Loading...
1/*
2 * linux/fs/namei.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 */
6
7/*
8 * Some corrections by tytso.
9 */
10
11/* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
12 * lookup logic.
13 */
14/* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.
15 */
16
17#include <linux/init.h>
18#include <linux/export.h>
19#include <linux/kernel.h>
20#include <linux/slab.h>
21#include <linux/fs.h>
22#include <linux/namei.h>
23#include <linux/pagemap.h>
24#include <linux/fsnotify.h>
25#include <linux/personality.h>
26#include <linux/security.h>
27#include <linux/ima.h>
28#include <linux/syscalls.h>
29#include <linux/mount.h>
30#include <linux/audit.h>
31#include <linux/capability.h>
32#include <linux/file.h>
33#include <linux/fcntl.h>
34#include <linux/device_cgroup.h>
35#include <linux/fs_struct.h>
36#include <linux/posix_acl.h>
37#include <linux/hash.h>
38#include <asm/uaccess.h>
39
40#include "internal.h"
41#include "mount.h"
42
43/* [Feb-1997 T. Schoebel-Theuer]
44 * Fundamental changes in the pathname lookup mechanisms (namei)
45 * were necessary because of omirr. The reason is that omirr needs
46 * to know the _real_ pathname, not the user-supplied one, in case
47 * of symlinks (and also when transname replacements occur).
48 *
49 * The new code replaces the old recursive symlink resolution with
50 * an iterative one (in case of non-nested symlink chains). It does
51 * this with calls to <fs>_follow_link().
52 * As a side effect, dir_namei(), _namei() and follow_link() are now
53 * replaced with a single function lookup_dentry() that can handle all
54 * the special cases of the former code.
55 *
56 * With the new dcache, the pathname is stored at each inode, at least as
57 * long as the refcount of the inode is positive. As a side effect, the
58 * size of the dcache depends on the inode cache and thus is dynamic.
59 *
60 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
61 * resolution to correspond with current state of the code.
62 *
63 * Note that the symlink resolution is not *completely* iterative.
64 * There is still a significant amount of tail- and mid- recursion in
65 * the algorithm. Also, note that <fs>_readlink() is not used in
66 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
67 * may return different results than <fs>_follow_link(). Many virtual
68 * filesystems (including /proc) exhibit this behavior.
69 */
70
71/* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
72 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
73 * and the name already exists in form of a symlink, try to create the new
74 * name indicated by the symlink. The old code always complained that the
75 * name already exists, due to not following the symlink even if its target
76 * is nonexistent. The new semantics affects also mknod() and link() when
77 * the name is a symlink pointing to a non-existent name.
78 *
79 * I don't know which semantics is the right one, since I have no access
80 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
81 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
82 * "old" one. Personally, I think the new semantics is much more logical.
83 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
84 * file does succeed in both HP-UX and SunOs, but not in Solaris
85 * and in the old Linux semantics.
86 */
87
88/* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
89 * semantics. See the comments in "open_namei" and "do_link" below.
90 *
91 * [10-Sep-98 Alan Modra] Another symlink change.
92 */
93
94/* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
95 * inside the path - always follow.
96 * in the last component in creation/removal/renaming - never follow.
97 * if LOOKUP_FOLLOW passed - follow.
98 * if the pathname has trailing slashes - follow.
99 * otherwise - don't follow.
100 * (applied in that order).
101 *
102 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
103 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
104 * During the 2.4 we need to fix the userland stuff depending on it -
105 * hopefully we will be able to get rid of that wart in 2.5. So far only
106 * XEmacs seems to be relying on it...
107 */
108/*
109 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
110 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
111 * any extra contention...
112 */
113
114/* In order to reduce some races, while at the same time doing additional
115 * checking and hopefully speeding things up, we copy filenames to the
116 * kernel data space before using them..
117 *
118 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
119 * PATH_MAX includes the nul terminator --RR.
120 */
121
122#define EMBEDDED_NAME_MAX (PATH_MAX - offsetof(struct filename, iname))
123
124struct filename *
125getname_flags(const char __user *filename, int flags, int *empty)
126{
127 struct filename *result;
128 char *kname;
129 int len;
130
131 result = audit_reusename(filename);
132 if (result)
133 return result;
134
135 result = __getname();
136 if (unlikely(!result))
137 return ERR_PTR(-ENOMEM);
138
139 /*
140 * First, try to embed the struct filename inside the names_cache
141 * allocation
142 */
143 kname = (char *)result->iname;
144 result->name = kname;
145
146 len = strncpy_from_user(kname, filename, EMBEDDED_NAME_MAX);
147 if (unlikely(len < 0)) {
148 __putname(result);
149 return ERR_PTR(len);
150 }
151
152 /*
153 * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a
154 * separate struct filename so we can dedicate the entire
155 * names_cache allocation for the pathname, and re-do the copy from
156 * userland.
157 */
158 if (unlikely(len == EMBEDDED_NAME_MAX)) {
159 const size_t size = offsetof(struct filename, iname[1]);
160 kname = (char *)result;
161
162 /*
163 * size is chosen that way we to guarantee that
164 * result->iname[0] is within the same object and that
165 * kname can't be equal to result->iname, no matter what.
166 */
167 result = kzalloc(size, GFP_KERNEL);
168 if (unlikely(!result)) {
169 __putname(kname);
170 return ERR_PTR(-ENOMEM);
171 }
172 result->name = kname;
173 len = strncpy_from_user(kname, filename, PATH_MAX);
174 if (unlikely(len < 0)) {
175 __putname(kname);
176 kfree(result);
177 return ERR_PTR(len);
178 }
179 if (unlikely(len == PATH_MAX)) {
180 __putname(kname);
181 kfree(result);
182 return ERR_PTR(-ENAMETOOLONG);
183 }
184 }
185
186 result->refcnt = 1;
187 /* The empty path is special. */
188 if (unlikely(!len)) {
189 if (empty)
190 *empty = 1;
191 if (!(flags & LOOKUP_EMPTY)) {
192 putname(result);
193 return ERR_PTR(-ENOENT);
194 }
195 }
196
197 result->uptr = filename;
198 result->aname = NULL;
199 audit_getname(result);
200 return result;
201}
202
203struct filename *
204getname(const char __user * filename)
205{
206 return getname_flags(filename, 0, NULL);
207}
208
209struct filename *
210getname_kernel(const char * filename)
211{
212 struct filename *result;
213 int len = strlen(filename) + 1;
214
215 result = __getname();
216 if (unlikely(!result))
217 return ERR_PTR(-ENOMEM);
218
219 if (len <= EMBEDDED_NAME_MAX) {
220 result->name = (char *)result->iname;
221 } else if (len <= PATH_MAX) {
222 struct filename *tmp;
223
224 tmp = kmalloc(sizeof(*tmp), GFP_KERNEL);
225 if (unlikely(!tmp)) {
226 __putname(result);
227 return ERR_PTR(-ENOMEM);
228 }
229 tmp->name = (char *)result;
230 result = tmp;
231 } else {
232 __putname(result);
233 return ERR_PTR(-ENAMETOOLONG);
234 }
235 memcpy((char *)result->name, filename, len);
236 result->uptr = NULL;
237 result->aname = NULL;
238 result->refcnt = 1;
239 audit_getname(result);
240
241 return result;
242}
243
244void putname(struct filename *name)
245{
246 BUG_ON(name->refcnt <= 0);
247
248 if (--name->refcnt > 0)
249 return;
250
251 if (name->name != name->iname) {
252 __putname(name->name);
253 kfree(name);
254 } else
255 __putname(name);
256}
257
258static int check_acl(struct inode *inode, int mask)
259{
260#ifdef CONFIG_FS_POSIX_ACL
261 struct posix_acl *acl;
262
263 if (mask & MAY_NOT_BLOCK) {
264 acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS);
265 if (!acl)
266 return -EAGAIN;
267 /* no ->get_acl() calls in RCU mode... */
268 if (acl == ACL_NOT_CACHED)
269 return -ECHILD;
270 return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK);
271 }
272
273 acl = get_acl(inode, ACL_TYPE_ACCESS);
274 if (IS_ERR(acl))
275 return PTR_ERR(acl);
276 if (acl) {
277 int error = posix_acl_permission(inode, acl, mask);
278 posix_acl_release(acl);
279 return error;
280 }
281#endif
282
283 return -EAGAIN;
284}
285
286/*
287 * This does the basic permission checking
288 */
289static int acl_permission_check(struct inode *inode, int mask)
290{
291 unsigned int mode = inode->i_mode;
292
293 if (likely(uid_eq(current_fsuid(), inode->i_uid)))
294 mode >>= 6;
295 else {
296 if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
297 int error = check_acl(inode, mask);
298 if (error != -EAGAIN)
299 return error;
300 }
301
302 if (in_group_p(inode->i_gid))
303 mode >>= 3;
304 }
305
306 /*
307 * If the DACs are ok we don't need any capability check.
308 */
309 if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0)
310 return 0;
311 return -EACCES;
312}
313
314/**
315 * generic_permission - check for access rights on a Posix-like filesystem
316 * @inode: inode to check access rights for
317 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
318 *
319 * Used to check for read/write/execute permissions on a file.
320 * We use "fsuid" for this, letting us set arbitrary permissions
321 * for filesystem access without changing the "normal" uids which
322 * are used for other things.
323 *
324 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
325 * request cannot be satisfied (eg. requires blocking or too much complexity).
326 * It would then be called again in ref-walk mode.
327 */
328int generic_permission(struct inode *inode, int mask)
329{
330 int ret;
331
332 /*
333 * Do the basic permission checks.
334 */
335 ret = acl_permission_check(inode, mask);
336 if (ret != -EACCES)
337 return ret;
338
339 if (S_ISDIR(inode->i_mode)) {
340 /* DACs are overridable for directories */
341 if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE))
342 return 0;
343 if (!(mask & MAY_WRITE))
344 if (capable_wrt_inode_uidgid(inode,
345 CAP_DAC_READ_SEARCH))
346 return 0;
347 return -EACCES;
348 }
349 /*
350 * Read/write DACs are always overridable.
351 * Executable DACs are overridable when there is
352 * at least one exec bit set.
353 */
354 if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
355 if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE))
356 return 0;
357
358 /*
359 * Searching includes executable on directories, else just read.
360 */
361 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
362 if (mask == MAY_READ)
363 if (capable_wrt_inode_uidgid(inode, CAP_DAC_READ_SEARCH))
364 return 0;
365
366 return -EACCES;
367}
368EXPORT_SYMBOL(generic_permission);
369
370/*
371 * We _really_ want to just do "generic_permission()" without
372 * even looking at the inode->i_op values. So we keep a cache
373 * flag in inode->i_opflags, that says "this has not special
374 * permission function, use the fast case".
375 */
376static inline int do_inode_permission(struct inode *inode, int mask)
377{
378 if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) {
379 if (likely(inode->i_op->permission))
380 return inode->i_op->permission(inode, mask);
381
382 /* This gets set once for the inode lifetime */
383 spin_lock(&inode->i_lock);
384 inode->i_opflags |= IOP_FASTPERM;
385 spin_unlock(&inode->i_lock);
386 }
387 return generic_permission(inode, mask);
388}
389
390/**
391 * __inode_permission - Check for access rights to a given inode
392 * @inode: Inode to check permission on
393 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
394 *
395 * Check for read/write/execute permissions on an inode.
396 *
397 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
398 *
399 * This does not check for a read-only file system. You probably want
400 * inode_permission().
401 */
402int __inode_permission(struct inode *inode, int mask)
403{
404 int retval;
405
406 if (unlikely(mask & MAY_WRITE)) {
407 /*
408 * Nobody gets write access to an immutable file.
409 */
410 if (IS_IMMUTABLE(inode))
411 return -EACCES;
412 }
413
414 retval = do_inode_permission(inode, mask);
415 if (retval)
416 return retval;
417
418 retval = devcgroup_inode_permission(inode, mask);
419 if (retval)
420 return retval;
421
422 return security_inode_permission(inode, mask);
423}
424EXPORT_SYMBOL(__inode_permission);
425
426/**
427 * sb_permission - Check superblock-level permissions
428 * @sb: Superblock of inode to check permission on
429 * @inode: Inode to check permission on
430 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
431 *
432 * Separate out file-system wide checks from inode-specific permission checks.
433 */
434static int sb_permission(struct super_block *sb, struct inode *inode, int mask)
435{
436 if (unlikely(mask & MAY_WRITE)) {
437 umode_t mode = inode->i_mode;
438
439 /* Nobody gets write access to a read-only fs. */
440 if ((sb->s_flags & MS_RDONLY) &&
441 (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
442 return -EROFS;
443 }
444 return 0;
445}
446
447/**
448 * inode_permission - Check for access rights to a given inode
449 * @inode: Inode to check permission on
450 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
451 *
452 * Check for read/write/execute permissions on an inode. We use fs[ug]id for
453 * this, letting us set arbitrary permissions for filesystem access without
454 * changing the "normal" UIDs which are used for other things.
455 *
456 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
457 */
458int inode_permission(struct inode *inode, int mask)
459{
460 int retval;
461
462 retval = sb_permission(inode->i_sb, inode, mask);
463 if (retval)
464 return retval;
465 return __inode_permission(inode, mask);
466}
467EXPORT_SYMBOL(inode_permission);
468
469/**
470 * path_get - get a reference to a path
471 * @path: path to get the reference to
472 *
473 * Given a path increment the reference count to the dentry and the vfsmount.
474 */
475void path_get(const struct path *path)
476{
477 mntget(path->mnt);
478 dget(path->dentry);
479}
480EXPORT_SYMBOL(path_get);
481
482/**
483 * path_put - put a reference to a path
484 * @path: path to put the reference to
485 *
486 * Given a path decrement the reference count to the dentry and the vfsmount.
487 */
488void path_put(const struct path *path)
489{
490 dput(path->dentry);
491 mntput(path->mnt);
492}
493EXPORT_SYMBOL(path_put);
494
495#define EMBEDDED_LEVELS 2
496struct nameidata {
497 struct path path;
498 struct qstr last;
499 struct path root;
500 struct inode *inode; /* path.dentry.d_inode */
501 unsigned int flags;
502 unsigned seq, m_seq;
503 int last_type;
504 unsigned depth;
505 int total_link_count;
506 struct saved {
507 struct path link;
508 struct delayed_call done;
509 const char *name;
510 unsigned seq;
511 } *stack, internal[EMBEDDED_LEVELS];
512 struct filename *name;
513 struct nameidata *saved;
514 struct inode *link_inode;
515 unsigned root_seq;
516 int dfd;
517};
518
519static void set_nameidata(struct nameidata *p, int dfd, struct filename *name)
520{
521 struct nameidata *old = current->nameidata;
522 p->stack = p->internal;
523 p->dfd = dfd;
524 p->name = name;
525 p->total_link_count = old ? old->total_link_count : 0;
526 p->saved = old;
527 current->nameidata = p;
528}
529
530static void restore_nameidata(void)
531{
532 struct nameidata *now = current->nameidata, *old = now->saved;
533
534 current->nameidata = old;
535 if (old)
536 old->total_link_count = now->total_link_count;
537 if (now->stack != now->internal)
538 kfree(now->stack);
539}
540
541static int __nd_alloc_stack(struct nameidata *nd)
542{
543 struct saved *p;
544
545 if (nd->flags & LOOKUP_RCU) {
546 p= kmalloc(MAXSYMLINKS * sizeof(struct saved),
547 GFP_ATOMIC);
548 if (unlikely(!p))
549 return -ECHILD;
550 } else {
551 p= kmalloc(MAXSYMLINKS * sizeof(struct saved),
552 GFP_KERNEL);
553 if (unlikely(!p))
554 return -ENOMEM;
555 }
556 memcpy(p, nd->internal, sizeof(nd->internal));
557 nd->stack = p;
558 return 0;
559}
560
561/**
562 * path_connected - Verify that a path->dentry is below path->mnt.mnt_root
563 * @path: nameidate to verify
564 *
565 * Rename can sometimes move a file or directory outside of a bind
566 * mount, path_connected allows those cases to be detected.
567 */
568static bool path_connected(const struct path *path)
569{
570 struct vfsmount *mnt = path->mnt;
571
572 /* Only bind mounts can have disconnected paths */
573 if (mnt->mnt_root == mnt->mnt_sb->s_root)
574 return true;
575
576 return is_subdir(path->dentry, mnt->mnt_root);
577}
578
579static inline int nd_alloc_stack(struct nameidata *nd)
580{
581 if (likely(nd->depth != EMBEDDED_LEVELS))
582 return 0;
583 if (likely(nd->stack != nd->internal))
584 return 0;
585 return __nd_alloc_stack(nd);
586}
587
588static void drop_links(struct nameidata *nd)
589{
590 int i = nd->depth;
591 while (i--) {
592 struct saved *last = nd->stack + i;
593 do_delayed_call(&last->done);
594 clear_delayed_call(&last->done);
595 }
596}
597
598static void terminate_walk(struct nameidata *nd)
599{
600 drop_links(nd);
601 if (!(nd->flags & LOOKUP_RCU)) {
602 int i;
603 path_put(&nd->path);
604 for (i = 0; i < nd->depth; i++)
605 path_put(&nd->stack[i].link);
606 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
607 path_put(&nd->root);
608 nd->root.mnt = NULL;
609 }
610 } else {
611 nd->flags &= ~LOOKUP_RCU;
612 if (!(nd->flags & LOOKUP_ROOT))
613 nd->root.mnt = NULL;
614 rcu_read_unlock();
615 }
616 nd->depth = 0;
617}
618
619/* path_put is needed afterwards regardless of success or failure */
620static bool legitimize_path(struct nameidata *nd,
621 struct path *path, unsigned seq)
622{
623 int res = __legitimize_mnt(path->mnt, nd->m_seq);
624 if (unlikely(res)) {
625 if (res > 0)
626 path->mnt = NULL;
627 path->dentry = NULL;
628 return false;
629 }
630 if (unlikely(!lockref_get_not_dead(&path->dentry->d_lockref))) {
631 path->dentry = NULL;
632 return false;
633 }
634 return !read_seqcount_retry(&path->dentry->d_seq, seq);
635}
636
637static bool legitimize_links(struct nameidata *nd)
638{
639 int i;
640 for (i = 0; i < nd->depth; i++) {
641 struct saved *last = nd->stack + i;
642 if (unlikely(!legitimize_path(nd, &last->link, last->seq))) {
643 drop_links(nd);
644 nd->depth = i + 1;
645 return false;
646 }
647 }
648 return true;
649}
650
651/*
652 * Path walking has 2 modes, rcu-walk and ref-walk (see
653 * Documentation/filesystems/path-lookup.txt). In situations when we can't
654 * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
655 * normal reference counts on dentries and vfsmounts to transition to ref-walk
656 * mode. Refcounts are grabbed at the last known good point before rcu-walk
657 * got stuck, so ref-walk may continue from there. If this is not successful
658 * (eg. a seqcount has changed), then failure is returned and it's up to caller
659 * to restart the path walk from the beginning in ref-walk mode.
660 */
661
662/**
663 * unlazy_walk - try to switch to ref-walk mode.
664 * @nd: nameidata pathwalk data
665 * @dentry: child of nd->path.dentry or NULL
666 * @seq: seq number to check dentry against
667 * Returns: 0 on success, -ECHILD on failure
668 *
669 * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry
670 * for ref-walk mode. @dentry must be a path found by a do_lookup call on
671 * @nd or NULL. Must be called from rcu-walk context.
672 * Nothing should touch nameidata between unlazy_walk() failure and
673 * terminate_walk().
674 */
675static int unlazy_walk(struct nameidata *nd, struct dentry *dentry, unsigned seq)
676{
677 struct dentry *parent = nd->path.dentry;
678
679 BUG_ON(!(nd->flags & LOOKUP_RCU));
680
681 nd->flags &= ~LOOKUP_RCU;
682 if (unlikely(!legitimize_links(nd)))
683 goto out2;
684 if (unlikely(!legitimize_mnt(nd->path.mnt, nd->m_seq)))
685 goto out2;
686 if (unlikely(!lockref_get_not_dead(&parent->d_lockref)))
687 goto out1;
688
689 /*
690 * For a negative lookup, the lookup sequence point is the parents
691 * sequence point, and it only needs to revalidate the parent dentry.
692 *
693 * For a positive lookup, we need to move both the parent and the
694 * dentry from the RCU domain to be properly refcounted. And the
695 * sequence number in the dentry validates *both* dentry counters,
696 * since we checked the sequence number of the parent after we got
697 * the child sequence number. So we know the parent must still
698 * be valid if the child sequence number is still valid.
699 */
700 if (!dentry) {
701 if (read_seqcount_retry(&parent->d_seq, nd->seq))
702 goto out;
703 BUG_ON(nd->inode != parent->d_inode);
704 } else {
705 if (!lockref_get_not_dead(&dentry->d_lockref))
706 goto out;
707 if (read_seqcount_retry(&dentry->d_seq, seq))
708 goto drop_dentry;
709 }
710
711 /*
712 * Sequence counts matched. Now make sure that the root is
713 * still valid and get it if required.
714 */
715 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
716 if (unlikely(!legitimize_path(nd, &nd->root, nd->root_seq))) {
717 rcu_read_unlock();
718 dput(dentry);
719 return -ECHILD;
720 }
721 }
722
723 rcu_read_unlock();
724 return 0;
725
726drop_dentry:
727 rcu_read_unlock();
728 dput(dentry);
729 goto drop_root_mnt;
730out2:
731 nd->path.mnt = NULL;
732out1:
733 nd->path.dentry = NULL;
734out:
735 rcu_read_unlock();
736drop_root_mnt:
737 if (!(nd->flags & LOOKUP_ROOT))
738 nd->root.mnt = NULL;
739 return -ECHILD;
740}
741
742static int unlazy_link(struct nameidata *nd, struct path *link, unsigned seq)
743{
744 if (unlikely(!legitimize_path(nd, link, seq))) {
745 drop_links(nd);
746 nd->depth = 0;
747 nd->flags &= ~LOOKUP_RCU;
748 nd->path.mnt = NULL;
749 nd->path.dentry = NULL;
750 if (!(nd->flags & LOOKUP_ROOT))
751 nd->root.mnt = NULL;
752 rcu_read_unlock();
753 } else if (likely(unlazy_walk(nd, NULL, 0)) == 0) {
754 return 0;
755 }
756 path_put(link);
757 return -ECHILD;
758}
759
760static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
761{
762 return dentry->d_op->d_revalidate(dentry, flags);
763}
764
765/**
766 * complete_walk - successful completion of path walk
767 * @nd: pointer nameidata
768 *
769 * If we had been in RCU mode, drop out of it and legitimize nd->path.
770 * Revalidate the final result, unless we'd already done that during
771 * the path walk or the filesystem doesn't ask for it. Return 0 on
772 * success, -error on failure. In case of failure caller does not
773 * need to drop nd->path.
774 */
775static int complete_walk(struct nameidata *nd)
776{
777 struct dentry *dentry = nd->path.dentry;
778 int status;
779
780 if (nd->flags & LOOKUP_RCU) {
781 if (!(nd->flags & LOOKUP_ROOT))
782 nd->root.mnt = NULL;
783 if (unlikely(unlazy_walk(nd, NULL, 0)))
784 return -ECHILD;
785 }
786
787 if (likely(!(nd->flags & LOOKUP_JUMPED)))
788 return 0;
789
790 if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE)))
791 return 0;
792
793 status = dentry->d_op->d_weak_revalidate(dentry, nd->flags);
794 if (status > 0)
795 return 0;
796
797 if (!status)
798 status = -ESTALE;
799
800 return status;
801}
802
803static void set_root(struct nameidata *nd)
804{
805 struct fs_struct *fs = current->fs;
806
807 if (nd->flags & LOOKUP_RCU) {
808 unsigned seq;
809
810 do {
811 seq = read_seqcount_begin(&fs->seq);
812 nd->root = fs->root;
813 nd->root_seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
814 } while (read_seqcount_retry(&fs->seq, seq));
815 } else {
816 get_fs_root(fs, &nd->root);
817 }
818}
819
820static void path_put_conditional(struct path *path, struct nameidata *nd)
821{
822 dput(path->dentry);
823 if (path->mnt != nd->path.mnt)
824 mntput(path->mnt);
825}
826
827static inline void path_to_nameidata(const struct path *path,
828 struct nameidata *nd)
829{
830 if (!(nd->flags & LOOKUP_RCU)) {
831 dput(nd->path.dentry);
832 if (nd->path.mnt != path->mnt)
833 mntput(nd->path.mnt);
834 }
835 nd->path.mnt = path->mnt;
836 nd->path.dentry = path->dentry;
837}
838
839static int nd_jump_root(struct nameidata *nd)
840{
841 if (nd->flags & LOOKUP_RCU) {
842 struct dentry *d;
843 nd->path = nd->root;
844 d = nd->path.dentry;
845 nd->inode = d->d_inode;
846 nd->seq = nd->root_seq;
847 if (unlikely(read_seqcount_retry(&d->d_seq, nd->seq)))
848 return -ECHILD;
849 } else {
850 path_put(&nd->path);
851 nd->path = nd->root;
852 path_get(&nd->path);
853 nd->inode = nd->path.dentry->d_inode;
854 }
855 nd->flags |= LOOKUP_JUMPED;
856 return 0;
857}
858
859/*
860 * Helper to directly jump to a known parsed path from ->get_link,
861 * caller must have taken a reference to path beforehand.
862 */
863void nd_jump_link(struct path *path)
864{
865 struct nameidata *nd = current->nameidata;
866 path_put(&nd->path);
867
868 nd->path = *path;
869 nd->inode = nd->path.dentry->d_inode;
870 nd->flags |= LOOKUP_JUMPED;
871}
872
873static inline void put_link(struct nameidata *nd)
874{
875 struct saved *last = nd->stack + --nd->depth;
876 do_delayed_call(&last->done);
877 if (!(nd->flags & LOOKUP_RCU))
878 path_put(&last->link);
879}
880
881int sysctl_protected_symlinks __read_mostly = 0;
882int sysctl_protected_hardlinks __read_mostly = 0;
883
884/**
885 * may_follow_link - Check symlink following for unsafe situations
886 * @nd: nameidata pathwalk data
887 *
888 * In the case of the sysctl_protected_symlinks sysctl being enabled,
889 * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
890 * in a sticky world-writable directory. This is to protect privileged
891 * processes from failing races against path names that may change out
892 * from under them by way of other users creating malicious symlinks.
893 * It will permit symlinks to be followed only when outside a sticky
894 * world-writable directory, or when the uid of the symlink and follower
895 * match, or when the directory owner matches the symlink's owner.
896 *
897 * Returns 0 if following the symlink is allowed, -ve on error.
898 */
899static inline int may_follow_link(struct nameidata *nd)
900{
901 const struct inode *inode;
902 const struct inode *parent;
903
904 if (!sysctl_protected_symlinks)
905 return 0;
906
907 /* Allowed if owner and follower match. */
908 inode = nd->link_inode;
909 if (uid_eq(current_cred()->fsuid, inode->i_uid))
910 return 0;
911
912 /* Allowed if parent directory not sticky and world-writable. */
913 parent = nd->inode;
914 if ((parent->i_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH))
915 return 0;
916
917 /* Allowed if parent directory and link owner match. */
918 if (uid_eq(parent->i_uid, inode->i_uid))
919 return 0;
920
921 if (nd->flags & LOOKUP_RCU)
922 return -ECHILD;
923
924 audit_log_link_denied("follow_link", &nd->stack[0].link);
925 return -EACCES;
926}
927
928/**
929 * safe_hardlink_source - Check for safe hardlink conditions
930 * @inode: the source inode to hardlink from
931 *
932 * Return false if at least one of the following conditions:
933 * - inode is not a regular file
934 * - inode is setuid
935 * - inode is setgid and group-exec
936 * - access failure for read and write
937 *
938 * Otherwise returns true.
939 */
940static bool safe_hardlink_source(struct inode *inode)
941{
942 umode_t mode = inode->i_mode;
943
944 /* Special files should not get pinned to the filesystem. */
945 if (!S_ISREG(mode))
946 return false;
947
948 /* Setuid files should not get pinned to the filesystem. */
949 if (mode & S_ISUID)
950 return false;
951
952 /* Executable setgid files should not get pinned to the filesystem. */
953 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP))
954 return false;
955
956 /* Hardlinking to unreadable or unwritable sources is dangerous. */
957 if (inode_permission(inode, MAY_READ | MAY_WRITE))
958 return false;
959
960 return true;
961}
962
963/**
964 * may_linkat - Check permissions for creating a hardlink
965 * @link: the source to hardlink from
966 *
967 * Block hardlink when all of:
968 * - sysctl_protected_hardlinks enabled
969 * - fsuid does not match inode
970 * - hardlink source is unsafe (see safe_hardlink_source() above)
971 * - not CAP_FOWNER in a namespace with the inode owner uid mapped
972 *
973 * Returns 0 if successful, -ve on error.
974 */
975static int may_linkat(struct path *link)
976{
977 struct inode *inode;
978
979 if (!sysctl_protected_hardlinks)
980 return 0;
981
982 inode = link->dentry->d_inode;
983
984 /* Source inode owner (or CAP_FOWNER) can hardlink all they like,
985 * otherwise, it must be a safe source.
986 */
987 if (inode_owner_or_capable(inode) || safe_hardlink_source(inode))
988 return 0;
989
990 audit_log_link_denied("linkat", link);
991 return -EPERM;
992}
993
994static __always_inline
995const char *get_link(struct nameidata *nd)
996{
997 struct saved *last = nd->stack + nd->depth - 1;
998 struct dentry *dentry = last->link.dentry;
999 struct inode *inode = nd->link_inode;
1000 int error;
1001 const char *res;
1002
1003 if (!(nd->flags & LOOKUP_RCU)) {
1004 touch_atime(&last->link);
1005 cond_resched();
1006 } else if (atime_needs_update(&last->link, inode)) {
1007 if (unlikely(unlazy_walk(nd, NULL, 0)))
1008 return ERR_PTR(-ECHILD);
1009 touch_atime(&last->link);
1010 }
1011
1012 error = security_inode_follow_link(dentry, inode,
1013 nd->flags & LOOKUP_RCU);
1014 if (unlikely(error))
1015 return ERR_PTR(error);
1016
1017 nd->last_type = LAST_BIND;
1018 res = inode->i_link;
1019 if (!res) {
1020 const char * (*get)(struct dentry *, struct inode *,
1021 struct delayed_call *);
1022 get = inode->i_op->get_link;
1023 if (nd->flags & LOOKUP_RCU) {
1024 res = get(NULL, inode, &last->done);
1025 if (res == ERR_PTR(-ECHILD)) {
1026 if (unlikely(unlazy_walk(nd, NULL, 0)))
1027 return ERR_PTR(-ECHILD);
1028 res = get(dentry, inode, &last->done);
1029 }
1030 } else {
1031 res = get(dentry, inode, &last->done);
1032 }
1033 if (IS_ERR_OR_NULL(res))
1034 return res;
1035 }
1036 if (*res == '/') {
1037 if (!nd->root.mnt)
1038 set_root(nd);
1039 if (unlikely(nd_jump_root(nd)))
1040 return ERR_PTR(-ECHILD);
1041 while (unlikely(*++res == '/'))
1042 ;
1043 }
1044 if (!*res)
1045 res = NULL;
1046 return res;
1047}
1048
1049/*
1050 * follow_up - Find the mountpoint of path's vfsmount
1051 *
1052 * Given a path, find the mountpoint of its source file system.
1053 * Replace @path with the path of the mountpoint in the parent mount.
1054 * Up is towards /.
1055 *
1056 * Return 1 if we went up a level and 0 if we were already at the
1057 * root.
1058 */
1059int follow_up(struct path *path)
1060{
1061 struct mount *mnt = real_mount(path->mnt);
1062 struct mount *parent;
1063 struct dentry *mountpoint;
1064
1065 read_seqlock_excl(&mount_lock);
1066 parent = mnt->mnt_parent;
1067 if (parent == mnt) {
1068 read_sequnlock_excl(&mount_lock);
1069 return 0;
1070 }
1071 mntget(&parent->mnt);
1072 mountpoint = dget(mnt->mnt_mountpoint);
1073 read_sequnlock_excl(&mount_lock);
1074 dput(path->dentry);
1075 path->dentry = mountpoint;
1076 mntput(path->mnt);
1077 path->mnt = &parent->mnt;
1078 return 1;
1079}
1080EXPORT_SYMBOL(follow_up);
1081
1082/*
1083 * Perform an automount
1084 * - return -EISDIR to tell follow_managed() to stop and return the path we
1085 * were called with.
1086 */
1087static int follow_automount(struct path *path, struct nameidata *nd,
1088 bool *need_mntput)
1089{
1090 struct vfsmount *mnt;
1091 int err;
1092
1093 if (!path->dentry->d_op || !path->dentry->d_op->d_automount)
1094 return -EREMOTE;
1095
1096 /* We don't want to mount if someone's just doing a stat -
1097 * unless they're stat'ing a directory and appended a '/' to
1098 * the name.
1099 *
1100 * We do, however, want to mount if someone wants to open or
1101 * create a file of any type under the mountpoint, wants to
1102 * traverse through the mountpoint or wants to open the
1103 * mounted directory. Also, autofs may mark negative dentries
1104 * as being automount points. These will need the attentions
1105 * of the daemon to instantiate them before they can be used.
1106 */
1107 if (!(nd->flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
1108 LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
1109 path->dentry->d_inode)
1110 return -EISDIR;
1111
1112 nd->total_link_count++;
1113 if (nd->total_link_count >= 40)
1114 return -ELOOP;
1115
1116 mnt = path->dentry->d_op->d_automount(path);
1117 if (IS_ERR(mnt)) {
1118 /*
1119 * The filesystem is allowed to return -EISDIR here to indicate
1120 * it doesn't want to automount. For instance, autofs would do
1121 * this so that its userspace daemon can mount on this dentry.
1122 *
1123 * However, we can only permit this if it's a terminal point in
1124 * the path being looked up; if it wasn't then the remainder of
1125 * the path is inaccessible and we should say so.
1126 */
1127 if (PTR_ERR(mnt) == -EISDIR && (nd->flags & LOOKUP_PARENT))
1128 return -EREMOTE;
1129 return PTR_ERR(mnt);
1130 }
1131
1132 if (!mnt) /* mount collision */
1133 return 0;
1134
1135 if (!*need_mntput) {
1136 /* lock_mount() may release path->mnt on error */
1137 mntget(path->mnt);
1138 *need_mntput = true;
1139 }
1140 err = finish_automount(mnt, path);
1141
1142 switch (err) {
1143 case -EBUSY:
1144 /* Someone else made a mount here whilst we were busy */
1145 return 0;
1146 case 0:
1147 path_put(path);
1148 path->mnt = mnt;
1149 path->dentry = dget(mnt->mnt_root);
1150 return 0;
1151 default:
1152 return err;
1153 }
1154
1155}
1156
1157/*
1158 * Handle a dentry that is managed in some way.
1159 * - Flagged for transit management (autofs)
1160 * - Flagged as mountpoint
1161 * - Flagged as automount point
1162 *
1163 * This may only be called in refwalk mode.
1164 *
1165 * Serialization is taken care of in namespace.c
1166 */
1167static int follow_managed(struct path *path, struct nameidata *nd)
1168{
1169 struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */
1170 unsigned managed;
1171 bool need_mntput = false;
1172 int ret = 0;
1173
1174 /* Given that we're not holding a lock here, we retain the value in a
1175 * local variable for each dentry as we look at it so that we don't see
1176 * the components of that value change under us */
1177 while (managed = ACCESS_ONCE(path->dentry->d_flags),
1178 managed &= DCACHE_MANAGED_DENTRY,
1179 unlikely(managed != 0)) {
1180 /* Allow the filesystem to manage the transit without i_mutex
1181 * being held. */
1182 if (managed & DCACHE_MANAGE_TRANSIT) {
1183 BUG_ON(!path->dentry->d_op);
1184 BUG_ON(!path->dentry->d_op->d_manage);
1185 ret = path->dentry->d_op->d_manage(path->dentry, false);
1186 if (ret < 0)
1187 break;
1188 }
1189
1190 /* Transit to a mounted filesystem. */
1191 if (managed & DCACHE_MOUNTED) {
1192 struct vfsmount *mounted = lookup_mnt(path);
1193 if (mounted) {
1194 dput(path->dentry);
1195 if (need_mntput)
1196 mntput(path->mnt);
1197 path->mnt = mounted;
1198 path->dentry = dget(mounted->mnt_root);
1199 need_mntput = true;
1200 continue;
1201 }
1202
1203 /* Something is mounted on this dentry in another
1204 * namespace and/or whatever was mounted there in this
1205 * namespace got unmounted before lookup_mnt() could
1206 * get it */
1207 }
1208
1209 /* Handle an automount point */
1210 if (managed & DCACHE_NEED_AUTOMOUNT) {
1211 ret = follow_automount(path, nd, &need_mntput);
1212 if (ret < 0)
1213 break;
1214 continue;
1215 }
1216
1217 /* We didn't change the current path point */
1218 break;
1219 }
1220
1221 if (need_mntput && path->mnt == mnt)
1222 mntput(path->mnt);
1223 if (ret == -EISDIR || !ret)
1224 ret = 1;
1225 if (need_mntput)
1226 nd->flags |= LOOKUP_JUMPED;
1227 if (unlikely(ret < 0))
1228 path_put_conditional(path, nd);
1229 return ret;
1230}
1231
1232int follow_down_one(struct path *path)
1233{
1234 struct vfsmount *mounted;
1235
1236 mounted = lookup_mnt(path);
1237 if (mounted) {
1238 dput(path->dentry);
1239 mntput(path->mnt);
1240 path->mnt = mounted;
1241 path->dentry = dget(mounted->mnt_root);
1242 return 1;
1243 }
1244 return 0;
1245}
1246EXPORT_SYMBOL(follow_down_one);
1247
1248static inline int managed_dentry_rcu(struct dentry *dentry)
1249{
1250 return (dentry->d_flags & DCACHE_MANAGE_TRANSIT) ?
1251 dentry->d_op->d_manage(dentry, true) : 0;
1252}
1253
1254/*
1255 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
1256 * we meet a managed dentry that would need blocking.
1257 */
1258static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
1259 struct inode **inode, unsigned *seqp)
1260{
1261 for (;;) {
1262 struct mount *mounted;
1263 /*
1264 * Don't forget we might have a non-mountpoint managed dentry
1265 * that wants to block transit.
1266 */
1267 switch (managed_dentry_rcu(path->dentry)) {
1268 case -ECHILD:
1269 default:
1270 return false;
1271 case -EISDIR:
1272 return true;
1273 case 0:
1274 break;
1275 }
1276
1277 if (!d_mountpoint(path->dentry))
1278 return !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT);
1279
1280 mounted = __lookup_mnt(path->mnt, path->dentry);
1281 if (!mounted)
1282 break;
1283 path->mnt = &mounted->mnt;
1284 path->dentry = mounted->mnt.mnt_root;
1285 nd->flags |= LOOKUP_JUMPED;
1286 *seqp = read_seqcount_begin(&path->dentry->d_seq);
1287 /*
1288 * Update the inode too. We don't need to re-check the
1289 * dentry sequence number here after this d_inode read,
1290 * because a mount-point is always pinned.
1291 */
1292 *inode = path->dentry->d_inode;
1293 }
1294 return !read_seqretry(&mount_lock, nd->m_seq) &&
1295 !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT);
1296}
1297
1298static int follow_dotdot_rcu(struct nameidata *nd)
1299{
1300 struct inode *inode = nd->inode;
1301
1302 while (1) {
1303 if (path_equal(&nd->path, &nd->root))
1304 break;
1305 if (nd->path.dentry != nd->path.mnt->mnt_root) {
1306 struct dentry *old = nd->path.dentry;
1307 struct dentry *parent = old->d_parent;
1308 unsigned seq;
1309
1310 inode = parent->d_inode;
1311 seq = read_seqcount_begin(&parent->d_seq);
1312 if (unlikely(read_seqcount_retry(&old->d_seq, nd->seq)))
1313 return -ECHILD;
1314 nd->path.dentry = parent;
1315 nd->seq = seq;
1316 if (unlikely(!path_connected(&nd->path)))
1317 return -ENOENT;
1318 break;
1319 } else {
1320 struct mount *mnt = real_mount(nd->path.mnt);
1321 struct mount *mparent = mnt->mnt_parent;
1322 struct dentry *mountpoint = mnt->mnt_mountpoint;
1323 struct inode *inode2 = mountpoint->d_inode;
1324 unsigned seq = read_seqcount_begin(&mountpoint->d_seq);
1325 if (unlikely(read_seqretry(&mount_lock, nd->m_seq)))
1326 return -ECHILD;
1327 if (&mparent->mnt == nd->path.mnt)
1328 break;
1329 /* we know that mountpoint was pinned */
1330 nd->path.dentry = mountpoint;
1331 nd->path.mnt = &mparent->mnt;
1332 inode = inode2;
1333 nd->seq = seq;
1334 }
1335 }
1336 while (unlikely(d_mountpoint(nd->path.dentry))) {
1337 struct mount *mounted;
1338 mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry);
1339 if (unlikely(read_seqretry(&mount_lock, nd->m_seq)))
1340 return -ECHILD;
1341 if (!mounted)
1342 break;
1343 nd->path.mnt = &mounted->mnt;
1344 nd->path.dentry = mounted->mnt.mnt_root;
1345 inode = nd->path.dentry->d_inode;
1346 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
1347 }
1348 nd->inode = inode;
1349 return 0;
1350}
1351
1352/*
1353 * Follow down to the covering mount currently visible to userspace. At each
1354 * point, the filesystem owning that dentry may be queried as to whether the
1355 * caller is permitted to proceed or not.
1356 */
1357int follow_down(struct path *path)
1358{
1359 unsigned managed;
1360 int ret;
1361
1362 while (managed = ACCESS_ONCE(path->dentry->d_flags),
1363 unlikely(managed & DCACHE_MANAGED_DENTRY)) {
1364 /* Allow the filesystem to manage the transit without i_mutex
1365 * being held.
1366 *
1367 * We indicate to the filesystem if someone is trying to mount
1368 * something here. This gives autofs the chance to deny anyone
1369 * other than its daemon the right to mount on its
1370 * superstructure.
1371 *
1372 * The filesystem may sleep at this point.
1373 */
1374 if (managed & DCACHE_MANAGE_TRANSIT) {
1375 BUG_ON(!path->dentry->d_op);
1376 BUG_ON(!path->dentry->d_op->d_manage);
1377 ret = path->dentry->d_op->d_manage(
1378 path->dentry, false);
1379 if (ret < 0)
1380 return ret == -EISDIR ? 0 : ret;
1381 }
1382
1383 /* Transit to a mounted filesystem. */
1384 if (managed & DCACHE_MOUNTED) {
1385 struct vfsmount *mounted = lookup_mnt(path);
1386 if (!mounted)
1387 break;
1388 dput(path->dentry);
1389 mntput(path->mnt);
1390 path->mnt = mounted;
1391 path->dentry = dget(mounted->mnt_root);
1392 continue;
1393 }
1394
1395 /* Don't handle automount points here */
1396 break;
1397 }
1398 return 0;
1399}
1400EXPORT_SYMBOL(follow_down);
1401
1402/*
1403 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1404 */
1405static void follow_mount(struct path *path)
1406{
1407 while (d_mountpoint(path->dentry)) {
1408 struct vfsmount *mounted = lookup_mnt(path);
1409 if (!mounted)
1410 break;
1411 dput(path->dentry);
1412 mntput(path->mnt);
1413 path->mnt = mounted;
1414 path->dentry = dget(mounted->mnt_root);
1415 }
1416}
1417
1418static int follow_dotdot(struct nameidata *nd)
1419{
1420 while(1) {
1421 struct dentry *old = nd->path.dentry;
1422
1423 if (nd->path.dentry == nd->root.dentry &&
1424 nd->path.mnt == nd->root.mnt) {
1425 break;
1426 }
1427 if (nd->path.dentry != nd->path.mnt->mnt_root) {
1428 /* rare case of legitimate dget_parent()... */
1429 nd->path.dentry = dget_parent(nd->path.dentry);
1430 dput(old);
1431 if (unlikely(!path_connected(&nd->path)))
1432 return -ENOENT;
1433 break;
1434 }
1435 if (!follow_up(&nd->path))
1436 break;
1437 }
1438 follow_mount(&nd->path);
1439 nd->inode = nd->path.dentry->d_inode;
1440 return 0;
1441}
1442
1443/*
1444 * This looks up the name in dcache, possibly revalidates the old dentry and
1445 * allocates a new one if not found or not valid. In the need_lookup argument
1446 * returns whether i_op->lookup is necessary.
1447 */
1448static struct dentry *lookup_dcache(const struct qstr *name,
1449 struct dentry *dir,
1450 unsigned int flags)
1451{
1452 struct dentry *dentry;
1453 int error;
1454
1455 dentry = d_lookup(dir, name);
1456 if (dentry) {
1457 if (dentry->d_flags & DCACHE_OP_REVALIDATE) {
1458 error = d_revalidate(dentry, flags);
1459 if (unlikely(error <= 0)) {
1460 if (!error)
1461 d_invalidate(dentry);
1462 dput(dentry);
1463 return ERR_PTR(error);
1464 }
1465 }
1466 }
1467 return dentry;
1468}
1469
1470/*
1471 * Call i_op->lookup on the dentry. The dentry must be negative and
1472 * unhashed.
1473 *
1474 * dir->d_inode->i_mutex must be held
1475 */
1476static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry,
1477 unsigned int flags)
1478{
1479 struct dentry *old;
1480
1481 /* Don't create child dentry for a dead directory. */
1482 if (unlikely(IS_DEADDIR(dir))) {
1483 dput(dentry);
1484 return ERR_PTR(-ENOENT);
1485 }
1486
1487 old = dir->i_op->lookup(dir, dentry, flags);
1488 if (unlikely(old)) {
1489 dput(dentry);
1490 dentry = old;
1491 }
1492 return dentry;
1493}
1494
1495static struct dentry *__lookup_hash(const struct qstr *name,
1496 struct dentry *base, unsigned int flags)
1497{
1498 struct dentry *dentry = lookup_dcache(name, base, flags);
1499
1500 if (dentry)
1501 return dentry;
1502
1503 dentry = d_alloc(base, name);
1504 if (unlikely(!dentry))
1505 return ERR_PTR(-ENOMEM);
1506
1507 return lookup_real(base->d_inode, dentry, flags);
1508}
1509
1510static int lookup_fast(struct nameidata *nd,
1511 struct path *path, struct inode **inode,
1512 unsigned *seqp)
1513{
1514 struct vfsmount *mnt = nd->path.mnt;
1515 struct dentry *dentry, *parent = nd->path.dentry;
1516 int status = 1;
1517 int err;
1518
1519 /*
1520 * Rename seqlock is not required here because in the off chance
1521 * of a false negative due to a concurrent rename, the caller is
1522 * going to fall back to non-racy lookup.
1523 */
1524 if (nd->flags & LOOKUP_RCU) {
1525 unsigned seq;
1526 bool negative;
1527 dentry = __d_lookup_rcu(parent, &nd->last, &seq);
1528 if (unlikely(!dentry)) {
1529 if (unlazy_walk(nd, NULL, 0))
1530 return -ECHILD;
1531 return 0;
1532 }
1533
1534 /*
1535 * This sequence count validates that the inode matches
1536 * the dentry name information from lookup.
1537 */
1538 *inode = d_backing_inode(dentry);
1539 negative = d_is_negative(dentry);
1540 if (unlikely(read_seqcount_retry(&dentry->d_seq, seq)))
1541 return -ECHILD;
1542
1543 /*
1544 * This sequence count validates that the parent had no
1545 * changes while we did the lookup of the dentry above.
1546 *
1547 * The memory barrier in read_seqcount_begin of child is
1548 * enough, we can use __read_seqcount_retry here.
1549 */
1550 if (unlikely(__read_seqcount_retry(&parent->d_seq, nd->seq)))
1551 return -ECHILD;
1552
1553 *seqp = seq;
1554 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE))
1555 status = d_revalidate(dentry, nd->flags);
1556 if (unlikely(status <= 0)) {
1557 if (unlazy_walk(nd, dentry, seq))
1558 return -ECHILD;
1559 if (status == -ECHILD)
1560 status = d_revalidate(dentry, nd->flags);
1561 } else {
1562 /*
1563 * Note: do negative dentry check after revalidation in
1564 * case that drops it.
1565 */
1566 if (unlikely(negative))
1567 return -ENOENT;
1568 path->mnt = mnt;
1569 path->dentry = dentry;
1570 if (likely(__follow_mount_rcu(nd, path, inode, seqp)))
1571 return 1;
1572 if (unlazy_walk(nd, dentry, seq))
1573 return -ECHILD;
1574 }
1575 } else {
1576 dentry = __d_lookup(parent, &nd->last);
1577 if (unlikely(!dentry))
1578 return 0;
1579 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE))
1580 status = d_revalidate(dentry, nd->flags);
1581 }
1582 if (unlikely(status <= 0)) {
1583 if (!status)
1584 d_invalidate(dentry);
1585 dput(dentry);
1586 return status;
1587 }
1588 if (unlikely(d_is_negative(dentry))) {
1589 dput(dentry);
1590 return -ENOENT;
1591 }
1592
1593 path->mnt = mnt;
1594 path->dentry = dentry;
1595 err = follow_managed(path, nd);
1596 if (likely(err > 0))
1597 *inode = d_backing_inode(path->dentry);
1598 return err;
1599}
1600
1601/* Fast lookup failed, do it the slow way */
1602static struct dentry *lookup_slow(const struct qstr *name,
1603 struct dentry *dir,
1604 unsigned int flags)
1605{
1606 struct dentry *dentry;
1607 inode_lock(dir->d_inode);
1608 dentry = d_lookup(dir, name);
1609 if (unlikely(dentry)) {
1610 if ((dentry->d_flags & DCACHE_OP_REVALIDATE) &&
1611 !(flags & LOOKUP_NO_REVAL)) {
1612 int error = d_revalidate(dentry, flags);
1613 if (unlikely(error <= 0)) {
1614 if (!error)
1615 d_invalidate(dentry);
1616 dput(dentry);
1617 dentry = ERR_PTR(error);
1618 }
1619 }
1620 if (dentry) {
1621 inode_unlock(dir->d_inode);
1622 return dentry;
1623 }
1624 }
1625 dentry = d_alloc(dir, name);
1626 if (unlikely(!dentry)) {
1627 inode_unlock(dir->d_inode);
1628 return ERR_PTR(-ENOMEM);
1629 }
1630 dentry = lookup_real(dir->d_inode, dentry, flags);
1631 inode_unlock(dir->d_inode);
1632 return dentry;
1633}
1634
1635static inline int may_lookup(struct nameidata *nd)
1636{
1637 if (nd->flags & LOOKUP_RCU) {
1638 int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
1639 if (err != -ECHILD)
1640 return err;
1641 if (unlazy_walk(nd, NULL, 0))
1642 return -ECHILD;
1643 }
1644 return inode_permission(nd->inode, MAY_EXEC);
1645}
1646
1647static inline int handle_dots(struct nameidata *nd, int type)
1648{
1649 if (type == LAST_DOTDOT) {
1650 if (!nd->root.mnt)
1651 set_root(nd);
1652 if (nd->flags & LOOKUP_RCU) {
1653 return follow_dotdot_rcu(nd);
1654 } else
1655 return follow_dotdot(nd);
1656 }
1657 return 0;
1658}
1659
1660static int pick_link(struct nameidata *nd, struct path *link,
1661 struct inode *inode, unsigned seq)
1662{
1663 int error;
1664 struct saved *last;
1665 if (unlikely(nd->total_link_count++ >= MAXSYMLINKS)) {
1666 path_to_nameidata(link, nd);
1667 return -ELOOP;
1668 }
1669 if (!(nd->flags & LOOKUP_RCU)) {
1670 if (link->mnt == nd->path.mnt)
1671 mntget(link->mnt);
1672 }
1673 error = nd_alloc_stack(nd);
1674 if (unlikely(error)) {
1675 if (error == -ECHILD) {
1676 if (unlikely(unlazy_link(nd, link, seq)))
1677 return -ECHILD;
1678 error = nd_alloc_stack(nd);
1679 }
1680 if (error) {
1681 path_put(link);
1682 return error;
1683 }
1684 }
1685
1686 last = nd->stack + nd->depth++;
1687 last->link = *link;
1688 clear_delayed_call(&last->done);
1689 nd->link_inode = inode;
1690 last->seq = seq;
1691 return 1;
1692}
1693
1694/*
1695 * Do we need to follow links? We _really_ want to be able
1696 * to do this check without having to look at inode->i_op,
1697 * so we keep a cache of "no, this doesn't need follow_link"
1698 * for the common case.
1699 */
1700static inline int should_follow_link(struct nameidata *nd, struct path *link,
1701 int follow,
1702 struct inode *inode, unsigned seq)
1703{
1704 if (likely(!d_is_symlink(link->dentry)))
1705 return 0;
1706 if (!follow)
1707 return 0;
1708 /* make sure that d_is_symlink above matches inode */
1709 if (nd->flags & LOOKUP_RCU) {
1710 if (read_seqcount_retry(&link->dentry->d_seq, seq))
1711 return -ECHILD;
1712 }
1713 return pick_link(nd, link, inode, seq);
1714}
1715
1716enum {WALK_GET = 1, WALK_PUT = 2};
1717
1718static int walk_component(struct nameidata *nd, int flags)
1719{
1720 struct path path;
1721 struct inode *inode;
1722 unsigned seq;
1723 int err;
1724 /*
1725 * "." and ".." are special - ".." especially so because it has
1726 * to be able to know about the current root directory and
1727 * parent relationships.
1728 */
1729 if (unlikely(nd->last_type != LAST_NORM)) {
1730 err = handle_dots(nd, nd->last_type);
1731 if (flags & WALK_PUT)
1732 put_link(nd);
1733 return err;
1734 }
1735 err = lookup_fast(nd, &path, &inode, &seq);
1736 if (unlikely(err <= 0)) {
1737 if (err < 0)
1738 return err;
1739 path.dentry = lookup_slow(&nd->last, nd->path.dentry,
1740 nd->flags);
1741 if (IS_ERR(path.dentry))
1742 return PTR_ERR(path.dentry);
1743
1744 path.mnt = nd->path.mnt;
1745 err = follow_managed(&path, nd);
1746 if (unlikely(err < 0))
1747 return err;
1748
1749 if (unlikely(d_is_negative(path.dentry))) {
1750 path_to_nameidata(&path, nd);
1751 return -ENOENT;
1752 }
1753
1754 seq = 0; /* we are already out of RCU mode */
1755 inode = d_backing_inode(path.dentry);
1756 }
1757
1758 if (flags & WALK_PUT)
1759 put_link(nd);
1760 err = should_follow_link(nd, &path, flags & WALK_GET, inode, seq);
1761 if (unlikely(err))
1762 return err;
1763 path_to_nameidata(&path, nd);
1764 nd->inode = inode;
1765 nd->seq = seq;
1766 return 0;
1767}
1768
1769/*
1770 * We can do the critical dentry name comparison and hashing
1771 * operations one word at a time, but we are limited to:
1772 *
1773 * - Architectures with fast unaligned word accesses. We could
1774 * do a "get_unaligned()" if this helps and is sufficiently
1775 * fast.
1776 *
1777 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
1778 * do not trap on the (extremely unlikely) case of a page
1779 * crossing operation.
1780 *
1781 * - Furthermore, we need an efficient 64-bit compile for the
1782 * 64-bit case in order to generate the "number of bytes in
1783 * the final mask". Again, that could be replaced with a
1784 * efficient population count instruction or similar.
1785 */
1786#ifdef CONFIG_DCACHE_WORD_ACCESS
1787
1788#include <asm/word-at-a-time.h>
1789
1790#ifdef CONFIG_64BIT
1791
1792static inline unsigned int fold_hash(unsigned long hash)
1793{
1794 return hash_64(hash, 32);
1795}
1796
1797#else /* 32-bit case */
1798
1799#define fold_hash(x) (x)
1800
1801#endif
1802
1803unsigned int full_name_hash(const unsigned char *name, unsigned int len)
1804{
1805 unsigned long a, mask;
1806 unsigned long hash = 0;
1807
1808 for (;;) {
1809 a = load_unaligned_zeropad(name);
1810 if (len < sizeof(unsigned long))
1811 break;
1812 hash += a;
1813 hash *= 9;
1814 name += sizeof(unsigned long);
1815 len -= sizeof(unsigned long);
1816 if (!len)
1817 goto done;
1818 }
1819 mask = bytemask_from_count(len);
1820 hash += mask & a;
1821done:
1822 return fold_hash(hash);
1823}
1824EXPORT_SYMBOL(full_name_hash);
1825
1826/*
1827 * Calculate the length and hash of the path component, and
1828 * return the "hash_len" as the result.
1829 */
1830static inline u64 hash_name(const char *name)
1831{
1832 unsigned long a, b, adata, bdata, mask, hash, len;
1833 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
1834
1835 hash = a = 0;
1836 len = -sizeof(unsigned long);
1837 do {
1838 hash = (hash + a) * 9;
1839 len += sizeof(unsigned long);
1840 a = load_unaligned_zeropad(name+len);
1841 b = a ^ REPEAT_BYTE('/');
1842 } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants)));
1843
1844 adata = prep_zero_mask(a, adata, &constants);
1845 bdata = prep_zero_mask(b, bdata, &constants);
1846
1847 mask = create_zero_mask(adata | bdata);
1848
1849 hash += a & zero_bytemask(mask);
1850 len += find_zero(mask);
1851 return hashlen_create(fold_hash(hash), len);
1852}
1853
1854#else
1855
1856unsigned int full_name_hash(const unsigned char *name, unsigned int len)
1857{
1858 unsigned long hash = init_name_hash();
1859 while (len--)
1860 hash = partial_name_hash(*name++, hash);
1861 return end_name_hash(hash);
1862}
1863EXPORT_SYMBOL(full_name_hash);
1864
1865/*
1866 * We know there's a real path component here of at least
1867 * one character.
1868 */
1869static inline u64 hash_name(const char *name)
1870{
1871 unsigned long hash = init_name_hash();
1872 unsigned long len = 0, c;
1873
1874 c = (unsigned char)*name;
1875 do {
1876 len++;
1877 hash = partial_name_hash(c, hash);
1878 c = (unsigned char)name[len];
1879 } while (c && c != '/');
1880 return hashlen_create(end_name_hash(hash), len);
1881}
1882
1883#endif
1884
1885/*
1886 * Name resolution.
1887 * This is the basic name resolution function, turning a pathname into
1888 * the final dentry. We expect 'base' to be positive and a directory.
1889 *
1890 * Returns 0 and nd will have valid dentry and mnt on success.
1891 * Returns error and drops reference to input namei data on failure.
1892 */
1893static int link_path_walk(const char *name, struct nameidata *nd)
1894{
1895 int err;
1896
1897 while (*name=='/')
1898 name++;
1899 if (!*name)
1900 return 0;
1901
1902 /* At this point we know we have a real path component. */
1903 for(;;) {
1904 u64 hash_len;
1905 int type;
1906
1907 err = may_lookup(nd);
1908 if (err)
1909 return err;
1910
1911 hash_len = hash_name(name);
1912
1913 type = LAST_NORM;
1914 if (name[0] == '.') switch (hashlen_len(hash_len)) {
1915 case 2:
1916 if (name[1] == '.') {
1917 type = LAST_DOTDOT;
1918 nd->flags |= LOOKUP_JUMPED;
1919 }
1920 break;
1921 case 1:
1922 type = LAST_DOT;
1923 }
1924 if (likely(type == LAST_NORM)) {
1925 struct dentry *parent = nd->path.dentry;
1926 nd->flags &= ~LOOKUP_JUMPED;
1927 if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
1928 struct qstr this = { { .hash_len = hash_len }, .name = name };
1929 err = parent->d_op->d_hash(parent, &this);
1930 if (err < 0)
1931 return err;
1932 hash_len = this.hash_len;
1933 name = this.name;
1934 }
1935 }
1936
1937 nd->last.hash_len = hash_len;
1938 nd->last.name = name;
1939 nd->last_type = type;
1940
1941 name += hashlen_len(hash_len);
1942 if (!*name)
1943 goto OK;
1944 /*
1945 * If it wasn't NUL, we know it was '/'. Skip that
1946 * slash, and continue until no more slashes.
1947 */
1948 do {
1949 name++;
1950 } while (unlikely(*name == '/'));
1951 if (unlikely(!*name)) {
1952OK:
1953 /* pathname body, done */
1954 if (!nd->depth)
1955 return 0;
1956 name = nd->stack[nd->depth - 1].name;
1957 /* trailing symlink, done */
1958 if (!name)
1959 return 0;
1960 /* last component of nested symlink */
1961 err = walk_component(nd, WALK_GET | WALK_PUT);
1962 } else {
1963 err = walk_component(nd, WALK_GET);
1964 }
1965 if (err < 0)
1966 return err;
1967
1968 if (err) {
1969 const char *s = get_link(nd);
1970
1971 if (IS_ERR(s))
1972 return PTR_ERR(s);
1973 err = 0;
1974 if (unlikely(!s)) {
1975 /* jumped */
1976 put_link(nd);
1977 } else {
1978 nd->stack[nd->depth - 1].name = name;
1979 name = s;
1980 continue;
1981 }
1982 }
1983 if (unlikely(!d_can_lookup(nd->path.dentry))) {
1984 if (nd->flags & LOOKUP_RCU) {
1985 if (unlazy_walk(nd, NULL, 0))
1986 return -ECHILD;
1987 }
1988 return -ENOTDIR;
1989 }
1990 }
1991}
1992
1993static const char *path_init(struct nameidata *nd, unsigned flags)
1994{
1995 int retval = 0;
1996 const char *s = nd->name->name;
1997
1998 nd->last_type = LAST_ROOT; /* if there are only slashes... */
1999 nd->flags = flags | LOOKUP_JUMPED | LOOKUP_PARENT;
2000 nd->depth = 0;
2001 if (flags & LOOKUP_ROOT) {
2002 struct dentry *root = nd->root.dentry;
2003 struct inode *inode = root->d_inode;
2004 if (*s) {
2005 if (!d_can_lookup(root))
2006 return ERR_PTR(-ENOTDIR);
2007 retval = inode_permission(inode, MAY_EXEC);
2008 if (retval)
2009 return ERR_PTR(retval);
2010 }
2011 nd->path = nd->root;
2012 nd->inode = inode;
2013 if (flags & LOOKUP_RCU) {
2014 rcu_read_lock();
2015 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
2016 nd->root_seq = nd->seq;
2017 nd->m_seq = read_seqbegin(&mount_lock);
2018 } else {
2019 path_get(&nd->path);
2020 }
2021 return s;
2022 }
2023
2024 nd->root.mnt = NULL;
2025 nd->path.mnt = NULL;
2026 nd->path.dentry = NULL;
2027
2028 nd->m_seq = read_seqbegin(&mount_lock);
2029 if (*s == '/') {
2030 if (flags & LOOKUP_RCU)
2031 rcu_read_lock();
2032 set_root(nd);
2033 if (likely(!nd_jump_root(nd)))
2034 return s;
2035 nd->root.mnt = NULL;
2036 rcu_read_unlock();
2037 return ERR_PTR(-ECHILD);
2038 } else if (nd->dfd == AT_FDCWD) {
2039 if (flags & LOOKUP_RCU) {
2040 struct fs_struct *fs = current->fs;
2041 unsigned seq;
2042
2043 rcu_read_lock();
2044
2045 do {
2046 seq = read_seqcount_begin(&fs->seq);
2047 nd->path = fs->pwd;
2048 nd->inode = nd->path.dentry->d_inode;
2049 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
2050 } while (read_seqcount_retry(&fs->seq, seq));
2051 } else {
2052 get_fs_pwd(current->fs, &nd->path);
2053 nd->inode = nd->path.dentry->d_inode;
2054 }
2055 return s;
2056 } else {
2057 /* Caller must check execute permissions on the starting path component */
2058 struct fd f = fdget_raw(nd->dfd);
2059 struct dentry *dentry;
2060
2061 if (!f.file)
2062 return ERR_PTR(-EBADF);
2063
2064 dentry = f.file->f_path.dentry;
2065
2066 if (*s) {
2067 if (!d_can_lookup(dentry)) {
2068 fdput(f);
2069 return ERR_PTR(-ENOTDIR);
2070 }
2071 }
2072
2073 nd->path = f.file->f_path;
2074 if (flags & LOOKUP_RCU) {
2075 rcu_read_lock();
2076 nd->inode = nd->path.dentry->d_inode;
2077 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
2078 } else {
2079 path_get(&nd->path);
2080 nd->inode = nd->path.dentry->d_inode;
2081 }
2082 fdput(f);
2083 return s;
2084 }
2085}
2086
2087static const char *trailing_symlink(struct nameidata *nd)
2088{
2089 const char *s;
2090 int error = may_follow_link(nd);
2091 if (unlikely(error))
2092 return ERR_PTR(error);
2093 nd->flags |= LOOKUP_PARENT;
2094 nd->stack[0].name = NULL;
2095 s = get_link(nd);
2096 return s ? s : "";
2097}
2098
2099static inline int lookup_last(struct nameidata *nd)
2100{
2101 if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
2102 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
2103
2104 nd->flags &= ~LOOKUP_PARENT;
2105 return walk_component(nd,
2106 nd->flags & LOOKUP_FOLLOW
2107 ? nd->depth
2108 ? WALK_PUT | WALK_GET
2109 : WALK_GET
2110 : 0);
2111}
2112
2113/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
2114static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path)
2115{
2116 const char *s = path_init(nd, flags);
2117 int err;
2118
2119 if (IS_ERR(s))
2120 return PTR_ERR(s);
2121 while (!(err = link_path_walk(s, nd))
2122 && ((err = lookup_last(nd)) > 0)) {
2123 s = trailing_symlink(nd);
2124 if (IS_ERR(s)) {
2125 err = PTR_ERR(s);
2126 break;
2127 }
2128 }
2129 if (!err)
2130 err = complete_walk(nd);
2131
2132 if (!err && nd->flags & LOOKUP_DIRECTORY)
2133 if (!d_can_lookup(nd->path.dentry))
2134 err = -ENOTDIR;
2135 if (!err) {
2136 *path = nd->path;
2137 nd->path.mnt = NULL;
2138 nd->path.dentry = NULL;
2139 }
2140 terminate_walk(nd);
2141 return err;
2142}
2143
2144static int filename_lookup(int dfd, struct filename *name, unsigned flags,
2145 struct path *path, struct path *root)
2146{
2147 int retval;
2148 struct nameidata nd;
2149 if (IS_ERR(name))
2150 return PTR_ERR(name);
2151 if (unlikely(root)) {
2152 nd.root = *root;
2153 flags |= LOOKUP_ROOT;
2154 }
2155 set_nameidata(&nd, dfd, name);
2156 retval = path_lookupat(&nd, flags | LOOKUP_RCU, path);
2157 if (unlikely(retval == -ECHILD))
2158 retval = path_lookupat(&nd, flags, path);
2159 if (unlikely(retval == -ESTALE))
2160 retval = path_lookupat(&nd, flags | LOOKUP_REVAL, path);
2161
2162 if (likely(!retval))
2163 audit_inode(name, path->dentry, flags & LOOKUP_PARENT);
2164 restore_nameidata();
2165 putname(name);
2166 return retval;
2167}
2168
2169/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
2170static int path_parentat(struct nameidata *nd, unsigned flags,
2171 struct path *parent)
2172{
2173 const char *s = path_init(nd, flags);
2174 int err;
2175 if (IS_ERR(s))
2176 return PTR_ERR(s);
2177 err = link_path_walk(s, nd);
2178 if (!err)
2179 err = complete_walk(nd);
2180 if (!err) {
2181 *parent = nd->path;
2182 nd->path.mnt = NULL;
2183 nd->path.dentry = NULL;
2184 }
2185 terminate_walk(nd);
2186 return err;
2187}
2188
2189static struct filename *filename_parentat(int dfd, struct filename *name,
2190 unsigned int flags, struct path *parent,
2191 struct qstr *last, int *type)
2192{
2193 int retval;
2194 struct nameidata nd;
2195
2196 if (IS_ERR(name))
2197 return name;
2198 set_nameidata(&nd, dfd, name);
2199 retval = path_parentat(&nd, flags | LOOKUP_RCU, parent);
2200 if (unlikely(retval == -ECHILD))
2201 retval = path_parentat(&nd, flags, parent);
2202 if (unlikely(retval == -ESTALE))
2203 retval = path_parentat(&nd, flags | LOOKUP_REVAL, parent);
2204 if (likely(!retval)) {
2205 *last = nd.last;
2206 *type = nd.last_type;
2207 audit_inode(name, parent->dentry, LOOKUP_PARENT);
2208 } else {
2209 putname(name);
2210 name = ERR_PTR(retval);
2211 }
2212 restore_nameidata();
2213 return name;
2214}
2215
2216/* does lookup, returns the object with parent locked */
2217struct dentry *kern_path_locked(const char *name, struct path *path)
2218{
2219 struct filename *filename;
2220 struct dentry *d;
2221 struct qstr last;
2222 int type;
2223
2224 filename = filename_parentat(AT_FDCWD, getname_kernel(name), 0, path,
2225 &last, &type);
2226 if (IS_ERR(filename))
2227 return ERR_CAST(filename);
2228 if (unlikely(type != LAST_NORM)) {
2229 path_put(path);
2230 putname(filename);
2231 return ERR_PTR(-EINVAL);
2232 }
2233 inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
2234 d = __lookup_hash(&last, path->dentry, 0);
2235 if (IS_ERR(d)) {
2236 inode_unlock(path->dentry->d_inode);
2237 path_put(path);
2238 }
2239 putname(filename);
2240 return d;
2241}
2242
2243int kern_path(const char *name, unsigned int flags, struct path *path)
2244{
2245 return filename_lookup(AT_FDCWD, getname_kernel(name),
2246 flags, path, NULL);
2247}
2248EXPORT_SYMBOL(kern_path);
2249
2250/**
2251 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
2252 * @dentry: pointer to dentry of the base directory
2253 * @mnt: pointer to vfs mount of the base directory
2254 * @name: pointer to file name
2255 * @flags: lookup flags
2256 * @path: pointer to struct path to fill
2257 */
2258int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
2259 const char *name, unsigned int flags,
2260 struct path *path)
2261{
2262 struct path root = {.mnt = mnt, .dentry = dentry};
2263 /* the first argument of filename_lookup() is ignored with root */
2264 return filename_lookup(AT_FDCWD, getname_kernel(name),
2265 flags , path, &root);
2266}
2267EXPORT_SYMBOL(vfs_path_lookup);
2268
2269/**
2270 * lookup_hash - lookup single pathname component on already hashed name
2271 * @name: name and hash to lookup
2272 * @base: base directory to lookup from
2273 *
2274 * The name must have been verified and hashed (see lookup_one_len()). Using
2275 * this after just full_name_hash() is unsafe.
2276 *
2277 * This function also doesn't check for search permission on base directory.
2278 *
2279 * Use lookup_one_len_unlocked() instead, unless you really know what you are
2280 * doing.
2281 *
2282 * Do not hold i_mutex; this helper takes i_mutex if necessary.
2283 */
2284struct dentry *lookup_hash(const struct qstr *name, struct dentry *base)
2285{
2286 struct dentry *ret;
2287
2288 ret = lookup_dcache(name, base, 0);
2289 if (!ret)
2290 ret = lookup_slow(name, base, 0);
2291
2292 return ret;
2293}
2294EXPORT_SYMBOL(lookup_hash);
2295
2296/**
2297 * lookup_one_len - filesystem helper to lookup single pathname component
2298 * @name: pathname component to lookup
2299 * @base: base directory to lookup from
2300 * @len: maximum length @len should be interpreted to
2301 *
2302 * Note that this routine is purely a helper for filesystem usage and should
2303 * not be called by generic code.
2304 *
2305 * The caller must hold base->i_mutex.
2306 */
2307struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
2308{
2309 struct qstr this;
2310 unsigned int c;
2311 int err;
2312
2313 WARN_ON_ONCE(!inode_is_locked(base->d_inode));
2314
2315 this.name = name;
2316 this.len = len;
2317 this.hash = full_name_hash(name, len);
2318 if (!len)
2319 return ERR_PTR(-EACCES);
2320
2321 if (unlikely(name[0] == '.')) {
2322 if (len < 2 || (len == 2 && name[1] == '.'))
2323 return ERR_PTR(-EACCES);
2324 }
2325
2326 while (len--) {
2327 c = *(const unsigned char *)name++;
2328 if (c == '/' || c == '\0')
2329 return ERR_PTR(-EACCES);
2330 }
2331 /*
2332 * See if the low-level filesystem might want
2333 * to use its own hash..
2334 */
2335 if (base->d_flags & DCACHE_OP_HASH) {
2336 int err = base->d_op->d_hash(base, &this);
2337 if (err < 0)
2338 return ERR_PTR(err);
2339 }
2340
2341 err = inode_permission(base->d_inode, MAY_EXEC);
2342 if (err)
2343 return ERR_PTR(err);
2344
2345 return __lookup_hash(&this, base, 0);
2346}
2347EXPORT_SYMBOL(lookup_one_len);
2348
2349/**
2350 * lookup_one_len_unlocked - filesystem helper to lookup single pathname component
2351 * @name: pathname component to lookup
2352 * @base: base directory to lookup from
2353 * @len: maximum length @len should be interpreted to
2354 *
2355 * Note that this routine is purely a helper for filesystem usage and should
2356 * not be called by generic code.
2357 *
2358 * Unlike lookup_one_len, it should be called without the parent
2359 * i_mutex held, and will take the i_mutex itself if necessary.
2360 */
2361struct dentry *lookup_one_len_unlocked(const char *name,
2362 struct dentry *base, int len)
2363{
2364 struct qstr this;
2365 unsigned int c;
2366 int err;
2367
2368 this.name = name;
2369 this.len = len;
2370 this.hash = full_name_hash(name, len);
2371 if (!len)
2372 return ERR_PTR(-EACCES);
2373
2374 if (unlikely(name[0] == '.')) {
2375 if (len < 2 || (len == 2 && name[1] == '.'))
2376 return ERR_PTR(-EACCES);
2377 }
2378
2379 while (len--) {
2380 c = *(const unsigned char *)name++;
2381 if (c == '/' || c == '\0')
2382 return ERR_PTR(-EACCES);
2383 }
2384 /*
2385 * See if the low-level filesystem might want
2386 * to use its own hash..
2387 */
2388 if (base->d_flags & DCACHE_OP_HASH) {
2389 int err = base->d_op->d_hash(base, &this);
2390 if (err < 0)
2391 return ERR_PTR(err);
2392 }
2393
2394 err = inode_permission(base->d_inode, MAY_EXEC);
2395 if (err)
2396 return ERR_PTR(err);
2397
2398 return lookup_hash(&this, base);
2399}
2400EXPORT_SYMBOL(lookup_one_len_unlocked);
2401
2402int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
2403 struct path *path, int *empty)
2404{
2405 return filename_lookup(dfd, getname_flags(name, flags, empty),
2406 flags, path, NULL);
2407}
2408EXPORT_SYMBOL(user_path_at_empty);
2409
2410/*
2411 * NB: most callers don't do anything directly with the reference to the
2412 * to struct filename, but the nd->last pointer points into the name string
2413 * allocated by getname. So we must hold the reference to it until all
2414 * path-walking is complete.
2415 */
2416static inline struct filename *
2417user_path_parent(int dfd, const char __user *path,
2418 struct path *parent,
2419 struct qstr *last,
2420 int *type,
2421 unsigned int flags)
2422{
2423 /* only LOOKUP_REVAL is allowed in extra flags */
2424 return filename_parentat(dfd, getname(path), flags & LOOKUP_REVAL,
2425 parent, last, type);
2426}
2427
2428/**
2429 * mountpoint_last - look up last component for umount
2430 * @nd: pathwalk nameidata - currently pointing at parent directory of "last"
2431 * @path: pointer to container for result
2432 *
2433 * This is a special lookup_last function just for umount. In this case, we
2434 * need to resolve the path without doing any revalidation.
2435 *
2436 * The nameidata should be the result of doing a LOOKUP_PARENT pathwalk. Since
2437 * mountpoints are always pinned in the dcache, their ancestors are too. Thus,
2438 * in almost all cases, this lookup will be served out of the dcache. The only
2439 * cases where it won't are if nd->last refers to a symlink or the path is
2440 * bogus and it doesn't exist.
2441 *
2442 * Returns:
2443 * -error: if there was an error during lookup. This includes -ENOENT if the
2444 * lookup found a negative dentry. The nd->path reference will also be
2445 * put in this case.
2446 *
2447 * 0: if we successfully resolved nd->path and found it to not to be a
2448 * symlink that needs to be followed. "path" will also be populated.
2449 * The nd->path reference will also be put.
2450 *
2451 * 1: if we successfully resolved nd->last and found it to be a symlink
2452 * that needs to be followed. "path" will be populated with the path
2453 * to the link, and nd->path will *not* be put.
2454 */
2455static int
2456mountpoint_last(struct nameidata *nd, struct path *path)
2457{
2458 int error = 0;
2459 struct dentry *dentry;
2460 struct dentry *dir = nd->path.dentry;
2461
2462 /* If we're in rcuwalk, drop out of it to handle last component */
2463 if (nd->flags & LOOKUP_RCU) {
2464 if (unlazy_walk(nd, NULL, 0))
2465 return -ECHILD;
2466 }
2467
2468 nd->flags &= ~LOOKUP_PARENT;
2469
2470 if (unlikely(nd->last_type != LAST_NORM)) {
2471 error = handle_dots(nd, nd->last_type);
2472 if (error)
2473 return error;
2474 dentry = dget(nd->path.dentry);
2475 } else {
2476 dentry = d_lookup(dir, &nd->last);
2477 if (!dentry) {
2478 /*
2479 * No cached dentry. Mounted dentries are pinned in the
2480 * cache, so that means that this dentry is probably
2481 * a symlink or the path doesn't actually point
2482 * to a mounted dentry.
2483 */
2484 dentry = lookup_slow(&nd->last, dir,
2485 nd->flags | LOOKUP_NO_REVAL);
2486 if (IS_ERR(dentry))
2487 return PTR_ERR(dentry);
2488 }
2489 }
2490 if (d_is_negative(dentry)) {
2491 dput(dentry);
2492 return -ENOENT;
2493 }
2494 if (nd->depth)
2495 put_link(nd);
2496 path->dentry = dentry;
2497 path->mnt = nd->path.mnt;
2498 error = should_follow_link(nd, path, nd->flags & LOOKUP_FOLLOW,
2499 d_backing_inode(dentry), 0);
2500 if (unlikely(error))
2501 return error;
2502 mntget(path->mnt);
2503 follow_mount(path);
2504 return 0;
2505}
2506
2507/**
2508 * path_mountpoint - look up a path to be umounted
2509 * @nd: lookup context
2510 * @flags: lookup flags
2511 * @path: pointer to container for result
2512 *
2513 * Look up the given name, but don't attempt to revalidate the last component.
2514 * Returns 0 and "path" will be valid on success; Returns error otherwise.
2515 */
2516static int
2517path_mountpoint(struct nameidata *nd, unsigned flags, struct path *path)
2518{
2519 const char *s = path_init(nd, flags);
2520 int err;
2521 if (IS_ERR(s))
2522 return PTR_ERR(s);
2523 while (!(err = link_path_walk(s, nd)) &&
2524 (err = mountpoint_last(nd, path)) > 0) {
2525 s = trailing_symlink(nd);
2526 if (IS_ERR(s)) {
2527 err = PTR_ERR(s);
2528 break;
2529 }
2530 }
2531 terminate_walk(nd);
2532 return err;
2533}
2534
2535static int
2536filename_mountpoint(int dfd, struct filename *name, struct path *path,
2537 unsigned int flags)
2538{
2539 struct nameidata nd;
2540 int error;
2541 if (IS_ERR(name))
2542 return PTR_ERR(name);
2543 set_nameidata(&nd, dfd, name);
2544 error = path_mountpoint(&nd, flags | LOOKUP_RCU, path);
2545 if (unlikely(error == -ECHILD))
2546 error = path_mountpoint(&nd, flags, path);
2547 if (unlikely(error == -ESTALE))
2548 error = path_mountpoint(&nd, flags | LOOKUP_REVAL, path);
2549 if (likely(!error))
2550 audit_inode(name, path->dentry, 0);
2551 restore_nameidata();
2552 putname(name);
2553 return error;
2554}
2555
2556/**
2557 * user_path_mountpoint_at - lookup a path from userland in order to umount it
2558 * @dfd: directory file descriptor
2559 * @name: pathname from userland
2560 * @flags: lookup flags
2561 * @path: pointer to container to hold result
2562 *
2563 * A umount is a special case for path walking. We're not actually interested
2564 * in the inode in this situation, and ESTALE errors can be a problem. We
2565 * simply want track down the dentry and vfsmount attached at the mountpoint
2566 * and avoid revalidating the last component.
2567 *
2568 * Returns 0 and populates "path" on success.
2569 */
2570int
2571user_path_mountpoint_at(int dfd, const char __user *name, unsigned int flags,
2572 struct path *path)
2573{
2574 return filename_mountpoint(dfd, getname(name), path, flags);
2575}
2576
2577int
2578kern_path_mountpoint(int dfd, const char *name, struct path *path,
2579 unsigned int flags)
2580{
2581 return filename_mountpoint(dfd, getname_kernel(name), path, flags);
2582}
2583EXPORT_SYMBOL(kern_path_mountpoint);
2584
2585int __check_sticky(struct inode *dir, struct inode *inode)
2586{
2587 kuid_t fsuid = current_fsuid();
2588
2589 if (uid_eq(inode->i_uid, fsuid))
2590 return 0;
2591 if (uid_eq(dir->i_uid, fsuid))
2592 return 0;
2593 return !capable_wrt_inode_uidgid(inode, CAP_FOWNER);
2594}
2595EXPORT_SYMBOL(__check_sticky);
2596
2597/*
2598 * Check whether we can remove a link victim from directory dir, check
2599 * whether the type of victim is right.
2600 * 1. We can't do it if dir is read-only (done in permission())
2601 * 2. We should have write and exec permissions on dir
2602 * 3. We can't remove anything from append-only dir
2603 * 4. We can't do anything with immutable dir (done in permission())
2604 * 5. If the sticky bit on dir is set we should either
2605 * a. be owner of dir, or
2606 * b. be owner of victim, or
2607 * c. have CAP_FOWNER capability
2608 * 6. If the victim is append-only or immutable we can't do antyhing with
2609 * links pointing to it.
2610 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
2611 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
2612 * 9. We can't remove a root or mountpoint.
2613 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
2614 * nfs_async_unlink().
2615 */
2616static int may_delete(struct inode *dir, struct dentry *victim, bool isdir)
2617{
2618 struct inode *inode = d_backing_inode(victim);
2619 int error;
2620
2621 if (d_is_negative(victim))
2622 return -ENOENT;
2623 BUG_ON(!inode);
2624
2625 BUG_ON(victim->d_parent->d_inode != dir);
2626 audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE);
2627
2628 error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
2629 if (error)
2630 return error;
2631 if (IS_APPEND(dir))
2632 return -EPERM;
2633
2634 if (check_sticky(dir, inode) || IS_APPEND(inode) ||
2635 IS_IMMUTABLE(inode) || IS_SWAPFILE(inode))
2636 return -EPERM;
2637 if (isdir) {
2638 if (!d_is_dir(victim))
2639 return -ENOTDIR;
2640 if (IS_ROOT(victim))
2641 return -EBUSY;
2642 } else if (d_is_dir(victim))
2643 return -EISDIR;
2644 if (IS_DEADDIR(dir))
2645 return -ENOENT;
2646 if (victim->d_flags & DCACHE_NFSFS_RENAMED)
2647 return -EBUSY;
2648 return 0;
2649}
2650
2651/* Check whether we can create an object with dentry child in directory
2652 * dir.
2653 * 1. We can't do it if child already exists (open has special treatment for
2654 * this case, but since we are inlined it's OK)
2655 * 2. We can't do it if dir is read-only (done in permission())
2656 * 3. We should have write and exec permissions on dir
2657 * 4. We can't do it if dir is immutable (done in permission())
2658 */
2659static inline int may_create(struct inode *dir, struct dentry *child)
2660{
2661 audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE);
2662 if (child->d_inode)
2663 return -EEXIST;
2664 if (IS_DEADDIR(dir))
2665 return -ENOENT;
2666 return inode_permission(dir, MAY_WRITE | MAY_EXEC);
2667}
2668
2669/*
2670 * p1 and p2 should be directories on the same fs.
2671 */
2672struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
2673{
2674 struct dentry *p;
2675
2676 if (p1 == p2) {
2677 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
2678 return NULL;
2679 }
2680
2681 mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
2682
2683 p = d_ancestor(p2, p1);
2684 if (p) {
2685 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT);
2686 inode_lock_nested(p1->d_inode, I_MUTEX_CHILD);
2687 return p;
2688 }
2689
2690 p = d_ancestor(p1, p2);
2691 if (p) {
2692 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
2693 inode_lock_nested(p2->d_inode, I_MUTEX_CHILD);
2694 return p;
2695 }
2696
2697 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
2698 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT2);
2699 return NULL;
2700}
2701EXPORT_SYMBOL(lock_rename);
2702
2703void unlock_rename(struct dentry *p1, struct dentry *p2)
2704{
2705 inode_unlock(p1->d_inode);
2706 if (p1 != p2) {
2707 inode_unlock(p2->d_inode);
2708 mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
2709 }
2710}
2711EXPORT_SYMBOL(unlock_rename);
2712
2713int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
2714 bool want_excl)
2715{
2716 int error = may_create(dir, dentry);
2717 if (error)
2718 return error;
2719
2720 if (!dir->i_op->create)
2721 return -EACCES; /* shouldn't it be ENOSYS? */
2722 mode &= S_IALLUGO;
2723 mode |= S_IFREG;
2724 error = security_inode_create(dir, dentry, mode);
2725 if (error)
2726 return error;
2727 error = dir->i_op->create(dir, dentry, mode, want_excl);
2728 if (!error)
2729 fsnotify_create(dir, dentry);
2730 return error;
2731}
2732EXPORT_SYMBOL(vfs_create);
2733
2734static int may_open(struct path *path, int acc_mode, int flag)
2735{
2736 struct dentry *dentry = path->dentry;
2737 struct inode *inode = dentry->d_inode;
2738 int error;
2739
2740 if (!inode)
2741 return -ENOENT;
2742
2743 switch (inode->i_mode & S_IFMT) {
2744 case S_IFLNK:
2745 return -ELOOP;
2746 case S_IFDIR:
2747 if (acc_mode & MAY_WRITE)
2748 return -EISDIR;
2749 break;
2750 case S_IFBLK:
2751 case S_IFCHR:
2752 if (path->mnt->mnt_flags & MNT_NODEV)
2753 return -EACCES;
2754 /*FALLTHRU*/
2755 case S_IFIFO:
2756 case S_IFSOCK:
2757 flag &= ~O_TRUNC;
2758 break;
2759 }
2760
2761 error = inode_permission(inode, MAY_OPEN | acc_mode);
2762 if (error)
2763 return error;
2764
2765 /*
2766 * An append-only file must be opened in append mode for writing.
2767 */
2768 if (IS_APPEND(inode)) {
2769 if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
2770 return -EPERM;
2771 if (flag & O_TRUNC)
2772 return -EPERM;
2773 }
2774
2775 /* O_NOATIME can only be set by the owner or superuser */
2776 if (flag & O_NOATIME && !inode_owner_or_capable(inode))
2777 return -EPERM;
2778
2779 return 0;
2780}
2781
2782static int handle_truncate(struct file *filp)
2783{
2784 struct path *path = &filp->f_path;
2785 struct inode *inode = path->dentry->d_inode;
2786 int error = get_write_access(inode);
2787 if (error)
2788 return error;
2789 /*
2790 * Refuse to truncate files with mandatory locks held on them.
2791 */
2792 error = locks_verify_locked(filp);
2793 if (!error)
2794 error = security_path_truncate(path);
2795 if (!error) {
2796 error = do_truncate(path->dentry, 0,
2797 ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
2798 filp);
2799 }
2800 put_write_access(inode);
2801 return error;
2802}
2803
2804static inline int open_to_namei_flags(int flag)
2805{
2806 if ((flag & O_ACCMODE) == 3)
2807 flag--;
2808 return flag;
2809}
2810
2811static int may_o_create(struct path *dir, struct dentry *dentry, umode_t mode)
2812{
2813 int error = security_path_mknod(dir, dentry, mode, 0);
2814 if (error)
2815 return error;
2816
2817 error = inode_permission(dir->dentry->d_inode, MAY_WRITE | MAY_EXEC);
2818 if (error)
2819 return error;
2820
2821 return security_inode_create(dir->dentry->d_inode, dentry, mode);
2822}
2823
2824/*
2825 * Attempt to atomically look up, create and open a file from a negative
2826 * dentry.
2827 *
2828 * Returns 0 if successful. The file will have been created and attached to
2829 * @file by the filesystem calling finish_open().
2830 *
2831 * Returns 1 if the file was looked up only or didn't need creating. The
2832 * caller will need to perform the open themselves. @path will have been
2833 * updated to point to the new dentry. This may be negative.
2834 *
2835 * Returns an error code otherwise.
2836 */
2837static int atomic_open(struct nameidata *nd, struct dentry *dentry,
2838 struct path *path, struct file *file,
2839 const struct open_flags *op,
2840 bool got_write, bool need_lookup,
2841 int *opened)
2842{
2843 struct inode *dir = nd->path.dentry->d_inode;
2844 unsigned open_flag = open_to_namei_flags(op->open_flag);
2845 umode_t mode;
2846 int error;
2847 int acc_mode;
2848 int create_error = 0;
2849 struct dentry *const DENTRY_NOT_SET = (void *) -1UL;
2850 bool excl;
2851
2852 BUG_ON(dentry->d_inode);
2853
2854 /* Don't create child dentry for a dead directory. */
2855 if (unlikely(IS_DEADDIR(dir))) {
2856 error = -ENOENT;
2857 goto out;
2858 }
2859
2860 mode = op->mode;
2861 if ((open_flag & O_CREAT) && !IS_POSIXACL(dir))
2862 mode &= ~current_umask();
2863
2864 excl = (open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT);
2865 if (excl)
2866 open_flag &= ~O_TRUNC;
2867
2868 /*
2869 * Checking write permission is tricky, bacuse we don't know if we are
2870 * going to actually need it: O_CREAT opens should work as long as the
2871 * file exists. But checking existence breaks atomicity. The trick is
2872 * to check access and if not granted clear O_CREAT from the flags.
2873 *
2874 * Another problem is returing the "right" error value (e.g. for an
2875 * O_EXCL open we want to return EEXIST not EROFS).
2876 */
2877 if (((open_flag & (O_CREAT | O_TRUNC)) ||
2878 (open_flag & O_ACCMODE) != O_RDONLY) && unlikely(!got_write)) {
2879 if (!(open_flag & O_CREAT)) {
2880 /*
2881 * No O_CREATE -> atomicity not a requirement -> fall
2882 * back to lookup + open
2883 */
2884 goto no_open;
2885 } else if (open_flag & (O_EXCL | O_TRUNC)) {
2886 /* Fall back and fail with the right error */
2887 create_error = -EROFS;
2888 goto no_open;
2889 } else {
2890 /* No side effects, safe to clear O_CREAT */
2891 create_error = -EROFS;
2892 open_flag &= ~O_CREAT;
2893 }
2894 }
2895
2896 if (open_flag & O_CREAT) {
2897 error = may_o_create(&nd->path, dentry, mode);
2898 if (error) {
2899 create_error = error;
2900 if (open_flag & O_EXCL)
2901 goto no_open;
2902 open_flag &= ~O_CREAT;
2903 }
2904 }
2905
2906 if (nd->flags & LOOKUP_DIRECTORY)
2907 open_flag |= O_DIRECTORY;
2908
2909 file->f_path.dentry = DENTRY_NOT_SET;
2910 file->f_path.mnt = nd->path.mnt;
2911 error = dir->i_op->atomic_open(dir, dentry, file, open_flag, mode,
2912 opened);
2913 if (error < 0) {
2914 if (create_error && error == -ENOENT)
2915 error = create_error;
2916 goto out;
2917 }
2918
2919 if (error) { /* returned 1, that is */
2920 if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) {
2921 error = -EIO;
2922 goto out;
2923 }
2924 if (file->f_path.dentry) {
2925 dput(dentry);
2926 dentry = file->f_path.dentry;
2927 }
2928 if (*opened & FILE_CREATED)
2929 fsnotify_create(dir, dentry);
2930 if (!dentry->d_inode) {
2931 WARN_ON(*opened & FILE_CREATED);
2932 if (create_error) {
2933 error = create_error;
2934 goto out;
2935 }
2936 } else {
2937 if (excl && !(*opened & FILE_CREATED)) {
2938 error = -EEXIST;
2939 goto out;
2940 }
2941 }
2942 goto looked_up;
2943 }
2944
2945 /*
2946 * We didn't have the inode before the open, so check open permission
2947 * here.
2948 */
2949 acc_mode = op->acc_mode;
2950 if (*opened & FILE_CREATED) {
2951 WARN_ON(!(open_flag & O_CREAT));
2952 fsnotify_create(dir, dentry);
2953 acc_mode = 0;
2954 }
2955 error = may_open(&file->f_path, acc_mode, open_flag);
2956 if (error)
2957 fput(file);
2958
2959out:
2960 dput(dentry);
2961 return error;
2962
2963no_open:
2964 if (need_lookup) {
2965 dentry = lookup_real(dir, dentry, nd->flags);
2966 if (IS_ERR(dentry))
2967 return PTR_ERR(dentry);
2968 }
2969 if (create_error && !dentry->d_inode) {
2970 error = create_error;
2971 goto out;
2972 }
2973looked_up:
2974 path->dentry = dentry;
2975 path->mnt = nd->path.mnt;
2976 return 1;
2977}
2978
2979/*
2980 * Look up and maybe create and open the last component.
2981 *
2982 * Must be called with i_mutex held on parent.
2983 *
2984 * Returns 0 if the file was successfully atomically created (if necessary) and
2985 * opened. In this case the file will be returned attached to @file.
2986 *
2987 * Returns 1 if the file was not completely opened at this time, though lookups
2988 * and creations will have been performed and the dentry returned in @path will
2989 * be positive upon return if O_CREAT was specified. If O_CREAT wasn't
2990 * specified then a negative dentry may be returned.
2991 *
2992 * An error code is returned otherwise.
2993 *
2994 * FILE_CREATE will be set in @*opened if the dentry was created and will be
2995 * cleared otherwise prior to returning.
2996 */
2997static int lookup_open(struct nameidata *nd, struct path *path,
2998 struct file *file,
2999 const struct open_flags *op,
3000 bool got_write, int *opened)
3001{
3002 struct dentry *dir = nd->path.dentry;
3003 struct inode *dir_inode = dir->d_inode;
3004 struct dentry *dentry;
3005 int error;
3006 bool need_lookup = false;
3007
3008 *opened &= ~FILE_CREATED;
3009 dentry = lookup_dcache(&nd->last, dir, nd->flags);
3010 if (IS_ERR(dentry))
3011 return PTR_ERR(dentry);
3012
3013 if (!dentry) {
3014 dentry = d_alloc(dir, &nd->last);
3015 if (unlikely(!dentry))
3016 return -ENOMEM;
3017 need_lookup = true;
3018 } else if (dentry->d_inode) {
3019 /* Cached positive dentry: will open in f_op->open */
3020 goto out_no_open;
3021 }
3022
3023 if ((nd->flags & LOOKUP_OPEN) && dir_inode->i_op->atomic_open) {
3024 return atomic_open(nd, dentry, path, file, op, got_write,
3025 need_lookup, opened);
3026 }
3027
3028 if (need_lookup) {
3029 BUG_ON(dentry->d_inode);
3030
3031 dentry = lookup_real(dir_inode, dentry, nd->flags);
3032 if (IS_ERR(dentry))
3033 return PTR_ERR(dentry);
3034 }
3035
3036 /* Negative dentry, just create the file */
3037 if (!dentry->d_inode && (op->open_flag & O_CREAT)) {
3038 umode_t mode = op->mode;
3039 if (!IS_POSIXACL(dir->d_inode))
3040 mode &= ~current_umask();
3041 /*
3042 * This write is needed to ensure that a
3043 * rw->ro transition does not occur between
3044 * the time when the file is created and when
3045 * a permanent write count is taken through
3046 * the 'struct file' in finish_open().
3047 */
3048 if (!got_write) {
3049 error = -EROFS;
3050 goto out_dput;
3051 }
3052 *opened |= FILE_CREATED;
3053 error = security_path_mknod(&nd->path, dentry, mode, 0);
3054 if (error)
3055 goto out_dput;
3056 error = vfs_create(dir->d_inode, dentry, mode,
3057 nd->flags & LOOKUP_EXCL);
3058 if (error)
3059 goto out_dput;
3060 }
3061out_no_open:
3062 path->dentry = dentry;
3063 path->mnt = nd->path.mnt;
3064 return 1;
3065
3066out_dput:
3067 dput(dentry);
3068 return error;
3069}
3070
3071/*
3072 * Handle the last step of open()
3073 */
3074static int do_last(struct nameidata *nd,
3075 struct file *file, const struct open_flags *op,
3076 int *opened)
3077{
3078 struct dentry *dir = nd->path.dentry;
3079 int open_flag = op->open_flag;
3080 bool will_truncate = (open_flag & O_TRUNC) != 0;
3081 bool got_write = false;
3082 int acc_mode = op->acc_mode;
3083 unsigned seq;
3084 struct inode *inode;
3085 struct path save_parent = { .dentry = NULL, .mnt = NULL };
3086 struct path path;
3087 bool retried = false;
3088 int error;
3089
3090 nd->flags &= ~LOOKUP_PARENT;
3091 nd->flags |= op->intent;
3092
3093 if (nd->last_type != LAST_NORM) {
3094 error = handle_dots(nd, nd->last_type);
3095 if (unlikely(error))
3096 return error;
3097 goto finish_open;
3098 }
3099
3100 if (!(open_flag & O_CREAT)) {
3101 if (nd->last.name[nd->last.len])
3102 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
3103 /* we _can_ be in RCU mode here */
3104 error = lookup_fast(nd, &path, &inode, &seq);
3105 if (likely(error > 0))
3106 goto finish_lookup;
3107
3108 if (error < 0)
3109 return error;
3110
3111 BUG_ON(nd->inode != dir->d_inode);
3112 BUG_ON(nd->flags & LOOKUP_RCU);
3113 } else {
3114 /* create side of things */
3115 /*
3116 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED
3117 * has been cleared when we got to the last component we are
3118 * about to look up
3119 */
3120 error = complete_walk(nd);
3121 if (error)
3122 return error;
3123
3124 audit_inode(nd->name, dir, LOOKUP_PARENT);
3125 /* trailing slashes? */
3126 if (unlikely(nd->last.name[nd->last.len]))
3127 return -EISDIR;
3128 }
3129
3130retry_lookup:
3131 if (op->open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
3132 error = mnt_want_write(nd->path.mnt);
3133 if (!error)
3134 got_write = true;
3135 /*
3136 * do _not_ fail yet - we might not need that or fail with
3137 * a different error; let lookup_open() decide; we'll be
3138 * dropping this one anyway.
3139 */
3140 }
3141 inode_lock(dir->d_inode);
3142 error = lookup_open(nd, &path, file, op, got_write, opened);
3143 inode_unlock(dir->d_inode);
3144
3145 if (error <= 0) {
3146 if (error)
3147 goto out;
3148
3149 if ((*opened & FILE_CREATED) ||
3150 !S_ISREG(file_inode(file)->i_mode))
3151 will_truncate = false;
3152
3153 audit_inode(nd->name, file->f_path.dentry, 0);
3154 goto opened;
3155 }
3156
3157 if (*opened & FILE_CREATED) {
3158 /* Don't check for write permission, don't truncate */
3159 open_flag &= ~O_TRUNC;
3160 will_truncate = false;
3161 acc_mode = 0;
3162 path_to_nameidata(&path, nd);
3163 goto finish_open_created;
3164 }
3165
3166 /*
3167 * If atomic_open() acquired write access it is dropped now due to
3168 * possible mount and symlink following (this might be optimized away if
3169 * necessary...)
3170 */
3171 if (got_write) {
3172 mnt_drop_write(nd->path.mnt);
3173 got_write = false;
3174 }
3175
3176 if (unlikely(d_is_negative(path.dentry))) {
3177 path_to_nameidata(&path, nd);
3178 return -ENOENT;
3179 }
3180
3181 /*
3182 * create/update audit record if it already exists.
3183 */
3184 audit_inode(nd->name, path.dentry, 0);
3185
3186 if (unlikely((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT))) {
3187 path_to_nameidata(&path, nd);
3188 return -EEXIST;
3189 }
3190
3191 error = follow_managed(&path, nd);
3192 if (unlikely(error < 0))
3193 return error;
3194
3195 seq = 0; /* out of RCU mode, so the value doesn't matter */
3196 inode = d_backing_inode(path.dentry);
3197finish_lookup:
3198 if (nd->depth)
3199 put_link(nd);
3200 error = should_follow_link(nd, &path, nd->flags & LOOKUP_FOLLOW,
3201 inode, seq);
3202 if (unlikely(error))
3203 return error;
3204
3205 if ((nd->flags & LOOKUP_RCU) || nd->path.mnt != path.mnt) {
3206 path_to_nameidata(&path, nd);
3207 } else {
3208 save_parent.dentry = nd->path.dentry;
3209 save_parent.mnt = mntget(path.mnt);
3210 nd->path.dentry = path.dentry;
3211
3212 }
3213 nd->inode = inode;
3214 nd->seq = seq;
3215 /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
3216finish_open:
3217 error = complete_walk(nd);
3218 if (error) {
3219 path_put(&save_parent);
3220 return error;
3221 }
3222 audit_inode(nd->name, nd->path.dentry, 0);
3223 if (unlikely(d_is_symlink(nd->path.dentry)) && !(open_flag & O_PATH)) {
3224 error = -ELOOP;
3225 goto out;
3226 }
3227 error = -EISDIR;
3228 if ((open_flag & O_CREAT) && d_is_dir(nd->path.dentry))
3229 goto out;
3230 error = -ENOTDIR;
3231 if ((nd->flags & LOOKUP_DIRECTORY) && !d_can_lookup(nd->path.dentry))
3232 goto out;
3233 if (!d_is_reg(nd->path.dentry))
3234 will_truncate = false;
3235
3236 if (will_truncate) {
3237 error = mnt_want_write(nd->path.mnt);
3238 if (error)
3239 goto out;
3240 got_write = true;
3241 }
3242finish_open_created:
3243 if (likely(!(open_flag & O_PATH))) {
3244 error = may_open(&nd->path, acc_mode, open_flag);
3245 if (error)
3246 goto out;
3247 }
3248 BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */
3249 error = vfs_open(&nd->path, file, current_cred());
3250 if (!error) {
3251 *opened |= FILE_OPENED;
3252 } else {
3253 if (error == -EOPENSTALE)
3254 goto stale_open;
3255 goto out;
3256 }
3257opened:
3258 error = open_check_o_direct(file);
3259 if (error)
3260 goto exit_fput;
3261 error = ima_file_check(file, op->acc_mode, *opened);
3262 if (error)
3263 goto exit_fput;
3264
3265 if (will_truncate) {
3266 error = handle_truncate(file);
3267 if (error)
3268 goto exit_fput;
3269 }
3270out:
3271 if (unlikely(error > 0)) {
3272 WARN_ON(1);
3273 error = -EINVAL;
3274 }
3275 if (got_write)
3276 mnt_drop_write(nd->path.mnt);
3277 path_put(&save_parent);
3278 return error;
3279
3280exit_fput:
3281 fput(file);
3282 goto out;
3283
3284stale_open:
3285 /* If no saved parent or already retried then can't retry */
3286 if (!save_parent.dentry || retried)
3287 goto out;
3288
3289 BUG_ON(save_parent.dentry != dir);
3290 path_put(&nd->path);
3291 nd->path = save_parent;
3292 nd->inode = dir->d_inode;
3293 save_parent.mnt = NULL;
3294 save_parent.dentry = NULL;
3295 if (got_write) {
3296 mnt_drop_write(nd->path.mnt);
3297 got_write = false;
3298 }
3299 retried = true;
3300 goto retry_lookup;
3301}
3302
3303static int do_tmpfile(struct nameidata *nd, unsigned flags,
3304 const struct open_flags *op,
3305 struct file *file, int *opened)
3306{
3307 static const struct qstr name = QSTR_INIT("/", 1);
3308 struct dentry *child;
3309 struct inode *dir;
3310 struct path path;
3311 int error = path_lookupat(nd, flags | LOOKUP_DIRECTORY, &path);
3312 if (unlikely(error))
3313 return error;
3314 error = mnt_want_write(path.mnt);
3315 if (unlikely(error))
3316 goto out;
3317 dir = path.dentry->d_inode;
3318 /* we want directory to be writable */
3319 error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
3320 if (error)
3321 goto out2;
3322 if (!dir->i_op->tmpfile) {
3323 error = -EOPNOTSUPP;
3324 goto out2;
3325 }
3326 child = d_alloc(path.dentry, &name);
3327 if (unlikely(!child)) {
3328 error = -ENOMEM;
3329 goto out2;
3330 }
3331 dput(path.dentry);
3332 path.dentry = child;
3333 error = dir->i_op->tmpfile(dir, child, op->mode);
3334 if (error)
3335 goto out2;
3336 audit_inode(nd->name, child, 0);
3337 /* Don't check for other permissions, the inode was just created */
3338 error = may_open(&path, 0, op->open_flag);
3339 if (error)
3340 goto out2;
3341 file->f_path.mnt = path.mnt;
3342 error = finish_open(file, child, NULL, opened);
3343 if (error)
3344 goto out2;
3345 error = open_check_o_direct(file);
3346 if (error) {
3347 fput(file);
3348 } else if (!(op->open_flag & O_EXCL)) {
3349 struct inode *inode = file_inode(file);
3350 spin_lock(&inode->i_lock);
3351 inode->i_state |= I_LINKABLE;
3352 spin_unlock(&inode->i_lock);
3353 }
3354out2:
3355 mnt_drop_write(path.mnt);
3356out:
3357 path_put(&path);
3358 return error;
3359}
3360
3361static struct file *path_openat(struct nameidata *nd,
3362 const struct open_flags *op, unsigned flags)
3363{
3364 const char *s;
3365 struct file *file;
3366 int opened = 0;
3367 int error;
3368
3369 file = get_empty_filp();
3370 if (IS_ERR(file))
3371 return file;
3372
3373 file->f_flags = op->open_flag;
3374
3375 if (unlikely(file->f_flags & __O_TMPFILE)) {
3376 error = do_tmpfile(nd, flags, op, file, &opened);
3377 goto out2;
3378 }
3379
3380 s = path_init(nd, flags);
3381 if (IS_ERR(s)) {
3382 put_filp(file);
3383 return ERR_CAST(s);
3384 }
3385 while (!(error = link_path_walk(s, nd)) &&
3386 (error = do_last(nd, file, op, &opened)) > 0) {
3387 nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
3388 s = trailing_symlink(nd);
3389 if (IS_ERR(s)) {
3390 error = PTR_ERR(s);
3391 break;
3392 }
3393 }
3394 terminate_walk(nd);
3395out2:
3396 if (!(opened & FILE_OPENED)) {
3397 BUG_ON(!error);
3398 put_filp(file);
3399 }
3400 if (unlikely(error)) {
3401 if (error == -EOPENSTALE) {
3402 if (flags & LOOKUP_RCU)
3403 error = -ECHILD;
3404 else
3405 error = -ESTALE;
3406 }
3407 file = ERR_PTR(error);
3408 }
3409 return file;
3410}
3411
3412struct file *do_filp_open(int dfd, struct filename *pathname,
3413 const struct open_flags *op)
3414{
3415 struct nameidata nd;
3416 int flags = op->lookup_flags;
3417 struct file *filp;
3418
3419 set_nameidata(&nd, dfd, pathname);
3420 filp = path_openat(&nd, op, flags | LOOKUP_RCU);
3421 if (unlikely(filp == ERR_PTR(-ECHILD)))
3422 filp = path_openat(&nd, op, flags);
3423 if (unlikely(filp == ERR_PTR(-ESTALE)))
3424 filp = path_openat(&nd, op, flags | LOOKUP_REVAL);
3425 restore_nameidata();
3426 return filp;
3427}
3428
3429struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
3430 const char *name, const struct open_flags *op)
3431{
3432 struct nameidata nd;
3433 struct file *file;
3434 struct filename *filename;
3435 int flags = op->lookup_flags | LOOKUP_ROOT;
3436
3437 nd.root.mnt = mnt;
3438 nd.root.dentry = dentry;
3439
3440 if (d_is_symlink(dentry) && op->intent & LOOKUP_OPEN)
3441 return ERR_PTR(-ELOOP);
3442
3443 filename = getname_kernel(name);
3444 if (IS_ERR(filename))
3445 return ERR_CAST(filename);
3446
3447 set_nameidata(&nd, -1, filename);
3448 file = path_openat(&nd, op, flags | LOOKUP_RCU);
3449 if (unlikely(file == ERR_PTR(-ECHILD)))
3450 file = path_openat(&nd, op, flags);
3451 if (unlikely(file == ERR_PTR(-ESTALE)))
3452 file = path_openat(&nd, op, flags | LOOKUP_REVAL);
3453 restore_nameidata();
3454 putname(filename);
3455 return file;
3456}
3457
3458static struct dentry *filename_create(int dfd, struct filename *name,
3459 struct path *path, unsigned int lookup_flags)
3460{
3461 struct dentry *dentry = ERR_PTR(-EEXIST);
3462 struct qstr last;
3463 int type;
3464 int err2;
3465 int error;
3466 bool is_dir = (lookup_flags & LOOKUP_DIRECTORY);
3467
3468 /*
3469 * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any
3470 * other flags passed in are ignored!
3471 */
3472 lookup_flags &= LOOKUP_REVAL;
3473
3474 name = filename_parentat(dfd, name, lookup_flags, path, &last, &type);
3475 if (IS_ERR(name))
3476 return ERR_CAST(name);
3477
3478 /*
3479 * Yucky last component or no last component at all?
3480 * (foo/., foo/.., /////)
3481 */
3482 if (unlikely(type != LAST_NORM))
3483 goto out;
3484
3485 /* don't fail immediately if it's r/o, at least try to report other errors */
3486 err2 = mnt_want_write(path->mnt);
3487 /*
3488 * Do the final lookup.
3489 */
3490 lookup_flags |= LOOKUP_CREATE | LOOKUP_EXCL;
3491 inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
3492 dentry = __lookup_hash(&last, path->dentry, lookup_flags);
3493 if (IS_ERR(dentry))
3494 goto unlock;
3495
3496 error = -EEXIST;
3497 if (d_is_positive(dentry))
3498 goto fail;
3499
3500 /*
3501 * Special case - lookup gave negative, but... we had foo/bar/
3502 * From the vfs_mknod() POV we just have a negative dentry -
3503 * all is fine. Let's be bastards - you had / on the end, you've
3504 * been asking for (non-existent) directory. -ENOENT for you.
3505 */
3506 if (unlikely(!is_dir && last.name[last.len])) {
3507 error = -ENOENT;
3508 goto fail;
3509 }
3510 if (unlikely(err2)) {
3511 error = err2;
3512 goto fail;
3513 }
3514 putname(name);
3515 return dentry;
3516fail:
3517 dput(dentry);
3518 dentry = ERR_PTR(error);
3519unlock:
3520 inode_unlock(path->dentry->d_inode);
3521 if (!err2)
3522 mnt_drop_write(path->mnt);
3523out:
3524 path_put(path);
3525 putname(name);
3526 return dentry;
3527}
3528
3529struct dentry *kern_path_create(int dfd, const char *pathname,
3530 struct path *path, unsigned int lookup_flags)
3531{
3532 return filename_create(dfd, getname_kernel(pathname),
3533 path, lookup_flags);
3534}
3535EXPORT_SYMBOL(kern_path_create);
3536
3537void done_path_create(struct path *path, struct dentry *dentry)
3538{
3539 dput(dentry);
3540 inode_unlock(path->dentry->d_inode);
3541 mnt_drop_write(path->mnt);
3542 path_put(path);
3543}
3544EXPORT_SYMBOL(done_path_create);
3545
3546inline struct dentry *user_path_create(int dfd, const char __user *pathname,
3547 struct path *path, unsigned int lookup_flags)
3548{
3549 return filename_create(dfd, getname(pathname), path, lookup_flags);
3550}
3551EXPORT_SYMBOL(user_path_create);
3552
3553int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
3554{
3555 int error = may_create(dir, dentry);
3556
3557 if (error)
3558 return error;
3559
3560 if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
3561 return -EPERM;
3562
3563 if (!dir->i_op->mknod)
3564 return -EPERM;
3565
3566 error = devcgroup_inode_mknod(mode, dev);
3567 if (error)
3568 return error;
3569
3570 error = security_inode_mknod(dir, dentry, mode, dev);
3571 if (error)
3572 return error;
3573
3574 error = dir->i_op->mknod(dir, dentry, mode, dev);
3575 if (!error)
3576 fsnotify_create(dir, dentry);
3577 return error;
3578}
3579EXPORT_SYMBOL(vfs_mknod);
3580
3581static int may_mknod(umode_t mode)
3582{
3583 switch (mode & S_IFMT) {
3584 case S_IFREG:
3585 case S_IFCHR:
3586 case S_IFBLK:
3587 case S_IFIFO:
3588 case S_IFSOCK:
3589 case 0: /* zero mode translates to S_IFREG */
3590 return 0;
3591 case S_IFDIR:
3592 return -EPERM;
3593 default:
3594 return -EINVAL;
3595 }
3596}
3597
3598SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,
3599 unsigned, dev)
3600{
3601 struct dentry *dentry;
3602 struct path path;
3603 int error;
3604 unsigned int lookup_flags = 0;
3605
3606 error = may_mknod(mode);
3607 if (error)
3608 return error;
3609retry:
3610 dentry = user_path_create(dfd, filename, &path, lookup_flags);
3611 if (IS_ERR(dentry))
3612 return PTR_ERR(dentry);
3613
3614 if (!IS_POSIXACL(path.dentry->d_inode))
3615 mode &= ~current_umask();
3616 error = security_path_mknod(&path, dentry, mode, dev);
3617 if (error)
3618 goto out;
3619 switch (mode & S_IFMT) {
3620 case 0: case S_IFREG:
3621 error = vfs_create(path.dentry->d_inode,dentry,mode,true);
3622 break;
3623 case S_IFCHR: case S_IFBLK:
3624 error = vfs_mknod(path.dentry->d_inode,dentry,mode,
3625 new_decode_dev(dev));
3626 break;
3627 case S_IFIFO: case S_IFSOCK:
3628 error = vfs_mknod(path.dentry->d_inode,dentry,mode,0);
3629 break;
3630 }
3631out:
3632 done_path_create(&path, dentry);
3633 if (retry_estale(error, lookup_flags)) {
3634 lookup_flags |= LOOKUP_REVAL;
3635 goto retry;
3636 }
3637 return error;
3638}
3639
3640SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev)
3641{
3642 return sys_mknodat(AT_FDCWD, filename, mode, dev);
3643}
3644
3645int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
3646{
3647 int error = may_create(dir, dentry);
3648 unsigned max_links = dir->i_sb->s_max_links;
3649
3650 if (error)
3651 return error;
3652
3653 if (!dir->i_op->mkdir)
3654 return -EPERM;
3655
3656 mode &= (S_IRWXUGO|S_ISVTX);
3657 error = security_inode_mkdir(dir, dentry, mode);
3658 if (error)
3659 return error;
3660
3661 if (max_links && dir->i_nlink >= max_links)
3662 return -EMLINK;
3663
3664 error = dir->i_op->mkdir(dir, dentry, mode);
3665 if (!error)
3666 fsnotify_mkdir(dir, dentry);
3667 return error;
3668}
3669EXPORT_SYMBOL(vfs_mkdir);
3670
3671SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
3672{
3673 struct dentry *dentry;
3674 struct path path;
3675 int error;
3676 unsigned int lookup_flags = LOOKUP_DIRECTORY;
3677
3678retry:
3679 dentry = user_path_create(dfd, pathname, &path, lookup_flags);
3680 if (IS_ERR(dentry))
3681 return PTR_ERR(dentry);
3682
3683 if (!IS_POSIXACL(path.dentry->d_inode))
3684 mode &= ~current_umask();
3685 error = security_path_mkdir(&path, dentry, mode);
3686 if (!error)
3687 error = vfs_mkdir(path.dentry->d_inode, dentry, mode);
3688 done_path_create(&path, dentry);
3689 if (retry_estale(error, lookup_flags)) {
3690 lookup_flags |= LOOKUP_REVAL;
3691 goto retry;
3692 }
3693 return error;
3694}
3695
3696SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode)
3697{
3698 return sys_mkdirat(AT_FDCWD, pathname, mode);
3699}
3700
3701int vfs_rmdir(struct inode *dir, struct dentry *dentry)
3702{
3703 int error = may_delete(dir, dentry, 1);
3704
3705 if (error)
3706 return error;
3707
3708 if (!dir->i_op->rmdir)
3709 return -EPERM;
3710
3711 dget(dentry);
3712 inode_lock(dentry->d_inode);
3713
3714 error = -EBUSY;
3715 if (is_local_mountpoint(dentry))
3716 goto out;
3717
3718 error = security_inode_rmdir(dir, dentry);
3719 if (error)
3720 goto out;
3721
3722 shrink_dcache_parent(dentry);
3723 error = dir->i_op->rmdir(dir, dentry);
3724 if (error)
3725 goto out;
3726
3727 dentry->d_inode->i_flags |= S_DEAD;
3728 dont_mount(dentry);
3729 detach_mounts(dentry);
3730
3731out:
3732 inode_unlock(dentry->d_inode);
3733 dput(dentry);
3734 if (!error)
3735 d_delete(dentry);
3736 return error;
3737}
3738EXPORT_SYMBOL(vfs_rmdir);
3739
3740static long do_rmdir(int dfd, const char __user *pathname)
3741{
3742 int error = 0;
3743 struct filename *name;
3744 struct dentry *dentry;
3745 struct path path;
3746 struct qstr last;
3747 int type;
3748 unsigned int lookup_flags = 0;
3749retry:
3750 name = user_path_parent(dfd, pathname,
3751 &path, &last, &type, lookup_flags);
3752 if (IS_ERR(name))
3753 return PTR_ERR(name);
3754
3755 switch (type) {
3756 case LAST_DOTDOT:
3757 error = -ENOTEMPTY;
3758 goto exit1;
3759 case LAST_DOT:
3760 error = -EINVAL;
3761 goto exit1;
3762 case LAST_ROOT:
3763 error = -EBUSY;
3764 goto exit1;
3765 }
3766
3767 error = mnt_want_write(path.mnt);
3768 if (error)
3769 goto exit1;
3770
3771 inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT);
3772 dentry = __lookup_hash(&last, path.dentry, lookup_flags);
3773 error = PTR_ERR(dentry);
3774 if (IS_ERR(dentry))
3775 goto exit2;
3776 if (!dentry->d_inode) {
3777 error = -ENOENT;
3778 goto exit3;
3779 }
3780 error = security_path_rmdir(&path, dentry);
3781 if (error)
3782 goto exit3;
3783 error = vfs_rmdir(path.dentry->d_inode, dentry);
3784exit3:
3785 dput(dentry);
3786exit2:
3787 inode_unlock(path.dentry->d_inode);
3788 mnt_drop_write(path.mnt);
3789exit1:
3790 path_put(&path);
3791 putname(name);
3792 if (retry_estale(error, lookup_flags)) {
3793 lookup_flags |= LOOKUP_REVAL;
3794 goto retry;
3795 }
3796 return error;
3797}
3798
3799SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
3800{
3801 return do_rmdir(AT_FDCWD, pathname);
3802}
3803
3804/**
3805 * vfs_unlink - unlink a filesystem object
3806 * @dir: parent directory
3807 * @dentry: victim
3808 * @delegated_inode: returns victim inode, if the inode is delegated.
3809 *
3810 * The caller must hold dir->i_mutex.
3811 *
3812 * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and
3813 * return a reference to the inode in delegated_inode. The caller
3814 * should then break the delegation on that inode and retry. Because
3815 * breaking a delegation may take a long time, the caller should drop
3816 * dir->i_mutex before doing so.
3817 *
3818 * Alternatively, a caller may pass NULL for delegated_inode. This may
3819 * be appropriate for callers that expect the underlying filesystem not
3820 * to be NFS exported.
3821 */
3822int vfs_unlink(struct inode *dir, struct dentry *dentry, struct inode **delegated_inode)
3823{
3824 struct inode *target = dentry->d_inode;
3825 int error = may_delete(dir, dentry, 0);
3826
3827 if (error)
3828 return error;
3829
3830 if (!dir->i_op->unlink)
3831 return -EPERM;
3832
3833 inode_lock(target);
3834 if (is_local_mountpoint(dentry))
3835 error = -EBUSY;
3836 else {
3837 error = security_inode_unlink(dir, dentry);
3838 if (!error) {
3839 error = try_break_deleg(target, delegated_inode);
3840 if (error)
3841 goto out;
3842 error = dir->i_op->unlink(dir, dentry);
3843 if (!error) {
3844 dont_mount(dentry);
3845 detach_mounts(dentry);
3846 }
3847 }
3848 }
3849out:
3850 inode_unlock(target);
3851
3852 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
3853 if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
3854 fsnotify_link_count(target);
3855 d_delete(dentry);
3856 }
3857
3858 return error;
3859}
3860EXPORT_SYMBOL(vfs_unlink);
3861
3862/*
3863 * Make sure that the actual truncation of the file will occur outside its
3864 * directory's i_mutex. Truncate can take a long time if there is a lot of
3865 * writeout happening, and we don't want to prevent access to the directory
3866 * while waiting on the I/O.
3867 */
3868static long do_unlinkat(int dfd, const char __user *pathname)
3869{
3870 int error;
3871 struct filename *name;
3872 struct dentry *dentry;
3873 struct path path;
3874 struct qstr last;
3875 int type;
3876 struct inode *inode = NULL;
3877 struct inode *delegated_inode = NULL;
3878 unsigned int lookup_flags = 0;
3879retry:
3880 name = user_path_parent(dfd, pathname,
3881 &path, &last, &type, lookup_flags);
3882 if (IS_ERR(name))
3883 return PTR_ERR(name);
3884
3885 error = -EISDIR;
3886 if (type != LAST_NORM)
3887 goto exit1;
3888
3889 error = mnt_want_write(path.mnt);
3890 if (error)
3891 goto exit1;
3892retry_deleg:
3893 inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT);
3894 dentry = __lookup_hash(&last, path.dentry, lookup_flags);
3895 error = PTR_ERR(dentry);
3896 if (!IS_ERR(dentry)) {
3897 /* Why not before? Because we want correct error value */
3898 if (last.name[last.len])
3899 goto slashes;
3900 inode = dentry->d_inode;
3901 if (d_is_negative(dentry))
3902 goto slashes;
3903 ihold(inode);
3904 error = security_path_unlink(&path, dentry);
3905 if (error)
3906 goto exit2;
3907 error = vfs_unlink(path.dentry->d_inode, dentry, &delegated_inode);
3908exit2:
3909 dput(dentry);
3910 }
3911 inode_unlock(path.dentry->d_inode);
3912 if (inode)
3913 iput(inode); /* truncate the inode here */
3914 inode = NULL;
3915 if (delegated_inode) {
3916 error = break_deleg_wait(&delegated_inode);
3917 if (!error)
3918 goto retry_deleg;
3919 }
3920 mnt_drop_write(path.mnt);
3921exit1:
3922 path_put(&path);
3923 putname(name);
3924 if (retry_estale(error, lookup_flags)) {
3925 lookup_flags |= LOOKUP_REVAL;
3926 inode = NULL;
3927 goto retry;
3928 }
3929 return error;
3930
3931slashes:
3932 if (d_is_negative(dentry))
3933 error = -ENOENT;
3934 else if (d_is_dir(dentry))
3935 error = -EISDIR;
3936 else
3937 error = -ENOTDIR;
3938 goto exit2;
3939}
3940
3941SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
3942{
3943 if ((flag & ~AT_REMOVEDIR) != 0)
3944 return -EINVAL;
3945
3946 if (flag & AT_REMOVEDIR)
3947 return do_rmdir(dfd, pathname);
3948
3949 return do_unlinkat(dfd, pathname);
3950}
3951
3952SYSCALL_DEFINE1(unlink, const char __user *, pathname)
3953{
3954 return do_unlinkat(AT_FDCWD, pathname);
3955}
3956
3957int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
3958{
3959 int error = may_create(dir, dentry);
3960
3961 if (error)
3962 return error;
3963
3964 if (!dir->i_op->symlink)
3965 return -EPERM;
3966
3967 error = security_inode_symlink(dir, dentry, oldname);
3968 if (error)
3969 return error;
3970
3971 error = dir->i_op->symlink(dir, dentry, oldname);
3972 if (!error)
3973 fsnotify_create(dir, dentry);
3974 return error;
3975}
3976EXPORT_SYMBOL(vfs_symlink);
3977
3978SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
3979 int, newdfd, const char __user *, newname)
3980{
3981 int error;
3982 struct filename *from;
3983 struct dentry *dentry;
3984 struct path path;
3985 unsigned int lookup_flags = 0;
3986
3987 from = getname(oldname);
3988 if (IS_ERR(from))
3989 return PTR_ERR(from);
3990retry:
3991 dentry = user_path_create(newdfd, newname, &path, lookup_flags);
3992 error = PTR_ERR(dentry);
3993 if (IS_ERR(dentry))
3994 goto out_putname;
3995
3996 error = security_path_symlink(&path, dentry, from->name);
3997 if (!error)
3998 error = vfs_symlink(path.dentry->d_inode, dentry, from->name);
3999 done_path_create(&path, dentry);
4000 if (retry_estale(error, lookup_flags)) {
4001 lookup_flags |= LOOKUP_REVAL;
4002 goto retry;
4003 }
4004out_putname:
4005 putname(from);
4006 return error;
4007}
4008
4009SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
4010{
4011 return sys_symlinkat(oldname, AT_FDCWD, newname);
4012}
4013
4014/**
4015 * vfs_link - create a new link
4016 * @old_dentry: object to be linked
4017 * @dir: new parent
4018 * @new_dentry: where to create the new link
4019 * @delegated_inode: returns inode needing a delegation break
4020 *
4021 * The caller must hold dir->i_mutex
4022 *
4023 * If vfs_link discovers a delegation on the to-be-linked file in need
4024 * of breaking, it will return -EWOULDBLOCK and return a reference to the
4025 * inode in delegated_inode. The caller should then break the delegation
4026 * and retry. Because breaking a delegation may take a long time, the
4027 * caller should drop the i_mutex before doing so.
4028 *
4029 * Alternatively, a caller may pass NULL for delegated_inode. This may
4030 * be appropriate for callers that expect the underlying filesystem not
4031 * to be NFS exported.
4032 */
4033int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry, struct inode **delegated_inode)
4034{
4035 struct inode *inode = old_dentry->d_inode;
4036 unsigned max_links = dir->i_sb->s_max_links;
4037 int error;
4038
4039 if (!inode)
4040 return -ENOENT;
4041
4042 error = may_create(dir, new_dentry);
4043 if (error)
4044 return error;
4045
4046 if (dir->i_sb != inode->i_sb)
4047 return -EXDEV;
4048
4049 /*
4050 * A link to an append-only or immutable file cannot be created.
4051 */
4052 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
4053 return -EPERM;
4054 if (!dir->i_op->link)
4055 return -EPERM;
4056 if (S_ISDIR(inode->i_mode))
4057 return -EPERM;
4058
4059 error = security_inode_link(old_dentry, dir, new_dentry);
4060 if (error)
4061 return error;
4062
4063 inode_lock(inode);
4064 /* Make sure we don't allow creating hardlink to an unlinked file */
4065 if (inode->i_nlink == 0 && !(inode->i_state & I_LINKABLE))
4066 error = -ENOENT;
4067 else if (max_links && inode->i_nlink >= max_links)
4068 error = -EMLINK;
4069 else {
4070 error = try_break_deleg(inode, delegated_inode);
4071 if (!error)
4072 error = dir->i_op->link(old_dentry, dir, new_dentry);
4073 }
4074
4075 if (!error && (inode->i_state & I_LINKABLE)) {
4076 spin_lock(&inode->i_lock);
4077 inode->i_state &= ~I_LINKABLE;
4078 spin_unlock(&inode->i_lock);
4079 }
4080 inode_unlock(inode);
4081 if (!error)
4082 fsnotify_link(dir, inode, new_dentry);
4083 return error;
4084}
4085EXPORT_SYMBOL(vfs_link);
4086
4087/*
4088 * Hardlinks are often used in delicate situations. We avoid
4089 * security-related surprises by not following symlinks on the
4090 * newname. --KAB
4091 *
4092 * We don't follow them on the oldname either to be compatible
4093 * with linux 2.0, and to avoid hard-linking to directories
4094 * and other special files. --ADM
4095 */
4096SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
4097 int, newdfd, const char __user *, newname, int, flags)
4098{
4099 struct dentry *new_dentry;
4100 struct path old_path, new_path;
4101 struct inode *delegated_inode = NULL;
4102 int how = 0;
4103 int error;
4104
4105 if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
4106 return -EINVAL;
4107 /*
4108 * To use null names we require CAP_DAC_READ_SEARCH
4109 * This ensures that not everyone will be able to create
4110 * handlink using the passed filedescriptor.
4111 */
4112 if (flags & AT_EMPTY_PATH) {
4113 if (!capable(CAP_DAC_READ_SEARCH))
4114 return -ENOENT;
4115 how = LOOKUP_EMPTY;
4116 }
4117
4118 if (flags & AT_SYMLINK_FOLLOW)
4119 how |= LOOKUP_FOLLOW;
4120retry:
4121 error = user_path_at(olddfd, oldname, how, &old_path);
4122 if (error)
4123 return error;
4124
4125 new_dentry = user_path_create(newdfd, newname, &new_path,
4126 (how & LOOKUP_REVAL));
4127 error = PTR_ERR(new_dentry);
4128 if (IS_ERR(new_dentry))
4129 goto out;
4130
4131 error = -EXDEV;
4132 if (old_path.mnt != new_path.mnt)
4133 goto out_dput;
4134 error = may_linkat(&old_path);
4135 if (unlikely(error))
4136 goto out_dput;
4137 error = security_path_link(old_path.dentry, &new_path, new_dentry);
4138 if (error)
4139 goto out_dput;
4140 error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry, &delegated_inode);
4141out_dput:
4142 done_path_create(&new_path, new_dentry);
4143 if (delegated_inode) {
4144 error = break_deleg_wait(&delegated_inode);
4145 if (!error) {
4146 path_put(&old_path);
4147 goto retry;
4148 }
4149 }
4150 if (retry_estale(error, how)) {
4151 path_put(&old_path);
4152 how |= LOOKUP_REVAL;
4153 goto retry;
4154 }
4155out:
4156 path_put(&old_path);
4157
4158 return error;
4159}
4160
4161SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
4162{
4163 return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
4164}
4165
4166/**
4167 * vfs_rename - rename a filesystem object
4168 * @old_dir: parent of source
4169 * @old_dentry: source
4170 * @new_dir: parent of destination
4171 * @new_dentry: destination
4172 * @delegated_inode: returns an inode needing a delegation break
4173 * @flags: rename flags
4174 *
4175 * The caller must hold multiple mutexes--see lock_rename()).
4176 *
4177 * If vfs_rename discovers a delegation in need of breaking at either
4178 * the source or destination, it will return -EWOULDBLOCK and return a
4179 * reference to the inode in delegated_inode. The caller should then
4180 * break the delegation and retry. Because breaking a delegation may
4181 * take a long time, the caller should drop all locks before doing
4182 * so.
4183 *
4184 * Alternatively, a caller may pass NULL for delegated_inode. This may
4185 * be appropriate for callers that expect the underlying filesystem not
4186 * to be NFS exported.
4187 *
4188 * The worst of all namespace operations - renaming directory. "Perverted"
4189 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
4190 * Problems:
4191 * a) we can get into loop creation.
4192 * b) race potential - two innocent renames can create a loop together.
4193 * That's where 4.4 screws up. Current fix: serialization on
4194 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
4195 * story.
4196 * c) we have to lock _four_ objects - parents and victim (if it exists),
4197 * and source (if it is not a directory).
4198 * And that - after we got ->i_mutex on parents (until then we don't know
4199 * whether the target exists). Solution: try to be smart with locking
4200 * order for inodes. We rely on the fact that tree topology may change
4201 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
4202 * move will be locked. Thus we can rank directories by the tree
4203 * (ancestors first) and rank all non-directories after them.
4204 * That works since everybody except rename does "lock parent, lookup,
4205 * lock child" and rename is under ->s_vfs_rename_mutex.
4206 * HOWEVER, it relies on the assumption that any object with ->lookup()
4207 * has no more than 1 dentry. If "hybrid" objects will ever appear,
4208 * we'd better make sure that there's no link(2) for them.
4209 * d) conversion from fhandle to dentry may come in the wrong moment - when
4210 * we are removing the target. Solution: we will have to grab ->i_mutex
4211 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
4212 * ->i_mutex on parents, which works but leads to some truly excessive
4213 * locking].
4214 */
4215int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
4216 struct inode *new_dir, struct dentry *new_dentry,
4217 struct inode **delegated_inode, unsigned int flags)
4218{
4219 int error;
4220 bool is_dir = d_is_dir(old_dentry);
4221 const unsigned char *old_name;
4222 struct inode *source = old_dentry->d_inode;
4223 struct inode *target = new_dentry->d_inode;
4224 bool new_is_dir = false;
4225 unsigned max_links = new_dir->i_sb->s_max_links;
4226
4227 /*
4228 * Check source == target.
4229 * On overlayfs need to look at underlying inodes.
4230 */
4231 if (vfs_select_inode(old_dentry, 0) == vfs_select_inode(new_dentry, 0))
4232 return 0;
4233
4234 error = may_delete(old_dir, old_dentry, is_dir);
4235 if (error)
4236 return error;
4237
4238 if (!target) {
4239 error = may_create(new_dir, new_dentry);
4240 } else {
4241 new_is_dir = d_is_dir(new_dentry);
4242
4243 if (!(flags & RENAME_EXCHANGE))
4244 error = may_delete(new_dir, new_dentry, is_dir);
4245 else
4246 error = may_delete(new_dir, new_dentry, new_is_dir);
4247 }
4248 if (error)
4249 return error;
4250
4251 if (!old_dir->i_op->rename && !old_dir->i_op->rename2)
4252 return -EPERM;
4253
4254 if (flags && !old_dir->i_op->rename2)
4255 return -EINVAL;
4256
4257 /*
4258 * If we are going to change the parent - check write permissions,
4259 * we'll need to flip '..'.
4260 */
4261 if (new_dir != old_dir) {
4262 if (is_dir) {
4263 error = inode_permission(source, MAY_WRITE);
4264 if (error)
4265 return error;
4266 }
4267 if ((flags & RENAME_EXCHANGE) && new_is_dir) {
4268 error = inode_permission(target, MAY_WRITE);
4269 if (error)
4270 return error;
4271 }
4272 }
4273
4274 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry,
4275 flags);
4276 if (error)
4277 return error;
4278
4279 old_name = fsnotify_oldname_init(old_dentry->d_name.name);
4280 dget(new_dentry);
4281 if (!is_dir || (flags & RENAME_EXCHANGE))
4282 lock_two_nondirectories(source, target);
4283 else if (target)
4284 inode_lock(target);
4285
4286 error = -EBUSY;
4287 if (is_local_mountpoint(old_dentry) || is_local_mountpoint(new_dentry))
4288 goto out;
4289
4290 if (max_links && new_dir != old_dir) {
4291 error = -EMLINK;
4292 if (is_dir && !new_is_dir && new_dir->i_nlink >= max_links)
4293 goto out;
4294 if ((flags & RENAME_EXCHANGE) && !is_dir && new_is_dir &&
4295 old_dir->i_nlink >= max_links)
4296 goto out;
4297 }
4298 if (is_dir && !(flags & RENAME_EXCHANGE) && target)
4299 shrink_dcache_parent(new_dentry);
4300 if (!is_dir) {
4301 error = try_break_deleg(source, delegated_inode);
4302 if (error)
4303 goto out;
4304 }
4305 if (target && !new_is_dir) {
4306 error = try_break_deleg(target, delegated_inode);
4307 if (error)
4308 goto out;
4309 }
4310 if (!old_dir->i_op->rename2) {
4311 error = old_dir->i_op->rename(old_dir, old_dentry,
4312 new_dir, new_dentry);
4313 } else {
4314 WARN_ON(old_dir->i_op->rename != NULL);
4315 error = old_dir->i_op->rename2(old_dir, old_dentry,
4316 new_dir, new_dentry, flags);
4317 }
4318 if (error)
4319 goto out;
4320
4321 if (!(flags & RENAME_EXCHANGE) && target) {
4322 if (is_dir)
4323 target->i_flags |= S_DEAD;
4324 dont_mount(new_dentry);
4325 detach_mounts(new_dentry);
4326 }
4327 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) {
4328 if (!(flags & RENAME_EXCHANGE))
4329 d_move(old_dentry, new_dentry);
4330 else
4331 d_exchange(old_dentry, new_dentry);
4332 }
4333out:
4334 if (!is_dir || (flags & RENAME_EXCHANGE))
4335 unlock_two_nondirectories(source, target);
4336 else if (target)
4337 inode_unlock(target);
4338 dput(new_dentry);
4339 if (!error) {
4340 fsnotify_move(old_dir, new_dir, old_name, is_dir,
4341 !(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry);
4342 if (flags & RENAME_EXCHANGE) {
4343 fsnotify_move(new_dir, old_dir, old_dentry->d_name.name,
4344 new_is_dir, NULL, new_dentry);
4345 }
4346 }
4347 fsnotify_oldname_free(old_name);
4348
4349 return error;
4350}
4351EXPORT_SYMBOL(vfs_rename);
4352
4353SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname,
4354 int, newdfd, const char __user *, newname, unsigned int, flags)
4355{
4356 struct dentry *old_dentry, *new_dentry;
4357 struct dentry *trap;
4358 struct path old_path, new_path;
4359 struct qstr old_last, new_last;
4360 int old_type, new_type;
4361 struct inode *delegated_inode = NULL;
4362 struct filename *from;
4363 struct filename *to;
4364 unsigned int lookup_flags = 0, target_flags = LOOKUP_RENAME_TARGET;
4365 bool should_retry = false;
4366 int error;
4367
4368 if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
4369 return -EINVAL;
4370
4371 if ((flags & (RENAME_NOREPLACE | RENAME_WHITEOUT)) &&
4372 (flags & RENAME_EXCHANGE))
4373 return -EINVAL;
4374
4375 if ((flags & RENAME_WHITEOUT) && !capable(CAP_MKNOD))
4376 return -EPERM;
4377
4378 if (flags & RENAME_EXCHANGE)
4379 target_flags = 0;
4380
4381retry:
4382 from = user_path_parent(olddfd, oldname,
4383 &old_path, &old_last, &old_type, lookup_flags);
4384 if (IS_ERR(from)) {
4385 error = PTR_ERR(from);
4386 goto exit;
4387 }
4388
4389 to = user_path_parent(newdfd, newname,
4390 &new_path, &new_last, &new_type, lookup_flags);
4391 if (IS_ERR(to)) {
4392 error = PTR_ERR(to);
4393 goto exit1;
4394 }
4395
4396 error = -EXDEV;
4397 if (old_path.mnt != new_path.mnt)
4398 goto exit2;
4399
4400 error = -EBUSY;
4401 if (old_type != LAST_NORM)
4402 goto exit2;
4403
4404 if (flags & RENAME_NOREPLACE)
4405 error = -EEXIST;
4406 if (new_type != LAST_NORM)
4407 goto exit2;
4408
4409 error = mnt_want_write(old_path.mnt);
4410 if (error)
4411 goto exit2;
4412
4413retry_deleg:
4414 trap = lock_rename(new_path.dentry, old_path.dentry);
4415
4416 old_dentry = __lookup_hash(&old_last, old_path.dentry, lookup_flags);
4417 error = PTR_ERR(old_dentry);
4418 if (IS_ERR(old_dentry))
4419 goto exit3;
4420 /* source must exist */
4421 error = -ENOENT;
4422 if (d_is_negative(old_dentry))
4423 goto exit4;
4424 new_dentry = __lookup_hash(&new_last, new_path.dentry, lookup_flags | target_flags);
4425 error = PTR_ERR(new_dentry);
4426 if (IS_ERR(new_dentry))
4427 goto exit4;
4428 error = -EEXIST;
4429 if ((flags & RENAME_NOREPLACE) && d_is_positive(new_dentry))
4430 goto exit5;
4431 if (flags & RENAME_EXCHANGE) {
4432 error = -ENOENT;
4433 if (d_is_negative(new_dentry))
4434 goto exit5;
4435
4436 if (!d_is_dir(new_dentry)) {
4437 error = -ENOTDIR;
4438 if (new_last.name[new_last.len])
4439 goto exit5;
4440 }
4441 }
4442 /* unless the source is a directory trailing slashes give -ENOTDIR */
4443 if (!d_is_dir(old_dentry)) {
4444 error = -ENOTDIR;
4445 if (old_last.name[old_last.len])
4446 goto exit5;
4447 if (!(flags & RENAME_EXCHANGE) && new_last.name[new_last.len])
4448 goto exit5;
4449 }
4450 /* source should not be ancestor of target */
4451 error = -EINVAL;
4452 if (old_dentry == trap)
4453 goto exit5;
4454 /* target should not be an ancestor of source */
4455 if (!(flags & RENAME_EXCHANGE))
4456 error = -ENOTEMPTY;
4457 if (new_dentry == trap)
4458 goto exit5;
4459
4460 error = security_path_rename(&old_path, old_dentry,
4461 &new_path, new_dentry, flags);
4462 if (error)
4463 goto exit5;
4464 error = vfs_rename(old_path.dentry->d_inode, old_dentry,
4465 new_path.dentry->d_inode, new_dentry,
4466 &delegated_inode, flags);
4467exit5:
4468 dput(new_dentry);
4469exit4:
4470 dput(old_dentry);
4471exit3:
4472 unlock_rename(new_path.dentry, old_path.dentry);
4473 if (delegated_inode) {
4474 error = break_deleg_wait(&delegated_inode);
4475 if (!error)
4476 goto retry_deleg;
4477 }
4478 mnt_drop_write(old_path.mnt);
4479exit2:
4480 if (retry_estale(error, lookup_flags))
4481 should_retry = true;
4482 path_put(&new_path);
4483 putname(to);
4484exit1:
4485 path_put(&old_path);
4486 putname(from);
4487 if (should_retry) {
4488 should_retry = false;
4489 lookup_flags |= LOOKUP_REVAL;
4490 goto retry;
4491 }
4492exit:
4493 return error;
4494}
4495
4496SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
4497 int, newdfd, const char __user *, newname)
4498{
4499 return sys_renameat2(olddfd, oldname, newdfd, newname, 0);
4500}
4501
4502SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
4503{
4504 return sys_renameat2(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
4505}
4506
4507int vfs_whiteout(struct inode *dir, struct dentry *dentry)
4508{
4509 int error = may_create(dir, dentry);
4510 if (error)
4511 return error;
4512
4513 if (!dir->i_op->mknod)
4514 return -EPERM;
4515
4516 return dir->i_op->mknod(dir, dentry,
4517 S_IFCHR | WHITEOUT_MODE, WHITEOUT_DEV);
4518}
4519EXPORT_SYMBOL(vfs_whiteout);
4520
4521int readlink_copy(char __user *buffer, int buflen, const char *link)
4522{
4523 int len = PTR_ERR(link);
4524 if (IS_ERR(link))
4525 goto out;
4526
4527 len = strlen(link);
4528 if (len > (unsigned) buflen)
4529 len = buflen;
4530 if (copy_to_user(buffer, link, len))
4531 len = -EFAULT;
4532out:
4533 return len;
4534}
4535EXPORT_SYMBOL(readlink_copy);
4536
4537/*
4538 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
4539 * have ->get_link() not calling nd_jump_link(). Using (or not using) it
4540 * for any given inode is up to filesystem.
4541 */
4542int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
4543{
4544 DEFINE_DELAYED_CALL(done);
4545 struct inode *inode = d_inode(dentry);
4546 const char *link = inode->i_link;
4547 int res;
4548
4549 if (!link) {
4550 link = inode->i_op->get_link(dentry, inode, &done);
4551 if (IS_ERR(link))
4552 return PTR_ERR(link);
4553 }
4554 res = readlink_copy(buffer, buflen, link);
4555 do_delayed_call(&done);
4556 return res;
4557}
4558EXPORT_SYMBOL(generic_readlink);
4559
4560/* get the link contents into pagecache */
4561const char *page_get_link(struct dentry *dentry, struct inode *inode,
4562 struct delayed_call *callback)
4563{
4564 char *kaddr;
4565 struct page *page;
4566 struct address_space *mapping = inode->i_mapping;
4567
4568 if (!dentry) {
4569 page = find_get_page(mapping, 0);
4570 if (!page)
4571 return ERR_PTR(-ECHILD);
4572 if (!PageUptodate(page)) {
4573 put_page(page);
4574 return ERR_PTR(-ECHILD);
4575 }
4576 } else {
4577 page = read_mapping_page(mapping, 0, NULL);
4578 if (IS_ERR(page))
4579 return (char*)page;
4580 }
4581 set_delayed_call(callback, page_put_link, page);
4582 BUG_ON(mapping_gfp_mask(mapping) & __GFP_HIGHMEM);
4583 kaddr = page_address(page);
4584 nd_terminate_link(kaddr, inode->i_size, PAGE_SIZE - 1);
4585 return kaddr;
4586}
4587
4588EXPORT_SYMBOL(page_get_link);
4589
4590void page_put_link(void *arg)
4591{
4592 put_page(arg);
4593}
4594EXPORT_SYMBOL(page_put_link);
4595
4596int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
4597{
4598 DEFINE_DELAYED_CALL(done);
4599 int res = readlink_copy(buffer, buflen,
4600 page_get_link(dentry, d_inode(dentry),
4601 &done));
4602 do_delayed_call(&done);
4603 return res;
4604}
4605EXPORT_SYMBOL(page_readlink);
4606
4607/*
4608 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
4609 */
4610int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
4611{
4612 struct address_space *mapping = inode->i_mapping;
4613 struct page *page;
4614 void *fsdata;
4615 int err;
4616 unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
4617 if (nofs)
4618 flags |= AOP_FLAG_NOFS;
4619
4620retry:
4621 err = pagecache_write_begin(NULL, mapping, 0, len-1,
4622 flags, &page, &fsdata);
4623 if (err)
4624 goto fail;
4625
4626 memcpy(page_address(page), symname, len-1);
4627
4628 err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
4629 page, fsdata);
4630 if (err < 0)
4631 goto fail;
4632 if (err < len-1)
4633 goto retry;
4634
4635 mark_inode_dirty(inode);
4636 return 0;
4637fail:
4638 return err;
4639}
4640EXPORT_SYMBOL(__page_symlink);
4641
4642int page_symlink(struct inode *inode, const char *symname, int len)
4643{
4644 return __page_symlink(inode, symname, len,
4645 !mapping_gfp_constraint(inode->i_mapping, __GFP_FS));
4646}
4647EXPORT_SYMBOL(page_symlink);
4648
4649const struct inode_operations page_symlink_inode_operations = {
4650 .readlink = generic_readlink,
4651 .get_link = page_get_link,
4652};
4653EXPORT_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/fsnotify.h>
26#include <linux/personality.h>
27#include <linux/security.h>
28#include <linux/ima.h>
29#include <linux/syscalls.h>
30#include <linux/mount.h>
31#include <linux/audit.h>
32#include <linux/capability.h>
33#include <linux/file.h>
34#include <linux/fcntl.h>
35#include <linux/device_cgroup.h>
36#include <linux/fs_struct.h>
37#include <linux/posix_acl.h>
38#include <linux/hash.h>
39#include <linux/bitops.h>
40#include <linux/init_task.h>
41#include <linux/uaccess.h>
42
43#include "internal.h"
44#include "mount.h"
45
46/* [Feb-1997 T. Schoebel-Theuer]
47 * Fundamental changes in the pathname lookup mechanisms (namei)
48 * were necessary because of omirr. The reason is that omirr needs
49 * to know the _real_ pathname, not the user-supplied one, in case
50 * of symlinks (and also when transname replacements occur).
51 *
52 * The new code replaces the old recursive symlink resolution with
53 * an iterative one (in case of non-nested symlink chains). It does
54 * this with calls to <fs>_follow_link().
55 * As a side effect, dir_namei(), _namei() and follow_link() are now
56 * replaced with a single function lookup_dentry() that can handle all
57 * the special cases of the former code.
58 *
59 * With the new dcache, the pathname is stored at each inode, at least as
60 * long as the refcount of the inode is positive. As a side effect, the
61 * size of the dcache depends on the inode cache and thus is dynamic.
62 *
63 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
64 * resolution to correspond with current state of the code.
65 *
66 * Note that the symlink resolution is not *completely* iterative.
67 * There is still a significant amount of tail- and mid- recursion in
68 * the algorithm. Also, note that <fs>_readlink() is not used in
69 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
70 * may return different results than <fs>_follow_link(). Many virtual
71 * filesystems (including /proc) exhibit this behavior.
72 */
73
74/* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
75 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
76 * and the name already exists in form of a symlink, try to create the new
77 * name indicated by the symlink. The old code always complained that the
78 * name already exists, due to not following the symlink even if its target
79 * is nonexistent. The new semantics affects also mknod() and link() when
80 * the name is a symlink pointing to a non-existent name.
81 *
82 * I don't know which semantics is the right one, since I have no access
83 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
84 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
85 * "old" one. Personally, I think the new semantics is much more logical.
86 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
87 * file does succeed in both HP-UX and SunOs, but not in Solaris
88 * and in the old Linux semantics.
89 */
90
91/* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
92 * semantics. See the comments in "open_namei" and "do_link" below.
93 *
94 * [10-Sep-98 Alan Modra] Another symlink change.
95 */
96
97/* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
98 * inside the path - always follow.
99 * in the last component in creation/removal/renaming - never follow.
100 * if LOOKUP_FOLLOW passed - follow.
101 * if the pathname has trailing slashes - follow.
102 * otherwise - don't follow.
103 * (applied in that order).
104 *
105 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
106 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
107 * During the 2.4 we need to fix the userland stuff depending on it -
108 * hopefully we will be able to get rid of that wart in 2.5. So far only
109 * XEmacs seems to be relying on it...
110 */
111/*
112 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
113 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
114 * any extra contention...
115 */
116
117/* In order to reduce some races, while at the same time doing additional
118 * checking and hopefully speeding things up, we copy filenames to the
119 * kernel data space before using them..
120 *
121 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
122 * PATH_MAX includes the nul terminator --RR.
123 */
124
125#define EMBEDDED_NAME_MAX (PATH_MAX - offsetof(struct filename, iname))
126
127struct filename *
128getname_flags(const char __user *filename, int flags, int *empty)
129{
130 struct filename *result;
131 char *kname;
132 int len;
133
134 result = audit_reusename(filename);
135 if (result)
136 return result;
137
138 result = __getname();
139 if (unlikely(!result))
140 return ERR_PTR(-ENOMEM);
141
142 /*
143 * First, try to embed the struct filename inside the names_cache
144 * allocation
145 */
146 kname = (char *)result->iname;
147 result->name = kname;
148
149 len = strncpy_from_user(kname, filename, EMBEDDED_NAME_MAX);
150 if (unlikely(len < 0)) {
151 __putname(result);
152 return ERR_PTR(len);
153 }
154
155 /*
156 * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a
157 * separate struct filename so we can dedicate the entire
158 * names_cache allocation for the pathname, and re-do the copy from
159 * userland.
160 */
161 if (unlikely(len == EMBEDDED_NAME_MAX)) {
162 const size_t size = offsetof(struct filename, iname[1]);
163 kname = (char *)result;
164
165 /*
166 * size is chosen that way we to guarantee that
167 * result->iname[0] is within the same object and that
168 * kname can't be equal to result->iname, no matter what.
169 */
170 result = kzalloc(size, GFP_KERNEL);
171 if (unlikely(!result)) {
172 __putname(kname);
173 return ERR_PTR(-ENOMEM);
174 }
175 result->name = kname;
176 len = strncpy_from_user(kname, filename, PATH_MAX);
177 if (unlikely(len < 0)) {
178 __putname(kname);
179 kfree(result);
180 return ERR_PTR(len);
181 }
182 if (unlikely(len == PATH_MAX)) {
183 __putname(kname);
184 kfree(result);
185 return ERR_PTR(-ENAMETOOLONG);
186 }
187 }
188
189 result->refcnt = 1;
190 /* The empty path is special. */
191 if (unlikely(!len)) {
192 if (empty)
193 *empty = 1;
194 if (!(flags & LOOKUP_EMPTY)) {
195 putname(result);
196 return ERR_PTR(-ENOENT);
197 }
198 }
199
200 result->uptr = filename;
201 result->aname = NULL;
202 audit_getname(result);
203 return result;
204}
205
206struct filename *
207getname(const char __user * filename)
208{
209 return getname_flags(filename, 0, NULL);
210}
211
212struct filename *
213getname_kernel(const char * filename)
214{
215 struct filename *result;
216 int len = strlen(filename) + 1;
217
218 result = __getname();
219 if (unlikely(!result))
220 return ERR_PTR(-ENOMEM);
221
222 if (len <= EMBEDDED_NAME_MAX) {
223 result->name = (char *)result->iname;
224 } else if (len <= PATH_MAX) {
225 const size_t size = offsetof(struct filename, iname[1]);
226 struct filename *tmp;
227
228 tmp = kmalloc(size, GFP_KERNEL);
229 if (unlikely(!tmp)) {
230 __putname(result);
231 return ERR_PTR(-ENOMEM);
232 }
233 tmp->name = (char *)result;
234 result = tmp;
235 } else {
236 __putname(result);
237 return ERR_PTR(-ENAMETOOLONG);
238 }
239 memcpy((char *)result->name, filename, len);
240 result->uptr = NULL;
241 result->aname = NULL;
242 result->refcnt = 1;
243 audit_getname(result);
244
245 return result;
246}
247
248void putname(struct filename *name)
249{
250 BUG_ON(name->refcnt <= 0);
251
252 if (--name->refcnt > 0)
253 return;
254
255 if (name->name != name->iname) {
256 __putname(name->name);
257 kfree(name);
258 } else
259 __putname(name);
260}
261
262/**
263 * check_acl - perform ACL permission checking
264 * @mnt_userns: user namespace of the mount the inode was found from
265 * @inode: inode to check permissions on
266 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC ...)
267 *
268 * This function performs the ACL permission checking. Since this function
269 * retrieve POSIX acls it needs to know whether it is called from a blocking or
270 * non-blocking context and thus cares about the MAY_NOT_BLOCK bit.
271 *
272 * If the inode has been found through an idmapped mount the user namespace of
273 * the vfsmount must be passed through @mnt_userns. This function will then take
274 * care to map the inode according to @mnt_userns before checking permissions.
275 * On non-idmapped mounts or if permission checking is to be performed on the
276 * raw inode simply passs init_user_ns.
277 */
278static int check_acl(struct user_namespace *mnt_userns,
279 struct inode *inode, int mask)
280{
281#ifdef CONFIG_FS_POSIX_ACL
282 struct posix_acl *acl;
283
284 if (mask & MAY_NOT_BLOCK) {
285 acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS);
286 if (!acl)
287 return -EAGAIN;
288 /* no ->get_acl() calls in RCU mode... */
289 if (is_uncached_acl(acl))
290 return -ECHILD;
291 return posix_acl_permission(mnt_userns, inode, acl, mask);
292 }
293
294 acl = get_acl(inode, ACL_TYPE_ACCESS);
295 if (IS_ERR(acl))
296 return PTR_ERR(acl);
297 if (acl) {
298 int error = posix_acl_permission(mnt_userns, inode, acl, mask);
299 posix_acl_release(acl);
300 return error;
301 }
302#endif
303
304 return -EAGAIN;
305}
306
307/**
308 * acl_permission_check - perform basic UNIX permission checking
309 * @mnt_userns: user namespace of the mount the inode was found from
310 * @inode: inode to check permissions on
311 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC ...)
312 *
313 * This function performs the basic UNIX permission checking. Since this
314 * function may retrieve POSIX acls it needs to know whether it is called from a
315 * blocking or non-blocking context and thus cares about the MAY_NOT_BLOCK bit.
316 *
317 * If the inode has been found through an idmapped mount the user namespace of
318 * the vfsmount must be passed through @mnt_userns. This function will then take
319 * care to map the inode according to @mnt_userns before checking permissions.
320 * On non-idmapped mounts or if permission checking is to be performed on the
321 * raw inode simply passs init_user_ns.
322 */
323static int acl_permission_check(struct user_namespace *mnt_userns,
324 struct inode *inode, int mask)
325{
326 unsigned int mode = inode->i_mode;
327 kuid_t i_uid;
328
329 /* Are we the owner? If so, ACL's don't matter */
330 i_uid = i_uid_into_mnt(mnt_userns, inode);
331 if (likely(uid_eq(current_fsuid(), i_uid))) {
332 mask &= 7;
333 mode >>= 6;
334 return (mask & ~mode) ? -EACCES : 0;
335 }
336
337 /* Do we have ACL's? */
338 if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
339 int error = check_acl(mnt_userns, inode, mask);
340 if (error != -EAGAIN)
341 return error;
342 }
343
344 /* Only RWX matters for group/other mode bits */
345 mask &= 7;
346
347 /*
348 * Are the group permissions different from
349 * the other permissions in the bits we care
350 * about? Need to check group ownership if so.
351 */
352 if (mask & (mode ^ (mode >> 3))) {
353 kgid_t kgid = i_gid_into_mnt(mnt_userns, inode);
354 if (in_group_p(kgid))
355 mode >>= 3;
356 }
357
358 /* Bits in 'mode' clear that we require? */
359 return (mask & ~mode) ? -EACCES : 0;
360}
361
362/**
363 * generic_permission - check for access rights on a Posix-like filesystem
364 * @mnt_userns: user namespace of the mount the inode was found from
365 * @inode: inode to check access rights for
366 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC,
367 * %MAY_NOT_BLOCK ...)
368 *
369 * Used to check for read/write/execute permissions on a file.
370 * We use "fsuid" for this, letting us set arbitrary permissions
371 * for filesystem access without changing the "normal" uids which
372 * are used for other things.
373 *
374 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
375 * request cannot be satisfied (eg. requires blocking or too much complexity).
376 * It would then be called again in ref-walk mode.
377 *
378 * If the inode has been found through an idmapped mount the user namespace of
379 * the vfsmount must be passed through @mnt_userns. This function will then take
380 * care to map the inode according to @mnt_userns before checking permissions.
381 * On non-idmapped mounts or if permission checking is to be performed on the
382 * raw inode simply passs init_user_ns.
383 */
384int generic_permission(struct user_namespace *mnt_userns, struct inode *inode,
385 int mask)
386{
387 int ret;
388
389 /*
390 * Do the basic permission checks.
391 */
392 ret = acl_permission_check(mnt_userns, inode, mask);
393 if (ret != -EACCES)
394 return ret;
395
396 if (S_ISDIR(inode->i_mode)) {
397 /* DACs are overridable for directories */
398 if (!(mask & MAY_WRITE))
399 if (capable_wrt_inode_uidgid(mnt_userns, inode,
400 CAP_DAC_READ_SEARCH))
401 return 0;
402 if (capable_wrt_inode_uidgid(mnt_userns, inode,
403 CAP_DAC_OVERRIDE))
404 return 0;
405 return -EACCES;
406 }
407
408 /*
409 * Searching includes executable on directories, else just read.
410 */
411 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
412 if (mask == MAY_READ)
413 if (capable_wrt_inode_uidgid(mnt_userns, inode,
414 CAP_DAC_READ_SEARCH))
415 return 0;
416 /*
417 * Read/write DACs are always overridable.
418 * Executable DACs are overridable when there is
419 * at least one exec bit set.
420 */
421 if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
422 if (capable_wrt_inode_uidgid(mnt_userns, inode,
423 CAP_DAC_OVERRIDE))
424 return 0;
425
426 return -EACCES;
427}
428EXPORT_SYMBOL(generic_permission);
429
430/**
431 * do_inode_permission - UNIX permission checking
432 * @mnt_userns: user namespace of the mount the inode was found from
433 * @inode: inode to check permissions on
434 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC ...)
435 *
436 * We _really_ want to just do "generic_permission()" without
437 * even looking at the inode->i_op values. So we keep a cache
438 * flag in inode->i_opflags, that says "this has not special
439 * permission function, use the fast case".
440 */
441static inline int do_inode_permission(struct user_namespace *mnt_userns,
442 struct inode *inode, int mask)
443{
444 if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) {
445 if (likely(inode->i_op->permission))
446 return inode->i_op->permission(mnt_userns, inode, mask);
447
448 /* This gets set once for the inode lifetime */
449 spin_lock(&inode->i_lock);
450 inode->i_opflags |= IOP_FASTPERM;
451 spin_unlock(&inode->i_lock);
452 }
453 return generic_permission(mnt_userns, inode, mask);
454}
455
456/**
457 * sb_permission - Check superblock-level permissions
458 * @sb: Superblock of inode to check permission on
459 * @inode: Inode to check permission on
460 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
461 *
462 * Separate out file-system wide checks from inode-specific permission checks.
463 */
464static int sb_permission(struct super_block *sb, struct inode *inode, int mask)
465{
466 if (unlikely(mask & MAY_WRITE)) {
467 umode_t mode = inode->i_mode;
468
469 /* Nobody gets write access to a read-only fs. */
470 if (sb_rdonly(sb) && (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
471 return -EROFS;
472 }
473 return 0;
474}
475
476/**
477 * inode_permission - Check for access rights to a given inode
478 * @mnt_userns: User namespace of the mount the inode was found from
479 * @inode: Inode to check permission on
480 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
481 *
482 * Check for read/write/execute permissions on an inode. We use fs[ug]id for
483 * this, letting us set arbitrary permissions for filesystem access without
484 * changing the "normal" UIDs which are used for other things.
485 *
486 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
487 */
488int inode_permission(struct user_namespace *mnt_userns,
489 struct inode *inode, int mask)
490{
491 int retval;
492
493 retval = sb_permission(inode->i_sb, inode, mask);
494 if (retval)
495 return retval;
496
497 if (unlikely(mask & MAY_WRITE)) {
498 /*
499 * Nobody gets write access to an immutable file.
500 */
501 if (IS_IMMUTABLE(inode))
502 return -EPERM;
503
504 /*
505 * Updating mtime will likely cause i_uid and i_gid to be
506 * written back improperly if their true value is unknown
507 * to the vfs.
508 */
509 if (HAS_UNMAPPED_ID(mnt_userns, inode))
510 return -EACCES;
511 }
512
513 retval = do_inode_permission(mnt_userns, inode, mask);
514 if (retval)
515 return retval;
516
517 retval = devcgroup_inode_permission(inode, mask);
518 if (retval)
519 return retval;
520
521 return security_inode_permission(inode, mask);
522}
523EXPORT_SYMBOL(inode_permission);
524
525/**
526 * path_get - get a reference to a path
527 * @path: path to get the reference to
528 *
529 * Given a path increment the reference count to the dentry and the vfsmount.
530 */
531void path_get(const struct path *path)
532{
533 mntget(path->mnt);
534 dget(path->dentry);
535}
536EXPORT_SYMBOL(path_get);
537
538/**
539 * path_put - put a reference to a path
540 * @path: path to put the reference to
541 *
542 * Given a path decrement the reference count to the dentry and the vfsmount.
543 */
544void path_put(const struct path *path)
545{
546 dput(path->dentry);
547 mntput(path->mnt);
548}
549EXPORT_SYMBOL(path_put);
550
551#define EMBEDDED_LEVELS 2
552struct nameidata {
553 struct path path;
554 struct qstr last;
555 struct path root;
556 struct inode *inode; /* path.dentry.d_inode */
557 unsigned int flags, state;
558 unsigned seq, m_seq, r_seq;
559 int last_type;
560 unsigned depth;
561 int total_link_count;
562 struct saved {
563 struct path link;
564 struct delayed_call done;
565 const char *name;
566 unsigned seq;
567 } *stack, internal[EMBEDDED_LEVELS];
568 struct filename *name;
569 struct nameidata *saved;
570 unsigned root_seq;
571 int dfd;
572 kuid_t dir_uid;
573 umode_t dir_mode;
574} __randomize_layout;
575
576#define ND_ROOT_PRESET 1
577#define ND_ROOT_GRABBED 2
578#define ND_JUMPED 4
579
580static void __set_nameidata(struct nameidata *p, int dfd, struct filename *name)
581{
582 struct nameidata *old = current->nameidata;
583 p->stack = p->internal;
584 p->depth = 0;
585 p->dfd = dfd;
586 p->name = name;
587 p->path.mnt = NULL;
588 p->path.dentry = NULL;
589 p->total_link_count = old ? old->total_link_count : 0;
590 p->saved = old;
591 current->nameidata = p;
592}
593
594static inline void set_nameidata(struct nameidata *p, int dfd, struct filename *name,
595 const struct path *root)
596{
597 __set_nameidata(p, dfd, name);
598 p->state = 0;
599 if (unlikely(root)) {
600 p->state = ND_ROOT_PRESET;
601 p->root = *root;
602 }
603}
604
605static void restore_nameidata(void)
606{
607 struct nameidata *now = current->nameidata, *old = now->saved;
608
609 current->nameidata = old;
610 if (old)
611 old->total_link_count = now->total_link_count;
612 if (now->stack != now->internal)
613 kfree(now->stack);
614}
615
616static bool nd_alloc_stack(struct nameidata *nd)
617{
618 struct saved *p;
619
620 p= kmalloc_array(MAXSYMLINKS, sizeof(struct saved),
621 nd->flags & LOOKUP_RCU ? GFP_ATOMIC : GFP_KERNEL);
622 if (unlikely(!p))
623 return false;
624 memcpy(p, nd->internal, sizeof(nd->internal));
625 nd->stack = p;
626 return true;
627}
628
629/**
630 * path_connected - Verify that a dentry is below mnt.mnt_root
631 *
632 * Rename can sometimes move a file or directory outside of a bind
633 * mount, path_connected allows those cases to be detected.
634 */
635static bool path_connected(struct vfsmount *mnt, struct dentry *dentry)
636{
637 struct super_block *sb = mnt->mnt_sb;
638
639 /* Bind mounts can have disconnected paths */
640 if (mnt->mnt_root == sb->s_root)
641 return true;
642
643 return is_subdir(dentry, mnt->mnt_root);
644}
645
646static void drop_links(struct nameidata *nd)
647{
648 int i = nd->depth;
649 while (i--) {
650 struct saved *last = nd->stack + i;
651 do_delayed_call(&last->done);
652 clear_delayed_call(&last->done);
653 }
654}
655
656static void terminate_walk(struct nameidata *nd)
657{
658 drop_links(nd);
659 if (!(nd->flags & LOOKUP_RCU)) {
660 int i;
661 path_put(&nd->path);
662 for (i = 0; i < nd->depth; i++)
663 path_put(&nd->stack[i].link);
664 if (nd->state & ND_ROOT_GRABBED) {
665 path_put(&nd->root);
666 nd->state &= ~ND_ROOT_GRABBED;
667 }
668 } else {
669 nd->flags &= ~LOOKUP_RCU;
670 rcu_read_unlock();
671 }
672 nd->depth = 0;
673 nd->path.mnt = NULL;
674 nd->path.dentry = NULL;
675}
676
677/* path_put is needed afterwards regardless of success or failure */
678static bool __legitimize_path(struct path *path, unsigned seq, unsigned mseq)
679{
680 int res = __legitimize_mnt(path->mnt, mseq);
681 if (unlikely(res)) {
682 if (res > 0)
683 path->mnt = NULL;
684 path->dentry = NULL;
685 return false;
686 }
687 if (unlikely(!lockref_get_not_dead(&path->dentry->d_lockref))) {
688 path->dentry = NULL;
689 return false;
690 }
691 return !read_seqcount_retry(&path->dentry->d_seq, seq);
692}
693
694static inline bool legitimize_path(struct nameidata *nd,
695 struct path *path, unsigned seq)
696{
697 return __legitimize_path(path, seq, nd->m_seq);
698}
699
700static bool legitimize_links(struct nameidata *nd)
701{
702 int i;
703 if (unlikely(nd->flags & LOOKUP_CACHED)) {
704 drop_links(nd);
705 nd->depth = 0;
706 return false;
707 }
708 for (i = 0; i < nd->depth; i++) {
709 struct saved *last = nd->stack + i;
710 if (unlikely(!legitimize_path(nd, &last->link, last->seq))) {
711 drop_links(nd);
712 nd->depth = i + 1;
713 return false;
714 }
715 }
716 return true;
717}
718
719static bool legitimize_root(struct nameidata *nd)
720{
721 /*
722 * For scoped-lookups (where nd->root has been zeroed), we need to
723 * restart the whole lookup from scratch -- because set_root() is wrong
724 * for these lookups (nd->dfd is the root, not the filesystem root).
725 */
726 if (!nd->root.mnt && (nd->flags & LOOKUP_IS_SCOPED))
727 return false;
728 /* Nothing to do if nd->root is zero or is managed by the VFS user. */
729 if (!nd->root.mnt || (nd->state & ND_ROOT_PRESET))
730 return true;
731 nd->state |= ND_ROOT_GRABBED;
732 return legitimize_path(nd, &nd->root, nd->root_seq);
733}
734
735/*
736 * Path walking has 2 modes, rcu-walk and ref-walk (see
737 * Documentation/filesystems/path-lookup.txt). In situations when we can't
738 * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
739 * normal reference counts on dentries and vfsmounts to transition to ref-walk
740 * mode. Refcounts are grabbed at the last known good point before rcu-walk
741 * got stuck, so ref-walk may continue from there. If this is not successful
742 * (eg. a seqcount has changed), then failure is returned and it's up to caller
743 * to restart the path walk from the beginning in ref-walk mode.
744 */
745
746/**
747 * try_to_unlazy - try to switch to ref-walk mode.
748 * @nd: nameidata pathwalk data
749 * Returns: true on success, false on failure
750 *
751 * try_to_unlazy attempts to legitimize the current nd->path and nd->root
752 * for ref-walk mode.
753 * Must be called from rcu-walk context.
754 * Nothing should touch nameidata between try_to_unlazy() failure and
755 * terminate_walk().
756 */
757static bool try_to_unlazy(struct nameidata *nd)
758{
759 struct dentry *parent = nd->path.dentry;
760
761 BUG_ON(!(nd->flags & LOOKUP_RCU));
762
763 nd->flags &= ~LOOKUP_RCU;
764 if (unlikely(!legitimize_links(nd)))
765 goto out1;
766 if (unlikely(!legitimize_path(nd, &nd->path, nd->seq)))
767 goto out;
768 if (unlikely(!legitimize_root(nd)))
769 goto out;
770 rcu_read_unlock();
771 BUG_ON(nd->inode != parent->d_inode);
772 return true;
773
774out1:
775 nd->path.mnt = NULL;
776 nd->path.dentry = NULL;
777out:
778 rcu_read_unlock();
779 return false;
780}
781
782/**
783 * try_to_unlazy_next - try to switch to ref-walk mode.
784 * @nd: nameidata pathwalk data
785 * @dentry: next dentry to step into
786 * @seq: seq number to check @dentry against
787 * Returns: true on success, false on failure
788 *
789 * Similar to to try_to_unlazy(), but here we have the next dentry already
790 * picked by rcu-walk and want to legitimize that in addition to the current
791 * nd->path and nd->root for ref-walk mode. Must be called from rcu-walk context.
792 * Nothing should touch nameidata between try_to_unlazy_next() failure and
793 * terminate_walk().
794 */
795static bool try_to_unlazy_next(struct nameidata *nd, struct dentry *dentry, unsigned seq)
796{
797 BUG_ON(!(nd->flags & LOOKUP_RCU));
798
799 nd->flags &= ~LOOKUP_RCU;
800 if (unlikely(!legitimize_links(nd)))
801 goto out2;
802 if (unlikely(!legitimize_mnt(nd->path.mnt, nd->m_seq)))
803 goto out2;
804 if (unlikely(!lockref_get_not_dead(&nd->path.dentry->d_lockref)))
805 goto out1;
806
807 /*
808 * We need to move both the parent and the dentry from the RCU domain
809 * to be properly refcounted. And the sequence number in the dentry
810 * validates *both* dentry counters, since we checked the sequence
811 * number of the parent after we got the child sequence number. So we
812 * know the parent must still be valid if the child sequence number is
813 */
814 if (unlikely(!lockref_get_not_dead(&dentry->d_lockref)))
815 goto out;
816 if (unlikely(read_seqcount_retry(&dentry->d_seq, seq)))
817 goto out_dput;
818 /*
819 * Sequence counts matched. Now make sure that the root is
820 * still valid and get it if required.
821 */
822 if (unlikely(!legitimize_root(nd)))
823 goto out_dput;
824 rcu_read_unlock();
825 return true;
826
827out2:
828 nd->path.mnt = NULL;
829out1:
830 nd->path.dentry = NULL;
831out:
832 rcu_read_unlock();
833 return false;
834out_dput:
835 rcu_read_unlock();
836 dput(dentry);
837 return false;
838}
839
840static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
841{
842 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE))
843 return dentry->d_op->d_revalidate(dentry, flags);
844 else
845 return 1;
846}
847
848/**
849 * complete_walk - successful completion of path walk
850 * @nd: pointer nameidata
851 *
852 * If we had been in RCU mode, drop out of it and legitimize nd->path.
853 * Revalidate the final result, unless we'd already done that during
854 * the path walk or the filesystem doesn't ask for it. Return 0 on
855 * success, -error on failure. In case of failure caller does not
856 * need to drop nd->path.
857 */
858static int complete_walk(struct nameidata *nd)
859{
860 struct dentry *dentry = nd->path.dentry;
861 int status;
862
863 if (nd->flags & LOOKUP_RCU) {
864 /*
865 * We don't want to zero nd->root for scoped-lookups or
866 * externally-managed nd->root.
867 */
868 if (!(nd->state & ND_ROOT_PRESET))
869 if (!(nd->flags & LOOKUP_IS_SCOPED))
870 nd->root.mnt = NULL;
871 nd->flags &= ~LOOKUP_CACHED;
872 if (!try_to_unlazy(nd))
873 return -ECHILD;
874 }
875
876 if (unlikely(nd->flags & LOOKUP_IS_SCOPED)) {
877 /*
878 * While the guarantee of LOOKUP_IS_SCOPED is (roughly) "don't
879 * ever step outside the root during lookup" and should already
880 * be guaranteed by the rest of namei, we want to avoid a namei
881 * BUG resulting in userspace being given a path that was not
882 * scoped within the root at some point during the lookup.
883 *
884 * So, do a final sanity-check to make sure that in the
885 * worst-case scenario (a complete bypass of LOOKUP_IS_SCOPED)
886 * we won't silently return an fd completely outside of the
887 * requested root to userspace.
888 *
889 * Userspace could move the path outside the root after this
890 * check, but as discussed elsewhere this is not a concern (the
891 * resolved file was inside the root at some point).
892 */
893 if (!path_is_under(&nd->path, &nd->root))
894 return -EXDEV;
895 }
896
897 if (likely(!(nd->state & ND_JUMPED)))
898 return 0;
899
900 if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE)))
901 return 0;
902
903 status = dentry->d_op->d_weak_revalidate(dentry, nd->flags);
904 if (status > 0)
905 return 0;
906
907 if (!status)
908 status = -ESTALE;
909
910 return status;
911}
912
913static int set_root(struct nameidata *nd)
914{
915 struct fs_struct *fs = current->fs;
916
917 /*
918 * Jumping to the real root in a scoped-lookup is a BUG in namei, but we
919 * still have to ensure it doesn't happen because it will cause a breakout
920 * from the dirfd.
921 */
922 if (WARN_ON(nd->flags & LOOKUP_IS_SCOPED))
923 return -ENOTRECOVERABLE;
924
925 if (nd->flags & LOOKUP_RCU) {
926 unsigned seq;
927
928 do {
929 seq = read_seqcount_begin(&fs->seq);
930 nd->root = fs->root;
931 nd->root_seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
932 } while (read_seqcount_retry(&fs->seq, seq));
933 } else {
934 get_fs_root(fs, &nd->root);
935 nd->state |= ND_ROOT_GRABBED;
936 }
937 return 0;
938}
939
940static int nd_jump_root(struct nameidata *nd)
941{
942 if (unlikely(nd->flags & LOOKUP_BENEATH))
943 return -EXDEV;
944 if (unlikely(nd->flags & LOOKUP_NO_XDEV)) {
945 /* Absolute path arguments to path_init() are allowed. */
946 if (nd->path.mnt != NULL && nd->path.mnt != nd->root.mnt)
947 return -EXDEV;
948 }
949 if (!nd->root.mnt) {
950 int error = set_root(nd);
951 if (error)
952 return error;
953 }
954 if (nd->flags & LOOKUP_RCU) {
955 struct dentry *d;
956 nd->path = nd->root;
957 d = nd->path.dentry;
958 nd->inode = d->d_inode;
959 nd->seq = nd->root_seq;
960 if (unlikely(read_seqcount_retry(&d->d_seq, nd->seq)))
961 return -ECHILD;
962 } else {
963 path_put(&nd->path);
964 nd->path = nd->root;
965 path_get(&nd->path);
966 nd->inode = nd->path.dentry->d_inode;
967 }
968 nd->state |= ND_JUMPED;
969 return 0;
970}
971
972/*
973 * Helper to directly jump to a known parsed path from ->get_link,
974 * caller must have taken a reference to path beforehand.
975 */
976int nd_jump_link(struct path *path)
977{
978 int error = -ELOOP;
979 struct nameidata *nd = current->nameidata;
980
981 if (unlikely(nd->flags & LOOKUP_NO_MAGICLINKS))
982 goto err;
983
984 error = -EXDEV;
985 if (unlikely(nd->flags & LOOKUP_NO_XDEV)) {
986 if (nd->path.mnt != path->mnt)
987 goto err;
988 }
989 /* Not currently safe for scoped-lookups. */
990 if (unlikely(nd->flags & LOOKUP_IS_SCOPED))
991 goto err;
992
993 path_put(&nd->path);
994 nd->path = *path;
995 nd->inode = nd->path.dentry->d_inode;
996 nd->state |= ND_JUMPED;
997 return 0;
998
999err:
1000 path_put(path);
1001 return error;
1002}
1003
1004static inline void put_link(struct nameidata *nd)
1005{
1006 struct saved *last = nd->stack + --nd->depth;
1007 do_delayed_call(&last->done);
1008 if (!(nd->flags & LOOKUP_RCU))
1009 path_put(&last->link);
1010}
1011
1012int sysctl_protected_symlinks __read_mostly = 0;
1013int sysctl_protected_hardlinks __read_mostly = 0;
1014int sysctl_protected_fifos __read_mostly;
1015int sysctl_protected_regular __read_mostly;
1016
1017/**
1018 * may_follow_link - Check symlink following for unsafe situations
1019 * @nd: nameidata pathwalk data
1020 *
1021 * In the case of the sysctl_protected_symlinks sysctl being enabled,
1022 * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
1023 * in a sticky world-writable directory. This is to protect privileged
1024 * processes from failing races against path names that may change out
1025 * from under them by way of other users creating malicious symlinks.
1026 * It will permit symlinks to be followed only when outside a sticky
1027 * world-writable directory, or when the uid of the symlink and follower
1028 * match, or when the directory owner matches the symlink's owner.
1029 *
1030 * Returns 0 if following the symlink is allowed, -ve on error.
1031 */
1032static inline int may_follow_link(struct nameidata *nd, const struct inode *inode)
1033{
1034 struct user_namespace *mnt_userns;
1035 kuid_t i_uid;
1036
1037 if (!sysctl_protected_symlinks)
1038 return 0;
1039
1040 mnt_userns = mnt_user_ns(nd->path.mnt);
1041 i_uid = i_uid_into_mnt(mnt_userns, inode);
1042 /* Allowed if owner and follower match. */
1043 if (uid_eq(current_cred()->fsuid, i_uid))
1044 return 0;
1045
1046 /* Allowed if parent directory not sticky and world-writable. */
1047 if ((nd->dir_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH))
1048 return 0;
1049
1050 /* Allowed if parent directory and link owner match. */
1051 if (uid_valid(nd->dir_uid) && uid_eq(nd->dir_uid, i_uid))
1052 return 0;
1053
1054 if (nd->flags & LOOKUP_RCU)
1055 return -ECHILD;
1056
1057 audit_inode(nd->name, nd->stack[0].link.dentry, 0);
1058 audit_log_path_denied(AUDIT_ANOM_LINK, "follow_link");
1059 return -EACCES;
1060}
1061
1062/**
1063 * safe_hardlink_source - Check for safe hardlink conditions
1064 * @mnt_userns: user namespace of the mount the inode was found from
1065 * @inode: the source inode to hardlink from
1066 *
1067 * Return false if at least one of the following conditions:
1068 * - inode is not a regular file
1069 * - inode is setuid
1070 * - inode is setgid and group-exec
1071 * - access failure for read and write
1072 *
1073 * Otherwise returns true.
1074 */
1075static bool safe_hardlink_source(struct user_namespace *mnt_userns,
1076 struct inode *inode)
1077{
1078 umode_t mode = inode->i_mode;
1079
1080 /* Special files should not get pinned to the filesystem. */
1081 if (!S_ISREG(mode))
1082 return false;
1083
1084 /* Setuid files should not get pinned to the filesystem. */
1085 if (mode & S_ISUID)
1086 return false;
1087
1088 /* Executable setgid files should not get pinned to the filesystem. */
1089 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP))
1090 return false;
1091
1092 /* Hardlinking to unreadable or unwritable sources is dangerous. */
1093 if (inode_permission(mnt_userns, inode, MAY_READ | MAY_WRITE))
1094 return false;
1095
1096 return true;
1097}
1098
1099/**
1100 * may_linkat - Check permissions for creating a hardlink
1101 * @mnt_userns: user namespace of the mount the inode was found from
1102 * @link: the source to hardlink from
1103 *
1104 * Block hardlink when all of:
1105 * - sysctl_protected_hardlinks enabled
1106 * - fsuid does not match inode
1107 * - hardlink source is unsafe (see safe_hardlink_source() above)
1108 * - not CAP_FOWNER in a namespace with the inode owner uid mapped
1109 *
1110 * If the inode has been found through an idmapped mount the user namespace of
1111 * the vfsmount must be passed through @mnt_userns. This function will then take
1112 * care to map the inode according to @mnt_userns before checking permissions.
1113 * On non-idmapped mounts or if permission checking is to be performed on the
1114 * raw inode simply passs init_user_ns.
1115 *
1116 * Returns 0 if successful, -ve on error.
1117 */
1118int may_linkat(struct user_namespace *mnt_userns, struct path *link)
1119{
1120 struct inode *inode = link->dentry->d_inode;
1121
1122 /* Inode writeback is not safe when the uid or gid are invalid. */
1123 if (!uid_valid(i_uid_into_mnt(mnt_userns, inode)) ||
1124 !gid_valid(i_gid_into_mnt(mnt_userns, inode)))
1125 return -EOVERFLOW;
1126
1127 if (!sysctl_protected_hardlinks)
1128 return 0;
1129
1130 /* Source inode owner (or CAP_FOWNER) can hardlink all they like,
1131 * otherwise, it must be a safe source.
1132 */
1133 if (safe_hardlink_source(mnt_userns, inode) ||
1134 inode_owner_or_capable(mnt_userns, inode))
1135 return 0;
1136
1137 audit_log_path_denied(AUDIT_ANOM_LINK, "linkat");
1138 return -EPERM;
1139}
1140
1141/**
1142 * may_create_in_sticky - Check whether an O_CREAT open in a sticky directory
1143 * should be allowed, or not, on files that already
1144 * exist.
1145 * @mnt_userns: user namespace of the mount the inode was found from
1146 * @nd: nameidata pathwalk data
1147 * @inode: the inode of the file to open
1148 *
1149 * Block an O_CREAT open of a FIFO (or a regular file) when:
1150 * - sysctl_protected_fifos (or sysctl_protected_regular) is enabled
1151 * - the file already exists
1152 * - we are in a sticky directory
1153 * - we don't own the file
1154 * - the owner of the directory doesn't own the file
1155 * - the directory is world writable
1156 * If the sysctl_protected_fifos (or sysctl_protected_regular) is set to 2
1157 * the directory doesn't have to be world writable: being group writable will
1158 * be enough.
1159 *
1160 * If the inode has been found through an idmapped mount the user namespace of
1161 * the vfsmount must be passed through @mnt_userns. This function will then take
1162 * care to map the inode according to @mnt_userns before checking permissions.
1163 * On non-idmapped mounts or if permission checking is to be performed on the
1164 * raw inode simply passs init_user_ns.
1165 *
1166 * Returns 0 if the open is allowed, -ve on error.
1167 */
1168static int may_create_in_sticky(struct user_namespace *mnt_userns,
1169 struct nameidata *nd, struct inode *const inode)
1170{
1171 umode_t dir_mode = nd->dir_mode;
1172 kuid_t dir_uid = nd->dir_uid;
1173
1174 if ((!sysctl_protected_fifos && S_ISFIFO(inode->i_mode)) ||
1175 (!sysctl_protected_regular && S_ISREG(inode->i_mode)) ||
1176 likely(!(dir_mode & S_ISVTX)) ||
1177 uid_eq(i_uid_into_mnt(mnt_userns, inode), dir_uid) ||
1178 uid_eq(current_fsuid(), i_uid_into_mnt(mnt_userns, inode)))
1179 return 0;
1180
1181 if (likely(dir_mode & 0002) ||
1182 (dir_mode & 0020 &&
1183 ((sysctl_protected_fifos >= 2 && S_ISFIFO(inode->i_mode)) ||
1184 (sysctl_protected_regular >= 2 && S_ISREG(inode->i_mode))))) {
1185 const char *operation = S_ISFIFO(inode->i_mode) ?
1186 "sticky_create_fifo" :
1187 "sticky_create_regular";
1188 audit_log_path_denied(AUDIT_ANOM_CREAT, operation);
1189 return -EACCES;
1190 }
1191 return 0;
1192}
1193
1194/*
1195 * follow_up - Find the mountpoint of path's vfsmount
1196 *
1197 * Given a path, find the mountpoint of its source file system.
1198 * Replace @path with the path of the mountpoint in the parent mount.
1199 * Up is towards /.
1200 *
1201 * Return 1 if we went up a level and 0 if we were already at the
1202 * root.
1203 */
1204int follow_up(struct path *path)
1205{
1206 struct mount *mnt = real_mount(path->mnt);
1207 struct mount *parent;
1208 struct dentry *mountpoint;
1209
1210 read_seqlock_excl(&mount_lock);
1211 parent = mnt->mnt_parent;
1212 if (parent == mnt) {
1213 read_sequnlock_excl(&mount_lock);
1214 return 0;
1215 }
1216 mntget(&parent->mnt);
1217 mountpoint = dget(mnt->mnt_mountpoint);
1218 read_sequnlock_excl(&mount_lock);
1219 dput(path->dentry);
1220 path->dentry = mountpoint;
1221 mntput(path->mnt);
1222 path->mnt = &parent->mnt;
1223 return 1;
1224}
1225EXPORT_SYMBOL(follow_up);
1226
1227static bool choose_mountpoint_rcu(struct mount *m, const struct path *root,
1228 struct path *path, unsigned *seqp)
1229{
1230 while (mnt_has_parent(m)) {
1231 struct dentry *mountpoint = m->mnt_mountpoint;
1232
1233 m = m->mnt_parent;
1234 if (unlikely(root->dentry == mountpoint &&
1235 root->mnt == &m->mnt))
1236 break;
1237 if (mountpoint != m->mnt.mnt_root) {
1238 path->mnt = &m->mnt;
1239 path->dentry = mountpoint;
1240 *seqp = read_seqcount_begin(&mountpoint->d_seq);
1241 return true;
1242 }
1243 }
1244 return false;
1245}
1246
1247static bool choose_mountpoint(struct mount *m, const struct path *root,
1248 struct path *path)
1249{
1250 bool found;
1251
1252 rcu_read_lock();
1253 while (1) {
1254 unsigned seq, mseq = read_seqbegin(&mount_lock);
1255
1256 found = choose_mountpoint_rcu(m, root, path, &seq);
1257 if (unlikely(!found)) {
1258 if (!read_seqretry(&mount_lock, mseq))
1259 break;
1260 } else {
1261 if (likely(__legitimize_path(path, seq, mseq)))
1262 break;
1263 rcu_read_unlock();
1264 path_put(path);
1265 rcu_read_lock();
1266 }
1267 }
1268 rcu_read_unlock();
1269 return found;
1270}
1271
1272/*
1273 * Perform an automount
1274 * - return -EISDIR to tell follow_managed() to stop and return the path we
1275 * were called with.
1276 */
1277static int follow_automount(struct path *path, int *count, unsigned lookup_flags)
1278{
1279 struct dentry *dentry = path->dentry;
1280
1281 /* We don't want to mount if someone's just doing a stat -
1282 * unless they're stat'ing a directory and appended a '/' to
1283 * the name.
1284 *
1285 * We do, however, want to mount if someone wants to open or
1286 * create a file of any type under the mountpoint, wants to
1287 * traverse through the mountpoint or wants to open the
1288 * mounted directory. Also, autofs may mark negative dentries
1289 * as being automount points. These will need the attentions
1290 * of the daemon to instantiate them before they can be used.
1291 */
1292 if (!(lookup_flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
1293 LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
1294 dentry->d_inode)
1295 return -EISDIR;
1296
1297 if (count && (*count)++ >= MAXSYMLINKS)
1298 return -ELOOP;
1299
1300 return finish_automount(dentry->d_op->d_automount(path), path);
1301}
1302
1303/*
1304 * mount traversal - out-of-line part. One note on ->d_flags accesses -
1305 * dentries are pinned but not locked here, so negative dentry can go
1306 * positive right under us. Use of smp_load_acquire() provides a barrier
1307 * sufficient for ->d_inode and ->d_flags consistency.
1308 */
1309static int __traverse_mounts(struct path *path, unsigned flags, bool *jumped,
1310 int *count, unsigned lookup_flags)
1311{
1312 struct vfsmount *mnt = path->mnt;
1313 bool need_mntput = false;
1314 int ret = 0;
1315
1316 while (flags & DCACHE_MANAGED_DENTRY) {
1317 /* Allow the filesystem to manage the transit without i_mutex
1318 * being held. */
1319 if (flags & DCACHE_MANAGE_TRANSIT) {
1320 ret = path->dentry->d_op->d_manage(path, false);
1321 flags = smp_load_acquire(&path->dentry->d_flags);
1322 if (ret < 0)
1323 break;
1324 }
1325
1326 if (flags & DCACHE_MOUNTED) { // something's mounted on it..
1327 struct vfsmount *mounted = lookup_mnt(path);
1328 if (mounted) { // ... in our namespace
1329 dput(path->dentry);
1330 if (need_mntput)
1331 mntput(path->mnt);
1332 path->mnt = mounted;
1333 path->dentry = dget(mounted->mnt_root);
1334 // here we know it's positive
1335 flags = path->dentry->d_flags;
1336 need_mntput = true;
1337 continue;
1338 }
1339 }
1340
1341 if (!(flags & DCACHE_NEED_AUTOMOUNT))
1342 break;
1343
1344 // uncovered automount point
1345 ret = follow_automount(path, count, lookup_flags);
1346 flags = smp_load_acquire(&path->dentry->d_flags);
1347 if (ret < 0)
1348 break;
1349 }
1350
1351 if (ret == -EISDIR)
1352 ret = 0;
1353 // possible if you race with several mount --move
1354 if (need_mntput && path->mnt == mnt)
1355 mntput(path->mnt);
1356 if (!ret && unlikely(d_flags_negative(flags)))
1357 ret = -ENOENT;
1358 *jumped = need_mntput;
1359 return ret;
1360}
1361
1362static inline int traverse_mounts(struct path *path, bool *jumped,
1363 int *count, unsigned lookup_flags)
1364{
1365 unsigned flags = smp_load_acquire(&path->dentry->d_flags);
1366
1367 /* fastpath */
1368 if (likely(!(flags & DCACHE_MANAGED_DENTRY))) {
1369 *jumped = false;
1370 if (unlikely(d_flags_negative(flags)))
1371 return -ENOENT;
1372 return 0;
1373 }
1374 return __traverse_mounts(path, flags, jumped, count, lookup_flags);
1375}
1376
1377int follow_down_one(struct path *path)
1378{
1379 struct vfsmount *mounted;
1380
1381 mounted = lookup_mnt(path);
1382 if (mounted) {
1383 dput(path->dentry);
1384 mntput(path->mnt);
1385 path->mnt = mounted;
1386 path->dentry = dget(mounted->mnt_root);
1387 return 1;
1388 }
1389 return 0;
1390}
1391EXPORT_SYMBOL(follow_down_one);
1392
1393/*
1394 * Follow down to the covering mount currently visible to userspace. At each
1395 * point, the filesystem owning that dentry may be queried as to whether the
1396 * caller is permitted to proceed or not.
1397 */
1398int follow_down(struct path *path)
1399{
1400 struct vfsmount *mnt = path->mnt;
1401 bool jumped;
1402 int ret = traverse_mounts(path, &jumped, NULL, 0);
1403
1404 if (path->mnt != mnt)
1405 mntput(mnt);
1406 return ret;
1407}
1408EXPORT_SYMBOL(follow_down);
1409
1410/*
1411 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
1412 * we meet a managed dentry that would need blocking.
1413 */
1414static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
1415 struct inode **inode, unsigned *seqp)
1416{
1417 struct dentry *dentry = path->dentry;
1418 unsigned int flags = dentry->d_flags;
1419
1420 if (likely(!(flags & DCACHE_MANAGED_DENTRY)))
1421 return true;
1422
1423 if (unlikely(nd->flags & LOOKUP_NO_XDEV))
1424 return false;
1425
1426 for (;;) {
1427 /*
1428 * Don't forget we might have a non-mountpoint managed dentry
1429 * that wants to block transit.
1430 */
1431 if (unlikely(flags & DCACHE_MANAGE_TRANSIT)) {
1432 int res = dentry->d_op->d_manage(path, true);
1433 if (res)
1434 return res == -EISDIR;
1435 flags = dentry->d_flags;
1436 }
1437
1438 if (flags & DCACHE_MOUNTED) {
1439 struct mount *mounted = __lookup_mnt(path->mnt, dentry);
1440 if (mounted) {
1441 path->mnt = &mounted->mnt;
1442 dentry = path->dentry = mounted->mnt.mnt_root;
1443 nd->state |= ND_JUMPED;
1444 *seqp = read_seqcount_begin(&dentry->d_seq);
1445 *inode = dentry->d_inode;
1446 /*
1447 * We don't need to re-check ->d_seq after this
1448 * ->d_inode read - there will be an RCU delay
1449 * between mount hash removal and ->mnt_root
1450 * becoming unpinned.
1451 */
1452 flags = dentry->d_flags;
1453 continue;
1454 }
1455 if (read_seqretry(&mount_lock, nd->m_seq))
1456 return false;
1457 }
1458 return !(flags & DCACHE_NEED_AUTOMOUNT);
1459 }
1460}
1461
1462static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry,
1463 struct path *path, struct inode **inode,
1464 unsigned int *seqp)
1465{
1466 bool jumped;
1467 int ret;
1468
1469 path->mnt = nd->path.mnt;
1470 path->dentry = dentry;
1471 if (nd->flags & LOOKUP_RCU) {
1472 unsigned int seq = *seqp;
1473 if (unlikely(!*inode))
1474 return -ENOENT;
1475 if (likely(__follow_mount_rcu(nd, path, inode, seqp)))
1476 return 0;
1477 if (!try_to_unlazy_next(nd, dentry, seq))
1478 return -ECHILD;
1479 // *path might've been clobbered by __follow_mount_rcu()
1480 path->mnt = nd->path.mnt;
1481 path->dentry = dentry;
1482 }
1483 ret = traverse_mounts(path, &jumped, &nd->total_link_count, nd->flags);
1484 if (jumped) {
1485 if (unlikely(nd->flags & LOOKUP_NO_XDEV))
1486 ret = -EXDEV;
1487 else
1488 nd->state |= ND_JUMPED;
1489 }
1490 if (unlikely(ret)) {
1491 dput(path->dentry);
1492 if (path->mnt != nd->path.mnt)
1493 mntput(path->mnt);
1494 } else {
1495 *inode = d_backing_inode(path->dentry);
1496 *seqp = 0; /* out of RCU mode, so the value doesn't matter */
1497 }
1498 return ret;
1499}
1500
1501/*
1502 * This looks up the name in dcache and possibly revalidates the found dentry.
1503 * NULL is returned if the dentry does not exist in the cache.
1504 */
1505static struct dentry *lookup_dcache(const struct qstr *name,
1506 struct dentry *dir,
1507 unsigned int flags)
1508{
1509 struct dentry *dentry = d_lookup(dir, name);
1510 if (dentry) {
1511 int error = d_revalidate(dentry, flags);
1512 if (unlikely(error <= 0)) {
1513 if (!error)
1514 d_invalidate(dentry);
1515 dput(dentry);
1516 return ERR_PTR(error);
1517 }
1518 }
1519 return dentry;
1520}
1521
1522/*
1523 * Parent directory has inode locked exclusive. This is one
1524 * and only case when ->lookup() gets called on non in-lookup
1525 * dentries - as the matter of fact, this only gets called
1526 * when directory is guaranteed to have no in-lookup children
1527 * at all.
1528 */
1529static struct dentry *__lookup_hash(const struct qstr *name,
1530 struct dentry *base, unsigned int flags)
1531{
1532 struct dentry *dentry = lookup_dcache(name, base, flags);
1533 struct dentry *old;
1534 struct inode *dir = base->d_inode;
1535
1536 if (dentry)
1537 return dentry;
1538
1539 /* Don't create child dentry for a dead directory. */
1540 if (unlikely(IS_DEADDIR(dir)))
1541 return ERR_PTR(-ENOENT);
1542
1543 dentry = d_alloc(base, name);
1544 if (unlikely(!dentry))
1545 return ERR_PTR(-ENOMEM);
1546
1547 old = dir->i_op->lookup(dir, dentry, flags);
1548 if (unlikely(old)) {
1549 dput(dentry);
1550 dentry = old;
1551 }
1552 return dentry;
1553}
1554
1555static struct dentry *lookup_fast(struct nameidata *nd,
1556 struct inode **inode,
1557 unsigned *seqp)
1558{
1559 struct dentry *dentry, *parent = nd->path.dentry;
1560 int status = 1;
1561
1562 /*
1563 * Rename seqlock is not required here because in the off chance
1564 * of a false negative due to a concurrent rename, the caller is
1565 * going to fall back to non-racy lookup.
1566 */
1567 if (nd->flags & LOOKUP_RCU) {
1568 unsigned seq;
1569 dentry = __d_lookup_rcu(parent, &nd->last, &seq);
1570 if (unlikely(!dentry)) {
1571 if (!try_to_unlazy(nd))
1572 return ERR_PTR(-ECHILD);
1573 return NULL;
1574 }
1575
1576 /*
1577 * This sequence count validates that the inode matches
1578 * the dentry name information from lookup.
1579 */
1580 *inode = d_backing_inode(dentry);
1581 if (unlikely(read_seqcount_retry(&dentry->d_seq, seq)))
1582 return ERR_PTR(-ECHILD);
1583
1584 /*
1585 * This sequence count validates that the parent had no
1586 * changes while we did the lookup of the dentry above.
1587 *
1588 * The memory barrier in read_seqcount_begin of child is
1589 * enough, we can use __read_seqcount_retry here.
1590 */
1591 if (unlikely(__read_seqcount_retry(&parent->d_seq, nd->seq)))
1592 return ERR_PTR(-ECHILD);
1593
1594 *seqp = seq;
1595 status = d_revalidate(dentry, nd->flags);
1596 if (likely(status > 0))
1597 return dentry;
1598 if (!try_to_unlazy_next(nd, dentry, seq))
1599 return ERR_PTR(-ECHILD);
1600 if (status == -ECHILD)
1601 /* we'd been told to redo it in non-rcu mode */
1602 status = d_revalidate(dentry, nd->flags);
1603 } else {
1604 dentry = __d_lookup(parent, &nd->last);
1605 if (unlikely(!dentry))
1606 return NULL;
1607 status = d_revalidate(dentry, nd->flags);
1608 }
1609 if (unlikely(status <= 0)) {
1610 if (!status)
1611 d_invalidate(dentry);
1612 dput(dentry);
1613 return ERR_PTR(status);
1614 }
1615 return dentry;
1616}
1617
1618/* Fast lookup failed, do it the slow way */
1619static struct dentry *__lookup_slow(const struct qstr *name,
1620 struct dentry *dir,
1621 unsigned int flags)
1622{
1623 struct dentry *dentry, *old;
1624 struct inode *inode = dir->d_inode;
1625 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
1626
1627 /* Don't go there if it's already dead */
1628 if (unlikely(IS_DEADDIR(inode)))
1629 return ERR_PTR(-ENOENT);
1630again:
1631 dentry = d_alloc_parallel(dir, name, &wq);
1632 if (IS_ERR(dentry))
1633 return dentry;
1634 if (unlikely(!d_in_lookup(dentry))) {
1635 int error = d_revalidate(dentry, flags);
1636 if (unlikely(error <= 0)) {
1637 if (!error) {
1638 d_invalidate(dentry);
1639 dput(dentry);
1640 goto again;
1641 }
1642 dput(dentry);
1643 dentry = ERR_PTR(error);
1644 }
1645 } else {
1646 old = inode->i_op->lookup(inode, dentry, flags);
1647 d_lookup_done(dentry);
1648 if (unlikely(old)) {
1649 dput(dentry);
1650 dentry = old;
1651 }
1652 }
1653 return dentry;
1654}
1655
1656static struct dentry *lookup_slow(const struct qstr *name,
1657 struct dentry *dir,
1658 unsigned int flags)
1659{
1660 struct inode *inode = dir->d_inode;
1661 struct dentry *res;
1662 inode_lock_shared(inode);
1663 res = __lookup_slow(name, dir, flags);
1664 inode_unlock_shared(inode);
1665 return res;
1666}
1667
1668static inline int may_lookup(struct user_namespace *mnt_userns,
1669 struct nameidata *nd)
1670{
1671 if (nd->flags & LOOKUP_RCU) {
1672 int err = inode_permission(mnt_userns, nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
1673 if (err != -ECHILD || !try_to_unlazy(nd))
1674 return err;
1675 }
1676 return inode_permission(mnt_userns, nd->inode, MAY_EXEC);
1677}
1678
1679static int reserve_stack(struct nameidata *nd, struct path *link, unsigned seq)
1680{
1681 if (unlikely(nd->total_link_count++ >= MAXSYMLINKS))
1682 return -ELOOP;
1683
1684 if (likely(nd->depth != EMBEDDED_LEVELS))
1685 return 0;
1686 if (likely(nd->stack != nd->internal))
1687 return 0;
1688 if (likely(nd_alloc_stack(nd)))
1689 return 0;
1690
1691 if (nd->flags & LOOKUP_RCU) {
1692 // we need to grab link before we do unlazy. And we can't skip
1693 // unlazy even if we fail to grab the link - cleanup needs it
1694 bool grabbed_link = legitimize_path(nd, link, seq);
1695
1696 if (!try_to_unlazy(nd) != 0 || !grabbed_link)
1697 return -ECHILD;
1698
1699 if (nd_alloc_stack(nd))
1700 return 0;
1701 }
1702 return -ENOMEM;
1703}
1704
1705enum {WALK_TRAILING = 1, WALK_MORE = 2, WALK_NOFOLLOW = 4};
1706
1707static const char *pick_link(struct nameidata *nd, struct path *link,
1708 struct inode *inode, unsigned seq, int flags)
1709{
1710 struct saved *last;
1711 const char *res;
1712 int error = reserve_stack(nd, link, seq);
1713
1714 if (unlikely(error)) {
1715 if (!(nd->flags & LOOKUP_RCU))
1716 path_put(link);
1717 return ERR_PTR(error);
1718 }
1719 last = nd->stack + nd->depth++;
1720 last->link = *link;
1721 clear_delayed_call(&last->done);
1722 last->seq = seq;
1723
1724 if (flags & WALK_TRAILING) {
1725 error = may_follow_link(nd, inode);
1726 if (unlikely(error))
1727 return ERR_PTR(error);
1728 }
1729
1730 if (unlikely(nd->flags & LOOKUP_NO_SYMLINKS) ||
1731 unlikely(link->mnt->mnt_flags & MNT_NOSYMFOLLOW))
1732 return ERR_PTR(-ELOOP);
1733
1734 if (!(nd->flags & LOOKUP_RCU)) {
1735 touch_atime(&last->link);
1736 cond_resched();
1737 } else if (atime_needs_update(&last->link, inode)) {
1738 if (!try_to_unlazy(nd))
1739 return ERR_PTR(-ECHILD);
1740 touch_atime(&last->link);
1741 }
1742
1743 error = security_inode_follow_link(link->dentry, inode,
1744 nd->flags & LOOKUP_RCU);
1745 if (unlikely(error))
1746 return ERR_PTR(error);
1747
1748 res = READ_ONCE(inode->i_link);
1749 if (!res) {
1750 const char * (*get)(struct dentry *, struct inode *,
1751 struct delayed_call *);
1752 get = inode->i_op->get_link;
1753 if (nd->flags & LOOKUP_RCU) {
1754 res = get(NULL, inode, &last->done);
1755 if (res == ERR_PTR(-ECHILD) && try_to_unlazy(nd))
1756 res = get(link->dentry, inode, &last->done);
1757 } else {
1758 res = get(link->dentry, inode, &last->done);
1759 }
1760 if (!res)
1761 goto all_done;
1762 if (IS_ERR(res))
1763 return res;
1764 }
1765 if (*res == '/') {
1766 error = nd_jump_root(nd);
1767 if (unlikely(error))
1768 return ERR_PTR(error);
1769 while (unlikely(*++res == '/'))
1770 ;
1771 }
1772 if (*res)
1773 return res;
1774all_done: // pure jump
1775 put_link(nd);
1776 return NULL;
1777}
1778
1779/*
1780 * Do we need to follow links? We _really_ want to be able
1781 * to do this check without having to look at inode->i_op,
1782 * so we keep a cache of "no, this doesn't need follow_link"
1783 * for the common case.
1784 */
1785static const char *step_into(struct nameidata *nd, int flags,
1786 struct dentry *dentry, struct inode *inode, unsigned seq)
1787{
1788 struct path path;
1789 int err = handle_mounts(nd, dentry, &path, &inode, &seq);
1790
1791 if (err < 0)
1792 return ERR_PTR(err);
1793 if (likely(!d_is_symlink(path.dentry)) ||
1794 ((flags & WALK_TRAILING) && !(nd->flags & LOOKUP_FOLLOW)) ||
1795 (flags & WALK_NOFOLLOW)) {
1796 /* not a symlink or should not follow */
1797 if (!(nd->flags & LOOKUP_RCU)) {
1798 dput(nd->path.dentry);
1799 if (nd->path.mnt != path.mnt)
1800 mntput(nd->path.mnt);
1801 }
1802 nd->path = path;
1803 nd->inode = inode;
1804 nd->seq = seq;
1805 return NULL;
1806 }
1807 if (nd->flags & LOOKUP_RCU) {
1808 /* make sure that d_is_symlink above matches inode */
1809 if (read_seqcount_retry(&path.dentry->d_seq, seq))
1810 return ERR_PTR(-ECHILD);
1811 } else {
1812 if (path.mnt == nd->path.mnt)
1813 mntget(path.mnt);
1814 }
1815 return pick_link(nd, &path, inode, seq, flags);
1816}
1817
1818static struct dentry *follow_dotdot_rcu(struct nameidata *nd,
1819 struct inode **inodep,
1820 unsigned *seqp)
1821{
1822 struct dentry *parent, *old;
1823
1824 if (path_equal(&nd->path, &nd->root))
1825 goto in_root;
1826 if (unlikely(nd->path.dentry == nd->path.mnt->mnt_root)) {
1827 struct path path;
1828 unsigned seq;
1829 if (!choose_mountpoint_rcu(real_mount(nd->path.mnt),
1830 &nd->root, &path, &seq))
1831 goto in_root;
1832 if (unlikely(nd->flags & LOOKUP_NO_XDEV))
1833 return ERR_PTR(-ECHILD);
1834 nd->path = path;
1835 nd->inode = path.dentry->d_inode;
1836 nd->seq = seq;
1837 if (unlikely(read_seqretry(&mount_lock, nd->m_seq)))
1838 return ERR_PTR(-ECHILD);
1839 /* we know that mountpoint was pinned */
1840 }
1841 old = nd->path.dentry;
1842 parent = old->d_parent;
1843 *inodep = parent->d_inode;
1844 *seqp = read_seqcount_begin(&parent->d_seq);
1845 if (unlikely(read_seqcount_retry(&old->d_seq, nd->seq)))
1846 return ERR_PTR(-ECHILD);
1847 if (unlikely(!path_connected(nd->path.mnt, parent)))
1848 return ERR_PTR(-ECHILD);
1849 return parent;
1850in_root:
1851 if (unlikely(read_seqretry(&mount_lock, nd->m_seq)))
1852 return ERR_PTR(-ECHILD);
1853 if (unlikely(nd->flags & LOOKUP_BENEATH))
1854 return ERR_PTR(-ECHILD);
1855 return NULL;
1856}
1857
1858static struct dentry *follow_dotdot(struct nameidata *nd,
1859 struct inode **inodep,
1860 unsigned *seqp)
1861{
1862 struct dentry *parent;
1863
1864 if (path_equal(&nd->path, &nd->root))
1865 goto in_root;
1866 if (unlikely(nd->path.dentry == nd->path.mnt->mnt_root)) {
1867 struct path path;
1868
1869 if (!choose_mountpoint(real_mount(nd->path.mnt),
1870 &nd->root, &path))
1871 goto in_root;
1872 path_put(&nd->path);
1873 nd->path = path;
1874 nd->inode = path.dentry->d_inode;
1875 if (unlikely(nd->flags & LOOKUP_NO_XDEV))
1876 return ERR_PTR(-EXDEV);
1877 }
1878 /* rare case of legitimate dget_parent()... */
1879 parent = dget_parent(nd->path.dentry);
1880 if (unlikely(!path_connected(nd->path.mnt, parent))) {
1881 dput(parent);
1882 return ERR_PTR(-ENOENT);
1883 }
1884 *seqp = 0;
1885 *inodep = parent->d_inode;
1886 return parent;
1887
1888in_root:
1889 if (unlikely(nd->flags & LOOKUP_BENEATH))
1890 return ERR_PTR(-EXDEV);
1891 dget(nd->path.dentry);
1892 return NULL;
1893}
1894
1895static const char *handle_dots(struct nameidata *nd, int type)
1896{
1897 if (type == LAST_DOTDOT) {
1898 const char *error = NULL;
1899 struct dentry *parent;
1900 struct inode *inode;
1901 unsigned seq;
1902
1903 if (!nd->root.mnt) {
1904 error = ERR_PTR(set_root(nd));
1905 if (error)
1906 return error;
1907 }
1908 if (nd->flags & LOOKUP_RCU)
1909 parent = follow_dotdot_rcu(nd, &inode, &seq);
1910 else
1911 parent = follow_dotdot(nd, &inode, &seq);
1912 if (IS_ERR(parent))
1913 return ERR_CAST(parent);
1914 if (unlikely(!parent))
1915 error = step_into(nd, WALK_NOFOLLOW,
1916 nd->path.dentry, nd->inode, nd->seq);
1917 else
1918 error = step_into(nd, WALK_NOFOLLOW,
1919 parent, inode, seq);
1920 if (unlikely(error))
1921 return error;
1922
1923 if (unlikely(nd->flags & LOOKUP_IS_SCOPED)) {
1924 /*
1925 * If there was a racing rename or mount along our
1926 * path, then we can't be sure that ".." hasn't jumped
1927 * above nd->root (and so userspace should retry or use
1928 * some fallback).
1929 */
1930 smp_rmb();
1931 if (unlikely(__read_seqcount_retry(&mount_lock.seqcount, nd->m_seq)))
1932 return ERR_PTR(-EAGAIN);
1933 if (unlikely(__read_seqcount_retry(&rename_lock.seqcount, nd->r_seq)))
1934 return ERR_PTR(-EAGAIN);
1935 }
1936 }
1937 return NULL;
1938}
1939
1940static const char *walk_component(struct nameidata *nd, int flags)
1941{
1942 struct dentry *dentry;
1943 struct inode *inode;
1944 unsigned seq;
1945 /*
1946 * "." and ".." are special - ".." especially so because it has
1947 * to be able to know about the current root directory and
1948 * parent relationships.
1949 */
1950 if (unlikely(nd->last_type != LAST_NORM)) {
1951 if (!(flags & WALK_MORE) && nd->depth)
1952 put_link(nd);
1953 return handle_dots(nd, nd->last_type);
1954 }
1955 dentry = lookup_fast(nd, &inode, &seq);
1956 if (IS_ERR(dentry))
1957 return ERR_CAST(dentry);
1958 if (unlikely(!dentry)) {
1959 dentry = lookup_slow(&nd->last, nd->path.dentry, nd->flags);
1960 if (IS_ERR(dentry))
1961 return ERR_CAST(dentry);
1962 }
1963 if (!(flags & WALK_MORE) && nd->depth)
1964 put_link(nd);
1965 return step_into(nd, flags, dentry, inode, seq);
1966}
1967
1968/*
1969 * We can do the critical dentry name comparison and hashing
1970 * operations one word at a time, but we are limited to:
1971 *
1972 * - Architectures with fast unaligned word accesses. We could
1973 * do a "get_unaligned()" if this helps and is sufficiently
1974 * fast.
1975 *
1976 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
1977 * do not trap on the (extremely unlikely) case of a page
1978 * crossing operation.
1979 *
1980 * - Furthermore, we need an efficient 64-bit compile for the
1981 * 64-bit case in order to generate the "number of bytes in
1982 * the final mask". Again, that could be replaced with a
1983 * efficient population count instruction or similar.
1984 */
1985#ifdef CONFIG_DCACHE_WORD_ACCESS
1986
1987#include <asm/word-at-a-time.h>
1988
1989#ifdef HASH_MIX
1990
1991/* Architecture provides HASH_MIX and fold_hash() in <asm/hash.h> */
1992
1993#elif defined(CONFIG_64BIT)
1994/*
1995 * Register pressure in the mixing function is an issue, particularly
1996 * on 32-bit x86, but almost any function requires one state value and
1997 * one temporary. Instead, use a function designed for two state values
1998 * and no temporaries.
1999 *
2000 * This function cannot create a collision in only two iterations, so
2001 * we have two iterations to achieve avalanche. In those two iterations,
2002 * we have six layers of mixing, which is enough to spread one bit's
2003 * influence out to 2^6 = 64 state bits.
2004 *
2005 * Rotate constants are scored by considering either 64 one-bit input
2006 * deltas or 64*63/2 = 2016 two-bit input deltas, and finding the
2007 * probability of that delta causing a change to each of the 128 output
2008 * bits, using a sample of random initial states.
2009 *
2010 * The Shannon entropy of the computed probabilities is then summed
2011 * to produce a score. Ideally, any input change has a 50% chance of
2012 * toggling any given output bit.
2013 *
2014 * Mixing scores (in bits) for (12,45):
2015 * Input delta: 1-bit 2-bit
2016 * 1 round: 713.3 42542.6
2017 * 2 rounds: 2753.7 140389.8
2018 * 3 rounds: 5954.1 233458.2
2019 * 4 rounds: 7862.6 256672.2
2020 * Perfect: 8192 258048
2021 * (64*128) (64*63/2 * 128)
2022 */
2023#define HASH_MIX(x, y, a) \
2024 ( x ^= (a), \
2025 y ^= x, x = rol64(x,12),\
2026 x += y, y = rol64(y,45),\
2027 y *= 9 )
2028
2029/*
2030 * Fold two longs into one 32-bit hash value. This must be fast, but
2031 * latency isn't quite as critical, as there is a fair bit of additional
2032 * work done before the hash value is used.
2033 */
2034static inline unsigned int fold_hash(unsigned long x, unsigned long y)
2035{
2036 y ^= x * GOLDEN_RATIO_64;
2037 y *= GOLDEN_RATIO_64;
2038 return y >> 32;
2039}
2040
2041#else /* 32-bit case */
2042
2043/*
2044 * Mixing scores (in bits) for (7,20):
2045 * Input delta: 1-bit 2-bit
2046 * 1 round: 330.3 9201.6
2047 * 2 rounds: 1246.4 25475.4
2048 * 3 rounds: 1907.1 31295.1
2049 * 4 rounds: 2042.3 31718.6
2050 * Perfect: 2048 31744
2051 * (32*64) (32*31/2 * 64)
2052 */
2053#define HASH_MIX(x, y, a) \
2054 ( x ^= (a), \
2055 y ^= x, x = rol32(x, 7),\
2056 x += y, y = rol32(y,20),\
2057 y *= 9 )
2058
2059static inline unsigned int fold_hash(unsigned long x, unsigned long y)
2060{
2061 /* Use arch-optimized multiply if one exists */
2062 return __hash_32(y ^ __hash_32(x));
2063}
2064
2065#endif
2066
2067/*
2068 * Return the hash of a string of known length. This is carfully
2069 * designed to match hash_name(), which is the more critical function.
2070 * In particular, we must end by hashing a final word containing 0..7
2071 * payload bytes, to match the way that hash_name() iterates until it
2072 * finds the delimiter after the name.
2073 */
2074unsigned int full_name_hash(const void *salt, const char *name, unsigned int len)
2075{
2076 unsigned long a, x = 0, y = (unsigned long)salt;
2077
2078 for (;;) {
2079 if (!len)
2080 goto done;
2081 a = load_unaligned_zeropad(name);
2082 if (len < sizeof(unsigned long))
2083 break;
2084 HASH_MIX(x, y, a);
2085 name += sizeof(unsigned long);
2086 len -= sizeof(unsigned long);
2087 }
2088 x ^= a & bytemask_from_count(len);
2089done:
2090 return fold_hash(x, y);
2091}
2092EXPORT_SYMBOL(full_name_hash);
2093
2094/* Return the "hash_len" (hash and length) of a null-terminated string */
2095u64 hashlen_string(const void *salt, const char *name)
2096{
2097 unsigned long a = 0, x = 0, y = (unsigned long)salt;
2098 unsigned long adata, mask, len;
2099 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
2100
2101 len = 0;
2102 goto inside;
2103
2104 do {
2105 HASH_MIX(x, y, a);
2106 len += sizeof(unsigned long);
2107inside:
2108 a = load_unaligned_zeropad(name+len);
2109 } while (!has_zero(a, &adata, &constants));
2110
2111 adata = prep_zero_mask(a, adata, &constants);
2112 mask = create_zero_mask(adata);
2113 x ^= a & zero_bytemask(mask);
2114
2115 return hashlen_create(fold_hash(x, y), len + find_zero(mask));
2116}
2117EXPORT_SYMBOL(hashlen_string);
2118
2119/*
2120 * Calculate the length and hash of the path component, and
2121 * return the "hash_len" as the result.
2122 */
2123static inline u64 hash_name(const void *salt, const char *name)
2124{
2125 unsigned long a = 0, b, x = 0, y = (unsigned long)salt;
2126 unsigned long adata, bdata, mask, len;
2127 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
2128
2129 len = 0;
2130 goto inside;
2131
2132 do {
2133 HASH_MIX(x, y, a);
2134 len += sizeof(unsigned long);
2135inside:
2136 a = load_unaligned_zeropad(name+len);
2137 b = a ^ REPEAT_BYTE('/');
2138 } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants)));
2139
2140 adata = prep_zero_mask(a, adata, &constants);
2141 bdata = prep_zero_mask(b, bdata, &constants);
2142 mask = create_zero_mask(adata | bdata);
2143 x ^= a & zero_bytemask(mask);
2144
2145 return hashlen_create(fold_hash(x, y), len + find_zero(mask));
2146}
2147
2148#else /* !CONFIG_DCACHE_WORD_ACCESS: Slow, byte-at-a-time version */
2149
2150/* Return the hash of a string of known length */
2151unsigned int full_name_hash(const void *salt, const char *name, unsigned int len)
2152{
2153 unsigned long hash = init_name_hash(salt);
2154 while (len--)
2155 hash = partial_name_hash((unsigned char)*name++, hash);
2156 return end_name_hash(hash);
2157}
2158EXPORT_SYMBOL(full_name_hash);
2159
2160/* Return the "hash_len" (hash and length) of a null-terminated string */
2161u64 hashlen_string(const void *salt, const char *name)
2162{
2163 unsigned long hash = init_name_hash(salt);
2164 unsigned long len = 0, c;
2165
2166 c = (unsigned char)*name;
2167 while (c) {
2168 len++;
2169 hash = partial_name_hash(c, hash);
2170 c = (unsigned char)name[len];
2171 }
2172 return hashlen_create(end_name_hash(hash), len);
2173}
2174EXPORT_SYMBOL(hashlen_string);
2175
2176/*
2177 * We know there's a real path component here of at least
2178 * one character.
2179 */
2180static inline u64 hash_name(const void *salt, const char *name)
2181{
2182 unsigned long hash = init_name_hash(salt);
2183 unsigned long len = 0, c;
2184
2185 c = (unsigned char)*name;
2186 do {
2187 len++;
2188 hash = partial_name_hash(c, hash);
2189 c = (unsigned char)name[len];
2190 } while (c && c != '/');
2191 return hashlen_create(end_name_hash(hash), len);
2192}
2193
2194#endif
2195
2196/*
2197 * Name resolution.
2198 * This is the basic name resolution function, turning a pathname into
2199 * the final dentry. We expect 'base' to be positive and a directory.
2200 *
2201 * Returns 0 and nd will have valid dentry and mnt on success.
2202 * Returns error and drops reference to input namei data on failure.
2203 */
2204static int link_path_walk(const char *name, struct nameidata *nd)
2205{
2206 int depth = 0; // depth <= nd->depth
2207 int err;
2208
2209 nd->last_type = LAST_ROOT;
2210 nd->flags |= LOOKUP_PARENT;
2211 if (IS_ERR(name))
2212 return PTR_ERR(name);
2213 while (*name=='/')
2214 name++;
2215 if (!*name) {
2216 nd->dir_mode = 0; // short-circuit the 'hardening' idiocy
2217 return 0;
2218 }
2219
2220 /* At this point we know we have a real path component. */
2221 for(;;) {
2222 struct user_namespace *mnt_userns;
2223 const char *link;
2224 u64 hash_len;
2225 int type;
2226
2227 mnt_userns = mnt_user_ns(nd->path.mnt);
2228 err = may_lookup(mnt_userns, nd);
2229 if (err)
2230 return err;
2231
2232 hash_len = hash_name(nd->path.dentry, name);
2233
2234 type = LAST_NORM;
2235 if (name[0] == '.') switch (hashlen_len(hash_len)) {
2236 case 2:
2237 if (name[1] == '.') {
2238 type = LAST_DOTDOT;
2239 nd->state |= ND_JUMPED;
2240 }
2241 break;
2242 case 1:
2243 type = LAST_DOT;
2244 }
2245 if (likely(type == LAST_NORM)) {
2246 struct dentry *parent = nd->path.dentry;
2247 nd->state &= ~ND_JUMPED;
2248 if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
2249 struct qstr this = { { .hash_len = hash_len }, .name = name };
2250 err = parent->d_op->d_hash(parent, &this);
2251 if (err < 0)
2252 return err;
2253 hash_len = this.hash_len;
2254 name = this.name;
2255 }
2256 }
2257
2258 nd->last.hash_len = hash_len;
2259 nd->last.name = name;
2260 nd->last_type = type;
2261
2262 name += hashlen_len(hash_len);
2263 if (!*name)
2264 goto OK;
2265 /*
2266 * If it wasn't NUL, we know it was '/'. Skip that
2267 * slash, and continue until no more slashes.
2268 */
2269 do {
2270 name++;
2271 } while (unlikely(*name == '/'));
2272 if (unlikely(!*name)) {
2273OK:
2274 /* pathname or trailing symlink, done */
2275 if (!depth) {
2276 nd->dir_uid = i_uid_into_mnt(mnt_userns, nd->inode);
2277 nd->dir_mode = nd->inode->i_mode;
2278 nd->flags &= ~LOOKUP_PARENT;
2279 return 0;
2280 }
2281 /* last component of nested symlink */
2282 name = nd->stack[--depth].name;
2283 link = walk_component(nd, 0);
2284 } else {
2285 /* not the last component */
2286 link = walk_component(nd, WALK_MORE);
2287 }
2288 if (unlikely(link)) {
2289 if (IS_ERR(link))
2290 return PTR_ERR(link);
2291 /* a symlink to follow */
2292 nd->stack[depth++].name = name;
2293 name = link;
2294 continue;
2295 }
2296 if (unlikely(!d_can_lookup(nd->path.dentry))) {
2297 if (nd->flags & LOOKUP_RCU) {
2298 if (!try_to_unlazy(nd))
2299 return -ECHILD;
2300 }
2301 return -ENOTDIR;
2302 }
2303 }
2304}
2305
2306/* must be paired with terminate_walk() */
2307static const char *path_init(struct nameidata *nd, unsigned flags)
2308{
2309 int error;
2310 const char *s = nd->name->name;
2311
2312 /* LOOKUP_CACHED requires RCU, ask caller to retry */
2313 if ((flags & (LOOKUP_RCU | LOOKUP_CACHED)) == LOOKUP_CACHED)
2314 return ERR_PTR(-EAGAIN);
2315
2316 if (!*s)
2317 flags &= ~LOOKUP_RCU;
2318 if (flags & LOOKUP_RCU)
2319 rcu_read_lock();
2320
2321 nd->flags = flags;
2322 nd->state |= ND_JUMPED;
2323
2324 nd->m_seq = __read_seqcount_begin(&mount_lock.seqcount);
2325 nd->r_seq = __read_seqcount_begin(&rename_lock.seqcount);
2326 smp_rmb();
2327
2328 if (nd->state & ND_ROOT_PRESET) {
2329 struct dentry *root = nd->root.dentry;
2330 struct inode *inode = root->d_inode;
2331 if (*s && unlikely(!d_can_lookup(root)))
2332 return ERR_PTR(-ENOTDIR);
2333 nd->path = nd->root;
2334 nd->inode = inode;
2335 if (flags & LOOKUP_RCU) {
2336 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
2337 nd->root_seq = nd->seq;
2338 } else {
2339 path_get(&nd->path);
2340 }
2341 return s;
2342 }
2343
2344 nd->root.mnt = NULL;
2345
2346 /* Absolute pathname -- fetch the root (LOOKUP_IN_ROOT uses nd->dfd). */
2347 if (*s == '/' && !(flags & LOOKUP_IN_ROOT)) {
2348 error = nd_jump_root(nd);
2349 if (unlikely(error))
2350 return ERR_PTR(error);
2351 return s;
2352 }
2353
2354 /* Relative pathname -- get the starting-point it is relative to. */
2355 if (nd->dfd == AT_FDCWD) {
2356 if (flags & LOOKUP_RCU) {
2357 struct fs_struct *fs = current->fs;
2358 unsigned seq;
2359
2360 do {
2361 seq = read_seqcount_begin(&fs->seq);
2362 nd->path = fs->pwd;
2363 nd->inode = nd->path.dentry->d_inode;
2364 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
2365 } while (read_seqcount_retry(&fs->seq, seq));
2366 } else {
2367 get_fs_pwd(current->fs, &nd->path);
2368 nd->inode = nd->path.dentry->d_inode;
2369 }
2370 } else {
2371 /* Caller must check execute permissions on the starting path component */
2372 struct fd f = fdget_raw(nd->dfd);
2373 struct dentry *dentry;
2374
2375 if (!f.file)
2376 return ERR_PTR(-EBADF);
2377
2378 dentry = f.file->f_path.dentry;
2379
2380 if (*s && unlikely(!d_can_lookup(dentry))) {
2381 fdput(f);
2382 return ERR_PTR(-ENOTDIR);
2383 }
2384
2385 nd->path = f.file->f_path;
2386 if (flags & LOOKUP_RCU) {
2387 nd->inode = nd->path.dentry->d_inode;
2388 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
2389 } else {
2390 path_get(&nd->path);
2391 nd->inode = nd->path.dentry->d_inode;
2392 }
2393 fdput(f);
2394 }
2395
2396 /* For scoped-lookups we need to set the root to the dirfd as well. */
2397 if (flags & LOOKUP_IS_SCOPED) {
2398 nd->root = nd->path;
2399 if (flags & LOOKUP_RCU) {
2400 nd->root_seq = nd->seq;
2401 } else {
2402 path_get(&nd->root);
2403 nd->state |= ND_ROOT_GRABBED;
2404 }
2405 }
2406 return s;
2407}
2408
2409static inline const char *lookup_last(struct nameidata *nd)
2410{
2411 if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
2412 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
2413
2414 return walk_component(nd, WALK_TRAILING);
2415}
2416
2417static int handle_lookup_down(struct nameidata *nd)
2418{
2419 if (!(nd->flags & LOOKUP_RCU))
2420 dget(nd->path.dentry);
2421 return PTR_ERR(step_into(nd, WALK_NOFOLLOW,
2422 nd->path.dentry, nd->inode, nd->seq));
2423}
2424
2425/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
2426static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path)
2427{
2428 const char *s = path_init(nd, flags);
2429 int err;
2430
2431 if (unlikely(flags & LOOKUP_DOWN) && !IS_ERR(s)) {
2432 err = handle_lookup_down(nd);
2433 if (unlikely(err < 0))
2434 s = ERR_PTR(err);
2435 }
2436
2437 while (!(err = link_path_walk(s, nd)) &&
2438 (s = lookup_last(nd)) != NULL)
2439 ;
2440 if (!err && unlikely(nd->flags & LOOKUP_MOUNTPOINT)) {
2441 err = handle_lookup_down(nd);
2442 nd->state &= ~ND_JUMPED; // no d_weak_revalidate(), please...
2443 }
2444 if (!err)
2445 err = complete_walk(nd);
2446
2447 if (!err && nd->flags & LOOKUP_DIRECTORY)
2448 if (!d_can_lookup(nd->path.dentry))
2449 err = -ENOTDIR;
2450 if (!err) {
2451 *path = nd->path;
2452 nd->path.mnt = NULL;
2453 nd->path.dentry = NULL;
2454 }
2455 terminate_walk(nd);
2456 return err;
2457}
2458
2459int filename_lookup(int dfd, struct filename *name, unsigned flags,
2460 struct path *path, struct path *root)
2461{
2462 int retval;
2463 struct nameidata nd;
2464 if (IS_ERR(name))
2465 return PTR_ERR(name);
2466 set_nameidata(&nd, dfd, name, root);
2467 retval = path_lookupat(&nd, flags | LOOKUP_RCU, path);
2468 if (unlikely(retval == -ECHILD))
2469 retval = path_lookupat(&nd, flags, path);
2470 if (unlikely(retval == -ESTALE))
2471 retval = path_lookupat(&nd, flags | LOOKUP_REVAL, path);
2472
2473 if (likely(!retval))
2474 audit_inode(name, path->dentry,
2475 flags & LOOKUP_MOUNTPOINT ? AUDIT_INODE_NOEVAL : 0);
2476 restore_nameidata();
2477 putname(name);
2478 return retval;
2479}
2480
2481/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
2482static int path_parentat(struct nameidata *nd, unsigned flags,
2483 struct path *parent)
2484{
2485 const char *s = path_init(nd, flags);
2486 int err = link_path_walk(s, nd);
2487 if (!err)
2488 err = complete_walk(nd);
2489 if (!err) {
2490 *parent = nd->path;
2491 nd->path.mnt = NULL;
2492 nd->path.dentry = NULL;
2493 }
2494 terminate_walk(nd);
2495 return err;
2496}
2497
2498static struct filename *filename_parentat(int dfd, struct filename *name,
2499 unsigned int flags, struct path *parent,
2500 struct qstr *last, int *type)
2501{
2502 int retval;
2503 struct nameidata nd;
2504
2505 if (IS_ERR(name))
2506 return name;
2507 set_nameidata(&nd, dfd, name, NULL);
2508 retval = path_parentat(&nd, flags | LOOKUP_RCU, parent);
2509 if (unlikely(retval == -ECHILD))
2510 retval = path_parentat(&nd, flags, parent);
2511 if (unlikely(retval == -ESTALE))
2512 retval = path_parentat(&nd, flags | LOOKUP_REVAL, parent);
2513 if (likely(!retval)) {
2514 *last = nd.last;
2515 *type = nd.last_type;
2516 audit_inode(name, parent->dentry, AUDIT_INODE_PARENT);
2517 } else {
2518 putname(name);
2519 name = ERR_PTR(retval);
2520 }
2521 restore_nameidata();
2522 return name;
2523}
2524
2525/* does lookup, returns the object with parent locked */
2526struct dentry *kern_path_locked(const char *name, struct path *path)
2527{
2528 struct filename *filename;
2529 struct dentry *d;
2530 struct qstr last;
2531 int type;
2532
2533 filename = filename_parentat(AT_FDCWD, getname_kernel(name), 0, path,
2534 &last, &type);
2535 if (IS_ERR(filename))
2536 return ERR_CAST(filename);
2537 if (unlikely(type != LAST_NORM)) {
2538 path_put(path);
2539 putname(filename);
2540 return ERR_PTR(-EINVAL);
2541 }
2542 inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
2543 d = __lookup_hash(&last, path->dentry, 0);
2544 if (IS_ERR(d)) {
2545 inode_unlock(path->dentry->d_inode);
2546 path_put(path);
2547 }
2548 putname(filename);
2549 return d;
2550}
2551
2552int kern_path(const char *name, unsigned int flags, struct path *path)
2553{
2554 return filename_lookup(AT_FDCWD, getname_kernel(name),
2555 flags, path, NULL);
2556}
2557EXPORT_SYMBOL(kern_path);
2558
2559/**
2560 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
2561 * @dentry: pointer to dentry of the base directory
2562 * @mnt: pointer to vfs mount of the base directory
2563 * @name: pointer to file name
2564 * @flags: lookup flags
2565 * @path: pointer to struct path to fill
2566 */
2567int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
2568 const char *name, unsigned int flags,
2569 struct path *path)
2570{
2571 struct path root = {.mnt = mnt, .dentry = dentry};
2572 /* the first argument of filename_lookup() is ignored with root */
2573 return filename_lookup(AT_FDCWD, getname_kernel(name),
2574 flags , path, &root);
2575}
2576EXPORT_SYMBOL(vfs_path_lookup);
2577
2578static int lookup_one_len_common(const char *name, struct dentry *base,
2579 int len, struct qstr *this)
2580{
2581 this->name = name;
2582 this->len = len;
2583 this->hash = full_name_hash(base, name, len);
2584 if (!len)
2585 return -EACCES;
2586
2587 if (unlikely(name[0] == '.')) {
2588 if (len < 2 || (len == 2 && name[1] == '.'))
2589 return -EACCES;
2590 }
2591
2592 while (len--) {
2593 unsigned int c = *(const unsigned char *)name++;
2594 if (c == '/' || c == '\0')
2595 return -EACCES;
2596 }
2597 /*
2598 * See if the low-level filesystem might want
2599 * to use its own hash..
2600 */
2601 if (base->d_flags & DCACHE_OP_HASH) {
2602 int err = base->d_op->d_hash(base, this);
2603 if (err < 0)
2604 return err;
2605 }
2606
2607 return inode_permission(&init_user_ns, base->d_inode, MAY_EXEC);
2608}
2609
2610/**
2611 * try_lookup_one_len - filesystem helper to lookup single pathname component
2612 * @name: pathname component to lookup
2613 * @base: base directory to lookup from
2614 * @len: maximum length @len should be interpreted to
2615 *
2616 * Look up a dentry by name in the dcache, returning NULL if it does not
2617 * currently exist. The function does not try to create a dentry.
2618 *
2619 * Note that this routine is purely a helper for filesystem usage and should
2620 * not be called by generic code.
2621 *
2622 * The caller must hold base->i_mutex.
2623 */
2624struct dentry *try_lookup_one_len(const char *name, struct dentry *base, int len)
2625{
2626 struct qstr this;
2627 int err;
2628
2629 WARN_ON_ONCE(!inode_is_locked(base->d_inode));
2630
2631 err = lookup_one_len_common(name, base, len, &this);
2632 if (err)
2633 return ERR_PTR(err);
2634
2635 return lookup_dcache(&this, base, 0);
2636}
2637EXPORT_SYMBOL(try_lookup_one_len);
2638
2639/**
2640 * lookup_one_len - filesystem helper to lookup single pathname component
2641 * @name: pathname component to lookup
2642 * @base: base directory to lookup from
2643 * @len: maximum length @len should be interpreted to
2644 *
2645 * Note that this routine is purely a helper for filesystem usage and should
2646 * not be called by generic code.
2647 *
2648 * The caller must hold base->i_mutex.
2649 */
2650struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
2651{
2652 struct dentry *dentry;
2653 struct qstr this;
2654 int err;
2655
2656 WARN_ON_ONCE(!inode_is_locked(base->d_inode));
2657
2658 err = lookup_one_len_common(name, base, len, &this);
2659 if (err)
2660 return ERR_PTR(err);
2661
2662 dentry = lookup_dcache(&this, base, 0);
2663 return dentry ? dentry : __lookup_slow(&this, base, 0);
2664}
2665EXPORT_SYMBOL(lookup_one_len);
2666
2667/**
2668 * lookup_one_len_unlocked - filesystem helper to lookup single pathname component
2669 * @name: pathname component to lookup
2670 * @base: base directory to lookup from
2671 * @len: maximum length @len should be interpreted to
2672 *
2673 * Note that this routine is purely a helper for filesystem usage and should
2674 * not be called by generic code.
2675 *
2676 * Unlike lookup_one_len, it should be called without the parent
2677 * i_mutex held, and will take the i_mutex itself if necessary.
2678 */
2679struct dentry *lookup_one_len_unlocked(const char *name,
2680 struct dentry *base, int len)
2681{
2682 struct qstr this;
2683 int err;
2684 struct dentry *ret;
2685
2686 err = lookup_one_len_common(name, base, len, &this);
2687 if (err)
2688 return ERR_PTR(err);
2689
2690 ret = lookup_dcache(&this, base, 0);
2691 if (!ret)
2692 ret = lookup_slow(&this, base, 0);
2693 return ret;
2694}
2695EXPORT_SYMBOL(lookup_one_len_unlocked);
2696
2697/*
2698 * Like lookup_one_len_unlocked(), except that it yields ERR_PTR(-ENOENT)
2699 * on negatives. Returns known positive or ERR_PTR(); that's what
2700 * most of the users want. Note that pinned negative with unlocked parent
2701 * _can_ become positive at any time, so callers of lookup_one_len_unlocked()
2702 * need to be very careful; pinned positives have ->d_inode stable, so
2703 * this one avoids such problems.
2704 */
2705struct dentry *lookup_positive_unlocked(const char *name,
2706 struct dentry *base, int len)
2707{
2708 struct dentry *ret = lookup_one_len_unlocked(name, base, len);
2709 if (!IS_ERR(ret) && d_flags_negative(smp_load_acquire(&ret->d_flags))) {
2710 dput(ret);
2711 ret = ERR_PTR(-ENOENT);
2712 }
2713 return ret;
2714}
2715EXPORT_SYMBOL(lookup_positive_unlocked);
2716
2717#ifdef CONFIG_UNIX98_PTYS
2718int path_pts(struct path *path)
2719{
2720 /* Find something mounted on "pts" in the same directory as
2721 * the input path.
2722 */
2723 struct dentry *parent = dget_parent(path->dentry);
2724 struct dentry *child;
2725 struct qstr this = QSTR_INIT("pts", 3);
2726
2727 if (unlikely(!path_connected(path->mnt, parent))) {
2728 dput(parent);
2729 return -ENOENT;
2730 }
2731 dput(path->dentry);
2732 path->dentry = parent;
2733 child = d_hash_and_lookup(parent, &this);
2734 if (!child)
2735 return -ENOENT;
2736
2737 path->dentry = child;
2738 dput(parent);
2739 follow_down(path);
2740 return 0;
2741}
2742#endif
2743
2744int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
2745 struct path *path, int *empty)
2746{
2747 return filename_lookup(dfd, getname_flags(name, flags, empty),
2748 flags, path, NULL);
2749}
2750EXPORT_SYMBOL(user_path_at_empty);
2751
2752int __check_sticky(struct user_namespace *mnt_userns, struct inode *dir,
2753 struct inode *inode)
2754{
2755 kuid_t fsuid = current_fsuid();
2756
2757 if (uid_eq(i_uid_into_mnt(mnt_userns, inode), fsuid))
2758 return 0;
2759 if (uid_eq(i_uid_into_mnt(mnt_userns, dir), fsuid))
2760 return 0;
2761 return !capable_wrt_inode_uidgid(mnt_userns, inode, CAP_FOWNER);
2762}
2763EXPORT_SYMBOL(__check_sticky);
2764
2765/*
2766 * Check whether we can remove a link victim from directory dir, check
2767 * whether the type of victim is right.
2768 * 1. We can't do it if dir is read-only (done in permission())
2769 * 2. We should have write and exec permissions on dir
2770 * 3. We can't remove anything from append-only dir
2771 * 4. We can't do anything with immutable dir (done in permission())
2772 * 5. If the sticky bit on dir is set we should either
2773 * a. be owner of dir, or
2774 * b. be owner of victim, or
2775 * c. have CAP_FOWNER capability
2776 * 6. If the victim is append-only or immutable we can't do antyhing with
2777 * links pointing to it.
2778 * 7. If the victim has an unknown uid or gid we can't change the inode.
2779 * 8. If we were asked to remove a directory and victim isn't one - ENOTDIR.
2780 * 9. If we were asked to remove a non-directory and victim isn't one - EISDIR.
2781 * 10. We can't remove a root or mountpoint.
2782 * 11. We don't allow removal of NFS sillyrenamed files; it's handled by
2783 * nfs_async_unlink().
2784 */
2785static int may_delete(struct user_namespace *mnt_userns, struct inode *dir,
2786 struct dentry *victim, bool isdir)
2787{
2788 struct inode *inode = d_backing_inode(victim);
2789 int error;
2790
2791 if (d_is_negative(victim))
2792 return -ENOENT;
2793 BUG_ON(!inode);
2794
2795 BUG_ON(victim->d_parent->d_inode != dir);
2796
2797 /* Inode writeback is not safe when the uid or gid are invalid. */
2798 if (!uid_valid(i_uid_into_mnt(mnt_userns, inode)) ||
2799 !gid_valid(i_gid_into_mnt(mnt_userns, inode)))
2800 return -EOVERFLOW;
2801
2802 audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE);
2803
2804 error = inode_permission(mnt_userns, dir, MAY_WRITE | MAY_EXEC);
2805 if (error)
2806 return error;
2807 if (IS_APPEND(dir))
2808 return -EPERM;
2809
2810 if (check_sticky(mnt_userns, dir, inode) || IS_APPEND(inode) ||
2811 IS_IMMUTABLE(inode) || IS_SWAPFILE(inode) ||
2812 HAS_UNMAPPED_ID(mnt_userns, inode))
2813 return -EPERM;
2814 if (isdir) {
2815 if (!d_is_dir(victim))
2816 return -ENOTDIR;
2817 if (IS_ROOT(victim))
2818 return -EBUSY;
2819 } else if (d_is_dir(victim))
2820 return -EISDIR;
2821 if (IS_DEADDIR(dir))
2822 return -ENOENT;
2823 if (victim->d_flags & DCACHE_NFSFS_RENAMED)
2824 return -EBUSY;
2825 return 0;
2826}
2827
2828/* Check whether we can create an object with dentry child in directory
2829 * dir.
2830 * 1. We can't do it if child already exists (open has special treatment for
2831 * this case, but since we are inlined it's OK)
2832 * 2. We can't do it if dir is read-only (done in permission())
2833 * 3. We can't do it if the fs can't represent the fsuid or fsgid.
2834 * 4. We should have write and exec permissions on dir
2835 * 5. We can't do it if dir is immutable (done in permission())
2836 */
2837static inline int may_create(struct user_namespace *mnt_userns,
2838 struct inode *dir, struct dentry *child)
2839{
2840 audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE);
2841 if (child->d_inode)
2842 return -EEXIST;
2843 if (IS_DEADDIR(dir))
2844 return -ENOENT;
2845 if (!fsuidgid_has_mapping(dir->i_sb, mnt_userns))
2846 return -EOVERFLOW;
2847
2848 return inode_permission(mnt_userns, dir, MAY_WRITE | MAY_EXEC);
2849}
2850
2851/*
2852 * p1 and p2 should be directories on the same fs.
2853 */
2854struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
2855{
2856 struct dentry *p;
2857
2858 if (p1 == p2) {
2859 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
2860 return NULL;
2861 }
2862
2863 mutex_lock(&p1->d_sb->s_vfs_rename_mutex);
2864
2865 p = d_ancestor(p2, p1);
2866 if (p) {
2867 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT);
2868 inode_lock_nested(p1->d_inode, I_MUTEX_CHILD);
2869 return p;
2870 }
2871
2872 p = d_ancestor(p1, p2);
2873 if (p) {
2874 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
2875 inode_lock_nested(p2->d_inode, I_MUTEX_CHILD);
2876 return p;
2877 }
2878
2879 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
2880 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT2);
2881 return NULL;
2882}
2883EXPORT_SYMBOL(lock_rename);
2884
2885void unlock_rename(struct dentry *p1, struct dentry *p2)
2886{
2887 inode_unlock(p1->d_inode);
2888 if (p1 != p2) {
2889 inode_unlock(p2->d_inode);
2890 mutex_unlock(&p1->d_sb->s_vfs_rename_mutex);
2891 }
2892}
2893EXPORT_SYMBOL(unlock_rename);
2894
2895/**
2896 * vfs_create - create new file
2897 * @mnt_userns: user namespace of the mount the inode was found from
2898 * @dir: inode of @dentry
2899 * @dentry: pointer to dentry of the base directory
2900 * @mode: mode of the new file
2901 * @want_excl: whether the file must not yet exist
2902 *
2903 * Create a new file.
2904 *
2905 * If the inode has been found through an idmapped mount the user namespace of
2906 * the vfsmount must be passed through @mnt_userns. This function will then take
2907 * care to map the inode according to @mnt_userns before checking permissions.
2908 * On non-idmapped mounts or if permission checking is to be performed on the
2909 * raw inode simply passs init_user_ns.
2910 */
2911int vfs_create(struct user_namespace *mnt_userns, struct inode *dir,
2912 struct dentry *dentry, umode_t mode, bool want_excl)
2913{
2914 int error = may_create(mnt_userns, dir, dentry);
2915 if (error)
2916 return error;
2917
2918 if (!dir->i_op->create)
2919 return -EACCES; /* shouldn't it be ENOSYS? */
2920 mode &= S_IALLUGO;
2921 mode |= S_IFREG;
2922 error = security_inode_create(dir, dentry, mode);
2923 if (error)
2924 return error;
2925 error = dir->i_op->create(mnt_userns, dir, dentry, mode, want_excl);
2926 if (!error)
2927 fsnotify_create(dir, dentry);
2928 return error;
2929}
2930EXPORT_SYMBOL(vfs_create);
2931
2932int vfs_mkobj(struct dentry *dentry, umode_t mode,
2933 int (*f)(struct dentry *, umode_t, void *),
2934 void *arg)
2935{
2936 struct inode *dir = dentry->d_parent->d_inode;
2937 int error = may_create(&init_user_ns, dir, dentry);
2938 if (error)
2939 return error;
2940
2941 mode &= S_IALLUGO;
2942 mode |= S_IFREG;
2943 error = security_inode_create(dir, dentry, mode);
2944 if (error)
2945 return error;
2946 error = f(dentry, mode, arg);
2947 if (!error)
2948 fsnotify_create(dir, dentry);
2949 return error;
2950}
2951EXPORT_SYMBOL(vfs_mkobj);
2952
2953bool may_open_dev(const struct path *path)
2954{
2955 return !(path->mnt->mnt_flags & MNT_NODEV) &&
2956 !(path->mnt->mnt_sb->s_iflags & SB_I_NODEV);
2957}
2958
2959static int may_open(struct user_namespace *mnt_userns, const struct path *path,
2960 int acc_mode, int flag)
2961{
2962 struct dentry *dentry = path->dentry;
2963 struct inode *inode = dentry->d_inode;
2964 int error;
2965
2966 if (!inode)
2967 return -ENOENT;
2968
2969 switch (inode->i_mode & S_IFMT) {
2970 case S_IFLNK:
2971 return -ELOOP;
2972 case S_IFDIR:
2973 if (acc_mode & MAY_WRITE)
2974 return -EISDIR;
2975 if (acc_mode & MAY_EXEC)
2976 return -EACCES;
2977 break;
2978 case S_IFBLK:
2979 case S_IFCHR:
2980 if (!may_open_dev(path))
2981 return -EACCES;
2982 fallthrough;
2983 case S_IFIFO:
2984 case S_IFSOCK:
2985 if (acc_mode & MAY_EXEC)
2986 return -EACCES;
2987 flag &= ~O_TRUNC;
2988 break;
2989 case S_IFREG:
2990 if ((acc_mode & MAY_EXEC) && path_noexec(path))
2991 return -EACCES;
2992 break;
2993 }
2994
2995 error = inode_permission(mnt_userns, inode, MAY_OPEN | acc_mode);
2996 if (error)
2997 return error;
2998
2999 /*
3000 * An append-only file must be opened in append mode for writing.
3001 */
3002 if (IS_APPEND(inode)) {
3003 if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
3004 return -EPERM;
3005 if (flag & O_TRUNC)
3006 return -EPERM;
3007 }
3008
3009 /* O_NOATIME can only be set by the owner or superuser */
3010 if (flag & O_NOATIME && !inode_owner_or_capable(mnt_userns, inode))
3011 return -EPERM;
3012
3013 return 0;
3014}
3015
3016static int handle_truncate(struct user_namespace *mnt_userns, struct file *filp)
3017{
3018 const struct path *path = &filp->f_path;
3019 struct inode *inode = path->dentry->d_inode;
3020 int error = get_write_access(inode);
3021 if (error)
3022 return error;
3023 /*
3024 * Refuse to truncate files with mandatory locks held on them.
3025 */
3026 error = locks_verify_locked(filp);
3027 if (!error)
3028 error = security_path_truncate(path);
3029 if (!error) {
3030 error = do_truncate(mnt_userns, path->dentry, 0,
3031 ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
3032 filp);
3033 }
3034 put_write_access(inode);
3035 return error;
3036}
3037
3038static inline int open_to_namei_flags(int flag)
3039{
3040 if ((flag & O_ACCMODE) == 3)
3041 flag--;
3042 return flag;
3043}
3044
3045static int may_o_create(struct user_namespace *mnt_userns,
3046 const struct path *dir, struct dentry *dentry,
3047 umode_t mode)
3048{
3049 int error = security_path_mknod(dir, dentry, mode, 0);
3050 if (error)
3051 return error;
3052
3053 if (!fsuidgid_has_mapping(dir->dentry->d_sb, mnt_userns))
3054 return -EOVERFLOW;
3055
3056 error = inode_permission(mnt_userns, dir->dentry->d_inode,
3057 MAY_WRITE | MAY_EXEC);
3058 if (error)
3059 return error;
3060
3061 return security_inode_create(dir->dentry->d_inode, dentry, mode);
3062}
3063
3064/*
3065 * Attempt to atomically look up, create and open a file from a negative
3066 * dentry.
3067 *
3068 * Returns 0 if successful. The file will have been created and attached to
3069 * @file by the filesystem calling finish_open().
3070 *
3071 * If the file was looked up only or didn't need creating, FMODE_OPENED won't
3072 * be set. The caller will need to perform the open themselves. @path will
3073 * have been updated to point to the new dentry. This may be negative.
3074 *
3075 * Returns an error code otherwise.
3076 */
3077static struct dentry *atomic_open(struct nameidata *nd, struct dentry *dentry,
3078 struct file *file,
3079 int open_flag, umode_t mode)
3080{
3081 struct dentry *const DENTRY_NOT_SET = (void *) -1UL;
3082 struct inode *dir = nd->path.dentry->d_inode;
3083 int error;
3084
3085 if (nd->flags & LOOKUP_DIRECTORY)
3086 open_flag |= O_DIRECTORY;
3087
3088 file->f_path.dentry = DENTRY_NOT_SET;
3089 file->f_path.mnt = nd->path.mnt;
3090 error = dir->i_op->atomic_open(dir, dentry, file,
3091 open_to_namei_flags(open_flag), mode);
3092 d_lookup_done(dentry);
3093 if (!error) {
3094 if (file->f_mode & FMODE_OPENED) {
3095 if (unlikely(dentry != file->f_path.dentry)) {
3096 dput(dentry);
3097 dentry = dget(file->f_path.dentry);
3098 }
3099 } else if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) {
3100 error = -EIO;
3101 } else {
3102 if (file->f_path.dentry) {
3103 dput(dentry);
3104 dentry = file->f_path.dentry;
3105 }
3106 if (unlikely(d_is_negative(dentry)))
3107 error = -ENOENT;
3108 }
3109 }
3110 if (error) {
3111 dput(dentry);
3112 dentry = ERR_PTR(error);
3113 }
3114 return dentry;
3115}
3116
3117/*
3118 * Look up and maybe create and open the last component.
3119 *
3120 * Must be called with parent locked (exclusive in O_CREAT case).
3121 *
3122 * Returns 0 on success, that is, if
3123 * the file was successfully atomically created (if necessary) and opened, or
3124 * the file was not completely opened at this time, though lookups and
3125 * creations were performed.
3126 * These case are distinguished by presence of FMODE_OPENED on file->f_mode.
3127 * In the latter case dentry returned in @path might be negative if O_CREAT
3128 * hadn't been specified.
3129 *
3130 * An error code is returned on failure.
3131 */
3132static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
3133 const struct open_flags *op,
3134 bool got_write)
3135{
3136 struct user_namespace *mnt_userns;
3137 struct dentry *dir = nd->path.dentry;
3138 struct inode *dir_inode = dir->d_inode;
3139 int open_flag = op->open_flag;
3140 struct dentry *dentry;
3141 int error, create_error = 0;
3142 umode_t mode = op->mode;
3143 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
3144
3145 if (unlikely(IS_DEADDIR(dir_inode)))
3146 return ERR_PTR(-ENOENT);
3147
3148 file->f_mode &= ~FMODE_CREATED;
3149 dentry = d_lookup(dir, &nd->last);
3150 for (;;) {
3151 if (!dentry) {
3152 dentry = d_alloc_parallel(dir, &nd->last, &wq);
3153 if (IS_ERR(dentry))
3154 return dentry;
3155 }
3156 if (d_in_lookup(dentry))
3157 break;
3158
3159 error = d_revalidate(dentry, nd->flags);
3160 if (likely(error > 0))
3161 break;
3162 if (error)
3163 goto out_dput;
3164 d_invalidate(dentry);
3165 dput(dentry);
3166 dentry = NULL;
3167 }
3168 if (dentry->d_inode) {
3169 /* Cached positive dentry: will open in f_op->open */
3170 return dentry;
3171 }
3172
3173 /*
3174 * Checking write permission is tricky, bacuse we don't know if we are
3175 * going to actually need it: O_CREAT opens should work as long as the
3176 * file exists. But checking existence breaks atomicity. The trick is
3177 * to check access and if not granted clear O_CREAT from the flags.
3178 *
3179 * Another problem is returing the "right" error value (e.g. for an
3180 * O_EXCL open we want to return EEXIST not EROFS).
3181 */
3182 if (unlikely(!got_write))
3183 open_flag &= ~O_TRUNC;
3184 mnt_userns = mnt_user_ns(nd->path.mnt);
3185 if (open_flag & O_CREAT) {
3186 if (open_flag & O_EXCL)
3187 open_flag &= ~O_TRUNC;
3188 if (!IS_POSIXACL(dir->d_inode))
3189 mode &= ~current_umask();
3190 if (likely(got_write))
3191 create_error = may_o_create(mnt_userns, &nd->path,
3192 dentry, mode);
3193 else
3194 create_error = -EROFS;
3195 }
3196 if (create_error)
3197 open_flag &= ~O_CREAT;
3198 if (dir_inode->i_op->atomic_open) {
3199 dentry = atomic_open(nd, dentry, file, open_flag, mode);
3200 if (unlikely(create_error) && dentry == ERR_PTR(-ENOENT))
3201 dentry = ERR_PTR(create_error);
3202 return dentry;
3203 }
3204
3205 if (d_in_lookup(dentry)) {
3206 struct dentry *res = dir_inode->i_op->lookup(dir_inode, dentry,
3207 nd->flags);
3208 d_lookup_done(dentry);
3209 if (unlikely(res)) {
3210 if (IS_ERR(res)) {
3211 error = PTR_ERR(res);
3212 goto out_dput;
3213 }
3214 dput(dentry);
3215 dentry = res;
3216 }
3217 }
3218
3219 /* Negative dentry, just create the file */
3220 if (!dentry->d_inode && (open_flag & O_CREAT)) {
3221 file->f_mode |= FMODE_CREATED;
3222 audit_inode_child(dir_inode, dentry, AUDIT_TYPE_CHILD_CREATE);
3223 if (!dir_inode->i_op->create) {
3224 error = -EACCES;
3225 goto out_dput;
3226 }
3227
3228 error = dir_inode->i_op->create(mnt_userns, dir_inode, dentry,
3229 mode, open_flag & O_EXCL);
3230 if (error)
3231 goto out_dput;
3232 }
3233 if (unlikely(create_error) && !dentry->d_inode) {
3234 error = create_error;
3235 goto out_dput;
3236 }
3237 return dentry;
3238
3239out_dput:
3240 dput(dentry);
3241 return ERR_PTR(error);
3242}
3243
3244static const char *open_last_lookups(struct nameidata *nd,
3245 struct file *file, const struct open_flags *op)
3246{
3247 struct dentry *dir = nd->path.dentry;
3248 int open_flag = op->open_flag;
3249 bool got_write = false;
3250 unsigned seq;
3251 struct inode *inode;
3252 struct dentry *dentry;
3253 const char *res;
3254
3255 nd->flags |= op->intent;
3256
3257 if (nd->last_type != LAST_NORM) {
3258 if (nd->depth)
3259 put_link(nd);
3260 return handle_dots(nd, nd->last_type);
3261 }
3262
3263 if (!(open_flag & O_CREAT)) {
3264 if (nd->last.name[nd->last.len])
3265 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
3266 /* we _can_ be in RCU mode here */
3267 dentry = lookup_fast(nd, &inode, &seq);
3268 if (IS_ERR(dentry))
3269 return ERR_CAST(dentry);
3270 if (likely(dentry))
3271 goto finish_lookup;
3272
3273 BUG_ON(nd->flags & LOOKUP_RCU);
3274 } else {
3275 /* create side of things */
3276 if (nd->flags & LOOKUP_RCU) {
3277 if (!try_to_unlazy(nd))
3278 return ERR_PTR(-ECHILD);
3279 }
3280 audit_inode(nd->name, dir, AUDIT_INODE_PARENT);
3281 /* trailing slashes? */
3282 if (unlikely(nd->last.name[nd->last.len]))
3283 return ERR_PTR(-EISDIR);
3284 }
3285
3286 if (open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
3287 got_write = !mnt_want_write(nd->path.mnt);
3288 /*
3289 * do _not_ fail yet - we might not need that or fail with
3290 * a different error; let lookup_open() decide; we'll be
3291 * dropping this one anyway.
3292 */
3293 }
3294 if (open_flag & O_CREAT)
3295 inode_lock(dir->d_inode);
3296 else
3297 inode_lock_shared(dir->d_inode);
3298 dentry = lookup_open(nd, file, op, got_write);
3299 if (!IS_ERR(dentry) && (file->f_mode & FMODE_CREATED))
3300 fsnotify_create(dir->d_inode, dentry);
3301 if (open_flag & O_CREAT)
3302 inode_unlock(dir->d_inode);
3303 else
3304 inode_unlock_shared(dir->d_inode);
3305
3306 if (got_write)
3307 mnt_drop_write(nd->path.mnt);
3308
3309 if (IS_ERR(dentry))
3310 return ERR_CAST(dentry);
3311
3312 if (file->f_mode & (FMODE_OPENED | FMODE_CREATED)) {
3313 dput(nd->path.dentry);
3314 nd->path.dentry = dentry;
3315 return NULL;
3316 }
3317
3318finish_lookup:
3319 if (nd->depth)
3320 put_link(nd);
3321 res = step_into(nd, WALK_TRAILING, dentry, inode, seq);
3322 if (unlikely(res))
3323 nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
3324 return res;
3325}
3326
3327/*
3328 * Handle the last step of open()
3329 */
3330static int do_open(struct nameidata *nd,
3331 struct file *file, const struct open_flags *op)
3332{
3333 struct user_namespace *mnt_userns;
3334 int open_flag = op->open_flag;
3335 bool do_truncate;
3336 int acc_mode;
3337 int error;
3338
3339 if (!(file->f_mode & (FMODE_OPENED | FMODE_CREATED))) {
3340 error = complete_walk(nd);
3341 if (error)
3342 return error;
3343 }
3344 if (!(file->f_mode & FMODE_CREATED))
3345 audit_inode(nd->name, nd->path.dentry, 0);
3346 mnt_userns = mnt_user_ns(nd->path.mnt);
3347 if (open_flag & O_CREAT) {
3348 if ((open_flag & O_EXCL) && !(file->f_mode & FMODE_CREATED))
3349 return -EEXIST;
3350 if (d_is_dir(nd->path.dentry))
3351 return -EISDIR;
3352 error = may_create_in_sticky(mnt_userns, nd,
3353 d_backing_inode(nd->path.dentry));
3354 if (unlikely(error))
3355 return error;
3356 }
3357 if ((nd->flags & LOOKUP_DIRECTORY) && !d_can_lookup(nd->path.dentry))
3358 return -ENOTDIR;
3359
3360 do_truncate = false;
3361 acc_mode = op->acc_mode;
3362 if (file->f_mode & FMODE_CREATED) {
3363 /* Don't check for write permission, don't truncate */
3364 open_flag &= ~O_TRUNC;
3365 acc_mode = 0;
3366 } else if (d_is_reg(nd->path.dentry) && open_flag & O_TRUNC) {
3367 error = mnt_want_write(nd->path.mnt);
3368 if (error)
3369 return error;
3370 do_truncate = true;
3371 }
3372 error = may_open(mnt_userns, &nd->path, acc_mode, open_flag);
3373 if (!error && !(file->f_mode & FMODE_OPENED))
3374 error = vfs_open(&nd->path, file);
3375 if (!error)
3376 error = ima_file_check(file, op->acc_mode);
3377 if (!error && do_truncate)
3378 error = handle_truncate(mnt_userns, file);
3379 if (unlikely(error > 0)) {
3380 WARN_ON(1);
3381 error = -EINVAL;
3382 }
3383 if (do_truncate)
3384 mnt_drop_write(nd->path.mnt);
3385 return error;
3386}
3387
3388/**
3389 * vfs_tmpfile - create tmpfile
3390 * @mnt_userns: user namespace of the mount the inode was found from
3391 * @dentry: pointer to dentry of the base directory
3392 * @mode: mode of the new tmpfile
3393 * @open_flag: flags
3394 *
3395 * Create a temporary file.
3396 *
3397 * If the inode has been found through an idmapped mount the user namespace of
3398 * the vfsmount must be passed through @mnt_userns. This function will then take
3399 * care to map the inode according to @mnt_userns before checking permissions.
3400 * On non-idmapped mounts or if permission checking is to be performed on the
3401 * raw inode simply passs init_user_ns.
3402 */
3403struct dentry *vfs_tmpfile(struct user_namespace *mnt_userns,
3404 struct dentry *dentry, umode_t mode, int open_flag)
3405{
3406 struct dentry *child = NULL;
3407 struct inode *dir = dentry->d_inode;
3408 struct inode *inode;
3409 int error;
3410
3411 /* we want directory to be writable */
3412 error = inode_permission(mnt_userns, dir, MAY_WRITE | MAY_EXEC);
3413 if (error)
3414 goto out_err;
3415 error = -EOPNOTSUPP;
3416 if (!dir->i_op->tmpfile)
3417 goto out_err;
3418 error = -ENOMEM;
3419 child = d_alloc(dentry, &slash_name);
3420 if (unlikely(!child))
3421 goto out_err;
3422 error = dir->i_op->tmpfile(mnt_userns, dir, child, mode);
3423 if (error)
3424 goto out_err;
3425 error = -ENOENT;
3426 inode = child->d_inode;
3427 if (unlikely(!inode))
3428 goto out_err;
3429 if (!(open_flag & O_EXCL)) {
3430 spin_lock(&inode->i_lock);
3431 inode->i_state |= I_LINKABLE;
3432 spin_unlock(&inode->i_lock);
3433 }
3434 ima_post_create_tmpfile(mnt_userns, inode);
3435 return child;
3436
3437out_err:
3438 dput(child);
3439 return ERR_PTR(error);
3440}
3441EXPORT_SYMBOL(vfs_tmpfile);
3442
3443static int do_tmpfile(struct nameidata *nd, unsigned flags,
3444 const struct open_flags *op,
3445 struct file *file)
3446{
3447 struct user_namespace *mnt_userns;
3448 struct dentry *child;
3449 struct path path;
3450 int error = path_lookupat(nd, flags | LOOKUP_DIRECTORY, &path);
3451 if (unlikely(error))
3452 return error;
3453 error = mnt_want_write(path.mnt);
3454 if (unlikely(error))
3455 goto out;
3456 mnt_userns = mnt_user_ns(path.mnt);
3457 child = vfs_tmpfile(mnt_userns, path.dentry, op->mode, op->open_flag);
3458 error = PTR_ERR(child);
3459 if (IS_ERR(child))
3460 goto out2;
3461 dput(path.dentry);
3462 path.dentry = child;
3463 audit_inode(nd->name, child, 0);
3464 /* Don't check for other permissions, the inode was just created */
3465 error = may_open(mnt_userns, &path, 0, op->open_flag);
3466 if (!error)
3467 error = vfs_open(&path, file);
3468out2:
3469 mnt_drop_write(path.mnt);
3470out:
3471 path_put(&path);
3472 return error;
3473}
3474
3475static int do_o_path(struct nameidata *nd, unsigned flags, struct file *file)
3476{
3477 struct path path;
3478 int error = path_lookupat(nd, flags, &path);
3479 if (!error) {
3480 audit_inode(nd->name, path.dentry, 0);
3481 error = vfs_open(&path, file);
3482 path_put(&path);
3483 }
3484 return error;
3485}
3486
3487static struct file *path_openat(struct nameidata *nd,
3488 const struct open_flags *op, unsigned flags)
3489{
3490 struct file *file;
3491 int error;
3492
3493 file = alloc_empty_file(op->open_flag, current_cred());
3494 if (IS_ERR(file))
3495 return file;
3496
3497 if (unlikely(file->f_flags & __O_TMPFILE)) {
3498 error = do_tmpfile(nd, flags, op, file);
3499 } else if (unlikely(file->f_flags & O_PATH)) {
3500 error = do_o_path(nd, flags, file);
3501 } else {
3502 const char *s = path_init(nd, flags);
3503 while (!(error = link_path_walk(s, nd)) &&
3504 (s = open_last_lookups(nd, file, op)) != NULL)
3505 ;
3506 if (!error)
3507 error = do_open(nd, file, op);
3508 terminate_walk(nd);
3509 }
3510 if (likely(!error)) {
3511 if (likely(file->f_mode & FMODE_OPENED))
3512 return file;
3513 WARN_ON(1);
3514 error = -EINVAL;
3515 }
3516 fput(file);
3517 if (error == -EOPENSTALE) {
3518 if (flags & LOOKUP_RCU)
3519 error = -ECHILD;
3520 else
3521 error = -ESTALE;
3522 }
3523 return ERR_PTR(error);
3524}
3525
3526struct file *do_filp_open(int dfd, struct filename *pathname,
3527 const struct open_flags *op)
3528{
3529 struct nameidata nd;
3530 int flags = op->lookup_flags;
3531 struct file *filp;
3532
3533 set_nameidata(&nd, dfd, pathname, NULL);
3534 filp = path_openat(&nd, op, flags | LOOKUP_RCU);
3535 if (unlikely(filp == ERR_PTR(-ECHILD)))
3536 filp = path_openat(&nd, op, flags);
3537 if (unlikely(filp == ERR_PTR(-ESTALE)))
3538 filp = path_openat(&nd, op, flags | LOOKUP_REVAL);
3539 restore_nameidata();
3540 return filp;
3541}
3542
3543struct file *do_file_open_root(const struct path *root,
3544 const char *name, const struct open_flags *op)
3545{
3546 struct nameidata nd;
3547 struct file *file;
3548 struct filename *filename;
3549 int flags = op->lookup_flags;
3550
3551 if (d_is_symlink(root->dentry) && op->intent & LOOKUP_OPEN)
3552 return ERR_PTR(-ELOOP);
3553
3554 filename = getname_kernel(name);
3555 if (IS_ERR(filename))
3556 return ERR_CAST(filename);
3557
3558 set_nameidata(&nd, -1, filename, root);
3559 file = path_openat(&nd, op, flags | LOOKUP_RCU);
3560 if (unlikely(file == ERR_PTR(-ECHILD)))
3561 file = path_openat(&nd, op, flags);
3562 if (unlikely(file == ERR_PTR(-ESTALE)))
3563 file = path_openat(&nd, op, flags | LOOKUP_REVAL);
3564 restore_nameidata();
3565 putname(filename);
3566 return file;
3567}
3568
3569static struct dentry *filename_create(int dfd, struct filename *name,
3570 struct path *path, unsigned int lookup_flags)
3571{
3572 struct dentry *dentry = ERR_PTR(-EEXIST);
3573 struct qstr last;
3574 int type;
3575 int err2;
3576 int error;
3577 bool is_dir = (lookup_flags & LOOKUP_DIRECTORY);
3578
3579 /*
3580 * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any
3581 * other flags passed in are ignored!
3582 */
3583 lookup_flags &= LOOKUP_REVAL;
3584
3585 name = filename_parentat(dfd, name, lookup_flags, path, &last, &type);
3586 if (IS_ERR(name))
3587 return ERR_CAST(name);
3588
3589 /*
3590 * Yucky last component or no last component at all?
3591 * (foo/., foo/.., /////)
3592 */
3593 if (unlikely(type != LAST_NORM))
3594 goto out;
3595
3596 /* don't fail immediately if it's r/o, at least try to report other errors */
3597 err2 = mnt_want_write(path->mnt);
3598 /*
3599 * Do the final lookup.
3600 */
3601 lookup_flags |= LOOKUP_CREATE | LOOKUP_EXCL;
3602 inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
3603 dentry = __lookup_hash(&last, path->dentry, lookup_flags);
3604 if (IS_ERR(dentry))
3605 goto unlock;
3606
3607 error = -EEXIST;
3608 if (d_is_positive(dentry))
3609 goto fail;
3610
3611 /*
3612 * Special case - lookup gave negative, but... we had foo/bar/
3613 * From the vfs_mknod() POV we just have a negative dentry -
3614 * all is fine. Let's be bastards - you had / on the end, you've
3615 * been asking for (non-existent) directory. -ENOENT for you.
3616 */
3617 if (unlikely(!is_dir && last.name[last.len])) {
3618 error = -ENOENT;
3619 goto fail;
3620 }
3621 if (unlikely(err2)) {
3622 error = err2;
3623 goto fail;
3624 }
3625 putname(name);
3626 return dentry;
3627fail:
3628 dput(dentry);
3629 dentry = ERR_PTR(error);
3630unlock:
3631 inode_unlock(path->dentry->d_inode);
3632 if (!err2)
3633 mnt_drop_write(path->mnt);
3634out:
3635 path_put(path);
3636 putname(name);
3637 return dentry;
3638}
3639
3640struct dentry *kern_path_create(int dfd, const char *pathname,
3641 struct path *path, unsigned int lookup_flags)
3642{
3643 return filename_create(dfd, getname_kernel(pathname),
3644 path, lookup_flags);
3645}
3646EXPORT_SYMBOL(kern_path_create);
3647
3648void done_path_create(struct path *path, struct dentry *dentry)
3649{
3650 dput(dentry);
3651 inode_unlock(path->dentry->d_inode);
3652 mnt_drop_write(path->mnt);
3653 path_put(path);
3654}
3655EXPORT_SYMBOL(done_path_create);
3656
3657inline struct dentry *user_path_create(int dfd, const char __user *pathname,
3658 struct path *path, unsigned int lookup_flags)
3659{
3660 return filename_create(dfd, getname(pathname), path, lookup_flags);
3661}
3662EXPORT_SYMBOL(user_path_create);
3663
3664/**
3665 * vfs_mknod - create device node or file
3666 * @mnt_userns: user namespace of the mount the inode was found from
3667 * @dir: inode of @dentry
3668 * @dentry: pointer to dentry of the base directory
3669 * @mode: mode of the new device node or file
3670 * @dev: device number of device to create
3671 *
3672 * Create a device node or file.
3673 *
3674 * If the inode has been found through an idmapped mount the user namespace of
3675 * the vfsmount must be passed through @mnt_userns. This function will then take
3676 * care to map the inode according to @mnt_userns before checking permissions.
3677 * On non-idmapped mounts or if permission checking is to be performed on the
3678 * raw inode simply passs init_user_ns.
3679 */
3680int vfs_mknod(struct user_namespace *mnt_userns, struct inode *dir,
3681 struct dentry *dentry, umode_t mode, dev_t dev)
3682{
3683 bool is_whiteout = S_ISCHR(mode) && dev == WHITEOUT_DEV;
3684 int error = may_create(mnt_userns, dir, dentry);
3685
3686 if (error)
3687 return error;
3688
3689 if ((S_ISCHR(mode) || S_ISBLK(mode)) && !is_whiteout &&
3690 !capable(CAP_MKNOD))
3691 return -EPERM;
3692
3693 if (!dir->i_op->mknod)
3694 return -EPERM;
3695
3696 error = devcgroup_inode_mknod(mode, dev);
3697 if (error)
3698 return error;
3699
3700 error = security_inode_mknod(dir, dentry, mode, dev);
3701 if (error)
3702 return error;
3703
3704 error = dir->i_op->mknod(mnt_userns, dir, dentry, mode, dev);
3705 if (!error)
3706 fsnotify_create(dir, dentry);
3707 return error;
3708}
3709EXPORT_SYMBOL(vfs_mknod);
3710
3711static int may_mknod(umode_t mode)
3712{
3713 switch (mode & S_IFMT) {
3714 case S_IFREG:
3715 case S_IFCHR:
3716 case S_IFBLK:
3717 case S_IFIFO:
3718 case S_IFSOCK:
3719 case 0: /* zero mode translates to S_IFREG */
3720 return 0;
3721 case S_IFDIR:
3722 return -EPERM;
3723 default:
3724 return -EINVAL;
3725 }
3726}
3727
3728static long do_mknodat(int dfd, const char __user *filename, umode_t mode,
3729 unsigned int dev)
3730{
3731 struct user_namespace *mnt_userns;
3732 struct dentry *dentry;
3733 struct path path;
3734 int error;
3735 unsigned int lookup_flags = 0;
3736
3737 error = may_mknod(mode);
3738 if (error)
3739 return error;
3740retry:
3741 dentry = user_path_create(dfd, filename, &path, lookup_flags);
3742 if (IS_ERR(dentry))
3743 return PTR_ERR(dentry);
3744
3745 if (!IS_POSIXACL(path.dentry->d_inode))
3746 mode &= ~current_umask();
3747 error = security_path_mknod(&path, dentry, mode, dev);
3748 if (error)
3749 goto out;
3750
3751 mnt_userns = mnt_user_ns(path.mnt);
3752 switch (mode & S_IFMT) {
3753 case 0: case S_IFREG:
3754 error = vfs_create(mnt_userns, path.dentry->d_inode,
3755 dentry, mode, true);
3756 if (!error)
3757 ima_post_path_mknod(mnt_userns, dentry);
3758 break;
3759 case S_IFCHR: case S_IFBLK:
3760 error = vfs_mknod(mnt_userns, path.dentry->d_inode,
3761 dentry, mode, new_decode_dev(dev));
3762 break;
3763 case S_IFIFO: case S_IFSOCK:
3764 error = vfs_mknod(mnt_userns, path.dentry->d_inode,
3765 dentry, mode, 0);
3766 break;
3767 }
3768out:
3769 done_path_create(&path, dentry);
3770 if (retry_estale(error, lookup_flags)) {
3771 lookup_flags |= LOOKUP_REVAL;
3772 goto retry;
3773 }
3774 return error;
3775}
3776
3777SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,
3778 unsigned int, dev)
3779{
3780 return do_mknodat(dfd, filename, mode, dev);
3781}
3782
3783SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev)
3784{
3785 return do_mknodat(AT_FDCWD, filename, mode, dev);
3786}
3787
3788/**
3789 * vfs_mkdir - create directory
3790 * @mnt_userns: user namespace of the mount the inode was found from
3791 * @dir: inode of @dentry
3792 * @dentry: pointer to dentry of the base directory
3793 * @mode: mode of the new directory
3794 *
3795 * Create a directory.
3796 *
3797 * If the inode has been found through an idmapped mount the user namespace of
3798 * the vfsmount must be passed through @mnt_userns. This function will then take
3799 * care to map the inode according to @mnt_userns before checking permissions.
3800 * On non-idmapped mounts or if permission checking is to be performed on the
3801 * raw inode simply passs init_user_ns.
3802 */
3803int vfs_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
3804 struct dentry *dentry, umode_t mode)
3805{
3806 int error = may_create(mnt_userns, dir, dentry);
3807 unsigned max_links = dir->i_sb->s_max_links;
3808
3809 if (error)
3810 return error;
3811
3812 if (!dir->i_op->mkdir)
3813 return -EPERM;
3814
3815 mode &= (S_IRWXUGO|S_ISVTX);
3816 error = security_inode_mkdir(dir, dentry, mode);
3817 if (error)
3818 return error;
3819
3820 if (max_links && dir->i_nlink >= max_links)
3821 return -EMLINK;
3822
3823 error = dir->i_op->mkdir(mnt_userns, dir, dentry, mode);
3824 if (!error)
3825 fsnotify_mkdir(dir, dentry);
3826 return error;
3827}
3828EXPORT_SYMBOL(vfs_mkdir);
3829
3830static long do_mkdirat(int dfd, const char __user *pathname, umode_t mode)
3831{
3832 struct dentry *dentry;
3833 struct path path;
3834 int error;
3835 unsigned int lookup_flags = LOOKUP_DIRECTORY;
3836
3837retry:
3838 dentry = user_path_create(dfd, pathname, &path, lookup_flags);
3839 if (IS_ERR(dentry))
3840 return PTR_ERR(dentry);
3841
3842 if (!IS_POSIXACL(path.dentry->d_inode))
3843 mode &= ~current_umask();
3844 error = security_path_mkdir(&path, dentry, mode);
3845 if (!error) {
3846 struct user_namespace *mnt_userns;
3847 mnt_userns = mnt_user_ns(path.mnt);
3848 error = vfs_mkdir(mnt_userns, path.dentry->d_inode, dentry,
3849 mode);
3850 }
3851 done_path_create(&path, dentry);
3852 if (retry_estale(error, lookup_flags)) {
3853 lookup_flags |= LOOKUP_REVAL;
3854 goto retry;
3855 }
3856 return error;
3857}
3858
3859SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
3860{
3861 return do_mkdirat(dfd, pathname, mode);
3862}
3863
3864SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode)
3865{
3866 return do_mkdirat(AT_FDCWD, pathname, mode);
3867}
3868
3869/**
3870 * vfs_rmdir - remove directory
3871 * @mnt_userns: user namespace of the mount the inode was found from
3872 * @dir: inode of @dentry
3873 * @dentry: pointer to dentry of the base directory
3874 *
3875 * Remove a directory.
3876 *
3877 * If the inode has been found through an idmapped mount the user namespace of
3878 * the vfsmount must be passed through @mnt_userns. This function will then take
3879 * care to map the inode according to @mnt_userns before checking permissions.
3880 * On non-idmapped mounts or if permission checking is to be performed on the
3881 * raw inode simply passs init_user_ns.
3882 */
3883int vfs_rmdir(struct user_namespace *mnt_userns, struct inode *dir,
3884 struct dentry *dentry)
3885{
3886 int error = may_delete(mnt_userns, dir, dentry, 1);
3887
3888 if (error)
3889 return error;
3890
3891 if (!dir->i_op->rmdir)
3892 return -EPERM;
3893
3894 dget(dentry);
3895 inode_lock(dentry->d_inode);
3896
3897 error = -EBUSY;
3898 if (is_local_mountpoint(dentry))
3899 goto out;
3900
3901 error = security_inode_rmdir(dir, dentry);
3902 if (error)
3903 goto out;
3904
3905 error = dir->i_op->rmdir(dir, dentry);
3906 if (error)
3907 goto out;
3908
3909 shrink_dcache_parent(dentry);
3910 dentry->d_inode->i_flags |= S_DEAD;
3911 dont_mount(dentry);
3912 detach_mounts(dentry);
3913 fsnotify_rmdir(dir, dentry);
3914
3915out:
3916 inode_unlock(dentry->d_inode);
3917 dput(dentry);
3918 if (!error)
3919 d_delete(dentry);
3920 return error;
3921}
3922EXPORT_SYMBOL(vfs_rmdir);
3923
3924long do_rmdir(int dfd, struct filename *name)
3925{
3926 struct user_namespace *mnt_userns;
3927 int error = 0;
3928 struct dentry *dentry;
3929 struct path path;
3930 struct qstr last;
3931 int type;
3932 unsigned int lookup_flags = 0;
3933retry:
3934 name = filename_parentat(dfd, name, lookup_flags,
3935 &path, &last, &type);
3936 if (IS_ERR(name))
3937 return PTR_ERR(name);
3938
3939 switch (type) {
3940 case LAST_DOTDOT:
3941 error = -ENOTEMPTY;
3942 goto exit1;
3943 case LAST_DOT:
3944 error = -EINVAL;
3945 goto exit1;
3946 case LAST_ROOT:
3947 error = -EBUSY;
3948 goto exit1;
3949 }
3950
3951 error = mnt_want_write(path.mnt);
3952 if (error)
3953 goto exit1;
3954
3955 inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT);
3956 dentry = __lookup_hash(&last, path.dentry, lookup_flags);
3957 error = PTR_ERR(dentry);
3958 if (IS_ERR(dentry))
3959 goto exit2;
3960 if (!dentry->d_inode) {
3961 error = -ENOENT;
3962 goto exit3;
3963 }
3964 error = security_path_rmdir(&path, dentry);
3965 if (error)
3966 goto exit3;
3967 mnt_userns = mnt_user_ns(path.mnt);
3968 error = vfs_rmdir(mnt_userns, path.dentry->d_inode, dentry);
3969exit3:
3970 dput(dentry);
3971exit2:
3972 inode_unlock(path.dentry->d_inode);
3973 mnt_drop_write(path.mnt);
3974exit1:
3975 path_put(&path);
3976 if (retry_estale(error, lookup_flags)) {
3977 lookup_flags |= LOOKUP_REVAL;
3978 goto retry;
3979 }
3980 putname(name);
3981 return error;
3982}
3983
3984SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
3985{
3986 return do_rmdir(AT_FDCWD, getname(pathname));
3987}
3988
3989/**
3990 * vfs_unlink - unlink a filesystem object
3991 * @mnt_userns: user namespace of the mount the inode was found from
3992 * @dir: parent directory
3993 * @dentry: victim
3994 * @delegated_inode: returns victim inode, if the inode is delegated.
3995 *
3996 * The caller must hold dir->i_mutex.
3997 *
3998 * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and
3999 * return a reference to the inode in delegated_inode. The caller
4000 * should then break the delegation on that inode and retry. Because
4001 * breaking a delegation may take a long time, the caller should drop
4002 * dir->i_mutex before doing so.
4003 *
4004 * Alternatively, a caller may pass NULL for delegated_inode. This may
4005 * be appropriate for callers that expect the underlying filesystem not
4006 * to be NFS exported.
4007 *
4008 * If the inode has been found through an idmapped mount the user namespace of
4009 * the vfsmount must be passed through @mnt_userns. This function will then take
4010 * care to map the inode according to @mnt_userns before checking permissions.
4011 * On non-idmapped mounts or if permission checking is to be performed on the
4012 * raw inode simply passs init_user_ns.
4013 */
4014int vfs_unlink(struct user_namespace *mnt_userns, struct inode *dir,
4015 struct dentry *dentry, struct inode **delegated_inode)
4016{
4017 struct inode *target = dentry->d_inode;
4018 int error = may_delete(mnt_userns, dir, dentry, 0);
4019
4020 if (error)
4021 return error;
4022
4023 if (!dir->i_op->unlink)
4024 return -EPERM;
4025
4026 inode_lock(target);
4027 if (is_local_mountpoint(dentry))
4028 error = -EBUSY;
4029 else {
4030 error = security_inode_unlink(dir, dentry);
4031 if (!error) {
4032 error = try_break_deleg(target, delegated_inode);
4033 if (error)
4034 goto out;
4035 error = dir->i_op->unlink(dir, dentry);
4036 if (!error) {
4037 dont_mount(dentry);
4038 detach_mounts(dentry);
4039 fsnotify_unlink(dir, dentry);
4040 }
4041 }
4042 }
4043out:
4044 inode_unlock(target);
4045
4046 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
4047 if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
4048 fsnotify_link_count(target);
4049 d_delete(dentry);
4050 }
4051
4052 return error;
4053}
4054EXPORT_SYMBOL(vfs_unlink);
4055
4056/*
4057 * Make sure that the actual truncation of the file will occur outside its
4058 * directory's i_mutex. Truncate can take a long time if there is a lot of
4059 * writeout happening, and we don't want to prevent access to the directory
4060 * while waiting on the I/O.
4061 */
4062long do_unlinkat(int dfd, struct filename *name)
4063{
4064 int error;
4065 struct dentry *dentry;
4066 struct path path;
4067 struct qstr last;
4068 int type;
4069 struct inode *inode = NULL;
4070 struct inode *delegated_inode = NULL;
4071 unsigned int lookup_flags = 0;
4072retry:
4073 name = filename_parentat(dfd, name, lookup_flags, &path, &last, &type);
4074 if (IS_ERR(name))
4075 return PTR_ERR(name);
4076
4077 error = -EISDIR;
4078 if (type != LAST_NORM)
4079 goto exit1;
4080
4081 error = mnt_want_write(path.mnt);
4082 if (error)
4083 goto exit1;
4084retry_deleg:
4085 inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT);
4086 dentry = __lookup_hash(&last, path.dentry, lookup_flags);
4087 error = PTR_ERR(dentry);
4088 if (!IS_ERR(dentry)) {
4089 struct user_namespace *mnt_userns;
4090
4091 /* Why not before? Because we want correct error value */
4092 if (last.name[last.len])
4093 goto slashes;
4094 inode = dentry->d_inode;
4095 if (d_is_negative(dentry))
4096 goto slashes;
4097 ihold(inode);
4098 error = security_path_unlink(&path, dentry);
4099 if (error)
4100 goto exit2;
4101 mnt_userns = mnt_user_ns(path.mnt);
4102 error = vfs_unlink(mnt_userns, path.dentry->d_inode, dentry,
4103 &delegated_inode);
4104exit2:
4105 dput(dentry);
4106 }
4107 inode_unlock(path.dentry->d_inode);
4108 if (inode)
4109 iput(inode); /* truncate the inode here */
4110 inode = NULL;
4111 if (delegated_inode) {
4112 error = break_deleg_wait(&delegated_inode);
4113 if (!error)
4114 goto retry_deleg;
4115 }
4116 mnt_drop_write(path.mnt);
4117exit1:
4118 path_put(&path);
4119 if (retry_estale(error, lookup_flags)) {
4120 lookup_flags |= LOOKUP_REVAL;
4121 inode = NULL;
4122 goto retry;
4123 }
4124 putname(name);
4125 return error;
4126
4127slashes:
4128 if (d_is_negative(dentry))
4129 error = -ENOENT;
4130 else if (d_is_dir(dentry))
4131 error = -EISDIR;
4132 else
4133 error = -ENOTDIR;
4134 goto exit2;
4135}
4136
4137SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
4138{
4139 if ((flag & ~AT_REMOVEDIR) != 0)
4140 return -EINVAL;
4141
4142 if (flag & AT_REMOVEDIR)
4143 return do_rmdir(dfd, getname(pathname));
4144 return do_unlinkat(dfd, getname(pathname));
4145}
4146
4147SYSCALL_DEFINE1(unlink, const char __user *, pathname)
4148{
4149 return do_unlinkat(AT_FDCWD, getname(pathname));
4150}
4151
4152/**
4153 * vfs_symlink - create symlink
4154 * @mnt_userns: user namespace of the mount the inode was found from
4155 * @dir: inode of @dentry
4156 * @dentry: pointer to dentry of the base directory
4157 * @oldname: name of the file to link to
4158 *
4159 * Create a symlink.
4160 *
4161 * If the inode has been found through an idmapped mount the user namespace of
4162 * the vfsmount must be passed through @mnt_userns. This function will then take
4163 * care to map the inode according to @mnt_userns before checking permissions.
4164 * On non-idmapped mounts or if permission checking is to be performed on the
4165 * raw inode simply passs init_user_ns.
4166 */
4167int vfs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
4168 struct dentry *dentry, const char *oldname)
4169{
4170 int error = may_create(mnt_userns, dir, dentry);
4171
4172 if (error)
4173 return error;
4174
4175 if (!dir->i_op->symlink)
4176 return -EPERM;
4177
4178 error = security_inode_symlink(dir, dentry, oldname);
4179 if (error)
4180 return error;
4181
4182 error = dir->i_op->symlink(mnt_userns, dir, dentry, oldname);
4183 if (!error)
4184 fsnotify_create(dir, dentry);
4185 return error;
4186}
4187EXPORT_SYMBOL(vfs_symlink);
4188
4189static long do_symlinkat(const char __user *oldname, int newdfd,
4190 const char __user *newname)
4191{
4192 int error;
4193 struct filename *from;
4194 struct dentry *dentry;
4195 struct path path;
4196 unsigned int lookup_flags = 0;
4197
4198 from = getname(oldname);
4199 if (IS_ERR(from))
4200 return PTR_ERR(from);
4201retry:
4202 dentry = user_path_create(newdfd, newname, &path, lookup_flags);
4203 error = PTR_ERR(dentry);
4204 if (IS_ERR(dentry))
4205 goto out_putname;
4206
4207 error = security_path_symlink(&path, dentry, from->name);
4208 if (!error) {
4209 struct user_namespace *mnt_userns;
4210
4211 mnt_userns = mnt_user_ns(path.mnt);
4212 error = vfs_symlink(mnt_userns, path.dentry->d_inode, dentry,
4213 from->name);
4214 }
4215 done_path_create(&path, dentry);
4216 if (retry_estale(error, lookup_flags)) {
4217 lookup_flags |= LOOKUP_REVAL;
4218 goto retry;
4219 }
4220out_putname:
4221 putname(from);
4222 return error;
4223}
4224
4225SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
4226 int, newdfd, const char __user *, newname)
4227{
4228 return do_symlinkat(oldname, newdfd, newname);
4229}
4230
4231SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
4232{
4233 return do_symlinkat(oldname, AT_FDCWD, newname);
4234}
4235
4236/**
4237 * vfs_link - create a new link
4238 * @old_dentry: object to be linked
4239 * @mnt_userns: the user namespace of the mount
4240 * @dir: new parent
4241 * @new_dentry: where to create the new link
4242 * @delegated_inode: returns inode needing a delegation break
4243 *
4244 * The caller must hold dir->i_mutex
4245 *
4246 * If vfs_link discovers a delegation on the to-be-linked file in need
4247 * of breaking, it will return -EWOULDBLOCK and return a reference to the
4248 * inode in delegated_inode. The caller should then break the delegation
4249 * and retry. Because breaking a delegation may take a long time, the
4250 * caller should drop the i_mutex before doing so.
4251 *
4252 * Alternatively, a caller may pass NULL for delegated_inode. This may
4253 * be appropriate for callers that expect the underlying filesystem not
4254 * to be NFS exported.
4255 *
4256 * If the inode has been found through an idmapped mount the user namespace of
4257 * the vfsmount must be passed through @mnt_userns. This function will then take
4258 * care to map the inode according to @mnt_userns before checking permissions.
4259 * On non-idmapped mounts or if permission checking is to be performed on the
4260 * raw inode simply passs init_user_ns.
4261 */
4262int vfs_link(struct dentry *old_dentry, struct user_namespace *mnt_userns,
4263 struct inode *dir, struct dentry *new_dentry,
4264 struct inode **delegated_inode)
4265{
4266 struct inode *inode = old_dentry->d_inode;
4267 unsigned max_links = dir->i_sb->s_max_links;
4268 int error;
4269
4270 if (!inode)
4271 return -ENOENT;
4272
4273 error = may_create(mnt_userns, dir, new_dentry);
4274 if (error)
4275 return error;
4276
4277 if (dir->i_sb != inode->i_sb)
4278 return -EXDEV;
4279
4280 /*
4281 * A link to an append-only or immutable file cannot be created.
4282 */
4283 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
4284 return -EPERM;
4285 /*
4286 * Updating the link count will likely cause i_uid and i_gid to
4287 * be writen back improperly if their true value is unknown to
4288 * the vfs.
4289 */
4290 if (HAS_UNMAPPED_ID(mnt_userns, inode))
4291 return -EPERM;
4292 if (!dir->i_op->link)
4293 return -EPERM;
4294 if (S_ISDIR(inode->i_mode))
4295 return -EPERM;
4296
4297 error = security_inode_link(old_dentry, dir, new_dentry);
4298 if (error)
4299 return error;
4300
4301 inode_lock(inode);
4302 /* Make sure we don't allow creating hardlink to an unlinked file */
4303 if (inode->i_nlink == 0 && !(inode->i_state & I_LINKABLE))
4304 error = -ENOENT;
4305 else if (max_links && inode->i_nlink >= max_links)
4306 error = -EMLINK;
4307 else {
4308 error = try_break_deleg(inode, delegated_inode);
4309 if (!error)
4310 error = dir->i_op->link(old_dentry, dir, new_dentry);
4311 }
4312
4313 if (!error && (inode->i_state & I_LINKABLE)) {
4314 spin_lock(&inode->i_lock);
4315 inode->i_state &= ~I_LINKABLE;
4316 spin_unlock(&inode->i_lock);
4317 }
4318 inode_unlock(inode);
4319 if (!error)
4320 fsnotify_link(dir, inode, new_dentry);
4321 return error;
4322}
4323EXPORT_SYMBOL(vfs_link);
4324
4325/*
4326 * Hardlinks are often used in delicate situations. We avoid
4327 * security-related surprises by not following symlinks on the
4328 * newname. --KAB
4329 *
4330 * We don't follow them on the oldname either to be compatible
4331 * with linux 2.0, and to avoid hard-linking to directories
4332 * and other special files. --ADM
4333 */
4334static int do_linkat(int olddfd, const char __user *oldname, int newdfd,
4335 const char __user *newname, int flags)
4336{
4337 struct user_namespace *mnt_userns;
4338 struct dentry *new_dentry;
4339 struct path old_path, new_path;
4340 struct inode *delegated_inode = NULL;
4341 int how = 0;
4342 int error;
4343
4344 if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
4345 return -EINVAL;
4346 /*
4347 * To use null names we require CAP_DAC_READ_SEARCH
4348 * This ensures that not everyone will be able to create
4349 * handlink using the passed filedescriptor.
4350 */
4351 if (flags & AT_EMPTY_PATH) {
4352 if (!capable(CAP_DAC_READ_SEARCH))
4353 return -ENOENT;
4354 how = LOOKUP_EMPTY;
4355 }
4356
4357 if (flags & AT_SYMLINK_FOLLOW)
4358 how |= LOOKUP_FOLLOW;
4359retry:
4360 error = user_path_at(olddfd, oldname, how, &old_path);
4361 if (error)
4362 return error;
4363
4364 new_dentry = user_path_create(newdfd, newname, &new_path,
4365 (how & LOOKUP_REVAL));
4366 error = PTR_ERR(new_dentry);
4367 if (IS_ERR(new_dentry))
4368 goto out;
4369
4370 error = -EXDEV;
4371 if (old_path.mnt != new_path.mnt)
4372 goto out_dput;
4373 mnt_userns = mnt_user_ns(new_path.mnt);
4374 error = may_linkat(mnt_userns, &old_path);
4375 if (unlikely(error))
4376 goto out_dput;
4377 error = security_path_link(old_path.dentry, &new_path, new_dentry);
4378 if (error)
4379 goto out_dput;
4380 error = vfs_link(old_path.dentry, mnt_userns, new_path.dentry->d_inode,
4381 new_dentry, &delegated_inode);
4382out_dput:
4383 done_path_create(&new_path, new_dentry);
4384 if (delegated_inode) {
4385 error = break_deleg_wait(&delegated_inode);
4386 if (!error) {
4387 path_put(&old_path);
4388 goto retry;
4389 }
4390 }
4391 if (retry_estale(error, how)) {
4392 path_put(&old_path);
4393 how |= LOOKUP_REVAL;
4394 goto retry;
4395 }
4396out:
4397 path_put(&old_path);
4398
4399 return error;
4400}
4401
4402SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
4403 int, newdfd, const char __user *, newname, int, flags)
4404{
4405 return do_linkat(olddfd, oldname, newdfd, newname, flags);
4406}
4407
4408SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
4409{
4410 return do_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
4411}
4412
4413/**
4414 * vfs_rename - rename a filesystem object
4415 * @rd: pointer to &struct renamedata info
4416 *
4417 * The caller must hold multiple mutexes--see lock_rename()).
4418 *
4419 * If vfs_rename discovers a delegation in need of breaking at either
4420 * the source or destination, it will return -EWOULDBLOCK and return a
4421 * reference to the inode in delegated_inode. The caller should then
4422 * break the delegation and retry. Because breaking a delegation may
4423 * take a long time, the caller should drop all locks before doing
4424 * so.
4425 *
4426 * Alternatively, a caller may pass NULL for delegated_inode. This may
4427 * be appropriate for callers that expect the underlying filesystem not
4428 * to be NFS exported.
4429 *
4430 * The worst of all namespace operations - renaming directory. "Perverted"
4431 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
4432 * Problems:
4433 *
4434 * a) we can get into loop creation.
4435 * b) race potential - two innocent renames can create a loop together.
4436 * That's where 4.4 screws up. Current fix: serialization on
4437 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
4438 * story.
4439 * c) we have to lock _four_ objects - parents and victim (if it exists),
4440 * and source (if it is not a directory).
4441 * And that - after we got ->i_mutex on parents (until then we don't know
4442 * whether the target exists). Solution: try to be smart with locking
4443 * order for inodes. We rely on the fact that tree topology may change
4444 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
4445 * move will be locked. Thus we can rank directories by the tree
4446 * (ancestors first) and rank all non-directories after them.
4447 * That works since everybody except rename does "lock parent, lookup,
4448 * lock child" and rename is under ->s_vfs_rename_mutex.
4449 * HOWEVER, it relies on the assumption that any object with ->lookup()
4450 * has no more than 1 dentry. If "hybrid" objects will ever appear,
4451 * we'd better make sure that there's no link(2) for them.
4452 * d) conversion from fhandle to dentry may come in the wrong moment - when
4453 * we are removing the target. Solution: we will have to grab ->i_mutex
4454 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
4455 * ->i_mutex on parents, which works but leads to some truly excessive
4456 * locking].
4457 */
4458int vfs_rename(struct renamedata *rd)
4459{
4460 int error;
4461 struct inode *old_dir = rd->old_dir, *new_dir = rd->new_dir;
4462 struct dentry *old_dentry = rd->old_dentry;
4463 struct dentry *new_dentry = rd->new_dentry;
4464 struct inode **delegated_inode = rd->delegated_inode;
4465 unsigned int flags = rd->flags;
4466 bool is_dir = d_is_dir(old_dentry);
4467 struct inode *source = old_dentry->d_inode;
4468 struct inode *target = new_dentry->d_inode;
4469 bool new_is_dir = false;
4470 unsigned max_links = new_dir->i_sb->s_max_links;
4471 struct name_snapshot old_name;
4472
4473 if (source == target)
4474 return 0;
4475
4476 error = may_delete(rd->old_mnt_userns, old_dir, old_dentry, is_dir);
4477 if (error)
4478 return error;
4479
4480 if (!target) {
4481 error = may_create(rd->new_mnt_userns, new_dir, new_dentry);
4482 } else {
4483 new_is_dir = d_is_dir(new_dentry);
4484
4485 if (!(flags & RENAME_EXCHANGE))
4486 error = may_delete(rd->new_mnt_userns, new_dir,
4487 new_dentry, is_dir);
4488 else
4489 error = may_delete(rd->new_mnt_userns, new_dir,
4490 new_dentry, new_is_dir);
4491 }
4492 if (error)
4493 return error;
4494
4495 if (!old_dir->i_op->rename)
4496 return -EPERM;
4497
4498 /*
4499 * If we are going to change the parent - check write permissions,
4500 * we'll need to flip '..'.
4501 */
4502 if (new_dir != old_dir) {
4503 if (is_dir) {
4504 error = inode_permission(rd->old_mnt_userns, source,
4505 MAY_WRITE);
4506 if (error)
4507 return error;
4508 }
4509 if ((flags & RENAME_EXCHANGE) && new_is_dir) {
4510 error = inode_permission(rd->new_mnt_userns, target,
4511 MAY_WRITE);
4512 if (error)
4513 return error;
4514 }
4515 }
4516
4517 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry,
4518 flags);
4519 if (error)
4520 return error;
4521
4522 take_dentry_name_snapshot(&old_name, old_dentry);
4523 dget(new_dentry);
4524 if (!is_dir || (flags & RENAME_EXCHANGE))
4525 lock_two_nondirectories(source, target);
4526 else if (target)
4527 inode_lock(target);
4528
4529 error = -EBUSY;
4530 if (is_local_mountpoint(old_dentry) || is_local_mountpoint(new_dentry))
4531 goto out;
4532
4533 if (max_links && new_dir != old_dir) {
4534 error = -EMLINK;
4535 if (is_dir && !new_is_dir && new_dir->i_nlink >= max_links)
4536 goto out;
4537 if ((flags & RENAME_EXCHANGE) && !is_dir && new_is_dir &&
4538 old_dir->i_nlink >= max_links)
4539 goto out;
4540 }
4541 if (!is_dir) {
4542 error = try_break_deleg(source, delegated_inode);
4543 if (error)
4544 goto out;
4545 }
4546 if (target && !new_is_dir) {
4547 error = try_break_deleg(target, delegated_inode);
4548 if (error)
4549 goto out;
4550 }
4551 error = old_dir->i_op->rename(rd->new_mnt_userns, old_dir, old_dentry,
4552 new_dir, new_dentry, flags);
4553 if (error)
4554 goto out;
4555
4556 if (!(flags & RENAME_EXCHANGE) && target) {
4557 if (is_dir) {
4558 shrink_dcache_parent(new_dentry);
4559 target->i_flags |= S_DEAD;
4560 }
4561 dont_mount(new_dentry);
4562 detach_mounts(new_dentry);
4563 }
4564 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) {
4565 if (!(flags & RENAME_EXCHANGE))
4566 d_move(old_dentry, new_dentry);
4567 else
4568 d_exchange(old_dentry, new_dentry);
4569 }
4570out:
4571 if (!is_dir || (flags & RENAME_EXCHANGE))
4572 unlock_two_nondirectories(source, target);
4573 else if (target)
4574 inode_unlock(target);
4575 dput(new_dentry);
4576 if (!error) {
4577 fsnotify_move(old_dir, new_dir, &old_name.name, is_dir,
4578 !(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry);
4579 if (flags & RENAME_EXCHANGE) {
4580 fsnotify_move(new_dir, old_dir, &old_dentry->d_name,
4581 new_is_dir, NULL, new_dentry);
4582 }
4583 }
4584 release_dentry_name_snapshot(&old_name);
4585
4586 return error;
4587}
4588EXPORT_SYMBOL(vfs_rename);
4589
4590int do_renameat2(int olddfd, struct filename *from, int newdfd,
4591 struct filename *to, unsigned int flags)
4592{
4593 struct renamedata rd;
4594 struct dentry *old_dentry, *new_dentry;
4595 struct dentry *trap;
4596 struct path old_path, new_path;
4597 struct qstr old_last, new_last;
4598 int old_type, new_type;
4599 struct inode *delegated_inode = NULL;
4600 unsigned int lookup_flags = 0, target_flags = LOOKUP_RENAME_TARGET;
4601 bool should_retry = false;
4602 int error = -EINVAL;
4603
4604 if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
4605 goto put_both;
4606
4607 if ((flags & (RENAME_NOREPLACE | RENAME_WHITEOUT)) &&
4608 (flags & RENAME_EXCHANGE))
4609 goto put_both;
4610
4611 if (flags & RENAME_EXCHANGE)
4612 target_flags = 0;
4613
4614retry:
4615 from = filename_parentat(olddfd, from, lookup_flags, &old_path,
4616 &old_last, &old_type);
4617 if (IS_ERR(from)) {
4618 error = PTR_ERR(from);
4619 goto put_new;
4620 }
4621
4622 to = filename_parentat(newdfd, to, lookup_flags, &new_path, &new_last,
4623 &new_type);
4624 if (IS_ERR(to)) {
4625 error = PTR_ERR(to);
4626 goto exit1;
4627 }
4628
4629 error = -EXDEV;
4630 if (old_path.mnt != new_path.mnt)
4631 goto exit2;
4632
4633 error = -EBUSY;
4634 if (old_type != LAST_NORM)
4635 goto exit2;
4636
4637 if (flags & RENAME_NOREPLACE)
4638 error = -EEXIST;
4639 if (new_type != LAST_NORM)
4640 goto exit2;
4641
4642 error = mnt_want_write(old_path.mnt);
4643 if (error)
4644 goto exit2;
4645
4646retry_deleg:
4647 trap = lock_rename(new_path.dentry, old_path.dentry);
4648
4649 old_dentry = __lookup_hash(&old_last, old_path.dentry, lookup_flags);
4650 error = PTR_ERR(old_dentry);
4651 if (IS_ERR(old_dentry))
4652 goto exit3;
4653 /* source must exist */
4654 error = -ENOENT;
4655 if (d_is_negative(old_dentry))
4656 goto exit4;
4657 new_dentry = __lookup_hash(&new_last, new_path.dentry, lookup_flags | target_flags);
4658 error = PTR_ERR(new_dentry);
4659 if (IS_ERR(new_dentry))
4660 goto exit4;
4661 error = -EEXIST;
4662 if ((flags & RENAME_NOREPLACE) && d_is_positive(new_dentry))
4663 goto exit5;
4664 if (flags & RENAME_EXCHANGE) {
4665 error = -ENOENT;
4666 if (d_is_negative(new_dentry))
4667 goto exit5;
4668
4669 if (!d_is_dir(new_dentry)) {
4670 error = -ENOTDIR;
4671 if (new_last.name[new_last.len])
4672 goto exit5;
4673 }
4674 }
4675 /* unless the source is a directory trailing slashes give -ENOTDIR */
4676 if (!d_is_dir(old_dentry)) {
4677 error = -ENOTDIR;
4678 if (old_last.name[old_last.len])
4679 goto exit5;
4680 if (!(flags & RENAME_EXCHANGE) && new_last.name[new_last.len])
4681 goto exit5;
4682 }
4683 /* source should not be ancestor of target */
4684 error = -EINVAL;
4685 if (old_dentry == trap)
4686 goto exit5;
4687 /* target should not be an ancestor of source */
4688 if (!(flags & RENAME_EXCHANGE))
4689 error = -ENOTEMPTY;
4690 if (new_dentry == trap)
4691 goto exit5;
4692
4693 error = security_path_rename(&old_path, old_dentry,
4694 &new_path, new_dentry, flags);
4695 if (error)
4696 goto exit5;
4697
4698 rd.old_dir = old_path.dentry->d_inode;
4699 rd.old_dentry = old_dentry;
4700 rd.old_mnt_userns = mnt_user_ns(old_path.mnt);
4701 rd.new_dir = new_path.dentry->d_inode;
4702 rd.new_dentry = new_dentry;
4703 rd.new_mnt_userns = mnt_user_ns(new_path.mnt);
4704 rd.delegated_inode = &delegated_inode;
4705 rd.flags = flags;
4706 error = vfs_rename(&rd);
4707exit5:
4708 dput(new_dentry);
4709exit4:
4710 dput(old_dentry);
4711exit3:
4712 unlock_rename(new_path.dentry, old_path.dentry);
4713 if (delegated_inode) {
4714 error = break_deleg_wait(&delegated_inode);
4715 if (!error)
4716 goto retry_deleg;
4717 }
4718 mnt_drop_write(old_path.mnt);
4719exit2:
4720 if (retry_estale(error, lookup_flags))
4721 should_retry = true;
4722 path_put(&new_path);
4723exit1:
4724 path_put(&old_path);
4725 if (should_retry) {
4726 should_retry = false;
4727 lookup_flags |= LOOKUP_REVAL;
4728 goto retry;
4729 }
4730put_both:
4731 if (!IS_ERR(from))
4732 putname(from);
4733put_new:
4734 if (!IS_ERR(to))
4735 putname(to);
4736 return error;
4737}
4738
4739SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname,
4740 int, newdfd, const char __user *, newname, unsigned int, flags)
4741{
4742 return do_renameat2(olddfd, getname(oldname), newdfd, getname(newname),
4743 flags);
4744}
4745
4746SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
4747 int, newdfd, const char __user *, newname)
4748{
4749 return do_renameat2(olddfd, getname(oldname), newdfd, getname(newname),
4750 0);
4751}
4752
4753SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
4754{
4755 return do_renameat2(AT_FDCWD, getname(oldname), AT_FDCWD,
4756 getname(newname), 0);
4757}
4758
4759int readlink_copy(char __user *buffer, int buflen, const char *link)
4760{
4761 int len = PTR_ERR(link);
4762 if (IS_ERR(link))
4763 goto out;
4764
4765 len = strlen(link);
4766 if (len > (unsigned) buflen)
4767 len = buflen;
4768 if (copy_to_user(buffer, link, len))
4769 len = -EFAULT;
4770out:
4771 return len;
4772}
4773
4774/**
4775 * vfs_readlink - copy symlink body into userspace buffer
4776 * @dentry: dentry on which to get symbolic link
4777 * @buffer: user memory pointer
4778 * @buflen: size of buffer
4779 *
4780 * Does not touch atime. That's up to the caller if necessary
4781 *
4782 * Does not call security hook.
4783 */
4784int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen)
4785{
4786 struct inode *inode = d_inode(dentry);
4787 DEFINE_DELAYED_CALL(done);
4788 const char *link;
4789 int res;
4790
4791 if (unlikely(!(inode->i_opflags & IOP_DEFAULT_READLINK))) {
4792 if (unlikely(inode->i_op->readlink))
4793 return inode->i_op->readlink(dentry, buffer, buflen);
4794
4795 if (!d_is_symlink(dentry))
4796 return -EINVAL;
4797
4798 spin_lock(&inode->i_lock);
4799 inode->i_opflags |= IOP_DEFAULT_READLINK;
4800 spin_unlock(&inode->i_lock);
4801 }
4802
4803 link = READ_ONCE(inode->i_link);
4804 if (!link) {
4805 link = inode->i_op->get_link(dentry, inode, &done);
4806 if (IS_ERR(link))
4807 return PTR_ERR(link);
4808 }
4809 res = readlink_copy(buffer, buflen, link);
4810 do_delayed_call(&done);
4811 return res;
4812}
4813EXPORT_SYMBOL(vfs_readlink);
4814
4815/**
4816 * vfs_get_link - get symlink body
4817 * @dentry: dentry on which to get symbolic link
4818 * @done: caller needs to free returned data with this
4819 *
4820 * Calls security hook and i_op->get_link() on the supplied inode.
4821 *
4822 * It does not touch atime. That's up to the caller if necessary.
4823 *
4824 * Does not work on "special" symlinks like /proc/$$/fd/N
4825 */
4826const char *vfs_get_link(struct dentry *dentry, struct delayed_call *done)
4827{
4828 const char *res = ERR_PTR(-EINVAL);
4829 struct inode *inode = d_inode(dentry);
4830
4831 if (d_is_symlink(dentry)) {
4832 res = ERR_PTR(security_inode_readlink(dentry));
4833 if (!res)
4834 res = inode->i_op->get_link(dentry, inode, done);
4835 }
4836 return res;
4837}
4838EXPORT_SYMBOL(vfs_get_link);
4839
4840/* get the link contents into pagecache */
4841const char *page_get_link(struct dentry *dentry, struct inode *inode,
4842 struct delayed_call *callback)
4843{
4844 char *kaddr;
4845 struct page *page;
4846 struct address_space *mapping = inode->i_mapping;
4847
4848 if (!dentry) {
4849 page = find_get_page(mapping, 0);
4850 if (!page)
4851 return ERR_PTR(-ECHILD);
4852 if (!PageUptodate(page)) {
4853 put_page(page);
4854 return ERR_PTR(-ECHILD);
4855 }
4856 } else {
4857 page = read_mapping_page(mapping, 0, NULL);
4858 if (IS_ERR(page))
4859 return (char*)page;
4860 }
4861 set_delayed_call(callback, page_put_link, page);
4862 BUG_ON(mapping_gfp_mask(mapping) & __GFP_HIGHMEM);
4863 kaddr = page_address(page);
4864 nd_terminate_link(kaddr, inode->i_size, PAGE_SIZE - 1);
4865 return kaddr;
4866}
4867
4868EXPORT_SYMBOL(page_get_link);
4869
4870void page_put_link(void *arg)
4871{
4872 put_page(arg);
4873}
4874EXPORT_SYMBOL(page_put_link);
4875
4876int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
4877{
4878 DEFINE_DELAYED_CALL(done);
4879 int res = readlink_copy(buffer, buflen,
4880 page_get_link(dentry, d_inode(dentry),
4881 &done));
4882 do_delayed_call(&done);
4883 return res;
4884}
4885EXPORT_SYMBOL(page_readlink);
4886
4887/*
4888 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
4889 */
4890int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
4891{
4892 struct address_space *mapping = inode->i_mapping;
4893 struct page *page;
4894 void *fsdata;
4895 int err;
4896 unsigned int flags = 0;
4897 if (nofs)
4898 flags |= AOP_FLAG_NOFS;
4899
4900retry:
4901 err = pagecache_write_begin(NULL, mapping, 0, len-1,
4902 flags, &page, &fsdata);
4903 if (err)
4904 goto fail;
4905
4906 memcpy(page_address(page), symname, len-1);
4907
4908 err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
4909 page, fsdata);
4910 if (err < 0)
4911 goto fail;
4912 if (err < len-1)
4913 goto retry;
4914
4915 mark_inode_dirty(inode);
4916 return 0;
4917fail:
4918 return err;
4919}
4920EXPORT_SYMBOL(__page_symlink);
4921
4922int page_symlink(struct inode *inode, const char *symname, int len)
4923{
4924 return __page_symlink(inode, symname, len,
4925 !mapping_gfp_constraint(inode->i_mapping, __GFP_FS));
4926}
4927EXPORT_SYMBOL(page_symlink);
4928
4929const struct inode_operations page_symlink_inode_operations = {
4930 .get_link = page_get_link,
4931};
4932EXPORT_SYMBOL(page_symlink_inode_operations);