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(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(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
;
513 BUG_ON(!(nd
->flags
& LOOKUP_RCU
));
514 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
)) {
516 spin_lock(&fs
->lock
);
517 if (nd
->root
.mnt
!= fs
->root
.mnt
||
518 nd
->root
.dentry
!= fs
->root
.dentry
)
521 spin_lock(&parent
->d_lock
);
523 if (!__d_rcu_to_refcount(parent
, nd
->seq
))
525 BUG_ON(nd
->inode
!= parent
->d_inode
);
527 if (dentry
->d_parent
!= parent
)
529 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
530 if (!__d_rcu_to_refcount(dentry
, nd
->seq
))
533 * If the sequence check on the child dentry passed, then
534 * the child has not been removed from its parent. This
535 * means the parent dentry must be valid and able to take
536 * a reference at this point.
538 BUG_ON(!IS_ROOT(dentry
) && dentry
->d_parent
!= parent
);
539 BUG_ON(!parent
->d_count
);
541 spin_unlock(&dentry
->d_lock
);
543 spin_unlock(&parent
->d_lock
);
546 spin_unlock(&fs
->lock
);
548 mntget(nd
->path
.mnt
);
551 nd
->flags
&= ~LOOKUP_RCU
;
555 spin_unlock(&dentry
->d_lock
);
557 spin_unlock(&parent
->d_lock
);
560 spin_unlock(&fs
->lock
);
564 static inline int d_revalidate(struct dentry
*dentry
, unsigned int flags
)
566 return dentry
->d_op
->d_revalidate(dentry
, flags
);
570 * complete_walk - successful completion of path walk
571 * @nd: pointer nameidata
573 * If we had been in RCU mode, drop out of it and legitimize nd->path.
574 * Revalidate the final result, unless we'd already done that during
575 * the path walk or the filesystem doesn't ask for it. Return 0 on
576 * success, -error on failure. In case of failure caller does not
577 * need to drop nd->path.
579 static int complete_walk(struct nameidata
*nd
)
581 struct dentry
*dentry
= nd
->path
.dentry
;
584 if (nd
->flags
& LOOKUP_RCU
) {
585 nd
->flags
&= ~LOOKUP_RCU
;
586 if (!(nd
->flags
& LOOKUP_ROOT
))
588 spin_lock(&dentry
->d_lock
);
589 if (unlikely(!__d_rcu_to_refcount(dentry
, nd
->seq
))) {
590 spin_unlock(&dentry
->d_lock
);
594 BUG_ON(nd
->inode
!= dentry
->d_inode
);
595 spin_unlock(&dentry
->d_lock
);
596 mntget(nd
->path
.mnt
);
600 if (likely(!(nd
->flags
& LOOKUP_JUMPED
)))
603 if (likely(!(dentry
->d_flags
& DCACHE_OP_REVALIDATE
)))
606 if (likely(!(dentry
->d_sb
->s_type
->fs_flags
& FS_REVAL_DOT
)))
609 /* Note: we do not d_invalidate() */
610 status
= d_revalidate(dentry
, nd
->flags
);
621 static __always_inline
void set_root(struct nameidata
*nd
)
624 get_fs_root(current
->fs
, &nd
->root
);
627 static int link_path_walk(const char *, struct nameidata
*);
629 static __always_inline
void set_root_rcu(struct nameidata
*nd
)
632 struct fs_struct
*fs
= current
->fs
;
636 seq
= read_seqcount_begin(&fs
->seq
);
638 nd
->seq
= __read_seqcount_begin(&nd
->root
.dentry
->d_seq
);
639 } while (read_seqcount_retry(&fs
->seq
, seq
));
643 static __always_inline
int __vfs_follow_link(struct nameidata
*nd
, const char *link
)
655 nd
->flags
|= LOOKUP_JUMPED
;
657 nd
->inode
= nd
->path
.dentry
->d_inode
;
659 ret
= link_path_walk(link
, nd
);
663 return PTR_ERR(link
);
666 static void path_put_conditional(struct path
*path
, struct nameidata
*nd
)
669 if (path
->mnt
!= nd
->path
.mnt
)
673 static inline void path_to_nameidata(const struct path
*path
,
674 struct nameidata
*nd
)
676 if (!(nd
->flags
& LOOKUP_RCU
)) {
677 dput(nd
->path
.dentry
);
678 if (nd
->path
.mnt
!= path
->mnt
)
679 mntput(nd
->path
.mnt
);
681 nd
->path
.mnt
= path
->mnt
;
682 nd
->path
.dentry
= path
->dentry
;
686 * Helper to directly jump to a known parsed path from ->follow_link,
687 * caller must have taken a reference to path beforehand.
689 void nd_jump_link(struct nameidata
*nd
, struct path
*path
)
694 nd
->inode
= nd
->path
.dentry
->d_inode
;
695 nd
->flags
|= LOOKUP_JUMPED
;
697 BUG_ON(nd
->inode
->i_op
->follow_link
);
700 static inline void put_link(struct nameidata
*nd
, struct path
*link
, void *cookie
)
702 struct inode
*inode
= link
->dentry
->d_inode
;
703 if (inode
->i_op
->put_link
)
704 inode
->i_op
->put_link(link
->dentry
, nd
, cookie
);
708 int sysctl_protected_symlinks __read_mostly
= 0;
709 int sysctl_protected_hardlinks __read_mostly
= 0;
712 * may_follow_link - Check symlink following for unsafe situations
713 * @link: The path of the symlink
714 * @nd: nameidata pathwalk data
716 * In the case of the sysctl_protected_symlinks sysctl being enabled,
717 * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
718 * in a sticky world-writable directory. This is to protect privileged
719 * processes from failing races against path names that may change out
720 * from under them by way of other users creating malicious symlinks.
721 * It will permit symlinks to be followed only when outside a sticky
722 * world-writable directory, or when the uid of the symlink and follower
723 * match, or when the directory owner matches the symlink's owner.
725 * Returns 0 if following the symlink is allowed, -ve on error.
727 static inline int may_follow_link(struct path
*link
, struct nameidata
*nd
)
729 const struct inode
*inode
;
730 const struct inode
*parent
;
732 if (!sysctl_protected_symlinks
)
735 /* Allowed if owner and follower match. */
736 inode
= link
->dentry
->d_inode
;
737 if (uid_eq(current_cred()->fsuid
, inode
->i_uid
))
740 /* Allowed if parent directory not sticky and world-writable. */
741 parent
= nd
->path
.dentry
->d_inode
;
742 if ((parent
->i_mode
& (S_ISVTX
|S_IWOTH
)) != (S_ISVTX
|S_IWOTH
))
745 /* Allowed if parent directory and link owner match. */
746 if (uid_eq(parent
->i_uid
, inode
->i_uid
))
749 audit_log_link_denied("follow_link", link
);
750 path_put_conditional(link
, nd
);
756 * safe_hardlink_source - Check for safe hardlink conditions
757 * @inode: the source inode to hardlink from
759 * Return false if at least one of the following conditions:
760 * - inode is not a regular file
762 * - inode is setgid and group-exec
763 * - access failure for read and write
765 * Otherwise returns true.
767 static bool safe_hardlink_source(struct inode
*inode
)
769 umode_t mode
= inode
->i_mode
;
771 /* Special files should not get pinned to the filesystem. */
775 /* Setuid files should not get pinned to the filesystem. */
779 /* Executable setgid files should not get pinned to the filesystem. */
780 if ((mode
& (S_ISGID
| S_IXGRP
)) == (S_ISGID
| S_IXGRP
))
783 /* Hardlinking to unreadable or unwritable sources is dangerous. */
784 if (inode_permission(inode
, MAY_READ
| MAY_WRITE
))
791 * may_linkat - Check permissions for creating a hardlink
792 * @link: the source to hardlink from
794 * Block hardlink when all of:
795 * - sysctl_protected_hardlinks enabled
796 * - fsuid does not match inode
797 * - hardlink source is unsafe (see safe_hardlink_source() above)
800 * Returns 0 if successful, -ve on error.
802 static int may_linkat(struct path
*link
)
804 const struct cred
*cred
;
807 if (!sysctl_protected_hardlinks
)
810 cred
= current_cred();
811 inode
= link
->dentry
->d_inode
;
813 /* Source inode owner (or CAP_FOWNER) can hardlink all they like,
814 * otherwise, it must be a safe source.
816 if (uid_eq(cred
->fsuid
, inode
->i_uid
) || safe_hardlink_source(inode
) ||
820 audit_log_link_denied("linkat", link
);
824 static __always_inline
int
825 follow_link(struct path
*link
, struct nameidata
*nd
, void **p
)
827 struct dentry
*dentry
= link
->dentry
;
831 BUG_ON(nd
->flags
& LOOKUP_RCU
);
833 if (link
->mnt
== nd
->path
.mnt
)
837 if (unlikely(current
->total_link_count
>= 40))
838 goto out_put_nd_path
;
841 current
->total_link_count
++;
844 nd_set_link(nd
, NULL
);
846 error
= security_inode_follow_link(link
->dentry
, nd
);
848 goto out_put_nd_path
;
850 nd
->last_type
= LAST_BIND
;
851 *p
= dentry
->d_inode
->i_op
->follow_link(dentry
, nd
);
854 goto out_put_nd_path
;
859 error
= __vfs_follow_link(nd
, s
);
861 put_link(nd
, link
, *p
);
873 static int follow_up_rcu(struct path
*path
)
875 struct mount
*mnt
= real_mount(path
->mnt
);
876 struct mount
*parent
;
877 struct dentry
*mountpoint
;
879 parent
= mnt
->mnt_parent
;
880 if (&parent
->mnt
== path
->mnt
)
882 mountpoint
= mnt
->mnt_mountpoint
;
883 path
->dentry
= mountpoint
;
884 path
->mnt
= &parent
->mnt
;
889 * follow_up - Find the mountpoint of path's vfsmount
891 * Given a path, find the mountpoint of its source file system.
892 * Replace @path with the path of the mountpoint in the parent mount.
895 * Return 1 if we went up a level and 0 if we were already at the
898 int follow_up(struct path
*path
)
900 struct mount
*mnt
= real_mount(path
->mnt
);
901 struct mount
*parent
;
902 struct dentry
*mountpoint
;
904 br_read_lock(&vfsmount_lock
);
905 parent
= mnt
->mnt_parent
;
907 br_read_unlock(&vfsmount_lock
);
910 mntget(&parent
->mnt
);
911 mountpoint
= dget(mnt
->mnt_mountpoint
);
912 br_read_unlock(&vfsmount_lock
);
914 path
->dentry
= mountpoint
;
916 path
->mnt
= &parent
->mnt
;
921 * Perform an automount
922 * - return -EISDIR to tell follow_managed() to stop and return the path we
925 static int follow_automount(struct path
*path
, unsigned flags
,
928 struct vfsmount
*mnt
;
931 if (!path
->dentry
->d_op
|| !path
->dentry
->d_op
->d_automount
)
934 /* We don't want to mount if someone's just doing a stat -
935 * unless they're stat'ing a directory and appended a '/' to
938 * We do, however, want to mount if someone wants to open or
939 * create a file of any type under the mountpoint, wants to
940 * traverse through the mountpoint or wants to open the
941 * mounted directory. Also, autofs may mark negative dentries
942 * as being automount points. These will need the attentions
943 * of the daemon to instantiate them before they can be used.
945 if (!(flags
& (LOOKUP_PARENT
| LOOKUP_DIRECTORY
|
946 LOOKUP_OPEN
| LOOKUP_CREATE
| LOOKUP_AUTOMOUNT
)) &&
947 path
->dentry
->d_inode
)
950 current
->total_link_count
++;
951 if (current
->total_link_count
>= 40)
954 mnt
= path
->dentry
->d_op
->d_automount(path
);
957 * The filesystem is allowed to return -EISDIR here to indicate
958 * it doesn't want to automount. For instance, autofs would do
959 * this so that its userspace daemon can mount on this dentry.
961 * However, we can only permit this if it's a terminal point in
962 * the path being looked up; if it wasn't then the remainder of
963 * the path is inaccessible and we should say so.
965 if (PTR_ERR(mnt
) == -EISDIR
&& (flags
& LOOKUP_PARENT
))
970 if (!mnt
) /* mount collision */
974 /* lock_mount() may release path->mnt on error */
978 err
= finish_automount(mnt
, path
);
982 /* Someone else made a mount here whilst we were busy */
987 path
->dentry
= dget(mnt
->mnt_root
);
996 * Handle a dentry that is managed in some way.
997 * - Flagged for transit management (autofs)
998 * - Flagged as mountpoint
999 * - Flagged as automount point
1001 * This may only be called in refwalk mode.
1003 * Serialization is taken care of in namespace.c
1005 static int follow_managed(struct path
*path
, unsigned flags
)
1007 struct vfsmount
*mnt
= path
->mnt
; /* held by caller, must be left alone */
1009 bool need_mntput
= false;
1012 /* Given that we're not holding a lock here, we retain the value in a
1013 * local variable for each dentry as we look at it so that we don't see
1014 * the components of that value change under us */
1015 while (managed
= ACCESS_ONCE(path
->dentry
->d_flags
),
1016 managed
&= DCACHE_MANAGED_DENTRY
,
1017 unlikely(managed
!= 0)) {
1018 /* Allow the filesystem to manage the transit without i_mutex
1020 if (managed
& DCACHE_MANAGE_TRANSIT
) {
1021 BUG_ON(!path
->dentry
->d_op
);
1022 BUG_ON(!path
->dentry
->d_op
->d_manage
);
1023 ret
= path
->dentry
->d_op
->d_manage(path
->dentry
, false);
1028 /* Transit to a mounted filesystem. */
1029 if (managed
& DCACHE_MOUNTED
) {
1030 struct vfsmount
*mounted
= lookup_mnt(path
);
1035 path
->mnt
= mounted
;
1036 path
->dentry
= dget(mounted
->mnt_root
);
1041 /* Something is mounted on this dentry in another
1042 * namespace and/or whatever was mounted there in this
1043 * namespace got unmounted before we managed to get the
1047 /* Handle an automount point */
1048 if (managed
& DCACHE_NEED_AUTOMOUNT
) {
1049 ret
= follow_automount(path
, flags
, &need_mntput
);
1055 /* We didn't change the current path point */
1059 if (need_mntput
&& path
->mnt
== mnt
)
1063 return ret
< 0 ? ret
: need_mntput
;
1066 int follow_down_one(struct path
*path
)
1068 struct vfsmount
*mounted
;
1070 mounted
= lookup_mnt(path
);
1074 path
->mnt
= mounted
;
1075 path
->dentry
= dget(mounted
->mnt_root
);
1081 static inline bool managed_dentry_might_block(struct dentry
*dentry
)
1083 return (dentry
->d_flags
& DCACHE_MANAGE_TRANSIT
&&
1084 dentry
->d_op
->d_manage(dentry
, true) < 0);
1088 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
1089 * we meet a managed dentry that would need blocking.
1091 static bool __follow_mount_rcu(struct nameidata
*nd
, struct path
*path
,
1092 struct inode
**inode
)
1095 struct mount
*mounted
;
1097 * Don't forget we might have a non-mountpoint managed dentry
1098 * that wants to block transit.
1100 if (unlikely(managed_dentry_might_block(path
->dentry
)))
1103 if (!d_mountpoint(path
->dentry
))
1106 mounted
= __lookup_mnt(path
->mnt
, path
->dentry
, 1);
1109 path
->mnt
= &mounted
->mnt
;
1110 path
->dentry
= mounted
->mnt
.mnt_root
;
1111 nd
->flags
|= LOOKUP_JUMPED
;
1112 nd
->seq
= read_seqcount_begin(&path
->dentry
->d_seq
);
1114 * Update the inode too. We don't need to re-check the
1115 * dentry sequence number here after this d_inode read,
1116 * because a mount-point is always pinned.
1118 *inode
= path
->dentry
->d_inode
;
1123 static void follow_mount_rcu(struct nameidata
*nd
)
1125 while (d_mountpoint(nd
->path
.dentry
)) {
1126 struct mount
*mounted
;
1127 mounted
= __lookup_mnt(nd
->path
.mnt
, nd
->path
.dentry
, 1);
1130 nd
->path
.mnt
= &mounted
->mnt
;
1131 nd
->path
.dentry
= mounted
->mnt
.mnt_root
;
1132 nd
->seq
= read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1136 static int follow_dotdot_rcu(struct nameidata
*nd
)
1141 if (nd
->path
.dentry
== nd
->root
.dentry
&&
1142 nd
->path
.mnt
== nd
->root
.mnt
) {
1145 if (nd
->path
.dentry
!= nd
->path
.mnt
->mnt_root
) {
1146 struct dentry
*old
= nd
->path
.dentry
;
1147 struct dentry
*parent
= old
->d_parent
;
1150 seq
= read_seqcount_begin(&parent
->d_seq
);
1151 if (read_seqcount_retry(&old
->d_seq
, nd
->seq
))
1153 nd
->path
.dentry
= parent
;
1157 if (!follow_up_rcu(&nd
->path
))
1159 nd
->seq
= read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1161 follow_mount_rcu(nd
);
1162 nd
->inode
= nd
->path
.dentry
->d_inode
;
1166 nd
->flags
&= ~LOOKUP_RCU
;
1167 if (!(nd
->flags
& LOOKUP_ROOT
))
1168 nd
->root
.mnt
= NULL
;
1174 * Follow down to the covering mount currently visible to userspace. At each
1175 * point, the filesystem owning that dentry may be queried as to whether the
1176 * caller is permitted to proceed or not.
1178 int follow_down(struct path
*path
)
1183 while (managed
= ACCESS_ONCE(path
->dentry
->d_flags
),
1184 unlikely(managed
& DCACHE_MANAGED_DENTRY
)) {
1185 /* Allow the filesystem to manage the transit without i_mutex
1188 * We indicate to the filesystem if someone is trying to mount
1189 * something here. This gives autofs the chance to deny anyone
1190 * other than its daemon the right to mount on its
1193 * The filesystem may sleep at this point.
1195 if (managed
& DCACHE_MANAGE_TRANSIT
) {
1196 BUG_ON(!path
->dentry
->d_op
);
1197 BUG_ON(!path
->dentry
->d_op
->d_manage
);
1198 ret
= path
->dentry
->d_op
->d_manage(
1199 path
->dentry
, false);
1201 return ret
== -EISDIR
? 0 : ret
;
1204 /* Transit to a mounted filesystem. */
1205 if (managed
& DCACHE_MOUNTED
) {
1206 struct vfsmount
*mounted
= lookup_mnt(path
);
1211 path
->mnt
= mounted
;
1212 path
->dentry
= dget(mounted
->mnt_root
);
1216 /* Don't handle automount points here */
1223 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1225 static void follow_mount(struct path
*path
)
1227 while (d_mountpoint(path
->dentry
)) {
1228 struct vfsmount
*mounted
= lookup_mnt(path
);
1233 path
->mnt
= mounted
;
1234 path
->dentry
= dget(mounted
->mnt_root
);
1238 static void follow_dotdot(struct nameidata
*nd
)
1243 struct dentry
*old
= nd
->path
.dentry
;
1245 if (nd
->path
.dentry
== nd
->root
.dentry
&&
1246 nd
->path
.mnt
== nd
->root
.mnt
) {
1249 if (nd
->path
.dentry
!= nd
->path
.mnt
->mnt_root
) {
1250 /* rare case of legitimate dget_parent()... */
1251 nd
->path
.dentry
= dget_parent(nd
->path
.dentry
);
1255 if (!follow_up(&nd
->path
))
1258 follow_mount(&nd
->path
);
1259 nd
->inode
= nd
->path
.dentry
->d_inode
;
1263 * This looks up the name in dcache, possibly revalidates the old dentry and
1264 * allocates a new one if not found or not valid. In the need_lookup argument
1265 * returns whether i_op->lookup is necessary.
1267 * dir->d_inode->i_mutex must be held
1269 static struct dentry
*lookup_dcache(struct qstr
*name
, struct dentry
*dir
,
1270 unsigned int flags
, bool *need_lookup
)
1272 struct dentry
*dentry
;
1275 *need_lookup
= false;
1276 dentry
= d_lookup(dir
, name
);
1278 if (dentry
->d_flags
& DCACHE_OP_REVALIDATE
) {
1279 error
= d_revalidate(dentry
, flags
);
1280 if (unlikely(error
<= 0)) {
1283 return ERR_PTR(error
);
1284 } else if (!d_invalidate(dentry
)) {
1293 dentry
= d_alloc(dir
, name
);
1294 if (unlikely(!dentry
))
1295 return ERR_PTR(-ENOMEM
);
1297 *need_lookup
= true;
1303 * Call i_op->lookup on the dentry. The dentry must be negative but may be
1304 * hashed if it was pouplated with DCACHE_NEED_LOOKUP.
1306 * dir->d_inode->i_mutex must be held
1308 static struct dentry
*lookup_real(struct inode
*dir
, struct dentry
*dentry
,
1313 /* Don't create child dentry for a dead directory. */
1314 if (unlikely(IS_DEADDIR(dir
))) {
1316 return ERR_PTR(-ENOENT
);
1319 old
= dir
->i_op
->lookup(dir
, dentry
, flags
);
1320 if (unlikely(old
)) {
1327 static struct dentry
*__lookup_hash(struct qstr
*name
,
1328 struct dentry
*base
, unsigned int flags
)
1331 struct dentry
*dentry
;
1333 dentry
= lookup_dcache(name
, base
, flags
, &need_lookup
);
1337 return lookup_real(base
->d_inode
, dentry
, flags
);
1341 * It's more convoluted than I'd like it to be, but... it's still fairly
1342 * small and for now I'd prefer to have fast path as straight as possible.
1343 * It _is_ time-critical.
1345 static int lookup_fast(struct nameidata
*nd
, struct qstr
*name
,
1346 struct path
*path
, struct inode
**inode
)
1348 struct vfsmount
*mnt
= nd
->path
.mnt
;
1349 struct dentry
*dentry
, *parent
= nd
->path
.dentry
;
1355 * Rename seqlock is not required here because in the off chance
1356 * of a false negative due to a concurrent rename, we're going to
1357 * do the non-racy lookup, below.
1359 if (nd
->flags
& LOOKUP_RCU
) {
1361 dentry
= __d_lookup_rcu(parent
, name
, &seq
, nd
->inode
);
1366 * This sequence count validates that the inode matches
1367 * the dentry name information from lookup.
1369 *inode
= dentry
->d_inode
;
1370 if (read_seqcount_retry(&dentry
->d_seq
, seq
))
1374 * This sequence count validates that the parent had no
1375 * changes while we did the lookup of the dentry above.
1377 * The memory barrier in read_seqcount_begin of child is
1378 * enough, we can use __read_seqcount_retry here.
1380 if (__read_seqcount_retry(&parent
->d_seq
, nd
->seq
))
1384 if (unlikely(dentry
->d_flags
& DCACHE_OP_REVALIDATE
)) {
1385 status
= d_revalidate(dentry
, nd
->flags
);
1386 if (unlikely(status
<= 0)) {
1387 if (status
!= -ECHILD
)
1393 path
->dentry
= dentry
;
1394 if (unlikely(!__follow_mount_rcu(nd
, path
, inode
)))
1396 if (unlikely(path
->dentry
->d_flags
& DCACHE_NEED_AUTOMOUNT
))
1400 if (unlazy_walk(nd
, dentry
))
1403 dentry
= __d_lookup(parent
, name
);
1406 if (unlikely(!dentry
))
1409 if (unlikely(dentry
->d_flags
& DCACHE_OP_REVALIDATE
) && need_reval
)
1410 status
= d_revalidate(dentry
, nd
->flags
);
1411 if (unlikely(status
<= 0)) {
1416 if (!d_invalidate(dentry
)) {
1423 path
->dentry
= dentry
;
1424 err
= follow_managed(path
, nd
->flags
);
1425 if (unlikely(err
< 0)) {
1426 path_put_conditional(path
, nd
);
1430 nd
->flags
|= LOOKUP_JUMPED
;
1431 *inode
= path
->dentry
->d_inode
;
1438 /* Fast lookup failed, do it the slow way */
1439 static int lookup_slow(struct nameidata
*nd
, struct qstr
*name
,
1442 struct dentry
*dentry
, *parent
;
1445 parent
= nd
->path
.dentry
;
1446 BUG_ON(nd
->inode
!= parent
->d_inode
);
1448 mutex_lock(&parent
->d_inode
->i_mutex
);
1449 dentry
= __lookup_hash(name
, parent
, nd
->flags
);
1450 mutex_unlock(&parent
->d_inode
->i_mutex
);
1452 return PTR_ERR(dentry
);
1453 path
->mnt
= nd
->path
.mnt
;
1454 path
->dentry
= dentry
;
1455 err
= follow_managed(path
, nd
->flags
);
1456 if (unlikely(err
< 0)) {
1457 path_put_conditional(path
, nd
);
1461 nd
->flags
|= LOOKUP_JUMPED
;
1465 static inline int may_lookup(struct nameidata
*nd
)
1467 if (nd
->flags
& LOOKUP_RCU
) {
1468 int err
= inode_permission(nd
->inode
, MAY_EXEC
|MAY_NOT_BLOCK
);
1471 if (unlazy_walk(nd
, NULL
))
1474 return inode_permission(nd
->inode
, MAY_EXEC
);
1477 static inline int handle_dots(struct nameidata
*nd
, int type
)
1479 if (type
== LAST_DOTDOT
) {
1480 if (nd
->flags
& LOOKUP_RCU
) {
1481 if (follow_dotdot_rcu(nd
))
1489 static void terminate_walk(struct nameidata
*nd
)
1491 if (!(nd
->flags
& LOOKUP_RCU
)) {
1492 path_put(&nd
->path
);
1494 nd
->flags
&= ~LOOKUP_RCU
;
1495 if (!(nd
->flags
& LOOKUP_ROOT
))
1496 nd
->root
.mnt
= NULL
;
1502 * Do we need to follow links? We _really_ want to be able
1503 * to do this check without having to look at inode->i_op,
1504 * so we keep a cache of "no, this doesn't need follow_link"
1505 * for the common case.
1507 static inline int should_follow_link(struct inode
*inode
, int follow
)
1509 if (unlikely(!(inode
->i_opflags
& IOP_NOFOLLOW
))) {
1510 if (likely(inode
->i_op
->follow_link
))
1513 /* This gets set once for the inode lifetime */
1514 spin_lock(&inode
->i_lock
);
1515 inode
->i_opflags
|= IOP_NOFOLLOW
;
1516 spin_unlock(&inode
->i_lock
);
1521 static inline int walk_component(struct nameidata
*nd
, struct path
*path
,
1522 struct qstr
*name
, int type
, int follow
)
1524 struct inode
*inode
;
1527 * "." and ".." are special - ".." especially so because it has
1528 * to be able to know about the current root directory and
1529 * parent relationships.
1531 if (unlikely(type
!= LAST_NORM
))
1532 return handle_dots(nd
, type
);
1533 err
= lookup_fast(nd
, name
, path
, &inode
);
1534 if (unlikely(err
)) {
1538 err
= lookup_slow(nd
, name
, path
);
1542 inode
= path
->dentry
->d_inode
;
1548 if (should_follow_link(inode
, follow
)) {
1549 if (nd
->flags
& LOOKUP_RCU
) {
1550 if (unlikely(unlazy_walk(nd
, path
->dentry
))) {
1555 BUG_ON(inode
!= path
->dentry
->d_inode
);
1558 path_to_nameidata(path
, nd
);
1563 path_to_nameidata(path
, nd
);
1570 * This limits recursive symlink follows to 8, while
1571 * limiting consecutive symlinks to 40.
1573 * Without that kind of total limit, nasty chains of consecutive
1574 * symlinks can cause almost arbitrarily long lookups.
1576 static inline int nested_symlink(struct path
*path
, struct nameidata
*nd
)
1580 if (unlikely(current
->link_count
>= MAX_NESTED_LINKS
)) {
1581 path_put_conditional(path
, nd
);
1582 path_put(&nd
->path
);
1585 BUG_ON(nd
->depth
>= MAX_NESTED_LINKS
);
1588 current
->link_count
++;
1591 struct path link
= *path
;
1594 res
= follow_link(&link
, nd
, &cookie
);
1597 res
= walk_component(nd
, path
, &nd
->last
,
1598 nd
->last_type
, LOOKUP_FOLLOW
);
1599 put_link(nd
, &link
, cookie
);
1602 current
->link_count
--;
1608 * We really don't want to look at inode->i_op->lookup
1609 * when we don't have to. So we keep a cache bit in
1610 * the inode ->i_opflags field that says "yes, we can
1611 * do lookup on this inode".
1613 static inline int can_lookup(struct inode
*inode
)
1615 if (likely(inode
->i_opflags
& IOP_LOOKUP
))
1617 if (likely(!inode
->i_op
->lookup
))
1620 /* We do this once for the lifetime of the inode */
1621 spin_lock(&inode
->i_lock
);
1622 inode
->i_opflags
|= IOP_LOOKUP
;
1623 spin_unlock(&inode
->i_lock
);
1628 * We can do the critical dentry name comparison and hashing
1629 * operations one word at a time, but we are limited to:
1631 * - Architectures with fast unaligned word accesses. We could
1632 * do a "get_unaligned()" if this helps and is sufficiently
1635 * - Little-endian machines (so that we can generate the mask
1636 * of low bytes efficiently). Again, we *could* do a byte
1637 * swapping load on big-endian architectures if that is not
1638 * expensive enough to make the optimization worthless.
1640 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
1641 * do not trap on the (extremely unlikely) case of a page
1642 * crossing operation.
1644 * - Furthermore, we need an efficient 64-bit compile for the
1645 * 64-bit case in order to generate the "number of bytes in
1646 * the final mask". Again, that could be replaced with a
1647 * efficient population count instruction or similar.
1649 #ifdef CONFIG_DCACHE_WORD_ACCESS
1651 #include <asm/word-at-a-time.h>
1655 static inline unsigned int fold_hash(unsigned long hash
)
1657 hash
+= hash
>> (8*sizeof(int));
1661 #else /* 32-bit case */
1663 #define fold_hash(x) (x)
1667 unsigned int full_name_hash(const unsigned char *name
, unsigned int len
)
1669 unsigned long a
, mask
;
1670 unsigned long hash
= 0;
1673 a
= load_unaligned_zeropad(name
);
1674 if (len
< sizeof(unsigned long))
1678 name
+= sizeof(unsigned long);
1679 len
-= sizeof(unsigned long);
1683 mask
= ~(~0ul << len
*8);
1686 return fold_hash(hash
);
1688 EXPORT_SYMBOL(full_name_hash
);
1691 * Calculate the length and hash of the path component, and
1692 * return the length of the component;
1694 static inline unsigned long hash_name(const char *name
, unsigned int *hashp
)
1696 unsigned long a
, b
, adata
, bdata
, mask
, hash
, len
;
1697 const struct word_at_a_time constants
= WORD_AT_A_TIME_CONSTANTS
;
1700 len
= -sizeof(unsigned long);
1702 hash
= (hash
+ a
) * 9;
1703 len
+= sizeof(unsigned long);
1704 a
= load_unaligned_zeropad(name
+len
);
1705 b
= a
^ REPEAT_BYTE('/');
1706 } while (!(has_zero(a
, &adata
, &constants
) | has_zero(b
, &bdata
, &constants
)));
1708 adata
= prep_zero_mask(a
, adata
, &constants
);
1709 bdata
= prep_zero_mask(b
, bdata
, &constants
);
1711 mask
= create_zero_mask(adata
| bdata
);
1713 hash
+= a
& zero_bytemask(mask
);
1714 *hashp
= fold_hash(hash
);
1716 return len
+ find_zero(mask
);
1721 unsigned int full_name_hash(const unsigned char *name
, unsigned int len
)
1723 unsigned long hash
= init_name_hash();
1725 hash
= partial_name_hash(*name
++, hash
);
1726 return end_name_hash(hash
);
1728 EXPORT_SYMBOL(full_name_hash
);
1731 * We know there's a real path component here of at least
1734 static inline unsigned long hash_name(const char *name
, unsigned int *hashp
)
1736 unsigned long hash
= init_name_hash();
1737 unsigned long len
= 0, c
;
1739 c
= (unsigned char)*name
;
1742 hash
= partial_name_hash(c
, hash
);
1743 c
= (unsigned char)name
[len
];
1744 } while (c
&& c
!= '/');
1745 *hashp
= end_name_hash(hash
);
1753 * This is the basic name resolution function, turning a pathname into
1754 * the final dentry. We expect 'base' to be positive and a directory.
1756 * Returns 0 and nd will have valid dentry and mnt on success.
1757 * Returns error and drops reference to input namei data on failure.
1759 static int link_path_walk(const char *name
, struct nameidata
*nd
)
1769 /* At this point we know we have a real path component. */
1775 err
= may_lookup(nd
);
1779 len
= hash_name(name
, &this.hash
);
1784 if (name
[0] == '.') switch (len
) {
1786 if (name
[1] == '.') {
1788 nd
->flags
|= LOOKUP_JUMPED
;
1794 if (likely(type
== LAST_NORM
)) {
1795 struct dentry
*parent
= nd
->path
.dentry
;
1796 nd
->flags
&= ~LOOKUP_JUMPED
;
1797 if (unlikely(parent
->d_flags
& DCACHE_OP_HASH
)) {
1798 err
= parent
->d_op
->d_hash(parent
, nd
->inode
,
1806 goto last_component
;
1808 * If it wasn't NUL, we know it was '/'. Skip that
1809 * slash, and continue until no more slashes.
1813 } while (unlikely(name
[len
] == '/'));
1815 goto last_component
;
1818 err
= walk_component(nd
, &next
, &this, type
, LOOKUP_FOLLOW
);
1823 err
= nested_symlink(&next
, nd
);
1827 if (can_lookup(nd
->inode
))
1831 /* here ends the main loop */
1835 nd
->last_type
= type
;
1842 static int path_init(int dfd
, const char *name
, unsigned int flags
,
1843 struct nameidata
*nd
, struct file
**fp
)
1847 nd
->last_type
= LAST_ROOT
; /* if there are only slashes... */
1848 nd
->flags
= flags
| LOOKUP_JUMPED
;
1850 if (flags
& LOOKUP_ROOT
) {
1851 struct inode
*inode
= nd
->root
.dentry
->d_inode
;
1853 if (!can_lookup(inode
))
1855 retval
= inode_permission(inode
, MAY_EXEC
);
1859 nd
->path
= nd
->root
;
1861 if (flags
& LOOKUP_RCU
) {
1863 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1865 path_get(&nd
->path
);
1870 nd
->root
.mnt
= NULL
;
1873 if (flags
& LOOKUP_RCU
) {
1878 path_get(&nd
->root
);
1880 nd
->path
= nd
->root
;
1881 } else if (dfd
== AT_FDCWD
) {
1882 if (flags
& LOOKUP_RCU
) {
1883 struct fs_struct
*fs
= current
->fs
;
1889 seq
= read_seqcount_begin(&fs
->seq
);
1891 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1892 } while (read_seqcount_retry(&fs
->seq
, seq
));
1894 get_fs_pwd(current
->fs
, &nd
->path
);
1897 /* Caller must check execute permissions on the starting path component */
1898 struct fd f
= fdget_raw(dfd
);
1899 struct dentry
*dentry
;
1904 dentry
= f
.file
->f_path
.dentry
;
1907 if (!can_lookup(dentry
->d_inode
)) {
1913 nd
->path
= f
.file
->f_path
;
1914 if (flags
& LOOKUP_RCU
) {
1917 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1920 path_get(&nd
->path
);
1925 nd
->inode
= nd
->path
.dentry
->d_inode
;
1929 static inline int lookup_last(struct nameidata
*nd
, struct path
*path
)
1931 if (nd
->last_type
== LAST_NORM
&& nd
->last
.name
[nd
->last
.len
])
1932 nd
->flags
|= LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
;
1934 nd
->flags
&= ~LOOKUP_PARENT
;
1935 return walk_component(nd
, path
, &nd
->last
, nd
->last_type
,
1936 nd
->flags
& LOOKUP_FOLLOW
);
1939 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
1940 static int path_lookupat(int dfd
, const char *name
,
1941 unsigned int flags
, struct nameidata
*nd
)
1943 struct file
*base
= NULL
;
1948 * Path walking is largely split up into 2 different synchronisation
1949 * schemes, rcu-walk and ref-walk (explained in
1950 * Documentation/filesystems/path-lookup.txt). These share much of the
1951 * path walk code, but some things particularly setup, cleanup, and
1952 * following mounts are sufficiently divergent that functions are
1953 * duplicated. Typically there is a function foo(), and its RCU
1954 * analogue, foo_rcu().
1956 * -ECHILD is the error number of choice (just to avoid clashes) that
1957 * is returned if some aspect of an rcu-walk fails. Such an error must
1958 * be handled by restarting a traditional ref-walk (which will always
1959 * be able to complete).
1961 err
= path_init(dfd
, name
, flags
| LOOKUP_PARENT
, nd
, &base
);
1966 current
->total_link_count
= 0;
1967 err
= link_path_walk(name
, nd
);
1969 if (!err
&& !(flags
& LOOKUP_PARENT
)) {
1970 err
= lookup_last(nd
, &path
);
1973 struct path link
= path
;
1974 err
= may_follow_link(&link
, nd
);
1977 nd
->flags
|= LOOKUP_PARENT
;
1978 err
= follow_link(&link
, nd
, &cookie
);
1981 err
= lookup_last(nd
, &path
);
1982 put_link(nd
, &link
, cookie
);
1987 err
= complete_walk(nd
);
1989 if (!err
&& nd
->flags
& LOOKUP_DIRECTORY
) {
1990 if (!nd
->inode
->i_op
->lookup
) {
1991 path_put(&nd
->path
);
1999 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
)) {
2000 path_put(&nd
->root
);
2001 nd
->root
.mnt
= NULL
;
2006 static int filename_lookup(int dfd
, struct filename
*name
,
2007 unsigned int flags
, struct nameidata
*nd
)
2009 int retval
= path_lookupat(dfd
, name
->name
, flags
| LOOKUP_RCU
, nd
);
2010 if (unlikely(retval
== -ECHILD
))
2011 retval
= path_lookupat(dfd
, name
->name
, flags
, nd
);
2012 if (unlikely(retval
== -ESTALE
))
2013 retval
= path_lookupat(dfd
, name
->name
,
2014 flags
| LOOKUP_REVAL
, nd
);
2016 if (likely(!retval
))
2017 audit_inode(name
, nd
->path
.dentry
, flags
& LOOKUP_PARENT
);
2021 static int do_path_lookup(int dfd
, const char *name
,
2022 unsigned int flags
, struct nameidata
*nd
)
2024 struct filename filename
= { .name
= name
};
2026 return filename_lookup(dfd
, &filename
, flags
, nd
);
2029 /* does lookup, returns the object with parent locked */
2030 struct dentry
*kern_path_locked(const char *name
, struct path
*path
)
2032 struct nameidata nd
;
2034 int err
= do_path_lookup(AT_FDCWD
, name
, LOOKUP_PARENT
, &nd
);
2036 return ERR_PTR(err
);
2037 if (nd
.last_type
!= LAST_NORM
) {
2039 return ERR_PTR(-EINVAL
);
2041 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2042 d
= __lookup_hash(&nd
.last
, nd
.path
.dentry
, 0);
2044 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
2052 int kern_path(const char *name
, unsigned int flags
, struct path
*path
)
2054 struct nameidata nd
;
2055 int res
= do_path_lookup(AT_FDCWD
, name
, flags
, &nd
);
2062 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
2063 * @dentry: pointer to dentry of the base directory
2064 * @mnt: pointer to vfs mount of the base directory
2065 * @name: pointer to file name
2066 * @flags: lookup flags
2067 * @path: pointer to struct path to fill
2069 int vfs_path_lookup(struct dentry
*dentry
, struct vfsmount
*mnt
,
2070 const char *name
, unsigned int flags
,
2073 struct nameidata nd
;
2075 nd
.root
.dentry
= dentry
;
2077 BUG_ON(flags
& LOOKUP_PARENT
);
2078 /* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */
2079 err
= do_path_lookup(AT_FDCWD
, name
, flags
| LOOKUP_ROOT
, &nd
);
2086 * Restricted form of lookup. Doesn't follow links, single-component only,
2087 * needs parent already locked. Doesn't follow mounts.
2090 static struct dentry
*lookup_hash(struct nameidata
*nd
)
2092 return __lookup_hash(&nd
->last
, nd
->path
.dentry
, nd
->flags
);
2096 * lookup_one_len - filesystem helper to lookup single pathname component
2097 * @name: pathname component to lookup
2098 * @base: base directory to lookup from
2099 * @len: maximum length @len should be interpreted to
2101 * Note that this routine is purely a helper for filesystem usage and should
2102 * not be called by generic code. Also note that by using this function the
2103 * nameidata argument is passed to the filesystem methods and a filesystem
2104 * using this helper needs to be prepared for that.
2106 struct dentry
*lookup_one_len(const char *name
, struct dentry
*base
, int len
)
2112 WARN_ON_ONCE(!mutex_is_locked(&base
->d_inode
->i_mutex
));
2116 this.hash
= full_name_hash(name
, len
);
2118 return ERR_PTR(-EACCES
);
2120 if (unlikely(name
[0] == '.')) {
2121 if (len
< 2 || (len
== 2 && name
[1] == '.'))
2122 return ERR_PTR(-EACCES
);
2126 c
= *(const unsigned char *)name
++;
2127 if (c
== '/' || c
== '\0')
2128 return ERR_PTR(-EACCES
);
2131 * See if the low-level filesystem might want
2132 * to use its own hash..
2134 if (base
->d_flags
& DCACHE_OP_HASH
) {
2135 int err
= base
->d_op
->d_hash(base
, base
->d_inode
, &this);
2137 return ERR_PTR(err
);
2140 err
= inode_permission(base
->d_inode
, MAY_EXEC
);
2142 return ERR_PTR(err
);
2144 return __lookup_hash(&this, base
, 0);
2147 int user_path_at_empty(int dfd
, const char __user
*name
, unsigned flags
,
2148 struct path
*path
, int *empty
)
2150 struct nameidata nd
;
2151 struct filename
*tmp
= getname_flags(name
, flags
, empty
);
2152 int err
= PTR_ERR(tmp
);
2155 BUG_ON(flags
& LOOKUP_PARENT
);
2157 err
= filename_lookup(dfd
, tmp
, flags
, &nd
);
2165 int user_path_at(int dfd
, const char __user
*name
, unsigned flags
,
2168 return user_path_at_empty(dfd
, name
, flags
, path
, NULL
);
2172 * NB: most callers don't do anything directly with the reference to the
2173 * to struct filename, but the nd->last pointer points into the name string
2174 * allocated by getname. So we must hold the reference to it until all
2175 * path-walking is complete.
2177 static struct filename
*
2178 user_path_parent(int dfd
, const char __user
*path
, struct nameidata
*nd
)
2180 struct filename
*s
= getname(path
);
2186 error
= filename_lookup(dfd
, s
, LOOKUP_PARENT
, nd
);
2189 return ERR_PTR(error
);
2196 * It's inline, so penalty for filesystems that don't use sticky bit is
2199 static inline int check_sticky(struct inode
*dir
, struct inode
*inode
)
2201 kuid_t fsuid
= current_fsuid();
2203 if (!(dir
->i_mode
& S_ISVTX
))
2205 if (uid_eq(inode
->i_uid
, fsuid
))
2207 if (uid_eq(dir
->i_uid
, fsuid
))
2209 return !inode_capable(inode
, CAP_FOWNER
);
2213 * Check whether we can remove a link victim from directory dir, check
2214 * whether the type of victim is right.
2215 * 1. We can't do it if dir is read-only (done in permission())
2216 * 2. We should have write and exec permissions on dir
2217 * 3. We can't remove anything from append-only dir
2218 * 4. We can't do anything with immutable dir (done in permission())
2219 * 5. If the sticky bit on dir is set we should either
2220 * a. be owner of dir, or
2221 * b. be owner of victim, or
2222 * c. have CAP_FOWNER capability
2223 * 6. If the victim is append-only or immutable we can't do antyhing with
2224 * links pointing to it.
2225 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
2226 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
2227 * 9. We can't remove a root or mountpoint.
2228 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
2229 * nfs_async_unlink().
2231 static int may_delete(struct inode
*dir
,struct dentry
*victim
,int isdir
)
2235 if (!victim
->d_inode
)
2238 BUG_ON(victim
->d_parent
->d_inode
!= dir
);
2239 audit_inode_child(dir
, victim
, AUDIT_TYPE_CHILD_DELETE
);
2241 error
= inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
2246 if (check_sticky(dir
, victim
->d_inode
)||IS_APPEND(victim
->d_inode
)||
2247 IS_IMMUTABLE(victim
->d_inode
) || IS_SWAPFILE(victim
->d_inode
))
2250 if (!S_ISDIR(victim
->d_inode
->i_mode
))
2252 if (IS_ROOT(victim
))
2254 } else if (S_ISDIR(victim
->d_inode
->i_mode
))
2256 if (IS_DEADDIR(dir
))
2258 if (victim
->d_flags
& DCACHE_NFSFS_RENAMED
)
2263 /* Check whether we can create an object with dentry child in directory
2265 * 1. We can't do it if child already exists (open has special treatment for
2266 * this case, but since we are inlined it's OK)
2267 * 2. We can't do it if dir is read-only (done in permission())
2268 * 3. We should have write and exec permissions on dir
2269 * 4. We can't do it if dir is immutable (done in permission())
2271 static inline int may_create(struct inode
*dir
, struct dentry
*child
)
2275 if (IS_DEADDIR(dir
))
2277 return inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
2281 * p1 and p2 should be directories on the same fs.
2283 struct dentry
*lock_rename(struct dentry
*p1
, struct dentry
*p2
)
2288 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2292 mutex_lock(&p1
->d_inode
->i_sb
->s_vfs_rename_mutex
);
2294 p
= d_ancestor(p2
, p1
);
2296 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2297 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_CHILD
);
2301 p
= d_ancestor(p1
, p2
);
2303 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2304 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_CHILD
);
2308 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2309 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_CHILD
);
2313 void unlock_rename(struct dentry
*p1
, struct dentry
*p2
)
2315 mutex_unlock(&p1
->d_inode
->i_mutex
);
2317 mutex_unlock(&p2
->d_inode
->i_mutex
);
2318 mutex_unlock(&p1
->d_inode
->i_sb
->s_vfs_rename_mutex
);
2322 int vfs_create(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
,
2325 int error
= may_create(dir
, dentry
);
2329 if (!dir
->i_op
->create
)
2330 return -EACCES
; /* shouldn't it be ENOSYS? */
2333 error
= security_inode_create(dir
, dentry
, mode
);
2336 error
= dir
->i_op
->create(dir
, dentry
, mode
, want_excl
);
2338 fsnotify_create(dir
, dentry
);
2342 static int may_open(struct path
*path
, int acc_mode
, int flag
)
2344 struct dentry
*dentry
= path
->dentry
;
2345 struct inode
*inode
= dentry
->d_inode
;
2355 switch (inode
->i_mode
& S_IFMT
) {
2359 if (acc_mode
& MAY_WRITE
)
2364 if (path
->mnt
->mnt_flags
& MNT_NODEV
)
2373 error
= inode_permission(inode
, acc_mode
);
2378 * An append-only file must be opened in append mode for writing.
2380 if (IS_APPEND(inode
)) {
2381 if ((flag
& O_ACCMODE
) != O_RDONLY
&& !(flag
& O_APPEND
))
2387 /* O_NOATIME can only be set by the owner or superuser */
2388 if (flag
& O_NOATIME
&& !inode_owner_or_capable(inode
))
2394 static int handle_truncate(struct file
*filp
)
2396 struct path
*path
= &filp
->f_path
;
2397 struct inode
*inode
= path
->dentry
->d_inode
;
2398 int error
= get_write_access(inode
);
2402 * Refuse to truncate files with mandatory locks held on them.
2404 error
= locks_verify_locked(inode
);
2406 error
= security_path_truncate(path
);
2408 error
= do_truncate(path
->dentry
, 0,
2409 ATTR_MTIME
|ATTR_CTIME
|ATTR_OPEN
,
2412 put_write_access(inode
);
2416 static inline int open_to_namei_flags(int flag
)
2418 if ((flag
& O_ACCMODE
) == 3)
2423 static int may_o_create(struct path
*dir
, struct dentry
*dentry
, umode_t mode
)
2425 int error
= security_path_mknod(dir
, dentry
, mode
, 0);
2429 error
= inode_permission(dir
->dentry
->d_inode
, MAY_WRITE
| MAY_EXEC
);
2433 return security_inode_create(dir
->dentry
->d_inode
, dentry
, mode
);
2437 * Attempt to atomically look up, create and open a file from a negative
2440 * Returns 0 if successful. The file will have been created and attached to
2441 * @file by the filesystem calling finish_open().
2443 * Returns 1 if the file was looked up only or didn't need creating. The
2444 * caller will need to perform the open themselves. @path will have been
2445 * updated to point to the new dentry. This may be negative.
2447 * Returns an error code otherwise.
2449 static int atomic_open(struct nameidata
*nd
, struct dentry
*dentry
,
2450 struct path
*path
, struct file
*file
,
2451 const struct open_flags
*op
,
2452 bool got_write
, bool need_lookup
,
2455 struct inode
*dir
= nd
->path
.dentry
->d_inode
;
2456 unsigned open_flag
= open_to_namei_flags(op
->open_flag
);
2460 int create_error
= 0;
2461 struct dentry
*const DENTRY_NOT_SET
= (void *) -1UL;
2463 BUG_ON(dentry
->d_inode
);
2465 /* Don't create child dentry for a dead directory. */
2466 if (unlikely(IS_DEADDIR(dir
))) {
2472 if ((open_flag
& O_CREAT
) && !IS_POSIXACL(dir
))
2473 mode
&= ~current_umask();
2475 if ((open_flag
& (O_EXCL
| O_CREAT
)) == (O_EXCL
| O_CREAT
)) {
2476 open_flag
&= ~O_TRUNC
;
2477 *opened
|= FILE_CREATED
;
2481 * Checking write permission is tricky, bacuse we don't know if we are
2482 * going to actually need it: O_CREAT opens should work as long as the
2483 * file exists. But checking existence breaks atomicity. The trick is
2484 * to check access and if not granted clear O_CREAT from the flags.
2486 * Another problem is returing the "right" error value (e.g. for an
2487 * O_EXCL open we want to return EEXIST not EROFS).
2489 if (((open_flag
& (O_CREAT
| O_TRUNC
)) ||
2490 (open_flag
& O_ACCMODE
) != O_RDONLY
) && unlikely(!got_write
)) {
2491 if (!(open_flag
& O_CREAT
)) {
2493 * No O_CREATE -> atomicity not a requirement -> fall
2494 * back to lookup + open
2497 } else if (open_flag
& (O_EXCL
| O_TRUNC
)) {
2498 /* Fall back and fail with the right error */
2499 create_error
= -EROFS
;
2502 /* No side effects, safe to clear O_CREAT */
2503 create_error
= -EROFS
;
2504 open_flag
&= ~O_CREAT
;
2508 if (open_flag
& O_CREAT
) {
2509 error
= may_o_create(&nd
->path
, dentry
, mode
);
2511 create_error
= error
;
2512 if (open_flag
& O_EXCL
)
2514 open_flag
&= ~O_CREAT
;
2518 if (nd
->flags
& LOOKUP_DIRECTORY
)
2519 open_flag
|= O_DIRECTORY
;
2521 file
->f_path
.dentry
= DENTRY_NOT_SET
;
2522 file
->f_path
.mnt
= nd
->path
.mnt
;
2523 error
= dir
->i_op
->atomic_open(dir
, dentry
, file
, open_flag
, mode
,
2526 if (create_error
&& error
== -ENOENT
)
2527 error
= create_error
;
2531 acc_mode
= op
->acc_mode
;
2532 if (*opened
& FILE_CREATED
) {
2533 fsnotify_create(dir
, dentry
);
2534 acc_mode
= MAY_OPEN
;
2537 if (error
) { /* returned 1, that is */
2538 if (WARN_ON(file
->f_path
.dentry
== DENTRY_NOT_SET
)) {
2542 if (file
->f_path
.dentry
) {
2544 dentry
= file
->f_path
.dentry
;
2546 if (create_error
&& dentry
->d_inode
== NULL
) {
2547 error
= create_error
;
2554 * We didn't have the inode before the open, so check open permission
2557 error
= may_open(&file
->f_path
, acc_mode
, open_flag
);
2567 dentry
= lookup_real(dir
, dentry
, nd
->flags
);
2569 return PTR_ERR(dentry
);
2572 int open_flag
= op
->open_flag
;
2574 error
= create_error
;
2575 if ((open_flag
& O_EXCL
)) {
2576 if (!dentry
->d_inode
)
2578 } else if (!dentry
->d_inode
) {
2580 } else if ((open_flag
& O_TRUNC
) &&
2581 S_ISREG(dentry
->d_inode
->i_mode
)) {
2584 /* will fail later, go on to get the right error */
2588 path
->dentry
= dentry
;
2589 path
->mnt
= nd
->path
.mnt
;
2594 * Look up and maybe create and open the last component.
2596 * Must be called with i_mutex held on parent.
2598 * Returns 0 if the file was successfully atomically created (if necessary) and
2599 * opened. In this case the file will be returned attached to @file.
2601 * Returns 1 if the file was not completely opened at this time, though lookups
2602 * and creations will have been performed and the dentry returned in @path will
2603 * be positive upon return if O_CREAT was specified. If O_CREAT wasn't
2604 * specified then a negative dentry may be returned.
2606 * An error code is returned otherwise.
2608 * FILE_CREATE will be set in @*opened if the dentry was created and will be
2609 * cleared otherwise prior to returning.
2611 static int lookup_open(struct nameidata
*nd
, struct path
*path
,
2613 const struct open_flags
*op
,
2614 bool got_write
, int *opened
)
2616 struct dentry
*dir
= nd
->path
.dentry
;
2617 struct inode
*dir_inode
= dir
->d_inode
;
2618 struct dentry
*dentry
;
2622 *opened
&= ~FILE_CREATED
;
2623 dentry
= lookup_dcache(&nd
->last
, dir
, nd
->flags
, &need_lookup
);
2625 return PTR_ERR(dentry
);
2627 /* Cached positive dentry: will open in f_op->open */
2628 if (!need_lookup
&& dentry
->d_inode
)
2631 if ((nd
->flags
& LOOKUP_OPEN
) && dir_inode
->i_op
->atomic_open
) {
2632 return atomic_open(nd
, dentry
, path
, file
, op
, got_write
,
2633 need_lookup
, opened
);
2637 BUG_ON(dentry
->d_inode
);
2639 dentry
= lookup_real(dir_inode
, dentry
, nd
->flags
);
2641 return PTR_ERR(dentry
);
2644 /* Negative dentry, just create the file */
2645 if (!dentry
->d_inode
&& (op
->open_flag
& O_CREAT
)) {
2646 umode_t mode
= op
->mode
;
2647 if (!IS_POSIXACL(dir
->d_inode
))
2648 mode
&= ~current_umask();
2650 * This write is needed to ensure that a
2651 * rw->ro transition does not occur between
2652 * the time when the file is created and when
2653 * a permanent write count is taken through
2654 * the 'struct file' in finish_open().
2660 *opened
|= FILE_CREATED
;
2661 error
= security_path_mknod(&nd
->path
, dentry
, mode
, 0);
2664 error
= vfs_create(dir
->d_inode
, dentry
, mode
,
2665 nd
->flags
& LOOKUP_EXCL
);
2670 path
->dentry
= dentry
;
2671 path
->mnt
= nd
->path
.mnt
;
2680 * Handle the last step of open()
2682 static int do_last(struct nameidata
*nd
, struct path
*path
,
2683 struct file
*file
, const struct open_flags
*op
,
2684 int *opened
, struct filename
*name
)
2686 struct dentry
*dir
= nd
->path
.dentry
;
2687 int open_flag
= op
->open_flag
;
2688 bool will_truncate
= (open_flag
& O_TRUNC
) != 0;
2689 bool got_write
= false;
2690 int acc_mode
= op
->acc_mode
;
2691 struct inode
*inode
;
2692 bool symlink_ok
= false;
2693 struct path save_parent
= { .dentry
= NULL
, .mnt
= NULL
};
2694 bool retried
= false;
2697 nd
->flags
&= ~LOOKUP_PARENT
;
2698 nd
->flags
|= op
->intent
;
2700 switch (nd
->last_type
) {
2703 error
= handle_dots(nd
, nd
->last_type
);
2708 error
= complete_walk(nd
);
2711 audit_inode(name
, nd
->path
.dentry
, 0);
2712 if (open_flag
& O_CREAT
) {
2718 error
= complete_walk(nd
);
2721 audit_inode(name
, dir
, 0);
2725 if (!(open_flag
& O_CREAT
)) {
2726 if (nd
->last
.name
[nd
->last
.len
])
2727 nd
->flags
|= LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
;
2728 if (open_flag
& O_PATH
&& !(nd
->flags
& LOOKUP_FOLLOW
))
2730 /* we _can_ be in RCU mode here */
2731 error
= lookup_fast(nd
, &nd
->last
, path
, &inode
);
2738 BUG_ON(nd
->inode
!= dir
->d_inode
);
2740 /* create side of things */
2742 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED
2743 * has been cleared when we got to the last component we are
2746 error
= complete_walk(nd
);
2750 audit_inode(name
, dir
, 0);
2752 /* trailing slashes? */
2753 if (nd
->last
.name
[nd
->last
.len
])
2758 if (op
->open_flag
& (O_CREAT
| O_TRUNC
| O_WRONLY
| O_RDWR
)) {
2759 error
= mnt_want_write(nd
->path
.mnt
);
2763 * do _not_ fail yet - we might not need that or fail with
2764 * a different error; let lookup_open() decide; we'll be
2765 * dropping this one anyway.
2768 mutex_lock(&dir
->d_inode
->i_mutex
);
2769 error
= lookup_open(nd
, path
, file
, op
, got_write
, opened
);
2770 mutex_unlock(&dir
->d_inode
->i_mutex
);
2776 if ((*opened
& FILE_CREATED
) ||
2777 !S_ISREG(file
->f_path
.dentry
->d_inode
->i_mode
))
2778 will_truncate
= false;
2780 audit_inode(name
, file
->f_path
.dentry
, 0);
2784 if (*opened
& FILE_CREATED
) {
2785 /* Don't check for write permission, don't truncate */
2786 open_flag
&= ~O_TRUNC
;
2787 will_truncate
= false;
2788 acc_mode
= MAY_OPEN
;
2789 path_to_nameidata(path
, nd
);
2790 goto finish_open_created
;
2794 * create/update audit record if it already exists.
2796 if (path
->dentry
->d_inode
)
2797 audit_inode(name
, path
->dentry
, 0);
2800 * If atomic_open() acquired write access it is dropped now due to
2801 * possible mount and symlink following (this might be optimized away if
2805 mnt_drop_write(nd
->path
.mnt
);
2810 if ((open_flag
& (O_EXCL
| O_CREAT
)) == (O_EXCL
| O_CREAT
))
2813 error
= follow_managed(path
, nd
->flags
);
2818 nd
->flags
|= LOOKUP_JUMPED
;
2820 BUG_ON(nd
->flags
& LOOKUP_RCU
);
2821 inode
= path
->dentry
->d_inode
;
2823 /* we _can_ be in RCU mode here */
2826 path_to_nameidata(path
, nd
);
2830 if (should_follow_link(inode
, !symlink_ok
)) {
2831 if (nd
->flags
& LOOKUP_RCU
) {
2832 if (unlikely(unlazy_walk(nd
, path
->dentry
))) {
2837 BUG_ON(inode
!= path
->dentry
->d_inode
);
2841 if ((nd
->flags
& LOOKUP_RCU
) || nd
->path
.mnt
!= path
->mnt
) {
2842 path_to_nameidata(path
, nd
);
2844 save_parent
.dentry
= nd
->path
.dentry
;
2845 save_parent
.mnt
= mntget(path
->mnt
);
2846 nd
->path
.dentry
= path
->dentry
;
2850 /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
2851 error
= complete_walk(nd
);
2853 path_put(&save_parent
);
2857 if ((open_flag
& O_CREAT
) && S_ISDIR(nd
->inode
->i_mode
))
2860 if ((nd
->flags
& LOOKUP_DIRECTORY
) && !nd
->inode
->i_op
->lookup
)
2862 audit_inode(name
, nd
->path
.dentry
, 0);
2864 if (!S_ISREG(nd
->inode
->i_mode
))
2865 will_truncate
= false;
2867 if (will_truncate
) {
2868 error
= mnt_want_write(nd
->path
.mnt
);
2873 finish_open_created
:
2874 error
= may_open(&nd
->path
, acc_mode
, open_flag
);
2877 file
->f_path
.mnt
= nd
->path
.mnt
;
2878 error
= finish_open(file
, nd
->path
.dentry
, NULL
, opened
);
2880 if (error
== -EOPENSTALE
)
2885 error
= open_check_o_direct(file
);
2888 error
= ima_file_check(file
, op
->acc_mode
);
2892 if (will_truncate
) {
2893 error
= handle_truncate(file
);
2899 mnt_drop_write(nd
->path
.mnt
);
2900 path_put(&save_parent
);
2905 path_put_conditional(path
, nd
);
2912 /* If no saved parent or already retried then can't retry */
2913 if (!save_parent
.dentry
|| retried
)
2916 BUG_ON(save_parent
.dentry
!= dir
);
2917 path_put(&nd
->path
);
2918 nd
->path
= save_parent
;
2919 nd
->inode
= dir
->d_inode
;
2920 save_parent
.mnt
= NULL
;
2921 save_parent
.dentry
= NULL
;
2923 mnt_drop_write(nd
->path
.mnt
);
2930 static struct file
*path_openat(int dfd
, struct filename
*pathname
,
2931 struct nameidata
*nd
, const struct open_flags
*op
, int flags
)
2933 struct file
*base
= NULL
;
2939 file
= get_empty_filp();
2941 return ERR_PTR(-ENFILE
);
2943 file
->f_flags
= op
->open_flag
;
2945 error
= path_init(dfd
, pathname
->name
, flags
| LOOKUP_PARENT
, nd
, &base
);
2946 if (unlikely(error
))
2949 current
->total_link_count
= 0;
2950 error
= link_path_walk(pathname
->name
, nd
);
2951 if (unlikely(error
))
2954 error
= do_last(nd
, &path
, file
, op
, &opened
, pathname
);
2955 while (unlikely(error
> 0)) { /* trailing symlink */
2956 struct path link
= path
;
2958 if (!(nd
->flags
& LOOKUP_FOLLOW
)) {
2959 path_put_conditional(&path
, nd
);
2960 path_put(&nd
->path
);
2964 error
= may_follow_link(&link
, nd
);
2965 if (unlikely(error
))
2967 nd
->flags
|= LOOKUP_PARENT
;
2968 nd
->flags
&= ~(LOOKUP_OPEN
|LOOKUP_CREATE
|LOOKUP_EXCL
);
2969 error
= follow_link(&link
, nd
, &cookie
);
2970 if (unlikely(error
))
2972 error
= do_last(nd
, &path
, file
, op
, &opened
, pathname
);
2973 put_link(nd
, &link
, cookie
);
2976 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
))
2977 path_put(&nd
->root
);
2980 if (!(opened
& FILE_OPENED
)) {
2984 if (unlikely(error
)) {
2985 if (error
== -EOPENSTALE
) {
2986 if (flags
& LOOKUP_RCU
)
2991 file
= ERR_PTR(error
);
2996 struct file
*do_filp_open(int dfd
, struct filename
*pathname
,
2997 const struct open_flags
*op
, int flags
)
2999 struct nameidata nd
;
3002 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
| LOOKUP_RCU
);
3003 if (unlikely(filp
== ERR_PTR(-ECHILD
)))
3004 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
);
3005 if (unlikely(filp
== ERR_PTR(-ESTALE
)))
3006 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
| LOOKUP_REVAL
);
3010 struct file
*do_file_open_root(struct dentry
*dentry
, struct vfsmount
*mnt
,
3011 const char *name
, const struct open_flags
*op
, int flags
)
3013 struct nameidata nd
;
3015 struct filename filename
= { .name
= name
};
3018 nd
.root
.dentry
= dentry
;
3020 flags
|= LOOKUP_ROOT
;
3022 if (dentry
->d_inode
->i_op
->follow_link
&& op
->intent
& LOOKUP_OPEN
)
3023 return ERR_PTR(-ELOOP
);
3025 file
= path_openat(-1, &filename
, &nd
, op
, flags
| LOOKUP_RCU
);
3026 if (unlikely(file
== ERR_PTR(-ECHILD
)))
3027 file
= path_openat(-1, &filename
, &nd
, op
, flags
);
3028 if (unlikely(file
== ERR_PTR(-ESTALE
)))
3029 file
= path_openat(-1, &filename
, &nd
, op
, flags
| LOOKUP_REVAL
);
3033 struct dentry
*kern_path_create(int dfd
, const char *pathname
, struct path
*path
, int is_dir
)
3035 struct dentry
*dentry
= ERR_PTR(-EEXIST
);
3036 struct nameidata nd
;
3038 int error
= do_path_lookup(dfd
, pathname
, LOOKUP_PARENT
, &nd
);
3040 return ERR_PTR(error
);
3043 * Yucky last component or no last component at all?
3044 * (foo/., foo/.., /////)
3046 if (nd
.last_type
!= LAST_NORM
)
3048 nd
.flags
&= ~LOOKUP_PARENT
;
3049 nd
.flags
|= LOOKUP_CREATE
| LOOKUP_EXCL
;
3051 /* don't fail immediately if it's r/o, at least try to report other errors */
3052 err2
= mnt_want_write(nd
.path
.mnt
);
3054 * Do the final lookup.
3056 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
3057 dentry
= lookup_hash(&nd
);
3062 if (dentry
->d_inode
)
3065 * Special case - lookup gave negative, but... we had foo/bar/
3066 * From the vfs_mknod() POV we just have a negative dentry -
3067 * all is fine. Let's be bastards - you had / on the end, you've
3068 * been asking for (non-existent) directory. -ENOENT for you.
3070 if (unlikely(!is_dir
&& nd
.last
.name
[nd
.last
.len
])) {
3074 if (unlikely(err2
)) {
3082 dentry
= ERR_PTR(error
);
3084 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
3086 mnt_drop_write(nd
.path
.mnt
);
3091 EXPORT_SYMBOL(kern_path_create
);
3093 void done_path_create(struct path
*path
, struct dentry
*dentry
)
3096 mutex_unlock(&path
->dentry
->d_inode
->i_mutex
);
3097 mnt_drop_write(path
->mnt
);
3100 EXPORT_SYMBOL(done_path_create
);
3102 struct dentry
*user_path_create(int dfd
, const char __user
*pathname
, struct path
*path
, int is_dir
)
3104 struct filename
*tmp
= getname(pathname
);
3107 return ERR_CAST(tmp
);
3108 res
= kern_path_create(dfd
, tmp
->name
, path
, is_dir
);
3112 EXPORT_SYMBOL(user_path_create
);
3114 int vfs_mknod(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
, dev_t dev
)
3116 int error
= may_create(dir
, dentry
);
3121 if ((S_ISCHR(mode
) || S_ISBLK(mode
)) && !capable(CAP_MKNOD
))
3124 if (!dir
->i_op
->mknod
)
3127 error
= devcgroup_inode_mknod(mode
, dev
);
3131 error
= security_inode_mknod(dir
, dentry
, mode
, dev
);
3135 error
= dir
->i_op
->mknod(dir
, dentry
, mode
, dev
);
3137 fsnotify_create(dir
, dentry
);
3141 static int may_mknod(umode_t mode
)
3143 switch (mode
& S_IFMT
) {
3149 case 0: /* zero mode translates to S_IFREG */
3158 SYSCALL_DEFINE4(mknodat
, int, dfd
, const char __user
*, filename
, umode_t
, mode
,
3161 struct dentry
*dentry
;
3165 error
= may_mknod(mode
);
3169 dentry
= user_path_create(dfd
, filename
, &path
, 0);
3171 return PTR_ERR(dentry
);
3173 if (!IS_POSIXACL(path
.dentry
->d_inode
))
3174 mode
&= ~current_umask();
3175 error
= security_path_mknod(&path
, dentry
, mode
, dev
);
3178 switch (mode
& S_IFMT
) {
3179 case 0: case S_IFREG
:
3180 error
= vfs_create(path
.dentry
->d_inode
,dentry
,mode
,true);
3182 case S_IFCHR
: case S_IFBLK
:
3183 error
= vfs_mknod(path
.dentry
->d_inode
,dentry
,mode
,
3184 new_decode_dev(dev
));
3186 case S_IFIFO
: case S_IFSOCK
:
3187 error
= vfs_mknod(path
.dentry
->d_inode
,dentry
,mode
,0);
3191 done_path_create(&path
, dentry
);
3195 SYSCALL_DEFINE3(mknod
, const char __user
*, filename
, umode_t
, mode
, unsigned, dev
)
3197 return sys_mknodat(AT_FDCWD
, filename
, mode
, dev
);
3200 int vfs_mkdir(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
)
3202 int error
= may_create(dir
, dentry
);
3203 unsigned max_links
= dir
->i_sb
->s_max_links
;
3208 if (!dir
->i_op
->mkdir
)
3211 mode
&= (S_IRWXUGO
|S_ISVTX
);
3212 error
= security_inode_mkdir(dir
, dentry
, mode
);
3216 if (max_links
&& dir
->i_nlink
>= max_links
)
3219 error
= dir
->i_op
->mkdir(dir
, dentry
, mode
);
3221 fsnotify_mkdir(dir
, dentry
);
3225 SYSCALL_DEFINE3(mkdirat
, int, dfd
, const char __user
*, pathname
, umode_t
, mode
)
3227 struct dentry
*dentry
;
3231 dentry
= user_path_create(dfd
, pathname
, &path
, 1);
3233 return PTR_ERR(dentry
);
3235 if (!IS_POSIXACL(path
.dentry
->d_inode
))
3236 mode
&= ~current_umask();
3237 error
= security_path_mkdir(&path
, dentry
, mode
);
3239 error
= vfs_mkdir(path
.dentry
->d_inode
, dentry
, mode
);
3240 done_path_create(&path
, dentry
);
3244 SYSCALL_DEFINE2(mkdir
, const char __user
*, pathname
, umode_t
, mode
)
3246 return sys_mkdirat(AT_FDCWD
, pathname
, mode
);
3250 * The dentry_unhash() helper will try to drop the dentry early: we
3251 * should have a usage count of 1 if we're the only user of this
3252 * dentry, and if that is true (possibly after pruning the dcache),
3253 * then we drop the dentry now.
3255 * A low-level filesystem can, if it choses, legally
3258 * if (!d_unhashed(dentry))
3261 * if it cannot handle the case of removing a directory
3262 * that is still in use by something else..
3264 void dentry_unhash(struct dentry
*dentry
)
3266 shrink_dcache_parent(dentry
);
3267 spin_lock(&dentry
->d_lock
);
3268 if (dentry
->d_count
== 1)
3270 spin_unlock(&dentry
->d_lock
);
3273 int vfs_rmdir(struct inode
*dir
, struct dentry
*dentry
)
3275 int error
= may_delete(dir
, dentry
, 1);
3280 if (!dir
->i_op
->rmdir
)
3284 mutex_lock(&dentry
->d_inode
->i_mutex
);
3287 if (d_mountpoint(dentry
))
3290 error
= security_inode_rmdir(dir
, dentry
);
3294 shrink_dcache_parent(dentry
);
3295 error
= dir
->i_op
->rmdir(dir
, dentry
);
3299 dentry
->d_inode
->i_flags
|= S_DEAD
;
3303 mutex_unlock(&dentry
->d_inode
->i_mutex
);
3310 static long do_rmdir(int dfd
, const char __user
*pathname
)
3313 struct filename
*name
;
3314 struct dentry
*dentry
;
3315 struct nameidata nd
;
3317 name
= user_path_parent(dfd
, pathname
, &nd
);
3319 return PTR_ERR(name
);
3321 switch(nd
.last_type
) {
3333 nd
.flags
&= ~LOOKUP_PARENT
;
3334 error
= mnt_want_write(nd
.path
.mnt
);
3338 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
3339 dentry
= lookup_hash(&nd
);
3340 error
= PTR_ERR(dentry
);
3343 if (!dentry
->d_inode
) {
3347 error
= security_path_rmdir(&nd
.path
, dentry
);
3350 error
= vfs_rmdir(nd
.path
.dentry
->d_inode
, dentry
);
3354 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
3355 mnt_drop_write(nd
.path
.mnt
);
3362 SYSCALL_DEFINE1(rmdir
, const char __user
*, pathname
)
3364 return do_rmdir(AT_FDCWD
, pathname
);
3367 int vfs_unlink(struct inode
*dir
, struct dentry
*dentry
)
3369 int error
= may_delete(dir
, dentry
, 0);
3374 if (!dir
->i_op
->unlink
)
3377 mutex_lock(&dentry
->d_inode
->i_mutex
);
3378 if (d_mountpoint(dentry
))
3381 error
= security_inode_unlink(dir
, dentry
);
3383 error
= dir
->i_op
->unlink(dir
, dentry
);
3388 mutex_unlock(&dentry
->d_inode
->i_mutex
);
3390 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
3391 if (!error
&& !(dentry
->d_flags
& DCACHE_NFSFS_RENAMED
)) {
3392 fsnotify_link_count(dentry
->d_inode
);
3400 * Make sure that the actual truncation of the file will occur outside its
3401 * directory's i_mutex. Truncate can take a long time if there is a lot of
3402 * writeout happening, and we don't want to prevent access to the directory
3403 * while waiting on the I/O.
3405 static long do_unlinkat(int dfd
, const char __user
*pathname
)
3408 struct filename
*name
;
3409 struct dentry
*dentry
;
3410 struct nameidata nd
;
3411 struct inode
*inode
= NULL
;
3413 name
= user_path_parent(dfd
, pathname
, &nd
);
3415 return PTR_ERR(name
);
3418 if (nd
.last_type
!= LAST_NORM
)
3421 nd
.flags
&= ~LOOKUP_PARENT
;
3422 error
= mnt_want_write(nd
.path
.mnt
);
3426 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
3427 dentry
= lookup_hash(&nd
);
3428 error
= PTR_ERR(dentry
);
3429 if (!IS_ERR(dentry
)) {
3430 /* Why not before? Because we want correct error value */
3431 if (nd
.last
.name
[nd
.last
.len
])
3433 inode
= dentry
->d_inode
;
3437 error
= security_path_unlink(&nd
.path
, dentry
);
3440 error
= vfs_unlink(nd
.path
.dentry
->d_inode
, dentry
);
3444 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
3446 iput(inode
); /* truncate the inode here */
3447 mnt_drop_write(nd
.path
.mnt
);
3454 error
= !dentry
->d_inode
? -ENOENT
:
3455 S_ISDIR(dentry
->d_inode
->i_mode
) ? -EISDIR
: -ENOTDIR
;
3459 SYSCALL_DEFINE3(unlinkat
, int, dfd
, const char __user
*, pathname
, int, flag
)
3461 if ((flag
& ~AT_REMOVEDIR
) != 0)
3464 if (flag
& AT_REMOVEDIR
)
3465 return do_rmdir(dfd
, pathname
);
3467 return do_unlinkat(dfd
, pathname
);
3470 SYSCALL_DEFINE1(unlink
, const char __user
*, pathname
)
3472 return do_unlinkat(AT_FDCWD
, pathname
);
3475 int vfs_symlink(struct inode
*dir
, struct dentry
*dentry
, const char *oldname
)
3477 int error
= may_create(dir
, dentry
);
3482 if (!dir
->i_op
->symlink
)
3485 error
= security_inode_symlink(dir
, dentry
, oldname
);
3489 error
= dir
->i_op
->symlink(dir
, dentry
, oldname
);
3491 fsnotify_create(dir
, dentry
);
3495 SYSCALL_DEFINE3(symlinkat
, const char __user
*, oldname
,
3496 int, newdfd
, const char __user
*, newname
)
3499 struct filename
*from
;
3500 struct dentry
*dentry
;
3503 from
= getname(oldname
);
3505 return PTR_ERR(from
);
3507 dentry
= user_path_create(newdfd
, newname
, &path
, 0);
3508 error
= PTR_ERR(dentry
);
3512 error
= security_path_symlink(&path
, dentry
, from
->name
);
3514 error
= vfs_symlink(path
.dentry
->d_inode
, dentry
, from
->name
);
3515 done_path_create(&path
, dentry
);
3521 SYSCALL_DEFINE2(symlink
, const char __user
*, oldname
, const char __user
*, newname
)
3523 return sys_symlinkat(oldname
, AT_FDCWD
, newname
);
3526 int vfs_link(struct dentry
*old_dentry
, struct inode
*dir
, struct dentry
*new_dentry
)
3528 struct inode
*inode
= old_dentry
->d_inode
;
3529 unsigned max_links
= dir
->i_sb
->s_max_links
;
3535 error
= may_create(dir
, new_dentry
);
3539 if (dir
->i_sb
!= inode
->i_sb
)
3543 * A link to an append-only or immutable file cannot be created.
3545 if (IS_APPEND(inode
) || IS_IMMUTABLE(inode
))
3547 if (!dir
->i_op
->link
)
3549 if (S_ISDIR(inode
->i_mode
))
3552 error
= security_inode_link(old_dentry
, dir
, new_dentry
);
3556 mutex_lock(&inode
->i_mutex
);
3557 /* Make sure we don't allow creating hardlink to an unlinked file */
3558 if (inode
->i_nlink
== 0)
3560 else if (max_links
&& inode
->i_nlink
>= max_links
)
3563 error
= dir
->i_op
->link(old_dentry
, dir
, new_dentry
);
3564 mutex_unlock(&inode
->i_mutex
);
3566 fsnotify_link(dir
, inode
, new_dentry
);
3571 * Hardlinks are often used in delicate situations. We avoid
3572 * security-related surprises by not following symlinks on the
3575 * We don't follow them on the oldname either to be compatible
3576 * with linux 2.0, and to avoid hard-linking to directories
3577 * and other special files. --ADM
3579 SYSCALL_DEFINE5(linkat
, int, olddfd
, const char __user
*, oldname
,
3580 int, newdfd
, const char __user
*, newname
, int, flags
)
3582 struct dentry
*new_dentry
;
3583 struct path old_path
, new_path
;
3587 if ((flags
& ~(AT_SYMLINK_FOLLOW
| AT_EMPTY_PATH
)) != 0)
3590 * To use null names we require CAP_DAC_READ_SEARCH
3591 * This ensures that not everyone will be able to create
3592 * handlink using the passed filedescriptor.
3594 if (flags
& AT_EMPTY_PATH
) {
3595 if (!capable(CAP_DAC_READ_SEARCH
))
3600 if (flags
& AT_SYMLINK_FOLLOW
)
3601 how
|= LOOKUP_FOLLOW
;
3603 error
= user_path_at(olddfd
, oldname
, how
, &old_path
);
3607 new_dentry
= user_path_create(newdfd
, newname
, &new_path
, 0);
3608 error
= PTR_ERR(new_dentry
);
3609 if (IS_ERR(new_dentry
))
3613 if (old_path
.mnt
!= new_path
.mnt
)
3615 error
= may_linkat(&old_path
);
3616 if (unlikely(error
))
3618 error
= security_path_link(old_path
.dentry
, &new_path
, new_dentry
);
3621 error
= vfs_link(old_path
.dentry
, new_path
.dentry
->d_inode
, new_dentry
);
3623 done_path_create(&new_path
, new_dentry
);
3625 path_put(&old_path
);
3630 SYSCALL_DEFINE2(link
, const char __user
*, oldname
, const char __user
*, newname
)
3632 return sys_linkat(AT_FDCWD
, oldname
, AT_FDCWD
, newname
, 0);
3636 * The worst of all namespace operations - renaming directory. "Perverted"
3637 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
3639 * a) we can get into loop creation. Check is done in is_subdir().
3640 * b) race potential - two innocent renames can create a loop together.
3641 * That's where 4.4 screws up. Current fix: serialization on
3642 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
3644 * c) we have to lock _three_ objects - parents and victim (if it exists).
3645 * And that - after we got ->i_mutex on parents (until then we don't know
3646 * whether the target exists). Solution: try to be smart with locking
3647 * order for inodes. We rely on the fact that tree topology may change
3648 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
3649 * move will be locked. Thus we can rank directories by the tree
3650 * (ancestors first) and rank all non-directories after them.
3651 * That works since everybody except rename does "lock parent, lookup,
3652 * lock child" and rename is under ->s_vfs_rename_mutex.
3653 * HOWEVER, it relies on the assumption that any object with ->lookup()
3654 * has no more than 1 dentry. If "hybrid" objects will ever appear,
3655 * we'd better make sure that there's no link(2) for them.
3656 * d) conversion from fhandle to dentry may come in the wrong moment - when
3657 * we are removing the target. Solution: we will have to grab ->i_mutex
3658 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
3659 * ->i_mutex on parents, which works but leads to some truly excessive
3662 static int vfs_rename_dir(struct inode
*old_dir
, struct dentry
*old_dentry
,
3663 struct inode
*new_dir
, struct dentry
*new_dentry
)
3666 struct inode
*target
= new_dentry
->d_inode
;
3667 unsigned max_links
= new_dir
->i_sb
->s_max_links
;
3670 * If we are going to change the parent - check write permissions,
3671 * we'll need to flip '..'.
3673 if (new_dir
!= old_dir
) {
3674 error
= inode_permission(old_dentry
->d_inode
, MAY_WRITE
);
3679 error
= security_inode_rename(old_dir
, old_dentry
, new_dir
, new_dentry
);
3685 mutex_lock(&target
->i_mutex
);
3688 if (d_mountpoint(old_dentry
) || d_mountpoint(new_dentry
))
3692 if (max_links
&& !target
&& new_dir
!= old_dir
&&
3693 new_dir
->i_nlink
>= max_links
)
3697 shrink_dcache_parent(new_dentry
);
3698 error
= old_dir
->i_op
->rename(old_dir
, old_dentry
, new_dir
, new_dentry
);
3703 target
->i_flags
|= S_DEAD
;
3704 dont_mount(new_dentry
);
3708 mutex_unlock(&target
->i_mutex
);
3711 if (!(old_dir
->i_sb
->s_type
->fs_flags
& FS_RENAME_DOES_D_MOVE
))
3712 d_move(old_dentry
,new_dentry
);
3716 static int vfs_rename_other(struct inode
*old_dir
, struct dentry
*old_dentry
,
3717 struct inode
*new_dir
, struct dentry
*new_dentry
)
3719 struct inode
*target
= new_dentry
->d_inode
;
3722 error
= security_inode_rename(old_dir
, old_dentry
, new_dir
, new_dentry
);
3728 mutex_lock(&target
->i_mutex
);
3731 if (d_mountpoint(old_dentry
)||d_mountpoint(new_dentry
))
3734 error
= old_dir
->i_op
->rename(old_dir
, old_dentry
, new_dir
, new_dentry
);
3739 dont_mount(new_dentry
);
3740 if (!(old_dir
->i_sb
->s_type
->fs_flags
& FS_RENAME_DOES_D_MOVE
))
3741 d_move(old_dentry
, new_dentry
);
3744 mutex_unlock(&target
->i_mutex
);
3749 int vfs_rename(struct inode
*old_dir
, struct dentry
*old_dentry
,
3750 struct inode
*new_dir
, struct dentry
*new_dentry
)
3753 int is_dir
= S_ISDIR(old_dentry
->d_inode
->i_mode
);
3754 const unsigned char *old_name
;
3756 if (old_dentry
->d_inode
== new_dentry
->d_inode
)
3759 error
= may_delete(old_dir
, old_dentry
, is_dir
);
3763 if (!new_dentry
->d_inode
)
3764 error
= may_create(new_dir
, new_dentry
);
3766 error
= may_delete(new_dir
, new_dentry
, is_dir
);
3770 if (!old_dir
->i_op
->rename
)
3773 old_name
= fsnotify_oldname_init(old_dentry
->d_name
.name
);
3776 error
= vfs_rename_dir(old_dir
,old_dentry
,new_dir
,new_dentry
);
3778 error
= vfs_rename_other(old_dir
,old_dentry
,new_dir
,new_dentry
);
3780 fsnotify_move(old_dir
, new_dir
, old_name
, is_dir
,
3781 new_dentry
->d_inode
, old_dentry
);
3782 fsnotify_oldname_free(old_name
);
3787 SYSCALL_DEFINE4(renameat
, int, olddfd
, const char __user
*, oldname
,
3788 int, newdfd
, const char __user
*, newname
)
3790 struct dentry
*old_dir
, *new_dir
;
3791 struct dentry
*old_dentry
, *new_dentry
;
3792 struct dentry
*trap
;
3793 struct nameidata oldnd
, newnd
;
3794 struct filename
*from
;
3795 struct filename
*to
;
3798 from
= user_path_parent(olddfd
, oldname
, &oldnd
);
3800 error
= PTR_ERR(from
);
3804 to
= user_path_parent(newdfd
, newname
, &newnd
);
3806 error
= PTR_ERR(to
);
3811 if (oldnd
.path
.mnt
!= newnd
.path
.mnt
)
3814 old_dir
= oldnd
.path
.dentry
;
3816 if (oldnd
.last_type
!= LAST_NORM
)
3819 new_dir
= newnd
.path
.dentry
;
3820 if (newnd
.last_type
!= LAST_NORM
)
3823 error
= mnt_want_write(oldnd
.path
.mnt
);
3827 oldnd
.flags
&= ~LOOKUP_PARENT
;
3828 newnd
.flags
&= ~LOOKUP_PARENT
;
3829 newnd
.flags
|= LOOKUP_RENAME_TARGET
;
3831 trap
= lock_rename(new_dir
, old_dir
);
3833 old_dentry
= lookup_hash(&oldnd
);
3834 error
= PTR_ERR(old_dentry
);
3835 if (IS_ERR(old_dentry
))
3837 /* source must exist */
3839 if (!old_dentry
->d_inode
)
3841 /* unless the source is a directory trailing slashes give -ENOTDIR */
3842 if (!S_ISDIR(old_dentry
->d_inode
->i_mode
)) {
3844 if (oldnd
.last
.name
[oldnd
.last
.len
])
3846 if (newnd
.last
.name
[newnd
.last
.len
])
3849 /* source should not be ancestor of target */
3851 if (old_dentry
== trap
)
3853 new_dentry
= lookup_hash(&newnd
);
3854 error
= PTR_ERR(new_dentry
);
3855 if (IS_ERR(new_dentry
))
3857 /* target should not be an ancestor of source */
3859 if (new_dentry
== trap
)
3862 error
= security_path_rename(&oldnd
.path
, old_dentry
,
3863 &newnd
.path
, new_dentry
);
3866 error
= vfs_rename(old_dir
->d_inode
, old_dentry
,
3867 new_dir
->d_inode
, new_dentry
);
3873 unlock_rename(new_dir
, old_dir
);
3874 mnt_drop_write(oldnd
.path
.mnt
);
3876 path_put(&newnd
.path
);
3879 path_put(&oldnd
.path
);
3885 SYSCALL_DEFINE2(rename
, const char __user
*, oldname
, const char __user
*, newname
)
3887 return sys_renameat(AT_FDCWD
, oldname
, AT_FDCWD
, newname
);
3890 int vfs_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
, const char *link
)
3894 len
= PTR_ERR(link
);
3899 if (len
> (unsigned) buflen
)
3901 if (copy_to_user(buffer
, link
, len
))
3908 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
3909 * have ->follow_link() touching nd only in nd_set_link(). Using (or not
3910 * using) it for any given inode is up to filesystem.
3912 int generic_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
)
3914 struct nameidata nd
;
3919 cookie
= dentry
->d_inode
->i_op
->follow_link(dentry
, &nd
);
3921 return PTR_ERR(cookie
);
3923 res
= vfs_readlink(dentry
, buffer
, buflen
, nd_get_link(&nd
));
3924 if (dentry
->d_inode
->i_op
->put_link
)
3925 dentry
->d_inode
->i_op
->put_link(dentry
, &nd
, cookie
);
3929 int vfs_follow_link(struct nameidata
*nd
, const char *link
)
3931 return __vfs_follow_link(nd
, link
);
3934 /* get the link contents into pagecache */
3935 static char *page_getlink(struct dentry
* dentry
, struct page
**ppage
)
3939 struct address_space
*mapping
= dentry
->d_inode
->i_mapping
;
3940 page
= read_mapping_page(mapping
, 0, NULL
);
3945 nd_terminate_link(kaddr
, dentry
->d_inode
->i_size
, PAGE_SIZE
- 1);
3949 int page_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
)
3951 struct page
*page
= NULL
;
3952 char *s
= page_getlink(dentry
, &page
);
3953 int res
= vfs_readlink(dentry
,buffer
,buflen
,s
);
3956 page_cache_release(page
);
3961 void *page_follow_link_light(struct dentry
*dentry
, struct nameidata
*nd
)
3963 struct page
*page
= NULL
;
3964 nd_set_link(nd
, page_getlink(dentry
, &page
));
3968 void page_put_link(struct dentry
*dentry
, struct nameidata
*nd
, void *cookie
)
3970 struct page
*page
= cookie
;
3974 page_cache_release(page
);
3979 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
3981 int __page_symlink(struct inode
*inode
, const char *symname
, int len
, int nofs
)
3983 struct address_space
*mapping
= inode
->i_mapping
;
3988 unsigned int flags
= AOP_FLAG_UNINTERRUPTIBLE
;
3990 flags
|= AOP_FLAG_NOFS
;
3993 err
= pagecache_write_begin(NULL
, mapping
, 0, len
-1,
3994 flags
, &page
, &fsdata
);
3998 kaddr
= kmap_atomic(page
);
3999 memcpy(kaddr
, symname
, len
-1);
4000 kunmap_atomic(kaddr
);
4002 err
= pagecache_write_end(NULL
, mapping
, 0, len
-1, len
-1,
4009 mark_inode_dirty(inode
);
4015 int page_symlink(struct inode
*inode
, const char *symname
, int len
)
4017 return __page_symlink(inode
, symname
, len
,
4018 !(mapping_gfp_mask(inode
->i_mapping
) & __GFP_FS
));
4021 const struct inode_operations page_symlink_inode_operations
= {
4022 .readlink
= generic_readlink
,
4023 .follow_link
= page_follow_link_light
,
4024 .put_link
= page_put_link
,
4027 EXPORT_SYMBOL(user_path_at
);
4028 EXPORT_SYMBOL(follow_down_one
);
4029 EXPORT_SYMBOL(follow_down
);
4030 EXPORT_SYMBOL(follow_up
);
4031 EXPORT_SYMBOL(get_write_access
); /* nfsd */
4032 EXPORT_SYMBOL(lock_rename
);
4033 EXPORT_SYMBOL(lookup_one_len
);
4034 EXPORT_SYMBOL(page_follow_link_light
);
4035 EXPORT_SYMBOL(page_put_link
);
4036 EXPORT_SYMBOL(page_readlink
);
4037 EXPORT_SYMBOL(__page_symlink
);
4038 EXPORT_SYMBOL(page_symlink
);
4039 EXPORT_SYMBOL(page_symlink_inode_operations
);
4040 EXPORT_SYMBOL(kern_path
);
4041 EXPORT_SYMBOL(vfs_path_lookup
);
4042 EXPORT_SYMBOL(inode_permission
);
4043 EXPORT_SYMBOL(unlock_rename
);
4044 EXPORT_SYMBOL(vfs_create
);
4045 EXPORT_SYMBOL(vfs_follow_link
);
4046 EXPORT_SYMBOL(vfs_link
);
4047 EXPORT_SYMBOL(vfs_mkdir
);
4048 EXPORT_SYMBOL(vfs_mknod
);
4049 EXPORT_SYMBOL(generic_permission
);
4050 EXPORT_SYMBOL(vfs_readlink
);
4051 EXPORT_SYMBOL(vfs_rename
);
4052 EXPORT_SYMBOL(vfs_rmdir
);
4053 EXPORT_SYMBOL(vfs_symlink
);
4054 EXPORT_SYMBOL(vfs_unlink
);
4055 EXPORT_SYMBOL(dentry_unhash
);
4056 EXPORT_SYMBOL(generic_readlink
);