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