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 <linux/hash.h>
38 #include <asm/uaccess.h>
43 /* [Feb-1997 T. Schoebel-Theuer]
44 * Fundamental changes in the pathname lookup mechanisms (namei)
45 * were necessary because of omirr. The reason is that omirr needs
46 * to know the _real_ pathname, not the user-supplied one, in case
47 * of symlinks (and also when transname replacements occur).
49 * The new code replaces the old recursive symlink resolution with
50 * an iterative one (in case of non-nested symlink chains). It does
51 * this with calls to <fs>_follow_link().
52 * As a side effect, dir_namei(), _namei() and follow_link() are now
53 * replaced with a single function lookup_dentry() that can handle all
54 * the special cases of the former code.
56 * With the new dcache, the pathname is stored at each inode, at least as
57 * long as the refcount of the inode is positive. As a side effect, the
58 * size of the dcache depends on the inode cache and thus is dynamic.
60 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
61 * resolution to correspond with current state of the code.
63 * Note that the symlink resolution is not *completely* iterative.
64 * There is still a significant amount of tail- and mid- recursion in
65 * the algorithm. Also, note that <fs>_readlink() is not used in
66 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
67 * may return different results than <fs>_follow_link(). Many virtual
68 * filesystems (including /proc) exhibit this behavior.
71 /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
72 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
73 * and the name already exists in form of a symlink, try to create the new
74 * name indicated by the symlink. The old code always complained that the
75 * name already exists, due to not following the symlink even if its target
76 * is nonexistent. The new semantics affects also mknod() and link() when
77 * the name is a symlink pointing to a non-existent name.
79 * I don't know which semantics is the right one, since I have no access
80 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
81 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
82 * "old" one. Personally, I think the new semantics is much more logical.
83 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
84 * file does succeed in both HP-UX and SunOs, but not in Solaris
85 * and in the old Linux semantics.
88 /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
89 * semantics. See the comments in "open_namei" and "do_link" below.
91 * [10-Sep-98 Alan Modra] Another symlink change.
94 /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
95 * inside the path - always follow.
96 * in the last component in creation/removal/renaming - never follow.
97 * if LOOKUP_FOLLOW passed - follow.
98 * if the pathname has trailing slashes - follow.
99 * otherwise - don't follow.
100 * (applied in that order).
102 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
103 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
104 * During the 2.4 we need to fix the userland stuff depending on it -
105 * hopefully we will be able to get rid of that wart in 2.5. So far only
106 * XEmacs seems to be relying on it...
109 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
110 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
111 * any extra contention...
114 /* In order to reduce some races, while at the same time doing additional
115 * checking and hopefully speeding things up, we copy filenames to the
116 * kernel data space before using them..
118 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
119 * PATH_MAX includes the nul terminator --RR.
122 #define EMBEDDED_NAME_MAX (PATH_MAX - offsetof(struct filename, iname))
125 getname_flags(const char __user
*filename
, int flags
, int *empty
)
127 struct filename
*result
;
131 result
= audit_reusename(filename
);
135 result
= __getname();
136 if (unlikely(!result
))
137 return ERR_PTR(-ENOMEM
);
140 * First, try to embed the struct filename inside the names_cache
143 kname
= (char *)result
->iname
;
144 result
->name
= kname
;
146 len
= strncpy_from_user(kname
, filename
, EMBEDDED_NAME_MAX
);
147 if (unlikely(len
< 0)) {
153 * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a
154 * separate struct filename so we can dedicate the entire
155 * names_cache allocation for the pathname, and re-do the copy from
158 if (unlikely(len
== EMBEDDED_NAME_MAX
)) {
159 const size_t size
= offsetof(struct filename
, iname
[1]);
160 kname
= (char *)result
;
163 * size is chosen that way we to guarantee that
164 * result->iname[0] is within the same object and that
165 * kname can't be equal to result->iname, no matter what.
167 result
= kzalloc(size
, GFP_KERNEL
);
168 if (unlikely(!result
)) {
170 return ERR_PTR(-ENOMEM
);
172 result
->name
= kname
;
173 len
= strncpy_from_user(kname
, filename
, PATH_MAX
);
174 if (unlikely(len
< 0)) {
179 if (unlikely(len
== PATH_MAX
)) {
182 return ERR_PTR(-ENAMETOOLONG
);
187 /* The empty path is special. */
188 if (unlikely(!len
)) {
191 if (!(flags
& LOOKUP_EMPTY
)) {
193 return ERR_PTR(-ENOENT
);
197 result
->uptr
= filename
;
198 result
->aname
= NULL
;
199 audit_getname(result
);
204 getname(const char __user
* filename
)
206 return getname_flags(filename
, 0, NULL
);
210 getname_kernel(const char * filename
)
212 struct filename
*result
;
213 int len
= strlen(filename
) + 1;
215 result
= __getname();
216 if (unlikely(!result
))
217 return ERR_PTR(-ENOMEM
);
219 if (len
<= EMBEDDED_NAME_MAX
) {
220 result
->name
= (char *)result
->iname
;
221 } else if (len
<= PATH_MAX
) {
222 struct filename
*tmp
;
224 tmp
= kmalloc(sizeof(*tmp
), GFP_KERNEL
);
225 if (unlikely(!tmp
)) {
227 return ERR_PTR(-ENOMEM
);
229 tmp
->name
= (char *)result
;
233 return ERR_PTR(-ENAMETOOLONG
);
235 memcpy((char *)result
->name
, filename
, len
);
237 result
->aname
= NULL
;
239 audit_getname(result
);
244 void putname(struct filename
*name
)
246 BUG_ON(name
->refcnt
<= 0);
248 if (--name
->refcnt
> 0)
251 if (name
->name
!= name
->iname
) {
252 __putname(name
->name
);
258 static int check_acl(struct inode
*inode
, int mask
)
260 #ifdef CONFIG_FS_POSIX_ACL
261 struct posix_acl
*acl
;
263 if (mask
& MAY_NOT_BLOCK
) {
264 acl
= get_cached_acl_rcu(inode
, ACL_TYPE_ACCESS
);
267 /* no ->get_acl() calls in RCU mode... */
268 if (acl
== ACL_NOT_CACHED
)
270 return posix_acl_permission(inode
, acl
, mask
& ~MAY_NOT_BLOCK
);
273 acl
= get_acl(inode
, ACL_TYPE_ACCESS
);
277 int error
= posix_acl_permission(inode
, acl
, mask
);
278 posix_acl_release(acl
);
287 * This does the basic permission checking
289 static int acl_permission_check(struct inode
*inode
, int mask
)
291 unsigned int mode
= inode
->i_mode
;
293 if (likely(uid_eq(current_fsuid(), inode
->i_uid
)))
296 if (IS_POSIXACL(inode
) && (mode
& S_IRWXG
)) {
297 int error
= check_acl(inode
, mask
);
298 if (error
!= -EAGAIN
)
302 if (in_group_p(inode
->i_gid
))
307 * If the DACs are ok we don't need any capability check.
309 if ((mask
& ~mode
& (MAY_READ
| MAY_WRITE
| MAY_EXEC
)) == 0)
315 * generic_permission - check for access rights on a Posix-like filesystem
316 * @inode: inode to check access rights for
317 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
319 * Used to check for read/write/execute permissions on a file.
320 * We use "fsuid" for this, letting us set arbitrary permissions
321 * for filesystem access without changing the "normal" uids which
322 * are used for other things.
324 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
325 * request cannot be satisfied (eg. requires blocking or too much complexity).
326 * It would then be called again in ref-walk mode.
328 int generic_permission(struct inode
*inode
, int mask
)
333 * Do the basic permission checks.
335 ret
= acl_permission_check(inode
, mask
);
339 if (S_ISDIR(inode
->i_mode
)) {
340 /* DACs are overridable for directories */
341 if (capable_wrt_inode_uidgid(inode
, CAP_DAC_OVERRIDE
))
343 if (!(mask
& MAY_WRITE
))
344 if (capable_wrt_inode_uidgid(inode
,
345 CAP_DAC_READ_SEARCH
))
350 * Read/write DACs are always overridable.
351 * Executable DACs are overridable when there is
352 * at least one exec bit set.
354 if (!(mask
& MAY_EXEC
) || (inode
->i_mode
& S_IXUGO
))
355 if (capable_wrt_inode_uidgid(inode
, CAP_DAC_OVERRIDE
))
359 * Searching includes executable on directories, else just read.
361 mask
&= MAY_READ
| MAY_WRITE
| MAY_EXEC
;
362 if (mask
== MAY_READ
)
363 if (capable_wrt_inode_uidgid(inode
, CAP_DAC_READ_SEARCH
))
368 EXPORT_SYMBOL(generic_permission
);
371 * We _really_ want to just do "generic_permission()" without
372 * even looking at the inode->i_op values. So we keep a cache
373 * flag in inode->i_opflags, that says "this has not special
374 * permission function, use the fast case".
376 static inline int do_inode_permission(struct inode
*inode
, int mask
)
378 if (unlikely(!(inode
->i_opflags
& IOP_FASTPERM
))) {
379 if (likely(inode
->i_op
->permission
))
380 return inode
->i_op
->permission(inode
, mask
);
382 /* This gets set once for the inode lifetime */
383 spin_lock(&inode
->i_lock
);
384 inode
->i_opflags
|= IOP_FASTPERM
;
385 spin_unlock(&inode
->i_lock
);
387 return generic_permission(inode
, mask
);
391 * __inode_permission - Check for access rights to a given inode
392 * @inode: Inode to check permission on
393 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
395 * Check for read/write/execute permissions on an inode.
397 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
399 * This does not check for a read-only file system. You probably want
400 * inode_permission().
402 int __inode_permission(struct inode
*inode
, int mask
)
406 if (unlikely(mask
& MAY_WRITE
)) {
408 * Nobody gets write access to an immutable file.
410 if (IS_IMMUTABLE(inode
))
414 retval
= do_inode_permission(inode
, mask
);
418 retval
= devcgroup_inode_permission(inode
, mask
);
422 return security_inode_permission(inode
, mask
);
424 EXPORT_SYMBOL(__inode_permission
);
427 * sb_permission - Check superblock-level permissions
428 * @sb: Superblock of inode to check permission on
429 * @inode: Inode to check permission on
430 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
432 * Separate out file-system wide checks from inode-specific permission checks.
434 static int sb_permission(struct super_block
*sb
, struct inode
*inode
, int mask
)
436 if (unlikely(mask
& MAY_WRITE
)) {
437 umode_t mode
= inode
->i_mode
;
439 /* Nobody gets write access to a read-only fs. */
440 if ((sb
->s_flags
& MS_RDONLY
) &&
441 (S_ISREG(mode
) || S_ISDIR(mode
) || S_ISLNK(mode
)))
448 * inode_permission - Check for access rights to a given inode
449 * @inode: Inode to check permission on
450 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
452 * Check for read/write/execute permissions on an inode. We use fs[ug]id for
453 * this, letting us set arbitrary permissions for filesystem access without
454 * changing the "normal" UIDs which are used for other things.
456 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
458 int inode_permission(struct inode
*inode
, int mask
)
462 retval
= sb_permission(inode
->i_sb
, inode
, mask
);
465 return __inode_permission(inode
, mask
);
467 EXPORT_SYMBOL(inode_permission
);
470 * path_get - get a reference to a path
471 * @path: path to get the reference to
473 * Given a path increment the reference count to the dentry and the vfsmount.
475 void path_get(const struct path
*path
)
480 EXPORT_SYMBOL(path_get
);
483 * path_put - put a reference to a path
484 * @path: path to put the reference to
486 * Given a path decrement the reference count to the dentry and the vfsmount.
488 void path_put(const struct path
*path
)
493 EXPORT_SYMBOL(path_put
);
502 struct inode
*inode
; /* path.dentry.d_inode */
511 * Path walking has 2 modes, rcu-walk and ref-walk (see
512 * Documentation/filesystems/path-lookup.txt). In situations when we can't
513 * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
514 * normal reference counts on dentries and vfsmounts to transition to rcu-walk
515 * mode. Refcounts are grabbed at the last known good point before rcu-walk
516 * got stuck, so ref-walk may continue from there. If this is not successful
517 * (eg. a seqcount has changed), then failure is returned and it's up to caller
518 * to restart the path walk from the beginning in ref-walk mode.
522 * unlazy_walk - try to switch to ref-walk mode.
523 * @nd: nameidata pathwalk data
524 * @dentry: child of nd->path.dentry or NULL
525 * Returns: 0 on success, -ECHILD on failure
527 * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry
528 * for ref-walk mode. @dentry must be a path found by a do_lookup call on
529 * @nd or NULL. Must be called from rcu-walk context.
531 static int unlazy_walk(struct nameidata
*nd
, struct dentry
*dentry
)
533 struct fs_struct
*fs
= current
->fs
;
534 struct dentry
*parent
= nd
->path
.dentry
;
536 BUG_ON(!(nd
->flags
& LOOKUP_RCU
));
539 * After legitimizing the bastards, terminate_walk()
540 * will do the right thing for non-RCU mode, and all our
541 * subsequent exit cases should rcu_read_unlock()
542 * before returning. Do vfsmount first; if dentry
543 * can't be legitimized, just set nd->path.dentry to NULL
544 * and rely on dput(NULL) being a no-op.
546 if (!legitimize_mnt(nd
->path
.mnt
, nd
->m_seq
))
548 nd
->flags
&= ~LOOKUP_RCU
;
550 if (!lockref_get_not_dead(&parent
->d_lockref
)) {
551 nd
->path
.dentry
= NULL
;
556 * For a negative lookup, the lookup sequence point is the parents
557 * sequence point, and it only needs to revalidate the parent dentry.
559 * For a positive lookup, we need to move both the parent and the
560 * dentry from the RCU domain to be properly refcounted. And the
561 * sequence number in the dentry validates *both* dentry counters,
562 * since we checked the sequence number of the parent after we got
563 * the child sequence number. So we know the parent must still
564 * be valid if the child sequence number is still valid.
567 if (read_seqcount_retry(&parent
->d_seq
, nd
->seq
))
569 BUG_ON(nd
->inode
!= parent
->d_inode
);
571 if (!lockref_get_not_dead(&dentry
->d_lockref
))
573 if (read_seqcount_retry(&dentry
->d_seq
, nd
->seq
))
578 * Sequence counts matched. Now make sure that the root is
579 * still valid and get it if required.
581 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
)) {
582 spin_lock(&fs
->lock
);
583 if (nd
->root
.mnt
!= fs
->root
.mnt
|| nd
->root
.dentry
!= fs
->root
.dentry
)
584 goto unlock_and_drop_dentry
;
586 spin_unlock(&fs
->lock
);
592 unlock_and_drop_dentry
:
593 spin_unlock(&fs
->lock
);
601 if (!(nd
->flags
& LOOKUP_ROOT
))
606 static inline int d_revalidate(struct dentry
*dentry
, unsigned int flags
)
608 return dentry
->d_op
->d_revalidate(dentry
, flags
);
612 * complete_walk - successful completion of path walk
613 * @nd: pointer nameidata
615 * If we had been in RCU mode, drop out of it and legitimize nd->path.
616 * Revalidate the final result, unless we'd already done that during
617 * the path walk or the filesystem doesn't ask for it. Return 0 on
618 * success, -error on failure. In case of failure caller does not
619 * need to drop nd->path.
621 static int complete_walk(struct nameidata
*nd
)
623 struct dentry
*dentry
= nd
->path
.dentry
;
626 if (nd
->flags
& LOOKUP_RCU
) {
627 nd
->flags
&= ~LOOKUP_RCU
;
628 if (!(nd
->flags
& LOOKUP_ROOT
))
631 if (!legitimize_mnt(nd
->path
.mnt
, nd
->m_seq
)) {
635 if (unlikely(!lockref_get_not_dead(&dentry
->d_lockref
))) {
637 mntput(nd
->path
.mnt
);
640 if (read_seqcount_retry(&dentry
->d_seq
, nd
->seq
)) {
643 mntput(nd
->path
.mnt
);
649 if (likely(!(nd
->flags
& LOOKUP_JUMPED
)))
652 if (likely(!(dentry
->d_flags
& DCACHE_OP_WEAK_REVALIDATE
)))
655 status
= dentry
->d_op
->d_weak_revalidate(dentry
, nd
->flags
);
666 static __always_inline
void set_root(struct nameidata
*nd
)
668 get_fs_root(current
->fs
, &nd
->root
);
671 static __always_inline
unsigned set_root_rcu(struct nameidata
*nd
)
673 struct fs_struct
*fs
= current
->fs
;
677 seq
= read_seqcount_begin(&fs
->seq
);
679 res
= __read_seqcount_begin(&nd
->root
.dentry
->d_seq
);
680 } while (read_seqcount_retry(&fs
->seq
, seq
));
684 static void path_put_conditional(struct path
*path
, struct nameidata
*nd
)
687 if (path
->mnt
!= nd
->path
.mnt
)
691 static inline void path_to_nameidata(const struct path
*path
,
692 struct nameidata
*nd
)
694 if (!(nd
->flags
& LOOKUP_RCU
)) {
695 dput(nd
->path
.dentry
);
696 if (nd
->path
.mnt
!= path
->mnt
)
697 mntput(nd
->path
.mnt
);
699 nd
->path
.mnt
= path
->mnt
;
700 nd
->path
.dentry
= path
->dentry
;
704 * Helper to directly jump to a known parsed path from ->follow_link,
705 * caller must have taken a reference to path beforehand.
707 void nd_jump_link(struct nameidata
*nd
, struct path
*path
)
712 nd
->inode
= nd
->path
.dentry
->d_inode
;
713 nd
->flags
|= LOOKUP_JUMPED
;
716 static inline void put_link(struct nameidata
*nd
, struct path
*link
, void *cookie
)
718 struct inode
*inode
= link
->dentry
->d_inode
;
719 if (cookie
&& inode
->i_op
->put_link
)
720 inode
->i_op
->put_link(link
->dentry
, cookie
);
724 int sysctl_protected_symlinks __read_mostly
= 0;
725 int sysctl_protected_hardlinks __read_mostly
= 0;
728 * may_follow_link - Check symlink following for unsafe situations
729 * @link: The path of the symlink
730 * @nd: nameidata pathwalk data
732 * In the case of the sysctl_protected_symlinks sysctl being enabled,
733 * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
734 * in a sticky world-writable directory. This is to protect privileged
735 * processes from failing races against path names that may change out
736 * from under them by way of other users creating malicious symlinks.
737 * It will permit symlinks to be followed only when outside a sticky
738 * world-writable directory, or when the uid of the symlink and follower
739 * match, or when the directory owner matches the symlink's owner.
741 * Returns 0 if following the symlink is allowed, -ve on error.
743 static inline int may_follow_link(struct path
*link
, struct nameidata
*nd
)
745 const struct inode
*inode
;
746 const struct inode
*parent
;
748 if (!sysctl_protected_symlinks
)
751 /* Allowed if owner and follower match. */
752 inode
= link
->dentry
->d_inode
;
753 if (uid_eq(current_cred()->fsuid
, inode
->i_uid
))
756 /* Allowed if parent directory not sticky and world-writable. */
757 parent
= nd
->path
.dentry
->d_inode
;
758 if ((parent
->i_mode
& (S_ISVTX
|S_IWOTH
)) != (S_ISVTX
|S_IWOTH
))
761 /* Allowed if parent directory and link owner match. */
762 if (uid_eq(parent
->i_uid
, inode
->i_uid
))
765 audit_log_link_denied("follow_link", link
);
766 path_put_conditional(link
, nd
);
772 * safe_hardlink_source - Check for safe hardlink conditions
773 * @inode: the source inode to hardlink from
775 * Return false if at least one of the following conditions:
776 * - inode is not a regular file
778 * - inode is setgid and group-exec
779 * - access failure for read and write
781 * Otherwise returns true.
783 static bool safe_hardlink_source(struct inode
*inode
)
785 umode_t mode
= inode
->i_mode
;
787 /* Special files should not get pinned to the filesystem. */
791 /* Setuid files should not get pinned to the filesystem. */
795 /* Executable setgid files should not get pinned to the filesystem. */
796 if ((mode
& (S_ISGID
| S_IXGRP
)) == (S_ISGID
| S_IXGRP
))
799 /* Hardlinking to unreadable or unwritable sources is dangerous. */
800 if (inode_permission(inode
, MAY_READ
| MAY_WRITE
))
807 * may_linkat - Check permissions for creating a hardlink
808 * @link: the source to hardlink from
810 * Block hardlink when all of:
811 * - sysctl_protected_hardlinks enabled
812 * - fsuid does not match inode
813 * - hardlink source is unsafe (see safe_hardlink_source() above)
816 * Returns 0 if successful, -ve on error.
818 static int may_linkat(struct path
*link
)
820 const struct cred
*cred
;
823 if (!sysctl_protected_hardlinks
)
826 cred
= current_cred();
827 inode
= link
->dentry
->d_inode
;
829 /* Source inode owner (or CAP_FOWNER) can hardlink all they like,
830 * otherwise, it must be a safe source.
832 if (uid_eq(cred
->fsuid
, inode
->i_uid
) || safe_hardlink_source(inode
) ||
836 audit_log_link_denied("linkat", link
);
840 static __always_inline
const char *
841 get_link(struct path
*link
, struct nameidata
*nd
, void **p
)
843 struct dentry
*dentry
= link
->dentry
;
844 struct inode
*inode
= dentry
->d_inode
;
848 BUG_ON(nd
->flags
& LOOKUP_RCU
);
850 if (link
->mnt
== nd
->path
.mnt
)
853 res
= ERR_PTR(-ELOOP
);
854 if (unlikely(current
->total_link_count
>= 40))
858 current
->total_link_count
++;
862 error
= security_inode_follow_link(dentry
);
863 res
= ERR_PTR(error
);
867 nd
->last_type
= LAST_BIND
;
871 res
= inode
->i_op
->follow_link(dentry
, p
, nd
);
881 static int follow_up_rcu(struct path
*path
)
883 struct mount
*mnt
= real_mount(path
->mnt
);
884 struct mount
*parent
;
885 struct dentry
*mountpoint
;
887 parent
= mnt
->mnt_parent
;
888 if (&parent
->mnt
== path
->mnt
)
890 mountpoint
= mnt
->mnt_mountpoint
;
891 path
->dentry
= mountpoint
;
892 path
->mnt
= &parent
->mnt
;
897 * follow_up - Find the mountpoint of path's vfsmount
899 * Given a path, find the mountpoint of its source file system.
900 * Replace @path with the path of the mountpoint in the parent mount.
903 * Return 1 if we went up a level and 0 if we were already at the
906 int follow_up(struct path
*path
)
908 struct mount
*mnt
= real_mount(path
->mnt
);
909 struct mount
*parent
;
910 struct dentry
*mountpoint
;
912 read_seqlock_excl(&mount_lock
);
913 parent
= mnt
->mnt_parent
;
915 read_sequnlock_excl(&mount_lock
);
918 mntget(&parent
->mnt
);
919 mountpoint
= dget(mnt
->mnt_mountpoint
);
920 read_sequnlock_excl(&mount_lock
);
922 path
->dentry
= mountpoint
;
924 path
->mnt
= &parent
->mnt
;
927 EXPORT_SYMBOL(follow_up
);
930 * Perform an automount
931 * - return -EISDIR to tell follow_managed() to stop and return the path we
934 static int follow_automount(struct path
*path
, unsigned flags
,
937 struct vfsmount
*mnt
;
940 if (!path
->dentry
->d_op
|| !path
->dentry
->d_op
->d_automount
)
943 /* We don't want to mount if someone's just doing a stat -
944 * unless they're stat'ing a directory and appended a '/' to
947 * We do, however, want to mount if someone wants to open or
948 * create a file of any type under the mountpoint, wants to
949 * traverse through the mountpoint or wants to open the
950 * mounted directory. Also, autofs may mark negative dentries
951 * as being automount points. These will need the attentions
952 * of the daemon to instantiate them before they can be used.
954 if (!(flags
& (LOOKUP_PARENT
| LOOKUP_DIRECTORY
|
955 LOOKUP_OPEN
| LOOKUP_CREATE
| LOOKUP_AUTOMOUNT
)) &&
956 path
->dentry
->d_inode
)
959 current
->total_link_count
++;
960 if (current
->total_link_count
>= 40)
963 mnt
= path
->dentry
->d_op
->d_automount(path
);
966 * The filesystem is allowed to return -EISDIR here to indicate
967 * it doesn't want to automount. For instance, autofs would do
968 * this so that its userspace daemon can mount on this dentry.
970 * However, we can only permit this if it's a terminal point in
971 * the path being looked up; if it wasn't then the remainder of
972 * the path is inaccessible and we should say so.
974 if (PTR_ERR(mnt
) == -EISDIR
&& (flags
& LOOKUP_PARENT
))
979 if (!mnt
) /* mount collision */
983 /* lock_mount() may release path->mnt on error */
987 err
= finish_automount(mnt
, path
);
991 /* Someone else made a mount here whilst we were busy */
996 path
->dentry
= dget(mnt
->mnt_root
);
1005 * Handle a dentry that is managed in some way.
1006 * - Flagged for transit management (autofs)
1007 * - Flagged as mountpoint
1008 * - Flagged as automount point
1010 * This may only be called in refwalk mode.
1012 * Serialization is taken care of in namespace.c
1014 static int follow_managed(struct path
*path
, unsigned flags
)
1016 struct vfsmount
*mnt
= path
->mnt
; /* held by caller, must be left alone */
1018 bool need_mntput
= false;
1021 /* Given that we're not holding a lock here, we retain the value in a
1022 * local variable for each dentry as we look at it so that we don't see
1023 * the components of that value change under us */
1024 while (managed
= ACCESS_ONCE(path
->dentry
->d_flags
),
1025 managed
&= DCACHE_MANAGED_DENTRY
,
1026 unlikely(managed
!= 0)) {
1027 /* Allow the filesystem to manage the transit without i_mutex
1029 if (managed
& DCACHE_MANAGE_TRANSIT
) {
1030 BUG_ON(!path
->dentry
->d_op
);
1031 BUG_ON(!path
->dentry
->d_op
->d_manage
);
1032 ret
= path
->dentry
->d_op
->d_manage(path
->dentry
, false);
1037 /* Transit to a mounted filesystem. */
1038 if (managed
& DCACHE_MOUNTED
) {
1039 struct vfsmount
*mounted
= lookup_mnt(path
);
1044 path
->mnt
= mounted
;
1045 path
->dentry
= dget(mounted
->mnt_root
);
1050 /* Something is mounted on this dentry in another
1051 * namespace and/or whatever was mounted there in this
1052 * namespace got unmounted before lookup_mnt() could
1056 /* Handle an automount point */
1057 if (managed
& DCACHE_NEED_AUTOMOUNT
) {
1058 ret
= follow_automount(path
, flags
, &need_mntput
);
1064 /* We didn't change the current path point */
1068 if (need_mntput
&& path
->mnt
== mnt
)
1072 return ret
< 0 ? ret
: need_mntput
;
1075 int follow_down_one(struct path
*path
)
1077 struct vfsmount
*mounted
;
1079 mounted
= lookup_mnt(path
);
1083 path
->mnt
= mounted
;
1084 path
->dentry
= dget(mounted
->mnt_root
);
1089 EXPORT_SYMBOL(follow_down_one
);
1091 static inline int managed_dentry_rcu(struct dentry
*dentry
)
1093 return (dentry
->d_flags
& DCACHE_MANAGE_TRANSIT
) ?
1094 dentry
->d_op
->d_manage(dentry
, true) : 0;
1098 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
1099 * we meet a managed dentry that would need blocking.
1101 static bool __follow_mount_rcu(struct nameidata
*nd
, struct path
*path
,
1102 struct inode
**inode
)
1105 struct mount
*mounted
;
1107 * Don't forget we might have a non-mountpoint managed dentry
1108 * that wants to block transit.
1110 switch (managed_dentry_rcu(path
->dentry
)) {
1120 if (!d_mountpoint(path
->dentry
))
1121 return !(path
->dentry
->d_flags
& DCACHE_NEED_AUTOMOUNT
);
1123 mounted
= __lookup_mnt(path
->mnt
, path
->dentry
);
1126 path
->mnt
= &mounted
->mnt
;
1127 path
->dentry
= mounted
->mnt
.mnt_root
;
1128 nd
->flags
|= LOOKUP_JUMPED
;
1129 nd
->seq
= read_seqcount_begin(&path
->dentry
->d_seq
);
1131 * Update the inode too. We don't need to re-check the
1132 * dentry sequence number here after this d_inode read,
1133 * because a mount-point is always pinned.
1135 *inode
= path
->dentry
->d_inode
;
1137 return !read_seqretry(&mount_lock
, nd
->m_seq
) &&
1138 !(path
->dentry
->d_flags
& DCACHE_NEED_AUTOMOUNT
);
1141 static int follow_dotdot_rcu(struct nameidata
*nd
)
1143 struct inode
*inode
= nd
->inode
;
1148 if (nd
->path
.dentry
== nd
->root
.dentry
&&
1149 nd
->path
.mnt
== nd
->root
.mnt
) {
1152 if (nd
->path
.dentry
!= nd
->path
.mnt
->mnt_root
) {
1153 struct dentry
*old
= nd
->path
.dentry
;
1154 struct dentry
*parent
= old
->d_parent
;
1157 inode
= parent
->d_inode
;
1158 seq
= read_seqcount_begin(&parent
->d_seq
);
1159 if (read_seqcount_retry(&old
->d_seq
, nd
->seq
))
1161 nd
->path
.dentry
= parent
;
1165 if (!follow_up_rcu(&nd
->path
))
1167 inode
= nd
->path
.dentry
->d_inode
;
1168 nd
->seq
= read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1170 while (d_mountpoint(nd
->path
.dentry
)) {
1171 struct mount
*mounted
;
1172 mounted
= __lookup_mnt(nd
->path
.mnt
, nd
->path
.dentry
);
1175 nd
->path
.mnt
= &mounted
->mnt
;
1176 nd
->path
.dentry
= mounted
->mnt
.mnt_root
;
1177 inode
= nd
->path
.dentry
->d_inode
;
1178 nd
->seq
= read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1179 if (read_seqretry(&mount_lock
, nd
->m_seq
))
1186 nd
->flags
&= ~LOOKUP_RCU
;
1187 if (!(nd
->flags
& LOOKUP_ROOT
))
1188 nd
->root
.mnt
= NULL
;
1194 * Follow down to the covering mount currently visible to userspace. At each
1195 * point, the filesystem owning that dentry may be queried as to whether the
1196 * caller is permitted to proceed or not.
1198 int follow_down(struct path
*path
)
1203 while (managed
= ACCESS_ONCE(path
->dentry
->d_flags
),
1204 unlikely(managed
& DCACHE_MANAGED_DENTRY
)) {
1205 /* Allow the filesystem to manage the transit without i_mutex
1208 * We indicate to the filesystem if someone is trying to mount
1209 * something here. This gives autofs the chance to deny anyone
1210 * other than its daemon the right to mount on its
1213 * The filesystem may sleep at this point.
1215 if (managed
& DCACHE_MANAGE_TRANSIT
) {
1216 BUG_ON(!path
->dentry
->d_op
);
1217 BUG_ON(!path
->dentry
->d_op
->d_manage
);
1218 ret
= path
->dentry
->d_op
->d_manage(
1219 path
->dentry
, false);
1221 return ret
== -EISDIR
? 0 : ret
;
1224 /* Transit to a mounted filesystem. */
1225 if (managed
& DCACHE_MOUNTED
) {
1226 struct vfsmount
*mounted
= lookup_mnt(path
);
1231 path
->mnt
= mounted
;
1232 path
->dentry
= dget(mounted
->mnt_root
);
1236 /* Don't handle automount points here */
1241 EXPORT_SYMBOL(follow_down
);
1244 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1246 static void follow_mount(struct path
*path
)
1248 while (d_mountpoint(path
->dentry
)) {
1249 struct vfsmount
*mounted
= lookup_mnt(path
);
1254 path
->mnt
= mounted
;
1255 path
->dentry
= dget(mounted
->mnt_root
);
1259 static void follow_dotdot(struct nameidata
*nd
)
1265 struct dentry
*old
= nd
->path
.dentry
;
1267 if (nd
->path
.dentry
== nd
->root
.dentry
&&
1268 nd
->path
.mnt
== nd
->root
.mnt
) {
1271 if (nd
->path
.dentry
!= nd
->path
.mnt
->mnt_root
) {
1272 /* rare case of legitimate dget_parent()... */
1273 nd
->path
.dentry
= dget_parent(nd
->path
.dentry
);
1277 if (!follow_up(&nd
->path
))
1280 follow_mount(&nd
->path
);
1281 nd
->inode
= nd
->path
.dentry
->d_inode
;
1285 * This looks up the name in dcache, possibly revalidates the old dentry and
1286 * allocates a new one if not found or not valid. In the need_lookup argument
1287 * returns whether i_op->lookup is necessary.
1289 * dir->d_inode->i_mutex must be held
1291 static struct dentry
*lookup_dcache(struct qstr
*name
, struct dentry
*dir
,
1292 unsigned int flags
, bool *need_lookup
)
1294 struct dentry
*dentry
;
1297 *need_lookup
= false;
1298 dentry
= d_lookup(dir
, name
);
1300 if (dentry
->d_flags
& DCACHE_OP_REVALIDATE
) {
1301 error
= d_revalidate(dentry
, flags
);
1302 if (unlikely(error
<= 0)) {
1305 return ERR_PTR(error
);
1307 d_invalidate(dentry
);
1316 dentry
= d_alloc(dir
, name
);
1317 if (unlikely(!dentry
))
1318 return ERR_PTR(-ENOMEM
);
1320 *need_lookup
= true;
1326 * Call i_op->lookup on the dentry. The dentry must be negative and
1329 * dir->d_inode->i_mutex must be held
1331 static struct dentry
*lookup_real(struct inode
*dir
, struct dentry
*dentry
,
1336 /* Don't create child dentry for a dead directory. */
1337 if (unlikely(IS_DEADDIR(dir
))) {
1339 return ERR_PTR(-ENOENT
);
1342 old
= dir
->i_op
->lookup(dir
, dentry
, flags
);
1343 if (unlikely(old
)) {
1350 static struct dentry
*__lookup_hash(struct qstr
*name
,
1351 struct dentry
*base
, unsigned int flags
)
1354 struct dentry
*dentry
;
1356 dentry
= lookup_dcache(name
, base
, flags
, &need_lookup
);
1360 return lookup_real(base
->d_inode
, dentry
, flags
);
1364 * It's more convoluted than I'd like it to be, but... it's still fairly
1365 * small and for now I'd prefer to have fast path as straight as possible.
1366 * It _is_ time-critical.
1368 static int lookup_fast(struct nameidata
*nd
,
1369 struct path
*path
, struct inode
**inode
)
1371 struct vfsmount
*mnt
= nd
->path
.mnt
;
1372 struct dentry
*dentry
, *parent
= nd
->path
.dentry
;
1378 * Rename seqlock is not required here because in the off chance
1379 * of a false negative due to a concurrent rename, we're going to
1380 * do the non-racy lookup, below.
1382 if (nd
->flags
& LOOKUP_RCU
) {
1385 dentry
= __d_lookup_rcu(parent
, &nd
->last
, &seq
);
1390 * This sequence count validates that the inode matches
1391 * the dentry name information from lookup.
1393 *inode
= dentry
->d_inode
;
1394 negative
= d_is_negative(dentry
);
1395 if (read_seqcount_retry(&dentry
->d_seq
, seq
))
1401 * This sequence count validates that the parent had no
1402 * changes while we did the lookup of the dentry above.
1404 * The memory barrier in read_seqcount_begin of child is
1405 * enough, we can use __read_seqcount_retry here.
1407 if (__read_seqcount_retry(&parent
->d_seq
, nd
->seq
))
1411 if (unlikely(dentry
->d_flags
& DCACHE_OP_REVALIDATE
)) {
1412 status
= d_revalidate(dentry
, nd
->flags
);
1413 if (unlikely(status
<= 0)) {
1414 if (status
!= -ECHILD
)
1420 path
->dentry
= dentry
;
1421 if (likely(__follow_mount_rcu(nd
, path
, inode
)))
1424 if (unlazy_walk(nd
, dentry
))
1427 dentry
= __d_lookup(parent
, &nd
->last
);
1430 if (unlikely(!dentry
))
1433 if (unlikely(dentry
->d_flags
& DCACHE_OP_REVALIDATE
) && need_reval
)
1434 status
= d_revalidate(dentry
, nd
->flags
);
1435 if (unlikely(status
<= 0)) {
1440 d_invalidate(dentry
);
1445 if (unlikely(d_is_negative(dentry
))) {
1450 path
->dentry
= dentry
;
1451 err
= follow_managed(path
, nd
->flags
);
1452 if (unlikely(err
< 0)) {
1453 path_put_conditional(path
, nd
);
1457 nd
->flags
|= LOOKUP_JUMPED
;
1458 *inode
= path
->dentry
->d_inode
;
1465 /* Fast lookup failed, do it the slow way */
1466 static int lookup_slow(struct nameidata
*nd
, struct path
*path
)
1468 struct dentry
*dentry
, *parent
;
1471 parent
= nd
->path
.dentry
;
1472 BUG_ON(nd
->inode
!= parent
->d_inode
);
1474 mutex_lock(&parent
->d_inode
->i_mutex
);
1475 dentry
= __lookup_hash(&nd
->last
, parent
, nd
->flags
);
1476 mutex_unlock(&parent
->d_inode
->i_mutex
);
1478 return PTR_ERR(dentry
);
1479 path
->mnt
= nd
->path
.mnt
;
1480 path
->dentry
= dentry
;
1481 err
= follow_managed(path
, nd
->flags
);
1482 if (unlikely(err
< 0)) {
1483 path_put_conditional(path
, nd
);
1487 nd
->flags
|= LOOKUP_JUMPED
;
1491 static inline int may_lookup(struct nameidata
*nd
)
1493 if (nd
->flags
& LOOKUP_RCU
) {
1494 int err
= inode_permission(nd
->inode
, MAY_EXEC
|MAY_NOT_BLOCK
);
1497 if (unlazy_walk(nd
, NULL
))
1500 return inode_permission(nd
->inode
, MAY_EXEC
);
1503 static inline int handle_dots(struct nameidata
*nd
, int type
)
1505 if (type
== LAST_DOTDOT
) {
1506 if (nd
->flags
& LOOKUP_RCU
) {
1507 if (follow_dotdot_rcu(nd
))
1515 static void terminate_walk(struct nameidata
*nd
)
1517 if (!(nd
->flags
& LOOKUP_RCU
)) {
1518 path_put(&nd
->path
);
1520 nd
->flags
&= ~LOOKUP_RCU
;
1521 if (!(nd
->flags
& LOOKUP_ROOT
))
1522 nd
->root
.mnt
= NULL
;
1528 * Do we need to follow links? We _really_ want to be able
1529 * to do this check without having to look at inode->i_op,
1530 * so we keep a cache of "no, this doesn't need follow_link"
1531 * for the common case.
1533 static inline int should_follow_link(struct dentry
*dentry
, int follow
)
1535 return unlikely(d_is_symlink(dentry
)) ? follow
: 0;
1538 static int walk_component(struct nameidata
*nd
, int follow
)
1541 struct inode
*inode
;
1544 * "." and ".." are special - ".." especially so because it has
1545 * to be able to know about the current root directory and
1546 * parent relationships.
1548 if (unlikely(nd
->last_type
!= LAST_NORM
))
1549 return handle_dots(nd
, nd
->last_type
);
1550 err
= lookup_fast(nd
, &path
, &inode
);
1551 if (unlikely(err
)) {
1555 err
= lookup_slow(nd
, &path
);
1559 inode
= path
.dentry
->d_inode
;
1561 if (d_is_negative(path
.dentry
))
1565 if (should_follow_link(path
.dentry
, follow
)) {
1566 if (nd
->flags
& LOOKUP_RCU
) {
1567 if (unlikely(nd
->path
.mnt
!= path
.mnt
||
1568 unlazy_walk(nd
, path
.dentry
))) {
1573 BUG_ON(inode
!= path
.dentry
->d_inode
);
1577 path_to_nameidata(&path
, nd
);
1582 path_to_nameidata(&path
, nd
);
1589 * We can do the critical dentry name comparison and hashing
1590 * operations one word at a time, but we are limited to:
1592 * - Architectures with fast unaligned word accesses. We could
1593 * do a "get_unaligned()" if this helps and is sufficiently
1596 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
1597 * do not trap on the (extremely unlikely) case of a page
1598 * crossing operation.
1600 * - Furthermore, we need an efficient 64-bit compile for the
1601 * 64-bit case in order to generate the "number of bytes in
1602 * the final mask". Again, that could be replaced with a
1603 * efficient population count instruction or similar.
1605 #ifdef CONFIG_DCACHE_WORD_ACCESS
1607 #include <asm/word-at-a-time.h>
1611 static inline unsigned int fold_hash(unsigned long hash
)
1613 return hash_64(hash
, 32);
1616 #else /* 32-bit case */
1618 #define fold_hash(x) (x)
1622 unsigned int full_name_hash(const unsigned char *name
, unsigned int len
)
1624 unsigned long a
, mask
;
1625 unsigned long hash
= 0;
1628 a
= load_unaligned_zeropad(name
);
1629 if (len
< sizeof(unsigned long))
1633 name
+= sizeof(unsigned long);
1634 len
-= sizeof(unsigned long);
1638 mask
= bytemask_from_count(len
);
1641 return fold_hash(hash
);
1643 EXPORT_SYMBOL(full_name_hash
);
1646 * Calculate the length and hash of the path component, and
1647 * return the "hash_len" as the result.
1649 static inline u64
hash_name(const char *name
)
1651 unsigned long a
, b
, adata
, bdata
, mask
, hash
, len
;
1652 const struct word_at_a_time constants
= WORD_AT_A_TIME_CONSTANTS
;
1655 len
= -sizeof(unsigned long);
1657 hash
= (hash
+ a
) * 9;
1658 len
+= sizeof(unsigned long);
1659 a
= load_unaligned_zeropad(name
+len
);
1660 b
= a
^ REPEAT_BYTE('/');
1661 } while (!(has_zero(a
, &adata
, &constants
) | has_zero(b
, &bdata
, &constants
)));
1663 adata
= prep_zero_mask(a
, adata
, &constants
);
1664 bdata
= prep_zero_mask(b
, bdata
, &constants
);
1666 mask
= create_zero_mask(adata
| bdata
);
1668 hash
+= a
& zero_bytemask(mask
);
1669 len
+= find_zero(mask
);
1670 return hashlen_create(fold_hash(hash
), len
);
1675 unsigned int full_name_hash(const unsigned char *name
, unsigned int len
)
1677 unsigned long hash
= init_name_hash();
1679 hash
= partial_name_hash(*name
++, hash
);
1680 return end_name_hash(hash
);
1682 EXPORT_SYMBOL(full_name_hash
);
1685 * We know there's a real path component here of at least
1688 static inline u64
hash_name(const char *name
)
1690 unsigned long hash
= init_name_hash();
1691 unsigned long len
= 0, c
;
1693 c
= (unsigned char)*name
;
1696 hash
= partial_name_hash(c
, hash
);
1697 c
= (unsigned char)name
[len
];
1698 } while (c
&& c
!= '/');
1699 return hashlen_create(end_name_hash(hash
), len
);
1706 * This is the basic name resolution function, turning a pathname into
1707 * the final dentry. We expect 'base' to be positive and a directory.
1709 * Returns 0 and nd will have valid dentry and mnt on success.
1710 * Returns error and drops reference to input namei data on failure.
1712 static int link_path_walk(const char *name
, struct nameidata
*nd
)
1721 /* At this point we know we have a real path component. */
1726 err
= may_lookup(nd
);
1730 hash_len
= hash_name(name
);
1733 if (name
[0] == '.') switch (hashlen_len(hash_len
)) {
1735 if (name
[1] == '.') {
1737 nd
->flags
|= LOOKUP_JUMPED
;
1743 if (likely(type
== LAST_NORM
)) {
1744 struct dentry
*parent
= nd
->path
.dentry
;
1745 nd
->flags
&= ~LOOKUP_JUMPED
;
1746 if (unlikely(parent
->d_flags
& DCACHE_OP_HASH
)) {
1747 struct qstr
this = { { .hash_len
= hash_len
}, .name
= name
};
1748 err
= parent
->d_op
->d_hash(parent
, &this);
1751 hash_len
= this.hash_len
;
1756 nd
->last
.hash_len
= hash_len
;
1757 nd
->last
.name
= name
;
1758 nd
->last_type
= type
;
1760 name
+= hashlen_len(hash_len
);
1764 * If it wasn't NUL, we know it was '/'. Skip that
1765 * slash, and continue until no more slashes.
1769 } while (unlikely(*name
== '/'));
1773 err
= walk_component(nd
, LOOKUP_FOLLOW
);
1783 if (unlikely(current
->link_count
>= MAX_NESTED_LINKS
)) {
1784 path_put_conditional(&nd
->link
, nd
);
1785 path_put(&nd
->path
);
1788 BUG_ON(nd
->depth
>= MAX_NESTED_LINKS
);
1791 current
->link_count
++;
1794 s
= get_link(&link
, nd
, &cookie
);
1796 if (unlikely(IS_ERR(s
))) {
1798 current
->link_count
--;
1805 put_link(nd
, &link
, cookie
);
1806 current
->link_count
--;
1812 path_put(&nd
->path
);
1813 nd
->path
= nd
->root
;
1814 path_get(&nd
->root
);
1815 nd
->flags
|= LOOKUP_JUMPED
;
1817 nd
->inode
= nd
->path
.dentry
->d_inode
;
1818 err
= link_path_walk(s
, nd
);
1819 if (unlikely(err
)) {
1820 put_link(nd
, &link
, cookie
);
1821 current
->link_count
--;
1825 err
= walk_component(nd
, LOOKUP_FOLLOW
);
1826 put_link(nd
, &link
, cookie
);
1827 current
->link_count
--;
1833 if (!d_can_lookup(nd
->path
.dentry
)) {
1842 static int path_init(int dfd
, const struct filename
*name
, unsigned int flags
,
1843 struct nameidata
*nd
)
1846 const char *s
= name
->name
;
1848 nd
->last_type
= LAST_ROOT
; /* if there are only slashes... */
1849 nd
->flags
= flags
| LOOKUP_JUMPED
| LOOKUP_PARENT
;
1852 if (flags
& LOOKUP_ROOT
) {
1853 struct dentry
*root
= nd
->root
.dentry
;
1854 struct inode
*inode
= root
->d_inode
;
1856 if (!d_can_lookup(root
))
1858 retval
= inode_permission(inode
, MAY_EXEC
);
1862 nd
->path
= nd
->root
;
1864 if (flags
& LOOKUP_RCU
) {
1866 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1867 nd
->m_seq
= read_seqbegin(&mount_lock
);
1869 path_get(&nd
->path
);
1874 nd
->root
.mnt
= NULL
;
1876 nd
->m_seq
= read_seqbegin(&mount_lock
);
1878 if (flags
& LOOKUP_RCU
) {
1880 nd
->seq
= set_root_rcu(nd
);
1883 path_get(&nd
->root
);
1885 nd
->path
= nd
->root
;
1886 } else if (dfd
== AT_FDCWD
) {
1887 if (flags
& LOOKUP_RCU
) {
1888 struct fs_struct
*fs
= current
->fs
;
1894 seq
= read_seqcount_begin(&fs
->seq
);
1896 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1897 } while (read_seqcount_retry(&fs
->seq
, seq
));
1899 get_fs_pwd(current
->fs
, &nd
->path
);
1902 /* Caller must check execute permissions on the starting path component */
1903 struct fd f
= fdget_raw(dfd
);
1904 struct dentry
*dentry
;
1909 dentry
= f
.file
->f_path
.dentry
;
1912 if (!d_can_lookup(dentry
)) {
1918 nd
->path
= f
.file
->f_path
;
1919 if (flags
& LOOKUP_RCU
) {
1920 if (f
.flags
& FDPUT_FPUT
)
1922 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1925 path_get(&nd
->path
);
1930 nd
->inode
= nd
->path
.dentry
->d_inode
;
1931 if (!(flags
& LOOKUP_RCU
))
1933 if (likely(!read_seqcount_retry(&nd
->path
.dentry
->d_seq
, nd
->seq
)))
1935 if (!(nd
->flags
& LOOKUP_ROOT
))
1936 nd
->root
.mnt
= NULL
;
1940 current
->total_link_count
= 0;
1941 return link_path_walk(s
, nd
);
1944 static void path_cleanup(struct nameidata
*nd
)
1946 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
)) {
1947 path_put(&nd
->root
);
1948 nd
->root
.mnt
= NULL
;
1950 if (unlikely(nd
->base
))
1954 static int trailing_symlink(struct path
*link
, struct nameidata
*nd
, void **p
)
1957 int error
= may_follow_link(link
, nd
);
1958 if (unlikely(error
))
1960 nd
->flags
|= LOOKUP_PARENT
;
1961 s
= get_link(link
, nd
, p
);
1962 if (unlikely(IS_ERR(s
)))
1969 path_put(&nd
->path
);
1970 nd
->path
= nd
->root
;
1971 path_get(&nd
->root
);
1972 nd
->flags
|= LOOKUP_JUMPED
;
1974 nd
->inode
= nd
->path
.dentry
->d_inode
;
1975 error
= link_path_walk(s
, nd
);
1976 if (unlikely(error
))
1977 put_link(nd
, link
, *p
);
1981 static inline int lookup_last(struct nameidata
*nd
)
1983 if (nd
->last_type
== LAST_NORM
&& nd
->last
.name
[nd
->last
.len
])
1984 nd
->flags
|= LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
;
1986 nd
->flags
&= ~LOOKUP_PARENT
;
1987 return walk_component(nd
, nd
->flags
& LOOKUP_FOLLOW
);
1990 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
1991 static int path_lookupat(int dfd
, const struct filename
*name
,
1992 unsigned int flags
, struct nameidata
*nd
)
1997 * Path walking is largely split up into 2 different synchronisation
1998 * schemes, rcu-walk and ref-walk (explained in
1999 * Documentation/filesystems/path-lookup.txt). These share much of the
2000 * path walk code, but some things particularly setup, cleanup, and
2001 * following mounts are sufficiently divergent that functions are
2002 * duplicated. Typically there is a function foo(), and its RCU
2003 * analogue, foo_rcu().
2005 * -ECHILD is the error number of choice (just to avoid clashes) that
2006 * is returned if some aspect of an rcu-walk fails. Such an error must
2007 * be handled by restarting a traditional ref-walk (which will always
2008 * be able to complete).
2010 err
= path_init(dfd
, name
, flags
, nd
);
2011 if (!err
&& !(flags
& LOOKUP_PARENT
)) {
2012 err
= lookup_last(nd
);
2015 struct path link
= nd
->link
;
2016 err
= trailing_symlink(&link
, nd
, &cookie
);
2019 err
= lookup_last(nd
);
2020 put_link(nd
, &link
, cookie
);
2025 err
= complete_walk(nd
);
2027 if (!err
&& nd
->flags
& LOOKUP_DIRECTORY
) {
2028 if (!d_can_lookup(nd
->path
.dentry
)) {
2029 path_put(&nd
->path
);
2038 static int filename_lookup(int dfd
, struct filename
*name
,
2039 unsigned int flags
, struct nameidata
*nd
)
2041 int retval
= path_lookupat(dfd
, name
, flags
| LOOKUP_RCU
, nd
);
2042 if (unlikely(retval
== -ECHILD
))
2043 retval
= path_lookupat(dfd
, name
, flags
, nd
);
2044 if (unlikely(retval
== -ESTALE
))
2045 retval
= path_lookupat(dfd
, name
, flags
| LOOKUP_REVAL
, nd
);
2047 if (likely(!retval
))
2048 audit_inode(name
, nd
->path
.dentry
, flags
& LOOKUP_PARENT
);
2052 /* does lookup, returns the object with parent locked */
2053 struct dentry
*kern_path_locked(const char *name
, struct path
*path
)
2055 struct filename
*filename
= getname_kernel(name
);
2056 struct nameidata nd
;
2060 if (IS_ERR(filename
))
2061 return ERR_CAST(filename
);
2063 err
= filename_lookup(AT_FDCWD
, filename
, LOOKUP_PARENT
, &nd
);
2068 if (nd
.last_type
!= LAST_NORM
) {
2070 d
= ERR_PTR(-EINVAL
);
2073 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2074 d
= __lookup_hash(&nd
.last
, nd
.path
.dentry
, 0);
2076 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
2086 int kern_path(const char *name
, unsigned int flags
, struct path
*path
)
2088 struct nameidata nd
;
2089 struct filename
*filename
= getname_kernel(name
);
2090 int res
= PTR_ERR(filename
);
2092 if (!IS_ERR(filename
)) {
2093 res
= filename_lookup(AT_FDCWD
, filename
, flags
, &nd
);
2100 EXPORT_SYMBOL(kern_path
);
2103 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
2104 * @dentry: pointer to dentry of the base directory
2105 * @mnt: pointer to vfs mount of the base directory
2106 * @name: pointer to file name
2107 * @flags: lookup flags
2108 * @path: pointer to struct path to fill
2110 int vfs_path_lookup(struct dentry
*dentry
, struct vfsmount
*mnt
,
2111 const char *name
, unsigned int flags
,
2114 struct filename
*filename
= getname_kernel(name
);
2115 int err
= PTR_ERR(filename
);
2117 BUG_ON(flags
& LOOKUP_PARENT
);
2119 /* the first argument of filename_lookup() is ignored with LOOKUP_ROOT */
2120 if (!IS_ERR(filename
)) {
2121 struct nameidata nd
;
2122 nd
.root
.dentry
= dentry
;
2124 err
= filename_lookup(AT_FDCWD
, filename
,
2125 flags
| LOOKUP_ROOT
, &nd
);
2132 EXPORT_SYMBOL(vfs_path_lookup
);
2135 * lookup_one_len - filesystem helper to lookup single pathname component
2136 * @name: pathname component to lookup
2137 * @base: base directory to lookup from
2138 * @len: maximum length @len should be interpreted to
2140 * Note that this routine is purely a helper for filesystem usage and should
2141 * not be called by generic code.
2143 struct dentry
*lookup_one_len(const char *name
, struct dentry
*base
, int len
)
2149 WARN_ON_ONCE(!mutex_is_locked(&base
->d_inode
->i_mutex
));
2153 this.hash
= full_name_hash(name
, len
);
2155 return ERR_PTR(-EACCES
);
2157 if (unlikely(name
[0] == '.')) {
2158 if (len
< 2 || (len
== 2 && name
[1] == '.'))
2159 return ERR_PTR(-EACCES
);
2163 c
= *(const unsigned char *)name
++;
2164 if (c
== '/' || c
== '\0')
2165 return ERR_PTR(-EACCES
);
2168 * See if the low-level filesystem might want
2169 * to use its own hash..
2171 if (base
->d_flags
& DCACHE_OP_HASH
) {
2172 int err
= base
->d_op
->d_hash(base
, &this);
2174 return ERR_PTR(err
);
2177 err
= inode_permission(base
->d_inode
, MAY_EXEC
);
2179 return ERR_PTR(err
);
2181 return __lookup_hash(&this, base
, 0);
2183 EXPORT_SYMBOL(lookup_one_len
);
2185 int user_path_at_empty(int dfd
, const char __user
*name
, unsigned flags
,
2186 struct path
*path
, int *empty
)
2188 struct nameidata nd
;
2189 struct filename
*tmp
= getname_flags(name
, flags
, empty
);
2190 int err
= PTR_ERR(tmp
);
2193 BUG_ON(flags
& LOOKUP_PARENT
);
2195 err
= filename_lookup(dfd
, tmp
, flags
, &nd
);
2203 int user_path_at(int dfd
, const char __user
*name
, unsigned flags
,
2206 return user_path_at_empty(dfd
, name
, flags
, path
, NULL
);
2208 EXPORT_SYMBOL(user_path_at
);
2211 * NB: most callers don't do anything directly with the reference to the
2212 * to struct filename, but the nd->last pointer points into the name string
2213 * allocated by getname. So we must hold the reference to it until all
2214 * path-walking is complete.
2216 static struct filename
*
2217 user_path_parent(int dfd
, const char __user
*path
,
2218 struct path
*parent
,
2223 struct nameidata nd
;
2224 struct filename
*s
= getname(path
);
2227 /* only LOOKUP_REVAL is allowed in extra flags */
2228 flags
&= LOOKUP_REVAL
;
2233 error
= filename_lookup(dfd
, s
, flags
| LOOKUP_PARENT
, &nd
);
2236 return ERR_PTR(error
);
2240 *type
= nd
.last_type
;
2246 * mountpoint_last - look up last component for umount
2247 * @nd: pathwalk nameidata - currently pointing at parent directory of "last"
2248 * @path: pointer to container for result
2250 * This is a special lookup_last function just for umount. In this case, we
2251 * need to resolve the path without doing any revalidation.
2253 * The nameidata should be the result of doing a LOOKUP_PARENT pathwalk. Since
2254 * mountpoints are always pinned in the dcache, their ancestors are too. Thus,
2255 * in almost all cases, this lookup will be served out of the dcache. The only
2256 * cases where it won't are if nd->last refers to a symlink or the path is
2257 * bogus and it doesn't exist.
2260 * -error: if there was an error during lookup. This includes -ENOENT if the
2261 * lookup found a negative dentry. The nd->path reference will also be
2264 * 0: if we successfully resolved nd->path and found it to not to be a
2265 * symlink that needs to be followed. "path" will also be populated.
2266 * The nd->path reference will also be put.
2268 * 1: if we successfully resolved nd->last and found it to be a symlink
2269 * that needs to be followed. "path" will be populated with the path
2270 * to the link, and nd->path will *not* be put.
2273 mountpoint_last(struct nameidata
*nd
, struct path
*path
)
2276 struct dentry
*dentry
;
2277 struct dentry
*dir
= nd
->path
.dentry
;
2279 /* If we're in rcuwalk, drop out of it to handle last component */
2280 if (nd
->flags
& LOOKUP_RCU
) {
2281 if (unlazy_walk(nd
, NULL
)) {
2287 nd
->flags
&= ~LOOKUP_PARENT
;
2289 if (unlikely(nd
->last_type
!= LAST_NORM
)) {
2290 error
= handle_dots(nd
, nd
->last_type
);
2293 dentry
= dget(nd
->path
.dentry
);
2297 mutex_lock(&dir
->d_inode
->i_mutex
);
2298 dentry
= d_lookup(dir
, &nd
->last
);
2301 * No cached dentry. Mounted dentries are pinned in the cache,
2302 * so that means that this dentry is probably a symlink or the
2303 * path doesn't actually point to a mounted dentry.
2305 dentry
= d_alloc(dir
, &nd
->last
);
2308 mutex_unlock(&dir
->d_inode
->i_mutex
);
2311 dentry
= lookup_real(dir
->d_inode
, dentry
, nd
->flags
);
2312 error
= PTR_ERR(dentry
);
2313 if (IS_ERR(dentry
)) {
2314 mutex_unlock(&dir
->d_inode
->i_mutex
);
2318 mutex_unlock(&dir
->d_inode
->i_mutex
);
2321 if (d_is_negative(dentry
)) {
2326 path
->dentry
= dentry
;
2327 path
->mnt
= nd
->path
.mnt
;
2328 if (should_follow_link(dentry
, nd
->flags
& LOOKUP_FOLLOW
)) {
2341 * path_mountpoint - look up a path to be umounted
2342 * @dfd: directory file descriptor to start walk from
2343 * @name: full pathname to walk
2344 * @path: pointer to container for result
2345 * @flags: lookup flags
2347 * Look up the given name, but don't attempt to revalidate the last component.
2348 * Returns 0 and "path" will be valid on success; Returns error otherwise.
2351 path_mountpoint(int dfd
, const struct filename
*name
, struct path
*path
,
2352 struct nameidata
*nd
, unsigned int flags
)
2354 int err
= path_init(dfd
, name
, flags
, nd
);
2358 err
= mountpoint_last(nd
, path
);
2361 struct path link
= *path
;
2362 err
= trailing_symlink(&link
, nd
, &cookie
);
2365 err
= mountpoint_last(nd
, path
);
2366 put_link(nd
, &link
, cookie
);
2374 filename_mountpoint(int dfd
, struct filename
*name
, struct path
*path
,
2377 struct nameidata nd
;
2380 return PTR_ERR(name
);
2381 error
= path_mountpoint(dfd
, name
, path
, &nd
, flags
| LOOKUP_RCU
);
2382 if (unlikely(error
== -ECHILD
))
2383 error
= path_mountpoint(dfd
, name
, path
, &nd
, flags
);
2384 if (unlikely(error
== -ESTALE
))
2385 error
= path_mountpoint(dfd
, name
, path
, &nd
, flags
| LOOKUP_REVAL
);
2387 audit_inode(name
, path
->dentry
, 0);
2393 * user_path_mountpoint_at - lookup a path from userland in order to umount it
2394 * @dfd: directory file descriptor
2395 * @name: pathname from userland
2396 * @flags: lookup flags
2397 * @path: pointer to container to hold result
2399 * A umount is a special case for path walking. We're not actually interested
2400 * in the inode in this situation, and ESTALE errors can be a problem. We
2401 * simply want track down the dentry and vfsmount attached at the mountpoint
2402 * and avoid revalidating the last component.
2404 * Returns 0 and populates "path" on success.
2407 user_path_mountpoint_at(int dfd
, const char __user
*name
, unsigned int flags
,
2410 return filename_mountpoint(dfd
, getname(name
), path
, flags
);
2414 kern_path_mountpoint(int dfd
, const char *name
, struct path
*path
,
2417 return filename_mountpoint(dfd
, getname_kernel(name
), path
, flags
);
2419 EXPORT_SYMBOL(kern_path_mountpoint
);
2421 int __check_sticky(struct inode
*dir
, struct inode
*inode
)
2423 kuid_t fsuid
= current_fsuid();
2425 if (uid_eq(inode
->i_uid
, fsuid
))
2427 if (uid_eq(dir
->i_uid
, fsuid
))
2429 return !capable_wrt_inode_uidgid(inode
, CAP_FOWNER
);
2431 EXPORT_SYMBOL(__check_sticky
);
2434 * Check whether we can remove a link victim from directory dir, check
2435 * whether the type of victim is right.
2436 * 1. We can't do it if dir is read-only (done in permission())
2437 * 2. We should have write and exec permissions on dir
2438 * 3. We can't remove anything from append-only dir
2439 * 4. We can't do anything with immutable dir (done in permission())
2440 * 5. If the sticky bit on dir is set we should either
2441 * a. be owner of dir, or
2442 * b. be owner of victim, or
2443 * c. have CAP_FOWNER capability
2444 * 6. If the victim is append-only or immutable we can't do antyhing with
2445 * links pointing to it.
2446 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
2447 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
2448 * 9. We can't remove a root or mountpoint.
2449 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
2450 * nfs_async_unlink().
2452 static int may_delete(struct inode
*dir
, struct dentry
*victim
, bool isdir
)
2454 struct inode
*inode
= victim
->d_inode
;
2457 if (d_is_negative(victim
))
2461 BUG_ON(victim
->d_parent
->d_inode
!= dir
);
2462 audit_inode_child(dir
, victim
, AUDIT_TYPE_CHILD_DELETE
);
2464 error
= inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
2470 if (check_sticky(dir
, inode
) || IS_APPEND(inode
) ||
2471 IS_IMMUTABLE(inode
) || IS_SWAPFILE(inode
))
2474 if (!d_is_dir(victim
))
2476 if (IS_ROOT(victim
))
2478 } else if (d_is_dir(victim
))
2480 if (IS_DEADDIR(dir
))
2482 if (victim
->d_flags
& DCACHE_NFSFS_RENAMED
)
2487 /* Check whether we can create an object with dentry child in directory
2489 * 1. We can't do it if child already exists (open has special treatment for
2490 * this case, but since we are inlined it's OK)
2491 * 2. We can't do it if dir is read-only (done in permission())
2492 * 3. We should have write and exec permissions on dir
2493 * 4. We can't do it if dir is immutable (done in permission())
2495 static inline int may_create(struct inode
*dir
, struct dentry
*child
)
2497 audit_inode_child(dir
, child
, AUDIT_TYPE_CHILD_CREATE
);
2500 if (IS_DEADDIR(dir
))
2502 return inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
2506 * p1 and p2 should be directories on the same fs.
2508 struct dentry
*lock_rename(struct dentry
*p1
, struct dentry
*p2
)
2513 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2517 mutex_lock(&p1
->d_inode
->i_sb
->s_vfs_rename_mutex
);
2519 p
= d_ancestor(p2
, p1
);
2521 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2522 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_CHILD
);
2526 p
= d_ancestor(p1
, p2
);
2528 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2529 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_CHILD
);
2533 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2534 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_PARENT2
);
2537 EXPORT_SYMBOL(lock_rename
);
2539 void unlock_rename(struct dentry
*p1
, struct dentry
*p2
)
2541 mutex_unlock(&p1
->d_inode
->i_mutex
);
2543 mutex_unlock(&p2
->d_inode
->i_mutex
);
2544 mutex_unlock(&p1
->d_inode
->i_sb
->s_vfs_rename_mutex
);
2547 EXPORT_SYMBOL(unlock_rename
);
2549 int vfs_create(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
,
2552 int error
= may_create(dir
, dentry
);
2556 if (!dir
->i_op
->create
)
2557 return -EACCES
; /* shouldn't it be ENOSYS? */
2560 error
= security_inode_create(dir
, dentry
, mode
);
2563 error
= dir
->i_op
->create(dir
, dentry
, mode
, want_excl
);
2565 fsnotify_create(dir
, dentry
);
2568 EXPORT_SYMBOL(vfs_create
);
2570 static int may_open(struct path
*path
, int acc_mode
, int flag
)
2572 struct dentry
*dentry
= path
->dentry
;
2573 struct inode
*inode
= dentry
->d_inode
;
2583 switch (inode
->i_mode
& S_IFMT
) {
2587 if (acc_mode
& MAY_WRITE
)
2592 if (path
->mnt
->mnt_flags
& MNT_NODEV
)
2601 error
= inode_permission(inode
, acc_mode
);
2606 * An append-only file must be opened in append mode for writing.
2608 if (IS_APPEND(inode
)) {
2609 if ((flag
& O_ACCMODE
) != O_RDONLY
&& !(flag
& O_APPEND
))
2615 /* O_NOATIME can only be set by the owner or superuser */
2616 if (flag
& O_NOATIME
&& !inode_owner_or_capable(inode
))
2622 static int handle_truncate(struct file
*filp
)
2624 struct path
*path
= &filp
->f_path
;
2625 struct inode
*inode
= path
->dentry
->d_inode
;
2626 int error
= get_write_access(inode
);
2630 * Refuse to truncate files with mandatory locks held on them.
2632 error
= locks_verify_locked(filp
);
2634 error
= security_path_truncate(path
);
2636 error
= do_truncate(path
->dentry
, 0,
2637 ATTR_MTIME
|ATTR_CTIME
|ATTR_OPEN
,
2640 put_write_access(inode
);
2644 static inline int open_to_namei_flags(int flag
)
2646 if ((flag
& O_ACCMODE
) == 3)
2651 static int may_o_create(struct path
*dir
, struct dentry
*dentry
, umode_t mode
)
2653 int error
= security_path_mknod(dir
, dentry
, mode
, 0);
2657 error
= inode_permission(dir
->dentry
->d_inode
, MAY_WRITE
| MAY_EXEC
);
2661 return security_inode_create(dir
->dentry
->d_inode
, dentry
, mode
);
2665 * Attempt to atomically look up, create and open a file from a negative
2668 * Returns 0 if successful. The file will have been created and attached to
2669 * @file by the filesystem calling finish_open().
2671 * Returns 1 if the file was looked up only or didn't need creating. The
2672 * caller will need to perform the open themselves. @path will have been
2673 * updated to point to the new dentry. This may be negative.
2675 * Returns an error code otherwise.
2677 static int atomic_open(struct nameidata
*nd
, struct dentry
*dentry
,
2678 struct path
*path
, struct file
*file
,
2679 const struct open_flags
*op
,
2680 bool got_write
, bool need_lookup
,
2683 struct inode
*dir
= nd
->path
.dentry
->d_inode
;
2684 unsigned open_flag
= open_to_namei_flags(op
->open_flag
);
2688 int create_error
= 0;
2689 struct dentry
*const DENTRY_NOT_SET
= (void *) -1UL;
2692 BUG_ON(dentry
->d_inode
);
2694 /* Don't create child dentry for a dead directory. */
2695 if (unlikely(IS_DEADDIR(dir
))) {
2701 if ((open_flag
& O_CREAT
) && !IS_POSIXACL(dir
))
2702 mode
&= ~current_umask();
2704 excl
= (open_flag
& (O_EXCL
| O_CREAT
)) == (O_EXCL
| O_CREAT
);
2706 open_flag
&= ~O_TRUNC
;
2709 * Checking write permission is tricky, bacuse we don't know if we are
2710 * going to actually need it: O_CREAT opens should work as long as the
2711 * file exists. But checking existence breaks atomicity. The trick is
2712 * to check access and if not granted clear O_CREAT from the flags.
2714 * Another problem is returing the "right" error value (e.g. for an
2715 * O_EXCL open we want to return EEXIST not EROFS).
2717 if (((open_flag
& (O_CREAT
| O_TRUNC
)) ||
2718 (open_flag
& O_ACCMODE
) != O_RDONLY
) && unlikely(!got_write
)) {
2719 if (!(open_flag
& O_CREAT
)) {
2721 * No O_CREATE -> atomicity not a requirement -> fall
2722 * back to lookup + open
2725 } else if (open_flag
& (O_EXCL
| O_TRUNC
)) {
2726 /* Fall back and fail with the right error */
2727 create_error
= -EROFS
;
2730 /* No side effects, safe to clear O_CREAT */
2731 create_error
= -EROFS
;
2732 open_flag
&= ~O_CREAT
;
2736 if (open_flag
& O_CREAT
) {
2737 error
= may_o_create(&nd
->path
, dentry
, mode
);
2739 create_error
= error
;
2740 if (open_flag
& O_EXCL
)
2742 open_flag
&= ~O_CREAT
;
2746 if (nd
->flags
& LOOKUP_DIRECTORY
)
2747 open_flag
|= O_DIRECTORY
;
2749 file
->f_path
.dentry
= DENTRY_NOT_SET
;
2750 file
->f_path
.mnt
= nd
->path
.mnt
;
2751 error
= dir
->i_op
->atomic_open(dir
, dentry
, file
, open_flag
, mode
,
2754 if (create_error
&& error
== -ENOENT
)
2755 error
= create_error
;
2759 if (error
) { /* returned 1, that is */
2760 if (WARN_ON(file
->f_path
.dentry
== DENTRY_NOT_SET
)) {
2764 if (file
->f_path
.dentry
) {
2766 dentry
= file
->f_path
.dentry
;
2768 if (*opened
& FILE_CREATED
)
2769 fsnotify_create(dir
, dentry
);
2770 if (!dentry
->d_inode
) {
2771 WARN_ON(*opened
& FILE_CREATED
);
2773 error
= create_error
;
2777 if (excl
&& !(*opened
& FILE_CREATED
)) {
2786 * We didn't have the inode before the open, so check open permission
2789 acc_mode
= op
->acc_mode
;
2790 if (*opened
& FILE_CREATED
) {
2791 WARN_ON(!(open_flag
& O_CREAT
));
2792 fsnotify_create(dir
, dentry
);
2793 acc_mode
= MAY_OPEN
;
2795 error
= may_open(&file
->f_path
, acc_mode
, open_flag
);
2805 dentry
= lookup_real(dir
, dentry
, nd
->flags
);
2807 return PTR_ERR(dentry
);
2810 int open_flag
= op
->open_flag
;
2812 error
= create_error
;
2813 if ((open_flag
& O_EXCL
)) {
2814 if (!dentry
->d_inode
)
2816 } else if (!dentry
->d_inode
) {
2818 } else if ((open_flag
& O_TRUNC
) &&
2822 /* will fail later, go on to get the right error */
2826 path
->dentry
= dentry
;
2827 path
->mnt
= nd
->path
.mnt
;
2832 * Look up and maybe create and open the last component.
2834 * Must be called with i_mutex held on parent.
2836 * Returns 0 if the file was successfully atomically created (if necessary) and
2837 * opened. In this case the file will be returned attached to @file.
2839 * Returns 1 if the file was not completely opened at this time, though lookups
2840 * and creations will have been performed and the dentry returned in @path will
2841 * be positive upon return if O_CREAT was specified. If O_CREAT wasn't
2842 * specified then a negative dentry may be returned.
2844 * An error code is returned otherwise.
2846 * FILE_CREATE will be set in @*opened if the dentry was created and will be
2847 * cleared otherwise prior to returning.
2849 static int lookup_open(struct nameidata
*nd
, struct path
*path
,
2851 const struct open_flags
*op
,
2852 bool got_write
, int *opened
)
2854 struct dentry
*dir
= nd
->path
.dentry
;
2855 struct inode
*dir_inode
= dir
->d_inode
;
2856 struct dentry
*dentry
;
2860 *opened
&= ~FILE_CREATED
;
2861 dentry
= lookup_dcache(&nd
->last
, dir
, nd
->flags
, &need_lookup
);
2863 return PTR_ERR(dentry
);
2865 /* Cached positive dentry: will open in f_op->open */
2866 if (!need_lookup
&& dentry
->d_inode
)
2869 if ((nd
->flags
& LOOKUP_OPEN
) && dir_inode
->i_op
->atomic_open
) {
2870 return atomic_open(nd
, dentry
, path
, file
, op
, got_write
,
2871 need_lookup
, opened
);
2875 BUG_ON(dentry
->d_inode
);
2877 dentry
= lookup_real(dir_inode
, dentry
, nd
->flags
);
2879 return PTR_ERR(dentry
);
2882 /* Negative dentry, just create the file */
2883 if (!dentry
->d_inode
&& (op
->open_flag
& O_CREAT
)) {
2884 umode_t mode
= op
->mode
;
2885 if (!IS_POSIXACL(dir
->d_inode
))
2886 mode
&= ~current_umask();
2888 * This write is needed to ensure that a
2889 * rw->ro transition does not occur between
2890 * the time when the file is created and when
2891 * a permanent write count is taken through
2892 * the 'struct file' in finish_open().
2898 *opened
|= FILE_CREATED
;
2899 error
= security_path_mknod(&nd
->path
, dentry
, mode
, 0);
2902 error
= vfs_create(dir
->d_inode
, dentry
, mode
,
2903 nd
->flags
& LOOKUP_EXCL
);
2908 path
->dentry
= dentry
;
2909 path
->mnt
= nd
->path
.mnt
;
2918 * Handle the last step of open()
2920 static int do_last(struct nameidata
*nd
,
2921 struct file
*file
, const struct open_flags
*op
,
2922 int *opened
, struct filename
*name
)
2924 struct dentry
*dir
= nd
->path
.dentry
;
2925 int open_flag
= op
->open_flag
;
2926 bool will_truncate
= (open_flag
& O_TRUNC
) != 0;
2927 bool got_write
= false;
2928 int acc_mode
= op
->acc_mode
;
2929 struct inode
*inode
;
2930 struct path save_parent
= { .dentry
= NULL
, .mnt
= NULL
};
2932 bool retried
= false;
2935 nd
->flags
&= ~LOOKUP_PARENT
;
2936 nd
->flags
|= op
->intent
;
2938 if (nd
->last_type
!= LAST_NORM
) {
2939 error
= handle_dots(nd
, nd
->last_type
);
2945 if (!(open_flag
& O_CREAT
)) {
2946 if (nd
->last
.name
[nd
->last
.len
])
2947 nd
->flags
|= LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
;
2948 /* we _can_ be in RCU mode here */
2949 error
= lookup_fast(nd
, &path
, &inode
);
2956 BUG_ON(nd
->inode
!= dir
->d_inode
);
2958 /* create side of things */
2960 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED
2961 * has been cleared when we got to the last component we are
2964 error
= complete_walk(nd
);
2968 audit_inode(name
, dir
, LOOKUP_PARENT
);
2970 /* trailing slashes? */
2971 if (nd
->last
.name
[nd
->last
.len
])
2976 if (op
->open_flag
& (O_CREAT
| O_TRUNC
| O_WRONLY
| O_RDWR
)) {
2977 error
= mnt_want_write(nd
->path
.mnt
);
2981 * do _not_ fail yet - we might not need that or fail with
2982 * a different error; let lookup_open() decide; we'll be
2983 * dropping this one anyway.
2986 mutex_lock(&dir
->d_inode
->i_mutex
);
2987 error
= lookup_open(nd
, &path
, file
, op
, got_write
, opened
);
2988 mutex_unlock(&dir
->d_inode
->i_mutex
);
2994 if ((*opened
& FILE_CREATED
) ||
2995 !S_ISREG(file_inode(file
)->i_mode
))
2996 will_truncate
= false;
2998 audit_inode(name
, file
->f_path
.dentry
, 0);
3002 if (*opened
& FILE_CREATED
) {
3003 /* Don't check for write permission, don't truncate */
3004 open_flag
&= ~O_TRUNC
;
3005 will_truncate
= false;
3006 acc_mode
= MAY_OPEN
;
3007 path_to_nameidata(&path
, nd
);
3008 goto finish_open_created
;
3012 * create/update audit record if it already exists.
3014 if (d_is_positive(path
.dentry
))
3015 audit_inode(name
, path
.dentry
, 0);
3018 * If atomic_open() acquired write access it is dropped now due to
3019 * possible mount and symlink following (this might be optimized away if
3023 mnt_drop_write(nd
->path
.mnt
);
3028 if ((open_flag
& (O_EXCL
| O_CREAT
)) == (O_EXCL
| O_CREAT
))
3031 error
= follow_managed(&path
, nd
->flags
);
3036 nd
->flags
|= LOOKUP_JUMPED
;
3038 BUG_ON(nd
->flags
& LOOKUP_RCU
);
3039 inode
= path
.dentry
->d_inode
;
3041 if (d_is_negative(path
.dentry
)) {
3042 path_to_nameidata(&path
, nd
);
3046 if (should_follow_link(path
.dentry
, nd
->flags
& LOOKUP_FOLLOW
)) {
3047 if (nd
->flags
& LOOKUP_RCU
) {
3048 if (unlikely(nd
->path
.mnt
!= path
.mnt
||
3049 unlazy_walk(nd
, path
.dentry
))) {
3054 BUG_ON(inode
!= path
.dentry
->d_inode
);
3059 if (unlikely(d_is_symlink(path
.dentry
)) && !(open_flag
& O_PATH
)) {
3060 path_to_nameidata(&path
, nd
);
3065 if ((nd
->flags
& LOOKUP_RCU
) || nd
->path
.mnt
!= path
.mnt
) {
3066 path_to_nameidata(&path
, nd
);
3068 save_parent
.dentry
= nd
->path
.dentry
;
3069 save_parent
.mnt
= mntget(path
.mnt
);
3070 nd
->path
.dentry
= path
.dentry
;
3074 /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
3076 error
= complete_walk(nd
);
3078 path_put(&save_parent
);
3081 audit_inode(name
, nd
->path
.dentry
, 0);
3083 if ((open_flag
& O_CREAT
) && d_is_dir(nd
->path
.dentry
))
3086 if ((nd
->flags
& LOOKUP_DIRECTORY
) && !d_can_lookup(nd
->path
.dentry
))
3088 if (!d_is_reg(nd
->path
.dentry
))
3089 will_truncate
= false;
3091 if (will_truncate
) {
3092 error
= mnt_want_write(nd
->path
.mnt
);
3097 finish_open_created
:
3098 error
= may_open(&nd
->path
, acc_mode
, open_flag
);
3102 BUG_ON(*opened
& FILE_OPENED
); /* once it's opened, it's opened */
3103 error
= vfs_open(&nd
->path
, file
, current_cred());
3105 *opened
|= FILE_OPENED
;
3107 if (error
== -EOPENSTALE
)
3112 error
= open_check_o_direct(file
);
3115 error
= ima_file_check(file
, op
->acc_mode
, *opened
);
3119 if (will_truncate
) {
3120 error
= handle_truncate(file
);
3126 mnt_drop_write(nd
->path
.mnt
);
3127 path_put(&save_parent
);
3132 path_put_conditional(&path
, nd
);
3139 /* If no saved parent or already retried then can't retry */
3140 if (!save_parent
.dentry
|| retried
)
3143 BUG_ON(save_parent
.dentry
!= dir
);
3144 path_put(&nd
->path
);
3145 nd
->path
= save_parent
;
3146 nd
->inode
= dir
->d_inode
;
3147 save_parent
.mnt
= NULL
;
3148 save_parent
.dentry
= NULL
;
3150 mnt_drop_write(nd
->path
.mnt
);
3157 static int do_tmpfile(int dfd
, struct filename
*pathname
,
3158 struct nameidata
*nd
, int flags
,
3159 const struct open_flags
*op
,
3160 struct file
*file
, int *opened
)
3162 static const struct qstr name
= QSTR_INIT("/", 1);
3163 struct dentry
*dentry
, *child
;
3165 int error
= path_lookupat(dfd
, pathname
,
3166 flags
| LOOKUP_DIRECTORY
, nd
);
3167 if (unlikely(error
))
3169 error
= mnt_want_write(nd
->path
.mnt
);
3170 if (unlikely(error
))
3172 /* we want directory to be writable */
3173 error
= inode_permission(nd
->inode
, MAY_WRITE
| MAY_EXEC
);
3176 dentry
= nd
->path
.dentry
;
3177 dir
= dentry
->d_inode
;
3178 if (!dir
->i_op
->tmpfile
) {
3179 error
= -EOPNOTSUPP
;
3182 child
= d_alloc(dentry
, &name
);
3183 if (unlikely(!child
)) {
3187 nd
->flags
&= ~LOOKUP_DIRECTORY
;
3188 nd
->flags
|= op
->intent
;
3189 dput(nd
->path
.dentry
);
3190 nd
->path
.dentry
= child
;
3191 error
= dir
->i_op
->tmpfile(dir
, nd
->path
.dentry
, op
->mode
);
3194 audit_inode(pathname
, nd
->path
.dentry
, 0);
3195 /* Don't check for other permissions, the inode was just created */
3196 error
= may_open(&nd
->path
, MAY_OPEN
, op
->open_flag
);
3199 file
->f_path
.mnt
= nd
->path
.mnt
;
3200 error
= finish_open(file
, nd
->path
.dentry
, NULL
, opened
);
3203 error
= open_check_o_direct(file
);
3206 } else if (!(op
->open_flag
& O_EXCL
)) {
3207 struct inode
*inode
= file_inode(file
);
3208 spin_lock(&inode
->i_lock
);
3209 inode
->i_state
|= I_LINKABLE
;
3210 spin_unlock(&inode
->i_lock
);
3213 mnt_drop_write(nd
->path
.mnt
);
3215 path_put(&nd
->path
);
3219 static struct file
*path_openat(int dfd
, struct filename
*pathname
,
3220 struct nameidata
*nd
, const struct open_flags
*op
, int flags
)
3226 file
= get_empty_filp();
3230 file
->f_flags
= op
->open_flag
;
3232 if (unlikely(file
->f_flags
& __O_TMPFILE
)) {
3233 error
= do_tmpfile(dfd
, pathname
, nd
, flags
, op
, file
, &opened
);
3237 error
= path_init(dfd
, pathname
, flags
, nd
);
3238 if (unlikely(error
))
3241 error
= do_last(nd
, file
, op
, &opened
, pathname
);
3242 while (unlikely(error
> 0)) { /* trailing symlink */
3243 struct path link
= nd
->link
;
3245 nd
->flags
&= ~(LOOKUP_OPEN
|LOOKUP_CREATE
|LOOKUP_EXCL
);
3246 error
= trailing_symlink(&link
, nd
, &cookie
);
3247 if (unlikely(error
))
3249 error
= do_last(nd
, file
, op
, &opened
, pathname
);
3250 put_link(nd
, &link
, cookie
);
3255 if (!(opened
& FILE_OPENED
)) {
3259 if (unlikely(error
)) {
3260 if (error
== -EOPENSTALE
) {
3261 if (flags
& LOOKUP_RCU
)
3266 file
= ERR_PTR(error
);
3271 struct file
*do_filp_open(int dfd
, struct filename
*pathname
,
3272 const struct open_flags
*op
)
3274 struct nameidata nd
;
3275 int flags
= op
->lookup_flags
;
3278 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
| LOOKUP_RCU
);
3279 if (unlikely(filp
== ERR_PTR(-ECHILD
)))
3280 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
);
3281 if (unlikely(filp
== ERR_PTR(-ESTALE
)))
3282 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
| LOOKUP_REVAL
);
3286 struct file
*do_file_open_root(struct dentry
*dentry
, struct vfsmount
*mnt
,
3287 const char *name
, const struct open_flags
*op
)
3289 struct nameidata nd
;
3291 struct filename
*filename
;
3292 int flags
= op
->lookup_flags
| LOOKUP_ROOT
;
3295 nd
.root
.dentry
= dentry
;
3297 if (d_is_symlink(dentry
) && op
->intent
& LOOKUP_OPEN
)
3298 return ERR_PTR(-ELOOP
);
3300 filename
= getname_kernel(name
);
3301 if (unlikely(IS_ERR(filename
)))
3302 return ERR_CAST(filename
);
3304 file
= path_openat(-1, filename
, &nd
, op
, flags
| LOOKUP_RCU
);
3305 if (unlikely(file
== ERR_PTR(-ECHILD
)))
3306 file
= path_openat(-1, filename
, &nd
, op
, flags
);
3307 if (unlikely(file
== ERR_PTR(-ESTALE
)))
3308 file
= path_openat(-1, filename
, &nd
, op
, flags
| LOOKUP_REVAL
);
3313 static struct dentry
*filename_create(int dfd
, struct filename
*name
,
3314 struct path
*path
, unsigned int lookup_flags
)
3316 struct dentry
*dentry
= ERR_PTR(-EEXIST
);
3317 struct nameidata nd
;
3320 bool is_dir
= (lookup_flags
& LOOKUP_DIRECTORY
);
3323 * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any
3324 * other flags passed in are ignored!
3326 lookup_flags
&= LOOKUP_REVAL
;
3328 error
= filename_lookup(dfd
, name
, LOOKUP_PARENT
|lookup_flags
, &nd
);
3330 return ERR_PTR(error
);
3333 * Yucky last component or no last component at all?
3334 * (foo/., foo/.., /////)
3336 if (nd
.last_type
!= LAST_NORM
)
3338 nd
.flags
&= ~LOOKUP_PARENT
;
3339 nd
.flags
|= LOOKUP_CREATE
| LOOKUP_EXCL
;
3341 /* don't fail immediately if it's r/o, at least try to report other errors */
3342 err2
= mnt_want_write(nd
.path
.mnt
);
3344 * Do the final lookup.
3346 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
3347 dentry
= __lookup_hash(&nd
.last
, nd
.path
.dentry
, nd
.flags
);
3352 if (d_is_positive(dentry
))
3356 * Special case - lookup gave negative, but... we had foo/bar/
3357 * From the vfs_mknod() POV we just have a negative dentry -
3358 * all is fine. Let's be bastards - you had / on the end, you've
3359 * been asking for (non-existent) directory. -ENOENT for you.
3361 if (unlikely(!is_dir
&& nd
.last
.name
[nd
.last
.len
])) {
3365 if (unlikely(err2
)) {
3373 dentry
= ERR_PTR(error
);
3375 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
3377 mnt_drop_write(nd
.path
.mnt
);
3383 struct dentry
*kern_path_create(int dfd
, const char *pathname
,
3384 struct path
*path
, unsigned int lookup_flags
)
3386 struct filename
*filename
= getname_kernel(pathname
);
3389 if (IS_ERR(filename
))
3390 return ERR_CAST(filename
);
3391 res
= filename_create(dfd
, filename
, path
, lookup_flags
);
3395 EXPORT_SYMBOL(kern_path_create
);
3397 void done_path_create(struct path
*path
, struct dentry
*dentry
)
3400 mutex_unlock(&path
->dentry
->d_inode
->i_mutex
);
3401 mnt_drop_write(path
->mnt
);
3404 EXPORT_SYMBOL(done_path_create
);
3406 struct dentry
*user_path_create(int dfd
, const char __user
*pathname
,
3407 struct path
*path
, unsigned int lookup_flags
)
3409 struct filename
*tmp
= getname(pathname
);
3412 return ERR_CAST(tmp
);
3413 res
= filename_create(dfd
, tmp
, path
, lookup_flags
);
3417 EXPORT_SYMBOL(user_path_create
);
3419 int vfs_mknod(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
, dev_t dev
)
3421 int error
= may_create(dir
, dentry
);
3426 if ((S_ISCHR(mode
) || S_ISBLK(mode
)) && !capable(CAP_MKNOD
))
3429 if (!dir
->i_op
->mknod
)
3432 error
= devcgroup_inode_mknod(mode
, dev
);
3436 error
= security_inode_mknod(dir
, dentry
, mode
, dev
);
3440 error
= dir
->i_op
->mknod(dir
, dentry
, mode
, dev
);
3442 fsnotify_create(dir
, dentry
);
3445 EXPORT_SYMBOL(vfs_mknod
);
3447 static int may_mknod(umode_t mode
)
3449 switch (mode
& S_IFMT
) {
3455 case 0: /* zero mode translates to S_IFREG */
3464 SYSCALL_DEFINE4(mknodat
, int, dfd
, const char __user
*, filename
, umode_t
, mode
,
3467 struct dentry
*dentry
;
3470 unsigned int lookup_flags
= 0;
3472 error
= may_mknod(mode
);
3476 dentry
= user_path_create(dfd
, filename
, &path
, lookup_flags
);
3478 return PTR_ERR(dentry
);
3480 if (!IS_POSIXACL(path
.dentry
->d_inode
))
3481 mode
&= ~current_umask();
3482 error
= security_path_mknod(&path
, dentry
, mode
, dev
);
3485 switch (mode
& S_IFMT
) {
3486 case 0: case S_IFREG
:
3487 error
= vfs_create(path
.dentry
->d_inode
,dentry
,mode
,true);
3489 case S_IFCHR
: case S_IFBLK
:
3490 error
= vfs_mknod(path
.dentry
->d_inode
,dentry
,mode
,
3491 new_decode_dev(dev
));
3493 case S_IFIFO
: case S_IFSOCK
:
3494 error
= vfs_mknod(path
.dentry
->d_inode
,dentry
,mode
,0);
3498 done_path_create(&path
, dentry
);
3499 if (retry_estale(error
, lookup_flags
)) {
3500 lookup_flags
|= LOOKUP_REVAL
;
3506 SYSCALL_DEFINE3(mknod
, const char __user
*, filename
, umode_t
, mode
, unsigned, dev
)
3508 return sys_mknodat(AT_FDCWD
, filename
, mode
, dev
);
3511 int vfs_mkdir(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
)
3513 int error
= may_create(dir
, dentry
);
3514 unsigned max_links
= dir
->i_sb
->s_max_links
;
3519 if (!dir
->i_op
->mkdir
)
3522 mode
&= (S_IRWXUGO
|S_ISVTX
);
3523 error
= security_inode_mkdir(dir
, dentry
, mode
);
3527 if (max_links
&& dir
->i_nlink
>= max_links
)
3530 error
= dir
->i_op
->mkdir(dir
, dentry
, mode
);
3532 fsnotify_mkdir(dir
, dentry
);
3535 EXPORT_SYMBOL(vfs_mkdir
);
3537 SYSCALL_DEFINE3(mkdirat
, int, dfd
, const char __user
*, pathname
, umode_t
, mode
)
3539 struct dentry
*dentry
;
3542 unsigned int lookup_flags
= LOOKUP_DIRECTORY
;
3545 dentry
= user_path_create(dfd
, pathname
, &path
, lookup_flags
);
3547 return PTR_ERR(dentry
);
3549 if (!IS_POSIXACL(path
.dentry
->d_inode
))
3550 mode
&= ~current_umask();
3551 error
= security_path_mkdir(&path
, dentry
, mode
);
3553 error
= vfs_mkdir(path
.dentry
->d_inode
, dentry
, mode
);
3554 done_path_create(&path
, dentry
);
3555 if (retry_estale(error
, lookup_flags
)) {
3556 lookup_flags
|= LOOKUP_REVAL
;
3562 SYSCALL_DEFINE2(mkdir
, const char __user
*, pathname
, umode_t
, mode
)
3564 return sys_mkdirat(AT_FDCWD
, pathname
, mode
);
3568 * The dentry_unhash() helper will try to drop the dentry early: we
3569 * should have a usage count of 1 if we're the only user of this
3570 * dentry, and if that is true (possibly after pruning the dcache),
3571 * then we drop the dentry now.
3573 * A low-level filesystem can, if it choses, legally
3576 * if (!d_unhashed(dentry))
3579 * if it cannot handle the case of removing a directory
3580 * that is still in use by something else..
3582 void dentry_unhash(struct dentry
*dentry
)
3584 shrink_dcache_parent(dentry
);
3585 spin_lock(&dentry
->d_lock
);
3586 if (dentry
->d_lockref
.count
== 1)
3588 spin_unlock(&dentry
->d_lock
);
3590 EXPORT_SYMBOL(dentry_unhash
);
3592 int vfs_rmdir(struct inode
*dir
, struct dentry
*dentry
)
3594 int error
= may_delete(dir
, dentry
, 1);
3599 if (!dir
->i_op
->rmdir
)
3603 mutex_lock(&dentry
->d_inode
->i_mutex
);
3606 if (is_local_mountpoint(dentry
))
3609 error
= security_inode_rmdir(dir
, dentry
);
3613 shrink_dcache_parent(dentry
);
3614 error
= dir
->i_op
->rmdir(dir
, dentry
);
3618 dentry
->d_inode
->i_flags
|= S_DEAD
;
3620 detach_mounts(dentry
);
3623 mutex_unlock(&dentry
->d_inode
->i_mutex
);
3629 EXPORT_SYMBOL(vfs_rmdir
);
3631 static long do_rmdir(int dfd
, const char __user
*pathname
)
3634 struct filename
*name
;
3635 struct dentry
*dentry
;
3639 unsigned int lookup_flags
= 0;
3641 name
= user_path_parent(dfd
, pathname
,
3642 &path
, &last
, &type
, lookup_flags
);
3644 return PTR_ERR(name
);
3658 error
= mnt_want_write(path
.mnt
);
3662 mutex_lock_nested(&path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
3663 dentry
= __lookup_hash(&last
, path
.dentry
, lookup_flags
);
3664 error
= PTR_ERR(dentry
);
3667 if (!dentry
->d_inode
) {
3671 error
= security_path_rmdir(&path
, dentry
);
3674 error
= vfs_rmdir(path
.dentry
->d_inode
, dentry
);
3678 mutex_unlock(&path
.dentry
->d_inode
->i_mutex
);
3679 mnt_drop_write(path
.mnt
);
3683 if (retry_estale(error
, lookup_flags
)) {
3684 lookup_flags
|= LOOKUP_REVAL
;
3690 SYSCALL_DEFINE1(rmdir
, const char __user
*, pathname
)
3692 return do_rmdir(AT_FDCWD
, pathname
);
3696 * vfs_unlink - unlink a filesystem object
3697 * @dir: parent directory
3699 * @delegated_inode: returns victim inode, if the inode is delegated.
3701 * The caller must hold dir->i_mutex.
3703 * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and
3704 * return a reference to the inode in delegated_inode. The caller
3705 * should then break the delegation on that inode and retry. Because
3706 * breaking a delegation may take a long time, the caller should drop
3707 * dir->i_mutex before doing so.
3709 * Alternatively, a caller may pass NULL for delegated_inode. This may
3710 * be appropriate for callers that expect the underlying filesystem not
3711 * to be NFS exported.
3713 int vfs_unlink(struct inode
*dir
, struct dentry
*dentry
, struct inode
**delegated_inode
)
3715 struct inode
*target
= dentry
->d_inode
;
3716 int error
= may_delete(dir
, dentry
, 0);
3721 if (!dir
->i_op
->unlink
)
3724 mutex_lock(&target
->i_mutex
);
3725 if (is_local_mountpoint(dentry
))
3728 error
= security_inode_unlink(dir
, dentry
);
3730 error
= try_break_deleg(target
, delegated_inode
);
3733 error
= dir
->i_op
->unlink(dir
, dentry
);
3736 detach_mounts(dentry
);
3741 mutex_unlock(&target
->i_mutex
);
3743 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
3744 if (!error
&& !(dentry
->d_flags
& DCACHE_NFSFS_RENAMED
)) {
3745 fsnotify_link_count(target
);
3751 EXPORT_SYMBOL(vfs_unlink
);
3754 * Make sure that the actual truncation of the file will occur outside its
3755 * directory's i_mutex. Truncate can take a long time if there is a lot of
3756 * writeout happening, and we don't want to prevent access to the directory
3757 * while waiting on the I/O.
3759 static long do_unlinkat(int dfd
, const char __user
*pathname
)
3762 struct filename
*name
;
3763 struct dentry
*dentry
;
3767 struct inode
*inode
= NULL
;
3768 struct inode
*delegated_inode
= NULL
;
3769 unsigned int lookup_flags
= 0;
3771 name
= user_path_parent(dfd
, pathname
,
3772 &path
, &last
, &type
, lookup_flags
);
3774 return PTR_ERR(name
);
3777 if (type
!= LAST_NORM
)
3780 error
= mnt_want_write(path
.mnt
);
3784 mutex_lock_nested(&path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
3785 dentry
= __lookup_hash(&last
, path
.dentry
, lookup_flags
);
3786 error
= PTR_ERR(dentry
);
3787 if (!IS_ERR(dentry
)) {
3788 /* Why not before? Because we want correct error value */
3789 if (last
.name
[last
.len
])
3791 inode
= dentry
->d_inode
;
3792 if (d_is_negative(dentry
))
3795 error
= security_path_unlink(&path
, dentry
);
3798 error
= vfs_unlink(path
.dentry
->d_inode
, dentry
, &delegated_inode
);
3802 mutex_unlock(&path
.dentry
->d_inode
->i_mutex
);
3804 iput(inode
); /* truncate the inode here */
3806 if (delegated_inode
) {
3807 error
= break_deleg_wait(&delegated_inode
);
3811 mnt_drop_write(path
.mnt
);
3815 if (retry_estale(error
, lookup_flags
)) {
3816 lookup_flags
|= LOOKUP_REVAL
;
3823 if (d_is_negative(dentry
))
3825 else if (d_is_dir(dentry
))
3832 SYSCALL_DEFINE3(unlinkat
, int, dfd
, const char __user
*, pathname
, int, flag
)
3834 if ((flag
& ~AT_REMOVEDIR
) != 0)
3837 if (flag
& AT_REMOVEDIR
)
3838 return do_rmdir(dfd
, pathname
);
3840 return do_unlinkat(dfd
, pathname
);
3843 SYSCALL_DEFINE1(unlink
, const char __user
*, pathname
)
3845 return do_unlinkat(AT_FDCWD
, pathname
);
3848 int vfs_symlink(struct inode
*dir
, struct dentry
*dentry
, const char *oldname
)
3850 int error
= may_create(dir
, dentry
);
3855 if (!dir
->i_op
->symlink
)
3858 error
= security_inode_symlink(dir
, dentry
, oldname
);
3862 error
= dir
->i_op
->symlink(dir
, dentry
, oldname
);
3864 fsnotify_create(dir
, dentry
);
3867 EXPORT_SYMBOL(vfs_symlink
);
3869 SYSCALL_DEFINE3(symlinkat
, const char __user
*, oldname
,
3870 int, newdfd
, const char __user
*, newname
)
3873 struct filename
*from
;
3874 struct dentry
*dentry
;
3876 unsigned int lookup_flags
= 0;
3878 from
= getname(oldname
);
3880 return PTR_ERR(from
);
3882 dentry
= user_path_create(newdfd
, newname
, &path
, lookup_flags
);
3883 error
= PTR_ERR(dentry
);
3887 error
= security_path_symlink(&path
, dentry
, from
->name
);
3889 error
= vfs_symlink(path
.dentry
->d_inode
, dentry
, from
->name
);
3890 done_path_create(&path
, dentry
);
3891 if (retry_estale(error
, lookup_flags
)) {
3892 lookup_flags
|= LOOKUP_REVAL
;
3900 SYSCALL_DEFINE2(symlink
, const char __user
*, oldname
, const char __user
*, newname
)
3902 return sys_symlinkat(oldname
, AT_FDCWD
, newname
);
3906 * vfs_link - create a new link
3907 * @old_dentry: object to be linked
3909 * @new_dentry: where to create the new link
3910 * @delegated_inode: returns inode needing a delegation break
3912 * The caller must hold dir->i_mutex
3914 * If vfs_link discovers a delegation on the to-be-linked file in need
3915 * of breaking, it will return -EWOULDBLOCK and return a reference to the
3916 * inode in delegated_inode. The caller should then break the delegation
3917 * and retry. Because breaking a delegation may take a long time, the
3918 * caller should drop the i_mutex before doing so.
3920 * Alternatively, a caller may pass NULL for delegated_inode. This may
3921 * be appropriate for callers that expect the underlying filesystem not
3922 * to be NFS exported.
3924 int vfs_link(struct dentry
*old_dentry
, struct inode
*dir
, struct dentry
*new_dentry
, struct inode
**delegated_inode
)
3926 struct inode
*inode
= old_dentry
->d_inode
;
3927 unsigned max_links
= dir
->i_sb
->s_max_links
;
3933 error
= may_create(dir
, new_dentry
);
3937 if (dir
->i_sb
!= inode
->i_sb
)
3941 * A link to an append-only or immutable file cannot be created.
3943 if (IS_APPEND(inode
) || IS_IMMUTABLE(inode
))
3945 if (!dir
->i_op
->link
)
3947 if (S_ISDIR(inode
->i_mode
))
3950 error
= security_inode_link(old_dentry
, dir
, new_dentry
);
3954 mutex_lock(&inode
->i_mutex
);
3955 /* Make sure we don't allow creating hardlink to an unlinked file */
3956 if (inode
->i_nlink
== 0 && !(inode
->i_state
& I_LINKABLE
))
3958 else if (max_links
&& inode
->i_nlink
>= max_links
)
3961 error
= try_break_deleg(inode
, delegated_inode
);
3963 error
= dir
->i_op
->link(old_dentry
, dir
, new_dentry
);
3966 if (!error
&& (inode
->i_state
& I_LINKABLE
)) {
3967 spin_lock(&inode
->i_lock
);
3968 inode
->i_state
&= ~I_LINKABLE
;
3969 spin_unlock(&inode
->i_lock
);
3971 mutex_unlock(&inode
->i_mutex
);
3973 fsnotify_link(dir
, inode
, new_dentry
);
3976 EXPORT_SYMBOL(vfs_link
);
3979 * Hardlinks are often used in delicate situations. We avoid
3980 * security-related surprises by not following symlinks on the
3983 * We don't follow them on the oldname either to be compatible
3984 * with linux 2.0, and to avoid hard-linking to directories
3985 * and other special files. --ADM
3987 SYSCALL_DEFINE5(linkat
, int, olddfd
, const char __user
*, oldname
,
3988 int, newdfd
, const char __user
*, newname
, int, flags
)
3990 struct dentry
*new_dentry
;
3991 struct path old_path
, new_path
;
3992 struct inode
*delegated_inode
= NULL
;
3996 if ((flags
& ~(AT_SYMLINK_FOLLOW
| AT_EMPTY_PATH
)) != 0)
3999 * To use null names we require CAP_DAC_READ_SEARCH
4000 * This ensures that not everyone will be able to create
4001 * handlink using the passed filedescriptor.
4003 if (flags
& AT_EMPTY_PATH
) {
4004 if (!capable(CAP_DAC_READ_SEARCH
))
4009 if (flags
& AT_SYMLINK_FOLLOW
)
4010 how
|= LOOKUP_FOLLOW
;
4012 error
= user_path_at(olddfd
, oldname
, how
, &old_path
);
4016 new_dentry
= user_path_create(newdfd
, newname
, &new_path
,
4017 (how
& LOOKUP_REVAL
));
4018 error
= PTR_ERR(new_dentry
);
4019 if (IS_ERR(new_dentry
))
4023 if (old_path
.mnt
!= new_path
.mnt
)
4025 error
= may_linkat(&old_path
);
4026 if (unlikely(error
))
4028 error
= security_path_link(old_path
.dentry
, &new_path
, new_dentry
);
4031 error
= vfs_link(old_path
.dentry
, new_path
.dentry
->d_inode
, new_dentry
, &delegated_inode
);
4033 done_path_create(&new_path
, new_dentry
);
4034 if (delegated_inode
) {
4035 error
= break_deleg_wait(&delegated_inode
);
4037 path_put(&old_path
);
4041 if (retry_estale(error
, how
)) {
4042 path_put(&old_path
);
4043 how
|= LOOKUP_REVAL
;
4047 path_put(&old_path
);
4052 SYSCALL_DEFINE2(link
, const char __user
*, oldname
, const char __user
*, newname
)
4054 return sys_linkat(AT_FDCWD
, oldname
, AT_FDCWD
, newname
, 0);
4058 * vfs_rename - rename a filesystem object
4059 * @old_dir: parent of source
4060 * @old_dentry: source
4061 * @new_dir: parent of destination
4062 * @new_dentry: destination
4063 * @delegated_inode: returns an inode needing a delegation break
4064 * @flags: rename flags
4066 * The caller must hold multiple mutexes--see lock_rename()).
4068 * If vfs_rename discovers a delegation in need of breaking at either
4069 * the source or destination, it will return -EWOULDBLOCK and return a
4070 * reference to the inode in delegated_inode. The caller should then
4071 * break the delegation and retry. Because breaking a delegation may
4072 * take a long time, the caller should drop all locks before doing
4075 * Alternatively, a caller may pass NULL for delegated_inode. This may
4076 * be appropriate for callers that expect the underlying filesystem not
4077 * to be NFS exported.
4079 * The worst of all namespace operations - renaming directory. "Perverted"
4080 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
4082 * a) we can get into loop creation.
4083 * b) race potential - two innocent renames can create a loop together.
4084 * That's where 4.4 screws up. Current fix: serialization on
4085 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
4087 * c) we have to lock _four_ objects - parents and victim (if it exists),
4088 * and source (if it is not a directory).
4089 * And that - after we got ->i_mutex on parents (until then we don't know
4090 * whether the target exists). Solution: try to be smart with locking
4091 * order for inodes. We rely on the fact that tree topology may change
4092 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
4093 * move will be locked. Thus we can rank directories by the tree
4094 * (ancestors first) and rank all non-directories after them.
4095 * That works since everybody except rename does "lock parent, lookup,
4096 * lock child" and rename is under ->s_vfs_rename_mutex.
4097 * HOWEVER, it relies on the assumption that any object with ->lookup()
4098 * has no more than 1 dentry. If "hybrid" objects will ever appear,
4099 * we'd better make sure that there's no link(2) for them.
4100 * d) conversion from fhandle to dentry may come in the wrong moment - when
4101 * we are removing the target. Solution: we will have to grab ->i_mutex
4102 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
4103 * ->i_mutex on parents, which works but leads to some truly excessive
4106 int vfs_rename(struct inode
*old_dir
, struct dentry
*old_dentry
,
4107 struct inode
*new_dir
, struct dentry
*new_dentry
,
4108 struct inode
**delegated_inode
, unsigned int flags
)
4111 bool is_dir
= d_is_dir(old_dentry
);
4112 const unsigned char *old_name
;
4113 struct inode
*source
= old_dentry
->d_inode
;
4114 struct inode
*target
= new_dentry
->d_inode
;
4115 bool new_is_dir
= false;
4116 unsigned max_links
= new_dir
->i_sb
->s_max_links
;
4118 if (source
== target
)
4121 error
= may_delete(old_dir
, old_dentry
, is_dir
);
4126 error
= may_create(new_dir
, new_dentry
);
4128 new_is_dir
= d_is_dir(new_dentry
);
4130 if (!(flags
& RENAME_EXCHANGE
))
4131 error
= may_delete(new_dir
, new_dentry
, is_dir
);
4133 error
= may_delete(new_dir
, new_dentry
, new_is_dir
);
4138 if (!old_dir
->i_op
->rename
&& !old_dir
->i_op
->rename2
)
4141 if (flags
&& !old_dir
->i_op
->rename2
)
4145 * If we are going to change the parent - check write permissions,
4146 * we'll need to flip '..'.
4148 if (new_dir
!= old_dir
) {
4150 error
= inode_permission(source
, MAY_WRITE
);
4154 if ((flags
& RENAME_EXCHANGE
) && new_is_dir
) {
4155 error
= inode_permission(target
, MAY_WRITE
);
4161 error
= security_inode_rename(old_dir
, old_dentry
, new_dir
, new_dentry
,
4166 old_name
= fsnotify_oldname_init(old_dentry
->d_name
.name
);
4168 if (!is_dir
|| (flags
& RENAME_EXCHANGE
))
4169 lock_two_nondirectories(source
, target
);
4171 mutex_lock(&target
->i_mutex
);
4174 if (is_local_mountpoint(old_dentry
) || is_local_mountpoint(new_dentry
))
4177 if (max_links
&& new_dir
!= old_dir
) {
4179 if (is_dir
&& !new_is_dir
&& new_dir
->i_nlink
>= max_links
)
4181 if ((flags
& RENAME_EXCHANGE
) && !is_dir
&& new_is_dir
&&
4182 old_dir
->i_nlink
>= max_links
)
4185 if (is_dir
&& !(flags
& RENAME_EXCHANGE
) && target
)
4186 shrink_dcache_parent(new_dentry
);
4188 error
= try_break_deleg(source
, delegated_inode
);
4192 if (target
&& !new_is_dir
) {
4193 error
= try_break_deleg(target
, delegated_inode
);
4197 if (!old_dir
->i_op
->rename2
) {
4198 error
= old_dir
->i_op
->rename(old_dir
, old_dentry
,
4199 new_dir
, new_dentry
);
4201 WARN_ON(old_dir
->i_op
->rename
!= NULL
);
4202 error
= old_dir
->i_op
->rename2(old_dir
, old_dentry
,
4203 new_dir
, new_dentry
, flags
);
4208 if (!(flags
& RENAME_EXCHANGE
) && target
) {
4210 target
->i_flags
|= S_DEAD
;
4211 dont_mount(new_dentry
);
4212 detach_mounts(new_dentry
);
4214 if (!(old_dir
->i_sb
->s_type
->fs_flags
& FS_RENAME_DOES_D_MOVE
)) {
4215 if (!(flags
& RENAME_EXCHANGE
))
4216 d_move(old_dentry
, new_dentry
);
4218 d_exchange(old_dentry
, new_dentry
);
4221 if (!is_dir
|| (flags
& RENAME_EXCHANGE
))
4222 unlock_two_nondirectories(source
, target
);
4224 mutex_unlock(&target
->i_mutex
);
4227 fsnotify_move(old_dir
, new_dir
, old_name
, is_dir
,
4228 !(flags
& RENAME_EXCHANGE
) ? target
: NULL
, old_dentry
);
4229 if (flags
& RENAME_EXCHANGE
) {
4230 fsnotify_move(new_dir
, old_dir
, old_dentry
->d_name
.name
,
4231 new_is_dir
, NULL
, new_dentry
);
4234 fsnotify_oldname_free(old_name
);
4238 EXPORT_SYMBOL(vfs_rename
);
4240 SYSCALL_DEFINE5(renameat2
, int, olddfd
, const char __user
*, oldname
,
4241 int, newdfd
, const char __user
*, newname
, unsigned int, flags
)
4243 struct dentry
*old_dentry
, *new_dentry
;
4244 struct dentry
*trap
;
4245 struct path old_path
, new_path
;
4246 struct qstr old_last
, new_last
;
4247 int old_type
, new_type
;
4248 struct inode
*delegated_inode
= NULL
;
4249 struct filename
*from
;
4250 struct filename
*to
;
4251 unsigned int lookup_flags
= 0, target_flags
= LOOKUP_RENAME_TARGET
;
4252 bool should_retry
= false;
4255 if (flags
& ~(RENAME_NOREPLACE
| RENAME_EXCHANGE
| RENAME_WHITEOUT
))
4258 if ((flags
& (RENAME_NOREPLACE
| RENAME_WHITEOUT
)) &&
4259 (flags
& RENAME_EXCHANGE
))
4262 if ((flags
& RENAME_WHITEOUT
) && !capable(CAP_MKNOD
))
4265 if (flags
& RENAME_EXCHANGE
)
4269 from
= user_path_parent(olddfd
, oldname
,
4270 &old_path
, &old_last
, &old_type
, lookup_flags
);
4272 error
= PTR_ERR(from
);
4276 to
= user_path_parent(newdfd
, newname
,
4277 &new_path
, &new_last
, &new_type
, lookup_flags
);
4279 error
= PTR_ERR(to
);
4284 if (old_path
.mnt
!= new_path
.mnt
)
4288 if (old_type
!= LAST_NORM
)
4291 if (flags
& RENAME_NOREPLACE
)
4293 if (new_type
!= LAST_NORM
)
4296 error
= mnt_want_write(old_path
.mnt
);
4301 trap
= lock_rename(new_path
.dentry
, old_path
.dentry
);
4303 old_dentry
= __lookup_hash(&old_last
, old_path
.dentry
, lookup_flags
);
4304 error
= PTR_ERR(old_dentry
);
4305 if (IS_ERR(old_dentry
))
4307 /* source must exist */
4309 if (d_is_negative(old_dentry
))
4311 new_dentry
= __lookup_hash(&new_last
, new_path
.dentry
, lookup_flags
| target_flags
);
4312 error
= PTR_ERR(new_dentry
);
4313 if (IS_ERR(new_dentry
))
4316 if ((flags
& RENAME_NOREPLACE
) && d_is_positive(new_dentry
))
4318 if (flags
& RENAME_EXCHANGE
) {
4320 if (d_is_negative(new_dentry
))
4323 if (!d_is_dir(new_dentry
)) {
4325 if (new_last
.name
[new_last
.len
])
4329 /* unless the source is a directory trailing slashes give -ENOTDIR */
4330 if (!d_is_dir(old_dentry
)) {
4332 if (old_last
.name
[old_last
.len
])
4334 if (!(flags
& RENAME_EXCHANGE
) && new_last
.name
[new_last
.len
])
4337 /* source should not be ancestor of target */
4339 if (old_dentry
== trap
)
4341 /* target should not be an ancestor of source */
4342 if (!(flags
& RENAME_EXCHANGE
))
4344 if (new_dentry
== trap
)
4347 error
= security_path_rename(&old_path
, old_dentry
,
4348 &new_path
, new_dentry
, flags
);
4351 error
= vfs_rename(old_path
.dentry
->d_inode
, old_dentry
,
4352 new_path
.dentry
->d_inode
, new_dentry
,
4353 &delegated_inode
, flags
);
4359 unlock_rename(new_path
.dentry
, old_path
.dentry
);
4360 if (delegated_inode
) {
4361 error
= break_deleg_wait(&delegated_inode
);
4365 mnt_drop_write(old_path
.mnt
);
4367 if (retry_estale(error
, lookup_flags
))
4368 should_retry
= true;
4369 path_put(&new_path
);
4372 path_put(&old_path
);
4375 should_retry
= false;
4376 lookup_flags
|= LOOKUP_REVAL
;
4383 SYSCALL_DEFINE4(renameat
, int, olddfd
, const char __user
*, oldname
,
4384 int, newdfd
, const char __user
*, newname
)
4386 return sys_renameat2(olddfd
, oldname
, newdfd
, newname
, 0);
4389 SYSCALL_DEFINE2(rename
, const char __user
*, oldname
, const char __user
*, newname
)
4391 return sys_renameat2(AT_FDCWD
, oldname
, AT_FDCWD
, newname
, 0);
4394 int vfs_whiteout(struct inode
*dir
, struct dentry
*dentry
)
4396 int error
= may_create(dir
, dentry
);
4400 if (!dir
->i_op
->mknod
)
4403 return dir
->i_op
->mknod(dir
, dentry
,
4404 S_IFCHR
| WHITEOUT_MODE
, WHITEOUT_DEV
);
4406 EXPORT_SYMBOL(vfs_whiteout
);
4408 int readlink_copy(char __user
*buffer
, int buflen
, const char *link
)
4410 int len
= PTR_ERR(link
);
4415 if (len
> (unsigned) buflen
)
4417 if (copy_to_user(buffer
, link
, len
))
4422 EXPORT_SYMBOL(readlink_copy
);
4425 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
4426 * have ->follow_link() touching nd only in nd_set_link(). Using (or not
4427 * using) it for any given inode is up to filesystem.
4429 int generic_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
)
4432 const char *link
= dentry
->d_inode
->i_link
;
4436 link
= dentry
->d_inode
->i_op
->follow_link(dentry
, &cookie
, NULL
);
4438 return PTR_ERR(link
);
4440 res
= readlink_copy(buffer
, buflen
, link
);
4441 if (cookie
&& dentry
->d_inode
->i_op
->put_link
)
4442 dentry
->d_inode
->i_op
->put_link(dentry
, cookie
);
4445 EXPORT_SYMBOL(generic_readlink
);
4447 /* get the link contents into pagecache */
4448 static char *page_getlink(struct dentry
* dentry
, struct page
**ppage
)
4452 struct address_space
*mapping
= dentry
->d_inode
->i_mapping
;
4453 page
= read_mapping_page(mapping
, 0, NULL
);
4458 nd_terminate_link(kaddr
, dentry
->d_inode
->i_size
, PAGE_SIZE
- 1);
4462 int page_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
)
4464 struct page
*page
= NULL
;
4465 int res
= readlink_copy(buffer
, buflen
, page_getlink(dentry
, &page
));
4468 page_cache_release(page
);
4472 EXPORT_SYMBOL(page_readlink
);
4474 const char *page_follow_link_light(struct dentry
*dentry
, void **cookie
, struct nameidata
*nd
)
4476 struct page
*page
= NULL
;
4477 char *res
= page_getlink(dentry
, &page
);
4482 EXPORT_SYMBOL(page_follow_link_light
);
4484 void page_put_link(struct dentry
*dentry
, void *cookie
)
4486 struct page
*page
= cookie
;
4488 page_cache_release(page
);
4490 EXPORT_SYMBOL(page_put_link
);
4493 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
4495 int __page_symlink(struct inode
*inode
, const char *symname
, int len
, int nofs
)
4497 struct address_space
*mapping
= inode
->i_mapping
;
4502 unsigned int flags
= AOP_FLAG_UNINTERRUPTIBLE
;
4504 flags
|= AOP_FLAG_NOFS
;
4507 err
= pagecache_write_begin(NULL
, mapping
, 0, len
-1,
4508 flags
, &page
, &fsdata
);
4512 kaddr
= kmap_atomic(page
);
4513 memcpy(kaddr
, symname
, len
-1);
4514 kunmap_atomic(kaddr
);
4516 err
= pagecache_write_end(NULL
, mapping
, 0, len
-1, len
-1,
4523 mark_inode_dirty(inode
);
4528 EXPORT_SYMBOL(__page_symlink
);
4530 int page_symlink(struct inode
*inode
, const char *symname
, int len
)
4532 return __page_symlink(inode
, symname
, len
,
4533 !(mapping_gfp_mask(inode
->i_mapping
) & __GFP_FS
));
4535 EXPORT_SYMBOL(page_symlink
);
4537 const struct inode_operations page_symlink_inode_operations
= {
4538 .readlink
= generic_readlink
,
4539 .follow_link
= page_follow_link_light
,
4540 .put_link
= page_put_link
,
4542 EXPORT_SYMBOL(page_symlink_inode_operations
);