4 * Copyright (C) 1991, 1992 Linus Torvalds
8 * Some corrections by tytso.
11 /* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
14 /* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.
17 #include <linux/init.h>
18 #include <linux/export.h>
19 #include <linux/kernel.h>
20 #include <linux/slab.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 <asm/uaccess.h>
42 /* [Feb-1997 T. Schoebel-Theuer]
43 * Fundamental changes in the pathname lookup mechanisms (namei)
44 * were necessary because of omirr. The reason is that omirr needs
45 * to know the _real_ pathname, not the user-supplied one, in case
46 * of symlinks (and also when transname replacements occur).
48 * The new code replaces the old recursive symlink resolution with
49 * an iterative one (in case of non-nested symlink chains). It does
50 * this with calls to <fs>_follow_link().
51 * As a side effect, dir_namei(), _namei() and follow_link() are now
52 * replaced with a single function lookup_dentry() that can handle all
53 * the special cases of the former code.
55 * With the new dcache, the pathname is stored at each inode, at least as
56 * long as the refcount of the inode is positive. As a side effect, the
57 * size of the dcache depends on the inode cache and thus is dynamic.
59 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
60 * resolution to correspond with current state of the code.
62 * Note that the symlink resolution is not *completely* iterative.
63 * There is still a significant amount of tail- and mid- recursion in
64 * the algorithm. Also, note that <fs>_readlink() is not used in
65 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
66 * may return different results than <fs>_follow_link(). Many virtual
67 * filesystems (including /proc) exhibit this behavior.
70 /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
71 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
72 * and the name already exists in form of a symlink, try to create the new
73 * name indicated by the symlink. The old code always complained that the
74 * name already exists, due to not following the symlink even if its target
75 * is nonexistent. The new semantics affects also mknod() and link() when
76 * the name is a symlink pointing to a non-existent name.
78 * I don't know which semantics is the right one, since I have no access
79 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
80 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
81 * "old" one. Personally, I think the new semantics is much more logical.
82 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
83 * file does succeed in both HP-UX and SunOs, but not in Solaris
84 * and in the old Linux semantics.
87 /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
88 * semantics. See the comments in "open_namei" and "do_link" below.
90 * [10-Sep-98 Alan Modra] Another symlink change.
93 /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
94 * inside the path - always follow.
95 * in the last component in creation/removal/renaming - never follow.
96 * if LOOKUP_FOLLOW passed - follow.
97 * if the pathname has trailing slashes - follow.
98 * otherwise - don't follow.
99 * (applied in that order).
101 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
102 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
103 * During the 2.4 we need to fix the userland stuff depending on it -
104 * hopefully we will be able to get rid of that wart in 2.5. So far only
105 * XEmacs seems to be relying on it...
108 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
109 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
110 * any extra contention...
113 /* In order to reduce some races, while at the same time doing additional
114 * checking and hopefully speeding things up, we copy filenames to the
115 * kernel data space before using them..
117 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
118 * PATH_MAX includes the nul terminator --RR.
120 void final_putname(struct filename
*name
)
122 if (name
->separate
) {
123 __putname(name
->name
);
130 #define EMBEDDED_NAME_MAX (PATH_MAX - sizeof(struct filename))
132 static struct filename
*
133 getname_flags(const char __user
*filename
, int flags
, int *empty
)
135 struct filename
*result
, *err
;
140 result
= audit_reusename(filename
);
144 result
= __getname();
145 if (unlikely(!result
))
146 return ERR_PTR(-ENOMEM
);
149 * First, try to embed the struct filename inside the names_cache
152 kname
= (char *)result
+ sizeof(*result
);
153 result
->name
= kname
;
154 result
->separate
= false;
155 max
= EMBEDDED_NAME_MAX
;
158 len
= strncpy_from_user(kname
, filename
, max
);
159 if (unlikely(len
< 0)) {
165 * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a
166 * separate struct filename so we can dedicate the entire
167 * names_cache allocation for the pathname, and re-do the copy from
170 if (len
== EMBEDDED_NAME_MAX
&& max
== EMBEDDED_NAME_MAX
) {
171 kname
= (char *)result
;
173 result
= kzalloc(sizeof(*result
), GFP_KERNEL
);
175 err
= ERR_PTR(-ENOMEM
);
176 result
= (struct filename
*)kname
;
179 result
->name
= kname
;
180 result
->separate
= true;
185 /* The empty path is special. */
186 if (unlikely(!len
)) {
189 err
= ERR_PTR(-ENOENT
);
190 if (!(flags
& LOOKUP_EMPTY
))
194 err
= ERR_PTR(-ENAMETOOLONG
);
195 if (unlikely(len
>= PATH_MAX
))
198 result
->uptr
= filename
;
199 audit_getname(result
);
203 final_putname(result
);
208 getname(const char __user
* filename
)
210 return getname_flags(filename
, 0, NULL
);
212 EXPORT_SYMBOL(getname
);
214 #ifdef CONFIG_AUDITSYSCALL
215 void putname(struct filename
*name
)
217 if (unlikely(!audit_dummy_context()))
218 return audit_putname(name
);
223 static int check_acl(struct inode
*inode
, int mask
)
225 #ifdef CONFIG_FS_POSIX_ACL
226 struct posix_acl
*acl
;
228 if (mask
& MAY_NOT_BLOCK
) {
229 acl
= get_cached_acl_rcu(inode
, ACL_TYPE_ACCESS
);
232 /* no ->get_acl() calls in RCU mode... */
233 if (acl
== ACL_NOT_CACHED
)
235 return posix_acl_permission(inode
, acl
, mask
& ~MAY_NOT_BLOCK
);
238 acl
= get_cached_acl(inode
, ACL_TYPE_ACCESS
);
241 * A filesystem can force a ACL callback by just never filling the
242 * ACL cache. But normally you'd fill the cache either at inode
243 * instantiation time, or on the first ->get_acl call.
245 * If the filesystem doesn't have a get_acl() function at all, we'll
246 * just create the negative cache entry.
248 if (acl
== ACL_NOT_CACHED
) {
249 if (inode
->i_op
->get_acl
) {
250 acl
= inode
->i_op
->get_acl(inode
, ACL_TYPE_ACCESS
);
254 set_cached_acl(inode
, ACL_TYPE_ACCESS
, NULL
);
260 int error
= posix_acl_permission(inode
, acl
, mask
);
261 posix_acl_release(acl
);
270 * This does the basic permission checking
272 static int acl_permission_check(struct inode
*inode
, int mask
)
274 unsigned int mode
= inode
->i_mode
;
276 if (likely(uid_eq(current_fsuid(), inode
->i_uid
)))
279 if (IS_POSIXACL(inode
) && (mode
& S_IRWXG
)) {
280 int error
= check_acl(inode
, mask
);
281 if (error
!= -EAGAIN
)
285 if (in_group_p(inode
->i_gid
))
290 * If the DACs are ok we don't need any capability check.
292 if ((mask
& ~mode
& (MAY_READ
| MAY_WRITE
| MAY_EXEC
)) == 0)
298 * generic_permission - check for access rights on a Posix-like filesystem
299 * @inode: inode to check access rights for
300 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
302 * Used to check for read/write/execute permissions on a file.
303 * We use "fsuid" for this, letting us set arbitrary permissions
304 * for filesystem access without changing the "normal" uids which
305 * are used for other things.
307 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
308 * request cannot be satisfied (eg. requires blocking or too much complexity).
309 * It would then be called again in ref-walk mode.
311 int generic_permission(struct inode
*inode
, int mask
)
316 * Do the basic permission checks.
318 ret
= acl_permission_check(inode
, mask
);
322 if (S_ISDIR(inode
->i_mode
)) {
323 /* DACs are overridable for directories */
324 if (inode_capable(inode
, CAP_DAC_OVERRIDE
))
326 if (!(mask
& MAY_WRITE
))
327 if (inode_capable(inode
, CAP_DAC_READ_SEARCH
))
332 * Read/write DACs are always overridable.
333 * Executable DACs are overridable when there is
334 * at least one exec bit set.
336 if (!(mask
& MAY_EXEC
) || (inode
->i_mode
& S_IXUGO
))
337 if (inode_capable(inode
, CAP_DAC_OVERRIDE
))
341 * Searching includes executable on directories, else just read.
343 mask
&= MAY_READ
| MAY_WRITE
| MAY_EXEC
;
344 if (mask
== MAY_READ
)
345 if (inode_capable(inode
, CAP_DAC_READ_SEARCH
))
352 * We _really_ want to just do "generic_permission()" without
353 * even looking at the inode->i_op values. So we keep a cache
354 * flag in inode->i_opflags, that says "this has not special
355 * permission function, use the fast case".
357 static inline int do_inode_permission(struct inode
*inode
, int mask
)
359 if (unlikely(!(inode
->i_opflags
& IOP_FASTPERM
))) {
360 if (likely(inode
->i_op
->permission
))
361 return inode
->i_op
->permission(inode
, mask
);
363 /* This gets set once for the inode lifetime */
364 spin_lock(&inode
->i_lock
);
365 inode
->i_opflags
|= IOP_FASTPERM
;
366 spin_unlock(&inode
->i_lock
);
368 return generic_permission(inode
, mask
);
372 * __inode_permission - Check for access rights to a given inode
373 * @inode: Inode to check permission on
374 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
376 * Check for read/write/execute permissions on an inode.
378 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
380 * This does not check for a read-only file system. You probably want
381 * inode_permission().
383 int __inode_permission(struct inode
*inode
, int mask
)
387 if (unlikely(mask
& MAY_WRITE
)) {
389 * Nobody gets write access to an immutable file.
391 if (IS_IMMUTABLE(inode
))
395 retval
= do_inode_permission(inode
, mask
);
399 retval
= devcgroup_inode_permission(inode
, mask
);
403 return security_inode_permission(inode
, mask
);
407 * sb_permission - Check superblock-level permissions
408 * @sb: Superblock of inode to check permission on
409 * @inode: Inode to check permission on
410 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
412 * Separate out file-system wide checks from inode-specific permission checks.
414 static int sb_permission(struct super_block
*sb
, struct inode
*inode
, int mask
)
416 if (unlikely(mask
& MAY_WRITE
)) {
417 umode_t mode
= inode
->i_mode
;
419 /* Nobody gets write access to a read-only fs. */
420 if ((sb
->s_flags
& MS_RDONLY
) &&
421 (S_ISREG(mode
) || S_ISDIR(mode
) || S_ISLNK(mode
)))
428 * inode_permission - Check for access rights to a given inode
429 * @inode: Inode to check permission on
430 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
432 * Check for read/write/execute permissions on an inode. We use fs[ug]id for
433 * this, letting us set arbitrary permissions for filesystem access without
434 * changing the "normal" UIDs which are used for other things.
436 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
438 int inode_permission(struct inode
*inode
, int mask
)
442 retval
= sb_permission(inode
->i_sb
, inode
, mask
);
445 return __inode_permission(inode
, mask
);
449 * path_get - get a reference to a path
450 * @path: path to get the reference to
452 * Given a path increment the reference count to the dentry and the vfsmount.
454 void path_get(const struct path
*path
)
459 EXPORT_SYMBOL(path_get
);
462 * path_put - put a reference to a path
463 * @path: path to put the reference to
465 * Given a path decrement the reference count to the dentry and the vfsmount.
467 void path_put(const struct path
*path
)
472 EXPORT_SYMBOL(path_put
);
475 * Path walking has 2 modes, rcu-walk and ref-walk (see
476 * Documentation/filesystems/path-lookup.txt). In situations when we can't
477 * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
478 * normal reference counts on dentries and vfsmounts to transition to rcu-walk
479 * mode. Refcounts are grabbed at the last known good point before rcu-walk
480 * got stuck, so ref-walk may continue from there. If this is not successful
481 * (eg. a seqcount has changed), then failure is returned and it's up to caller
482 * to restart the path walk from the beginning in ref-walk mode.
486 * unlazy_walk - try to switch to ref-walk mode.
487 * @nd: nameidata pathwalk data
488 * @dentry: child of nd->path.dentry or NULL
489 * Returns: 0 on success, -ECHILD on failure
491 * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry
492 * for ref-walk mode. @dentry must be a path found by a do_lookup call on
493 * @nd or NULL. Must be called from rcu-walk context.
495 static int unlazy_walk(struct nameidata
*nd
, struct dentry
*dentry
)
497 struct fs_struct
*fs
= current
->fs
;
498 struct dentry
*parent
= nd
->path
.dentry
;
500 BUG_ON(!(nd
->flags
& LOOKUP_RCU
));
503 * After legitimizing the bastards, terminate_walk()
504 * will do the right thing for non-RCU mode, and all our
505 * subsequent exit cases should rcu_read_unlock()
506 * before returning. Do vfsmount first; if dentry
507 * can't be legitimized, just set nd->path.dentry to NULL
508 * and rely on dput(NULL) being a no-op.
510 if (!legitimize_mnt(nd
->path
.mnt
, nd
->m_seq
))
512 nd
->flags
&= ~LOOKUP_RCU
;
514 if (!lockref_get_not_dead(&parent
->d_lockref
)) {
515 nd
->path
.dentry
= NULL
;
520 * For a negative lookup, the lookup sequence point is the parents
521 * sequence point, and it only needs to revalidate the parent dentry.
523 * For a positive lookup, we need to move both the parent and the
524 * dentry from the RCU domain to be properly refcounted. And the
525 * sequence number in the dentry validates *both* dentry counters,
526 * since we checked the sequence number of the parent after we got
527 * the child sequence number. So we know the parent must still
528 * be valid if the child sequence number is still valid.
531 if (read_seqcount_retry(&parent
->d_seq
, nd
->seq
))
533 BUG_ON(nd
->inode
!= parent
->d_inode
);
535 if (!lockref_get_not_dead(&dentry
->d_lockref
))
537 if (read_seqcount_retry(&dentry
->d_seq
, nd
->seq
))
542 * Sequence counts matched. Now make sure that the root is
543 * still valid and get it if required.
545 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
)) {
546 spin_lock(&fs
->lock
);
547 if (nd
->root
.mnt
!= fs
->root
.mnt
|| nd
->root
.dentry
!= fs
->root
.dentry
)
548 goto unlock_and_drop_dentry
;
550 spin_unlock(&fs
->lock
);
556 unlock_and_drop_dentry
:
557 spin_unlock(&fs
->lock
);
565 if (!(nd
->flags
& LOOKUP_ROOT
))
570 static inline int d_revalidate(struct dentry
*dentry
, unsigned int flags
)
572 return dentry
->d_op
->d_revalidate(dentry
, flags
);
576 * complete_walk - successful completion of path walk
577 * @nd: pointer nameidata
579 * If we had been in RCU mode, drop out of it and legitimize nd->path.
580 * Revalidate the final result, unless we'd already done that during
581 * the path walk or the filesystem doesn't ask for it. Return 0 on
582 * success, -error on failure. In case of failure caller does not
583 * need to drop nd->path.
585 static int complete_walk(struct nameidata
*nd
)
587 struct dentry
*dentry
= nd
->path
.dentry
;
590 if (nd
->flags
& LOOKUP_RCU
) {
591 nd
->flags
&= ~LOOKUP_RCU
;
592 if (!(nd
->flags
& LOOKUP_ROOT
))
595 if (!legitimize_mnt(nd
->path
.mnt
, nd
->m_seq
)) {
599 if (unlikely(!lockref_get_not_dead(&dentry
->d_lockref
))) {
601 mntput(nd
->path
.mnt
);
604 if (read_seqcount_retry(&dentry
->d_seq
, nd
->seq
)) {
607 mntput(nd
->path
.mnt
);
613 if (likely(!(nd
->flags
& LOOKUP_JUMPED
)))
616 if (likely(!(dentry
->d_flags
& DCACHE_OP_WEAK_REVALIDATE
)))
619 status
= dentry
->d_op
->d_weak_revalidate(dentry
, nd
->flags
);
630 static __always_inline
void set_root(struct nameidata
*nd
)
633 get_fs_root(current
->fs
, &nd
->root
);
636 static int link_path_walk(const char *, struct nameidata
*);
638 static __always_inline
void set_root_rcu(struct nameidata
*nd
)
641 struct fs_struct
*fs
= current
->fs
;
645 seq
= read_seqcount_begin(&fs
->seq
);
647 nd
->seq
= __read_seqcount_begin(&nd
->root
.dentry
->d_seq
);
648 } while (read_seqcount_retry(&fs
->seq
, seq
));
652 static void path_put_conditional(struct path
*path
, struct nameidata
*nd
)
655 if (path
->mnt
!= nd
->path
.mnt
)
659 static inline void path_to_nameidata(const struct path
*path
,
660 struct nameidata
*nd
)
662 if (!(nd
->flags
& LOOKUP_RCU
)) {
663 dput(nd
->path
.dentry
);
664 if (nd
->path
.mnt
!= path
->mnt
)
665 mntput(nd
->path
.mnt
);
667 nd
->path
.mnt
= path
->mnt
;
668 nd
->path
.dentry
= path
->dentry
;
672 * Helper to directly jump to a known parsed path from ->follow_link,
673 * caller must have taken a reference to path beforehand.
675 void nd_jump_link(struct nameidata
*nd
, struct path
*path
)
680 nd
->inode
= nd
->path
.dentry
->d_inode
;
681 nd
->flags
|= LOOKUP_JUMPED
;
684 static inline void put_link(struct nameidata
*nd
, struct path
*link
, void *cookie
)
686 struct inode
*inode
= link
->dentry
->d_inode
;
687 if (inode
->i_op
->put_link
)
688 inode
->i_op
->put_link(link
->dentry
, nd
, cookie
);
692 int sysctl_protected_symlinks __read_mostly
= 0;
693 int sysctl_protected_hardlinks __read_mostly
= 0;
696 * may_follow_link - Check symlink following for unsafe situations
697 * @link: The path of the symlink
698 * @nd: nameidata pathwalk data
700 * In the case of the sysctl_protected_symlinks sysctl being enabled,
701 * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
702 * in a sticky world-writable directory. This is to protect privileged
703 * processes from failing races against path names that may change out
704 * from under them by way of other users creating malicious symlinks.
705 * It will permit symlinks to be followed only when outside a sticky
706 * world-writable directory, or when the uid of the symlink and follower
707 * match, or when the directory owner matches the symlink's owner.
709 * Returns 0 if following the symlink is allowed, -ve on error.
711 static inline int may_follow_link(struct path
*link
, struct nameidata
*nd
)
713 const struct inode
*inode
;
714 const struct inode
*parent
;
716 if (!sysctl_protected_symlinks
)
719 /* Allowed if owner and follower match. */
720 inode
= link
->dentry
->d_inode
;
721 if (uid_eq(current_cred()->fsuid
, inode
->i_uid
))
724 /* Allowed if parent directory not sticky and world-writable. */
725 parent
= nd
->path
.dentry
->d_inode
;
726 if ((parent
->i_mode
& (S_ISVTX
|S_IWOTH
)) != (S_ISVTX
|S_IWOTH
))
729 /* Allowed if parent directory and link owner match. */
730 if (uid_eq(parent
->i_uid
, inode
->i_uid
))
733 audit_log_link_denied("follow_link", link
);
734 path_put_conditional(link
, nd
);
740 * safe_hardlink_source - Check for safe hardlink conditions
741 * @inode: the source inode to hardlink from
743 * Return false if at least one of the following conditions:
744 * - inode is not a regular file
746 * - inode is setgid and group-exec
747 * - access failure for read and write
749 * Otherwise returns true.
751 static bool safe_hardlink_source(struct inode
*inode
)
753 umode_t mode
= inode
->i_mode
;
755 /* Special files should not get pinned to the filesystem. */
759 /* Setuid files should not get pinned to the filesystem. */
763 /* Executable setgid files should not get pinned to the filesystem. */
764 if ((mode
& (S_ISGID
| S_IXGRP
)) == (S_ISGID
| S_IXGRP
))
767 /* Hardlinking to unreadable or unwritable sources is dangerous. */
768 if (inode_permission(inode
, MAY_READ
| MAY_WRITE
))
775 * may_linkat - Check permissions for creating a hardlink
776 * @link: the source to hardlink from
778 * Block hardlink when all of:
779 * - sysctl_protected_hardlinks enabled
780 * - fsuid does not match inode
781 * - hardlink source is unsafe (see safe_hardlink_source() above)
784 * Returns 0 if successful, -ve on error.
786 static int may_linkat(struct path
*link
)
788 const struct cred
*cred
;
791 if (!sysctl_protected_hardlinks
)
794 cred
= current_cred();
795 inode
= link
->dentry
->d_inode
;
797 /* Source inode owner (or CAP_FOWNER) can hardlink all they like,
798 * otherwise, it must be a safe source.
800 if (uid_eq(cred
->fsuid
, inode
->i_uid
) || safe_hardlink_source(inode
) ||
804 audit_log_link_denied("linkat", link
);
808 static __always_inline
int
809 follow_link(struct path
*link
, struct nameidata
*nd
, void **p
)
811 struct dentry
*dentry
= link
->dentry
;
815 BUG_ON(nd
->flags
& LOOKUP_RCU
);
817 if (link
->mnt
== nd
->path
.mnt
)
821 if (unlikely(current
->total_link_count
>= 40))
822 goto out_put_nd_path
;
825 current
->total_link_count
++;
828 nd_set_link(nd
, NULL
);
830 error
= security_inode_follow_link(link
->dentry
, nd
);
832 goto out_put_nd_path
;
834 nd
->last_type
= LAST_BIND
;
835 *p
= dentry
->d_inode
->i_op
->follow_link(dentry
, nd
);
838 goto out_put_nd_path
;
843 if (unlikely(IS_ERR(s
))) {
845 put_link(nd
, link
, *p
);
853 nd
->flags
|= LOOKUP_JUMPED
;
855 nd
->inode
= nd
->path
.dentry
->d_inode
;
856 error
= link_path_walk(s
, nd
);
858 put_link(nd
, link
, *p
);
870 static int follow_up_rcu(struct path
*path
)
872 struct mount
*mnt
= real_mount(path
->mnt
);
873 struct mount
*parent
;
874 struct dentry
*mountpoint
;
876 parent
= mnt
->mnt_parent
;
877 if (&parent
->mnt
== path
->mnt
)
879 mountpoint
= mnt
->mnt_mountpoint
;
880 path
->dentry
= mountpoint
;
881 path
->mnt
= &parent
->mnt
;
886 * follow_up - Find the mountpoint of path's vfsmount
888 * Given a path, find the mountpoint of its source file system.
889 * Replace @path with the path of the mountpoint in the parent mount.
892 * Return 1 if we went up a level and 0 if we were already at the
895 int follow_up(struct path
*path
)
897 struct mount
*mnt
= real_mount(path
->mnt
);
898 struct mount
*parent
;
899 struct dentry
*mountpoint
;
901 read_seqlock_excl(&mount_lock
);
902 parent
= mnt
->mnt_parent
;
904 read_sequnlock_excl(&mount_lock
);
907 mntget(&parent
->mnt
);
908 mountpoint
= dget(mnt
->mnt_mountpoint
);
909 read_sequnlock_excl(&mount_lock
);
911 path
->dentry
= mountpoint
;
913 path
->mnt
= &parent
->mnt
;
918 * Perform an automount
919 * - return -EISDIR to tell follow_managed() to stop and return the path we
922 static int follow_automount(struct path
*path
, unsigned flags
,
925 struct vfsmount
*mnt
;
928 if (!path
->dentry
->d_op
|| !path
->dentry
->d_op
->d_automount
)
931 /* We don't want to mount if someone's just doing a stat -
932 * unless they're stat'ing a directory and appended a '/' to
935 * We do, however, want to mount if someone wants to open or
936 * create a file of any type under the mountpoint, wants to
937 * traverse through the mountpoint or wants to open the
938 * mounted directory. Also, autofs may mark negative dentries
939 * as being automount points. These will need the attentions
940 * of the daemon to instantiate them before they can be used.
942 if (!(flags
& (LOOKUP_PARENT
| LOOKUP_DIRECTORY
|
943 LOOKUP_OPEN
| LOOKUP_CREATE
| LOOKUP_AUTOMOUNT
)) &&
944 path
->dentry
->d_inode
)
947 current
->total_link_count
++;
948 if (current
->total_link_count
>= 40)
951 mnt
= path
->dentry
->d_op
->d_automount(path
);
954 * The filesystem is allowed to return -EISDIR here to indicate
955 * it doesn't want to automount. For instance, autofs would do
956 * this so that its userspace daemon can mount on this dentry.
958 * However, we can only permit this if it's a terminal point in
959 * the path being looked up; if it wasn't then the remainder of
960 * the path is inaccessible and we should say so.
962 if (PTR_ERR(mnt
) == -EISDIR
&& (flags
& LOOKUP_PARENT
))
967 if (!mnt
) /* mount collision */
971 /* lock_mount() may release path->mnt on error */
975 err
= finish_automount(mnt
, path
);
979 /* Someone else made a mount here whilst we were busy */
984 path
->dentry
= dget(mnt
->mnt_root
);
993 * Handle a dentry that is managed in some way.
994 * - Flagged for transit management (autofs)
995 * - Flagged as mountpoint
996 * - Flagged as automount point
998 * This may only be called in refwalk mode.
1000 * Serialization is taken care of in namespace.c
1002 static int follow_managed(struct path
*path
, unsigned flags
)
1004 struct vfsmount
*mnt
= path
->mnt
; /* held by caller, must be left alone */
1006 bool need_mntput
= false;
1009 /* Given that we're not holding a lock here, we retain the value in a
1010 * local variable for each dentry as we look at it so that we don't see
1011 * the components of that value change under us */
1012 while (managed
= ACCESS_ONCE(path
->dentry
->d_flags
),
1013 managed
&= DCACHE_MANAGED_DENTRY
,
1014 unlikely(managed
!= 0)) {
1015 /* Allow the filesystem to manage the transit without i_mutex
1017 if (managed
& DCACHE_MANAGE_TRANSIT
) {
1018 BUG_ON(!path
->dentry
->d_op
);
1019 BUG_ON(!path
->dentry
->d_op
->d_manage
);
1020 ret
= path
->dentry
->d_op
->d_manage(path
->dentry
, false);
1025 /* Transit to a mounted filesystem. */
1026 if (managed
& DCACHE_MOUNTED
) {
1027 struct vfsmount
*mounted
= lookup_mnt(path
);
1032 path
->mnt
= mounted
;
1033 path
->dentry
= dget(mounted
->mnt_root
);
1038 /* Something is mounted on this dentry in another
1039 * namespace and/or whatever was mounted there in this
1040 * namespace got unmounted before lookup_mnt() could
1044 /* Handle an automount point */
1045 if (managed
& DCACHE_NEED_AUTOMOUNT
) {
1046 ret
= follow_automount(path
, flags
, &need_mntput
);
1052 /* We didn't change the current path point */
1056 if (need_mntput
&& path
->mnt
== mnt
)
1060 return ret
< 0 ? ret
: need_mntput
;
1063 int follow_down_one(struct path
*path
)
1065 struct vfsmount
*mounted
;
1067 mounted
= lookup_mnt(path
);
1071 path
->mnt
= mounted
;
1072 path
->dentry
= dget(mounted
->mnt_root
);
1078 static inline bool managed_dentry_might_block(struct dentry
*dentry
)
1080 return (dentry
->d_flags
& DCACHE_MANAGE_TRANSIT
&&
1081 dentry
->d_op
->d_manage(dentry
, true) < 0);
1085 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
1086 * we meet a managed dentry that would need blocking.
1088 static bool __follow_mount_rcu(struct nameidata
*nd
, struct path
*path
,
1089 struct inode
**inode
)
1092 struct mount
*mounted
;
1094 * Don't forget we might have a non-mountpoint managed dentry
1095 * that wants to block transit.
1097 if (unlikely(managed_dentry_might_block(path
->dentry
)))
1100 if (!d_mountpoint(path
->dentry
))
1103 mounted
= __lookup_mnt(path
->mnt
, path
->dentry
);
1106 path
->mnt
= &mounted
->mnt
;
1107 path
->dentry
= mounted
->mnt
.mnt_root
;
1108 nd
->flags
|= LOOKUP_JUMPED
;
1109 nd
->seq
= read_seqcount_begin(&path
->dentry
->d_seq
);
1111 * Update the inode too. We don't need to re-check the
1112 * dentry sequence number here after this d_inode read,
1113 * because a mount-point is always pinned.
1115 *inode
= path
->dentry
->d_inode
;
1120 static void follow_mount_rcu(struct nameidata
*nd
)
1122 while (d_mountpoint(nd
->path
.dentry
)) {
1123 struct mount
*mounted
;
1124 mounted
= __lookup_mnt(nd
->path
.mnt
, nd
->path
.dentry
);
1127 nd
->path
.mnt
= &mounted
->mnt
;
1128 nd
->path
.dentry
= mounted
->mnt
.mnt_root
;
1129 nd
->seq
= read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1133 static int follow_dotdot_rcu(struct nameidata
*nd
)
1138 if (nd
->path
.dentry
== nd
->root
.dentry
&&
1139 nd
->path
.mnt
== nd
->root
.mnt
) {
1142 if (nd
->path
.dentry
!= nd
->path
.mnt
->mnt_root
) {
1143 struct dentry
*old
= nd
->path
.dentry
;
1144 struct dentry
*parent
= old
->d_parent
;
1147 seq
= read_seqcount_begin(&parent
->d_seq
);
1148 if (read_seqcount_retry(&old
->d_seq
, nd
->seq
))
1150 nd
->path
.dentry
= parent
;
1154 if (!follow_up_rcu(&nd
->path
))
1156 nd
->seq
= read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1158 follow_mount_rcu(nd
);
1159 nd
->inode
= nd
->path
.dentry
->d_inode
;
1163 nd
->flags
&= ~LOOKUP_RCU
;
1164 if (!(nd
->flags
& LOOKUP_ROOT
))
1165 nd
->root
.mnt
= NULL
;
1171 * Follow down to the covering mount currently visible to userspace. At each
1172 * point, the filesystem owning that dentry may be queried as to whether the
1173 * caller is permitted to proceed or not.
1175 int follow_down(struct path
*path
)
1180 while (managed
= ACCESS_ONCE(path
->dentry
->d_flags
),
1181 unlikely(managed
& DCACHE_MANAGED_DENTRY
)) {
1182 /* Allow the filesystem to manage the transit without i_mutex
1185 * We indicate to the filesystem if someone is trying to mount
1186 * something here. This gives autofs the chance to deny anyone
1187 * other than its daemon the right to mount on its
1190 * The filesystem may sleep at this point.
1192 if (managed
& DCACHE_MANAGE_TRANSIT
) {
1193 BUG_ON(!path
->dentry
->d_op
);
1194 BUG_ON(!path
->dentry
->d_op
->d_manage
);
1195 ret
= path
->dentry
->d_op
->d_manage(
1196 path
->dentry
, false);
1198 return ret
== -EISDIR
? 0 : ret
;
1201 /* Transit to a mounted filesystem. */
1202 if (managed
& DCACHE_MOUNTED
) {
1203 struct vfsmount
*mounted
= lookup_mnt(path
);
1208 path
->mnt
= mounted
;
1209 path
->dentry
= dget(mounted
->mnt_root
);
1213 /* Don't handle automount points here */
1220 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1222 static void follow_mount(struct path
*path
)
1224 while (d_mountpoint(path
->dentry
)) {
1225 struct vfsmount
*mounted
= lookup_mnt(path
);
1230 path
->mnt
= mounted
;
1231 path
->dentry
= dget(mounted
->mnt_root
);
1235 static void follow_dotdot(struct nameidata
*nd
)
1240 struct dentry
*old
= nd
->path
.dentry
;
1242 if (nd
->path
.dentry
== nd
->root
.dentry
&&
1243 nd
->path
.mnt
== nd
->root
.mnt
) {
1246 if (nd
->path
.dentry
!= nd
->path
.mnt
->mnt_root
) {
1247 /* rare case of legitimate dget_parent()... */
1248 nd
->path
.dentry
= dget_parent(nd
->path
.dentry
);
1252 if (!follow_up(&nd
->path
))
1255 follow_mount(&nd
->path
);
1256 nd
->inode
= nd
->path
.dentry
->d_inode
;
1260 * This looks up the name in dcache, possibly revalidates the old dentry and
1261 * allocates a new one if not found or not valid. In the need_lookup argument
1262 * returns whether i_op->lookup is necessary.
1264 * dir->d_inode->i_mutex must be held
1266 static struct dentry
*lookup_dcache(struct qstr
*name
, struct dentry
*dir
,
1267 unsigned int flags
, bool *need_lookup
)
1269 struct dentry
*dentry
;
1272 *need_lookup
= false;
1273 dentry
= d_lookup(dir
, name
);
1275 if (dentry
->d_flags
& DCACHE_OP_REVALIDATE
) {
1276 error
= d_revalidate(dentry
, flags
);
1277 if (unlikely(error
<= 0)) {
1280 return ERR_PTR(error
);
1281 } else if (!d_invalidate(dentry
)) {
1290 dentry
= d_alloc(dir
, name
);
1291 if (unlikely(!dentry
))
1292 return ERR_PTR(-ENOMEM
);
1294 *need_lookup
= true;
1300 * Call i_op->lookup on the dentry. The dentry must be negative and
1303 * dir->d_inode->i_mutex must be held
1305 static struct dentry
*lookup_real(struct inode
*dir
, struct dentry
*dentry
,
1310 /* Don't create child dentry for a dead directory. */
1311 if (unlikely(IS_DEADDIR(dir
))) {
1313 return ERR_PTR(-ENOENT
);
1316 old
= dir
->i_op
->lookup(dir
, dentry
, flags
);
1317 if (unlikely(old
)) {
1324 static struct dentry
*__lookup_hash(struct qstr
*name
,
1325 struct dentry
*base
, unsigned int flags
)
1328 struct dentry
*dentry
;
1330 dentry
= lookup_dcache(name
, base
, flags
, &need_lookup
);
1334 return lookup_real(base
->d_inode
, dentry
, flags
);
1338 * It's more convoluted than I'd like it to be, but... it's still fairly
1339 * small and for now I'd prefer to have fast path as straight as possible.
1340 * It _is_ time-critical.
1342 static int lookup_fast(struct nameidata
*nd
,
1343 struct path
*path
, struct inode
**inode
)
1345 struct vfsmount
*mnt
= nd
->path
.mnt
;
1346 struct dentry
*dentry
, *parent
= nd
->path
.dentry
;
1352 * Rename seqlock is not required here because in the off chance
1353 * of a false negative due to a concurrent rename, we're going to
1354 * do the non-racy lookup, below.
1356 if (nd
->flags
& LOOKUP_RCU
) {
1358 dentry
= __d_lookup_rcu(parent
, &nd
->last
, &seq
);
1363 * This sequence count validates that the inode matches
1364 * the dentry name information from lookup.
1366 *inode
= dentry
->d_inode
;
1367 if (read_seqcount_retry(&dentry
->d_seq
, seq
))
1371 * This sequence count validates that the parent had no
1372 * changes while we did the lookup of the dentry above.
1374 * The memory barrier in read_seqcount_begin of child is
1375 * enough, we can use __read_seqcount_retry here.
1377 if (__read_seqcount_retry(&parent
->d_seq
, nd
->seq
))
1381 if (unlikely(dentry
->d_flags
& DCACHE_OP_REVALIDATE
)) {
1382 status
= d_revalidate(dentry
, nd
->flags
);
1383 if (unlikely(status
<= 0)) {
1384 if (status
!= -ECHILD
)
1390 path
->dentry
= dentry
;
1391 if (unlikely(!__follow_mount_rcu(nd
, path
, inode
)))
1393 if (unlikely(path
->dentry
->d_flags
& DCACHE_NEED_AUTOMOUNT
))
1397 if (unlazy_walk(nd
, dentry
))
1400 dentry
= __d_lookup(parent
, &nd
->last
);
1403 if (unlikely(!dentry
))
1406 if (unlikely(dentry
->d_flags
& DCACHE_OP_REVALIDATE
) && need_reval
)
1407 status
= d_revalidate(dentry
, nd
->flags
);
1408 if (unlikely(status
<= 0)) {
1413 if (!d_invalidate(dentry
)) {
1420 path
->dentry
= dentry
;
1421 err
= follow_managed(path
, nd
->flags
);
1422 if (unlikely(err
< 0)) {
1423 path_put_conditional(path
, nd
);
1427 nd
->flags
|= LOOKUP_JUMPED
;
1428 *inode
= path
->dentry
->d_inode
;
1435 /* Fast lookup failed, do it the slow way */
1436 static int lookup_slow(struct nameidata
*nd
, struct path
*path
)
1438 struct dentry
*dentry
, *parent
;
1441 parent
= nd
->path
.dentry
;
1442 BUG_ON(nd
->inode
!= parent
->d_inode
);
1444 mutex_lock(&parent
->d_inode
->i_mutex
);
1445 dentry
= __lookup_hash(&nd
->last
, parent
, nd
->flags
);
1446 mutex_unlock(&parent
->d_inode
->i_mutex
);
1448 return PTR_ERR(dentry
);
1449 path
->mnt
= nd
->path
.mnt
;
1450 path
->dentry
= dentry
;
1451 err
= follow_managed(path
, nd
->flags
);
1452 if (unlikely(err
< 0)) {
1453 path_put_conditional(path
, nd
);
1457 nd
->flags
|= LOOKUP_JUMPED
;
1461 static inline int may_lookup(struct nameidata
*nd
)
1463 if (nd
->flags
& LOOKUP_RCU
) {
1464 int err
= inode_permission(nd
->inode
, MAY_EXEC
|MAY_NOT_BLOCK
);
1467 if (unlazy_walk(nd
, NULL
))
1470 return inode_permission(nd
->inode
, MAY_EXEC
);
1473 static inline int handle_dots(struct nameidata
*nd
, int type
)
1475 if (type
== LAST_DOTDOT
) {
1476 if (nd
->flags
& LOOKUP_RCU
) {
1477 if (follow_dotdot_rcu(nd
))
1485 static void terminate_walk(struct nameidata
*nd
)
1487 if (!(nd
->flags
& LOOKUP_RCU
)) {
1488 path_put(&nd
->path
);
1490 nd
->flags
&= ~LOOKUP_RCU
;
1491 if (!(nd
->flags
& LOOKUP_ROOT
))
1492 nd
->root
.mnt
= NULL
;
1498 * Do we need to follow links? We _really_ want to be able
1499 * to do this check without having to look at inode->i_op,
1500 * so we keep a cache of "no, this doesn't need follow_link"
1501 * for the common case.
1503 static inline int should_follow_link(struct dentry
*dentry
, int follow
)
1505 return unlikely(d_is_symlink(dentry
)) ? follow
: 0;
1508 static inline int walk_component(struct nameidata
*nd
, struct path
*path
,
1511 struct inode
*inode
;
1514 * "." and ".." are special - ".." especially so because it has
1515 * to be able to know about the current root directory and
1516 * parent relationships.
1518 if (unlikely(nd
->last_type
!= LAST_NORM
))
1519 return handle_dots(nd
, nd
->last_type
);
1520 err
= lookup_fast(nd
, path
, &inode
);
1521 if (unlikely(err
)) {
1525 err
= lookup_slow(nd
, path
);
1529 inode
= path
->dentry
->d_inode
;
1535 if (should_follow_link(path
->dentry
, follow
)) {
1536 if (nd
->flags
& LOOKUP_RCU
) {
1537 if (unlikely(unlazy_walk(nd
, path
->dentry
))) {
1542 BUG_ON(inode
!= path
->dentry
->d_inode
);
1545 path_to_nameidata(path
, nd
);
1550 path_to_nameidata(path
, nd
);
1557 * This limits recursive symlink follows to 8, while
1558 * limiting consecutive symlinks to 40.
1560 * Without that kind of total limit, nasty chains of consecutive
1561 * symlinks can cause almost arbitrarily long lookups.
1563 static inline int nested_symlink(struct path
*path
, struct nameidata
*nd
)
1567 if (unlikely(current
->link_count
>= MAX_NESTED_LINKS
)) {
1568 path_put_conditional(path
, nd
);
1569 path_put(&nd
->path
);
1572 BUG_ON(nd
->depth
>= MAX_NESTED_LINKS
);
1575 current
->link_count
++;
1578 struct path link
= *path
;
1581 res
= follow_link(&link
, nd
, &cookie
);
1584 res
= walk_component(nd
, path
, LOOKUP_FOLLOW
);
1585 put_link(nd
, &link
, cookie
);
1588 current
->link_count
--;
1594 * We can do the critical dentry name comparison and hashing
1595 * operations one word at a time, but we are limited to:
1597 * - Architectures with fast unaligned word accesses. We could
1598 * do a "get_unaligned()" if this helps and is sufficiently
1601 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
1602 * do not trap on the (extremely unlikely) case of a page
1603 * crossing operation.
1605 * - Furthermore, we need an efficient 64-bit compile for the
1606 * 64-bit case in order to generate the "number of bytes in
1607 * the final mask". Again, that could be replaced with a
1608 * efficient population count instruction or similar.
1610 #ifdef CONFIG_DCACHE_WORD_ACCESS
1612 #include <asm/word-at-a-time.h>
1616 static inline unsigned int fold_hash(unsigned long hash
)
1618 hash
+= hash
>> (8*sizeof(int));
1622 #else /* 32-bit case */
1624 #define fold_hash(x) (x)
1628 unsigned int full_name_hash(const unsigned char *name
, unsigned int len
)
1630 unsigned long a
, mask
;
1631 unsigned long hash
= 0;
1634 a
= load_unaligned_zeropad(name
);
1635 if (len
< sizeof(unsigned long))
1639 name
+= sizeof(unsigned long);
1640 len
-= sizeof(unsigned long);
1644 mask
= bytemask_from_count(len
);
1647 return fold_hash(hash
);
1649 EXPORT_SYMBOL(full_name_hash
);
1652 * Calculate the length and hash of the path component, and
1653 * return the length of the component;
1655 static inline unsigned long hash_name(const char *name
, unsigned int *hashp
)
1657 unsigned long a
, b
, adata
, bdata
, mask
, hash
, len
;
1658 const struct word_at_a_time constants
= WORD_AT_A_TIME_CONSTANTS
;
1661 len
= -sizeof(unsigned long);
1663 hash
= (hash
+ a
) * 9;
1664 len
+= sizeof(unsigned long);
1665 a
= load_unaligned_zeropad(name
+len
);
1666 b
= a
^ REPEAT_BYTE('/');
1667 } while (!(has_zero(a
, &adata
, &constants
) | has_zero(b
, &bdata
, &constants
)));
1669 adata
= prep_zero_mask(a
, adata
, &constants
);
1670 bdata
= prep_zero_mask(b
, bdata
, &constants
);
1672 mask
= create_zero_mask(adata
| bdata
);
1674 hash
+= a
& zero_bytemask(mask
);
1675 *hashp
= fold_hash(hash
);
1677 return len
+ find_zero(mask
);
1682 unsigned int full_name_hash(const unsigned char *name
, unsigned int len
)
1684 unsigned long hash
= init_name_hash();
1686 hash
= partial_name_hash(*name
++, hash
);
1687 return end_name_hash(hash
);
1689 EXPORT_SYMBOL(full_name_hash
);
1692 * We know there's a real path component here of at least
1695 static inline unsigned long hash_name(const char *name
, unsigned int *hashp
)
1697 unsigned long hash
= init_name_hash();
1698 unsigned long len
= 0, c
;
1700 c
= (unsigned char)*name
;
1703 hash
= partial_name_hash(c
, hash
);
1704 c
= (unsigned char)name
[len
];
1705 } while (c
&& c
!= '/');
1706 *hashp
= end_name_hash(hash
);
1714 * This is the basic name resolution function, turning a pathname into
1715 * the final dentry. We expect 'base' to be positive and a directory.
1717 * Returns 0 and nd will have valid dentry and mnt on success.
1718 * Returns error and drops reference to input namei data on failure.
1720 static int link_path_walk(const char *name
, struct nameidata
*nd
)
1730 /* At this point we know we have a real path component. */
1736 err
= may_lookup(nd
);
1740 len
= hash_name(name
, &this.hash
);
1745 if (name
[0] == '.') switch (len
) {
1747 if (name
[1] == '.') {
1749 nd
->flags
|= LOOKUP_JUMPED
;
1755 if (likely(type
== LAST_NORM
)) {
1756 struct dentry
*parent
= nd
->path
.dentry
;
1757 nd
->flags
&= ~LOOKUP_JUMPED
;
1758 if (unlikely(parent
->d_flags
& DCACHE_OP_HASH
)) {
1759 err
= parent
->d_op
->d_hash(parent
, &this);
1766 nd
->last_type
= type
;
1771 * If it wasn't NUL, we know it was '/'. Skip that
1772 * slash, and continue until no more slashes.
1776 } while (unlikely(name
[len
] == '/'));
1782 err
= walk_component(nd
, &next
, LOOKUP_FOLLOW
);
1787 err
= nested_symlink(&next
, nd
);
1791 if (!d_is_directory(nd
->path
.dentry
)) {
1800 static int path_init(int dfd
, const char *name
, unsigned int flags
,
1801 struct nameidata
*nd
, struct file
**fp
)
1805 nd
->last_type
= LAST_ROOT
; /* if there are only slashes... */
1806 nd
->flags
= flags
| LOOKUP_JUMPED
;
1808 if (flags
& LOOKUP_ROOT
) {
1809 struct dentry
*root
= nd
->root
.dentry
;
1810 struct inode
*inode
= root
->d_inode
;
1812 if (!d_is_directory(root
))
1814 retval
= inode_permission(inode
, MAY_EXEC
);
1818 nd
->path
= nd
->root
;
1820 if (flags
& LOOKUP_RCU
) {
1822 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1823 nd
->m_seq
= read_seqbegin(&mount_lock
);
1825 path_get(&nd
->path
);
1830 nd
->root
.mnt
= NULL
;
1832 nd
->m_seq
= read_seqbegin(&mount_lock
);
1834 if (flags
& LOOKUP_RCU
) {
1839 path_get(&nd
->root
);
1841 nd
->path
= nd
->root
;
1842 } else if (dfd
== AT_FDCWD
) {
1843 if (flags
& LOOKUP_RCU
) {
1844 struct fs_struct
*fs
= current
->fs
;
1850 seq
= read_seqcount_begin(&fs
->seq
);
1852 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1853 } while (read_seqcount_retry(&fs
->seq
, seq
));
1855 get_fs_pwd(current
->fs
, &nd
->path
);
1858 /* Caller must check execute permissions on the starting path component */
1859 struct fd f
= fdget_raw(dfd
);
1860 struct dentry
*dentry
;
1865 dentry
= f
.file
->f_path
.dentry
;
1868 if (!d_is_directory(dentry
)) {
1874 nd
->path
= f
.file
->f_path
;
1875 if (flags
& LOOKUP_RCU
) {
1878 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1881 path_get(&nd
->path
);
1886 nd
->inode
= nd
->path
.dentry
->d_inode
;
1890 static inline int lookup_last(struct nameidata
*nd
, struct path
*path
)
1892 if (nd
->last_type
== LAST_NORM
&& nd
->last
.name
[nd
->last
.len
])
1893 nd
->flags
|= LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
;
1895 nd
->flags
&= ~LOOKUP_PARENT
;
1896 return walk_component(nd
, path
, nd
->flags
& LOOKUP_FOLLOW
);
1899 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
1900 static int path_lookupat(int dfd
, const char *name
,
1901 unsigned int flags
, struct nameidata
*nd
)
1903 struct file
*base
= NULL
;
1908 * Path walking is largely split up into 2 different synchronisation
1909 * schemes, rcu-walk and ref-walk (explained in
1910 * Documentation/filesystems/path-lookup.txt). These share much of the
1911 * path walk code, but some things particularly setup, cleanup, and
1912 * following mounts are sufficiently divergent that functions are
1913 * duplicated. Typically there is a function foo(), and its RCU
1914 * analogue, foo_rcu().
1916 * -ECHILD is the error number of choice (just to avoid clashes) that
1917 * is returned if some aspect of an rcu-walk fails. Such an error must
1918 * be handled by restarting a traditional ref-walk (which will always
1919 * be able to complete).
1921 err
= path_init(dfd
, name
, flags
| LOOKUP_PARENT
, nd
, &base
);
1926 current
->total_link_count
= 0;
1927 err
= link_path_walk(name
, nd
);
1929 if (!err
&& !(flags
& LOOKUP_PARENT
)) {
1930 err
= lookup_last(nd
, &path
);
1933 struct path link
= path
;
1934 err
= may_follow_link(&link
, nd
);
1937 nd
->flags
|= LOOKUP_PARENT
;
1938 err
= follow_link(&link
, nd
, &cookie
);
1941 err
= lookup_last(nd
, &path
);
1942 put_link(nd
, &link
, cookie
);
1947 err
= complete_walk(nd
);
1949 if (!err
&& nd
->flags
& LOOKUP_DIRECTORY
) {
1950 if (!d_is_directory(nd
->path
.dentry
)) {
1951 path_put(&nd
->path
);
1959 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
)) {
1960 path_put(&nd
->root
);
1961 nd
->root
.mnt
= NULL
;
1966 static int filename_lookup(int dfd
, struct filename
*name
,
1967 unsigned int flags
, struct nameidata
*nd
)
1969 int retval
= path_lookupat(dfd
, name
->name
, flags
| LOOKUP_RCU
, nd
);
1970 if (unlikely(retval
== -ECHILD
))
1971 retval
= path_lookupat(dfd
, name
->name
, flags
, nd
);
1972 if (unlikely(retval
== -ESTALE
))
1973 retval
= path_lookupat(dfd
, name
->name
,
1974 flags
| LOOKUP_REVAL
, nd
);
1976 if (likely(!retval
))
1977 audit_inode(name
, nd
->path
.dentry
, flags
& LOOKUP_PARENT
);
1981 static int do_path_lookup(int dfd
, const char *name
,
1982 unsigned int flags
, struct nameidata
*nd
)
1984 struct filename filename
= { .name
= name
};
1986 return filename_lookup(dfd
, &filename
, flags
, nd
);
1989 /* does lookup, returns the object with parent locked */
1990 struct dentry
*kern_path_locked(const char *name
, struct path
*path
)
1992 struct nameidata nd
;
1994 int err
= do_path_lookup(AT_FDCWD
, name
, LOOKUP_PARENT
, &nd
);
1996 return ERR_PTR(err
);
1997 if (nd
.last_type
!= LAST_NORM
) {
1999 return ERR_PTR(-EINVAL
);
2001 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2002 d
= __lookup_hash(&nd
.last
, nd
.path
.dentry
, 0);
2004 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
2012 int kern_path(const char *name
, unsigned int flags
, struct path
*path
)
2014 struct nameidata nd
;
2015 int res
= do_path_lookup(AT_FDCWD
, name
, flags
, &nd
);
2022 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
2023 * @dentry: pointer to dentry of the base directory
2024 * @mnt: pointer to vfs mount of the base directory
2025 * @name: pointer to file name
2026 * @flags: lookup flags
2027 * @path: pointer to struct path to fill
2029 int vfs_path_lookup(struct dentry
*dentry
, struct vfsmount
*mnt
,
2030 const char *name
, unsigned int flags
,
2033 struct nameidata nd
;
2035 nd
.root
.dentry
= dentry
;
2037 BUG_ON(flags
& LOOKUP_PARENT
);
2038 /* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */
2039 err
= do_path_lookup(AT_FDCWD
, name
, flags
| LOOKUP_ROOT
, &nd
);
2046 * Restricted form of lookup. Doesn't follow links, single-component only,
2047 * needs parent already locked. Doesn't follow mounts.
2050 static struct dentry
*lookup_hash(struct nameidata
*nd
)
2052 return __lookup_hash(&nd
->last
, nd
->path
.dentry
, nd
->flags
);
2056 * lookup_one_len - filesystem helper to lookup single pathname component
2057 * @name: pathname component to lookup
2058 * @base: base directory to lookup from
2059 * @len: maximum length @len should be interpreted to
2061 * Note that this routine is purely a helper for filesystem usage and should
2062 * not be called by generic code. Also note that by using this function the
2063 * nameidata argument is passed to the filesystem methods and a filesystem
2064 * using this helper needs to be prepared for that.
2066 struct dentry
*lookup_one_len(const char *name
, struct dentry
*base
, int len
)
2072 WARN_ON_ONCE(!mutex_is_locked(&base
->d_inode
->i_mutex
));
2076 this.hash
= full_name_hash(name
, len
);
2078 return ERR_PTR(-EACCES
);
2080 if (unlikely(name
[0] == '.')) {
2081 if (len
< 2 || (len
== 2 && name
[1] == '.'))
2082 return ERR_PTR(-EACCES
);
2086 c
= *(const unsigned char *)name
++;
2087 if (c
== '/' || c
== '\0')
2088 return ERR_PTR(-EACCES
);
2091 * See if the low-level filesystem might want
2092 * to use its own hash..
2094 if (base
->d_flags
& DCACHE_OP_HASH
) {
2095 int err
= base
->d_op
->d_hash(base
, &this);
2097 return ERR_PTR(err
);
2100 err
= inode_permission(base
->d_inode
, MAY_EXEC
);
2102 return ERR_PTR(err
);
2104 return __lookup_hash(&this, base
, 0);
2107 int user_path_at_empty(int dfd
, const char __user
*name
, unsigned flags
,
2108 struct path
*path
, int *empty
)
2110 struct nameidata nd
;
2111 struct filename
*tmp
= getname_flags(name
, flags
, empty
);
2112 int err
= PTR_ERR(tmp
);
2115 BUG_ON(flags
& LOOKUP_PARENT
);
2117 err
= filename_lookup(dfd
, tmp
, flags
, &nd
);
2125 int user_path_at(int dfd
, const char __user
*name
, unsigned flags
,
2128 return user_path_at_empty(dfd
, name
, flags
, path
, NULL
);
2132 * NB: most callers don't do anything directly with the reference to the
2133 * to struct filename, but the nd->last pointer points into the name string
2134 * allocated by getname. So we must hold the reference to it until all
2135 * path-walking is complete.
2137 static struct filename
*
2138 user_path_parent(int dfd
, const char __user
*path
, struct nameidata
*nd
,
2141 struct filename
*s
= getname(path
);
2144 /* only LOOKUP_REVAL is allowed in extra flags */
2145 flags
&= LOOKUP_REVAL
;
2150 error
= filename_lookup(dfd
, s
, flags
| LOOKUP_PARENT
, nd
);
2153 return ERR_PTR(error
);
2160 * mountpoint_last - look up last component for umount
2161 * @nd: pathwalk nameidata - currently pointing at parent directory of "last"
2162 * @path: pointer to container for result
2164 * This is a special lookup_last function just for umount. In this case, we
2165 * need to resolve the path without doing any revalidation.
2167 * The nameidata should be the result of doing a LOOKUP_PARENT pathwalk. Since
2168 * mountpoints are always pinned in the dcache, their ancestors are too. Thus,
2169 * in almost all cases, this lookup will be served out of the dcache. The only
2170 * cases where it won't are if nd->last refers to a symlink or the path is
2171 * bogus and it doesn't exist.
2174 * -error: if there was an error during lookup. This includes -ENOENT if the
2175 * lookup found a negative dentry. The nd->path reference will also be
2178 * 0: if we successfully resolved nd->path and found it to not to be a
2179 * symlink that needs to be followed. "path" will also be populated.
2180 * The nd->path reference will also be put.
2182 * 1: if we successfully resolved nd->last and found it to be a symlink
2183 * that needs to be followed. "path" will be populated with the path
2184 * to the link, and nd->path will *not* be put.
2187 mountpoint_last(struct nameidata
*nd
, struct path
*path
)
2190 struct dentry
*dentry
;
2191 struct dentry
*dir
= nd
->path
.dentry
;
2193 /* If we're in rcuwalk, drop out of it to handle last component */
2194 if (nd
->flags
& LOOKUP_RCU
) {
2195 if (unlazy_walk(nd
, NULL
)) {
2201 nd
->flags
&= ~LOOKUP_PARENT
;
2203 if (unlikely(nd
->last_type
!= LAST_NORM
)) {
2204 error
= handle_dots(nd
, nd
->last_type
);
2207 dentry
= dget(nd
->path
.dentry
);
2211 mutex_lock(&dir
->d_inode
->i_mutex
);
2212 dentry
= d_lookup(dir
, &nd
->last
);
2215 * No cached dentry. Mounted dentries are pinned in the cache,
2216 * so that means that this dentry is probably a symlink or the
2217 * path doesn't actually point to a mounted dentry.
2219 dentry
= d_alloc(dir
, &nd
->last
);
2222 mutex_unlock(&dir
->d_inode
->i_mutex
);
2225 dentry
= lookup_real(dir
->d_inode
, dentry
, nd
->flags
);
2226 error
= PTR_ERR(dentry
);
2227 if (IS_ERR(dentry
)) {
2228 mutex_unlock(&dir
->d_inode
->i_mutex
);
2232 mutex_unlock(&dir
->d_inode
->i_mutex
);
2235 if (!dentry
->d_inode
) {
2240 path
->dentry
= dentry
;
2241 path
->mnt
= mntget(nd
->path
.mnt
);
2242 if (should_follow_link(dentry
, nd
->flags
& LOOKUP_FOLLOW
))
2252 * path_mountpoint - look up a path to be umounted
2253 * @dfd: directory file descriptor to start walk from
2254 * @name: full pathname to walk
2255 * @path: pointer to container for result
2256 * @flags: lookup flags
2258 * Look up the given name, but don't attempt to revalidate the last component.
2259 * Returns 0 and "path" will be valid on success; Returns error otherwise.
2262 path_mountpoint(int dfd
, const char *name
, struct path
*path
, unsigned int flags
)
2264 struct file
*base
= NULL
;
2265 struct nameidata nd
;
2268 err
= path_init(dfd
, name
, flags
| LOOKUP_PARENT
, &nd
, &base
);
2272 current
->total_link_count
= 0;
2273 err
= link_path_walk(name
, &nd
);
2277 err
= mountpoint_last(&nd
, path
);
2280 struct path link
= *path
;
2281 err
= may_follow_link(&link
, &nd
);
2284 nd
.flags
|= LOOKUP_PARENT
;
2285 err
= follow_link(&link
, &nd
, &cookie
);
2288 err
= mountpoint_last(&nd
, path
);
2289 put_link(&nd
, &link
, cookie
);
2295 if (nd
.root
.mnt
&& !(nd
.flags
& LOOKUP_ROOT
))
2302 filename_mountpoint(int dfd
, struct filename
*s
, struct path
*path
,
2305 int error
= path_mountpoint(dfd
, s
->name
, path
, flags
| LOOKUP_RCU
);
2306 if (unlikely(error
== -ECHILD
))
2307 error
= path_mountpoint(dfd
, s
->name
, path
, flags
);
2308 if (unlikely(error
== -ESTALE
))
2309 error
= path_mountpoint(dfd
, s
->name
, path
, flags
| LOOKUP_REVAL
);
2311 audit_inode(s
, path
->dentry
, 0);
2316 * user_path_mountpoint_at - lookup a path from userland in order to umount it
2317 * @dfd: directory file descriptor
2318 * @name: pathname from userland
2319 * @flags: lookup flags
2320 * @path: pointer to container to hold result
2322 * A umount is a special case for path walking. We're not actually interested
2323 * in the inode in this situation, and ESTALE errors can be a problem. We
2324 * simply want track down the dentry and vfsmount attached at the mountpoint
2325 * and avoid revalidating the last component.
2327 * Returns 0 and populates "path" on success.
2330 user_path_mountpoint_at(int dfd
, const char __user
*name
, unsigned int flags
,
2333 struct filename
*s
= getname(name
);
2337 error
= filename_mountpoint(dfd
, s
, path
, flags
);
2343 kern_path_mountpoint(int dfd
, const char *name
, struct path
*path
,
2346 struct filename s
= {.name
= name
};
2347 return filename_mountpoint(dfd
, &s
, path
, flags
);
2349 EXPORT_SYMBOL(kern_path_mountpoint
);
2352 * It's inline, so penalty for filesystems that don't use sticky bit is
2355 static inline int check_sticky(struct inode
*dir
, struct inode
*inode
)
2357 kuid_t fsuid
= current_fsuid();
2359 if (!(dir
->i_mode
& S_ISVTX
))
2361 if (uid_eq(inode
->i_uid
, fsuid
))
2363 if (uid_eq(dir
->i_uid
, fsuid
))
2365 return !inode_capable(inode
, CAP_FOWNER
);
2369 * Check whether we can remove a link victim from directory dir, check
2370 * whether the type of victim is right.
2371 * 1. We can't do it if dir is read-only (done in permission())
2372 * 2. We should have write and exec permissions on dir
2373 * 3. We can't remove anything from append-only dir
2374 * 4. We can't do anything with immutable dir (done in permission())
2375 * 5. If the sticky bit on dir is set we should either
2376 * a. be owner of dir, or
2377 * b. be owner of victim, or
2378 * c. have CAP_FOWNER capability
2379 * 6. If the victim is append-only or immutable we can't do antyhing with
2380 * links pointing to it.
2381 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
2382 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
2383 * 9. We can't remove a root or mountpoint.
2384 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
2385 * nfs_async_unlink().
2387 static int may_delete(struct inode
*dir
, struct dentry
*victim
, bool isdir
)
2389 struct inode
*inode
= victim
->d_inode
;
2392 if (d_is_negative(victim
))
2396 BUG_ON(victim
->d_parent
->d_inode
!= dir
);
2397 audit_inode_child(dir
, victim
, AUDIT_TYPE_CHILD_DELETE
);
2399 error
= inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
2405 if (check_sticky(dir
, inode
) || IS_APPEND(inode
) ||
2406 IS_IMMUTABLE(inode
) || IS_SWAPFILE(inode
))
2409 if (!d_is_directory(victim
) && !d_is_autodir(victim
))
2411 if (IS_ROOT(victim
))
2413 } else if (d_is_directory(victim
) || d_is_autodir(victim
))
2415 if (IS_DEADDIR(dir
))
2417 if (victim
->d_flags
& DCACHE_NFSFS_RENAMED
)
2422 /* Check whether we can create an object with dentry child in directory
2424 * 1. We can't do it if child already exists (open has special treatment for
2425 * this case, but since we are inlined it's OK)
2426 * 2. We can't do it if dir is read-only (done in permission())
2427 * 3. We should have write and exec permissions on dir
2428 * 4. We can't do it if dir is immutable (done in permission())
2430 static inline int may_create(struct inode
*dir
, struct dentry
*child
)
2432 audit_inode_child(dir
, child
, AUDIT_TYPE_CHILD_CREATE
);
2435 if (IS_DEADDIR(dir
))
2437 return inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
2441 * p1 and p2 should be directories on the same fs.
2443 struct dentry
*lock_rename(struct dentry
*p1
, struct dentry
*p2
)
2448 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2452 mutex_lock(&p1
->d_inode
->i_sb
->s_vfs_rename_mutex
);
2454 p
= d_ancestor(p2
, p1
);
2456 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2457 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_CHILD
);
2461 p
= d_ancestor(p1
, p2
);
2463 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2464 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_CHILD
);
2468 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2469 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_CHILD
);
2473 void unlock_rename(struct dentry
*p1
, struct dentry
*p2
)
2475 mutex_unlock(&p1
->d_inode
->i_mutex
);
2477 mutex_unlock(&p2
->d_inode
->i_mutex
);
2478 mutex_unlock(&p1
->d_inode
->i_sb
->s_vfs_rename_mutex
);
2482 int vfs_create(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
,
2485 int error
= may_create(dir
, dentry
);
2489 if (!dir
->i_op
->create
)
2490 return -EACCES
; /* shouldn't it be ENOSYS? */
2493 error
= security_inode_create(dir
, dentry
, mode
);
2496 error
= dir
->i_op
->create(dir
, dentry
, mode
, want_excl
);
2498 fsnotify_create(dir
, dentry
);
2502 static int may_open(struct path
*path
, int acc_mode
, int flag
)
2504 struct dentry
*dentry
= path
->dentry
;
2505 struct inode
*inode
= dentry
->d_inode
;
2515 switch (inode
->i_mode
& S_IFMT
) {
2519 if (acc_mode
& MAY_WRITE
)
2524 if (path
->mnt
->mnt_flags
& MNT_NODEV
)
2533 error
= inode_permission(inode
, acc_mode
);
2538 * An append-only file must be opened in append mode for writing.
2540 if (IS_APPEND(inode
)) {
2541 if ((flag
& O_ACCMODE
) != O_RDONLY
&& !(flag
& O_APPEND
))
2547 /* O_NOATIME can only be set by the owner or superuser */
2548 if (flag
& O_NOATIME
&& !inode_owner_or_capable(inode
))
2554 static int handle_truncate(struct file
*filp
)
2556 struct path
*path
= &filp
->f_path
;
2557 struct inode
*inode
= path
->dentry
->d_inode
;
2558 int error
= get_write_access(inode
);
2562 * Refuse to truncate files with mandatory locks held on them.
2564 error
= locks_verify_locked(inode
);
2566 error
= security_path_truncate(path
);
2568 error
= do_truncate(path
->dentry
, 0,
2569 ATTR_MTIME
|ATTR_CTIME
|ATTR_OPEN
,
2572 put_write_access(inode
);
2576 static inline int open_to_namei_flags(int flag
)
2578 if ((flag
& O_ACCMODE
) == 3)
2583 static int may_o_create(struct path
*dir
, struct dentry
*dentry
, umode_t mode
)
2585 int error
= security_path_mknod(dir
, dentry
, mode
, 0);
2589 error
= inode_permission(dir
->dentry
->d_inode
, MAY_WRITE
| MAY_EXEC
);
2593 return security_inode_create(dir
->dentry
->d_inode
, dentry
, mode
);
2597 * Attempt to atomically look up, create and open a file from a negative
2600 * Returns 0 if successful. The file will have been created and attached to
2601 * @file by the filesystem calling finish_open().
2603 * Returns 1 if the file was looked up only or didn't need creating. The
2604 * caller will need to perform the open themselves. @path will have been
2605 * updated to point to the new dentry. This may be negative.
2607 * Returns an error code otherwise.
2609 static int atomic_open(struct nameidata
*nd
, struct dentry
*dentry
,
2610 struct path
*path
, struct file
*file
,
2611 const struct open_flags
*op
,
2612 bool got_write
, bool need_lookup
,
2615 struct inode
*dir
= nd
->path
.dentry
->d_inode
;
2616 unsigned open_flag
= open_to_namei_flags(op
->open_flag
);
2620 int create_error
= 0;
2621 struct dentry
*const DENTRY_NOT_SET
= (void *) -1UL;
2624 BUG_ON(dentry
->d_inode
);
2626 /* Don't create child dentry for a dead directory. */
2627 if (unlikely(IS_DEADDIR(dir
))) {
2633 if ((open_flag
& O_CREAT
) && !IS_POSIXACL(dir
))
2634 mode
&= ~current_umask();
2636 excl
= (open_flag
& (O_EXCL
| O_CREAT
)) == (O_EXCL
| O_CREAT
);
2638 open_flag
&= ~O_TRUNC
;
2641 * Checking write permission is tricky, bacuse we don't know if we are
2642 * going to actually need it: O_CREAT opens should work as long as the
2643 * file exists. But checking existence breaks atomicity. The trick is
2644 * to check access and if not granted clear O_CREAT from the flags.
2646 * Another problem is returing the "right" error value (e.g. for an
2647 * O_EXCL open we want to return EEXIST not EROFS).
2649 if (((open_flag
& (O_CREAT
| O_TRUNC
)) ||
2650 (open_flag
& O_ACCMODE
) != O_RDONLY
) && unlikely(!got_write
)) {
2651 if (!(open_flag
& O_CREAT
)) {
2653 * No O_CREATE -> atomicity not a requirement -> fall
2654 * back to lookup + open
2657 } else if (open_flag
& (O_EXCL
| O_TRUNC
)) {
2658 /* Fall back and fail with the right error */
2659 create_error
= -EROFS
;
2662 /* No side effects, safe to clear O_CREAT */
2663 create_error
= -EROFS
;
2664 open_flag
&= ~O_CREAT
;
2668 if (open_flag
& O_CREAT
) {
2669 error
= may_o_create(&nd
->path
, dentry
, mode
);
2671 create_error
= error
;
2672 if (open_flag
& O_EXCL
)
2674 open_flag
&= ~O_CREAT
;
2678 if (nd
->flags
& LOOKUP_DIRECTORY
)
2679 open_flag
|= O_DIRECTORY
;
2681 file
->f_path
.dentry
= DENTRY_NOT_SET
;
2682 file
->f_path
.mnt
= nd
->path
.mnt
;
2683 error
= dir
->i_op
->atomic_open(dir
, dentry
, file
, open_flag
, mode
,
2686 if (create_error
&& error
== -ENOENT
)
2687 error
= create_error
;
2691 if (error
) { /* returned 1, that is */
2692 if (WARN_ON(file
->f_path
.dentry
== DENTRY_NOT_SET
)) {
2696 if (file
->f_path
.dentry
) {
2698 dentry
= file
->f_path
.dentry
;
2700 if (*opened
& FILE_CREATED
)
2701 fsnotify_create(dir
, dentry
);
2702 if (!dentry
->d_inode
) {
2703 WARN_ON(*opened
& FILE_CREATED
);
2705 error
= create_error
;
2709 if (excl
&& !(*opened
& FILE_CREATED
)) {
2718 * We didn't have the inode before the open, so check open permission
2721 acc_mode
= op
->acc_mode
;
2722 if (*opened
& FILE_CREATED
) {
2723 WARN_ON(!(open_flag
& O_CREAT
));
2724 fsnotify_create(dir
, dentry
);
2725 acc_mode
= MAY_OPEN
;
2727 error
= may_open(&file
->f_path
, acc_mode
, open_flag
);
2737 dentry
= lookup_real(dir
, dentry
, nd
->flags
);
2739 return PTR_ERR(dentry
);
2742 int open_flag
= op
->open_flag
;
2744 error
= create_error
;
2745 if ((open_flag
& O_EXCL
)) {
2746 if (!dentry
->d_inode
)
2748 } else if (!dentry
->d_inode
) {
2750 } else if ((open_flag
& O_TRUNC
) &&
2751 S_ISREG(dentry
->d_inode
->i_mode
)) {
2754 /* will fail later, go on to get the right error */
2758 path
->dentry
= dentry
;
2759 path
->mnt
= nd
->path
.mnt
;
2764 * Look up and maybe create and open the last component.
2766 * Must be called with i_mutex held on parent.
2768 * Returns 0 if the file was successfully atomically created (if necessary) and
2769 * opened. In this case the file will be returned attached to @file.
2771 * Returns 1 if the file was not completely opened at this time, though lookups
2772 * and creations will have been performed and the dentry returned in @path will
2773 * be positive upon return if O_CREAT was specified. If O_CREAT wasn't
2774 * specified then a negative dentry may be returned.
2776 * An error code is returned otherwise.
2778 * FILE_CREATE will be set in @*opened if the dentry was created and will be
2779 * cleared otherwise prior to returning.
2781 static int lookup_open(struct nameidata
*nd
, struct path
*path
,
2783 const struct open_flags
*op
,
2784 bool got_write
, int *opened
)
2786 struct dentry
*dir
= nd
->path
.dentry
;
2787 struct inode
*dir_inode
= dir
->d_inode
;
2788 struct dentry
*dentry
;
2792 *opened
&= ~FILE_CREATED
;
2793 dentry
= lookup_dcache(&nd
->last
, dir
, nd
->flags
, &need_lookup
);
2795 return PTR_ERR(dentry
);
2797 /* Cached positive dentry: will open in f_op->open */
2798 if (!need_lookup
&& dentry
->d_inode
)
2801 if ((nd
->flags
& LOOKUP_OPEN
) && dir_inode
->i_op
->atomic_open
) {
2802 return atomic_open(nd
, dentry
, path
, file
, op
, got_write
,
2803 need_lookup
, opened
);
2807 BUG_ON(dentry
->d_inode
);
2809 dentry
= lookup_real(dir_inode
, dentry
, nd
->flags
);
2811 return PTR_ERR(dentry
);
2814 /* Negative dentry, just create the file */
2815 if (!dentry
->d_inode
&& (op
->open_flag
& O_CREAT
)) {
2816 umode_t mode
= op
->mode
;
2817 if (!IS_POSIXACL(dir
->d_inode
))
2818 mode
&= ~current_umask();
2820 * This write is needed to ensure that a
2821 * rw->ro transition does not occur between
2822 * the time when the file is created and when
2823 * a permanent write count is taken through
2824 * the 'struct file' in finish_open().
2830 *opened
|= FILE_CREATED
;
2831 error
= security_path_mknod(&nd
->path
, dentry
, mode
, 0);
2834 error
= vfs_create(dir
->d_inode
, dentry
, mode
,
2835 nd
->flags
& LOOKUP_EXCL
);
2840 path
->dentry
= dentry
;
2841 path
->mnt
= nd
->path
.mnt
;
2850 * Handle the last step of open()
2852 static int do_last(struct nameidata
*nd
, struct path
*path
,
2853 struct file
*file
, const struct open_flags
*op
,
2854 int *opened
, struct filename
*name
)
2856 struct dentry
*dir
= nd
->path
.dentry
;
2857 int open_flag
= op
->open_flag
;
2858 bool will_truncate
= (open_flag
& O_TRUNC
) != 0;
2859 bool got_write
= false;
2860 int acc_mode
= op
->acc_mode
;
2861 struct inode
*inode
;
2862 bool symlink_ok
= false;
2863 struct path save_parent
= { .dentry
= NULL
, .mnt
= NULL
};
2864 bool retried
= false;
2867 nd
->flags
&= ~LOOKUP_PARENT
;
2868 nd
->flags
|= op
->intent
;
2870 if (nd
->last_type
!= LAST_NORM
) {
2871 error
= handle_dots(nd
, nd
->last_type
);
2877 if (!(open_flag
& O_CREAT
)) {
2878 if (nd
->last
.name
[nd
->last
.len
])
2879 nd
->flags
|= LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
;
2880 if (open_flag
& O_PATH
&& !(nd
->flags
& LOOKUP_FOLLOW
))
2882 /* we _can_ be in RCU mode here */
2883 error
= lookup_fast(nd
, path
, &inode
);
2890 BUG_ON(nd
->inode
!= dir
->d_inode
);
2892 /* create side of things */
2894 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED
2895 * has been cleared when we got to the last component we are
2898 error
= complete_walk(nd
);
2902 audit_inode(name
, dir
, LOOKUP_PARENT
);
2904 /* trailing slashes? */
2905 if (nd
->last
.name
[nd
->last
.len
])
2910 if (op
->open_flag
& (O_CREAT
| O_TRUNC
| O_WRONLY
| O_RDWR
)) {
2911 error
= mnt_want_write(nd
->path
.mnt
);
2915 * do _not_ fail yet - we might not need that or fail with
2916 * a different error; let lookup_open() decide; we'll be
2917 * dropping this one anyway.
2920 mutex_lock(&dir
->d_inode
->i_mutex
);
2921 error
= lookup_open(nd
, path
, file
, op
, got_write
, opened
);
2922 mutex_unlock(&dir
->d_inode
->i_mutex
);
2928 if ((*opened
& FILE_CREATED
) ||
2929 !S_ISREG(file_inode(file
)->i_mode
))
2930 will_truncate
= false;
2932 audit_inode(name
, file
->f_path
.dentry
, 0);
2936 if (*opened
& FILE_CREATED
) {
2937 /* Don't check for write permission, don't truncate */
2938 open_flag
&= ~O_TRUNC
;
2939 will_truncate
= false;
2940 acc_mode
= MAY_OPEN
;
2941 path_to_nameidata(path
, nd
);
2942 goto finish_open_created
;
2946 * create/update audit record if it already exists.
2948 if (d_is_positive(path
->dentry
))
2949 audit_inode(name
, path
->dentry
, 0);
2952 * If atomic_open() acquired write access it is dropped now due to
2953 * possible mount and symlink following (this might be optimized away if
2957 mnt_drop_write(nd
->path
.mnt
);
2962 if ((open_flag
& (O_EXCL
| O_CREAT
)) == (O_EXCL
| O_CREAT
))
2965 error
= follow_managed(path
, nd
->flags
);
2970 nd
->flags
|= LOOKUP_JUMPED
;
2972 BUG_ON(nd
->flags
& LOOKUP_RCU
);
2973 inode
= path
->dentry
->d_inode
;
2975 /* we _can_ be in RCU mode here */
2977 if (d_is_negative(path
->dentry
)) {
2978 path_to_nameidata(path
, nd
);
2982 if (should_follow_link(path
->dentry
, !symlink_ok
)) {
2983 if (nd
->flags
& LOOKUP_RCU
) {
2984 if (unlikely(unlazy_walk(nd
, path
->dentry
))) {
2989 BUG_ON(inode
!= path
->dentry
->d_inode
);
2993 if ((nd
->flags
& LOOKUP_RCU
) || nd
->path
.mnt
!= path
->mnt
) {
2994 path_to_nameidata(path
, nd
);
2996 save_parent
.dentry
= nd
->path
.dentry
;
2997 save_parent
.mnt
= mntget(path
->mnt
);
2998 nd
->path
.dentry
= path
->dentry
;
3002 /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
3004 error
= complete_walk(nd
);
3006 path_put(&save_parent
);
3009 audit_inode(name
, nd
->path
.dentry
, 0);
3011 if ((open_flag
& O_CREAT
) &&
3012 (d_is_directory(nd
->path
.dentry
) || d_is_autodir(nd
->path
.dentry
)))
3015 if ((nd
->flags
& LOOKUP_DIRECTORY
) && !d_is_directory(nd
->path
.dentry
))
3017 if (!S_ISREG(nd
->inode
->i_mode
))
3018 will_truncate
= false;
3020 if (will_truncate
) {
3021 error
= mnt_want_write(nd
->path
.mnt
);
3026 finish_open_created
:
3027 error
= may_open(&nd
->path
, acc_mode
, open_flag
);
3030 file
->f_path
.mnt
= nd
->path
.mnt
;
3031 error
= finish_open(file
, nd
->path
.dentry
, NULL
, opened
);
3033 if (error
== -EOPENSTALE
)
3038 error
= open_check_o_direct(file
);
3041 error
= ima_file_check(file
, op
->acc_mode
);
3045 if (will_truncate
) {
3046 error
= handle_truncate(file
);
3052 mnt_drop_write(nd
->path
.mnt
);
3053 path_put(&save_parent
);
3058 path_put_conditional(path
, nd
);
3065 /* If no saved parent or already retried then can't retry */
3066 if (!save_parent
.dentry
|| retried
)
3069 BUG_ON(save_parent
.dentry
!= dir
);
3070 path_put(&nd
->path
);
3071 nd
->path
= save_parent
;
3072 nd
->inode
= dir
->d_inode
;
3073 save_parent
.mnt
= NULL
;
3074 save_parent
.dentry
= NULL
;
3076 mnt_drop_write(nd
->path
.mnt
);
3083 static int do_tmpfile(int dfd
, struct filename
*pathname
,
3084 struct nameidata
*nd
, int flags
,
3085 const struct open_flags
*op
,
3086 struct file
*file
, int *opened
)
3088 static const struct qstr name
= QSTR_INIT("/", 1);
3089 struct dentry
*dentry
, *child
;
3091 int error
= path_lookupat(dfd
, pathname
->name
,
3092 flags
| LOOKUP_DIRECTORY
, nd
);
3093 if (unlikely(error
))
3095 error
= mnt_want_write(nd
->path
.mnt
);
3096 if (unlikely(error
))
3098 /* we want directory to be writable */
3099 error
= inode_permission(nd
->inode
, MAY_WRITE
| MAY_EXEC
);
3102 dentry
= nd
->path
.dentry
;
3103 dir
= dentry
->d_inode
;
3104 if (!dir
->i_op
->tmpfile
) {
3105 error
= -EOPNOTSUPP
;
3108 child
= d_alloc(dentry
, &name
);
3109 if (unlikely(!child
)) {
3113 nd
->flags
&= ~LOOKUP_DIRECTORY
;
3114 nd
->flags
|= op
->intent
;
3115 dput(nd
->path
.dentry
);
3116 nd
->path
.dentry
= child
;
3117 error
= dir
->i_op
->tmpfile(dir
, nd
->path
.dentry
, op
->mode
);
3120 audit_inode(pathname
, nd
->path
.dentry
, 0);
3121 error
= may_open(&nd
->path
, op
->acc_mode
, op
->open_flag
);
3124 file
->f_path
.mnt
= nd
->path
.mnt
;
3125 error
= finish_open(file
, nd
->path
.dentry
, NULL
, opened
);
3128 error
= open_check_o_direct(file
);
3131 } else if (!(op
->open_flag
& O_EXCL
)) {
3132 struct inode
*inode
= file_inode(file
);
3133 spin_lock(&inode
->i_lock
);
3134 inode
->i_state
|= I_LINKABLE
;
3135 spin_unlock(&inode
->i_lock
);
3138 mnt_drop_write(nd
->path
.mnt
);
3140 path_put(&nd
->path
);
3144 static struct file
*path_openat(int dfd
, struct filename
*pathname
,
3145 struct nameidata
*nd
, const struct open_flags
*op
, int flags
)
3147 struct file
*base
= NULL
;
3153 file
= get_empty_filp();
3157 file
->f_flags
= op
->open_flag
;
3159 if (unlikely(file
->f_flags
& __O_TMPFILE
)) {
3160 error
= do_tmpfile(dfd
, pathname
, nd
, flags
, op
, file
, &opened
);
3164 error
= path_init(dfd
, pathname
->name
, flags
| LOOKUP_PARENT
, nd
, &base
);
3165 if (unlikely(error
))
3168 current
->total_link_count
= 0;
3169 error
= link_path_walk(pathname
->name
, nd
);
3170 if (unlikely(error
))
3173 error
= do_last(nd
, &path
, file
, op
, &opened
, pathname
);
3174 while (unlikely(error
> 0)) { /* trailing symlink */
3175 struct path link
= path
;
3177 if (!(nd
->flags
& LOOKUP_FOLLOW
)) {
3178 path_put_conditional(&path
, nd
);
3179 path_put(&nd
->path
);
3183 error
= may_follow_link(&link
, nd
);
3184 if (unlikely(error
))
3186 nd
->flags
|= LOOKUP_PARENT
;
3187 nd
->flags
&= ~(LOOKUP_OPEN
|LOOKUP_CREATE
|LOOKUP_EXCL
);
3188 error
= follow_link(&link
, nd
, &cookie
);
3189 if (unlikely(error
))
3191 error
= do_last(nd
, &path
, file
, op
, &opened
, pathname
);
3192 put_link(nd
, &link
, cookie
);
3195 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
))
3196 path_put(&nd
->root
);
3199 if (!(opened
& FILE_OPENED
)) {
3203 if (unlikely(error
)) {
3204 if (error
== -EOPENSTALE
) {
3205 if (flags
& LOOKUP_RCU
)
3210 file
= ERR_PTR(error
);
3215 struct file
*do_filp_open(int dfd
, struct filename
*pathname
,
3216 const struct open_flags
*op
)
3218 struct nameidata nd
;
3219 int flags
= op
->lookup_flags
;
3222 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
| LOOKUP_RCU
);
3223 if (unlikely(filp
== ERR_PTR(-ECHILD
)))
3224 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
);
3225 if (unlikely(filp
== ERR_PTR(-ESTALE
)))
3226 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
| LOOKUP_REVAL
);
3230 struct file
*do_file_open_root(struct dentry
*dentry
, struct vfsmount
*mnt
,
3231 const char *name
, const struct open_flags
*op
)
3233 struct nameidata nd
;
3235 struct filename filename
= { .name
= name
};
3236 int flags
= op
->lookup_flags
| LOOKUP_ROOT
;
3239 nd
.root
.dentry
= dentry
;
3241 if (d_is_symlink(dentry
) && op
->intent
& LOOKUP_OPEN
)
3242 return ERR_PTR(-ELOOP
);
3244 file
= path_openat(-1, &filename
, &nd
, op
, flags
| LOOKUP_RCU
);
3245 if (unlikely(file
== ERR_PTR(-ECHILD
)))
3246 file
= path_openat(-1, &filename
, &nd
, op
, flags
);
3247 if (unlikely(file
== ERR_PTR(-ESTALE
)))
3248 file
= path_openat(-1, &filename
, &nd
, op
, flags
| LOOKUP_REVAL
);
3252 struct dentry
*kern_path_create(int dfd
, const char *pathname
,
3253 struct path
*path
, unsigned int lookup_flags
)
3255 struct dentry
*dentry
= ERR_PTR(-EEXIST
);
3256 struct nameidata nd
;
3259 bool is_dir
= (lookup_flags
& LOOKUP_DIRECTORY
);
3262 * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any
3263 * other flags passed in are ignored!
3265 lookup_flags
&= LOOKUP_REVAL
;
3267 error
= do_path_lookup(dfd
, pathname
, LOOKUP_PARENT
|lookup_flags
, &nd
);
3269 return ERR_PTR(error
);
3272 * Yucky last component or no last component at all?
3273 * (foo/., foo/.., /////)
3275 if (nd
.last_type
!= LAST_NORM
)
3277 nd
.flags
&= ~LOOKUP_PARENT
;
3278 nd
.flags
|= LOOKUP_CREATE
| LOOKUP_EXCL
;
3280 /* don't fail immediately if it's r/o, at least try to report other errors */
3281 err2
= mnt_want_write(nd
.path
.mnt
);
3283 * Do the final lookup.
3285 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
3286 dentry
= lookup_hash(&nd
);
3291 if (d_is_positive(dentry
))
3295 * Special case - lookup gave negative, but... we had foo/bar/
3296 * From the vfs_mknod() POV we just have a negative dentry -
3297 * all is fine. Let's be bastards - you had / on the end, you've
3298 * been asking for (non-existent) directory. -ENOENT for you.
3300 if (unlikely(!is_dir
&& nd
.last
.name
[nd
.last
.len
])) {
3304 if (unlikely(err2
)) {
3312 dentry
= ERR_PTR(error
);
3314 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
3316 mnt_drop_write(nd
.path
.mnt
);
3321 EXPORT_SYMBOL(kern_path_create
);
3323 void done_path_create(struct path
*path
, struct dentry
*dentry
)
3326 mutex_unlock(&path
->dentry
->d_inode
->i_mutex
);
3327 mnt_drop_write(path
->mnt
);
3330 EXPORT_SYMBOL(done_path_create
);
3332 struct dentry
*user_path_create(int dfd
, const char __user
*pathname
,
3333 struct path
*path
, unsigned int lookup_flags
)
3335 struct filename
*tmp
= getname(pathname
);
3338 return ERR_CAST(tmp
);
3339 res
= kern_path_create(dfd
, tmp
->name
, path
, lookup_flags
);
3343 EXPORT_SYMBOL(user_path_create
);
3345 int vfs_mknod(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
, dev_t dev
)
3347 int error
= may_create(dir
, dentry
);
3352 if ((S_ISCHR(mode
) || S_ISBLK(mode
)) && !capable(CAP_MKNOD
))
3355 if (!dir
->i_op
->mknod
)
3358 error
= devcgroup_inode_mknod(mode
, dev
);
3362 error
= security_inode_mknod(dir
, dentry
, mode
, dev
);
3366 error
= dir
->i_op
->mknod(dir
, dentry
, mode
, dev
);
3368 fsnotify_create(dir
, dentry
);
3372 static int may_mknod(umode_t mode
)
3374 switch (mode
& S_IFMT
) {
3380 case 0: /* zero mode translates to S_IFREG */
3389 SYSCALL_DEFINE4(mknodat
, int, dfd
, const char __user
*, filename
, umode_t
, mode
,
3392 struct dentry
*dentry
;
3395 unsigned int lookup_flags
= 0;
3397 error
= may_mknod(mode
);
3401 dentry
= user_path_create(dfd
, filename
, &path
, lookup_flags
);
3403 return PTR_ERR(dentry
);
3405 if (!IS_POSIXACL(path
.dentry
->d_inode
))
3406 mode
&= ~current_umask();
3407 error
= security_path_mknod(&path
, dentry
, mode
, dev
);
3410 switch (mode
& S_IFMT
) {
3411 case 0: case S_IFREG
:
3412 error
= vfs_create(path
.dentry
->d_inode
,dentry
,mode
,true);
3414 case S_IFCHR
: case S_IFBLK
:
3415 error
= vfs_mknod(path
.dentry
->d_inode
,dentry
,mode
,
3416 new_decode_dev(dev
));
3418 case S_IFIFO
: case S_IFSOCK
:
3419 error
= vfs_mknod(path
.dentry
->d_inode
,dentry
,mode
,0);
3423 done_path_create(&path
, dentry
);
3424 if (retry_estale(error
, lookup_flags
)) {
3425 lookup_flags
|= LOOKUP_REVAL
;
3431 SYSCALL_DEFINE3(mknod
, const char __user
*, filename
, umode_t
, mode
, unsigned, dev
)
3433 return sys_mknodat(AT_FDCWD
, filename
, mode
, dev
);
3436 int vfs_mkdir(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
)
3438 int error
= may_create(dir
, dentry
);
3439 unsigned max_links
= dir
->i_sb
->s_max_links
;
3444 if (!dir
->i_op
->mkdir
)
3447 mode
&= (S_IRWXUGO
|S_ISVTX
);
3448 error
= security_inode_mkdir(dir
, dentry
, mode
);
3452 if (max_links
&& dir
->i_nlink
>= max_links
)
3455 error
= dir
->i_op
->mkdir(dir
, dentry
, mode
);
3457 fsnotify_mkdir(dir
, dentry
);
3461 SYSCALL_DEFINE3(mkdirat
, int, dfd
, const char __user
*, pathname
, umode_t
, mode
)
3463 struct dentry
*dentry
;
3466 unsigned int lookup_flags
= LOOKUP_DIRECTORY
;
3469 dentry
= user_path_create(dfd
, pathname
, &path
, lookup_flags
);
3471 return PTR_ERR(dentry
);
3473 if (!IS_POSIXACL(path
.dentry
->d_inode
))
3474 mode
&= ~current_umask();
3475 error
= security_path_mkdir(&path
, dentry
, mode
);
3477 error
= vfs_mkdir(path
.dentry
->d_inode
, dentry
, mode
);
3478 done_path_create(&path
, dentry
);
3479 if (retry_estale(error
, lookup_flags
)) {
3480 lookup_flags
|= LOOKUP_REVAL
;
3486 SYSCALL_DEFINE2(mkdir
, const char __user
*, pathname
, umode_t
, mode
)
3488 return sys_mkdirat(AT_FDCWD
, pathname
, mode
);
3492 * The dentry_unhash() helper will try to drop the dentry early: we
3493 * should have a usage count of 1 if we're the only user of this
3494 * dentry, and if that is true (possibly after pruning the dcache),
3495 * then we drop the dentry now.
3497 * A low-level filesystem can, if it choses, legally
3500 * if (!d_unhashed(dentry))
3503 * if it cannot handle the case of removing a directory
3504 * that is still in use by something else..
3506 void dentry_unhash(struct dentry
*dentry
)
3508 shrink_dcache_parent(dentry
);
3509 spin_lock(&dentry
->d_lock
);
3510 if (dentry
->d_lockref
.count
== 1)
3512 spin_unlock(&dentry
->d_lock
);
3515 int vfs_rmdir(struct inode
*dir
, struct dentry
*dentry
)
3517 int error
= may_delete(dir
, dentry
, 1);
3522 if (!dir
->i_op
->rmdir
)
3526 mutex_lock(&dentry
->d_inode
->i_mutex
);
3529 if (d_mountpoint(dentry
))
3532 error
= security_inode_rmdir(dir
, dentry
);
3536 shrink_dcache_parent(dentry
);
3537 error
= dir
->i_op
->rmdir(dir
, dentry
);
3541 dentry
->d_inode
->i_flags
|= S_DEAD
;
3545 mutex_unlock(&dentry
->d_inode
->i_mutex
);
3552 static long do_rmdir(int dfd
, const char __user
*pathname
)
3555 struct filename
*name
;
3556 struct dentry
*dentry
;
3557 struct nameidata nd
;
3558 unsigned int lookup_flags
= 0;
3560 name
= user_path_parent(dfd
, pathname
, &nd
, lookup_flags
);
3562 return PTR_ERR(name
);
3564 switch(nd
.last_type
) {
3576 nd
.flags
&= ~LOOKUP_PARENT
;
3577 error
= mnt_want_write(nd
.path
.mnt
);
3581 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
3582 dentry
= lookup_hash(&nd
);
3583 error
= PTR_ERR(dentry
);
3586 if (!dentry
->d_inode
) {
3590 error
= security_path_rmdir(&nd
.path
, dentry
);
3593 error
= vfs_rmdir(nd
.path
.dentry
->d_inode
, dentry
);
3597 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
3598 mnt_drop_write(nd
.path
.mnt
);
3602 if (retry_estale(error
, lookup_flags
)) {
3603 lookup_flags
|= LOOKUP_REVAL
;
3609 SYSCALL_DEFINE1(rmdir
, const char __user
*, pathname
)
3611 return do_rmdir(AT_FDCWD
, pathname
);
3615 * vfs_unlink - unlink a filesystem object
3616 * @dir: parent directory
3618 * @delegated_inode: returns victim inode, if the inode is delegated.
3620 * The caller must hold dir->i_mutex.
3622 * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and
3623 * return a reference to the inode in delegated_inode. The caller
3624 * should then break the delegation on that inode and retry. Because
3625 * breaking a delegation may take a long time, the caller should drop
3626 * dir->i_mutex before doing so.
3628 * Alternatively, a caller may pass NULL for delegated_inode. This may
3629 * be appropriate for callers that expect the underlying filesystem not
3630 * to be NFS exported.
3632 int vfs_unlink(struct inode
*dir
, struct dentry
*dentry
, struct inode
**delegated_inode
)
3634 struct inode
*target
= dentry
->d_inode
;
3635 int error
= may_delete(dir
, dentry
, 0);
3640 if (!dir
->i_op
->unlink
)
3643 mutex_lock(&target
->i_mutex
);
3644 if (d_mountpoint(dentry
))
3647 error
= security_inode_unlink(dir
, dentry
);
3649 error
= try_break_deleg(target
, delegated_inode
);
3652 error
= dir
->i_op
->unlink(dir
, dentry
);
3658 mutex_unlock(&target
->i_mutex
);
3660 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
3661 if (!error
&& !(dentry
->d_flags
& DCACHE_NFSFS_RENAMED
)) {
3662 fsnotify_link_count(target
);
3670 * Make sure that the actual truncation of the file will occur outside its
3671 * directory's i_mutex. Truncate can take a long time if there is a lot of
3672 * writeout happening, and we don't want to prevent access to the directory
3673 * while waiting on the I/O.
3675 static long do_unlinkat(int dfd
, const char __user
*pathname
)
3678 struct filename
*name
;
3679 struct dentry
*dentry
;
3680 struct nameidata nd
;
3681 struct inode
*inode
= NULL
;
3682 struct inode
*delegated_inode
= NULL
;
3683 unsigned int lookup_flags
= 0;
3685 name
= user_path_parent(dfd
, pathname
, &nd
, lookup_flags
);
3687 return PTR_ERR(name
);
3690 if (nd
.last_type
!= LAST_NORM
)
3693 nd
.flags
&= ~LOOKUP_PARENT
;
3694 error
= mnt_want_write(nd
.path
.mnt
);
3698 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
3699 dentry
= lookup_hash(&nd
);
3700 error
= PTR_ERR(dentry
);
3701 if (!IS_ERR(dentry
)) {
3702 /* Why not before? Because we want correct error value */
3703 if (nd
.last
.name
[nd
.last
.len
])
3705 inode
= dentry
->d_inode
;
3706 if (d_is_negative(dentry
))
3709 error
= security_path_unlink(&nd
.path
, dentry
);
3712 error
= vfs_unlink(nd
.path
.dentry
->d_inode
, dentry
, &delegated_inode
);
3716 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
3718 iput(inode
); /* truncate the inode here */
3720 if (delegated_inode
) {
3721 error
= break_deleg_wait(&delegated_inode
);
3725 mnt_drop_write(nd
.path
.mnt
);
3729 if (retry_estale(error
, lookup_flags
)) {
3730 lookup_flags
|= LOOKUP_REVAL
;
3737 if (d_is_negative(dentry
))
3739 else if (d_is_directory(dentry
) || d_is_autodir(dentry
))
3746 SYSCALL_DEFINE3(unlinkat
, int, dfd
, const char __user
*, pathname
, int, flag
)
3748 if ((flag
& ~AT_REMOVEDIR
) != 0)
3751 if (flag
& AT_REMOVEDIR
)
3752 return do_rmdir(dfd
, pathname
);
3754 return do_unlinkat(dfd
, pathname
);
3757 SYSCALL_DEFINE1(unlink
, const char __user
*, pathname
)
3759 return do_unlinkat(AT_FDCWD
, pathname
);
3762 int vfs_symlink(struct inode
*dir
, struct dentry
*dentry
, const char *oldname
)
3764 int error
= may_create(dir
, dentry
);
3769 if (!dir
->i_op
->symlink
)
3772 error
= security_inode_symlink(dir
, dentry
, oldname
);
3776 error
= dir
->i_op
->symlink(dir
, dentry
, oldname
);
3778 fsnotify_create(dir
, dentry
);
3782 SYSCALL_DEFINE3(symlinkat
, const char __user
*, oldname
,
3783 int, newdfd
, const char __user
*, newname
)
3786 struct filename
*from
;
3787 struct dentry
*dentry
;
3789 unsigned int lookup_flags
= 0;
3791 from
= getname(oldname
);
3793 return PTR_ERR(from
);
3795 dentry
= user_path_create(newdfd
, newname
, &path
, lookup_flags
);
3796 error
= PTR_ERR(dentry
);
3800 error
= security_path_symlink(&path
, dentry
, from
->name
);
3802 error
= vfs_symlink(path
.dentry
->d_inode
, dentry
, from
->name
);
3803 done_path_create(&path
, dentry
);
3804 if (retry_estale(error
, lookup_flags
)) {
3805 lookup_flags
|= LOOKUP_REVAL
;
3813 SYSCALL_DEFINE2(symlink
, const char __user
*, oldname
, const char __user
*, newname
)
3815 return sys_symlinkat(oldname
, AT_FDCWD
, newname
);
3819 * vfs_link - create a new link
3820 * @old_dentry: object to be linked
3822 * @new_dentry: where to create the new link
3823 * @delegated_inode: returns inode needing a delegation break
3825 * The caller must hold dir->i_mutex
3827 * If vfs_link discovers a delegation on the to-be-linked file in need
3828 * of breaking, it will return -EWOULDBLOCK and return a reference to the
3829 * inode in delegated_inode. The caller should then break the delegation
3830 * and retry. Because breaking a delegation may take a long time, the
3831 * caller should drop the i_mutex before doing so.
3833 * Alternatively, a caller may pass NULL for delegated_inode. This may
3834 * be appropriate for callers that expect the underlying filesystem not
3835 * to be NFS exported.
3837 int vfs_link(struct dentry
*old_dentry
, struct inode
*dir
, struct dentry
*new_dentry
, struct inode
**delegated_inode
)
3839 struct inode
*inode
= old_dentry
->d_inode
;
3840 unsigned max_links
= dir
->i_sb
->s_max_links
;
3846 error
= may_create(dir
, new_dentry
);
3850 if (dir
->i_sb
!= inode
->i_sb
)
3854 * A link to an append-only or immutable file cannot be created.
3856 if (IS_APPEND(inode
) || IS_IMMUTABLE(inode
))
3858 if (!dir
->i_op
->link
)
3860 if (S_ISDIR(inode
->i_mode
))
3863 error
= security_inode_link(old_dentry
, dir
, new_dentry
);
3867 mutex_lock(&inode
->i_mutex
);
3868 /* Make sure we don't allow creating hardlink to an unlinked file */
3869 if (inode
->i_nlink
== 0 && !(inode
->i_state
& I_LINKABLE
))
3871 else if (max_links
&& inode
->i_nlink
>= max_links
)
3874 error
= try_break_deleg(inode
, delegated_inode
);
3876 error
= dir
->i_op
->link(old_dentry
, dir
, new_dentry
);
3879 if (!error
&& (inode
->i_state
& I_LINKABLE
)) {
3880 spin_lock(&inode
->i_lock
);
3881 inode
->i_state
&= ~I_LINKABLE
;
3882 spin_unlock(&inode
->i_lock
);
3884 mutex_unlock(&inode
->i_mutex
);
3886 fsnotify_link(dir
, inode
, new_dentry
);
3891 * Hardlinks are often used in delicate situations. We avoid
3892 * security-related surprises by not following symlinks on the
3895 * We don't follow them on the oldname either to be compatible
3896 * with linux 2.0, and to avoid hard-linking to directories
3897 * and other special files. --ADM
3899 SYSCALL_DEFINE5(linkat
, int, olddfd
, const char __user
*, oldname
,
3900 int, newdfd
, const char __user
*, newname
, int, flags
)
3902 struct dentry
*new_dentry
;
3903 struct path old_path
, new_path
;
3904 struct inode
*delegated_inode
= NULL
;
3908 if ((flags
& ~(AT_SYMLINK_FOLLOW
| AT_EMPTY_PATH
)) != 0)
3911 * To use null names we require CAP_DAC_READ_SEARCH
3912 * This ensures that not everyone will be able to create
3913 * handlink using the passed filedescriptor.
3915 if (flags
& AT_EMPTY_PATH
) {
3916 if (!capable(CAP_DAC_READ_SEARCH
))
3921 if (flags
& AT_SYMLINK_FOLLOW
)
3922 how
|= LOOKUP_FOLLOW
;
3924 error
= user_path_at(olddfd
, oldname
, how
, &old_path
);
3928 new_dentry
= user_path_create(newdfd
, newname
, &new_path
,
3929 (how
& LOOKUP_REVAL
));
3930 error
= PTR_ERR(new_dentry
);
3931 if (IS_ERR(new_dentry
))
3935 if (old_path
.mnt
!= new_path
.mnt
)
3937 error
= may_linkat(&old_path
);
3938 if (unlikely(error
))
3940 error
= security_path_link(old_path
.dentry
, &new_path
, new_dentry
);
3943 error
= vfs_link(old_path
.dentry
, new_path
.dentry
->d_inode
, new_dentry
, &delegated_inode
);
3945 done_path_create(&new_path
, new_dentry
);
3946 if (delegated_inode
) {
3947 error
= break_deleg_wait(&delegated_inode
);
3951 if (retry_estale(error
, how
)) {
3952 how
|= LOOKUP_REVAL
;
3956 path_put(&old_path
);
3961 SYSCALL_DEFINE2(link
, const char __user
*, oldname
, const char __user
*, newname
)
3963 return sys_linkat(AT_FDCWD
, oldname
, AT_FDCWD
, newname
, 0);
3967 * The worst of all namespace operations - renaming directory. "Perverted"
3968 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
3970 * a) we can get into loop creation. Check is done in is_subdir().
3971 * b) race potential - two innocent renames can create a loop together.
3972 * That's where 4.4 screws up. Current fix: serialization on
3973 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
3975 * c) we have to lock _four_ objects - parents and victim (if it exists),
3976 * and source (if it is not a directory).
3977 * And that - after we got ->i_mutex on parents (until then we don't know
3978 * whether the target exists). Solution: try to be smart with locking
3979 * order for inodes. We rely on the fact that tree topology may change
3980 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
3981 * move will be locked. Thus we can rank directories by the tree
3982 * (ancestors first) and rank all non-directories after them.
3983 * That works since everybody except rename does "lock parent, lookup,
3984 * lock child" and rename is under ->s_vfs_rename_mutex.
3985 * HOWEVER, it relies on the assumption that any object with ->lookup()
3986 * has no more than 1 dentry. If "hybrid" objects will ever appear,
3987 * we'd better make sure that there's no link(2) for them.
3988 * d) conversion from fhandle to dentry may come in the wrong moment - when
3989 * we are removing the target. Solution: we will have to grab ->i_mutex
3990 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
3991 * ->i_mutex on parents, which works but leads to some truly excessive
3994 static int vfs_rename_dir(struct inode
*old_dir
, struct dentry
*old_dentry
,
3995 struct inode
*new_dir
, struct dentry
*new_dentry
)
3998 struct inode
*target
= new_dentry
->d_inode
;
3999 unsigned max_links
= new_dir
->i_sb
->s_max_links
;
4002 * If we are going to change the parent - check write permissions,
4003 * we'll need to flip '..'.
4005 if (new_dir
!= old_dir
) {
4006 error
= inode_permission(old_dentry
->d_inode
, MAY_WRITE
);
4011 error
= security_inode_rename(old_dir
, old_dentry
, new_dir
, new_dentry
);
4017 mutex_lock(&target
->i_mutex
);
4020 if (d_mountpoint(old_dentry
) || d_mountpoint(new_dentry
))
4024 if (max_links
&& !target
&& new_dir
!= old_dir
&&
4025 new_dir
->i_nlink
>= max_links
)
4029 shrink_dcache_parent(new_dentry
);
4030 error
= old_dir
->i_op
->rename(old_dir
, old_dentry
, new_dir
, new_dentry
);
4035 target
->i_flags
|= S_DEAD
;
4036 dont_mount(new_dentry
);
4040 mutex_unlock(&target
->i_mutex
);
4043 if (!(old_dir
->i_sb
->s_type
->fs_flags
& FS_RENAME_DOES_D_MOVE
))
4044 d_move(old_dentry
,new_dentry
);
4048 static int vfs_rename_other(struct inode
*old_dir
, struct dentry
*old_dentry
,
4049 struct inode
*new_dir
, struct dentry
*new_dentry
,
4050 struct inode
**delegated_inode
)
4052 struct inode
*target
= new_dentry
->d_inode
;
4053 struct inode
*source
= old_dentry
->d_inode
;
4056 error
= security_inode_rename(old_dir
, old_dentry
, new_dir
, new_dentry
);
4061 lock_two_nondirectories(source
, target
);
4064 if (d_mountpoint(old_dentry
)||d_mountpoint(new_dentry
))
4067 error
= try_break_deleg(source
, delegated_inode
);
4071 error
= try_break_deleg(target
, delegated_inode
);
4075 error
= old_dir
->i_op
->rename(old_dir
, old_dentry
, new_dir
, new_dentry
);
4080 dont_mount(new_dentry
);
4081 if (!(old_dir
->i_sb
->s_type
->fs_flags
& FS_RENAME_DOES_D_MOVE
))
4082 d_move(old_dentry
, new_dentry
);
4084 unlock_two_nondirectories(source
, target
);
4090 * vfs_rename - rename a filesystem object
4091 * @old_dir: parent of source
4092 * @old_dentry: source
4093 * @new_dir: parent of destination
4094 * @new_dentry: destination
4095 * @delegated_inode: returns an inode needing a delegation break
4097 * The caller must hold multiple mutexes--see lock_rename()).
4099 * If vfs_rename discovers a delegation in need of breaking at either
4100 * the source or destination, it will return -EWOULDBLOCK and return a
4101 * reference to the inode in delegated_inode. The caller should then
4102 * break the delegation and retry. Because breaking a delegation may
4103 * take a long time, the caller should drop all locks before doing
4106 * Alternatively, a caller may pass NULL for delegated_inode. This may
4107 * be appropriate for callers that expect the underlying filesystem not
4108 * to be NFS exported.
4110 int vfs_rename(struct inode
*old_dir
, struct dentry
*old_dentry
,
4111 struct inode
*new_dir
, struct dentry
*new_dentry
,
4112 struct inode
**delegated_inode
)
4115 int is_dir
= d_is_directory(old_dentry
) || d_is_autodir(old_dentry
);
4116 const unsigned char *old_name
;
4118 if (old_dentry
->d_inode
== new_dentry
->d_inode
)
4121 error
= may_delete(old_dir
, old_dentry
, is_dir
);
4125 if (!new_dentry
->d_inode
)
4126 error
= may_create(new_dir
, new_dentry
);
4128 error
= may_delete(new_dir
, new_dentry
, is_dir
);
4132 if (!old_dir
->i_op
->rename
)
4135 old_name
= fsnotify_oldname_init(old_dentry
->d_name
.name
);
4138 error
= vfs_rename_dir(old_dir
,old_dentry
,new_dir
,new_dentry
);
4140 error
= vfs_rename_other(old_dir
,old_dentry
,new_dir
,new_dentry
,delegated_inode
);
4142 fsnotify_move(old_dir
, new_dir
, old_name
, is_dir
,
4143 new_dentry
->d_inode
, old_dentry
);
4144 fsnotify_oldname_free(old_name
);
4149 SYSCALL_DEFINE4(renameat
, int, olddfd
, const char __user
*, oldname
,
4150 int, newdfd
, const char __user
*, newname
)
4152 struct dentry
*old_dir
, *new_dir
;
4153 struct dentry
*old_dentry
, *new_dentry
;
4154 struct dentry
*trap
;
4155 struct nameidata oldnd
, newnd
;
4156 struct inode
*delegated_inode
= NULL
;
4157 struct filename
*from
;
4158 struct filename
*to
;
4159 unsigned int lookup_flags
= 0;
4160 bool should_retry
= false;
4163 from
= user_path_parent(olddfd
, oldname
, &oldnd
, lookup_flags
);
4165 error
= PTR_ERR(from
);
4169 to
= user_path_parent(newdfd
, newname
, &newnd
, lookup_flags
);
4171 error
= PTR_ERR(to
);
4176 if (oldnd
.path
.mnt
!= newnd
.path
.mnt
)
4179 old_dir
= oldnd
.path
.dentry
;
4181 if (oldnd
.last_type
!= LAST_NORM
)
4184 new_dir
= newnd
.path
.dentry
;
4185 if (newnd
.last_type
!= LAST_NORM
)
4188 error
= mnt_want_write(oldnd
.path
.mnt
);
4192 oldnd
.flags
&= ~LOOKUP_PARENT
;
4193 newnd
.flags
&= ~LOOKUP_PARENT
;
4194 newnd
.flags
|= LOOKUP_RENAME_TARGET
;
4197 trap
= lock_rename(new_dir
, old_dir
);
4199 old_dentry
= lookup_hash(&oldnd
);
4200 error
= PTR_ERR(old_dentry
);
4201 if (IS_ERR(old_dentry
))
4203 /* source must exist */
4205 if (d_is_negative(old_dentry
))
4207 /* unless the source is a directory trailing slashes give -ENOTDIR */
4208 if (!d_is_directory(old_dentry
) && !d_is_autodir(old_dentry
)) {
4210 if (oldnd
.last
.name
[oldnd
.last
.len
])
4212 if (newnd
.last
.name
[newnd
.last
.len
])
4215 /* source should not be ancestor of target */
4217 if (old_dentry
== trap
)
4219 new_dentry
= lookup_hash(&newnd
);
4220 error
= PTR_ERR(new_dentry
);
4221 if (IS_ERR(new_dentry
))
4223 /* target should not be an ancestor of source */
4225 if (new_dentry
== trap
)
4228 error
= security_path_rename(&oldnd
.path
, old_dentry
,
4229 &newnd
.path
, new_dentry
);
4232 error
= vfs_rename(old_dir
->d_inode
, old_dentry
,
4233 new_dir
->d_inode
, new_dentry
,
4240 unlock_rename(new_dir
, old_dir
);
4241 if (delegated_inode
) {
4242 error
= break_deleg_wait(&delegated_inode
);
4246 mnt_drop_write(oldnd
.path
.mnt
);
4248 if (retry_estale(error
, lookup_flags
))
4249 should_retry
= true;
4250 path_put(&newnd
.path
);
4253 path_put(&oldnd
.path
);
4256 should_retry
= false;
4257 lookup_flags
|= LOOKUP_REVAL
;
4264 SYSCALL_DEFINE2(rename
, const char __user
*, oldname
, const char __user
*, newname
)
4266 return sys_renameat(AT_FDCWD
, oldname
, AT_FDCWD
, newname
);
4269 int vfs_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
, const char *link
)
4273 len
= PTR_ERR(link
);
4278 if (len
> (unsigned) buflen
)
4280 if (copy_to_user(buffer
, link
, len
))
4287 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
4288 * have ->follow_link() touching nd only in nd_set_link(). Using (or not
4289 * using) it for any given inode is up to filesystem.
4291 int generic_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
)
4293 struct nameidata nd
;
4298 cookie
= dentry
->d_inode
->i_op
->follow_link(dentry
, &nd
);
4300 return PTR_ERR(cookie
);
4302 res
= vfs_readlink(dentry
, buffer
, buflen
, nd_get_link(&nd
));
4303 if (dentry
->d_inode
->i_op
->put_link
)
4304 dentry
->d_inode
->i_op
->put_link(dentry
, &nd
, cookie
);
4308 /* get the link contents into pagecache */
4309 static char *page_getlink(struct dentry
* dentry
, struct page
**ppage
)
4313 struct address_space
*mapping
= dentry
->d_inode
->i_mapping
;
4314 page
= read_mapping_page(mapping
, 0, NULL
);
4319 nd_terminate_link(kaddr
, dentry
->d_inode
->i_size
, PAGE_SIZE
- 1);
4323 int page_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
)
4325 struct page
*page
= NULL
;
4326 char *s
= page_getlink(dentry
, &page
);
4327 int res
= vfs_readlink(dentry
,buffer
,buflen
,s
);
4330 page_cache_release(page
);
4335 void *page_follow_link_light(struct dentry
*dentry
, struct nameidata
*nd
)
4337 struct page
*page
= NULL
;
4338 nd_set_link(nd
, page_getlink(dentry
, &page
));
4342 void page_put_link(struct dentry
*dentry
, struct nameidata
*nd
, void *cookie
)
4344 struct page
*page
= cookie
;
4348 page_cache_release(page
);
4353 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
4355 int __page_symlink(struct inode
*inode
, const char *symname
, int len
, int nofs
)
4357 struct address_space
*mapping
= inode
->i_mapping
;
4362 unsigned int flags
= AOP_FLAG_UNINTERRUPTIBLE
;
4364 flags
|= AOP_FLAG_NOFS
;
4367 err
= pagecache_write_begin(NULL
, mapping
, 0, len
-1,
4368 flags
, &page
, &fsdata
);
4372 kaddr
= kmap_atomic(page
);
4373 memcpy(kaddr
, symname
, len
-1);
4374 kunmap_atomic(kaddr
);
4376 err
= pagecache_write_end(NULL
, mapping
, 0, len
-1, len
-1,
4383 mark_inode_dirty(inode
);
4389 int page_symlink(struct inode
*inode
, const char *symname
, int len
)
4391 return __page_symlink(inode
, symname
, len
,
4392 !(mapping_gfp_mask(inode
->i_mapping
) & __GFP_FS
));
4395 const struct inode_operations page_symlink_inode_operations
= {
4396 .readlink
= generic_readlink
,
4397 .follow_link
= page_follow_link_light
,
4398 .put_link
= page_put_link
,
4401 EXPORT_SYMBOL(user_path_at
);
4402 EXPORT_SYMBOL(follow_down_one
);
4403 EXPORT_SYMBOL(follow_down
);
4404 EXPORT_SYMBOL(follow_up
);
4405 EXPORT_SYMBOL(get_write_access
); /* nfsd */
4406 EXPORT_SYMBOL(lock_rename
);
4407 EXPORT_SYMBOL(lookup_one_len
);
4408 EXPORT_SYMBOL(page_follow_link_light
);
4409 EXPORT_SYMBOL(page_put_link
);
4410 EXPORT_SYMBOL(page_readlink
);
4411 EXPORT_SYMBOL(__page_symlink
);
4412 EXPORT_SYMBOL(page_symlink
);
4413 EXPORT_SYMBOL(page_symlink_inode_operations
);
4414 EXPORT_SYMBOL(kern_path
);
4415 EXPORT_SYMBOL(vfs_path_lookup
);
4416 EXPORT_SYMBOL(inode_permission
);
4417 EXPORT_SYMBOL(unlock_rename
);
4418 EXPORT_SYMBOL(vfs_create
);
4419 EXPORT_SYMBOL(vfs_link
);
4420 EXPORT_SYMBOL(vfs_mkdir
);
4421 EXPORT_SYMBOL(vfs_mknod
);
4422 EXPORT_SYMBOL(generic_permission
);
4423 EXPORT_SYMBOL(vfs_readlink
);
4424 EXPORT_SYMBOL(vfs_rename
);
4425 EXPORT_SYMBOL(vfs_rmdir
);
4426 EXPORT_SYMBOL(vfs_symlink
);
4427 EXPORT_SYMBOL(vfs_unlink
);
4428 EXPORT_SYMBOL(dentry_unhash
);
4429 EXPORT_SYMBOL(generic_readlink
);