mode);
3608 error = dir->i_op->tmpfile(mnt_userns, dir, file, mode);
3609 dput(child);
3610 if (error)
3611 return error;
3612 /* Don't check for other permissions, the inode was just created */
3613 error = may_open(mnt_userns, &file->f_path, 0, file->f_flags);
3614 if (error)
3615 return error;
3616 inode = file_inode(file);
3617 if (!(open_flag & O_EXCL)) {
3618 spin_lock(&inode->i_lock);
3619 inode->i_state |= I_LINKABLE;
3620 spin_unlock(&inode->i_lock);
3621 }
3622 ima_post_create_tmpfile(mnt_userns, inode);
3623 return 0;
3624}
3625
3626/**
3627 * vfs_tmpfile_open - open a tmpfile for kernel internal use
3628 * @mnt_userns: user namespace of the mount the inode was found from
3629 * @parentpath: path of the base directory
3630 * @mode: mode of the new tmpfile
3631 * @open_flag: flags
3632 * @cred: credentials for open
3633 *
3634 * Create and open a temporary file. The file is not accounted in nr_files,
3635 * hence this is only for kernel internal use, and must not be installed into
3636 * file tables or such.
3637 */
3638struct file *vfs_tmpfile_open(struct user_namespace *mnt_userns,
3639 const struct path *parentpath,
3640 umode_t mode, int open_flag, const struct cred *cred)
3641{
3642 struct file *file;
3643 int error;
3644
3645 file = alloc_empty_file_noaccount(open_flag, cred);
3646 if (!IS_ERR(file)) {
3647 error = vfs_tmpfile(mnt_userns, parentpath, file, mode);
3648 if (error) {
3649 fput(file);
3650 file = ERR_PTR(error);
3651 }
3652 }
3653 return file;
3654}
3655EXPORT_SYMBOL(vfs_tmpfile_open);
3656
3657static int do_tmpfile(struct nameidata *nd, unsigned flags,
3658 const struct open_flags *op,
3659 struct file *file)
3660{
3661 struct user_namespace *mnt_userns;
3662 struct path path;
3663 int error = path_lookupat(nd, flags | LOOKUP_DIRECTORY, &path);
3664
3665 if (unlikely(error))
3666 return error;
3667 error = mnt_want_write(path.mnt);
3668 if (unlikely(error))
3669 goto out;
3670 mnt_userns = mnt_user_ns(path.mnt);
3671 error = vfs_tmpfile(mnt_userns, &path, file, op->mode);
3672 if (error)
3673 goto out2;
3674 audit_inode(nd->name, file->f_path.dentry, 0);
3675out2:
3676 mnt_drop_write(path.mnt);
3677out:
3678 path_put(&path);
3679 return error;
3680}
3681
3682static int do_o_path(struct nameidata *nd, unsigned flags, struct file *file)
3683{
3684 struct path path;
3685 int error = path_lookupat(nd, flags, &path);
3686 if (!error) {
3687 audit_inode(nd->name, path.dentry, 0);
3688 error = vfs_open(&path, file);
3689 path_put(&path);
3690 }
3691 return error;
3692}
3693
3694static struct file *path_openat(struct nameidata *nd,
3695 const struct open_flags *op, unsigned flags)
3696{
3697 struct file *file;
3698 int error;
3699
3700 file = alloc_empty_file(op->open_flag, current_cred());
3701 if (IS_ERR(file))
3702 return file;
3703
3704 if (unlikely(file->f_flags & __O_TMPFILE)) {
3705 error = do_tmpfile(nd, flags, op, file);
3706 } else if (unlikely(file->f_flags & O_PATH)) {
3707 error = do_o_path(nd, flags, file);
3708 } else {
3709 const char *s = path_init(nd, flags);
3710 while (!(error = link_path_walk(s, nd)) &&
3711 (s = open_last_lookups(nd, file, op)) != NULL)
3712 ;
3713 if (!error)
3714 error = do_open(nd, file, op);
3715 terminate_walk(nd);
3716 }
3717 if (likely(!error)) {
3718 if (likely(file->f_mode & FMODE_OPENED))
3719 return file;
3720 WARN_ON(1);
3721 error = -EINVAL;
3722 }
3723 fput(file);
3724 if (error == -EOPENSTALE) {
3725 if (flags & LOOKUP_RCU)
3726 error = -ECHILD;
3727 else
3728 error = -ESTALE;
3729 }
3730 return ERR_PTR(error);
3731}
3732
3733struct file *do_filp_open(int dfd, struct filename *pathname,
3734 const struct open_flags *op)
3735{
3736 struct nameidata nd;
3737 int flags = op->lookup_flags;
3738 struct file *filp;
3739
3740 set_nameidata(&nd, dfd, pathname, NULL);
3741 filp = path_openat(&nd, op, flags | LOOKUP_RCU);
3742 if (unlikely(filp == ERR_PTR(-ECHILD)))
3743 filp = path_openat(&nd, op, flags);
3744 if (unlikely(filp == ERR_PTR(-ESTALE)))
3745 filp = path_openat(&nd, op, flags | LOOKUP_REVAL);
3746 restore_nameidata();
3747 return filp;
3748}
3749
3750struct file *do_file_open_root(const struct path *root,
3751 const char *name, const struct open_flags *op)
3752{
3753 struct nameidata nd;
3754 struct file *file;
3755 struct filename *filename;
3756 int flags = op->lookup_flags;
3757
3758 if (d_is_symlink(root->dentry) && op->intent & LOOKUP_OPEN)
3759 return ERR_PTR(-ELOOP);
3760
3761 filename = getname_kernel(name);
3762 if (IS_ERR(filename))
3763 return ERR_CAST(filename);
3764
3765 set_nameidata(&nd, -1, filename, root);
3766 file = path_openat(&nd, op, flags | LOOKUP_RCU);
3767 if (unlikely(file == ERR_PTR(-ECHILD)))
3768 file = path_openat(&nd, op, flags);
3769 if (unlikely(file == ERR_PTR(-ESTALE)))
3770 file = path_openat(&nd, op, flags | LOOKUP_REVAL);
3771 restore_nameidata();
3772 putname(filename);
3773 return file;
3774}
3775
3776static struct dentry *filename_create(int dfd, struct filename *name,
3777 struct path *path, unsigned int lookup_flags)
3778{
3779 struct dentry *dentry = ERR_PTR(-EEXIST);
3780 struct qstr last;
3781 bool want_dir = lookup_flags & LOOKUP_DIRECTORY;
3782 unsigned int reval_flag = lookup_flags & LOOKUP_REVAL;
3783 unsigned int create_flags = LOOKUP_CREATE | LOOKUP_EXCL;
3784 int type;
3785 int err2;
3786 int error;
3787
3788 error = filename_parentat(dfd, name, reval_flag, path, &last, &type);
3789 if (error)
3790 return ERR_PTR(error);
3791
3792 /*
3793 * Yucky last component or no last component at all?
3794 * (foo/., foo/.., /////)
3795 */
3796 if (unlikely(type != LAST_NORM))
3797 goto out;
3798
3799 /* don't fail immediately if it's r/o, at least try to report other errors */
3800 err2 = mnt_want_write(path->mnt);
3801 /*
3802 * Do the final lookup. Suppress 'create' if there is a trailing
3803 * '/', and a directory wasn't requested.
3804 */
3805 if (last.name[last.len] && !want_dir)
3806 create_flags = 0;
3807 inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
3808 dentry = __lookup_hash(&last, path->dentry, reval_flag | create_flags);
3809 if (IS_ERR(dentry))
3810 goto unlock;
3811
3812 error = -EEXIST;
3813 if (d_is_positive(dentry))
3814 goto fail;
3815
3816 /*
3817 * Special case - lookup gave negative, but... we had foo/bar/
3818 * From the vfs_mknod() POV we just have a negative dentry -
3819 * all is fine. Let's be bastards - you had / on the end, you've
3820 * been asking for (non-existent) directory. -ENOENT for you.
3821 */
3822 if (unlikely(!create_flags)) {
3823 error = -ENOENT;
3824 goto fail;
3825 }
3826 if (unlikely(err2)) {
3827 error = err2;
3828 goto fail;
3829 }
3830 return dentry;
3831fail:
3832 dput(dentry);
3833 dentry = ERR_PTR(error);
3834unlock:
3835 inode_unlock(path->dentry->d_inode);
3836 if (!err2)
3837 mnt_drop_write(path->mnt);
3838out:
3839 path_put(path);
3840 return dentry;
3841}
3842
3843struct dentry *kern_path_create(int dfd, const char *pathname,
3844 struct path *path, unsigned int lookup_flags)
3845{
3846 struct filename *filename = getname_kernel(pathname);
3847 struct dentry *res = filename_create(dfd, filename, path, lookup_flags);
3848
3849 putname(filename);
3850 return res;
3851}
3852EXPORT_SYMBOL(kern_path_create);
3853
3854void done_path_create(struct path *path, struct dentry *dentry)
3855{
3856 dput(dentry);
3857 inode_unlock(path->dentry->d_inode);
3858 mnt_drop_write(path->mnt);
3859 path_put(path);
3860}
3861EXPORT_SYMBOL(done_path_create);
3862
3863inline struct dentry *user_path_create(int dfd, const char __user *pathname,
3864 struct path *path, unsigned int lookup_flags)
3865{
3866 struct filename *filename = getname(pathname);
3867 struct dentry *res = filename_create(dfd, filename, path, lookup_flags);
3868
3869 putname(filename);
3870 return res;
3871}
3872EXPORT_SYMBOL(user_path_create);
3873
3874/**
3875 * vfs_mknod - create device node or file
3876 * @mnt_userns: user namespace of the mount the inode was found from
3877 * @dir: inode of @dentry
3878 * @dentry: pointer to dentry of the base directory
3879 * @mode: mode of the new device node or file
3880 * @dev: device number of device to create
3881 *
3882 * Create a device node or file.
3883 *
3884 * If the inode has been found through an idmapped mount the user namespace of
3885 * the vfsmount must be passed through @mnt_userns. This function will then take
3886 * care to map the inode according to @mnt_userns before checking permissions.
3887 * On non-idmapped mounts or if permission checking is to be performed on the
3888 * raw inode simply passs init_user_ns.
3889 */
3890int vfs_mknod(struct user_namespace *mnt_userns, struct inode *dir,
3891 struct dentry *dentry, umode_t mode, dev_t dev)
3892{
3893 bool is_whiteout = S_ISCHR(mode) && dev == WHITEOUT_DEV;
3894 int error = may_create(mnt_userns, dir, dentry);
3895
3896 if (error)
3897 return error;
3898
3899 if ((S_ISCHR(mode) || S_ISBLK(mode)) && !is_whiteout &&
3900 !capable(CAP_MKNOD))
3901 return -EPERM;
3902
3903 if (!dir->i_op->mknod)
3904 return -EPERM;
3905
3906 mode = vfs_prepare_mode(mnt_userns, dir, mode, mode, mode);
3907 error = devcgroup_inode_mknod(mode, dev);
3908 if (error)
3909 return error;
3910
3911 error = security_inode_mknod(dir, dentry, mode, dev);
3912 if (error)
3913 return error;
3914
3915 error = dir->i_op->mknod(mnt_userns, dir, dentry, mode, dev);
3916 if (!error)
3917 fsnotify_create(dir, dentry);
3918 return error;
3919}
3920EXPORT_SYMBOL(vfs_mknod);
3921
3922static int may_mknod(umode_t mode)
3923{
3924 switch (mode & S_IFMT) {
3925 case S_IFREG:
3926 case S_IFCHR:
3927 case S_IFBLK:
3928 case S_IFIFO:
3929 case S_IFSOCK:
3930 case 0: /* zero mode translates to S_IFREG */
3931 return 0;
3932 case S_IFDIR:
3933 return -EPERM;
3934 default:
3935 return -EINVAL;
3936 }
3937}
3938
3939static int do_mknodat(int dfd, struct filename *name, umode_t mode,
3940 unsigned int dev)
3941{
3942 struct user_namespace *mnt_userns;
3943 struct dentry *dentry;
3944 struct path path;
3945 int error;
3946 unsigned int lookup_flags = 0;
3947
3948 error = may_mknod(mode);
3949 if (error)
3950 goto out1;
3951retry:
3952 dentry = filename_create(dfd, name, &path, lookup_flags);
3953 error = PTR_ERR(dentry);
3954 if (IS_ERR(dentry))
3955 goto out1;
3956
3957 error = security_path_mknod(&path, dentry,
3958 mode_strip_umask(path.dentry->d_inode, mode), dev);
3959 if (error)
3960 goto out2;
3961
3962 mnt_userns = mnt_user_ns(path.mnt);
3963 switch (mode & S_IFMT) {
3964 case 0: case S_IFREG:
3965 error = vfs_create(mnt_userns, path.dentry->d_inode,
3966 dentry, mode, true);
3967 if (!error)
3968 ima_post_path_mknod(mnt_userns, dentry);
3969 break;
3970 case S_IFCHR: case S_IFBLK:
3971 error = vfs_mknod(mnt_userns, path.dentry->d_inode,
3972 dentry, mode, new_decode_dev(dev));
3973 break;
3974 case S_IFIFO: case S_IFSOCK:
3975 error = vfs_mknod(mnt_userns, path.dentry->d_inode,
3976 dentry, mode, 0);
3977 break;
3978 }
3979out2:
3980 done_path_create(&path, dentry);
3981 if (retry_estale(error, lookup_flags)) {
3982 lookup_flags |= LOOKUP_REVAL;
3983 goto retry;
3984 }
3985out1:
3986 putname(name);
3987 return error;
3988}
3989
3990SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,
3991 unsigned int, dev)
3992{
3993 return do_mknodat(dfd, getname(filename), mode, dev);
3994}
3995
3996SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev)
3997{
3998 return do_mknodat(AT_FDCWD, getname(filename), mode, dev);
3999}
4000
4001/**
4002 * vfs_mkdir - create directory
4003 * @mnt_userns: user namespace of the mount the inode was found from
4004 * @dir: inode of @dentry
4005 * @dentry: pointer to dentry of the base directory
4006 * @mode: mode of the new directory
4007 *
4008 * Create a directory.
4009 *
4010 * If the inode has been found through an idmapped mount the user namespace of
4011 * the vfsmount must be passed through @mnt_userns. This function will then take
4012 * care to map the inode according to @mnt_userns before checking permissions.
4013 * On non-idmapped mounts or if permission checking is to be performed on the
4014 * raw inode simply passs init_user_ns.
4015 */
4016int vfs_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
4017 struct dentry *dentry, umode_t mode)
4018{
4019 int error = may_create(mnt_userns, dir, dentry);
4020 unsigned max_links = dir->i_sb->s_max_links;
4021
4022 if (error)
4023 return error;
4024
4025 if (!dir->i_op->mkdir)
4026 return -EPERM;
4027
4028 mode = vfs_prepare_mode(mnt_userns, dir, mode, S_IRWXUGO | S_ISVTX, 0);
4029 error = security_inode_mkdir(dir, dentry, mode);
4030 if (error)
4031 return error;
4032
4033 if (max_links && dir->i_nlink >= max_links)
4034 return -EMLINK;
4035
4036 error = dir->i_op->mkdir(mnt_userns, dir, dentry, mode);
4037 if (!error)
4038 fsnotify_mkdir(dir, dentry);
4039 return error;
4040}
4041EXPORT_SYMBOL(vfs_mkdir);
4042
4043int do_mkdirat(int dfd, struct filename *name, umode_t mode)
4044{
4045 struct dentry *dentry;
4046 struct path path;
4047 int error;
4048 unsigned int lookup_flags = LOOKUP_DIRECTORY;
4049
4050retry:
4051 dentry = filename_create(dfd, name, &path, lookup_flags);
4052 error = PTR_ERR(dentry);
4053 if (IS_ERR(dentry))
4054 goto out_putname;
4055
4056 error = security_path_mkdir(&path, dentry,
4057 mode_strip_umask(path.dentry->d_inode, mode));
4058 if (!error) {
4059 struct user_namespace *mnt_userns;
4060 mnt_userns = mnt_user_ns(path.mnt);
4061 error = vfs_mkdir(mnt_userns, path.dentry->d_inode, dentry,
4062 mode);
4063 }
4064 done_path_create(&path, dentry);
4065 if (retry_estale(error, lookup_flags)) {
4066 lookup_flags |= LOOKUP_REVAL;
4067 goto retry;
4068 }
4069out_putname:
4070 putname(name);
4071 return error;
4072}
4073
4074SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
4075{
4076 return do_mkdirat(dfd, getname(pathname), mode);
4077}
4078
4079SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode)
4080{
4081 return do_mkdirat(AT_FDCWD, getname(pathname), mode);
4082}
4083
4084/**
4085 * vfs_rmdir - remove directory
4086 * @mnt_userns: user namespace of the mount the inode was found from
4087 * @dir: inode of @dentry
4088 * @dentry: pointer to dentry of the base directory
4089 *
4090 * Remove a directory.
4091 *
4092 * If the inode has been found through an idmapped mount the user namespace of
4093 * the vfsmount must be passed through @mnt_userns. This function will then take
4094 * care to map the inode according to @mnt_userns before checking permissions.
4095 * On non-idmapped mounts or if permission checking is to be performed on the
4096 * raw inode simply passs init_user_ns.
4097 */
4098int vfs_rmdir(struct user_namespace *mnt_userns, struct inode *dir,
4099 struct dentry *dentry)
4100{
4101 int error = may_delete(mnt_userns, dir, dentry, 1);
4102
4103 if (error)
4104 return error;
4105
4106 if (!dir->i_op->rmdir)
4107 return -EPERM;
4108
4109 dget(dentry);
4110 inode_lock(dentry->d_inode);
4111
4112 error = -EBUSY;
4113 if (is_local_mountpoint(dentry) ||
4114 (dentry->d_inode->i_flags & S_KERNEL_FILE))
4115 goto out;
4116
4117 error = security_inode_rmdir(dir, dentry);
4118 if (error)
4119 goto out;
4120
4121 error = dir->i_op->rmdir(dir, dentry);
4122 if (error)
4123 goto out;
4124
4125 shrink_dcache_parent(dentry);
4126 dentry->d_inode->i_flags |= S_DEAD;
4127 dont_mount(dentry);
4128 detach_mounts(dentry);
4129
4130out:
4131 inode_unlock(dentry->d_inode);
4132 dput(dentry);
4133 if (!error)
4134 d_delete_notify(dir, dentry);
4135 return error;
4136}
4137EXPORT_SYMBOL(vfs_rmdir);
4138
4139int do_rmdir(int dfd, struct filename *name)
4140{
4141 struct user_namespace *mnt_userns;
4142 int error;
4143 struct dentry *dentry;
4144 struct path path;
4145 struct qstr last;
4146 int type;
4147 unsigned int lookup_flags = 0;
4148retry:
4149 error = filename_parentat(dfd, name, lookup_flags, &path, &last, &type);
4150 if (error)
4151 goto exit1;
4152
4153 switch (type) {
4154 case LAST_DOTDOT:
4155 error = -ENOTEMPTY;
4156 goto exit2;
4157 case LAST_DOT:
4158 error = -EINVAL;
4159 goto exit2;
4160 case LAST_ROOT:
4161 error = -EBUSY;
4162 goto exit2;
4163 }
4164
4165 error = mnt_want_write(path.mnt);
4166 if (error)
4167 goto exit2;
4168
4169 inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT);
4170 dentry = __lookup_hash(&last, path.dentry, lookup_flags);
4171 error = PTR_ERR(dentry);
4172 if (IS_ERR(dentry))
4173 goto exit3;
4174 if (!dentry->d_inode) {
4175 error = -ENOENT;
4176 goto exit4;
4177 }
4178 error = security_path_rmdir(&path, dentry);
4179 if (error)
4180 goto exit4;
4181 mnt_userns = mnt_user_ns(path.mnt);
4182 error = vfs_rmdir(mnt_userns, path.dentry->d_inode, dentry);
4183exit4:
4184 dput(dentry);
4185exit3:
4186 inode_unlock(path.dentry->d_inode);
4187 mnt_drop_write(path.mnt);
4188exit2:
4189 path_put(&path);
4190 if (retry_estale(error, lookup_flags)) {
4191 lookup_flags |= LOOKUP_REVAL;
4192 goto retry;
4193 }
4194exit1:
4195 putname(name);
4196 return error;
4197}
4198
4199SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
4200{
4201 return do_rmdir(AT_FDCWD, getname(pathname));
4202}
4203
4204/**
4205 * vfs_unlink - unlink a filesystem object
4206 * @mnt_userns: user namespace of the mount the inode was found from
4207 * @dir: parent directory
4208 * @dentry: victim
4209 * @delegated_inode: returns victim inode, if the inode is delegated.
4210 *
4211 * The caller must hold dir->i_mutex.
4212 *
4213 * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and
4214 * return a reference to the inode in delegated_inode. The caller
4215 * should then break the delegation on that inode and retry. Because
4216 * breaking a delegation may take a long time, the caller should drop
4217 * dir->i_mutex before doing so.
4218 *
4219 * Alternatively, a caller may pass NULL for delegated_inode. This may
4220 * be appropriate for callers that expect the underlying filesystem not
4221 * to be NFS exported.
4222 *
4223 * If the inode has been found through an idmapped mount the user namespace of
4224 * the vfsmount must be passed through @mnt_userns. This function will then take
4225 * care to map the inode according to @mnt_userns before checking permissions.
4226 * On non-idmapped mounts or if permission checking is to be performed on the
4227 * raw inode simply passs init_user_ns.
4228 */
4229int vfs_unlink(struct user_namespace *mnt_userns, struct inode *dir,
4230 struct dentry *dentry, struct inode **delegated_inode)
4231{
4232 struct inode *target = dentry->d_inode;
4233 int error = may_delete(mnt_userns, dir, dentry, 0);
4234
4235 if (error)
4236 return error;
4237
4238 if (!dir->i_op->unlink)
4239 return -EPERM;
4240
4241 inode_lock(target);
4242 if (IS_SWAPFILE(target))
4243 error = -EPERM;
4244 else if (is_local_mountpoint(dentry))
4245 error = -EBUSY;
4246 else {
4247 error = security_inode_unlink(dir, dentry);
4248 if (!error) {
4249 error = try_break_deleg(target, delegated_inode);
4250 if (error)
4251 goto out;
4252 error = dir->i_op->unlink(dir, dentry);
4253 if (!error) {
4254 dont_mount(dentry);
4255 detach_mounts(dentry);
4256 }
4257 }
4258 }
4259out:
4260 inode_unlock(target);
4261
4262 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
4263 if (!error && dentry->d_flags & DCACHE_NFSFS_RENAMED) {
4264 fsnotify_unlink(dir, dentry);
4265 } else if (!error) {
4266 fsnotify_link_count(target);
4267 d_delete_notify(dir, dentry);
4268 }
4269
4270 return error;
4271}
4272EXPORT_SYMBOL(vfs_unlink);
4273
4274/*
4275 * Make sure that the actual truncation of the file will occur outside its
4276 * directory's i_mutex. Truncate can take a long time if there is a lot of
4277 * writeout happening, and we don't want to prevent access to the directory
4278 * while waiting on the I/O.
4279 */
4280int do_unlinkat(int dfd, struct filename *name)
4281{
4282 int error;
4283 struct dentry *dentry;
4284 struct path path;
4285 struct qstr last;
4286 int type;
4287 struct inode *inode = NULL;
4288 struct inode *delegated_inode = NULL;
4289 unsigned int lookup_flags = 0;
4290retry:
4291 error = filename_parentat(dfd, name, lookup_flags, &path, &last, &type);
4292 if (error)
4293 goto exit1;
4294
4295 error = -EISDIR;
4296 if (type != LAST_NORM)
4297 goto exit2;
4298
4299 error = mnt_want_write(path.mnt);
4300 if (error)
4301 goto exit2;
4302retry_deleg:
4303 inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT);
4304 dentry = __lookup_hash(&last, path.dentry, lookup_flags);
4305 error = PTR_ERR(dentry);
4306 if (!IS_ERR(dentry)) {
4307 struct user_namespace *mnt_userns;
4308
4309 /* Why not before? Because we want correct error value */
4310 if (last.name[last.len])
4311 goto slashes;
4312 inode = dentry->d_inode;
4313 if (d_is_negative(dentry))
4314 goto slashes;
4315 ihold(inode);
4316 error = security_path_unlink(&path, dentry);
4317 if (error)
4318 goto exit3;
4319 mnt_userns = mnt_user_ns(path.mnt);
4320 error = vfs_unlink(mnt_userns, path.dentry->d_inode, dentry,
4321 &delegated_inode);
4322exit3:
4323 dput(dentry);
4324 }
4325 inode_unlock(path.dentry->d_inode);
4326 if (inode)
4327 iput(inode); /* truncate the inode here */
4328 inode = NULL;
4329 if (delegated_inode) {
4330 error = break_deleg_wait(&delegated_inode);
4331 if (!error)
4332 goto retry_deleg;
4333 }
4334 mnt_drop_write(path.mnt);
4335exit2:
4336 path_put(&path);
4337 if (retry_estale(error, lookup_flags)) {
4338 lookup_flags |= LOOKUP_REVAL;
4339 inode = NULL;
4340 goto retry;
4341 }
4342exit1:
4343 putname(name);
4344 return error;
4345
4346slashes:
4347 if (d_is_negative(dentry))
4348 error = -ENOENT;
4349 else if (d_is_dir(dentry))
4350 error = -EISDIR;
4351 else
4352 error = -ENOTDIR;
4353 goto exit3;
4354}
4355
4356SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
4357{
4358 if ((flag & ~AT_REMOVEDIR) != 0)
4359 return -EINVAL;
4360
4361 if (flag & AT_REMOVEDIR)
4362 return do_rmdir(dfd, getname(pathname));
4363 return do_unlinkat(dfd, getname(pathname));
4364}
4365
4366SYSCALL_DEFINE1(unlink, const char __user *, pathname)
4367{
4368 return do_unlinkat(AT_FDCWD, getname(pathname));
4369}
4370
4371/**
4372 * vfs_symlink - create symlink
4373 * @mnt_userns: user namespace of the mount the inode was found from
4374 * @dir: inode of @dentry
4375 * @dentry: pointer to dentry of the base directory
4376 * @oldname: name of the file to link to
4377 *
4378 * Create a symlink.
4379 *
4380 * If the inode has been found through an idmapped mount the user namespace of
4381 * the vfsmount must be passed through @mnt_userns. This function will then take
4382 * care to map the inode according to @mnt_userns before checking permissions.
4383 * On non-idmapped mounts or if permission checking is to be performed on the
4384 * raw inode simply passs init_user_ns.
4385 */
4386int vfs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
4387 struct dentry *dentry, const char *oldname)
4388{
4389 int error = may_create(mnt_userns, dir, dentry);
4390
4391 if (error)
4392 return error;
4393
4394 if (!dir->i_op->symlink)
4395 return -EPERM;
4396
4397 error = security_inode_symlink(dir, dentry, oldname);
4398 if (error)
4399 return error;
4400
4401 error = dir->i_op->symlink(mnt_userns, dir, dentry, oldname);
4402 if (!error)
4403 fsnotify_create(dir, dentry);
4404 return error;
4405}
4406EXPORT_SYMBOL(vfs_symlink);
4407
4408int do_symlinkat(struct filename *from, int newdfd, struct filename *to)
4409{
4410 int error;
4411 struct dentry *dentry;
4412 struct path path;
4413 unsigned int lookup_flags = 0;
4414
4415 if (IS_ERR(from)) {
4416 error = PTR_ERR(from);
4417 goto out_putnames;
4418 }
4419retry:
4420 dentry = filename_create(newdfd, to, &path, lookup_flags);
4421 error = PTR_ERR(dentry);
4422 if (IS_ERR(dentry))
4423 goto out_putnames;
4424
4425 error = security_path_symlink(&path, dentry, from->name);
4426 if (!error) {
4427 struct user_namespace *mnt_userns;
4428
4429 mnt_userns = mnt_user_ns(path.mnt);
4430 error = vfs_symlink(mnt_userns, path.dentry->d_inode, dentry,
4431 from->name);
4432 }
4433 done_path_create(&path, dentry);
4434 if (retry_estale(error, lookup_flags)) {
4435 lookup_flags |= LOOKUP_REVAL;
4436 goto retry;
4437 }
4438out_putnames:
4439 putname(to);
4440 putname(from);
4441 return error;
4442}
4443
4444SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
4445 int, newdfd, const char __user *, newname)
4446{
4447 return do_symlinkat(getname(oldname), newdfd, getname(newname));
4448}
4449
4450SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
4451{
4452 return do_symlinkat(getname(oldname), AT_FDCWD, getname(newname));
4453}
4454
4455/**
4456 * vfs_link - create a new link
4457 * @old_dentry: object to be linked
4458 * @mnt_userns: the user namespace of the mount
4459 * @dir: new parent
4460 * @new_dentry: where to create the new link
4461 * @delegated_inode: returns inode needing a delegation break
4462 *
4463 * The caller must hold dir->i_mutex
4464 *
4465 * If vfs_link discovers a delegation on the to-be-linked file in need
4466 * of breaking, it will return -EWOULDBLOCK and return a reference to the
4467 * inode in delegated_inode. The caller should then break the delegation
4468 * and retry. Because breaking a delegation may take a long time, the
4469 * caller should drop the i_mutex before doing so.
4470 *
4471 * Alternatively, a caller may pass NULL for delegated_inode. This may
4472 * be appropriate for callers that expect the underlying filesystem not
4473 * to be NFS exported.
4474 *
4475 * If the inode has been found through an idmapped mount the user namespace of
4476 * the vfsmount must be passed through @mnt_userns. This function will then take
4477 * care to map the inode according to @mnt_userns before checking permissions.
4478 * On non-idmapped mounts or if permission checking is to be performed on the
4479 * raw inode simply passs init_user_ns.
4480 */
4481int vfs_link(struct dentry *old_dentry, struct user_namespace *mnt_userns,
4482 struct inode *dir, struct dentry *new_dentry,
4483 struct inode **delegated_inode)
4484{
4485 struct inode *inode = old_dentry->d_inode;
4486 unsigned max_links = dir->i_sb->s_max_links;
4487 int error;
4488
4489 if (!inode)
4490 return -ENOENT;
4491
4492 error = may_create(mnt_userns, dir, new_dentry);
4493 if (error)
4494 return error;
4495
4496 if (dir->i_sb != inode->i_sb)
4497 return -EXDEV;
4498
4499 /*
4500 * A link to an append-only or immutable file cannot be created.
4501 */
4502 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
4503 return -EPERM;
4504 /*
4505 * Updating the link count will likely cause i_uid and i_gid to
4506 * be writen back improperly if their true value is unknown to
4507 * the vfs.
4508 */
4509 if (HAS_UNMAPPED_ID(mnt_userns, inode))
4510 return -EPERM;
4511 if (!dir->i_op->link)
4512 return -EPERM;
4513 if (S_ISDIR(inode->i_mode))
4514 return -EPERM;
4515
4516 error = security_inode_link(old_dentry, dir, new_dentry);
4517 if (error)
4518 return error;
4519
4520 inode_lock(inode);
4521 /* Make sure we don't allow creating hardlink to an unlinked file */
4522 if (inode->i_nlink == 0 && !(inode->i_state & I_LINKABLE))
4523 error = -ENOENT;
4524 else if (max_links && inode->i_nlink >= max_links)
4525 error = -EMLINK;
4526 else {
4527 error = try_break_deleg(inode, delegated_inode);
4528 if (!error)
4529 error = dir->i_op->link(old_dentry, dir, new_dentry);
4530 }
4531
4532 if (!error && (inode->i_state & I_LINKABLE)) {
4533 spin_lock(&inode->i_lock);
4534 inode->i_state &= ~I_LINKABLE;
4535 spin_unlock(&inode->i_lock);
4536 }
4537 inode_unlock(inode);
4538 if (!error)
4539 fsnotify_link(dir, inode, new_dentry);
4540 return error;
4541}
4542EXPORT_SYMBOL(vfs_link);
4543
4544/*
4545 * Hardlinks are often used in delicate situations. We avoid
4546 * security-related surprises by not following symlinks on the
4547 * newname. --KAB
4548 *
4549 * We don't follow them on the oldname either to be compatible
4550 * with linux 2.0, and to avoid hard-linking to directories
4551 * and other special files. --ADM
4552 */
4553int do_linkat(int olddfd, struct filename *old, int newdfd,
4554 struct filename *new, int flags)
4555{
4556 struct user_namespace *mnt_userns;
4557 struct dentry *new_dentry;
4558 struct path old_path, new_path;
4559 struct inode *delegated_inode = NULL;
4560 int how = 0;
4561 int error;
4562
4563 if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0) {
4564 error = -EINVAL;
4565 goto out_putnames;
4566 }
4567 /*
4568 * To use null names we require CAP_DAC_READ_SEARCH
4569 * This ensures that not everyone will be able to create
4570 * handlink using the passed filedescriptor.
4571 */
4572 if (flags & AT_EMPTY_PATH && !capable(CAP_DAC_READ_SEARCH)) {
4573 error = -ENOENT;
4574 goto out_putnames;
4575 }
4576
4577 if (flags & AT_SYMLINK_FOLLOW)
4578 how |= LOOKUP_FOLLOW;
4579retry:
4580 error = filename_lookup(olddfd, old, how, &old_path, NULL);
4581 if (error)
4582 goto out_putnames;
4583
4584 new_dentry = filename_create(newdfd, new, &new_path,
4585 (how & LOOKUP_REVAL));
4586 error = PTR_ERR(new_dentry);
4587 if (IS_ERR(new_dentry))
4588 goto out_putpath;
4589
4590 error = -EXDEV;
4591 if (old_path.mnt != new_path.mnt)
4592 goto out_dput;
4593 mnt_userns = mnt_user_ns(new_path.mnt);
4594 error = may_linkat(mnt_userns, &old_path);
4595 if (unlikely(error))
4596 goto out_dput;
4597 error = security_path_link(old_path.dentry, &new_path, new_dentry);
4598 if (error)
4599 goto out_dput;
4600 error = vfs_link(old_path.dentry, mnt_userns, new_path.dentry->d_inode,
4601 new_dentry, &delegated_inode);
4602out_dput:
4603 done_path_create(&new_path, new_dentry);
4604 if (delegated_inode) {
4605 error = break_deleg_wait(&delegated_inode);
4606 if (!error) {
4607 path_put(&old_path);
4608 goto retry;
4609 }
4610 }
4611 if (retry_estale(error, how)) {
4612 path_put(&old_path);
4613 how |= LOOKUP_REVAL;
4614 goto retry;
4615 }
4616out_putpath:
4617 path_put(&old_path);
4618out_putnames:
4619 putname(old);
4620 putname(new);
4621
4622 return error;
4623}
4624
4625SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
4626 int, newdfd, const char __user *, newname, int, flags)
4627{
4628 return do_linkat(olddfd, getname_uflags(oldname, flags),
4629 newdfd, getname(newname), flags);
4630}
4631
4632SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
4633{
4634 return do_linkat(AT_FDCWD, getname(oldname), AT_FDCWD, getname(newname), 0);
4635}
4636
4637/**
4638 * vfs_rename - rename a filesystem object
4639 * @rd: pointer to &struct renamedata info
4640 *
4641 * The caller must hold multiple mutexes--see lock_rename()).
4642 *
4643 * If vfs_rename discovers a delegation in need of breaking at either
4644 * the source or destination, it will return -EWOULDBLOCK and return a
4645 * reference to the inode in delegated_inode. The caller should then
4646 * break the delegation and retry. Because breaking a delegation may
4647 * take a long time, the caller should drop all locks before doing
4648 * so.
4649 *
4650 * Alternatively, a caller may pass NULL for delegated_inode. This may
4651 * be appropriate for callers that expect the underlying filesystem not
4652 * to be NFS exported.
4653 *
4654 * The worst of all namespace operations - renaming directory. "Perverted"
4655 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
4656 * Problems:
4657 *
4658 * a) we can get into loop creation.
4659 * b) race potential - two innocent renames can create a loop together.
4660 * That's where 4.4 screws up. Current fix: serialization on
4661 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
4662 * story.
4663 * c) we have to lock _four_ objects - parents and victim (if it exists),
4664 * and source (if it is not a directory).
4665 * And that - after we got ->i_mutex on parents (until then we don't know
4666 * whether the target exists). Solution: try to be smart with locking
4667 * order for inodes. We rely on the fact that tree topology may change
4668 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
4669 * move will be locked. Thus we can rank directories by the tree
4670 * (ancestors first) and rank all non-directories after them.
4671 * That works since everybody except rename does "lock parent, lookup,
4672 * lock child" and rename is under ->s_vfs_rename_mutex.
4673 * HOWEVER, it relies on the assumption that any object with ->lookup()
4674 * has no more than 1 dentry. If "hybrid" objects will ever appear,
4675 * we'd better make sure that there's no link(2) for them.
4676 * d) conversion from fhandle to dentry may come in the wrong moment - when
4677 * we are removing the target. Solution: we will have to grab ->i_mutex
4678 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
4679 * ->i_mutex on parents, which works but leads to some truly excessive
4680 * locking].
4681 */
4682int vfs_rename(struct renamedata *rd)
4683{
4684 int error;
4685 struct inode *old_dir = rd->old_dir, *new_dir = rd->new_dir;
4686 struct dentry *old_dentry = rd->old_dentry;
4687 struct dentry *new_dentry = rd->new_dentry;
4688 struct inode **delegated_inode = rd->delegated_inode;
4689 unsigned int flags = rd->flags;
4690 bool is_dir = d_is_dir(old_dentry);
4691 struct inode *source = old_dentry->d_inode;
4692 struct inode *target = new_dentry->d_inode;
4693 bool new_is_dir = false;
4694 unsigned max_links = new_dir->i_sb->s_max_links;
4695 struct name_snapshot old_name;
4696
4697 if (source == target)
4698 return 0;
4699
4700 error = may_delete(rd->old_mnt_userns, old_dir, old_dentry, is_dir);
4701 if (error)
4702 return error;
4703
4704 if (!target) {
4705 error = may_create(rd->new_mnt_userns, new_dir, new_dentry);
4706 } else {
4707 new_is_dir = d_is_dir(new_dentry);
4708
4709 if (!(flags & RENAME_EXCHANGE))
4710 error = may_delete(rd->new_mnt_userns, new_dir,
4711 new_dentry, is_dir);
4712 else
4713 error = may_delete(rd->new_mnt_userns, new_dir,
4714 new_dentry, new_is_dir);
4715 }
4716 if (error)
4717 return error;
4718
4719 if (!old_dir->i_op->rename)
4720 return -EPERM;
4721
4722 /*
4723 * If we are going to change the parent - check write permissions,
4724 * we'll need to flip '..'.
4725 */
4726 if (new_dir != old_dir) {
4727 if (is_dir) {
4728 error = inode_permission(rd->old_mnt_userns, source,
4729 MAY_WRITE);
4730 if (error)
4731 return error;
4732 }
4733 if ((flags & RENAME_EXCHANGE) && new_is_dir) {
4734 error = inode_permission(rd->new_mnt_userns, target,
4735 MAY_WRITE);
4736 if (error)
4737 return error;
4738 }
4739 }
4740
4741 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry,
4742 flags);
4743 if (error)
4744 return error;
4745
4746 take_dentry_name_snapshot(&old_name, old_dentry);
4747 dget(new_dentry);
4748 if (!is_dir || (flags & RENAME_EXCHANGE))
4749 lock_two_nondirectories(source, target);
4750 else if (target)
4751 inode_lock(target);
4752
4753 error = -EPERM;
4754 if (IS_SWAPFILE(source) || (target && IS_SWAPFILE(target)))
4755 goto out;
4756
4757 error = -EBUSY;
4758 if (is_local_mountpoint(old_dentry) || is_local_mountpoint(new_dentry))
4759 goto out;
4760
4761 if (max_links && new_dir != old_dir) {
4762 error = -EMLINK;
4763 if (is_dir && !new_is_dir && new_dir->i_nlink >= max_links)
4764 goto out;
4765 if ((flags & RENAME_EXCHANGE) && !is_dir && new_is_dir &&
4766 old_dir->i_nlink >= max_links)
4767 goto out;
4768 }
4769 if (!is_dir) {
4770 error = try_break_deleg(source, delegated_inode);
4771 if (error)
4772 goto out;
4773 }
4774 if (target && !new_is_dir) {
4775 error = try_break_deleg(target, delegated_inode);
4776 if (error)
4777 goto out;
4778 }
4779 error = old_dir->i_op->rename(rd->new_mnt_userns, old_dir, old_dentry,
4780 new_dir, new_dentry, flags);
4781 if (error)
4782 goto out;
4783
4784 if (!(flags & RENAME_EXCHANGE) && target) {
4785 if (is_dir) {
4786 shrink_dcache_parent(new_dentry);
4787 target->i_flags |= S_DEAD;
4788 }
4789 dont_mount(new_dentry);
4790 detach_mounts(new_dentry);
4791 }
4792 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) {
4793 if (!(flags & RENAME_EXCHANGE))
4794 d_move(old_dentry, new_dentry);
4795 else
4796 d_exchange(old_dentry, new_dentry);
4797 }
4798out:
4799 if (!is_dir || (flags & RENAME_EXCHANGE))
4800 unlock_two_nondirectories(source, target);
4801 else if (target)
4802 inode_unlock(target);
4803 dput(new_dentry);
4804 if (!error) {
4805 fsnotify_move(old_dir, new_dir, &old_name.name, is_dir,
4806 !(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry);
4807 if (flags & RENAME_EXCHANGE) {
4808 fsnotify_move(new_dir, old_dir, &old_dentry->d_name,
4809 new_is_dir, NULL, new_dentry);
4810 }
4811 }
4812 release_dentry_name_snapshot(&old_name);
4813
4814 return error;
4815}
4816EXPORT_SYMBOL(vfs_rename);
4817
4818int do_renameat2(int olddfd, struct filename *from, int newdfd,
4819 struct filename *to, unsigned int flags)
4820{
4821 struct renamedata rd;
4822 struct dentry *old_dentry, *new_dentry;
4823 struct dentry *trap;
4824 struct path old_path, new_path;
4825 struct qstr old_last, new_last;
4826 int old_type, new_type;
4827 struct inode *delegated_inode = NULL;
4828 unsigned int lookup_flags = 0, target_flags = LOOKUP_RENAME_TARGET;
4829 bool should_retry = false;
4830 int error = -EINVAL;
4831
4832 if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
4833 goto put_names;
4834
4835 if ((flags & (RENAME_NOREPLACE | RENAME_WHITEOUT)) &&
4836 (flags & RENAME_EXCHANGE))
4837 goto put_names;
4838
4839 if (flags & RENAME_EXCHANGE)
4840 target_flags = 0;
4841
4842retry:
4843 error = filename_parentat(olddfd, from, lookup_flags, &old_path,
4844 &old_last, &old_type);
4845 if (error)
4846 goto put_names;
4847
4848 error = filename_parentat(newdfd, to, lookup_flags, &new_path, &new_last,
4849 &new_type);
4850 if (error)
4851 goto exit1;
4852
4853 error = -EXDEV;
4854 if (old_path.mnt != new_path.mnt)
4855 goto exit2;
4856
4857 error = -EBUSY;
4858 if (old_type != LAST_NORM)
4859 goto exit2;
4860
4861 if (flags & RENAME_NOREPLACE)
4862 error = -EEXIST;
4863 if (new_type != LAST_NORM)
4864 goto exit2;
4865
4866 error = mnt_want_write(old_path.mnt);
4867 if (error)
4868 goto exit2;
4869
4870retry_deleg:
4871 trap = lock_rename(new_path.dentry, old_path.dentry);
4872
4873 old_dentry = __lookup_hash(&old_last, old_path.dentry, lookup_flags);
4874 error = PTR_ERR(old_dentry);
4875 if (IS_ERR(old_dentry))
4876 goto exit3;
4877 /* source must exist */
4878 error = -ENOENT;
4879 if (d_is_negative(old_dentry))
4880 goto exit4;
4881 new_dentry = __lookup_hash(&new_last, new_path.dentry, lookup_flags | target_flags);
4882 error = PTR_ERR(new_dentry);
4883 if (IS_ERR(new_dentry))
4884 goto exit4;
4885 error = -EEXIST;
4886 if ((flags & RENAME_NOREPLACE) && d_is_positive(new_dentry))
4887 goto exit5;
4888 if (flags & RENAME_EXCHANGE) {
4889 error = -ENOENT;
4890 if (d_is_negative(new_dentry))
4891 goto exit5;
4892
4893 if (!d_is_dir(new_dentry)) {
4894 error = -ENOTDIR;
4895 if (new_last.name[new_last.len])
4896 goto exit5;
4897 }
4898 }
4899 /* unless the source is a directory trailing slashes give -ENOTDIR */
4900 if (!d_is_dir(old_dentry)) {
4901 error = -ENOTDIR;
4902 if (old_last.name[old_last.len])
4903 goto exit5;
4904 if (!(flags & RENAME_EXCHANGE) && new_last.name[new_last.len])
4905 goto exit5;
4906 }
4907 /* source should not be ancestor of target */
4908 error = -EINVAL;
4909 if (old_dentry == trap)
4910 goto exit5;
4911 /* target should not be an ancestor of source */
4912 if (!(flags & RENAME_EXCHANGE))
4913 error = -ENOTEMPTY;
4914 if (new_dentry == trap)
4915 goto exit5;
4916
4917 error = security_path_rename(&old_path, old_dentry,
4918 &new_path, new_dentry, flags);
4919 if (error)
4920 goto exit5;
4921
4922 rd.old_dir = old_path.dentry->d_inode;
4923 rd.old_dentry = old_dentry;
4924 rd.old_mnt_userns = mnt_user_ns(old_path.mnt);
4925 rd.new_dir = new_path.dentry->d_inode;
4926 rd.new_dentry = new_dentry;
4927 rd.new_mnt_userns = mnt_user_ns(new_path.mnt);
4928 rd.delegated_inode = &delegated_inode;
4929 rd.flags = flags;
4930 error = vfs_rename(&rd);
4931exit5:
4932 dput(new_dentry);
4933exit4:
4934 dput(old_dentry);
4935exit3:
4936 unlock_rename(new_path.dentry, old_path.dentry);
4937 if (delegated_inode) {
4938 error = break_deleg_wait(&delegated_inode);
4939 if (!error)
4940 goto retry_deleg;
4941 }
4942 mnt_drop_write(old_path.mnt);
4943exit2:
4944 if (retry_estale(error, lookup_flags))
4945 should_retry = true;
4946 path_put(&new_path);
4947exit1:
4948 path_put(&old_path);
4949 if (should_retry) {
4950 should_retry = false;
4951 lookup_flags |= LOOKUP_REVAL;
4952 goto retry;
4953 }
4954put_names:
4955 putname(from);
4956 putname(to);
4957 return error;
4958}
4959
4960SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname,
4961 int, newdfd, const char __user *, newname, unsigned int, flags)
4962{
4963 return do_renameat2(olddfd, getname(oldname), newdfd, getname(newname),
4964 flags);
4965}
4966
4967SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
4968 int, newdfd, const char __user *, newname)
4969{
4970 return do_renameat2(olddfd, getname(oldname), newdfd, getname(newname),
4971 0);
4972}
4973
4974SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
4975{
4976 return do_renameat2(AT_FDCWD, getname(oldname), AT_FDCWD,
4977 getname(newname), 0);
4978}
4979
4980int readlink_copy(char __user *buffer, int buflen, const char *link)
4981{
4982 int len = PTR_ERR(link);
4983 if (IS_ERR(link))
4984 goto out;
4985
4986 len = strlen(link);
4987 if (len > (unsigned) buflen)
4988 len = buflen;
4989 if (copy_to_user(buffer, link, len))
4990 len = -EFAULT;
4991out:
4992 return len;
4993}
4994
4995/**
4996 * vfs_readlink - copy symlink body into userspace buffer
4997 * @dentry: dentry on which to get symbolic link
4998 * @buffer: user memory pointer
4999 * @buflen: size of buffer
5000 *
5001 * Does not touch atime. That's up to the caller if necessary
5002 *
5003 * Does not call security hook.
5004 */
5005int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen)
5006{
5007 struct inode *inode = d_inode(dentry);
5008 DEFINE_DELAYED_CALL(done);
5009 const char *link;
5010 int res;
5011
5012 if (unlikely(!(inode->i_opflags & IOP_DEFAULT_READLINK))) {
5013 if (unlikely(inode->i_op->readlink))
5014 return inode->i_op->readlink(dentry, buffer, buflen);
5015
5016 if (!d_is_symlink(dentry))
5017 return -EINVAL;
5018
5019 spin_lock(&inode->i_lock);
5020 inode->i_opflags |= IOP_DEFAULT_READLINK;
5021 spin_unlock(&inode->i_lock);
5022 }
5023
5024 link = READ_ONCE(inode->i_link);
5025 if (!link) {
5026 link = inode->i_op->get_link(dentry, inode, &done);
5027 if (IS_ERR(link))
5028 return PTR_ERR(link);
5029 }
5030 res = readlink_copy(buffer, buflen, link);
5031 do_delayed_call(&done);
5032 return res;
5033}
5034EXPORT_SYMBOL(vfs_readlink);
5035
5036/**
5037 * vfs_get_link - get symlink body
5038 * @dentry: dentry on which to get symbolic link
5039 * @done: caller needs to free returned data with this
5040 *
5041 * Calls security hook and i_op->get_link() on the supplied inode.
5042 *
5043 * It does not touch atime. That's up to the caller if necessary.
5044 *
5045 * Does not work on "special" symlinks like /proc/$$/fd/N
5046 */
5047const char *vfs_get_link(struct dentry *dentry, struct delayed_call *done)
5048{
5049 const char *res = ERR_PTR(-EINVAL);
5050 struct inode *inode = d_inode(dentry);
5051
5052 if (d_is_symlink(dentry)) {
5053 res = ERR_PTR(security_inode_readlink(dentry));
5054 if (!res)
5055 res = inode->i_op->get_link(dentry, inode, done);
5056 }
5057 return res;
5058}
5059EXPORT_SYMBOL(vfs_get_link);
5060
5061/* get the link contents into pagecache */
5062const char *page_get_link(struct dentry *dentry, struct inode *inode,
5063 struct delayed_call *callback)
5064{
5065 char *kaddr;
5066 struct page *page;
5067 struct address_space *mapping = inode->i_mapping;
5068
5069 if (!dentry) {
5070 page = find_get_page(mapping, 0);
5071 if (!page)
5072 return ERR_PTR(-ECHILD);
5073 if (!PageUptodate(page)) {
5074 put_page(page);
5075 return ERR_PTR(-ECHILD);
5076 }
5077 } else {
5078 page = read_mapping_page(mapping, 0, NULL);
5079 if (IS_ERR(page))
5080 return (char*)page;
5081 }
5082 set_delayed_call(callback, page_put_link, page);
5083 BUG_ON(mapping_gfp_mask(mapping) & __GFP_HIGHMEM);
5084 kaddr = page_address(page);
5085 nd_terminate_link(kaddr, inode->i_size, PAGE_SIZE - 1);
5086 return kaddr;
5087}
5088
5089EXPORT_SYMBOL(page_get_link);
5090
5091void page_put_link(void *arg)
5092{
5093 put_page(arg);
5094}
5095EXPORT_SYMBOL(page_put_link);
5096
5097int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
5098{
5099 DEFINE_DELAYED_CALL(done);
5100 int res = readlink_copy(buffer, buflen,
5101 page_get_link(dentry, d_inode(dentry),
5102 &done));
5103 do_delayed_call(&done);
5104 return res;
5105}
5106EXPORT_SYMBOL(page_readlink);
5107
5108int page_symlink(struct inode *inode, const char *symname, int len)
5109{
5110 struct address_space *mapping = inode->i_mapping;
5111 const struct address_space_operations *aops = mapping->a_ops;
5112 bool nofs = !mapping_gfp_constraint(mapping, __GFP_FS);
5113 struct page *page;
5114 void *fsdata = NULL;
5115 int err;
5116 unsigned int flags;
5117
5118retry:
5119 if (nofs)
5120 flags = memalloc_nofs_save();
5121 err = aops->write_begin(NULL, mapping, 0, len-1, &page, &fsdata);
5122 if (nofs)
5123 memalloc_nofs_restore(flags);
5124 if (err)
5125 goto fail;
5126
5127 memcpy(page_address(page), symname, len-1);
5128
5129 err = aops->write_end(NULL, mapping, 0, len-1, len-1,
5130 page, fsdata);
5131 if (err < 0)
5132 goto fail;
5133 if (err < len-1)
5134 goto retry;
5135
5136 mark_inode_dirty(inode);
5137 return 0;
5138fail:
5139 return err;
5140}
5141EXPORT_SYMBOL(page_symlink);
5142
5143const struct inode_operations page_symlink_inode_operations = {
5144 .get_link = page_get_link,
5145};
5146EXPORT_SYMBOL(page_symlink_inode_operations);