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.
485 static inline void lock_rcu_walk(void)
487 br_read_lock(&vfsmount_lock
);
491 static inline void unlock_rcu_walk(void)
494 br_read_unlock(&vfsmount_lock
);
498 * unlazy_walk - try to switch to ref-walk mode.
499 * @nd: nameidata pathwalk data
500 * @dentry: child of nd->path.dentry or NULL
501 * Returns: 0 on success, -ECHILD on failure
503 * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry
504 * for ref-walk mode. @dentry must be a path found by a do_lookup call on
505 * @nd or NULL. Must be called from rcu-walk context.
507 static int unlazy_walk(struct nameidata
*nd
, struct dentry
*dentry
)
509 struct fs_struct
*fs
= current
->fs
;
510 struct dentry
*parent
= nd
->path
.dentry
;
512 BUG_ON(!(nd
->flags
& LOOKUP_RCU
));
515 * Get a reference to the parent first: we're
516 * going to make "path_put(nd->path)" valid in
517 * non-RCU context for "terminate_walk()".
519 * If this doesn't work, return immediately with
520 * RCU walking still active (and then we will do
521 * the RCU walk cleanup in terminate_walk()).
523 if (!lockref_get_not_dead(&parent
->d_lockref
))
527 * After the mntget(), we terminate_walk() will do
528 * the right thing for non-RCU mode, and all our
529 * subsequent exit cases should unlock_rcu_walk()
532 mntget(nd
->path
.mnt
);
533 nd
->flags
&= ~LOOKUP_RCU
;
536 * For a negative lookup, the lookup sequence point is the parents
537 * sequence point, and it only needs to revalidate the parent dentry.
539 * For a positive lookup, we need to move both the parent and the
540 * dentry from the RCU domain to be properly refcounted. And the
541 * sequence number in the dentry validates *both* dentry counters,
542 * since we checked the sequence number of the parent after we got
543 * the child sequence number. So we know the parent must still
544 * be valid if the child sequence number is still valid.
547 if (read_seqcount_retry(&parent
->d_seq
, nd
->seq
))
549 BUG_ON(nd
->inode
!= parent
->d_inode
);
551 if (!lockref_get_not_dead(&dentry
->d_lockref
))
553 if (read_seqcount_retry(&dentry
->d_seq
, nd
->seq
))
558 * Sequence counts matched. Now make sure that the root is
559 * still valid and get it if required.
561 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
)) {
562 spin_lock(&fs
->lock
);
563 if (nd
->root
.mnt
!= fs
->root
.mnt
|| nd
->root
.dentry
!= fs
->root
.dentry
)
564 goto unlock_and_drop_dentry
;
566 spin_unlock(&fs
->lock
);
572 unlock_and_drop_dentry
:
573 spin_unlock(&fs
->lock
);
583 static inline int d_revalidate(struct dentry
*dentry
, unsigned int flags
)
585 return dentry
->d_op
->d_revalidate(dentry
, flags
);
589 * complete_walk - successful completion of path walk
590 * @nd: pointer nameidata
592 * If we had been in RCU mode, drop out of it and legitimize nd->path.
593 * Revalidate the final result, unless we'd already done that during
594 * the path walk or the filesystem doesn't ask for it. Return 0 on
595 * success, -error on failure. In case of failure caller does not
596 * need to drop nd->path.
598 static int complete_walk(struct nameidata
*nd
)
600 struct dentry
*dentry
= nd
->path
.dentry
;
603 if (nd
->flags
& LOOKUP_RCU
) {
604 nd
->flags
&= ~LOOKUP_RCU
;
605 if (!(nd
->flags
& LOOKUP_ROOT
))
608 if (unlikely(!lockref_get_not_dead(&dentry
->d_lockref
))) {
612 if (read_seqcount_retry(&dentry
->d_seq
, nd
->seq
)) {
617 mntget(nd
->path
.mnt
);
621 if (likely(!(nd
->flags
& LOOKUP_JUMPED
)))
624 if (likely(!(dentry
->d_flags
& DCACHE_OP_WEAK_REVALIDATE
)))
627 status
= dentry
->d_op
->d_weak_revalidate(dentry
, nd
->flags
);
638 static __always_inline
void set_root(struct nameidata
*nd
)
641 get_fs_root(current
->fs
, &nd
->root
);
644 static int link_path_walk(const char *, struct nameidata
*);
646 static __always_inline
void set_root_rcu(struct nameidata
*nd
)
649 struct fs_struct
*fs
= current
->fs
;
653 seq
= read_seqcount_begin(&fs
->seq
);
655 nd
->seq
= __read_seqcount_begin(&nd
->root
.dentry
->d_seq
);
656 } while (read_seqcount_retry(&fs
->seq
, seq
));
660 static __always_inline
int __vfs_follow_link(struct nameidata
*nd
, const char *link
)
672 nd
->flags
|= LOOKUP_JUMPED
;
674 nd
->inode
= nd
->path
.dentry
->d_inode
;
676 ret
= link_path_walk(link
, nd
);
680 return PTR_ERR(link
);
683 static void path_put_conditional(struct path
*path
, struct nameidata
*nd
)
686 if (path
->mnt
!= nd
->path
.mnt
)
690 static inline void path_to_nameidata(const struct path
*path
,
691 struct nameidata
*nd
)
693 if (!(nd
->flags
& LOOKUP_RCU
)) {
694 dput(nd
->path
.dentry
);
695 if (nd
->path
.mnt
!= path
->mnt
)
696 mntput(nd
->path
.mnt
);
698 nd
->path
.mnt
= path
->mnt
;
699 nd
->path
.dentry
= path
->dentry
;
703 * Helper to directly jump to a known parsed path from ->follow_link,
704 * caller must have taken a reference to path beforehand.
706 void nd_jump_link(struct nameidata
*nd
, struct path
*path
)
711 nd
->inode
= nd
->path
.dentry
->d_inode
;
712 nd
->flags
|= LOOKUP_JUMPED
;
715 static inline void put_link(struct nameidata
*nd
, struct path
*link
, void *cookie
)
717 struct inode
*inode
= link
->dentry
->d_inode
;
718 if (inode
->i_op
->put_link
)
719 inode
->i_op
->put_link(link
->dentry
, nd
, cookie
);
723 int sysctl_protected_symlinks __read_mostly
= 0;
724 int sysctl_protected_hardlinks __read_mostly
= 0;
727 * may_follow_link - Check symlink following for unsafe situations
728 * @link: The path of the symlink
729 * @nd: nameidata pathwalk data
731 * In the case of the sysctl_protected_symlinks sysctl being enabled,
732 * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
733 * in a sticky world-writable directory. This is to protect privileged
734 * processes from failing races against path names that may change out
735 * from under them by way of other users creating malicious symlinks.
736 * It will permit symlinks to be followed only when outside a sticky
737 * world-writable directory, or when the uid of the symlink and follower
738 * match, or when the directory owner matches the symlink's owner.
740 * Returns 0 if following the symlink is allowed, -ve on error.
742 static inline int may_follow_link(struct path
*link
, struct nameidata
*nd
)
744 const struct inode
*inode
;
745 const struct inode
*parent
;
747 if (!sysctl_protected_symlinks
)
750 /* Allowed if owner and follower match. */
751 inode
= link
->dentry
->d_inode
;
752 if (uid_eq(current_cred()->fsuid
, inode
->i_uid
))
755 /* Allowed if parent directory not sticky and world-writable. */
756 parent
= nd
->path
.dentry
->d_inode
;
757 if ((parent
->i_mode
& (S_ISVTX
|S_IWOTH
)) != (S_ISVTX
|S_IWOTH
))
760 /* Allowed if parent directory and link owner match. */
761 if (uid_eq(parent
->i_uid
, inode
->i_uid
))
764 audit_log_link_denied("follow_link", link
);
765 path_put_conditional(link
, nd
);
771 * safe_hardlink_source - Check for safe hardlink conditions
772 * @inode: the source inode to hardlink from
774 * Return false if at least one of the following conditions:
775 * - inode is not a regular file
777 * - inode is setgid and group-exec
778 * - access failure for read and write
780 * Otherwise returns true.
782 static bool safe_hardlink_source(struct inode
*inode
)
784 umode_t mode
= inode
->i_mode
;
786 /* Special files should not get pinned to the filesystem. */
790 /* Setuid files should not get pinned to the filesystem. */
794 /* Executable setgid files should not get pinned to the filesystem. */
795 if ((mode
& (S_ISGID
| S_IXGRP
)) == (S_ISGID
| S_IXGRP
))
798 /* Hardlinking to unreadable or unwritable sources is dangerous. */
799 if (inode_permission(inode
, MAY_READ
| MAY_WRITE
))
806 * may_linkat - Check permissions for creating a hardlink
807 * @link: the source to hardlink from
809 * Block hardlink when all of:
810 * - sysctl_protected_hardlinks enabled
811 * - fsuid does not match inode
812 * - hardlink source is unsafe (see safe_hardlink_source() above)
815 * Returns 0 if successful, -ve on error.
817 static int may_linkat(struct path
*link
)
819 const struct cred
*cred
;
822 if (!sysctl_protected_hardlinks
)
825 cred
= current_cred();
826 inode
= link
->dentry
->d_inode
;
828 /* Source inode owner (or CAP_FOWNER) can hardlink all they like,
829 * otherwise, it must be a safe source.
831 if (uid_eq(cred
->fsuid
, inode
->i_uid
) || safe_hardlink_source(inode
) ||
835 audit_log_link_denied("linkat", link
);
839 static __always_inline
int
840 follow_link(struct path
*link
, struct nameidata
*nd
, void **p
)
842 struct dentry
*dentry
= link
->dentry
;
846 BUG_ON(nd
->flags
& LOOKUP_RCU
);
848 if (link
->mnt
== nd
->path
.mnt
)
852 if (unlikely(current
->total_link_count
>= 40))
853 goto out_put_nd_path
;
856 current
->total_link_count
++;
859 nd_set_link(nd
, NULL
);
861 error
= security_inode_follow_link(link
->dentry
, nd
);
863 goto out_put_nd_path
;
865 nd
->last_type
= LAST_BIND
;
866 *p
= dentry
->d_inode
->i_op
->follow_link(dentry
, nd
);
869 goto out_put_nd_path
;
874 error
= __vfs_follow_link(nd
, s
);
876 put_link(nd
, link
, *p
);
888 static int follow_up_rcu(struct path
*path
)
890 struct mount
*mnt
= real_mount(path
->mnt
);
891 struct mount
*parent
;
892 struct dentry
*mountpoint
;
894 parent
= mnt
->mnt_parent
;
895 if (&parent
->mnt
== path
->mnt
)
897 mountpoint
= mnt
->mnt_mountpoint
;
898 path
->dentry
= mountpoint
;
899 path
->mnt
= &parent
->mnt
;
904 * follow_up - Find the mountpoint of path's vfsmount
906 * Given a path, find the mountpoint of its source file system.
907 * Replace @path with the path of the mountpoint in the parent mount.
910 * Return 1 if we went up a level and 0 if we were already at the
913 int follow_up(struct path
*path
)
915 struct mount
*mnt
= real_mount(path
->mnt
);
916 struct mount
*parent
;
917 struct dentry
*mountpoint
;
919 br_read_lock(&vfsmount_lock
);
920 parent
= mnt
->mnt_parent
;
922 br_read_unlock(&vfsmount_lock
);
925 mntget(&parent
->mnt
);
926 mountpoint
= dget(mnt
->mnt_mountpoint
);
927 br_read_unlock(&vfsmount_lock
);
929 path
->dentry
= mountpoint
;
931 path
->mnt
= &parent
->mnt
;
936 * Perform an automount
937 * - return -EISDIR to tell follow_managed() to stop and return the path we
940 static int follow_automount(struct path
*path
, unsigned flags
,
943 struct vfsmount
*mnt
;
946 if (!path
->dentry
->d_op
|| !path
->dentry
->d_op
->d_automount
)
949 /* We don't want to mount if someone's just doing a stat -
950 * unless they're stat'ing a directory and appended a '/' to
953 * We do, however, want to mount if someone wants to open or
954 * create a file of any type under the mountpoint, wants to
955 * traverse through the mountpoint or wants to open the
956 * mounted directory. Also, autofs may mark negative dentries
957 * as being automount points. These will need the attentions
958 * of the daemon to instantiate them before they can be used.
960 if (!(flags
& (LOOKUP_PARENT
| LOOKUP_DIRECTORY
|
961 LOOKUP_OPEN
| LOOKUP_CREATE
| LOOKUP_AUTOMOUNT
)) &&
962 path
->dentry
->d_inode
)
965 current
->total_link_count
++;
966 if (current
->total_link_count
>= 40)
969 mnt
= path
->dentry
->d_op
->d_automount(path
);
972 * The filesystem is allowed to return -EISDIR here to indicate
973 * it doesn't want to automount. For instance, autofs would do
974 * this so that its userspace daemon can mount on this dentry.
976 * However, we can only permit this if it's a terminal point in
977 * the path being looked up; if it wasn't then the remainder of
978 * the path is inaccessible and we should say so.
980 if (PTR_ERR(mnt
) == -EISDIR
&& (flags
& LOOKUP_PARENT
))
985 if (!mnt
) /* mount collision */
989 /* lock_mount() may release path->mnt on error */
993 err
= finish_automount(mnt
, path
);
997 /* Someone else made a mount here whilst we were busy */
1002 path
->dentry
= dget(mnt
->mnt_root
);
1011 * Handle a dentry that is managed in some way.
1012 * - Flagged for transit management (autofs)
1013 * - Flagged as mountpoint
1014 * - Flagged as automount point
1016 * This may only be called in refwalk mode.
1018 * Serialization is taken care of in namespace.c
1020 static int follow_managed(struct path
*path
, unsigned flags
)
1022 struct vfsmount
*mnt
= path
->mnt
; /* held by caller, must be left alone */
1024 bool need_mntput
= false;
1027 /* Given that we're not holding a lock here, we retain the value in a
1028 * local variable for each dentry as we look at it so that we don't see
1029 * the components of that value change under us */
1030 while (managed
= ACCESS_ONCE(path
->dentry
->d_flags
),
1031 managed
&= DCACHE_MANAGED_DENTRY
,
1032 unlikely(managed
!= 0)) {
1033 /* Allow the filesystem to manage the transit without i_mutex
1035 if (managed
& DCACHE_MANAGE_TRANSIT
) {
1036 BUG_ON(!path
->dentry
->d_op
);
1037 BUG_ON(!path
->dentry
->d_op
->d_manage
);
1038 ret
= path
->dentry
->d_op
->d_manage(path
->dentry
, false);
1043 /* Transit to a mounted filesystem. */
1044 if (managed
& DCACHE_MOUNTED
) {
1045 struct vfsmount
*mounted
= lookup_mnt(path
);
1050 path
->mnt
= mounted
;
1051 path
->dentry
= dget(mounted
->mnt_root
);
1056 /* Something is mounted on this dentry in another
1057 * namespace and/or whatever was mounted there in this
1058 * namespace got unmounted before we managed to get the
1062 /* Handle an automount point */
1063 if (managed
& DCACHE_NEED_AUTOMOUNT
) {
1064 ret
= follow_automount(path
, flags
, &need_mntput
);
1070 /* We didn't change the current path point */
1074 if (need_mntput
&& path
->mnt
== mnt
)
1078 return ret
< 0 ? ret
: need_mntput
;
1081 int follow_down_one(struct path
*path
)
1083 struct vfsmount
*mounted
;
1085 mounted
= lookup_mnt(path
);
1089 path
->mnt
= mounted
;
1090 path
->dentry
= dget(mounted
->mnt_root
);
1096 static inline bool managed_dentry_might_block(struct dentry
*dentry
)
1098 return (dentry
->d_flags
& DCACHE_MANAGE_TRANSIT
&&
1099 dentry
->d_op
->d_manage(dentry
, true) < 0);
1103 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
1104 * we meet a managed dentry that would need blocking.
1106 static bool __follow_mount_rcu(struct nameidata
*nd
, struct path
*path
,
1107 struct inode
**inode
)
1110 struct mount
*mounted
;
1112 * Don't forget we might have a non-mountpoint managed dentry
1113 * that wants to block transit.
1115 if (unlikely(managed_dentry_might_block(path
->dentry
)))
1118 if (!d_mountpoint(path
->dentry
))
1121 mounted
= __lookup_mnt(path
->mnt
, path
->dentry
, 1);
1124 path
->mnt
= &mounted
->mnt
;
1125 path
->dentry
= mounted
->mnt
.mnt_root
;
1126 nd
->flags
|= LOOKUP_JUMPED
;
1127 nd
->seq
= read_seqcount_begin(&path
->dentry
->d_seq
);
1129 * Update the inode too. We don't need to re-check the
1130 * dentry sequence number here after this d_inode read,
1131 * because a mount-point is always pinned.
1133 *inode
= path
->dentry
->d_inode
;
1138 static void follow_mount_rcu(struct nameidata
*nd
)
1140 while (d_mountpoint(nd
->path
.dentry
)) {
1141 struct mount
*mounted
;
1142 mounted
= __lookup_mnt(nd
->path
.mnt
, nd
->path
.dentry
, 1);
1145 nd
->path
.mnt
= &mounted
->mnt
;
1146 nd
->path
.dentry
= mounted
->mnt
.mnt_root
;
1147 nd
->seq
= read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1151 static int follow_dotdot_rcu(struct nameidata
*nd
)
1156 if (nd
->path
.dentry
== nd
->root
.dentry
&&
1157 nd
->path
.mnt
== nd
->root
.mnt
) {
1160 if (nd
->path
.dentry
!= nd
->path
.mnt
->mnt_root
) {
1161 struct dentry
*old
= nd
->path
.dentry
;
1162 struct dentry
*parent
= old
->d_parent
;
1165 seq
= read_seqcount_begin(&parent
->d_seq
);
1166 if (read_seqcount_retry(&old
->d_seq
, nd
->seq
))
1168 nd
->path
.dentry
= parent
;
1172 if (!follow_up_rcu(&nd
->path
))
1174 nd
->seq
= read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1176 follow_mount_rcu(nd
);
1177 nd
->inode
= nd
->path
.dentry
->d_inode
;
1181 nd
->flags
&= ~LOOKUP_RCU
;
1182 if (!(nd
->flags
& LOOKUP_ROOT
))
1183 nd
->root
.mnt
= NULL
;
1189 * Follow down to the covering mount currently visible to userspace. At each
1190 * point, the filesystem owning that dentry may be queried as to whether the
1191 * caller is permitted to proceed or not.
1193 int follow_down(struct path
*path
)
1198 while (managed
= ACCESS_ONCE(path
->dentry
->d_flags
),
1199 unlikely(managed
& DCACHE_MANAGED_DENTRY
)) {
1200 /* Allow the filesystem to manage the transit without i_mutex
1203 * We indicate to the filesystem if someone is trying to mount
1204 * something here. This gives autofs the chance to deny anyone
1205 * other than its daemon the right to mount on its
1208 * The filesystem may sleep at this point.
1210 if (managed
& DCACHE_MANAGE_TRANSIT
) {
1211 BUG_ON(!path
->dentry
->d_op
);
1212 BUG_ON(!path
->dentry
->d_op
->d_manage
);
1213 ret
= path
->dentry
->d_op
->d_manage(
1214 path
->dentry
, false);
1216 return ret
== -EISDIR
? 0 : ret
;
1219 /* Transit to a mounted filesystem. */
1220 if (managed
& DCACHE_MOUNTED
) {
1221 struct vfsmount
*mounted
= lookup_mnt(path
);
1226 path
->mnt
= mounted
;
1227 path
->dentry
= dget(mounted
->mnt_root
);
1231 /* Don't handle automount points here */
1238 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1240 static void follow_mount(struct path
*path
)
1242 while (d_mountpoint(path
->dentry
)) {
1243 struct vfsmount
*mounted
= lookup_mnt(path
);
1248 path
->mnt
= mounted
;
1249 path
->dentry
= dget(mounted
->mnt_root
);
1253 static void follow_dotdot(struct nameidata
*nd
)
1258 struct dentry
*old
= nd
->path
.dentry
;
1260 if (nd
->path
.dentry
== nd
->root
.dentry
&&
1261 nd
->path
.mnt
== nd
->root
.mnt
) {
1264 if (nd
->path
.dentry
!= nd
->path
.mnt
->mnt_root
) {
1265 /* rare case of legitimate dget_parent()... */
1266 nd
->path
.dentry
= dget_parent(nd
->path
.dentry
);
1270 if (!follow_up(&nd
->path
))
1273 follow_mount(&nd
->path
);
1274 nd
->inode
= nd
->path
.dentry
->d_inode
;
1278 * This looks up the name in dcache, possibly revalidates the old dentry and
1279 * allocates a new one if not found or not valid. In the need_lookup argument
1280 * returns whether i_op->lookup is necessary.
1282 * dir->d_inode->i_mutex must be held
1284 static struct dentry
*lookup_dcache(struct qstr
*name
, struct dentry
*dir
,
1285 unsigned int flags
, bool *need_lookup
)
1287 struct dentry
*dentry
;
1290 *need_lookup
= false;
1291 dentry
= d_lookup(dir
, name
);
1293 if (dentry
->d_flags
& DCACHE_OP_REVALIDATE
) {
1294 error
= d_revalidate(dentry
, flags
);
1295 if (unlikely(error
<= 0)) {
1298 return ERR_PTR(error
);
1299 } else if (!d_invalidate(dentry
)) {
1308 dentry
= d_alloc(dir
, name
);
1309 if (unlikely(!dentry
))
1310 return ERR_PTR(-ENOMEM
);
1312 *need_lookup
= true;
1318 * Call i_op->lookup on the dentry. The dentry must be negative but may be
1319 * hashed if it was pouplated with DCACHE_NEED_LOOKUP.
1321 * dir->d_inode->i_mutex must be held
1323 static struct dentry
*lookup_real(struct inode
*dir
, struct dentry
*dentry
,
1328 /* Don't create child dentry for a dead directory. */
1329 if (unlikely(IS_DEADDIR(dir
))) {
1331 return ERR_PTR(-ENOENT
);
1334 old
= dir
->i_op
->lookup(dir
, dentry
, flags
);
1335 if (unlikely(old
)) {
1342 static struct dentry
*__lookup_hash(struct qstr
*name
,
1343 struct dentry
*base
, unsigned int flags
)
1346 struct dentry
*dentry
;
1348 dentry
= lookup_dcache(name
, base
, flags
, &need_lookup
);
1352 return lookup_real(base
->d_inode
, dentry
, flags
);
1356 * It's more convoluted than I'd like it to be, but... it's still fairly
1357 * small and for now I'd prefer to have fast path as straight as possible.
1358 * It _is_ time-critical.
1360 static int lookup_fast(struct nameidata
*nd
,
1361 struct path
*path
, struct inode
**inode
)
1363 struct vfsmount
*mnt
= nd
->path
.mnt
;
1364 struct dentry
*dentry
, *parent
= nd
->path
.dentry
;
1370 * Rename seqlock is not required here because in the off chance
1371 * of a false negative due to a concurrent rename, we're going to
1372 * do the non-racy lookup, below.
1374 if (nd
->flags
& LOOKUP_RCU
) {
1376 dentry
= __d_lookup_rcu(parent
, &nd
->last
, &seq
);
1381 * This sequence count validates that the inode matches
1382 * the dentry name information from lookup.
1384 *inode
= dentry
->d_inode
;
1385 if (read_seqcount_retry(&dentry
->d_seq
, seq
))
1389 * This sequence count validates that the parent had no
1390 * changes while we did the lookup of the dentry above.
1392 * The memory barrier in read_seqcount_begin of child is
1393 * enough, we can use __read_seqcount_retry here.
1395 if (__read_seqcount_retry(&parent
->d_seq
, nd
->seq
))
1399 if (unlikely(dentry
->d_flags
& DCACHE_OP_REVALIDATE
)) {
1400 status
= d_revalidate(dentry
, nd
->flags
);
1401 if (unlikely(status
<= 0)) {
1402 if (status
!= -ECHILD
)
1408 path
->dentry
= dentry
;
1409 if (unlikely(!__follow_mount_rcu(nd
, path
, inode
)))
1411 if (unlikely(path
->dentry
->d_flags
& DCACHE_NEED_AUTOMOUNT
))
1415 if (unlazy_walk(nd
, dentry
))
1418 dentry
= __d_lookup(parent
, &nd
->last
);
1421 if (unlikely(!dentry
))
1424 if (unlikely(dentry
->d_flags
& DCACHE_OP_REVALIDATE
) && need_reval
)
1425 status
= d_revalidate(dentry
, nd
->flags
);
1426 if (unlikely(status
<= 0)) {
1431 if (!d_invalidate(dentry
)) {
1438 path
->dentry
= dentry
;
1439 err
= follow_managed(path
, nd
->flags
);
1440 if (unlikely(err
< 0)) {
1441 path_put_conditional(path
, nd
);
1445 nd
->flags
|= LOOKUP_JUMPED
;
1446 *inode
= path
->dentry
->d_inode
;
1453 /* Fast lookup failed, do it the slow way */
1454 static int lookup_slow(struct nameidata
*nd
, struct path
*path
)
1456 struct dentry
*dentry
, *parent
;
1459 parent
= nd
->path
.dentry
;
1460 BUG_ON(nd
->inode
!= parent
->d_inode
);
1462 mutex_lock(&parent
->d_inode
->i_mutex
);
1463 dentry
= __lookup_hash(&nd
->last
, parent
, nd
->flags
);
1464 mutex_unlock(&parent
->d_inode
->i_mutex
);
1466 return PTR_ERR(dentry
);
1467 path
->mnt
= nd
->path
.mnt
;
1468 path
->dentry
= dentry
;
1469 err
= follow_managed(path
, nd
->flags
);
1470 if (unlikely(err
< 0)) {
1471 path_put_conditional(path
, nd
);
1475 nd
->flags
|= LOOKUP_JUMPED
;
1479 static inline int may_lookup(struct nameidata
*nd
)
1481 if (nd
->flags
& LOOKUP_RCU
) {
1482 int err
= inode_permission(nd
->inode
, MAY_EXEC
|MAY_NOT_BLOCK
);
1485 if (unlazy_walk(nd
, NULL
))
1488 return inode_permission(nd
->inode
, MAY_EXEC
);
1491 static inline int handle_dots(struct nameidata
*nd
, int type
)
1493 if (type
== LAST_DOTDOT
) {
1494 if (nd
->flags
& LOOKUP_RCU
) {
1495 if (follow_dotdot_rcu(nd
))
1503 static void terminate_walk(struct nameidata
*nd
)
1505 if (!(nd
->flags
& LOOKUP_RCU
)) {
1506 path_put(&nd
->path
);
1508 nd
->flags
&= ~LOOKUP_RCU
;
1509 if (!(nd
->flags
& LOOKUP_ROOT
))
1510 nd
->root
.mnt
= NULL
;
1516 * Do we need to follow links? We _really_ want to be able
1517 * to do this check without having to look at inode->i_op,
1518 * so we keep a cache of "no, this doesn't need follow_link"
1519 * for the common case.
1521 static inline int should_follow_link(struct inode
*inode
, int follow
)
1523 if (unlikely(!(inode
->i_opflags
& IOP_NOFOLLOW
))) {
1524 if (likely(inode
->i_op
->follow_link
))
1527 /* This gets set once for the inode lifetime */
1528 spin_lock(&inode
->i_lock
);
1529 inode
->i_opflags
|= IOP_NOFOLLOW
;
1530 spin_unlock(&inode
->i_lock
);
1535 static inline int walk_component(struct nameidata
*nd
, struct path
*path
,
1538 struct inode
*inode
;
1541 * "." and ".." are special - ".." especially so because it has
1542 * to be able to know about the current root directory and
1543 * parent relationships.
1545 if (unlikely(nd
->last_type
!= LAST_NORM
))
1546 return handle_dots(nd
, nd
->last_type
);
1547 err
= lookup_fast(nd
, path
, &inode
);
1548 if (unlikely(err
)) {
1552 err
= lookup_slow(nd
, path
);
1556 inode
= path
->dentry
->d_inode
;
1562 if (should_follow_link(inode
, follow
)) {
1563 if (nd
->flags
& LOOKUP_RCU
) {
1564 if (unlikely(unlazy_walk(nd
, path
->dentry
))) {
1569 BUG_ON(inode
!= path
->dentry
->d_inode
);
1572 path_to_nameidata(path
, nd
);
1577 path_to_nameidata(path
, nd
);
1584 * This limits recursive symlink follows to 8, while
1585 * limiting consecutive symlinks to 40.
1587 * Without that kind of total limit, nasty chains of consecutive
1588 * symlinks can cause almost arbitrarily long lookups.
1590 static inline int nested_symlink(struct path
*path
, struct nameidata
*nd
)
1594 if (unlikely(current
->link_count
>= MAX_NESTED_LINKS
)) {
1595 path_put_conditional(path
, nd
);
1596 path_put(&nd
->path
);
1599 BUG_ON(nd
->depth
>= MAX_NESTED_LINKS
);
1602 current
->link_count
++;
1605 struct path link
= *path
;
1608 res
= follow_link(&link
, nd
, &cookie
);
1611 res
= walk_component(nd
, path
, LOOKUP_FOLLOW
);
1612 put_link(nd
, &link
, cookie
);
1615 current
->link_count
--;
1621 * We really don't want to look at inode->i_op->lookup
1622 * when we don't have to. So we keep a cache bit in
1623 * the inode ->i_opflags field that says "yes, we can
1624 * do lookup on this inode".
1626 static inline int can_lookup(struct inode
*inode
)
1628 if (likely(inode
->i_opflags
& IOP_LOOKUP
))
1630 if (likely(!inode
->i_op
->lookup
))
1633 /* We do this once for the lifetime of the inode */
1634 spin_lock(&inode
->i_lock
);
1635 inode
->i_opflags
|= IOP_LOOKUP
;
1636 spin_unlock(&inode
->i_lock
);
1641 * We can do the critical dentry name comparison and hashing
1642 * operations one word at a time, but we are limited to:
1644 * - Architectures with fast unaligned word accesses. We could
1645 * do a "get_unaligned()" if this helps and is sufficiently
1648 * - Little-endian machines (so that we can generate the mask
1649 * of low bytes efficiently). Again, we *could* do a byte
1650 * swapping load on big-endian architectures if that is not
1651 * expensive enough to make the optimization worthless.
1653 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
1654 * do not trap on the (extremely unlikely) case of a page
1655 * crossing operation.
1657 * - Furthermore, we need an efficient 64-bit compile for the
1658 * 64-bit case in order to generate the "number of bytes in
1659 * the final mask". Again, that could be replaced with a
1660 * efficient population count instruction or similar.
1662 #ifdef CONFIG_DCACHE_WORD_ACCESS
1664 #include <asm/word-at-a-time.h>
1668 static inline unsigned int fold_hash(unsigned long hash
)
1670 hash
+= hash
>> (8*sizeof(int));
1674 #else /* 32-bit case */
1676 #define fold_hash(x) (x)
1680 unsigned int full_name_hash(const unsigned char *name
, unsigned int len
)
1682 unsigned long a
, mask
;
1683 unsigned long hash
= 0;
1686 a
= load_unaligned_zeropad(name
);
1687 if (len
< sizeof(unsigned long))
1691 name
+= sizeof(unsigned long);
1692 len
-= sizeof(unsigned long);
1696 mask
= ~(~0ul << len
*8);
1699 return fold_hash(hash
);
1701 EXPORT_SYMBOL(full_name_hash
);
1704 * Calculate the length and hash of the path component, and
1705 * return the length of the component;
1707 static inline unsigned long hash_name(const char *name
, unsigned int *hashp
)
1709 unsigned long a
, b
, adata
, bdata
, mask
, hash
, len
;
1710 const struct word_at_a_time constants
= WORD_AT_A_TIME_CONSTANTS
;
1713 len
= -sizeof(unsigned long);
1715 hash
= (hash
+ a
) * 9;
1716 len
+= sizeof(unsigned long);
1717 a
= load_unaligned_zeropad(name
+len
);
1718 b
= a
^ REPEAT_BYTE('/');
1719 } while (!(has_zero(a
, &adata
, &constants
) | has_zero(b
, &bdata
, &constants
)));
1721 adata
= prep_zero_mask(a
, adata
, &constants
);
1722 bdata
= prep_zero_mask(b
, bdata
, &constants
);
1724 mask
= create_zero_mask(adata
| bdata
);
1726 hash
+= a
& zero_bytemask(mask
);
1727 *hashp
= fold_hash(hash
);
1729 return len
+ find_zero(mask
);
1734 unsigned int full_name_hash(const unsigned char *name
, unsigned int len
)
1736 unsigned long hash
= init_name_hash();
1738 hash
= partial_name_hash(*name
++, hash
);
1739 return end_name_hash(hash
);
1741 EXPORT_SYMBOL(full_name_hash
);
1744 * We know there's a real path component here of at least
1747 static inline unsigned long hash_name(const char *name
, unsigned int *hashp
)
1749 unsigned long hash
= init_name_hash();
1750 unsigned long len
= 0, c
;
1752 c
= (unsigned char)*name
;
1755 hash
= partial_name_hash(c
, hash
);
1756 c
= (unsigned char)name
[len
];
1757 } while (c
&& c
!= '/');
1758 *hashp
= end_name_hash(hash
);
1766 * This is the basic name resolution function, turning a pathname into
1767 * the final dentry. We expect 'base' to be positive and a directory.
1769 * Returns 0 and nd will have valid dentry and mnt on success.
1770 * Returns error and drops reference to input namei data on failure.
1772 static int link_path_walk(const char *name
, struct nameidata
*nd
)
1782 /* At this point we know we have a real path component. */
1788 err
= may_lookup(nd
);
1792 len
= hash_name(name
, &this.hash
);
1797 if (name
[0] == '.') switch (len
) {
1799 if (name
[1] == '.') {
1801 nd
->flags
|= LOOKUP_JUMPED
;
1807 if (likely(type
== LAST_NORM
)) {
1808 struct dentry
*parent
= nd
->path
.dentry
;
1809 nd
->flags
&= ~LOOKUP_JUMPED
;
1810 if (unlikely(parent
->d_flags
& DCACHE_OP_HASH
)) {
1811 err
= parent
->d_op
->d_hash(parent
, &this);
1818 nd
->last_type
= type
;
1823 * If it wasn't NUL, we know it was '/'. Skip that
1824 * slash, and continue until no more slashes.
1828 } while (unlikely(name
[len
] == '/'));
1834 err
= walk_component(nd
, &next
, LOOKUP_FOLLOW
);
1839 err
= nested_symlink(&next
, nd
);
1843 if (!can_lookup(nd
->inode
)) {
1852 static int path_init(int dfd
, const char *name
, unsigned int flags
,
1853 struct nameidata
*nd
, struct file
**fp
)
1857 nd
->last_type
= LAST_ROOT
; /* if there are only slashes... */
1858 nd
->flags
= flags
| LOOKUP_JUMPED
;
1860 if (flags
& LOOKUP_ROOT
) {
1861 struct inode
*inode
= nd
->root
.dentry
->d_inode
;
1863 if (!can_lookup(inode
))
1865 retval
= inode_permission(inode
, MAY_EXEC
);
1869 nd
->path
= nd
->root
;
1871 if (flags
& LOOKUP_RCU
) {
1873 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1875 path_get(&nd
->path
);
1880 nd
->root
.mnt
= NULL
;
1883 if (flags
& LOOKUP_RCU
) {
1888 path_get(&nd
->root
);
1890 nd
->path
= nd
->root
;
1891 } else if (dfd
== AT_FDCWD
) {
1892 if (flags
& LOOKUP_RCU
) {
1893 struct fs_struct
*fs
= current
->fs
;
1899 seq
= read_seqcount_begin(&fs
->seq
);
1901 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1902 } while (read_seqcount_retry(&fs
->seq
, seq
));
1904 get_fs_pwd(current
->fs
, &nd
->path
);
1907 /* Caller must check execute permissions on the starting path component */
1908 struct fd f
= fdget_raw(dfd
);
1909 struct dentry
*dentry
;
1914 dentry
= f
.file
->f_path
.dentry
;
1917 if (!can_lookup(dentry
->d_inode
)) {
1923 nd
->path
= f
.file
->f_path
;
1924 if (flags
& LOOKUP_RCU
) {
1927 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1930 path_get(&nd
->path
);
1935 nd
->inode
= nd
->path
.dentry
->d_inode
;
1939 static inline int lookup_last(struct nameidata
*nd
, struct path
*path
)
1941 if (nd
->last_type
== LAST_NORM
&& nd
->last
.name
[nd
->last
.len
])
1942 nd
->flags
|= LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
;
1944 nd
->flags
&= ~LOOKUP_PARENT
;
1945 return walk_component(nd
, path
, nd
->flags
& LOOKUP_FOLLOW
);
1948 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
1949 static int path_lookupat(int dfd
, const char *name
,
1950 unsigned int flags
, struct nameidata
*nd
)
1952 struct file
*base
= NULL
;
1957 * Path walking is largely split up into 2 different synchronisation
1958 * schemes, rcu-walk and ref-walk (explained in
1959 * Documentation/filesystems/path-lookup.txt). These share much of the
1960 * path walk code, but some things particularly setup, cleanup, and
1961 * following mounts are sufficiently divergent that functions are
1962 * duplicated. Typically there is a function foo(), and its RCU
1963 * analogue, foo_rcu().
1965 * -ECHILD is the error number of choice (just to avoid clashes) that
1966 * is returned if some aspect of an rcu-walk fails. Such an error must
1967 * be handled by restarting a traditional ref-walk (which will always
1968 * be able to complete).
1970 err
= path_init(dfd
, name
, flags
| LOOKUP_PARENT
, nd
, &base
);
1975 current
->total_link_count
= 0;
1976 err
= link_path_walk(name
, nd
);
1978 if (!err
&& !(flags
& LOOKUP_PARENT
)) {
1979 err
= lookup_last(nd
, &path
);
1982 struct path link
= path
;
1983 err
= may_follow_link(&link
, nd
);
1986 nd
->flags
|= LOOKUP_PARENT
;
1987 err
= follow_link(&link
, nd
, &cookie
);
1990 err
= lookup_last(nd
, &path
);
1991 put_link(nd
, &link
, cookie
);
1996 err
= complete_walk(nd
);
1998 if (!err
&& nd
->flags
& LOOKUP_DIRECTORY
) {
1999 if (!can_lookup(nd
->inode
)) {
2000 path_put(&nd
->path
);
2008 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
)) {
2009 path_put(&nd
->root
);
2010 nd
->root
.mnt
= NULL
;
2015 static int filename_lookup(int dfd
, struct filename
*name
,
2016 unsigned int flags
, struct nameidata
*nd
)
2018 int retval
= path_lookupat(dfd
, name
->name
, flags
| LOOKUP_RCU
, nd
);
2019 if (unlikely(retval
== -ECHILD
))
2020 retval
= path_lookupat(dfd
, name
->name
, flags
, nd
);
2021 if (unlikely(retval
== -ESTALE
))
2022 retval
= path_lookupat(dfd
, name
->name
,
2023 flags
| LOOKUP_REVAL
, nd
);
2025 if (likely(!retval
))
2026 audit_inode(name
, nd
->path
.dentry
, flags
& LOOKUP_PARENT
);
2030 static int do_path_lookup(int dfd
, const char *name
,
2031 unsigned int flags
, struct nameidata
*nd
)
2033 struct filename filename
= { .name
= name
};
2035 return filename_lookup(dfd
, &filename
, flags
, nd
);
2038 /* does lookup, returns the object with parent locked */
2039 struct dentry
*kern_path_locked(const char *name
, struct path
*path
)
2041 struct nameidata nd
;
2043 int err
= do_path_lookup(AT_FDCWD
, name
, LOOKUP_PARENT
, &nd
);
2045 return ERR_PTR(err
);
2046 if (nd
.last_type
!= LAST_NORM
) {
2048 return ERR_PTR(-EINVAL
);
2050 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2051 d
= __lookup_hash(&nd
.last
, nd
.path
.dentry
, 0);
2053 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
2061 int kern_path(const char *name
, unsigned int flags
, struct path
*path
)
2063 struct nameidata nd
;
2064 int res
= do_path_lookup(AT_FDCWD
, name
, flags
, &nd
);
2071 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
2072 * @dentry: pointer to dentry of the base directory
2073 * @mnt: pointer to vfs mount of the base directory
2074 * @name: pointer to file name
2075 * @flags: lookup flags
2076 * @path: pointer to struct path to fill
2078 int vfs_path_lookup(struct dentry
*dentry
, struct vfsmount
*mnt
,
2079 const char *name
, unsigned int flags
,
2082 struct nameidata nd
;
2084 nd
.root
.dentry
= dentry
;
2086 BUG_ON(flags
& LOOKUP_PARENT
);
2087 /* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */
2088 err
= do_path_lookup(AT_FDCWD
, name
, flags
| LOOKUP_ROOT
, &nd
);
2095 * Restricted form of lookup. Doesn't follow links, single-component only,
2096 * needs parent already locked. Doesn't follow mounts.
2099 static struct dentry
*lookup_hash(struct nameidata
*nd
)
2101 return __lookup_hash(&nd
->last
, nd
->path
.dentry
, nd
->flags
);
2105 * lookup_one_len - filesystem helper to lookup single pathname component
2106 * @name: pathname component to lookup
2107 * @base: base directory to lookup from
2108 * @len: maximum length @len should be interpreted to
2110 * Note that this routine is purely a helper for filesystem usage and should
2111 * not be called by generic code. Also note that by using this function the
2112 * nameidata argument is passed to the filesystem methods and a filesystem
2113 * using this helper needs to be prepared for that.
2115 struct dentry
*lookup_one_len(const char *name
, struct dentry
*base
, int len
)
2121 WARN_ON_ONCE(!mutex_is_locked(&base
->d_inode
->i_mutex
));
2125 this.hash
= full_name_hash(name
, len
);
2127 return ERR_PTR(-EACCES
);
2129 if (unlikely(name
[0] == '.')) {
2130 if (len
< 2 || (len
== 2 && name
[1] == '.'))
2131 return ERR_PTR(-EACCES
);
2135 c
= *(const unsigned char *)name
++;
2136 if (c
== '/' || c
== '\0')
2137 return ERR_PTR(-EACCES
);
2140 * See if the low-level filesystem might want
2141 * to use its own hash..
2143 if (base
->d_flags
& DCACHE_OP_HASH
) {
2144 int err
= base
->d_op
->d_hash(base
, &this);
2146 return ERR_PTR(err
);
2149 err
= inode_permission(base
->d_inode
, MAY_EXEC
);
2151 return ERR_PTR(err
);
2153 return __lookup_hash(&this, base
, 0);
2156 int user_path_at_empty(int dfd
, const char __user
*name
, unsigned flags
,
2157 struct path
*path
, int *empty
)
2159 struct nameidata nd
;
2160 struct filename
*tmp
= getname_flags(name
, flags
, empty
);
2161 int err
= PTR_ERR(tmp
);
2164 BUG_ON(flags
& LOOKUP_PARENT
);
2166 err
= filename_lookup(dfd
, tmp
, flags
, &nd
);
2174 int user_path_at(int dfd
, const char __user
*name
, unsigned flags
,
2177 return user_path_at_empty(dfd
, name
, flags
, path
, NULL
);
2181 * NB: most callers don't do anything directly with the reference to the
2182 * to struct filename, but the nd->last pointer points into the name string
2183 * allocated by getname. So we must hold the reference to it until all
2184 * path-walking is complete.
2186 static struct filename
*
2187 user_path_parent(int dfd
, const char __user
*path
, struct nameidata
*nd
,
2190 struct filename
*s
= getname(path
);
2193 /* only LOOKUP_REVAL is allowed in extra flags */
2194 flags
&= LOOKUP_REVAL
;
2199 error
= filename_lookup(dfd
, s
, flags
| LOOKUP_PARENT
, nd
);
2202 return ERR_PTR(error
);
2209 * umount_lookup_last - look up last component for umount
2210 * @nd: pathwalk nameidata - currently pointing at parent directory of "last"
2211 * @path: pointer to container for result
2213 * This is a special lookup_last function just for umount. In this case, we
2214 * need to resolve the path without doing any revalidation.
2216 * The nameidata should be the result of doing a LOOKUP_PARENT pathwalk. Since
2217 * mountpoints are always pinned in the dcache, their ancestors are too. Thus,
2218 * in almost all cases, this lookup will be served out of the dcache. The only
2219 * cases where it won't are if nd->last refers to a symlink or the path is
2220 * bogus and it doesn't exist.
2223 * -error: if there was an error during lookup. This includes -ENOENT if the
2224 * lookup found a negative dentry. The nd->path reference will also be
2227 * 0: if we successfully resolved nd->path and found it to not to be a
2228 * symlink that needs to be followed. "path" will also be populated.
2229 * The nd->path reference will also be put.
2231 * 1: if we successfully resolved nd->last and found it to be a symlink
2232 * that needs to be followed. "path" will be populated with the path
2233 * to the link, and nd->path will *not* be put.
2236 umount_lookup_last(struct nameidata
*nd
, struct path
*path
)
2239 struct dentry
*dentry
;
2240 struct dentry
*dir
= nd
->path
.dentry
;
2242 if (unlikely(nd
->flags
& LOOKUP_RCU
)) {
2248 nd
->flags
&= ~LOOKUP_PARENT
;
2250 if (unlikely(nd
->last_type
!= LAST_NORM
)) {
2251 error
= handle_dots(nd
, nd
->last_type
);
2253 dentry
= dget(nd
->path
.dentry
);
2257 mutex_lock(&dir
->d_inode
->i_mutex
);
2258 dentry
= d_lookup(dir
, &nd
->last
);
2261 * No cached dentry. Mounted dentries are pinned in the cache,
2262 * so that means that this dentry is probably a symlink or the
2263 * path doesn't actually point to a mounted dentry.
2265 dentry
= d_alloc(dir
, &nd
->last
);
2269 dentry
= lookup_real(dir
->d_inode
, dentry
, nd
->flags
);
2271 error
= PTR_ERR(dentry
);
2274 mutex_unlock(&dir
->d_inode
->i_mutex
);
2278 if (!dentry
->d_inode
) {
2282 path
->dentry
= dentry
;
2283 path
->mnt
= mntget(nd
->path
.mnt
);
2284 if (should_follow_link(dentry
->d_inode
,
2285 nd
->flags
& LOOKUP_FOLLOW
))
2295 * path_umountat - look up a path to be umounted
2296 * @dfd: directory file descriptor to start walk from
2297 * @name: full pathname to walk
2298 * @flags: lookup flags
2299 * @nd: pathwalk nameidata
2301 * Look up the given name, but don't attempt to revalidate the last component.
2302 * Returns 0 and "path" will be valid on success; Retuns error otherwise.
2305 path_umountat(int dfd
, const char *name
, struct path
*path
, unsigned int flags
)
2307 struct file
*base
= NULL
;
2308 struct nameidata nd
;
2311 err
= path_init(dfd
, name
, flags
| LOOKUP_PARENT
, &nd
, &base
);
2315 current
->total_link_count
= 0;
2316 err
= link_path_walk(name
, &nd
);
2320 /* If we're in rcuwalk, drop out of it to handle last component */
2321 if (nd
.flags
& LOOKUP_RCU
) {
2322 err
= unlazy_walk(&nd
, NULL
);
2324 terminate_walk(&nd
);
2329 err
= umount_lookup_last(&nd
, path
);
2332 struct path link
= *path
;
2333 err
= may_follow_link(&link
, &nd
);
2336 nd
.flags
|= LOOKUP_PARENT
;
2337 err
= follow_link(&link
, &nd
, &cookie
);
2340 err
= umount_lookup_last(&nd
, path
);
2341 put_link(&nd
, &link
, cookie
);
2347 if (nd
.root
.mnt
&& !(nd
.flags
& LOOKUP_ROOT
))
2354 * user_path_umountat - lookup a path from userland in order to umount it
2355 * @dfd: directory file descriptor
2356 * @name: pathname from userland
2357 * @flags: lookup flags
2358 * @path: pointer to container to hold result
2360 * A umount is a special case for path walking. We're not actually interested
2361 * in the inode in this situation, and ESTALE errors can be a problem. We
2362 * simply want track down the dentry and vfsmount attached at the mountpoint
2363 * and avoid revalidating the last component.
2365 * Returns 0 and populates "path" on success.
2368 user_path_umountat(int dfd
, const char __user
*name
, unsigned int flags
,
2371 struct filename
*s
= getname(name
);
2377 error
= path_umountat(dfd
, s
->name
, path
, flags
| LOOKUP_RCU
);
2378 if (unlikely(error
== -ECHILD
))
2379 error
= path_umountat(dfd
, s
->name
, path
, flags
);
2380 if (unlikely(error
== -ESTALE
))
2381 error
= path_umountat(dfd
, s
->name
, path
, flags
| LOOKUP_REVAL
);
2384 audit_inode(s
, path
->dentry
, 0);
2391 * It's inline, so penalty for filesystems that don't use sticky bit is
2394 static inline int check_sticky(struct inode
*dir
, struct inode
*inode
)
2396 kuid_t fsuid
= current_fsuid();
2398 if (!(dir
->i_mode
& S_ISVTX
))
2400 if (uid_eq(inode
->i_uid
, fsuid
))
2402 if (uid_eq(dir
->i_uid
, fsuid
))
2404 return !inode_capable(inode
, CAP_FOWNER
);
2408 * Check whether we can remove a link victim from directory dir, check
2409 * whether the type of victim is right.
2410 * 1. We can't do it if dir is read-only (done in permission())
2411 * 2. We should have write and exec permissions on dir
2412 * 3. We can't remove anything from append-only dir
2413 * 4. We can't do anything with immutable dir (done in permission())
2414 * 5. If the sticky bit on dir is set we should either
2415 * a. be owner of dir, or
2416 * b. be owner of victim, or
2417 * c. have CAP_FOWNER capability
2418 * 6. If the victim is append-only or immutable we can't do antyhing with
2419 * links pointing to it.
2420 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
2421 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
2422 * 9. We can't remove a root or mountpoint.
2423 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
2424 * nfs_async_unlink().
2426 static int may_delete(struct inode
*dir
,struct dentry
*victim
,int isdir
)
2430 if (!victim
->d_inode
)
2433 BUG_ON(victim
->d_parent
->d_inode
!= dir
);
2434 audit_inode_child(dir
, victim
, AUDIT_TYPE_CHILD_DELETE
);
2436 error
= inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
2441 if (check_sticky(dir
, victim
->d_inode
)||IS_APPEND(victim
->d_inode
)||
2442 IS_IMMUTABLE(victim
->d_inode
) || IS_SWAPFILE(victim
->d_inode
))
2445 if (!S_ISDIR(victim
->d_inode
->i_mode
))
2447 if (IS_ROOT(victim
))
2449 } else if (S_ISDIR(victim
->d_inode
->i_mode
))
2451 if (IS_DEADDIR(dir
))
2453 if (victim
->d_flags
& DCACHE_NFSFS_RENAMED
)
2458 /* Check whether we can create an object with dentry child in directory
2460 * 1. We can't do it if child already exists (open has special treatment for
2461 * this case, but since we are inlined it's OK)
2462 * 2. We can't do it if dir is read-only (done in permission())
2463 * 3. We should have write and exec permissions on dir
2464 * 4. We can't do it if dir is immutable (done in permission())
2466 static inline int may_create(struct inode
*dir
, struct dentry
*child
)
2470 if (IS_DEADDIR(dir
))
2472 return inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
2476 * p1 and p2 should be directories on the same fs.
2478 struct dentry
*lock_rename(struct dentry
*p1
, struct dentry
*p2
)
2483 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2487 mutex_lock(&p1
->d_inode
->i_sb
->s_vfs_rename_mutex
);
2489 p
= d_ancestor(p2
, p1
);
2491 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2492 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_CHILD
);
2496 p
= d_ancestor(p1
, p2
);
2498 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2499 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_CHILD
);
2503 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2504 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_CHILD
);
2508 void unlock_rename(struct dentry
*p1
, struct dentry
*p2
)
2510 mutex_unlock(&p1
->d_inode
->i_mutex
);
2512 mutex_unlock(&p2
->d_inode
->i_mutex
);
2513 mutex_unlock(&p1
->d_inode
->i_sb
->s_vfs_rename_mutex
);
2517 int vfs_create(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
,
2520 int error
= may_create(dir
, dentry
);
2524 if (!dir
->i_op
->create
)
2525 return -EACCES
; /* shouldn't it be ENOSYS? */
2528 error
= security_inode_create(dir
, dentry
, mode
);
2531 error
= dir
->i_op
->create(dir
, dentry
, mode
, want_excl
);
2533 fsnotify_create(dir
, dentry
);
2537 static int may_open(struct path
*path
, int acc_mode
, int flag
)
2539 struct dentry
*dentry
= path
->dentry
;
2540 struct inode
*inode
= dentry
->d_inode
;
2550 switch (inode
->i_mode
& S_IFMT
) {
2554 if (acc_mode
& MAY_WRITE
)
2559 if (path
->mnt
->mnt_flags
& MNT_NODEV
)
2568 error
= inode_permission(inode
, acc_mode
);
2573 * An append-only file must be opened in append mode for writing.
2575 if (IS_APPEND(inode
)) {
2576 if ((flag
& O_ACCMODE
) != O_RDONLY
&& !(flag
& O_APPEND
))
2582 /* O_NOATIME can only be set by the owner or superuser */
2583 if (flag
& O_NOATIME
&& !inode_owner_or_capable(inode
))
2589 static int handle_truncate(struct file
*filp
)
2591 struct path
*path
= &filp
->f_path
;
2592 struct inode
*inode
= path
->dentry
->d_inode
;
2593 int error
= get_write_access(inode
);
2597 * Refuse to truncate files with mandatory locks held on them.
2599 error
= locks_verify_locked(inode
);
2601 error
= security_path_truncate(path
);
2603 error
= do_truncate(path
->dentry
, 0,
2604 ATTR_MTIME
|ATTR_CTIME
|ATTR_OPEN
,
2607 put_write_access(inode
);
2611 static inline int open_to_namei_flags(int flag
)
2613 if ((flag
& O_ACCMODE
) == 3)
2618 static int may_o_create(struct path
*dir
, struct dentry
*dentry
, umode_t mode
)
2620 int error
= security_path_mknod(dir
, dentry
, mode
, 0);
2624 error
= inode_permission(dir
->dentry
->d_inode
, MAY_WRITE
| MAY_EXEC
);
2628 return security_inode_create(dir
->dentry
->d_inode
, dentry
, mode
);
2632 * Attempt to atomically look up, create and open a file from a negative
2635 * Returns 0 if successful. The file will have been created and attached to
2636 * @file by the filesystem calling finish_open().
2638 * Returns 1 if the file was looked up only or didn't need creating. The
2639 * caller will need to perform the open themselves. @path will have been
2640 * updated to point to the new dentry. This may be negative.
2642 * Returns an error code otherwise.
2644 static int atomic_open(struct nameidata
*nd
, struct dentry
*dentry
,
2645 struct path
*path
, struct file
*file
,
2646 const struct open_flags
*op
,
2647 bool got_write
, bool need_lookup
,
2650 struct inode
*dir
= nd
->path
.dentry
->d_inode
;
2651 unsigned open_flag
= open_to_namei_flags(op
->open_flag
);
2655 int create_error
= 0;
2656 struct dentry
*const DENTRY_NOT_SET
= (void *) -1UL;
2658 BUG_ON(dentry
->d_inode
);
2660 /* Don't create child dentry for a dead directory. */
2661 if (unlikely(IS_DEADDIR(dir
))) {
2667 if ((open_flag
& O_CREAT
) && !IS_POSIXACL(dir
))
2668 mode
&= ~current_umask();
2670 if ((open_flag
& (O_EXCL
| O_CREAT
)) == (O_EXCL
| O_CREAT
)) {
2671 open_flag
&= ~O_TRUNC
;
2672 *opened
|= FILE_CREATED
;
2676 * Checking write permission is tricky, bacuse we don't know if we are
2677 * going to actually need it: O_CREAT opens should work as long as the
2678 * file exists. But checking existence breaks atomicity. The trick is
2679 * to check access and if not granted clear O_CREAT from the flags.
2681 * Another problem is returing the "right" error value (e.g. for an
2682 * O_EXCL open we want to return EEXIST not EROFS).
2684 if (((open_flag
& (O_CREAT
| O_TRUNC
)) ||
2685 (open_flag
& O_ACCMODE
) != O_RDONLY
) && unlikely(!got_write
)) {
2686 if (!(open_flag
& O_CREAT
)) {
2688 * No O_CREATE -> atomicity not a requirement -> fall
2689 * back to lookup + open
2692 } else if (open_flag
& (O_EXCL
| O_TRUNC
)) {
2693 /* Fall back and fail with the right error */
2694 create_error
= -EROFS
;
2697 /* No side effects, safe to clear O_CREAT */
2698 create_error
= -EROFS
;
2699 open_flag
&= ~O_CREAT
;
2703 if (open_flag
& O_CREAT
) {
2704 error
= may_o_create(&nd
->path
, dentry
, mode
);
2706 create_error
= error
;
2707 if (open_flag
& O_EXCL
)
2709 open_flag
&= ~O_CREAT
;
2713 if (nd
->flags
& LOOKUP_DIRECTORY
)
2714 open_flag
|= O_DIRECTORY
;
2716 file
->f_path
.dentry
= DENTRY_NOT_SET
;
2717 file
->f_path
.mnt
= nd
->path
.mnt
;
2718 error
= dir
->i_op
->atomic_open(dir
, dentry
, file
, open_flag
, mode
,
2721 if (create_error
&& error
== -ENOENT
)
2722 error
= create_error
;
2726 acc_mode
= op
->acc_mode
;
2727 if (*opened
& FILE_CREATED
) {
2728 fsnotify_create(dir
, dentry
);
2729 acc_mode
= MAY_OPEN
;
2732 if (error
) { /* returned 1, that is */
2733 if (WARN_ON(file
->f_path
.dentry
== DENTRY_NOT_SET
)) {
2737 if (file
->f_path
.dentry
) {
2739 dentry
= file
->f_path
.dentry
;
2741 if (create_error
&& dentry
->d_inode
== NULL
) {
2742 error
= create_error
;
2749 * We didn't have the inode before the open, so check open permission
2752 error
= may_open(&file
->f_path
, acc_mode
, open_flag
);
2762 dentry
= lookup_real(dir
, dentry
, nd
->flags
);
2764 return PTR_ERR(dentry
);
2767 int open_flag
= op
->open_flag
;
2769 error
= create_error
;
2770 if ((open_flag
& O_EXCL
)) {
2771 if (!dentry
->d_inode
)
2773 } else if (!dentry
->d_inode
) {
2775 } else if ((open_flag
& O_TRUNC
) &&
2776 S_ISREG(dentry
->d_inode
->i_mode
)) {
2779 /* will fail later, go on to get the right error */
2783 path
->dentry
= dentry
;
2784 path
->mnt
= nd
->path
.mnt
;
2789 * Look up and maybe create and open the last component.
2791 * Must be called with i_mutex held on parent.
2793 * Returns 0 if the file was successfully atomically created (if necessary) and
2794 * opened. In this case the file will be returned attached to @file.
2796 * Returns 1 if the file was not completely opened at this time, though lookups
2797 * and creations will have been performed and the dentry returned in @path will
2798 * be positive upon return if O_CREAT was specified. If O_CREAT wasn't
2799 * specified then a negative dentry may be returned.
2801 * An error code is returned otherwise.
2803 * FILE_CREATE will be set in @*opened if the dentry was created and will be
2804 * cleared otherwise prior to returning.
2806 static int lookup_open(struct nameidata
*nd
, struct path
*path
,
2808 const struct open_flags
*op
,
2809 bool got_write
, int *opened
)
2811 struct dentry
*dir
= nd
->path
.dentry
;
2812 struct inode
*dir_inode
= dir
->d_inode
;
2813 struct dentry
*dentry
;
2817 *opened
&= ~FILE_CREATED
;
2818 dentry
= lookup_dcache(&nd
->last
, dir
, nd
->flags
, &need_lookup
);
2820 return PTR_ERR(dentry
);
2822 /* Cached positive dentry: will open in f_op->open */
2823 if (!need_lookup
&& dentry
->d_inode
)
2826 if ((nd
->flags
& LOOKUP_OPEN
) && dir_inode
->i_op
->atomic_open
) {
2827 return atomic_open(nd
, dentry
, path
, file
, op
, got_write
,
2828 need_lookup
, opened
);
2832 BUG_ON(dentry
->d_inode
);
2834 dentry
= lookup_real(dir_inode
, dentry
, nd
->flags
);
2836 return PTR_ERR(dentry
);
2839 /* Negative dentry, just create the file */
2840 if (!dentry
->d_inode
&& (op
->open_flag
& O_CREAT
)) {
2841 umode_t mode
= op
->mode
;
2842 if (!IS_POSIXACL(dir
->d_inode
))
2843 mode
&= ~current_umask();
2845 * This write is needed to ensure that a
2846 * rw->ro transition does not occur between
2847 * the time when the file is created and when
2848 * a permanent write count is taken through
2849 * the 'struct file' in finish_open().
2855 *opened
|= FILE_CREATED
;
2856 error
= security_path_mknod(&nd
->path
, dentry
, mode
, 0);
2859 error
= vfs_create(dir
->d_inode
, dentry
, mode
,
2860 nd
->flags
& LOOKUP_EXCL
);
2865 path
->dentry
= dentry
;
2866 path
->mnt
= nd
->path
.mnt
;
2875 * Handle the last step of open()
2877 static int do_last(struct nameidata
*nd
, struct path
*path
,
2878 struct file
*file
, const struct open_flags
*op
,
2879 int *opened
, struct filename
*name
)
2881 struct dentry
*dir
= nd
->path
.dentry
;
2882 int open_flag
= op
->open_flag
;
2883 bool will_truncate
= (open_flag
& O_TRUNC
) != 0;
2884 bool got_write
= false;
2885 int acc_mode
= op
->acc_mode
;
2886 struct inode
*inode
;
2887 bool symlink_ok
= false;
2888 struct path save_parent
= { .dentry
= NULL
, .mnt
= NULL
};
2889 bool retried
= false;
2892 nd
->flags
&= ~LOOKUP_PARENT
;
2893 nd
->flags
|= op
->intent
;
2895 if (nd
->last_type
!= LAST_NORM
) {
2896 error
= handle_dots(nd
, nd
->last_type
);
2902 if (!(open_flag
& O_CREAT
)) {
2903 if (nd
->last
.name
[nd
->last
.len
])
2904 nd
->flags
|= LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
;
2905 if (open_flag
& O_PATH
&& !(nd
->flags
& LOOKUP_FOLLOW
))
2907 /* we _can_ be in RCU mode here */
2908 error
= lookup_fast(nd
, path
, &inode
);
2915 BUG_ON(nd
->inode
!= dir
->d_inode
);
2917 /* create side of things */
2919 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED
2920 * has been cleared when we got to the last component we are
2923 error
= complete_walk(nd
);
2927 audit_inode(name
, dir
, LOOKUP_PARENT
);
2929 /* trailing slashes? */
2930 if (nd
->last
.name
[nd
->last
.len
])
2935 if (op
->open_flag
& (O_CREAT
| O_TRUNC
| O_WRONLY
| O_RDWR
)) {
2936 error
= mnt_want_write(nd
->path
.mnt
);
2940 * do _not_ fail yet - we might not need that or fail with
2941 * a different error; let lookup_open() decide; we'll be
2942 * dropping this one anyway.
2945 mutex_lock(&dir
->d_inode
->i_mutex
);
2946 error
= lookup_open(nd
, path
, file
, op
, got_write
, opened
);
2947 mutex_unlock(&dir
->d_inode
->i_mutex
);
2953 if ((*opened
& FILE_CREATED
) ||
2954 !S_ISREG(file_inode(file
)->i_mode
))
2955 will_truncate
= false;
2957 audit_inode(name
, file
->f_path
.dentry
, 0);
2961 if (*opened
& FILE_CREATED
) {
2962 /* Don't check for write permission, don't truncate */
2963 open_flag
&= ~O_TRUNC
;
2964 will_truncate
= false;
2965 acc_mode
= MAY_OPEN
;
2966 path_to_nameidata(path
, nd
);
2967 goto finish_open_created
;
2971 * create/update audit record if it already exists.
2973 if (path
->dentry
->d_inode
)
2974 audit_inode(name
, path
->dentry
, 0);
2977 * If atomic_open() acquired write access it is dropped now due to
2978 * possible mount and symlink following (this might be optimized away if
2982 mnt_drop_write(nd
->path
.mnt
);
2987 if ((open_flag
& (O_EXCL
| O_CREAT
)) == (O_EXCL
| O_CREAT
))
2990 error
= follow_managed(path
, nd
->flags
);
2995 nd
->flags
|= LOOKUP_JUMPED
;
2997 BUG_ON(nd
->flags
& LOOKUP_RCU
);
2998 inode
= path
->dentry
->d_inode
;
3000 /* we _can_ be in RCU mode here */
3003 path_to_nameidata(path
, nd
);
3007 if (should_follow_link(inode
, !symlink_ok
)) {
3008 if (nd
->flags
& LOOKUP_RCU
) {
3009 if (unlikely(unlazy_walk(nd
, path
->dentry
))) {
3014 BUG_ON(inode
!= path
->dentry
->d_inode
);
3018 if ((nd
->flags
& LOOKUP_RCU
) || nd
->path
.mnt
!= path
->mnt
) {
3019 path_to_nameidata(path
, nd
);
3021 save_parent
.dentry
= nd
->path
.dentry
;
3022 save_parent
.mnt
= mntget(path
->mnt
);
3023 nd
->path
.dentry
= path
->dentry
;
3027 /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
3029 error
= complete_walk(nd
);
3031 path_put(&save_parent
);
3034 audit_inode(name
, nd
->path
.dentry
, 0);
3036 if ((open_flag
& O_CREAT
) && S_ISDIR(nd
->inode
->i_mode
))
3039 if ((nd
->flags
& LOOKUP_DIRECTORY
) && !can_lookup(nd
->inode
))
3041 if (!S_ISREG(nd
->inode
->i_mode
))
3042 will_truncate
= false;
3044 if (will_truncate
) {
3045 error
= mnt_want_write(nd
->path
.mnt
);
3050 finish_open_created
:
3051 error
= may_open(&nd
->path
, acc_mode
, open_flag
);
3054 file
->f_path
.mnt
= nd
->path
.mnt
;
3055 error
= finish_open(file
, nd
->path
.dentry
, NULL
, opened
);
3057 if (error
== -EOPENSTALE
)
3062 error
= open_check_o_direct(file
);
3065 error
= ima_file_check(file
, op
->acc_mode
);
3069 if (will_truncate
) {
3070 error
= handle_truncate(file
);
3076 mnt_drop_write(nd
->path
.mnt
);
3077 path_put(&save_parent
);
3082 path_put_conditional(path
, nd
);
3089 /* If no saved parent or already retried then can't retry */
3090 if (!save_parent
.dentry
|| retried
)
3093 BUG_ON(save_parent
.dentry
!= dir
);
3094 path_put(&nd
->path
);
3095 nd
->path
= save_parent
;
3096 nd
->inode
= dir
->d_inode
;
3097 save_parent
.mnt
= NULL
;
3098 save_parent
.dentry
= NULL
;
3100 mnt_drop_write(nd
->path
.mnt
);
3107 static int do_tmpfile(int dfd
, struct filename
*pathname
,
3108 struct nameidata
*nd
, int flags
,
3109 const struct open_flags
*op
,
3110 struct file
*file
, int *opened
)
3112 static const struct qstr name
= QSTR_INIT("/", 1);
3113 struct dentry
*dentry
, *child
;
3115 int error
= path_lookupat(dfd
, pathname
->name
,
3116 flags
| LOOKUP_DIRECTORY
, nd
);
3117 if (unlikely(error
))
3119 error
= mnt_want_write(nd
->path
.mnt
);
3120 if (unlikely(error
))
3122 /* we want directory to be writable */
3123 error
= inode_permission(nd
->inode
, MAY_WRITE
| MAY_EXEC
);
3126 dentry
= nd
->path
.dentry
;
3127 dir
= dentry
->d_inode
;
3128 if (!dir
->i_op
->tmpfile
) {
3129 error
= -EOPNOTSUPP
;
3132 child
= d_alloc(dentry
, &name
);
3133 if (unlikely(!child
)) {
3137 nd
->flags
&= ~LOOKUP_DIRECTORY
;
3138 nd
->flags
|= op
->intent
;
3139 dput(nd
->path
.dentry
);
3140 nd
->path
.dentry
= child
;
3141 error
= dir
->i_op
->tmpfile(dir
, nd
->path
.dentry
, op
->mode
);
3144 audit_inode(pathname
, nd
->path
.dentry
, 0);
3145 error
= may_open(&nd
->path
, op
->acc_mode
, op
->open_flag
);
3148 file
->f_path
.mnt
= nd
->path
.mnt
;
3149 error
= finish_open(file
, nd
->path
.dentry
, NULL
, opened
);
3152 error
= open_check_o_direct(file
);
3155 } else if (!(op
->open_flag
& O_EXCL
)) {
3156 struct inode
*inode
= file_inode(file
);
3157 spin_lock(&inode
->i_lock
);
3158 inode
->i_state
|= I_LINKABLE
;
3159 spin_unlock(&inode
->i_lock
);
3162 mnt_drop_write(nd
->path
.mnt
);
3164 path_put(&nd
->path
);
3168 static struct file
*path_openat(int dfd
, struct filename
*pathname
,
3169 struct nameidata
*nd
, const struct open_flags
*op
, int flags
)
3171 struct file
*base
= NULL
;
3177 file
= get_empty_filp();
3181 file
->f_flags
= op
->open_flag
;
3183 if (unlikely(file
->f_flags
& __O_TMPFILE
)) {
3184 error
= do_tmpfile(dfd
, pathname
, nd
, flags
, op
, file
, &opened
);
3188 error
= path_init(dfd
, pathname
->name
, flags
| LOOKUP_PARENT
, nd
, &base
);
3189 if (unlikely(error
))
3192 current
->total_link_count
= 0;
3193 error
= link_path_walk(pathname
->name
, nd
);
3194 if (unlikely(error
))
3197 error
= do_last(nd
, &path
, file
, op
, &opened
, pathname
);
3198 while (unlikely(error
> 0)) { /* trailing symlink */
3199 struct path link
= path
;
3201 if (!(nd
->flags
& LOOKUP_FOLLOW
)) {
3202 path_put_conditional(&path
, nd
);
3203 path_put(&nd
->path
);
3207 error
= may_follow_link(&link
, nd
);
3208 if (unlikely(error
))
3210 nd
->flags
|= LOOKUP_PARENT
;
3211 nd
->flags
&= ~(LOOKUP_OPEN
|LOOKUP_CREATE
|LOOKUP_EXCL
);
3212 error
= follow_link(&link
, nd
, &cookie
);
3213 if (unlikely(error
))
3215 error
= do_last(nd
, &path
, file
, op
, &opened
, pathname
);
3216 put_link(nd
, &link
, cookie
);
3219 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
))
3220 path_put(&nd
->root
);
3223 if (!(opened
& FILE_OPENED
)) {
3227 if (unlikely(error
)) {
3228 if (error
== -EOPENSTALE
) {
3229 if (flags
& LOOKUP_RCU
)
3234 file
= ERR_PTR(error
);
3239 struct file
*do_filp_open(int dfd
, struct filename
*pathname
,
3240 const struct open_flags
*op
)
3242 struct nameidata nd
;
3243 int flags
= op
->lookup_flags
;
3246 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
| LOOKUP_RCU
);
3247 if (unlikely(filp
== ERR_PTR(-ECHILD
)))
3248 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
);
3249 if (unlikely(filp
== ERR_PTR(-ESTALE
)))
3250 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
| LOOKUP_REVAL
);
3254 struct file
*do_file_open_root(struct dentry
*dentry
, struct vfsmount
*mnt
,
3255 const char *name
, const struct open_flags
*op
)
3257 struct nameidata nd
;
3259 struct filename filename
= { .name
= name
};
3260 int flags
= op
->lookup_flags
| LOOKUP_ROOT
;
3263 nd
.root
.dentry
= dentry
;
3265 if (dentry
->d_inode
->i_op
->follow_link
&& op
->intent
& LOOKUP_OPEN
)
3266 return ERR_PTR(-ELOOP
);
3268 file
= path_openat(-1, &filename
, &nd
, op
, flags
| LOOKUP_RCU
);
3269 if (unlikely(file
== ERR_PTR(-ECHILD
)))
3270 file
= path_openat(-1, &filename
, &nd
, op
, flags
);
3271 if (unlikely(file
== ERR_PTR(-ESTALE
)))
3272 file
= path_openat(-1, &filename
, &nd
, op
, flags
| LOOKUP_REVAL
);
3276 struct dentry
*kern_path_create(int dfd
, const char *pathname
,
3277 struct path
*path
, unsigned int lookup_flags
)
3279 struct dentry
*dentry
= ERR_PTR(-EEXIST
);
3280 struct nameidata nd
;
3283 bool is_dir
= (lookup_flags
& LOOKUP_DIRECTORY
);
3286 * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any
3287 * other flags passed in are ignored!
3289 lookup_flags
&= LOOKUP_REVAL
;
3291 error
= do_path_lookup(dfd
, pathname
, LOOKUP_PARENT
|lookup_flags
, &nd
);
3293 return ERR_PTR(error
);
3296 * Yucky last component or no last component at all?
3297 * (foo/., foo/.., /////)
3299 if (nd
.last_type
!= LAST_NORM
)
3301 nd
.flags
&= ~LOOKUP_PARENT
;
3302 nd
.flags
|= LOOKUP_CREATE
| LOOKUP_EXCL
;
3304 /* don't fail immediately if it's r/o, at least try to report other errors */
3305 err2
= mnt_want_write(nd
.path
.mnt
);
3307 * Do the final lookup.
3309 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
3310 dentry
= lookup_hash(&nd
);
3315 if (dentry
->d_inode
)
3318 * Special case - lookup gave negative, but... we had foo/bar/
3319 * From the vfs_mknod() POV we just have a negative dentry -
3320 * all is fine. Let's be bastards - you had / on the end, you've
3321 * been asking for (non-existent) directory. -ENOENT for you.
3323 if (unlikely(!is_dir
&& nd
.last
.name
[nd
.last
.len
])) {
3327 if (unlikely(err2
)) {
3335 dentry
= ERR_PTR(error
);
3337 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
3339 mnt_drop_write(nd
.path
.mnt
);
3344 EXPORT_SYMBOL(kern_path_create
);
3346 void done_path_create(struct path
*path
, struct dentry
*dentry
)
3349 mutex_unlock(&path
->dentry
->d_inode
->i_mutex
);
3350 mnt_drop_write(path
->mnt
);
3353 EXPORT_SYMBOL(done_path_create
);
3355 struct dentry
*user_path_create(int dfd
, const char __user
*pathname
,
3356 struct path
*path
, unsigned int lookup_flags
)
3358 struct filename
*tmp
= getname(pathname
);
3361 return ERR_CAST(tmp
);
3362 res
= kern_path_create(dfd
, tmp
->name
, path
, lookup_flags
);
3366 EXPORT_SYMBOL(user_path_create
);
3368 int vfs_mknod(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
, dev_t dev
)
3370 int error
= may_create(dir
, dentry
);
3375 if ((S_ISCHR(mode
) || S_ISBLK(mode
)) && !capable(CAP_MKNOD
))
3378 if (!dir
->i_op
->mknod
)
3381 error
= devcgroup_inode_mknod(mode
, dev
);
3385 error
= security_inode_mknod(dir
, dentry
, mode
, dev
);
3389 error
= dir
->i_op
->mknod(dir
, dentry
, mode
, dev
);
3391 fsnotify_create(dir
, dentry
);
3395 static int may_mknod(umode_t mode
)
3397 switch (mode
& S_IFMT
) {
3403 case 0: /* zero mode translates to S_IFREG */
3412 SYSCALL_DEFINE4(mknodat
, int, dfd
, const char __user
*, filename
, umode_t
, mode
,
3415 struct dentry
*dentry
;
3418 unsigned int lookup_flags
= 0;
3420 error
= may_mknod(mode
);
3424 dentry
= user_path_create(dfd
, filename
, &path
, lookup_flags
);
3426 return PTR_ERR(dentry
);
3428 if (!IS_POSIXACL(path
.dentry
->d_inode
))
3429 mode
&= ~current_umask();
3430 error
= security_path_mknod(&path
, dentry
, mode
, dev
);
3433 switch (mode
& S_IFMT
) {
3434 case 0: case S_IFREG
:
3435 error
= vfs_create(path
.dentry
->d_inode
,dentry
,mode
,true);
3437 case S_IFCHR
: case S_IFBLK
:
3438 error
= vfs_mknod(path
.dentry
->d_inode
,dentry
,mode
,
3439 new_decode_dev(dev
));
3441 case S_IFIFO
: case S_IFSOCK
:
3442 error
= vfs_mknod(path
.dentry
->d_inode
,dentry
,mode
,0);
3446 done_path_create(&path
, dentry
);
3447 if (retry_estale(error
, lookup_flags
)) {
3448 lookup_flags
|= LOOKUP_REVAL
;
3454 SYSCALL_DEFINE3(mknod
, const char __user
*, filename
, umode_t
, mode
, unsigned, dev
)
3456 return sys_mknodat(AT_FDCWD
, filename
, mode
, dev
);
3459 int vfs_mkdir(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
)
3461 int error
= may_create(dir
, dentry
);
3462 unsigned max_links
= dir
->i_sb
->s_max_links
;
3467 if (!dir
->i_op
->mkdir
)
3470 mode
&= (S_IRWXUGO
|S_ISVTX
);
3471 error
= security_inode_mkdir(dir
, dentry
, mode
);
3475 if (max_links
&& dir
->i_nlink
>= max_links
)
3478 error
= dir
->i_op
->mkdir(dir
, dentry
, mode
);
3480 fsnotify_mkdir(dir
, dentry
);
3484 SYSCALL_DEFINE3(mkdirat
, int, dfd
, const char __user
*, pathname
, umode_t
, mode
)
3486 struct dentry
*dentry
;
3489 unsigned int lookup_flags
= LOOKUP_DIRECTORY
;
3492 dentry
= user_path_create(dfd
, pathname
, &path
, lookup_flags
);
3494 return PTR_ERR(dentry
);
3496 if (!IS_POSIXACL(path
.dentry
->d_inode
))
3497 mode
&= ~current_umask();
3498 error
= security_path_mkdir(&path
, dentry
, mode
);
3500 error
= vfs_mkdir(path
.dentry
->d_inode
, dentry
, mode
);
3501 done_path_create(&path
, dentry
);
3502 if (retry_estale(error
, lookup_flags
)) {
3503 lookup_flags
|= LOOKUP_REVAL
;
3509 SYSCALL_DEFINE2(mkdir
, const char __user
*, pathname
, umode_t
, mode
)
3511 return sys_mkdirat(AT_FDCWD
, pathname
, mode
);
3515 * The dentry_unhash() helper will try to drop the dentry early: we
3516 * should have a usage count of 1 if we're the only user of this
3517 * dentry, and if that is true (possibly after pruning the dcache),
3518 * then we drop the dentry now.
3520 * A low-level filesystem can, if it choses, legally
3523 * if (!d_unhashed(dentry))
3526 * if it cannot handle the case of removing a directory
3527 * that is still in use by something else..
3529 void dentry_unhash(struct dentry
*dentry
)
3531 shrink_dcache_parent(dentry
);
3532 spin_lock(&dentry
->d_lock
);
3533 if (dentry
->d_lockref
.count
== 1)
3535 spin_unlock(&dentry
->d_lock
);
3538 int vfs_rmdir(struct inode
*dir
, struct dentry
*dentry
)
3540 int error
= may_delete(dir
, dentry
, 1);
3545 if (!dir
->i_op
->rmdir
)
3549 mutex_lock(&dentry
->d_inode
->i_mutex
);
3552 if (d_mountpoint(dentry
))
3555 error
= security_inode_rmdir(dir
, dentry
);
3559 shrink_dcache_parent(dentry
);
3560 error
= dir
->i_op
->rmdir(dir
, dentry
);
3564 dentry
->d_inode
->i_flags
|= S_DEAD
;
3568 mutex_unlock(&dentry
->d_inode
->i_mutex
);
3575 static long do_rmdir(int dfd
, const char __user
*pathname
)
3578 struct filename
*name
;
3579 struct dentry
*dentry
;
3580 struct nameidata nd
;
3581 unsigned int lookup_flags
= 0;
3583 name
= user_path_parent(dfd
, pathname
, &nd
, lookup_flags
);
3585 return PTR_ERR(name
);
3587 switch(nd
.last_type
) {
3599 nd
.flags
&= ~LOOKUP_PARENT
;
3600 error
= mnt_want_write(nd
.path
.mnt
);
3604 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
3605 dentry
= lookup_hash(&nd
);
3606 error
= PTR_ERR(dentry
);
3609 if (!dentry
->d_inode
) {
3613 error
= security_path_rmdir(&nd
.path
, dentry
);
3616 error
= vfs_rmdir(nd
.path
.dentry
->d_inode
, dentry
);
3620 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
3621 mnt_drop_write(nd
.path
.mnt
);
3625 if (retry_estale(error
, lookup_flags
)) {
3626 lookup_flags
|= LOOKUP_REVAL
;
3632 SYSCALL_DEFINE1(rmdir
, const char __user
*, pathname
)
3634 return do_rmdir(AT_FDCWD
, pathname
);
3637 int vfs_unlink(struct inode
*dir
, struct dentry
*dentry
)
3639 int error
= may_delete(dir
, dentry
, 0);
3644 if (!dir
->i_op
->unlink
)
3647 mutex_lock(&dentry
->d_inode
->i_mutex
);
3648 if (d_mountpoint(dentry
))
3651 error
= security_inode_unlink(dir
, dentry
);
3653 error
= dir
->i_op
->unlink(dir
, dentry
);
3658 mutex_unlock(&dentry
->d_inode
->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(dentry
->d_inode
);
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 unsigned int lookup_flags
= 0;
3684 name
= user_path_parent(dfd
, pathname
, &nd
, lookup_flags
);
3686 return PTR_ERR(name
);
3689 if (nd
.last_type
!= LAST_NORM
)
3692 nd
.flags
&= ~LOOKUP_PARENT
;
3693 error
= mnt_want_write(nd
.path
.mnt
);
3697 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
3698 dentry
= lookup_hash(&nd
);
3699 error
= PTR_ERR(dentry
);
3700 if (!IS_ERR(dentry
)) {
3701 /* Why not before? Because we want correct error value */
3702 if (nd
.last
.name
[nd
.last
.len
])
3704 inode
= dentry
->d_inode
;
3708 error
= security_path_unlink(&nd
.path
, dentry
);
3711 error
= vfs_unlink(nd
.path
.dentry
->d_inode
, dentry
);
3715 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
3717 iput(inode
); /* truncate the inode here */
3718 mnt_drop_write(nd
.path
.mnt
);
3722 if (retry_estale(error
, lookup_flags
)) {
3723 lookup_flags
|= LOOKUP_REVAL
;
3730 error
= !dentry
->d_inode
? -ENOENT
:
3731 S_ISDIR(dentry
->d_inode
->i_mode
) ? -EISDIR
: -ENOTDIR
;
3735 SYSCALL_DEFINE3(unlinkat
, int, dfd
, const char __user
*, pathname
, int, flag
)
3737 if ((flag
& ~AT_REMOVEDIR
) != 0)
3740 if (flag
& AT_REMOVEDIR
)
3741 return do_rmdir(dfd
, pathname
);
3743 return do_unlinkat(dfd
, pathname
);
3746 SYSCALL_DEFINE1(unlink
, const char __user
*, pathname
)
3748 return do_unlinkat(AT_FDCWD
, pathname
);
3751 int vfs_symlink(struct inode
*dir
, struct dentry
*dentry
, const char *oldname
)
3753 int error
= may_create(dir
, dentry
);
3758 if (!dir
->i_op
->symlink
)
3761 error
= security_inode_symlink(dir
, dentry
, oldname
);
3765 error
= dir
->i_op
->symlink(dir
, dentry
, oldname
);
3767 fsnotify_create(dir
, dentry
);
3771 SYSCALL_DEFINE3(symlinkat
, const char __user
*, oldname
,
3772 int, newdfd
, const char __user
*, newname
)
3775 struct filename
*from
;
3776 struct dentry
*dentry
;
3778 unsigned int lookup_flags
= 0;
3780 from
= getname(oldname
);
3782 return PTR_ERR(from
);
3784 dentry
= user_path_create(newdfd
, newname
, &path
, lookup_flags
);
3785 error
= PTR_ERR(dentry
);
3789 error
= security_path_symlink(&path
, dentry
, from
->name
);
3791 error
= vfs_symlink(path
.dentry
->d_inode
, dentry
, from
->name
);
3792 done_path_create(&path
, dentry
);
3793 if (retry_estale(error
, lookup_flags
)) {
3794 lookup_flags
|= LOOKUP_REVAL
;
3802 SYSCALL_DEFINE2(symlink
, const char __user
*, oldname
, const char __user
*, newname
)
3804 return sys_symlinkat(oldname
, AT_FDCWD
, newname
);
3807 int vfs_link(struct dentry
*old_dentry
, struct inode
*dir
, struct dentry
*new_dentry
)
3809 struct inode
*inode
= old_dentry
->d_inode
;
3810 unsigned max_links
= dir
->i_sb
->s_max_links
;
3816 error
= may_create(dir
, new_dentry
);
3820 if (dir
->i_sb
!= inode
->i_sb
)
3824 * A link to an append-only or immutable file cannot be created.
3826 if (IS_APPEND(inode
) || IS_IMMUTABLE(inode
))
3828 if (!dir
->i_op
->link
)
3830 if (S_ISDIR(inode
->i_mode
))
3833 error
= security_inode_link(old_dentry
, dir
, new_dentry
);
3837 mutex_lock(&inode
->i_mutex
);
3838 /* Make sure we don't allow creating hardlink to an unlinked file */
3839 if (inode
->i_nlink
== 0 && !(inode
->i_state
& I_LINKABLE
))
3841 else if (max_links
&& inode
->i_nlink
>= max_links
)
3844 error
= dir
->i_op
->link(old_dentry
, dir
, new_dentry
);
3846 if (!error
&& (inode
->i_state
& I_LINKABLE
)) {
3847 spin_lock(&inode
->i_lock
);
3848 inode
->i_state
&= ~I_LINKABLE
;
3849 spin_unlock(&inode
->i_lock
);
3851 mutex_unlock(&inode
->i_mutex
);
3853 fsnotify_link(dir
, inode
, new_dentry
);
3858 * Hardlinks are often used in delicate situations. We avoid
3859 * security-related surprises by not following symlinks on the
3862 * We don't follow them on the oldname either to be compatible
3863 * with linux 2.0, and to avoid hard-linking to directories
3864 * and other special files. --ADM
3866 SYSCALL_DEFINE5(linkat
, int, olddfd
, const char __user
*, oldname
,
3867 int, newdfd
, const char __user
*, newname
, int, flags
)
3869 struct dentry
*new_dentry
;
3870 struct path old_path
, new_path
;
3874 if ((flags
& ~(AT_SYMLINK_FOLLOW
| AT_EMPTY_PATH
)) != 0)
3877 * To use null names we require CAP_DAC_READ_SEARCH
3878 * This ensures that not everyone will be able to create
3879 * handlink using the passed filedescriptor.
3881 if (flags
& AT_EMPTY_PATH
) {
3882 if (!capable(CAP_DAC_READ_SEARCH
))
3887 if (flags
& AT_SYMLINK_FOLLOW
)
3888 how
|= LOOKUP_FOLLOW
;
3890 error
= user_path_at(olddfd
, oldname
, how
, &old_path
);
3894 new_dentry
= user_path_create(newdfd
, newname
, &new_path
,
3895 (how
& LOOKUP_REVAL
));
3896 error
= PTR_ERR(new_dentry
);
3897 if (IS_ERR(new_dentry
))
3901 if (old_path
.mnt
!= new_path
.mnt
)
3903 error
= may_linkat(&old_path
);
3904 if (unlikely(error
))
3906 error
= security_path_link(old_path
.dentry
, &new_path
, new_dentry
);
3909 error
= vfs_link(old_path
.dentry
, new_path
.dentry
->d_inode
, new_dentry
);
3911 done_path_create(&new_path
, new_dentry
);
3912 if (retry_estale(error
, how
)) {
3913 how
|= LOOKUP_REVAL
;
3917 path_put(&old_path
);
3922 SYSCALL_DEFINE2(link
, const char __user
*, oldname
, const char __user
*, newname
)
3924 return sys_linkat(AT_FDCWD
, oldname
, AT_FDCWD
, newname
, 0);
3928 * The worst of all namespace operations - renaming directory. "Perverted"
3929 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
3931 * a) we can get into loop creation. Check is done in is_subdir().
3932 * b) race potential - two innocent renames can create a loop together.
3933 * That's where 4.4 screws up. Current fix: serialization on
3934 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
3936 * c) we have to lock _three_ objects - parents and victim (if it exists).
3937 * And that - after we got ->i_mutex on parents (until then we don't know
3938 * whether the target exists). Solution: try to be smart with locking
3939 * order for inodes. We rely on the fact that tree topology may change
3940 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
3941 * move will be locked. Thus we can rank directories by the tree
3942 * (ancestors first) and rank all non-directories after them.
3943 * That works since everybody except rename does "lock parent, lookup,
3944 * lock child" and rename is under ->s_vfs_rename_mutex.
3945 * HOWEVER, it relies on the assumption that any object with ->lookup()
3946 * has no more than 1 dentry. If "hybrid" objects will ever appear,
3947 * we'd better make sure that there's no link(2) for them.
3948 * d) conversion from fhandle to dentry may come in the wrong moment - when
3949 * we are removing the target. Solution: we will have to grab ->i_mutex
3950 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
3951 * ->i_mutex on parents, which works but leads to some truly excessive
3954 static int vfs_rename_dir(struct inode
*old_dir
, struct dentry
*old_dentry
,
3955 struct inode
*new_dir
, struct dentry
*new_dentry
)
3958 struct inode
*target
= new_dentry
->d_inode
;
3959 unsigned max_links
= new_dir
->i_sb
->s_max_links
;
3962 * If we are going to change the parent - check write permissions,
3963 * we'll need to flip '..'.
3965 if (new_dir
!= old_dir
) {
3966 error
= inode_permission(old_dentry
->d_inode
, MAY_WRITE
);
3971 error
= security_inode_rename(old_dir
, old_dentry
, new_dir
, new_dentry
);
3977 mutex_lock(&target
->i_mutex
);
3980 if (d_mountpoint(old_dentry
) || d_mountpoint(new_dentry
))
3984 if (max_links
&& !target
&& new_dir
!= old_dir
&&
3985 new_dir
->i_nlink
>= max_links
)
3989 shrink_dcache_parent(new_dentry
);
3990 error
= old_dir
->i_op
->rename(old_dir
, old_dentry
, new_dir
, new_dentry
);
3995 target
->i_flags
|= S_DEAD
;
3996 dont_mount(new_dentry
);
4000 mutex_unlock(&target
->i_mutex
);
4003 if (!(old_dir
->i_sb
->s_type
->fs_flags
& FS_RENAME_DOES_D_MOVE
))
4004 d_move(old_dentry
,new_dentry
);
4008 static int vfs_rename_other(struct inode
*old_dir
, struct dentry
*old_dentry
,
4009 struct inode
*new_dir
, struct dentry
*new_dentry
)
4011 struct inode
*target
= new_dentry
->d_inode
;
4014 error
= security_inode_rename(old_dir
, old_dentry
, new_dir
, new_dentry
);
4020 mutex_lock(&target
->i_mutex
);
4023 if (d_mountpoint(old_dentry
)||d_mountpoint(new_dentry
))
4026 error
= old_dir
->i_op
->rename(old_dir
, old_dentry
, new_dir
, new_dentry
);
4031 dont_mount(new_dentry
);
4032 if (!(old_dir
->i_sb
->s_type
->fs_flags
& FS_RENAME_DOES_D_MOVE
))
4033 d_move(old_dentry
, new_dentry
);
4036 mutex_unlock(&target
->i_mutex
);
4041 int vfs_rename(struct inode
*old_dir
, struct dentry
*old_dentry
,
4042 struct inode
*new_dir
, struct dentry
*new_dentry
)
4045 int is_dir
= S_ISDIR(old_dentry
->d_inode
->i_mode
);
4046 const unsigned char *old_name
;
4048 if (old_dentry
->d_inode
== new_dentry
->d_inode
)
4051 error
= may_delete(old_dir
, old_dentry
, is_dir
);
4055 if (!new_dentry
->d_inode
)
4056 error
= may_create(new_dir
, new_dentry
);
4058 error
= may_delete(new_dir
, new_dentry
, is_dir
);
4062 if (!old_dir
->i_op
->rename
)
4065 old_name
= fsnotify_oldname_init(old_dentry
->d_name
.name
);
4068 error
= vfs_rename_dir(old_dir
,old_dentry
,new_dir
,new_dentry
);
4070 error
= vfs_rename_other(old_dir
,old_dentry
,new_dir
,new_dentry
);
4072 fsnotify_move(old_dir
, new_dir
, old_name
, is_dir
,
4073 new_dentry
->d_inode
, old_dentry
);
4074 fsnotify_oldname_free(old_name
);
4079 SYSCALL_DEFINE4(renameat
, int, olddfd
, const char __user
*, oldname
,
4080 int, newdfd
, const char __user
*, newname
)
4082 struct dentry
*old_dir
, *new_dir
;
4083 struct dentry
*old_dentry
, *new_dentry
;
4084 struct dentry
*trap
;
4085 struct nameidata oldnd
, newnd
;
4086 struct filename
*from
;
4087 struct filename
*to
;
4088 unsigned int lookup_flags
= 0;
4089 bool should_retry
= false;
4092 from
= user_path_parent(olddfd
, oldname
, &oldnd
, lookup_flags
);
4094 error
= PTR_ERR(from
);
4098 to
= user_path_parent(newdfd
, newname
, &newnd
, lookup_flags
);
4100 error
= PTR_ERR(to
);
4105 if (oldnd
.path
.mnt
!= newnd
.path
.mnt
)
4108 old_dir
= oldnd
.path
.dentry
;
4110 if (oldnd
.last_type
!= LAST_NORM
)
4113 new_dir
= newnd
.path
.dentry
;
4114 if (newnd
.last_type
!= LAST_NORM
)
4117 error
= mnt_want_write(oldnd
.path
.mnt
);
4121 oldnd
.flags
&= ~LOOKUP_PARENT
;
4122 newnd
.flags
&= ~LOOKUP_PARENT
;
4123 newnd
.flags
|= LOOKUP_RENAME_TARGET
;
4125 trap
= lock_rename(new_dir
, old_dir
);
4127 old_dentry
= lookup_hash(&oldnd
);
4128 error
= PTR_ERR(old_dentry
);
4129 if (IS_ERR(old_dentry
))
4131 /* source must exist */
4133 if (!old_dentry
->d_inode
)
4135 /* unless the source is a directory trailing slashes give -ENOTDIR */
4136 if (!S_ISDIR(old_dentry
->d_inode
->i_mode
)) {
4138 if (oldnd
.last
.name
[oldnd
.last
.len
])
4140 if (newnd
.last
.name
[newnd
.last
.len
])
4143 /* source should not be ancestor of target */
4145 if (old_dentry
== trap
)
4147 new_dentry
= lookup_hash(&newnd
);
4148 error
= PTR_ERR(new_dentry
);
4149 if (IS_ERR(new_dentry
))
4151 /* target should not be an ancestor of source */
4153 if (new_dentry
== trap
)
4156 error
= security_path_rename(&oldnd
.path
, old_dentry
,
4157 &newnd
.path
, new_dentry
);
4160 error
= vfs_rename(old_dir
->d_inode
, old_dentry
,
4161 new_dir
->d_inode
, new_dentry
);
4167 unlock_rename(new_dir
, old_dir
);
4168 mnt_drop_write(oldnd
.path
.mnt
);
4170 if (retry_estale(error
, lookup_flags
))
4171 should_retry
= true;
4172 path_put(&newnd
.path
);
4175 path_put(&oldnd
.path
);
4178 should_retry
= false;
4179 lookup_flags
|= LOOKUP_REVAL
;
4186 SYSCALL_DEFINE2(rename
, const char __user
*, oldname
, const char __user
*, newname
)
4188 return sys_renameat(AT_FDCWD
, oldname
, AT_FDCWD
, newname
);
4191 int vfs_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
, const char *link
)
4195 len
= PTR_ERR(link
);
4200 if (len
> (unsigned) buflen
)
4202 if (copy_to_user(buffer
, link
, len
))
4209 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
4210 * have ->follow_link() touching nd only in nd_set_link(). Using (or not
4211 * using) it for any given inode is up to filesystem.
4213 int generic_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
)
4215 struct nameidata nd
;
4220 cookie
= dentry
->d_inode
->i_op
->follow_link(dentry
, &nd
);
4222 return PTR_ERR(cookie
);
4224 res
= vfs_readlink(dentry
, buffer
, buflen
, nd_get_link(&nd
));
4225 if (dentry
->d_inode
->i_op
->put_link
)
4226 dentry
->d_inode
->i_op
->put_link(dentry
, &nd
, cookie
);
4230 int vfs_follow_link(struct nameidata
*nd
, const char *link
)
4232 return __vfs_follow_link(nd
, link
);
4235 /* get the link contents into pagecache */
4236 static char *page_getlink(struct dentry
* dentry
, struct page
**ppage
)
4240 struct address_space
*mapping
= dentry
->d_inode
->i_mapping
;
4241 page
= read_mapping_page(mapping
, 0, NULL
);
4246 nd_terminate_link(kaddr
, dentry
->d_inode
->i_size
, PAGE_SIZE
- 1);
4250 int page_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
)
4252 struct page
*page
= NULL
;
4253 char *s
= page_getlink(dentry
, &page
);
4254 int res
= vfs_readlink(dentry
,buffer
,buflen
,s
);
4257 page_cache_release(page
);
4262 void *page_follow_link_light(struct dentry
*dentry
, struct nameidata
*nd
)
4264 struct page
*page
= NULL
;
4265 nd_set_link(nd
, page_getlink(dentry
, &page
));
4269 void page_put_link(struct dentry
*dentry
, struct nameidata
*nd
, void *cookie
)
4271 struct page
*page
= cookie
;
4275 page_cache_release(page
);
4280 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
4282 int __page_symlink(struct inode
*inode
, const char *symname
, int len
, int nofs
)
4284 struct address_space
*mapping
= inode
->i_mapping
;
4289 unsigned int flags
= AOP_FLAG_UNINTERRUPTIBLE
;
4291 flags
|= AOP_FLAG_NOFS
;
4294 err
= pagecache_write_begin(NULL
, mapping
, 0, len
-1,
4295 flags
, &page
, &fsdata
);
4299 kaddr
= kmap_atomic(page
);
4300 memcpy(kaddr
, symname
, len
-1);
4301 kunmap_atomic(kaddr
);
4303 err
= pagecache_write_end(NULL
, mapping
, 0, len
-1, len
-1,
4310 mark_inode_dirty(inode
);
4316 int page_symlink(struct inode
*inode
, const char *symname
, int len
)
4318 return __page_symlink(inode
, symname
, len
,
4319 !(mapping_gfp_mask(inode
->i_mapping
) & __GFP_FS
));
4322 const struct inode_operations page_symlink_inode_operations
= {
4323 .readlink
= generic_readlink
,
4324 .follow_link
= page_follow_link_light
,
4325 .put_link
= page_put_link
,
4328 EXPORT_SYMBOL(user_path_at
);
4329 EXPORT_SYMBOL(follow_down_one
);
4330 EXPORT_SYMBOL(follow_down
);
4331 EXPORT_SYMBOL(follow_up
);
4332 EXPORT_SYMBOL(get_write_access
); /* nfsd */
4333 EXPORT_SYMBOL(lock_rename
);
4334 EXPORT_SYMBOL(lookup_one_len
);
4335 EXPORT_SYMBOL(page_follow_link_light
);
4336 EXPORT_SYMBOL(page_put_link
);
4337 EXPORT_SYMBOL(page_readlink
);
4338 EXPORT_SYMBOL(__page_symlink
);
4339 EXPORT_SYMBOL(page_symlink
);
4340 EXPORT_SYMBOL(page_symlink_inode_operations
);
4341 EXPORT_SYMBOL(kern_path
);
4342 EXPORT_SYMBOL(vfs_path_lookup
);
4343 EXPORT_SYMBOL(inode_permission
);
4344 EXPORT_SYMBOL(unlock_rename
);
4345 EXPORT_SYMBOL(vfs_create
);
4346 EXPORT_SYMBOL(vfs_follow_link
);
4347 EXPORT_SYMBOL(vfs_link
);
4348 EXPORT_SYMBOL(vfs_mkdir
);
4349 EXPORT_SYMBOL(vfs_mknod
);
4350 EXPORT_SYMBOL(generic_permission
);
4351 EXPORT_SYMBOL(vfs_readlink
);
4352 EXPORT_SYMBOL(vfs_rename
);
4353 EXPORT_SYMBOL(vfs_rmdir
);
4354 EXPORT_SYMBOL(vfs_symlink
);
4355 EXPORT_SYMBOL(vfs_unlink
);
4356 EXPORT_SYMBOL(dentry_unhash
);
4357 EXPORT_SYMBOL(generic_readlink
);