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 int link_path_walk(const char *, struct nameidata
*);
673 static __always_inline
unsigned set_root_rcu(struct nameidata
*nd
)
675 struct fs_struct
*fs
= current
->fs
;
679 seq
= read_seqcount_begin(&fs
->seq
);
681 res
= __read_seqcount_begin(&nd
->root
.dentry
->d_seq
);
682 } while (read_seqcount_retry(&fs
->seq
, seq
));
686 static void path_put_conditional(struct path
*path
, struct nameidata
*nd
)
689 if (path
->mnt
!= nd
->path
.mnt
)
693 static inline void path_to_nameidata(const struct path
*path
,
694 struct nameidata
*nd
)
696 if (!(nd
->flags
& LOOKUP_RCU
)) {
697 dput(nd
->path
.dentry
);
698 if (nd
->path
.mnt
!= path
->mnt
)
699 mntput(nd
->path
.mnt
);
701 nd
->path
.mnt
= path
->mnt
;
702 nd
->path
.dentry
= path
->dentry
;
706 * Helper to directly jump to a known parsed path from ->follow_link,
707 * caller must have taken a reference to path beforehand.
709 void nd_jump_link(struct nameidata
*nd
, struct path
*path
)
714 nd
->inode
= nd
->path
.dentry
->d_inode
;
715 nd
->flags
|= LOOKUP_JUMPED
;
718 static inline void put_link(struct nameidata
*nd
, struct path
*link
, void *cookie
)
720 struct inode
*inode
= link
->dentry
->d_inode
;
721 if (cookie
&& inode
->i_op
->put_link
)
722 inode
->i_op
->put_link(link
->dentry
, cookie
);
726 int sysctl_protected_symlinks __read_mostly
= 0;
727 int sysctl_protected_hardlinks __read_mostly
= 0;
730 * may_follow_link - Check symlink following for unsafe situations
731 * @link: The path of the symlink
732 * @nd: nameidata pathwalk data
734 * In the case of the sysctl_protected_symlinks sysctl being enabled,
735 * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
736 * in a sticky world-writable directory. This is to protect privileged
737 * processes from failing races against path names that may change out
738 * from under them by way of other users creating malicious symlinks.
739 * It will permit symlinks to be followed only when outside a sticky
740 * world-writable directory, or when the uid of the symlink and follower
741 * match, or when the directory owner matches the symlink's owner.
743 * Returns 0 if following the symlink is allowed, -ve on error.
745 static inline int may_follow_link(struct path
*link
, struct nameidata
*nd
)
747 const struct inode
*inode
;
748 const struct inode
*parent
;
750 if (!sysctl_protected_symlinks
)
753 /* Allowed if owner and follower match. */
754 inode
= link
->dentry
->d_inode
;
755 if (uid_eq(current_cred()->fsuid
, inode
->i_uid
))
758 /* Allowed if parent directory not sticky and world-writable. */
759 parent
= nd
->path
.dentry
->d_inode
;
760 if ((parent
->i_mode
& (S_ISVTX
|S_IWOTH
)) != (S_ISVTX
|S_IWOTH
))
763 /* Allowed if parent directory and link owner match. */
764 if (uid_eq(parent
->i_uid
, inode
->i_uid
))
767 audit_log_link_denied("follow_link", link
);
768 path_put_conditional(link
, nd
);
774 * safe_hardlink_source - Check for safe hardlink conditions
775 * @inode: the source inode to hardlink from
777 * Return false if at least one of the following conditions:
778 * - inode is not a regular file
780 * - inode is setgid and group-exec
781 * - access failure for read and write
783 * Otherwise returns true.
785 static bool safe_hardlink_source(struct inode
*inode
)
787 umode_t mode
= inode
->i_mode
;
789 /* Special files should not get pinned to the filesystem. */
793 /* Setuid files should not get pinned to the filesystem. */
797 /* Executable setgid files should not get pinned to the filesystem. */
798 if ((mode
& (S_ISGID
| S_IXGRP
)) == (S_ISGID
| S_IXGRP
))
801 /* Hardlinking to unreadable or unwritable sources is dangerous. */
802 if (inode_permission(inode
, MAY_READ
| MAY_WRITE
))
809 * may_linkat - Check permissions for creating a hardlink
810 * @link: the source to hardlink from
812 * Block hardlink when all of:
813 * - sysctl_protected_hardlinks enabled
814 * - fsuid does not match inode
815 * - hardlink source is unsafe (see safe_hardlink_source() above)
818 * Returns 0 if successful, -ve on error.
820 static int may_linkat(struct path
*link
)
822 const struct cred
*cred
;
825 if (!sysctl_protected_hardlinks
)
828 cred
= current_cred();
829 inode
= link
->dentry
->d_inode
;
831 /* Source inode owner (or CAP_FOWNER) can hardlink all they like,
832 * otherwise, it must be a safe source.
834 if (uid_eq(cred
->fsuid
, inode
->i_uid
) || safe_hardlink_source(inode
) ||
838 audit_log_link_denied("linkat", link
);
842 static __always_inline
const char *
843 get_link(struct path
*link
, struct nameidata
*nd
, void **p
)
845 struct dentry
*dentry
= link
->dentry
;
846 struct inode
*inode
= dentry
->d_inode
;
850 BUG_ON(nd
->flags
& LOOKUP_RCU
);
852 if (link
->mnt
== nd
->path
.mnt
)
855 res
= ERR_PTR(-ELOOP
);
856 if (unlikely(current
->total_link_count
>= 40))
860 current
->total_link_count
++;
864 error
= security_inode_follow_link(dentry
);
865 res
= ERR_PTR(error
);
869 nd
->last_type
= LAST_BIND
;
873 res
= inode
->i_op
->follow_link(dentry
, p
, nd
);
883 static __always_inline
int
884 follow_link(struct path
*link
, struct nameidata
*nd
, void **p
)
886 const char *s
= get_link(link
, nd
, p
);
889 if (unlikely(IS_ERR(s
)))
899 nd
->flags
|= LOOKUP_JUMPED
;
901 nd
->inode
= nd
->path
.dentry
->d_inode
;
902 error
= link_path_walk(s
, nd
);
904 put_link(nd
, link
, *p
);
908 static int follow_up_rcu(struct path
*path
)
910 struct mount
*mnt
= real_mount(path
->mnt
);
911 struct mount
*parent
;
912 struct dentry
*mountpoint
;
914 parent
= mnt
->mnt_parent
;
915 if (&parent
->mnt
== path
->mnt
)
917 mountpoint
= mnt
->mnt_mountpoint
;
918 path
->dentry
= mountpoint
;
919 path
->mnt
= &parent
->mnt
;
924 * follow_up - Find the mountpoint of path's vfsmount
926 * Given a path, find the mountpoint of its source file system.
927 * Replace @path with the path of the mountpoint in the parent mount.
930 * Return 1 if we went up a level and 0 if we were already at the
933 int follow_up(struct path
*path
)
935 struct mount
*mnt
= real_mount(path
->mnt
);
936 struct mount
*parent
;
937 struct dentry
*mountpoint
;
939 read_seqlock_excl(&mount_lock
);
940 parent
= mnt
->mnt_parent
;
942 read_sequnlock_excl(&mount_lock
);
945 mntget(&parent
->mnt
);
946 mountpoint
= dget(mnt
->mnt_mountpoint
);
947 read_sequnlock_excl(&mount_lock
);
949 path
->dentry
= mountpoint
;
951 path
->mnt
= &parent
->mnt
;
954 EXPORT_SYMBOL(follow_up
);
957 * Perform an automount
958 * - return -EISDIR to tell follow_managed() to stop and return the path we
961 static int follow_automount(struct path
*path
, unsigned flags
,
964 struct vfsmount
*mnt
;
967 if (!path
->dentry
->d_op
|| !path
->dentry
->d_op
->d_automount
)
970 /* We don't want to mount if someone's just doing a stat -
971 * unless they're stat'ing a directory and appended a '/' to
974 * We do, however, want to mount if someone wants to open or
975 * create a file of any type under the mountpoint, wants to
976 * traverse through the mountpoint or wants to open the
977 * mounted directory. Also, autofs may mark negative dentries
978 * as being automount points. These will need the attentions
979 * of the daemon to instantiate them before they can be used.
981 if (!(flags
& (LOOKUP_PARENT
| LOOKUP_DIRECTORY
|
982 LOOKUP_OPEN
| LOOKUP_CREATE
| LOOKUP_AUTOMOUNT
)) &&
983 path
->dentry
->d_inode
)
986 current
->total_link_count
++;
987 if (current
->total_link_count
>= 40)
990 mnt
= path
->dentry
->d_op
->d_automount(path
);
993 * The filesystem is allowed to return -EISDIR here to indicate
994 * it doesn't want to automount. For instance, autofs would do
995 * this so that its userspace daemon can mount on this dentry.
997 * However, we can only permit this if it's a terminal point in
998 * the path being looked up; if it wasn't then the remainder of
999 * the path is inaccessible and we should say so.
1001 if (PTR_ERR(mnt
) == -EISDIR
&& (flags
& LOOKUP_PARENT
))
1003 return PTR_ERR(mnt
);
1006 if (!mnt
) /* mount collision */
1009 if (!*need_mntput
) {
1010 /* lock_mount() may release path->mnt on error */
1012 *need_mntput
= true;
1014 err
= finish_automount(mnt
, path
);
1018 /* Someone else made a mount here whilst we were busy */
1023 path
->dentry
= dget(mnt
->mnt_root
);
1032 * Handle a dentry that is managed in some way.
1033 * - Flagged for transit management (autofs)
1034 * - Flagged as mountpoint
1035 * - Flagged as automount point
1037 * This may only be called in refwalk mode.
1039 * Serialization is taken care of in namespace.c
1041 static int follow_managed(struct path
*path
, unsigned flags
)
1043 struct vfsmount
*mnt
= path
->mnt
; /* held by caller, must be left alone */
1045 bool need_mntput
= false;
1048 /* Given that we're not holding a lock here, we retain the value in a
1049 * local variable for each dentry as we look at it so that we don't see
1050 * the components of that value change under us */
1051 while (managed
= ACCESS_ONCE(path
->dentry
->d_flags
),
1052 managed
&= DCACHE_MANAGED_DENTRY
,
1053 unlikely(managed
!= 0)) {
1054 /* Allow the filesystem to manage the transit without i_mutex
1056 if (managed
& DCACHE_MANAGE_TRANSIT
) {
1057 BUG_ON(!path
->dentry
->d_op
);
1058 BUG_ON(!path
->dentry
->d_op
->d_manage
);
1059 ret
= path
->dentry
->d_op
->d_manage(path
->dentry
, false);
1064 /* Transit to a mounted filesystem. */
1065 if (managed
& DCACHE_MOUNTED
) {
1066 struct vfsmount
*mounted
= lookup_mnt(path
);
1071 path
->mnt
= mounted
;
1072 path
->dentry
= dget(mounted
->mnt_root
);
1077 /* Something is mounted on this dentry in another
1078 * namespace and/or whatever was mounted there in this
1079 * namespace got unmounted before lookup_mnt() could
1083 /* Handle an automount point */
1084 if (managed
& DCACHE_NEED_AUTOMOUNT
) {
1085 ret
= follow_automount(path
, flags
, &need_mntput
);
1091 /* We didn't change the current path point */
1095 if (need_mntput
&& path
->mnt
== mnt
)
1099 return ret
< 0 ? ret
: need_mntput
;
1102 int follow_down_one(struct path
*path
)
1104 struct vfsmount
*mounted
;
1106 mounted
= lookup_mnt(path
);
1110 path
->mnt
= mounted
;
1111 path
->dentry
= dget(mounted
->mnt_root
);
1116 EXPORT_SYMBOL(follow_down_one
);
1118 static inline int managed_dentry_rcu(struct dentry
*dentry
)
1120 return (dentry
->d_flags
& DCACHE_MANAGE_TRANSIT
) ?
1121 dentry
->d_op
->d_manage(dentry
, true) : 0;
1125 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
1126 * we meet a managed dentry that would need blocking.
1128 static bool __follow_mount_rcu(struct nameidata
*nd
, struct path
*path
,
1129 struct inode
**inode
)
1132 struct mount
*mounted
;
1134 * Don't forget we might have a non-mountpoint managed dentry
1135 * that wants to block transit.
1137 switch (managed_dentry_rcu(path
->dentry
)) {
1147 if (!d_mountpoint(path
->dentry
))
1148 return !(path
->dentry
->d_flags
& DCACHE_NEED_AUTOMOUNT
);
1150 mounted
= __lookup_mnt(path
->mnt
, path
->dentry
);
1153 path
->mnt
= &mounted
->mnt
;
1154 path
->dentry
= mounted
->mnt
.mnt_root
;
1155 nd
->flags
|= LOOKUP_JUMPED
;
1156 nd
->seq
= read_seqcount_begin(&path
->dentry
->d_seq
);
1158 * Update the inode too. We don't need to re-check the
1159 * dentry sequence number here after this d_inode read,
1160 * because a mount-point is always pinned.
1162 *inode
= path
->dentry
->d_inode
;
1164 return !read_seqretry(&mount_lock
, nd
->m_seq
) &&
1165 !(path
->dentry
->d_flags
& DCACHE_NEED_AUTOMOUNT
);
1168 static int follow_dotdot_rcu(struct nameidata
*nd
)
1170 struct inode
*inode
= nd
->inode
;
1175 if (nd
->path
.dentry
== nd
->root
.dentry
&&
1176 nd
->path
.mnt
== nd
->root
.mnt
) {
1179 if (nd
->path
.dentry
!= nd
->path
.mnt
->mnt_root
) {
1180 struct dentry
*old
= nd
->path
.dentry
;
1181 struct dentry
*parent
= old
->d_parent
;
1184 inode
= parent
->d_inode
;
1185 seq
= read_seqcount_begin(&parent
->d_seq
);
1186 if (read_seqcount_retry(&old
->d_seq
, nd
->seq
))
1188 nd
->path
.dentry
= parent
;
1192 if (!follow_up_rcu(&nd
->path
))
1194 inode
= nd
->path
.dentry
->d_inode
;
1195 nd
->seq
= read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1197 while (d_mountpoint(nd
->path
.dentry
)) {
1198 struct mount
*mounted
;
1199 mounted
= __lookup_mnt(nd
->path
.mnt
, nd
->path
.dentry
);
1202 nd
->path
.mnt
= &mounted
->mnt
;
1203 nd
->path
.dentry
= mounted
->mnt
.mnt_root
;
1204 inode
= nd
->path
.dentry
->d_inode
;
1205 nd
->seq
= read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1206 if (read_seqretry(&mount_lock
, nd
->m_seq
))
1213 nd
->flags
&= ~LOOKUP_RCU
;
1214 if (!(nd
->flags
& LOOKUP_ROOT
))
1215 nd
->root
.mnt
= NULL
;
1221 * Follow down to the covering mount currently visible to userspace. At each
1222 * point, the filesystem owning that dentry may be queried as to whether the
1223 * caller is permitted to proceed or not.
1225 int follow_down(struct path
*path
)
1230 while (managed
= ACCESS_ONCE(path
->dentry
->d_flags
),
1231 unlikely(managed
& DCACHE_MANAGED_DENTRY
)) {
1232 /* Allow the filesystem to manage the transit without i_mutex
1235 * We indicate to the filesystem if someone is trying to mount
1236 * something here. This gives autofs the chance to deny anyone
1237 * other than its daemon the right to mount on its
1240 * The filesystem may sleep at this point.
1242 if (managed
& DCACHE_MANAGE_TRANSIT
) {
1243 BUG_ON(!path
->dentry
->d_op
);
1244 BUG_ON(!path
->dentry
->d_op
->d_manage
);
1245 ret
= path
->dentry
->d_op
->d_manage(
1246 path
->dentry
, false);
1248 return ret
== -EISDIR
? 0 : ret
;
1251 /* Transit to a mounted filesystem. */
1252 if (managed
& DCACHE_MOUNTED
) {
1253 struct vfsmount
*mounted
= lookup_mnt(path
);
1258 path
->mnt
= mounted
;
1259 path
->dentry
= dget(mounted
->mnt_root
);
1263 /* Don't handle automount points here */
1268 EXPORT_SYMBOL(follow_down
);
1271 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1273 static void follow_mount(struct path
*path
)
1275 while (d_mountpoint(path
->dentry
)) {
1276 struct vfsmount
*mounted
= lookup_mnt(path
);
1281 path
->mnt
= mounted
;
1282 path
->dentry
= dget(mounted
->mnt_root
);
1286 static void follow_dotdot(struct nameidata
*nd
)
1292 struct dentry
*old
= nd
->path
.dentry
;
1294 if (nd
->path
.dentry
== nd
->root
.dentry
&&
1295 nd
->path
.mnt
== nd
->root
.mnt
) {
1298 if (nd
->path
.dentry
!= nd
->path
.mnt
->mnt_root
) {
1299 /* rare case of legitimate dget_parent()... */
1300 nd
->path
.dentry
= dget_parent(nd
->path
.dentry
);
1304 if (!follow_up(&nd
->path
))
1307 follow_mount(&nd
->path
);
1308 nd
->inode
= nd
->path
.dentry
->d_inode
;
1312 * This looks up the name in dcache, possibly revalidates the old dentry and
1313 * allocates a new one if not found or not valid. In the need_lookup argument
1314 * returns whether i_op->lookup is necessary.
1316 * dir->d_inode->i_mutex must be held
1318 static struct dentry
*lookup_dcache(struct qstr
*name
, struct dentry
*dir
,
1319 unsigned int flags
, bool *need_lookup
)
1321 struct dentry
*dentry
;
1324 *need_lookup
= false;
1325 dentry
= d_lookup(dir
, name
);
1327 if (dentry
->d_flags
& DCACHE_OP_REVALIDATE
) {
1328 error
= d_revalidate(dentry
, flags
);
1329 if (unlikely(error
<= 0)) {
1332 return ERR_PTR(error
);
1334 d_invalidate(dentry
);
1343 dentry
= d_alloc(dir
, name
);
1344 if (unlikely(!dentry
))
1345 return ERR_PTR(-ENOMEM
);
1347 *need_lookup
= true;
1353 * Call i_op->lookup on the dentry. The dentry must be negative and
1356 * dir->d_inode->i_mutex must be held
1358 static struct dentry
*lookup_real(struct inode
*dir
, struct dentry
*dentry
,
1363 /* Don't create child dentry for a dead directory. */
1364 if (unlikely(IS_DEADDIR(dir
))) {
1366 return ERR_PTR(-ENOENT
);
1369 old
= dir
->i_op
->lookup(dir
, dentry
, flags
);
1370 if (unlikely(old
)) {
1377 static struct dentry
*__lookup_hash(struct qstr
*name
,
1378 struct dentry
*base
, unsigned int flags
)
1381 struct dentry
*dentry
;
1383 dentry
= lookup_dcache(name
, base
, flags
, &need_lookup
);
1387 return lookup_real(base
->d_inode
, dentry
, flags
);
1391 * It's more convoluted than I'd like it to be, but... it's still fairly
1392 * small and for now I'd prefer to have fast path as straight as possible.
1393 * It _is_ time-critical.
1395 static int lookup_fast(struct nameidata
*nd
,
1396 struct path
*path
, struct inode
**inode
)
1398 struct vfsmount
*mnt
= nd
->path
.mnt
;
1399 struct dentry
*dentry
, *parent
= nd
->path
.dentry
;
1405 * Rename seqlock is not required here because in the off chance
1406 * of a false negative due to a concurrent rename, we're going to
1407 * do the non-racy lookup, below.
1409 if (nd
->flags
& LOOKUP_RCU
) {
1412 dentry
= __d_lookup_rcu(parent
, &nd
->last
, &seq
);
1417 * This sequence count validates that the inode matches
1418 * the dentry name information from lookup.
1420 *inode
= dentry
->d_inode
;
1421 negative
= d_is_negative(dentry
);
1422 if (read_seqcount_retry(&dentry
->d_seq
, seq
))
1428 * This sequence count validates that the parent had no
1429 * changes while we did the lookup of the dentry above.
1431 * The memory barrier in read_seqcount_begin of child is
1432 * enough, we can use __read_seqcount_retry here.
1434 if (__read_seqcount_retry(&parent
->d_seq
, nd
->seq
))
1438 if (unlikely(dentry
->d_flags
& DCACHE_OP_REVALIDATE
)) {
1439 status
= d_revalidate(dentry
, nd
->flags
);
1440 if (unlikely(status
<= 0)) {
1441 if (status
!= -ECHILD
)
1447 path
->dentry
= dentry
;
1448 if (likely(__follow_mount_rcu(nd
, path
, inode
)))
1451 if (unlazy_walk(nd
, dentry
))
1454 dentry
= __d_lookup(parent
, &nd
->last
);
1457 if (unlikely(!dentry
))
1460 if (unlikely(dentry
->d_flags
& DCACHE_OP_REVALIDATE
) && need_reval
)
1461 status
= d_revalidate(dentry
, nd
->flags
);
1462 if (unlikely(status
<= 0)) {
1467 d_invalidate(dentry
);
1472 if (unlikely(d_is_negative(dentry
))) {
1477 path
->dentry
= dentry
;
1478 err
= follow_managed(path
, nd
->flags
);
1479 if (unlikely(err
< 0)) {
1480 path_put_conditional(path
, nd
);
1484 nd
->flags
|= LOOKUP_JUMPED
;
1485 *inode
= path
->dentry
->d_inode
;
1492 /* Fast lookup failed, do it the slow way */
1493 static int lookup_slow(struct nameidata
*nd
, struct path
*path
)
1495 struct dentry
*dentry
, *parent
;
1498 parent
= nd
->path
.dentry
;
1499 BUG_ON(nd
->inode
!= parent
->d_inode
);
1501 mutex_lock(&parent
->d_inode
->i_mutex
);
1502 dentry
= __lookup_hash(&nd
->last
, parent
, nd
->flags
);
1503 mutex_unlock(&parent
->d_inode
->i_mutex
);
1505 return PTR_ERR(dentry
);
1506 path
->mnt
= nd
->path
.mnt
;
1507 path
->dentry
= dentry
;
1508 err
= follow_managed(path
, nd
->flags
);
1509 if (unlikely(err
< 0)) {
1510 path_put_conditional(path
, nd
);
1514 nd
->flags
|= LOOKUP_JUMPED
;
1518 static inline int may_lookup(struct nameidata
*nd
)
1520 if (nd
->flags
& LOOKUP_RCU
) {
1521 int err
= inode_permission(nd
->inode
, MAY_EXEC
|MAY_NOT_BLOCK
);
1524 if (unlazy_walk(nd
, NULL
))
1527 return inode_permission(nd
->inode
, MAY_EXEC
);
1530 static inline int handle_dots(struct nameidata
*nd
, int type
)
1532 if (type
== LAST_DOTDOT
) {
1533 if (nd
->flags
& LOOKUP_RCU
) {
1534 if (follow_dotdot_rcu(nd
))
1542 static void terminate_walk(struct nameidata
*nd
)
1544 if (!(nd
->flags
& LOOKUP_RCU
)) {
1545 path_put(&nd
->path
);
1547 nd
->flags
&= ~LOOKUP_RCU
;
1548 if (!(nd
->flags
& LOOKUP_ROOT
))
1549 nd
->root
.mnt
= NULL
;
1555 * Do we need to follow links? We _really_ want to be able
1556 * to do this check without having to look at inode->i_op,
1557 * so we keep a cache of "no, this doesn't need follow_link"
1558 * for the common case.
1560 static inline int should_follow_link(struct dentry
*dentry
, int follow
)
1562 return unlikely(d_is_symlink(dentry
)) ? follow
: 0;
1565 static int walk_component(struct nameidata
*nd
, int follow
)
1568 struct inode
*inode
;
1571 * "." and ".." are special - ".." especially so because it has
1572 * to be able to know about the current root directory and
1573 * parent relationships.
1575 if (unlikely(nd
->last_type
!= LAST_NORM
))
1576 return handle_dots(nd
, nd
->last_type
);
1577 err
= lookup_fast(nd
, &path
, &inode
);
1578 if (unlikely(err
)) {
1582 err
= lookup_slow(nd
, &path
);
1586 inode
= path
.dentry
->d_inode
;
1588 if (d_is_negative(path
.dentry
))
1592 if (should_follow_link(path
.dentry
, follow
)) {
1593 if (nd
->flags
& LOOKUP_RCU
) {
1594 if (unlikely(nd
->path
.mnt
!= path
.mnt
||
1595 unlazy_walk(nd
, path
.dentry
))) {
1600 BUG_ON(inode
!= path
.dentry
->d_inode
);
1604 path_to_nameidata(&path
, nd
);
1609 path_to_nameidata(&path
, nd
);
1616 * This limits recursive symlink follows to 8, while
1617 * limiting consecutive symlinks to 40.
1619 * Without that kind of total limit, nasty chains of consecutive
1620 * symlinks can cause almost arbitrarily long lookups.
1622 static inline int nested_symlink(struct nameidata
*nd
)
1626 if (unlikely(current
->link_count
>= MAX_NESTED_LINKS
)) {
1627 path_put_conditional(&nd
->link
, nd
);
1628 path_put(&nd
->path
);
1631 BUG_ON(nd
->depth
>= MAX_NESTED_LINKS
);
1634 current
->link_count
++;
1637 struct path link
= nd
->link
;
1640 res
= follow_link(&link
, nd
, &cookie
);
1643 res
= walk_component(nd
, LOOKUP_FOLLOW
);
1644 put_link(nd
, &link
, cookie
);
1647 current
->link_count
--;
1653 * We can do the critical dentry name comparison and hashing
1654 * operations one word at a time, but we are limited to:
1656 * - Architectures with fast unaligned word accesses. We could
1657 * do a "get_unaligned()" if this helps and is sufficiently
1660 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
1661 * do not trap on the (extremely unlikely) case of a page
1662 * crossing operation.
1664 * - Furthermore, we need an efficient 64-bit compile for the
1665 * 64-bit case in order to generate the "number of bytes in
1666 * the final mask". Again, that could be replaced with a
1667 * efficient population count instruction or similar.
1669 #ifdef CONFIG_DCACHE_WORD_ACCESS
1671 #include <asm/word-at-a-time.h>
1675 static inline unsigned int fold_hash(unsigned long hash
)
1677 return hash_64(hash
, 32);
1680 #else /* 32-bit case */
1682 #define fold_hash(x) (x)
1686 unsigned int full_name_hash(const unsigned char *name
, unsigned int len
)
1688 unsigned long a
, mask
;
1689 unsigned long hash
= 0;
1692 a
= load_unaligned_zeropad(name
);
1693 if (len
< sizeof(unsigned long))
1697 name
+= sizeof(unsigned long);
1698 len
-= sizeof(unsigned long);
1702 mask
= bytemask_from_count(len
);
1705 return fold_hash(hash
);
1707 EXPORT_SYMBOL(full_name_hash
);
1710 * Calculate the length and hash of the path component, and
1711 * return the "hash_len" as the result.
1713 static inline u64
hash_name(const char *name
)
1715 unsigned long a
, b
, adata
, bdata
, mask
, hash
, len
;
1716 const struct word_at_a_time constants
= WORD_AT_A_TIME_CONSTANTS
;
1719 len
= -sizeof(unsigned long);
1721 hash
= (hash
+ a
) * 9;
1722 len
+= sizeof(unsigned long);
1723 a
= load_unaligned_zeropad(name
+len
);
1724 b
= a
^ REPEAT_BYTE('/');
1725 } while (!(has_zero(a
, &adata
, &constants
) | has_zero(b
, &bdata
, &constants
)));
1727 adata
= prep_zero_mask(a
, adata
, &constants
);
1728 bdata
= prep_zero_mask(b
, bdata
, &constants
);
1730 mask
= create_zero_mask(adata
| bdata
);
1732 hash
+= a
& zero_bytemask(mask
);
1733 len
+= find_zero(mask
);
1734 return hashlen_create(fold_hash(hash
), len
);
1739 unsigned int full_name_hash(const unsigned char *name
, unsigned int len
)
1741 unsigned long hash
= init_name_hash();
1743 hash
= partial_name_hash(*name
++, hash
);
1744 return end_name_hash(hash
);
1746 EXPORT_SYMBOL(full_name_hash
);
1749 * We know there's a real path component here of at least
1752 static inline u64
hash_name(const char *name
)
1754 unsigned long hash
= init_name_hash();
1755 unsigned long len
= 0, c
;
1757 c
= (unsigned char)*name
;
1760 hash
= partial_name_hash(c
, hash
);
1761 c
= (unsigned char)name
[len
];
1762 } while (c
&& c
!= '/');
1763 return hashlen_create(end_name_hash(hash
), len
);
1770 * This is the basic name resolution function, turning a pathname into
1771 * the final dentry. We expect 'base' to be positive and a directory.
1773 * Returns 0 and nd will have valid dentry and mnt on success.
1774 * Returns error and drops reference to input namei data on failure.
1776 static int link_path_walk(const char *name
, struct nameidata
*nd
)
1785 /* At this point we know we have a real path component. */
1790 err
= may_lookup(nd
);
1794 hash_len
= hash_name(name
);
1797 if (name
[0] == '.') switch (hashlen_len(hash_len
)) {
1799 if (name
[1] == '.') {
1801 nd
->flags
|= LOOKUP_JUMPED
;
1807 if (likely(type
== LAST_NORM
)) {
1808 struct dentry
*parent
= nd
->path
.dentry
;
1809 nd
->flags
&= ~LOOKUP_JUMPED
;
1810 if (unlikely(parent
->d_flags
& DCACHE_OP_HASH
)) {
1811 struct qstr
this = { { .hash_len
= hash_len
}, .name
= name
};
1812 err
= parent
->d_op
->d_hash(parent
, &this);
1815 hash_len
= this.hash_len
;
1820 nd
->last
.hash_len
= hash_len
;
1821 nd
->last
.name
= name
;
1822 nd
->last_type
= type
;
1824 name
+= hashlen_len(hash_len
);
1828 * If it wasn't NUL, we know it was '/'. Skip that
1829 * slash, and continue until no more slashes.
1833 } while (unlikely(*name
== '/'));
1837 err
= walk_component(nd
, LOOKUP_FOLLOW
);
1842 err
= nested_symlink(nd
);
1846 if (!d_can_lookup(nd
->path
.dentry
)) {
1855 static int path_init(int dfd
, const struct filename
*name
, unsigned int flags
,
1856 struct nameidata
*nd
)
1859 const char *s
= name
->name
;
1861 nd
->last_type
= LAST_ROOT
; /* if there are only slashes... */
1862 nd
->flags
= flags
| LOOKUP_JUMPED
| LOOKUP_PARENT
;
1865 if (flags
& LOOKUP_ROOT
) {
1866 struct dentry
*root
= nd
->root
.dentry
;
1867 struct inode
*inode
= root
->d_inode
;
1869 if (!d_can_lookup(root
))
1871 retval
= inode_permission(inode
, MAY_EXEC
);
1875 nd
->path
= nd
->root
;
1877 if (flags
& LOOKUP_RCU
) {
1879 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1880 nd
->m_seq
= read_seqbegin(&mount_lock
);
1882 path_get(&nd
->path
);
1887 nd
->root
.mnt
= NULL
;
1889 nd
->m_seq
= read_seqbegin(&mount_lock
);
1891 if (flags
& LOOKUP_RCU
) {
1893 nd
->seq
= set_root_rcu(nd
);
1896 path_get(&nd
->root
);
1898 nd
->path
= nd
->root
;
1899 } else if (dfd
== AT_FDCWD
) {
1900 if (flags
& LOOKUP_RCU
) {
1901 struct fs_struct
*fs
= current
->fs
;
1907 seq
= read_seqcount_begin(&fs
->seq
);
1909 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1910 } while (read_seqcount_retry(&fs
->seq
, seq
));
1912 get_fs_pwd(current
->fs
, &nd
->path
);
1915 /* Caller must check execute permissions on the starting path component */
1916 struct fd f
= fdget_raw(dfd
);
1917 struct dentry
*dentry
;
1922 dentry
= f
.file
->f_path
.dentry
;
1925 if (!d_can_lookup(dentry
)) {
1931 nd
->path
= f
.file
->f_path
;
1932 if (flags
& LOOKUP_RCU
) {
1933 if (f
.flags
& FDPUT_FPUT
)
1935 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1938 path_get(&nd
->path
);
1943 nd
->inode
= nd
->path
.dentry
->d_inode
;
1944 if (!(flags
& LOOKUP_RCU
))
1946 if (likely(!read_seqcount_retry(&nd
->path
.dentry
->d_seq
, nd
->seq
)))
1948 if (!(nd
->flags
& LOOKUP_ROOT
))
1949 nd
->root
.mnt
= NULL
;
1953 current
->total_link_count
= 0;
1954 return link_path_walk(s
, nd
);
1957 static void path_cleanup(struct nameidata
*nd
)
1959 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
)) {
1960 path_put(&nd
->root
);
1961 nd
->root
.mnt
= NULL
;
1963 if (unlikely(nd
->base
))
1967 static inline int lookup_last(struct nameidata
*nd
)
1969 if (nd
->last_type
== LAST_NORM
&& nd
->last
.name
[nd
->last
.len
])
1970 nd
->flags
|= LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
;
1972 nd
->flags
&= ~LOOKUP_PARENT
;
1973 return walk_component(nd
, nd
->flags
& LOOKUP_FOLLOW
);
1976 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
1977 static int path_lookupat(int dfd
, const struct filename
*name
,
1978 unsigned int flags
, struct nameidata
*nd
)
1983 * Path walking is largely split up into 2 different synchronisation
1984 * schemes, rcu-walk and ref-walk (explained in
1985 * Documentation/filesystems/path-lookup.txt). These share much of the
1986 * path walk code, but some things particularly setup, cleanup, and
1987 * following mounts are sufficiently divergent that functions are
1988 * duplicated. Typically there is a function foo(), and its RCU
1989 * analogue, foo_rcu().
1991 * -ECHILD is the error number of choice (just to avoid clashes) that
1992 * is returned if some aspect of an rcu-walk fails. Such an error must
1993 * be handled by restarting a traditional ref-walk (which will always
1994 * be able to complete).
1996 err
= path_init(dfd
, name
, flags
, nd
);
1997 if (!err
&& !(flags
& LOOKUP_PARENT
)) {
1998 err
= lookup_last(nd
);
2001 struct path link
= nd
->link
;
2002 err
= may_follow_link(&link
, nd
);
2005 nd
->flags
|= LOOKUP_PARENT
;
2006 err
= follow_link(&link
, nd
, &cookie
);
2009 err
= lookup_last(nd
);
2010 put_link(nd
, &link
, cookie
);
2015 err
= complete_walk(nd
);
2017 if (!err
&& nd
->flags
& LOOKUP_DIRECTORY
) {
2018 if (!d_can_lookup(nd
->path
.dentry
)) {
2019 path_put(&nd
->path
);
2028 static int filename_lookup(int dfd
, struct filename
*name
,
2029 unsigned int flags
, struct nameidata
*nd
)
2031 int retval
= path_lookupat(dfd
, name
, flags
| LOOKUP_RCU
, nd
);
2032 if (unlikely(retval
== -ECHILD
))
2033 retval
= path_lookupat(dfd
, name
, flags
, nd
);
2034 if (unlikely(retval
== -ESTALE
))
2035 retval
= path_lookupat(dfd
, name
, flags
| LOOKUP_REVAL
, nd
);
2037 if (likely(!retval
))
2038 audit_inode(name
, nd
->path
.dentry
, flags
& LOOKUP_PARENT
);
2042 /* does lookup, returns the object with parent locked */
2043 struct dentry
*kern_path_locked(const char *name
, struct path
*path
)
2045 struct filename
*filename
= getname_kernel(name
);
2046 struct nameidata nd
;
2050 if (IS_ERR(filename
))
2051 return ERR_CAST(filename
);
2053 err
= filename_lookup(AT_FDCWD
, filename
, LOOKUP_PARENT
, &nd
);
2058 if (nd
.last_type
!= LAST_NORM
) {
2060 d
= ERR_PTR(-EINVAL
);
2063 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2064 d
= __lookup_hash(&nd
.last
, nd
.path
.dentry
, 0);
2066 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
2076 int kern_path(const char *name
, unsigned int flags
, struct path
*path
)
2078 struct nameidata nd
;
2079 struct filename
*filename
= getname_kernel(name
);
2080 int res
= PTR_ERR(filename
);
2082 if (!IS_ERR(filename
)) {
2083 res
= filename_lookup(AT_FDCWD
, filename
, flags
, &nd
);
2090 EXPORT_SYMBOL(kern_path
);
2093 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
2094 * @dentry: pointer to dentry of the base directory
2095 * @mnt: pointer to vfs mount of the base directory
2096 * @name: pointer to file name
2097 * @flags: lookup flags
2098 * @path: pointer to struct path to fill
2100 int vfs_path_lookup(struct dentry
*dentry
, struct vfsmount
*mnt
,
2101 const char *name
, unsigned int flags
,
2104 struct filename
*filename
= getname_kernel(name
);
2105 int err
= PTR_ERR(filename
);
2107 BUG_ON(flags
& LOOKUP_PARENT
);
2109 /* the first argument of filename_lookup() is ignored with LOOKUP_ROOT */
2110 if (!IS_ERR(filename
)) {
2111 struct nameidata nd
;
2112 nd
.root
.dentry
= dentry
;
2114 err
= filename_lookup(AT_FDCWD
, filename
,
2115 flags
| LOOKUP_ROOT
, &nd
);
2122 EXPORT_SYMBOL(vfs_path_lookup
);
2125 * lookup_one_len - filesystem helper to lookup single pathname component
2126 * @name: pathname component to lookup
2127 * @base: base directory to lookup from
2128 * @len: maximum length @len should be interpreted to
2130 * Note that this routine is purely a helper for filesystem usage and should
2131 * not be called by generic code.
2133 struct dentry
*lookup_one_len(const char *name
, struct dentry
*base
, int len
)
2139 WARN_ON_ONCE(!mutex_is_locked(&base
->d_inode
->i_mutex
));
2143 this.hash
= full_name_hash(name
, len
);
2145 return ERR_PTR(-EACCES
);
2147 if (unlikely(name
[0] == '.')) {
2148 if (len
< 2 || (len
== 2 && name
[1] == '.'))
2149 return ERR_PTR(-EACCES
);
2153 c
= *(const unsigned char *)name
++;
2154 if (c
== '/' || c
== '\0')
2155 return ERR_PTR(-EACCES
);
2158 * See if the low-level filesystem might want
2159 * to use its own hash..
2161 if (base
->d_flags
& DCACHE_OP_HASH
) {
2162 int err
= base
->d_op
->d_hash(base
, &this);
2164 return ERR_PTR(err
);
2167 err
= inode_permission(base
->d_inode
, MAY_EXEC
);
2169 return ERR_PTR(err
);
2171 return __lookup_hash(&this, base
, 0);
2173 EXPORT_SYMBOL(lookup_one_len
);
2175 int user_path_at_empty(int dfd
, const char __user
*name
, unsigned flags
,
2176 struct path
*path
, int *empty
)
2178 struct nameidata nd
;
2179 struct filename
*tmp
= getname_flags(name
, flags
, empty
);
2180 int err
= PTR_ERR(tmp
);
2183 BUG_ON(flags
& LOOKUP_PARENT
);
2185 err
= filename_lookup(dfd
, tmp
, flags
, &nd
);
2193 int user_path_at(int dfd
, const char __user
*name
, unsigned flags
,
2196 return user_path_at_empty(dfd
, name
, flags
, path
, NULL
);
2198 EXPORT_SYMBOL(user_path_at
);
2201 * NB: most callers don't do anything directly with the reference to the
2202 * to struct filename, but the nd->last pointer points into the name string
2203 * allocated by getname. So we must hold the reference to it until all
2204 * path-walking is complete.
2206 static struct filename
*
2207 user_path_parent(int dfd
, const char __user
*path
,
2208 struct path
*parent
,
2213 struct nameidata nd
;
2214 struct filename
*s
= getname(path
);
2217 /* only LOOKUP_REVAL is allowed in extra flags */
2218 flags
&= LOOKUP_REVAL
;
2223 error
= filename_lookup(dfd
, s
, flags
| LOOKUP_PARENT
, &nd
);
2226 return ERR_PTR(error
);
2230 *type
= nd
.last_type
;
2236 * mountpoint_last - look up last component for umount
2237 * @nd: pathwalk nameidata - currently pointing at parent directory of "last"
2238 * @path: pointer to container for result
2240 * This is a special lookup_last function just for umount. In this case, we
2241 * need to resolve the path without doing any revalidation.
2243 * The nameidata should be the result of doing a LOOKUP_PARENT pathwalk. Since
2244 * mountpoints are always pinned in the dcache, their ancestors are too. Thus,
2245 * in almost all cases, this lookup will be served out of the dcache. The only
2246 * cases where it won't are if nd->last refers to a symlink or the path is
2247 * bogus and it doesn't exist.
2250 * -error: if there was an error during lookup. This includes -ENOENT if the
2251 * lookup found a negative dentry. The nd->path reference will also be
2254 * 0: if we successfully resolved nd->path and found it to not to be a
2255 * symlink that needs to be followed. "path" will also be populated.
2256 * The nd->path reference will also be put.
2258 * 1: if we successfully resolved nd->last and found it to be a symlink
2259 * that needs to be followed. "path" will be populated with the path
2260 * to the link, and nd->path will *not* be put.
2263 mountpoint_last(struct nameidata
*nd
, struct path
*path
)
2266 struct dentry
*dentry
;
2267 struct dentry
*dir
= nd
->path
.dentry
;
2269 /* If we're in rcuwalk, drop out of it to handle last component */
2270 if (nd
->flags
& LOOKUP_RCU
) {
2271 if (unlazy_walk(nd
, NULL
)) {
2277 nd
->flags
&= ~LOOKUP_PARENT
;
2279 if (unlikely(nd
->last_type
!= LAST_NORM
)) {
2280 error
= handle_dots(nd
, nd
->last_type
);
2283 dentry
= dget(nd
->path
.dentry
);
2287 mutex_lock(&dir
->d_inode
->i_mutex
);
2288 dentry
= d_lookup(dir
, &nd
->last
);
2291 * No cached dentry. Mounted dentries are pinned in the cache,
2292 * so that means that this dentry is probably a symlink or the
2293 * path doesn't actually point to a mounted dentry.
2295 dentry
= d_alloc(dir
, &nd
->last
);
2298 mutex_unlock(&dir
->d_inode
->i_mutex
);
2301 dentry
= lookup_real(dir
->d_inode
, dentry
, nd
->flags
);
2302 error
= PTR_ERR(dentry
);
2303 if (IS_ERR(dentry
)) {
2304 mutex_unlock(&dir
->d_inode
->i_mutex
);
2308 mutex_unlock(&dir
->d_inode
->i_mutex
);
2311 if (d_is_negative(dentry
)) {
2316 path
->dentry
= dentry
;
2317 path
->mnt
= nd
->path
.mnt
;
2318 if (should_follow_link(dentry
, nd
->flags
& LOOKUP_FOLLOW
)) {
2331 * path_mountpoint - look up a path to be umounted
2332 * @dfd: directory file descriptor to start walk from
2333 * @name: full pathname to walk
2334 * @path: pointer to container for result
2335 * @flags: lookup flags
2337 * Look up the given name, but don't attempt to revalidate the last component.
2338 * Returns 0 and "path" will be valid on success; Returns error otherwise.
2341 path_mountpoint(int dfd
, const struct filename
*name
, struct path
*path
,
2342 struct nameidata
*nd
, unsigned int flags
)
2344 int err
= path_init(dfd
, name
, flags
, nd
);
2348 err
= mountpoint_last(nd
, path
);
2351 struct path link
= *path
;
2352 err
= may_follow_link(&link
, nd
);
2355 nd
->flags
|= LOOKUP_PARENT
;
2356 err
= follow_link(&link
, nd
, &cookie
);
2359 err
= mountpoint_last(nd
, path
);
2360 put_link(nd
, &link
, cookie
);
2368 filename_mountpoint(int dfd
, struct filename
*name
, struct path
*path
,
2371 struct nameidata nd
;
2374 return PTR_ERR(name
);
2375 error
= path_mountpoint(dfd
, name
, path
, &nd
, flags
| LOOKUP_RCU
);
2376 if (unlikely(error
== -ECHILD
))
2377 error
= path_mountpoint(dfd
, name
, path
, &nd
, flags
);
2378 if (unlikely(error
== -ESTALE
))
2379 error
= path_mountpoint(dfd
, name
, path
, &nd
, flags
| LOOKUP_REVAL
);
2381 audit_inode(name
, path
->dentry
, 0);
2387 * user_path_mountpoint_at - lookup a path from userland in order to umount it
2388 * @dfd: directory file descriptor
2389 * @name: pathname from userland
2390 * @flags: lookup flags
2391 * @path: pointer to container to hold result
2393 * A umount is a special case for path walking. We're not actually interested
2394 * in the inode in this situation, and ESTALE errors can be a problem. We
2395 * simply want track down the dentry and vfsmount attached at the mountpoint
2396 * and avoid revalidating the last component.
2398 * Returns 0 and populates "path" on success.
2401 user_path_mountpoint_at(int dfd
, const char __user
*name
, unsigned int flags
,
2404 return filename_mountpoint(dfd
, getname(name
), path
, flags
);
2408 kern_path_mountpoint(int dfd
, const char *name
, struct path
*path
,
2411 return filename_mountpoint(dfd
, getname_kernel(name
), path
, flags
);
2413 EXPORT_SYMBOL(kern_path_mountpoint
);
2415 int __check_sticky(struct inode
*dir
, struct inode
*inode
)
2417 kuid_t fsuid
= current_fsuid();
2419 if (uid_eq(inode
->i_uid
, fsuid
))
2421 if (uid_eq(dir
->i_uid
, fsuid
))
2423 return !capable_wrt_inode_uidgid(inode
, CAP_FOWNER
);
2425 EXPORT_SYMBOL(__check_sticky
);
2428 * Check whether we can remove a link victim from directory dir, check
2429 * whether the type of victim is right.
2430 * 1. We can't do it if dir is read-only (done in permission())
2431 * 2. We should have write and exec permissions on dir
2432 * 3. We can't remove anything from append-only dir
2433 * 4. We can't do anything with immutable dir (done in permission())
2434 * 5. If the sticky bit on dir is set we should either
2435 * a. be owner of dir, or
2436 * b. be owner of victim, or
2437 * c. have CAP_FOWNER capability
2438 * 6. If the victim is append-only or immutable we can't do antyhing with
2439 * links pointing to it.
2440 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
2441 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
2442 * 9. We can't remove a root or mountpoint.
2443 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
2444 * nfs_async_unlink().
2446 static int may_delete(struct inode
*dir
, struct dentry
*victim
, bool isdir
)
2448 struct inode
*inode
= victim
->d_inode
;
2451 if (d_is_negative(victim
))
2455 BUG_ON(victim
->d_parent
->d_inode
!= dir
);
2456 audit_inode_child(dir
, victim
, AUDIT_TYPE_CHILD_DELETE
);
2458 error
= inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
2464 if (check_sticky(dir
, inode
) || IS_APPEND(inode
) ||
2465 IS_IMMUTABLE(inode
) || IS_SWAPFILE(inode
))
2468 if (!d_is_dir(victim
))
2470 if (IS_ROOT(victim
))
2472 } else if (d_is_dir(victim
))
2474 if (IS_DEADDIR(dir
))
2476 if (victim
->d_flags
& DCACHE_NFSFS_RENAMED
)
2481 /* Check whether we can create an object with dentry child in directory
2483 * 1. We can't do it if child already exists (open has special treatment for
2484 * this case, but since we are inlined it's OK)
2485 * 2. We can't do it if dir is read-only (done in permission())
2486 * 3. We should have write and exec permissions on dir
2487 * 4. We can't do it if dir is immutable (done in permission())
2489 static inline int may_create(struct inode
*dir
, struct dentry
*child
)
2491 audit_inode_child(dir
, child
, AUDIT_TYPE_CHILD_CREATE
);
2494 if (IS_DEADDIR(dir
))
2496 return inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
2500 * p1 and p2 should be directories on the same fs.
2502 struct dentry
*lock_rename(struct dentry
*p1
, struct dentry
*p2
)
2507 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2511 mutex_lock(&p1
->d_inode
->i_sb
->s_vfs_rename_mutex
);
2513 p
= d_ancestor(p2
, p1
);
2515 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2516 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_CHILD
);
2520 p
= d_ancestor(p1
, p2
);
2522 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2523 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_CHILD
);
2527 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2528 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_PARENT2
);
2531 EXPORT_SYMBOL(lock_rename
);
2533 void unlock_rename(struct dentry
*p1
, struct dentry
*p2
)
2535 mutex_unlock(&p1
->d_inode
->i_mutex
);
2537 mutex_unlock(&p2
->d_inode
->i_mutex
);
2538 mutex_unlock(&p1
->d_inode
->i_sb
->s_vfs_rename_mutex
);
2541 EXPORT_SYMBOL(unlock_rename
);
2543 int vfs_create(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
,
2546 int error
= may_create(dir
, dentry
);
2550 if (!dir
->i_op
->create
)
2551 return -EACCES
; /* shouldn't it be ENOSYS? */
2554 error
= security_inode_create(dir
, dentry
, mode
);
2557 error
= dir
->i_op
->create(dir
, dentry
, mode
, want_excl
);
2559 fsnotify_create(dir
, dentry
);
2562 EXPORT_SYMBOL(vfs_create
);
2564 static int may_open(struct path
*path
, int acc_mode
, int flag
)
2566 struct dentry
*dentry
= path
->dentry
;
2567 struct inode
*inode
= dentry
->d_inode
;
2577 switch (inode
->i_mode
& S_IFMT
) {
2581 if (acc_mode
& MAY_WRITE
)
2586 if (path
->mnt
->mnt_flags
& MNT_NODEV
)
2595 error
= inode_permission(inode
, acc_mode
);
2600 * An append-only file must be opened in append mode for writing.
2602 if (IS_APPEND(inode
)) {
2603 if ((flag
& O_ACCMODE
) != O_RDONLY
&& !(flag
& O_APPEND
))
2609 /* O_NOATIME can only be set by the owner or superuser */
2610 if (flag
& O_NOATIME
&& !inode_owner_or_capable(inode
))
2616 static int handle_truncate(struct file
*filp
)
2618 struct path
*path
= &filp
->f_path
;
2619 struct inode
*inode
= path
->dentry
->d_inode
;
2620 int error
= get_write_access(inode
);
2624 * Refuse to truncate files with mandatory locks held on them.
2626 error
= locks_verify_locked(filp
);
2628 error
= security_path_truncate(path
);
2630 error
= do_truncate(path
->dentry
, 0,
2631 ATTR_MTIME
|ATTR_CTIME
|ATTR_OPEN
,
2634 put_write_access(inode
);
2638 static inline int open_to_namei_flags(int flag
)
2640 if ((flag
& O_ACCMODE
) == 3)
2645 static int may_o_create(struct path
*dir
, struct dentry
*dentry
, umode_t mode
)
2647 int error
= security_path_mknod(dir
, dentry
, mode
, 0);
2651 error
= inode_permission(dir
->dentry
->d_inode
, MAY_WRITE
| MAY_EXEC
);
2655 return security_inode_create(dir
->dentry
->d_inode
, dentry
, mode
);
2659 * Attempt to atomically look up, create and open a file from a negative
2662 * Returns 0 if successful. The file will have been created and attached to
2663 * @file by the filesystem calling finish_open().
2665 * Returns 1 if the file was looked up only or didn't need creating. The
2666 * caller will need to perform the open themselves. @path will have been
2667 * updated to point to the new dentry. This may be negative.
2669 * Returns an error code otherwise.
2671 static int atomic_open(struct nameidata
*nd
, struct dentry
*dentry
,
2672 struct path
*path
, struct file
*file
,
2673 const struct open_flags
*op
,
2674 bool got_write
, bool need_lookup
,
2677 struct inode
*dir
= nd
->path
.dentry
->d_inode
;
2678 unsigned open_flag
= open_to_namei_flags(op
->open_flag
);
2682 int create_error
= 0;
2683 struct dentry
*const DENTRY_NOT_SET
= (void *) -1UL;
2686 BUG_ON(dentry
->d_inode
);
2688 /* Don't create child dentry for a dead directory. */
2689 if (unlikely(IS_DEADDIR(dir
))) {
2695 if ((open_flag
& O_CREAT
) && !IS_POSIXACL(dir
))
2696 mode
&= ~current_umask();
2698 excl
= (open_flag
& (O_EXCL
| O_CREAT
)) == (O_EXCL
| O_CREAT
);
2700 open_flag
&= ~O_TRUNC
;
2703 * Checking write permission is tricky, bacuse we don't know if we are
2704 * going to actually need it: O_CREAT opens should work as long as the
2705 * file exists. But checking existence breaks atomicity. The trick is
2706 * to check access and if not granted clear O_CREAT from the flags.
2708 * Another problem is returing the "right" error value (e.g. for an
2709 * O_EXCL open we want to return EEXIST not EROFS).
2711 if (((open_flag
& (O_CREAT
| O_TRUNC
)) ||
2712 (open_flag
& O_ACCMODE
) != O_RDONLY
) && unlikely(!got_write
)) {
2713 if (!(open_flag
& O_CREAT
)) {
2715 * No O_CREATE -> atomicity not a requirement -> fall
2716 * back to lookup + open
2719 } else if (open_flag
& (O_EXCL
| O_TRUNC
)) {
2720 /* Fall back and fail with the right error */
2721 create_error
= -EROFS
;
2724 /* No side effects, safe to clear O_CREAT */
2725 create_error
= -EROFS
;
2726 open_flag
&= ~O_CREAT
;
2730 if (open_flag
& O_CREAT
) {
2731 error
= may_o_create(&nd
->path
, dentry
, mode
);
2733 create_error
= error
;
2734 if (open_flag
& O_EXCL
)
2736 open_flag
&= ~O_CREAT
;
2740 if (nd
->flags
& LOOKUP_DIRECTORY
)
2741 open_flag
|= O_DIRECTORY
;
2743 file
->f_path
.dentry
= DENTRY_NOT_SET
;
2744 file
->f_path
.mnt
= nd
->path
.mnt
;
2745 error
= dir
->i_op
->atomic_open(dir
, dentry
, file
, open_flag
, mode
,
2748 if (create_error
&& error
== -ENOENT
)
2749 error
= create_error
;
2753 if (error
) { /* returned 1, that is */
2754 if (WARN_ON(file
->f_path
.dentry
== DENTRY_NOT_SET
)) {
2758 if (file
->f_path
.dentry
) {
2760 dentry
= file
->f_path
.dentry
;
2762 if (*opened
& FILE_CREATED
)
2763 fsnotify_create(dir
, dentry
);
2764 if (!dentry
->d_inode
) {
2765 WARN_ON(*opened
& FILE_CREATED
);
2767 error
= create_error
;
2771 if (excl
&& !(*opened
& FILE_CREATED
)) {
2780 * We didn't have the inode before the open, so check open permission
2783 acc_mode
= op
->acc_mode
;
2784 if (*opened
& FILE_CREATED
) {
2785 WARN_ON(!(open_flag
& O_CREAT
));
2786 fsnotify_create(dir
, dentry
);
2787 acc_mode
= MAY_OPEN
;
2789 error
= may_open(&file
->f_path
, acc_mode
, open_flag
);
2799 dentry
= lookup_real(dir
, dentry
, nd
->flags
);
2801 return PTR_ERR(dentry
);
2804 int open_flag
= op
->open_flag
;
2806 error
= create_error
;
2807 if ((open_flag
& O_EXCL
)) {
2808 if (!dentry
->d_inode
)
2810 } else if (!dentry
->d_inode
) {
2812 } else if ((open_flag
& O_TRUNC
) &&
2816 /* will fail later, go on to get the right error */
2820 path
->dentry
= dentry
;
2821 path
->mnt
= nd
->path
.mnt
;
2826 * Look up and maybe create and open the last component.
2828 * Must be called with i_mutex held on parent.
2830 * Returns 0 if the file was successfully atomically created (if necessary) and
2831 * opened. In this case the file will be returned attached to @file.
2833 * Returns 1 if the file was not completely opened at this time, though lookups
2834 * and creations will have been performed and the dentry returned in @path will
2835 * be positive upon return if O_CREAT was specified. If O_CREAT wasn't
2836 * specified then a negative dentry may be returned.
2838 * An error code is returned otherwise.
2840 * FILE_CREATE will be set in @*opened if the dentry was created and will be
2841 * cleared otherwise prior to returning.
2843 static int lookup_open(struct nameidata
*nd
, struct path
*path
,
2845 const struct open_flags
*op
,
2846 bool got_write
, int *opened
)
2848 struct dentry
*dir
= nd
->path
.dentry
;
2849 struct inode
*dir_inode
= dir
->d_inode
;
2850 struct dentry
*dentry
;
2854 *opened
&= ~FILE_CREATED
;
2855 dentry
= lookup_dcache(&nd
->last
, dir
, nd
->flags
, &need_lookup
);
2857 return PTR_ERR(dentry
);
2859 /* Cached positive dentry: will open in f_op->open */
2860 if (!need_lookup
&& dentry
->d_inode
)
2863 if ((nd
->flags
& LOOKUP_OPEN
) && dir_inode
->i_op
->atomic_open
) {
2864 return atomic_open(nd
, dentry
, path
, file
, op
, got_write
,
2865 need_lookup
, opened
);
2869 BUG_ON(dentry
->d_inode
);
2871 dentry
= lookup_real(dir_inode
, dentry
, nd
->flags
);
2873 return PTR_ERR(dentry
);
2876 /* Negative dentry, just create the file */
2877 if (!dentry
->d_inode
&& (op
->open_flag
& O_CREAT
)) {
2878 umode_t mode
= op
->mode
;
2879 if (!IS_POSIXACL(dir
->d_inode
))
2880 mode
&= ~current_umask();
2882 * This write is needed to ensure that a
2883 * rw->ro transition does not occur between
2884 * the time when the file is created and when
2885 * a permanent write count is taken through
2886 * the 'struct file' in finish_open().
2892 *opened
|= FILE_CREATED
;
2893 error
= security_path_mknod(&nd
->path
, dentry
, mode
, 0);
2896 error
= vfs_create(dir
->d_inode
, dentry
, mode
,
2897 nd
->flags
& LOOKUP_EXCL
);
2902 path
->dentry
= dentry
;
2903 path
->mnt
= nd
->path
.mnt
;
2912 * Handle the last step of open()
2914 static int do_last(struct nameidata
*nd
, struct path
*path
,
2915 struct file
*file
, const struct open_flags
*op
,
2916 int *opened
, struct filename
*name
)
2918 struct dentry
*dir
= nd
->path
.dentry
;
2919 int open_flag
= op
->open_flag
;
2920 bool will_truncate
= (open_flag
& O_TRUNC
) != 0;
2921 bool got_write
= false;
2922 int acc_mode
= op
->acc_mode
;
2923 struct inode
*inode
;
2924 struct path save_parent
= { .dentry
= NULL
, .mnt
= NULL
};
2925 bool retried
= false;
2928 nd
->flags
&= ~LOOKUP_PARENT
;
2929 nd
->flags
|= op
->intent
;
2931 if (nd
->last_type
!= LAST_NORM
) {
2932 error
= handle_dots(nd
, nd
->last_type
);
2938 if (!(open_flag
& O_CREAT
)) {
2939 if (nd
->last
.name
[nd
->last
.len
])
2940 nd
->flags
|= LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
;
2941 /* we _can_ be in RCU mode here */
2942 error
= lookup_fast(nd
, path
, &inode
);
2949 BUG_ON(nd
->inode
!= dir
->d_inode
);
2951 /* create side of things */
2953 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED
2954 * has been cleared when we got to the last component we are
2957 error
= complete_walk(nd
);
2961 audit_inode(name
, dir
, LOOKUP_PARENT
);
2963 /* trailing slashes? */
2964 if (nd
->last
.name
[nd
->last
.len
])
2969 if (op
->open_flag
& (O_CREAT
| O_TRUNC
| O_WRONLY
| O_RDWR
)) {
2970 error
= mnt_want_write(nd
->path
.mnt
);
2974 * do _not_ fail yet - we might not need that or fail with
2975 * a different error; let lookup_open() decide; we'll be
2976 * dropping this one anyway.
2979 mutex_lock(&dir
->d_inode
->i_mutex
);
2980 error
= lookup_open(nd
, path
, file
, op
, got_write
, opened
);
2981 mutex_unlock(&dir
->d_inode
->i_mutex
);
2987 if ((*opened
& FILE_CREATED
) ||
2988 !S_ISREG(file_inode(file
)->i_mode
))
2989 will_truncate
= false;
2991 audit_inode(name
, file
->f_path
.dentry
, 0);
2995 if (*opened
& FILE_CREATED
) {
2996 /* Don't check for write permission, don't truncate */
2997 open_flag
&= ~O_TRUNC
;
2998 will_truncate
= false;
2999 acc_mode
= MAY_OPEN
;
3000 path_to_nameidata(path
, nd
);
3001 goto finish_open_created
;
3005 * create/update audit record if it already exists.
3007 if (d_is_positive(path
->dentry
))
3008 audit_inode(name
, path
->dentry
, 0);
3011 * If atomic_open() acquired write access it is dropped now due to
3012 * possible mount and symlink following (this might be optimized away if
3016 mnt_drop_write(nd
->path
.mnt
);
3021 if ((open_flag
& (O_EXCL
| O_CREAT
)) == (O_EXCL
| O_CREAT
))
3024 error
= follow_managed(path
, nd
->flags
);
3029 nd
->flags
|= LOOKUP_JUMPED
;
3031 BUG_ON(nd
->flags
& LOOKUP_RCU
);
3032 inode
= path
->dentry
->d_inode
;
3034 if (d_is_negative(path
->dentry
)) {
3035 path_to_nameidata(path
, nd
);
3039 if (should_follow_link(path
->dentry
, nd
->flags
& LOOKUP_FOLLOW
)) {
3040 if (nd
->flags
& LOOKUP_RCU
) {
3041 if (unlikely(nd
->path
.mnt
!= path
->mnt
||
3042 unlazy_walk(nd
, path
->dentry
))) {
3047 BUG_ON(inode
!= path
->dentry
->d_inode
);
3052 if (unlikely(d_is_symlink(path
->dentry
)) && !(open_flag
& O_PATH
)) {
3053 path_to_nameidata(path
, nd
);
3058 if ((nd
->flags
& LOOKUP_RCU
) || nd
->path
.mnt
!= path
->mnt
) {
3059 path_to_nameidata(path
, nd
);
3061 save_parent
.dentry
= nd
->path
.dentry
;
3062 save_parent
.mnt
= mntget(path
->mnt
);
3063 nd
->path
.dentry
= path
->dentry
;
3067 /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
3069 error
= complete_walk(nd
);
3071 path_put(&save_parent
);
3074 audit_inode(name
, nd
->path
.dentry
, 0);
3076 if ((open_flag
& O_CREAT
) && d_is_dir(nd
->path
.dentry
))
3079 if ((nd
->flags
& LOOKUP_DIRECTORY
) && !d_can_lookup(nd
->path
.dentry
))
3081 if (!d_is_reg(nd
->path
.dentry
))
3082 will_truncate
= false;
3084 if (will_truncate
) {
3085 error
= mnt_want_write(nd
->path
.mnt
);
3090 finish_open_created
:
3091 error
= may_open(&nd
->path
, acc_mode
, open_flag
);
3095 BUG_ON(*opened
& FILE_OPENED
); /* once it's opened, it's opened */
3096 error
= vfs_open(&nd
->path
, file
, current_cred());
3098 *opened
|= FILE_OPENED
;
3100 if (error
== -EOPENSTALE
)
3105 error
= open_check_o_direct(file
);
3108 error
= ima_file_check(file
, op
->acc_mode
, *opened
);
3112 if (will_truncate
) {
3113 error
= handle_truncate(file
);
3119 mnt_drop_write(nd
->path
.mnt
);
3120 path_put(&save_parent
);
3125 path_put_conditional(path
, nd
);
3132 /* If no saved parent or already retried then can't retry */
3133 if (!save_parent
.dentry
|| retried
)
3136 BUG_ON(save_parent
.dentry
!= dir
);
3137 path_put(&nd
->path
);
3138 nd
->path
= save_parent
;
3139 nd
->inode
= dir
->d_inode
;
3140 save_parent
.mnt
= NULL
;
3141 save_parent
.dentry
= NULL
;
3143 mnt_drop_write(nd
->path
.mnt
);
3150 static int do_tmpfile(int dfd
, struct filename
*pathname
,
3151 struct nameidata
*nd
, int flags
,
3152 const struct open_flags
*op
,
3153 struct file
*file
, int *opened
)
3155 static const struct qstr name
= QSTR_INIT("/", 1);
3156 struct dentry
*dentry
, *child
;
3158 int error
= path_lookupat(dfd
, pathname
,
3159 flags
| LOOKUP_DIRECTORY
, nd
);
3160 if (unlikely(error
))
3162 error
= mnt_want_write(nd
->path
.mnt
);
3163 if (unlikely(error
))
3165 /* we want directory to be writable */
3166 error
= inode_permission(nd
->inode
, MAY_WRITE
| MAY_EXEC
);
3169 dentry
= nd
->path
.dentry
;
3170 dir
= dentry
->d_inode
;
3171 if (!dir
->i_op
->tmpfile
) {
3172 error
= -EOPNOTSUPP
;
3175 child
= d_alloc(dentry
, &name
);
3176 if (unlikely(!child
)) {
3180 nd
->flags
&= ~LOOKUP_DIRECTORY
;
3181 nd
->flags
|= op
->intent
;
3182 dput(nd
->path
.dentry
);
3183 nd
->path
.dentry
= child
;
3184 error
= dir
->i_op
->tmpfile(dir
, nd
->path
.dentry
, op
->mode
);
3187 audit_inode(pathname
, nd
->path
.dentry
, 0);
3188 /* Don't check for other permissions, the inode was just created */
3189 error
= may_open(&nd
->path
, MAY_OPEN
, op
->open_flag
);
3192 file
->f_path
.mnt
= nd
->path
.mnt
;
3193 error
= finish_open(file
, nd
->path
.dentry
, NULL
, opened
);
3196 error
= open_check_o_direct(file
);
3199 } else if (!(op
->open_flag
& O_EXCL
)) {
3200 struct inode
*inode
= file_inode(file
);
3201 spin_lock(&inode
->i_lock
);
3202 inode
->i_state
|= I_LINKABLE
;
3203 spin_unlock(&inode
->i_lock
);
3206 mnt_drop_write(nd
->path
.mnt
);
3208 path_put(&nd
->path
);
3212 static struct file
*path_openat(int dfd
, struct filename
*pathname
,
3213 struct nameidata
*nd
, const struct open_flags
*op
, int flags
)
3220 file
= get_empty_filp();
3224 file
->f_flags
= op
->open_flag
;
3226 if (unlikely(file
->f_flags
& __O_TMPFILE
)) {
3227 error
= do_tmpfile(dfd
, pathname
, nd
, flags
, op
, file
, &opened
);
3231 error
= path_init(dfd
, pathname
, flags
, nd
);
3232 if (unlikely(error
))
3235 error
= do_last(nd
, &path
, file
, op
, &opened
, pathname
);
3236 while (unlikely(error
> 0)) { /* trailing symlink */
3237 struct path link
= nd
->link
;
3239 error
= may_follow_link(&link
, nd
);
3240 if (unlikely(error
))
3242 nd
->flags
|= LOOKUP_PARENT
;
3243 nd
->flags
&= ~(LOOKUP_OPEN
|LOOKUP_CREATE
|LOOKUP_EXCL
);
3244 error
= follow_link(&link
, nd
, &cookie
);
3245 if (unlikely(error
))
3247 error
= do_last(nd
, &path
, file
, op
, &opened
, pathname
);
3248 put_link(nd
, &link
, cookie
);
3253 if (!(opened
& FILE_OPENED
)) {
3257 if (unlikely(error
)) {
3258 if (error
== -EOPENSTALE
) {
3259 if (flags
& LOOKUP_RCU
)
3264 file
= ERR_PTR(error
);
3269 struct file
*do_filp_open(int dfd
, struct filename
*pathname
,
3270 const struct open_flags
*op
)
3272 struct nameidata nd
;
3273 int flags
= op
->lookup_flags
;
3276 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
| LOOKUP_RCU
);
3277 if (unlikely(filp
== ERR_PTR(-ECHILD
)))
3278 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
);
3279 if (unlikely(filp
== ERR_PTR(-ESTALE
)))
3280 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
| LOOKUP_REVAL
);
3284 struct file
*do_file_open_root(struct dentry
*dentry
, struct vfsmount
*mnt
,
3285 const char *name
, const struct open_flags
*op
)
3287 struct nameidata nd
;
3289 struct filename
*filename
;
3290 int flags
= op
->lookup_flags
| LOOKUP_ROOT
;
3293 nd
.root
.dentry
= dentry
;
3295 if (d_is_symlink(dentry
) && op
->intent
& LOOKUP_OPEN
)
3296 return ERR_PTR(-ELOOP
);
3298 filename
= getname_kernel(name
);
3299 if (unlikely(IS_ERR(filename
)))
3300 return ERR_CAST(filename
);
3302 file
= path_openat(-1, filename
, &nd
, op
, flags
| LOOKUP_RCU
);
3303 if (unlikely(file
== ERR_PTR(-ECHILD
)))
3304 file
= path_openat(-1, filename
, &nd
, op
, flags
);
3305 if (unlikely(file
== ERR_PTR(-ESTALE
)))
3306 file
= path_openat(-1, filename
, &nd
, op
, flags
| LOOKUP_REVAL
);
3311 static struct dentry
*filename_create(int dfd
, struct filename
*name
,
3312 struct path
*path
, unsigned int lookup_flags
)
3314 struct dentry
*dentry
= ERR_PTR(-EEXIST
);
3315 struct nameidata nd
;
3318 bool is_dir
= (lookup_flags
& LOOKUP_DIRECTORY
);
3321 * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any
3322 * other flags passed in are ignored!
3324 lookup_flags
&= LOOKUP_REVAL
;
3326 error
= filename_lookup(dfd
, name
, LOOKUP_PARENT
|lookup_flags
, &nd
);
3328 return ERR_PTR(error
);
3331 * Yucky last component or no last component at all?
3332 * (foo/., foo/.., /////)
3334 if (nd
.last_type
!= LAST_NORM
)
3336 nd
.flags
&= ~LOOKUP_PARENT
;
3337 nd
.flags
|= LOOKUP_CREATE
| LOOKUP_EXCL
;
3339 /* don't fail immediately if it's r/o, at least try to report other errors */
3340 err2
= mnt_want_write(nd
.path
.mnt
);
3342 * Do the final lookup.
3344 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
3345 dentry
= __lookup_hash(&nd
.last
, nd
.path
.dentry
, nd
.flags
);
3350 if (d_is_positive(dentry
))
3354 * Special case - lookup gave negative, but... we had foo/bar/
3355 * From the vfs_mknod() POV we just have a negative dentry -
3356 * all is fine. Let's be bastards - you had / on the end, you've
3357 * been asking for (non-existent) directory. -ENOENT for you.
3359 if (unlikely(!is_dir
&& nd
.last
.name
[nd
.last
.len
])) {
3363 if (unlikely(err2
)) {
3371 dentry
= ERR_PTR(error
);
3373 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
3375 mnt_drop_write(nd
.path
.mnt
);
3381 struct dentry
*kern_path_create(int dfd
, const char *pathname
,
3382 struct path
*path
, unsigned int lookup_flags
)
3384 struct filename
*filename
= getname_kernel(pathname
);
3387 if (IS_ERR(filename
))
3388 return ERR_CAST(filename
);
3389 res
= filename_create(dfd
, filename
, path
, lookup_flags
);
3393 EXPORT_SYMBOL(kern_path_create
);
3395 void done_path_create(struct path
*path
, struct dentry
*dentry
)
3398 mutex_unlock(&path
->dentry
->d_inode
->i_mutex
);
3399 mnt_drop_write(path
->mnt
);
3402 EXPORT_SYMBOL(done_path_create
);
3404 struct dentry
*user_path_create(int dfd
, const char __user
*pathname
,
3405 struct path
*path
, unsigned int lookup_flags
)
3407 struct filename
*tmp
= getname(pathname
);
3410 return ERR_CAST(tmp
);
3411 res
= filename_create(dfd
, tmp
, path
, lookup_flags
);
3415 EXPORT_SYMBOL(user_path_create
);
3417 int vfs_mknod(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
, dev_t dev
)
3419 int error
= may_create(dir
, dentry
);
3424 if ((S_ISCHR(mode
) || S_ISBLK(mode
)) && !capable(CAP_MKNOD
))
3427 if (!dir
->i_op
->mknod
)
3430 error
= devcgroup_inode_mknod(mode
, dev
);
3434 error
= security_inode_mknod(dir
, dentry
, mode
, dev
);
3438 error
= dir
->i_op
->mknod(dir
, dentry
, mode
, dev
);
3440 fsnotify_create(dir
, dentry
);
3443 EXPORT_SYMBOL(vfs_mknod
);
3445 static int may_mknod(umode_t mode
)
3447 switch (mode
& S_IFMT
) {
3453 case 0: /* zero mode translates to S_IFREG */
3462 SYSCALL_DEFINE4(mknodat
, int, dfd
, const char __user
*, filename
, umode_t
, mode
,
3465 struct dentry
*dentry
;
3468 unsigned int lookup_flags
= 0;
3470 error
= may_mknod(mode
);
3474 dentry
= user_path_create(dfd
, filename
, &path
, lookup_flags
);
3476 return PTR_ERR(dentry
);
3478 if (!IS_POSIXACL(path
.dentry
->d_inode
))
3479 mode
&= ~current_umask();
3480 error
= security_path_mknod(&path
, dentry
, mode
, dev
);
3483 switch (mode
& S_IFMT
) {
3484 case 0: case S_IFREG
:
3485 error
= vfs_create(path
.dentry
->d_inode
,dentry
,mode
,true);
3487 case S_IFCHR
: case S_IFBLK
:
3488 error
= vfs_mknod(path
.dentry
->d_inode
,dentry
,mode
,
3489 new_decode_dev(dev
));
3491 case S_IFIFO
: case S_IFSOCK
:
3492 error
= vfs_mknod(path
.dentry
->d_inode
,dentry
,mode
,0);
3496 done_path_create(&path
, dentry
);
3497 if (retry_estale(error
, lookup_flags
)) {
3498 lookup_flags
|= LOOKUP_REVAL
;
3504 SYSCALL_DEFINE3(mknod
, const char __user
*, filename
, umode_t
, mode
, unsigned, dev
)
3506 return sys_mknodat(AT_FDCWD
, filename
, mode
, dev
);
3509 int vfs_mkdir(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
)
3511 int error
= may_create(dir
, dentry
);
3512 unsigned max_links
= dir
->i_sb
->s_max_links
;
3517 if (!dir
->i_op
->mkdir
)
3520 mode
&= (S_IRWXUGO
|S_ISVTX
);
3521 error
= security_inode_mkdir(dir
, dentry
, mode
);
3525 if (max_links
&& dir
->i_nlink
>= max_links
)
3528 error
= dir
->i_op
->mkdir(dir
, dentry
, mode
);
3530 fsnotify_mkdir(dir
, dentry
);
3533 EXPORT_SYMBOL(vfs_mkdir
);
3535 SYSCALL_DEFINE3(mkdirat
, int, dfd
, const char __user
*, pathname
, umode_t
, mode
)
3537 struct dentry
*dentry
;
3540 unsigned int lookup_flags
= LOOKUP_DIRECTORY
;
3543 dentry
= user_path_create(dfd
, pathname
, &path
, lookup_flags
);
3545 return PTR_ERR(dentry
);
3547 if (!IS_POSIXACL(path
.dentry
->d_inode
))
3548 mode
&= ~current_umask();
3549 error
= security_path_mkdir(&path
, dentry
, mode
);
3551 error
= vfs_mkdir(path
.dentry
->d_inode
, dentry
, mode
);
3552 done_path_create(&path
, dentry
);
3553 if (retry_estale(error
, lookup_flags
)) {
3554 lookup_flags
|= LOOKUP_REVAL
;
3560 SYSCALL_DEFINE2(mkdir
, const char __user
*, pathname
, umode_t
, mode
)
3562 return sys_mkdirat(AT_FDCWD
, pathname
, mode
);
3566 * The dentry_unhash() helper will try to drop the dentry early: we
3567 * should have a usage count of 1 if we're the only user of this
3568 * dentry, and if that is true (possibly after pruning the dcache),
3569 * then we drop the dentry now.
3571 * A low-level filesystem can, if it choses, legally
3574 * if (!d_unhashed(dentry))
3577 * if it cannot handle the case of removing a directory
3578 * that is still in use by something else..
3580 void dentry_unhash(struct dentry
*dentry
)
3582 shrink_dcache_parent(dentry
);
3583 spin_lock(&dentry
->d_lock
);
3584 if (dentry
->d_lockref
.count
== 1)
3586 spin_unlock(&dentry
->d_lock
);
3588 EXPORT_SYMBOL(dentry_unhash
);
3590 int vfs_rmdir(struct inode
*dir
, struct dentry
*dentry
)
3592 int error
= may_delete(dir
, dentry
, 1);
3597 if (!dir
->i_op
->rmdir
)
3601 mutex_lock(&dentry
->d_inode
->i_mutex
);
3604 if (is_local_mountpoint(dentry
))
3607 error
= security_inode_rmdir(dir
, dentry
);
3611 shrink_dcache_parent(dentry
);
3612 error
= dir
->i_op
->rmdir(dir
, dentry
);
3616 dentry
->d_inode
->i_flags
|= S_DEAD
;
3618 detach_mounts(dentry
);
3621 mutex_unlock(&dentry
->d_inode
->i_mutex
);
3627 EXPORT_SYMBOL(vfs_rmdir
);
3629 static long do_rmdir(int dfd
, const char __user
*pathname
)
3632 struct filename
*name
;
3633 struct dentry
*dentry
;
3637 unsigned int lookup_flags
= 0;
3639 name
= user_path_parent(dfd
, pathname
,
3640 &path
, &last
, &type
, lookup_flags
);
3642 return PTR_ERR(name
);
3656 error
= mnt_want_write(path
.mnt
);
3660 mutex_lock_nested(&path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
3661 dentry
= __lookup_hash(&last
, path
.dentry
, lookup_flags
);
3662 error
= PTR_ERR(dentry
);
3665 if (!dentry
->d_inode
) {
3669 error
= security_path_rmdir(&path
, dentry
);
3672 error
= vfs_rmdir(path
.dentry
->d_inode
, dentry
);
3676 mutex_unlock(&path
.dentry
->d_inode
->i_mutex
);
3677 mnt_drop_write(path
.mnt
);
3681 if (retry_estale(error
, lookup_flags
)) {
3682 lookup_flags
|= LOOKUP_REVAL
;
3688 SYSCALL_DEFINE1(rmdir
, const char __user
*, pathname
)
3690 return do_rmdir(AT_FDCWD
, pathname
);
3694 * vfs_unlink - unlink a filesystem object
3695 * @dir: parent directory
3697 * @delegated_inode: returns victim inode, if the inode is delegated.
3699 * The caller must hold dir->i_mutex.
3701 * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and
3702 * return a reference to the inode in delegated_inode. The caller
3703 * should then break the delegation on that inode and retry. Because
3704 * breaking a delegation may take a long time, the caller should drop
3705 * dir->i_mutex before doing so.
3707 * Alternatively, a caller may pass NULL for delegated_inode. This may
3708 * be appropriate for callers that expect the underlying filesystem not
3709 * to be NFS exported.
3711 int vfs_unlink(struct inode
*dir
, struct dentry
*dentry
, struct inode
**delegated_inode
)
3713 struct inode
*target
= dentry
->d_inode
;
3714 int error
= may_delete(dir
, dentry
, 0);
3719 if (!dir
->i_op
->unlink
)
3722 mutex_lock(&target
->i_mutex
);
3723 if (is_local_mountpoint(dentry
))
3726 error
= security_inode_unlink(dir
, dentry
);
3728 error
= try_break_deleg(target
, delegated_inode
);
3731 error
= dir
->i_op
->unlink(dir
, dentry
);
3734 detach_mounts(dentry
);
3739 mutex_unlock(&target
->i_mutex
);
3741 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
3742 if (!error
&& !(dentry
->d_flags
& DCACHE_NFSFS_RENAMED
)) {
3743 fsnotify_link_count(target
);
3749 EXPORT_SYMBOL(vfs_unlink
);
3752 * Make sure that the actual truncation of the file will occur outside its
3753 * directory's i_mutex. Truncate can take a long time if there is a lot of
3754 * writeout happening, and we don't want to prevent access to the directory
3755 * while waiting on the I/O.
3757 static long do_unlinkat(int dfd
, const char __user
*pathname
)
3760 struct filename
*name
;
3761 struct dentry
*dentry
;
3765 struct inode
*inode
= NULL
;
3766 struct inode
*delegated_inode
= NULL
;
3767 unsigned int lookup_flags
= 0;
3769 name
= user_path_parent(dfd
, pathname
,
3770 &path
, &last
, &type
, lookup_flags
);
3772 return PTR_ERR(name
);
3775 if (type
!= LAST_NORM
)
3778 error
= mnt_want_write(path
.mnt
);
3782 mutex_lock_nested(&path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
3783 dentry
= __lookup_hash(&last
, path
.dentry
, lookup_flags
);
3784 error
= PTR_ERR(dentry
);
3785 if (!IS_ERR(dentry
)) {
3786 /* Why not before? Because we want correct error value */
3787 if (last
.name
[last
.len
])
3789 inode
= dentry
->d_inode
;
3790 if (d_is_negative(dentry
))
3793 error
= security_path_unlink(&path
, dentry
);
3796 error
= vfs_unlink(path
.dentry
->d_inode
, dentry
, &delegated_inode
);
3800 mutex_unlock(&path
.dentry
->d_inode
->i_mutex
);
3802 iput(inode
); /* truncate the inode here */
3804 if (delegated_inode
) {
3805 error
= break_deleg_wait(&delegated_inode
);
3809 mnt_drop_write(path
.mnt
);
3813 if (retry_estale(error
, lookup_flags
)) {
3814 lookup_flags
|= LOOKUP_REVAL
;
3821 if (d_is_negative(dentry
))
3823 else if (d_is_dir(dentry
))
3830 SYSCALL_DEFINE3(unlinkat
, int, dfd
, const char __user
*, pathname
, int, flag
)
3832 if ((flag
& ~AT_REMOVEDIR
) != 0)
3835 if (flag
& AT_REMOVEDIR
)
3836 return do_rmdir(dfd
, pathname
);
3838 return do_unlinkat(dfd
, pathname
);
3841 SYSCALL_DEFINE1(unlink
, const char __user
*, pathname
)
3843 return do_unlinkat(AT_FDCWD
, pathname
);
3846 int vfs_symlink(struct inode
*dir
, struct dentry
*dentry
, const char *oldname
)
3848 int error
= may_create(dir
, dentry
);
3853 if (!dir
->i_op
->symlink
)
3856 error
= security_inode_symlink(dir
, dentry
, oldname
);
3860 error
= dir
->i_op
->symlink(dir
, dentry
, oldname
);
3862 fsnotify_create(dir
, dentry
);
3865 EXPORT_SYMBOL(vfs_symlink
);
3867 SYSCALL_DEFINE3(symlinkat
, const char __user
*, oldname
,
3868 int, newdfd
, const char __user
*, newname
)
3871 struct filename
*from
;
3872 struct dentry
*dentry
;
3874 unsigned int lookup_flags
= 0;
3876 from
= getname(oldname
);
3878 return PTR_ERR(from
);
3880 dentry
= user_path_create(newdfd
, newname
, &path
, lookup_flags
);
3881 error
= PTR_ERR(dentry
);
3885 error
= security_path_symlink(&path
, dentry
, from
->name
);
3887 error
= vfs_symlink(path
.dentry
->d_inode
, dentry
, from
->name
);
3888 done_path_create(&path
, dentry
);
3889 if (retry_estale(error
, lookup_flags
)) {
3890 lookup_flags
|= LOOKUP_REVAL
;
3898 SYSCALL_DEFINE2(symlink
, const char __user
*, oldname
, const char __user
*, newname
)
3900 return sys_symlinkat(oldname
, AT_FDCWD
, newname
);
3904 * vfs_link - create a new link
3905 * @old_dentry: object to be linked
3907 * @new_dentry: where to create the new link
3908 * @delegated_inode: returns inode needing a delegation break
3910 * The caller must hold dir->i_mutex
3912 * If vfs_link discovers a delegation on the to-be-linked file in need
3913 * of breaking, it will return -EWOULDBLOCK and return a reference to the
3914 * inode in delegated_inode. The caller should then break the delegation
3915 * and retry. Because breaking a delegation may take a long time, the
3916 * caller should drop the i_mutex before doing so.
3918 * Alternatively, a caller may pass NULL for delegated_inode. This may
3919 * be appropriate for callers that expect the underlying filesystem not
3920 * to be NFS exported.
3922 int vfs_link(struct dentry
*old_dentry
, struct inode
*dir
, struct dentry
*new_dentry
, struct inode
**delegated_inode
)
3924 struct inode
*inode
= old_dentry
->d_inode
;
3925 unsigned max_links
= dir
->i_sb
->s_max_links
;
3931 error
= may_create(dir
, new_dentry
);
3935 if (dir
->i_sb
!= inode
->i_sb
)
3939 * A link to an append-only or immutable file cannot be created.
3941 if (IS_APPEND(inode
) || IS_IMMUTABLE(inode
))
3943 if (!dir
->i_op
->link
)
3945 if (S_ISDIR(inode
->i_mode
))
3948 error
= security_inode_link(old_dentry
, dir
, new_dentry
);
3952 mutex_lock(&inode
->i_mutex
);
3953 /* Make sure we don't allow creating hardlink to an unlinked file */
3954 if (inode
->i_nlink
== 0 && !(inode
->i_state
& I_LINKABLE
))
3956 else if (max_links
&& inode
->i_nlink
>= max_links
)
3959 error
= try_break_deleg(inode
, delegated_inode
);
3961 error
= dir
->i_op
->link(old_dentry
, dir
, new_dentry
);
3964 if (!error
&& (inode
->i_state
& I_LINKABLE
)) {
3965 spin_lock(&inode
->i_lock
);
3966 inode
->i_state
&= ~I_LINKABLE
;
3967 spin_unlock(&inode
->i_lock
);
3969 mutex_unlock(&inode
->i_mutex
);
3971 fsnotify_link(dir
, inode
, new_dentry
);
3974 EXPORT_SYMBOL(vfs_link
);
3977 * Hardlinks are often used in delicate situations. We avoid
3978 * security-related surprises by not following symlinks on the
3981 * We don't follow them on the oldname either to be compatible
3982 * with linux 2.0, and to avoid hard-linking to directories
3983 * and other special files. --ADM
3985 SYSCALL_DEFINE5(linkat
, int, olddfd
, const char __user
*, oldname
,
3986 int, newdfd
, const char __user
*, newname
, int, flags
)
3988 struct dentry
*new_dentry
;
3989 struct path old_path
, new_path
;
3990 struct inode
*delegated_inode
= NULL
;
3994 if ((flags
& ~(AT_SYMLINK_FOLLOW
| AT_EMPTY_PATH
)) != 0)
3997 * To use null names we require CAP_DAC_READ_SEARCH
3998 * This ensures that not everyone will be able to create
3999 * handlink using the passed filedescriptor.
4001 if (flags
& AT_EMPTY_PATH
) {
4002 if (!capable(CAP_DAC_READ_SEARCH
))
4007 if (flags
& AT_SYMLINK_FOLLOW
)
4008 how
|= LOOKUP_FOLLOW
;
4010 error
= user_path_at(olddfd
, oldname
, how
, &old_path
);
4014 new_dentry
= user_path_create(newdfd
, newname
, &new_path
,
4015 (how
& LOOKUP_REVAL
));
4016 error
= PTR_ERR(new_dentry
);
4017 if (IS_ERR(new_dentry
))
4021 if (old_path
.mnt
!= new_path
.mnt
)
4023 error
= may_linkat(&old_path
);
4024 if (unlikely(error
))
4026 error
= security_path_link(old_path
.dentry
, &new_path
, new_dentry
);
4029 error
= vfs_link(old_path
.dentry
, new_path
.dentry
->d_inode
, new_dentry
, &delegated_inode
);
4031 done_path_create(&new_path
, new_dentry
);
4032 if (delegated_inode
) {
4033 error
= break_deleg_wait(&delegated_inode
);
4035 path_put(&old_path
);
4039 if (retry_estale(error
, how
)) {
4040 path_put(&old_path
);
4041 how
|= LOOKUP_REVAL
;
4045 path_put(&old_path
);
4050 SYSCALL_DEFINE2(link
, const char __user
*, oldname
, const char __user
*, newname
)
4052 return sys_linkat(AT_FDCWD
, oldname
, AT_FDCWD
, newname
, 0);
4056 * vfs_rename - rename a filesystem object
4057 * @old_dir: parent of source
4058 * @old_dentry: source
4059 * @new_dir: parent of destination
4060 * @new_dentry: destination
4061 * @delegated_inode: returns an inode needing a delegation break
4062 * @flags: rename flags
4064 * The caller must hold multiple mutexes--see lock_rename()).
4066 * If vfs_rename discovers a delegation in need of breaking at either
4067 * the source or destination, it will return -EWOULDBLOCK and return a
4068 * reference to the inode in delegated_inode. The caller should then
4069 * break the delegation and retry. Because breaking a delegation may
4070 * take a long time, the caller should drop all locks before doing
4073 * Alternatively, a caller may pass NULL for delegated_inode. This may
4074 * be appropriate for callers that expect the underlying filesystem not
4075 * to be NFS exported.
4077 * The worst of all namespace operations - renaming directory. "Perverted"
4078 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
4080 * a) we can get into loop creation.
4081 * b) race potential - two innocent renames can create a loop together.
4082 * That's where 4.4 screws up. Current fix: serialization on
4083 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
4085 * c) we have to lock _four_ objects - parents and victim (if it exists),
4086 * and source (if it is not a directory).
4087 * And that - after we got ->i_mutex on parents (until then we don't know
4088 * whether the target exists). Solution: try to be smart with locking
4089 * order for inodes. We rely on the fact that tree topology may change
4090 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
4091 * move will be locked. Thus we can rank directories by the tree
4092 * (ancestors first) and rank all non-directories after them.
4093 * That works since everybody except rename does "lock parent, lookup,
4094 * lock child" and rename is under ->s_vfs_rename_mutex.
4095 * HOWEVER, it relies on the assumption that any object with ->lookup()
4096 * has no more than 1 dentry. If "hybrid" objects will ever appear,
4097 * we'd better make sure that there's no link(2) for them.
4098 * d) conversion from fhandle to dentry may come in the wrong moment - when
4099 * we are removing the target. Solution: we will have to grab ->i_mutex
4100 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
4101 * ->i_mutex on parents, which works but leads to some truly excessive
4104 int vfs_rename(struct inode
*old_dir
, struct dentry
*old_dentry
,
4105 struct inode
*new_dir
, struct dentry
*new_dentry
,
4106 struct inode
**delegated_inode
, unsigned int flags
)
4109 bool is_dir
= d_is_dir(old_dentry
);
4110 const unsigned char *old_name
;
4111 struct inode
*source
= old_dentry
->d_inode
;
4112 struct inode
*target
= new_dentry
->d_inode
;
4113 bool new_is_dir
= false;
4114 unsigned max_links
= new_dir
->i_sb
->s_max_links
;
4116 if (source
== target
)
4119 error
= may_delete(old_dir
, old_dentry
, is_dir
);
4124 error
= may_create(new_dir
, new_dentry
);
4126 new_is_dir
= d_is_dir(new_dentry
);
4128 if (!(flags
& RENAME_EXCHANGE
))
4129 error
= may_delete(new_dir
, new_dentry
, is_dir
);
4131 error
= may_delete(new_dir
, new_dentry
, new_is_dir
);
4136 if (!old_dir
->i_op
->rename
&& !old_dir
->i_op
->rename2
)
4139 if (flags
&& !old_dir
->i_op
->rename2
)
4143 * If we are going to change the parent - check write permissions,
4144 * we'll need to flip '..'.
4146 if (new_dir
!= old_dir
) {
4148 error
= inode_permission(source
, MAY_WRITE
);
4152 if ((flags
& RENAME_EXCHANGE
) && new_is_dir
) {
4153 error
= inode_permission(target
, MAY_WRITE
);
4159 error
= security_inode_rename(old_dir
, old_dentry
, new_dir
, new_dentry
,
4164 old_name
= fsnotify_oldname_init(old_dentry
->d_name
.name
);
4166 if (!is_dir
|| (flags
& RENAME_EXCHANGE
))
4167 lock_two_nondirectories(source
, target
);
4169 mutex_lock(&target
->i_mutex
);
4172 if (is_local_mountpoint(old_dentry
) || is_local_mountpoint(new_dentry
))
4175 if (max_links
&& new_dir
!= old_dir
) {
4177 if (is_dir
&& !new_is_dir
&& new_dir
->i_nlink
>= max_links
)
4179 if ((flags
& RENAME_EXCHANGE
) && !is_dir
&& new_is_dir
&&
4180 old_dir
->i_nlink
>= max_links
)
4183 if (is_dir
&& !(flags
& RENAME_EXCHANGE
) && target
)
4184 shrink_dcache_parent(new_dentry
);
4186 error
= try_break_deleg(source
, delegated_inode
);
4190 if (target
&& !new_is_dir
) {
4191 error
= try_break_deleg(target
, delegated_inode
);
4195 if (!old_dir
->i_op
->rename2
) {
4196 error
= old_dir
->i_op
->rename(old_dir
, old_dentry
,
4197 new_dir
, new_dentry
);
4199 WARN_ON(old_dir
->i_op
->rename
!= NULL
);
4200 error
= old_dir
->i_op
->rename2(old_dir
, old_dentry
,
4201 new_dir
, new_dentry
, flags
);
4206 if (!(flags
& RENAME_EXCHANGE
) && target
) {
4208 target
->i_flags
|= S_DEAD
;
4209 dont_mount(new_dentry
);
4210 detach_mounts(new_dentry
);
4212 if (!(old_dir
->i_sb
->s_type
->fs_flags
& FS_RENAME_DOES_D_MOVE
)) {
4213 if (!(flags
& RENAME_EXCHANGE
))
4214 d_move(old_dentry
, new_dentry
);
4216 d_exchange(old_dentry
, new_dentry
);
4219 if (!is_dir
|| (flags
& RENAME_EXCHANGE
))
4220 unlock_two_nondirectories(source
, target
);
4222 mutex_unlock(&target
->i_mutex
);
4225 fsnotify_move(old_dir
, new_dir
, old_name
, is_dir
,
4226 !(flags
& RENAME_EXCHANGE
) ? target
: NULL
, old_dentry
);
4227 if (flags
& RENAME_EXCHANGE
) {
4228 fsnotify_move(new_dir
, old_dir
, old_dentry
->d_name
.name
,
4229 new_is_dir
, NULL
, new_dentry
);
4232 fsnotify_oldname_free(old_name
);
4236 EXPORT_SYMBOL(vfs_rename
);
4238 SYSCALL_DEFINE5(renameat2
, int, olddfd
, const char __user
*, oldname
,
4239 int, newdfd
, const char __user
*, newname
, unsigned int, flags
)
4241 struct dentry
*old_dentry
, *new_dentry
;
4242 struct dentry
*trap
;
4243 struct path old_path
, new_path
;
4244 struct qstr old_last
, new_last
;
4245 int old_type
, new_type
;
4246 struct inode
*delegated_inode
= NULL
;
4247 struct filename
*from
;
4248 struct filename
*to
;
4249 unsigned int lookup_flags
= 0, target_flags
= LOOKUP_RENAME_TARGET
;
4250 bool should_retry
= false;
4253 if (flags
& ~(RENAME_NOREPLACE
| RENAME_EXCHANGE
| RENAME_WHITEOUT
))
4256 if ((flags
& (RENAME_NOREPLACE
| RENAME_WHITEOUT
)) &&
4257 (flags
& RENAME_EXCHANGE
))
4260 if ((flags
& RENAME_WHITEOUT
) && !capable(CAP_MKNOD
))
4263 if (flags
& RENAME_EXCHANGE
)
4267 from
= user_path_parent(olddfd
, oldname
,
4268 &old_path
, &old_last
, &old_type
, lookup_flags
);
4270 error
= PTR_ERR(from
);
4274 to
= user_path_parent(newdfd
, newname
,
4275 &new_path
, &new_last
, &new_type
, lookup_flags
);
4277 error
= PTR_ERR(to
);
4282 if (old_path
.mnt
!= new_path
.mnt
)
4286 if (old_type
!= LAST_NORM
)
4289 if (flags
& RENAME_NOREPLACE
)
4291 if (new_type
!= LAST_NORM
)
4294 error
= mnt_want_write(old_path
.mnt
);
4299 trap
= lock_rename(new_path
.dentry
, old_path
.dentry
);
4301 old_dentry
= __lookup_hash(&old_last
, old_path
.dentry
, lookup_flags
);
4302 error
= PTR_ERR(old_dentry
);
4303 if (IS_ERR(old_dentry
))
4305 /* source must exist */
4307 if (d_is_negative(old_dentry
))
4309 new_dentry
= __lookup_hash(&new_last
, new_path
.dentry
, lookup_flags
| target_flags
);
4310 error
= PTR_ERR(new_dentry
);
4311 if (IS_ERR(new_dentry
))
4314 if ((flags
& RENAME_NOREPLACE
) && d_is_positive(new_dentry
))
4316 if (flags
& RENAME_EXCHANGE
) {
4318 if (d_is_negative(new_dentry
))
4321 if (!d_is_dir(new_dentry
)) {
4323 if (new_last
.name
[new_last
.len
])
4327 /* unless the source is a directory trailing slashes give -ENOTDIR */
4328 if (!d_is_dir(old_dentry
)) {
4330 if (old_last
.name
[old_last
.len
])
4332 if (!(flags
& RENAME_EXCHANGE
) && new_last
.name
[new_last
.len
])
4335 /* source should not be ancestor of target */
4337 if (old_dentry
== trap
)
4339 /* target should not be an ancestor of source */
4340 if (!(flags
& RENAME_EXCHANGE
))
4342 if (new_dentry
== trap
)
4345 error
= security_path_rename(&old_path
, old_dentry
,
4346 &new_path
, new_dentry
, flags
);
4349 error
= vfs_rename(old_path
.dentry
->d_inode
, old_dentry
,
4350 new_path
.dentry
->d_inode
, new_dentry
,
4351 &delegated_inode
, flags
);
4357 unlock_rename(new_path
.dentry
, old_path
.dentry
);
4358 if (delegated_inode
) {
4359 error
= break_deleg_wait(&delegated_inode
);
4363 mnt_drop_write(old_path
.mnt
);
4365 if (retry_estale(error
, lookup_flags
))
4366 should_retry
= true;
4367 path_put(&new_path
);
4370 path_put(&old_path
);
4373 should_retry
= false;
4374 lookup_flags
|= LOOKUP_REVAL
;
4381 SYSCALL_DEFINE4(renameat
, int, olddfd
, const char __user
*, oldname
,
4382 int, newdfd
, const char __user
*, newname
)
4384 return sys_renameat2(olddfd
, oldname
, newdfd
, newname
, 0);
4387 SYSCALL_DEFINE2(rename
, const char __user
*, oldname
, const char __user
*, newname
)
4389 return sys_renameat2(AT_FDCWD
, oldname
, AT_FDCWD
, newname
, 0);
4392 int vfs_whiteout(struct inode
*dir
, struct dentry
*dentry
)
4394 int error
= may_create(dir
, dentry
);
4398 if (!dir
->i_op
->mknod
)
4401 return dir
->i_op
->mknod(dir
, dentry
,
4402 S_IFCHR
| WHITEOUT_MODE
, WHITEOUT_DEV
);
4404 EXPORT_SYMBOL(vfs_whiteout
);
4406 int readlink_copy(char __user
*buffer
, int buflen
, const char *link
)
4408 int len
= PTR_ERR(link
);
4413 if (len
> (unsigned) buflen
)
4415 if (copy_to_user(buffer
, link
, len
))
4420 EXPORT_SYMBOL(readlink_copy
);
4423 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
4424 * have ->follow_link() touching nd only in nd_set_link(). Using (or not
4425 * using) it for any given inode is up to filesystem.
4427 int generic_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
)
4430 const char *link
= dentry
->d_inode
->i_link
;
4434 link
= dentry
->d_inode
->i_op
->follow_link(dentry
, &cookie
, NULL
);
4436 return PTR_ERR(link
);
4438 res
= readlink_copy(buffer
, buflen
, link
);
4439 if (cookie
&& dentry
->d_inode
->i_op
->put_link
)
4440 dentry
->d_inode
->i_op
->put_link(dentry
, cookie
);
4443 EXPORT_SYMBOL(generic_readlink
);
4445 /* get the link contents into pagecache */
4446 static char *page_getlink(struct dentry
* dentry
, struct page
**ppage
)
4450 struct address_space
*mapping
= dentry
->d_inode
->i_mapping
;
4451 page
= read_mapping_page(mapping
, 0, NULL
);
4456 nd_terminate_link(kaddr
, dentry
->d_inode
->i_size
, PAGE_SIZE
- 1);
4460 int page_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
)
4462 struct page
*page
= NULL
;
4463 int res
= readlink_copy(buffer
, buflen
, page_getlink(dentry
, &page
));
4466 page_cache_release(page
);
4470 EXPORT_SYMBOL(page_readlink
);
4472 const char *page_follow_link_light(struct dentry
*dentry
, void **cookie
, struct nameidata
*nd
)
4474 struct page
*page
= NULL
;
4475 char *res
= page_getlink(dentry
, &page
);
4480 EXPORT_SYMBOL(page_follow_link_light
);
4482 void page_put_link(struct dentry
*dentry
, void *cookie
)
4484 struct page
*page
= cookie
;
4486 page_cache_release(page
);
4488 EXPORT_SYMBOL(page_put_link
);
4491 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
4493 int __page_symlink(struct inode
*inode
, const char *symname
, int len
, int nofs
)
4495 struct address_space
*mapping
= inode
->i_mapping
;
4500 unsigned int flags
= AOP_FLAG_UNINTERRUPTIBLE
;
4502 flags
|= AOP_FLAG_NOFS
;
4505 err
= pagecache_write_begin(NULL
, mapping
, 0, len
-1,
4506 flags
, &page
, &fsdata
);
4510 kaddr
= kmap_atomic(page
);
4511 memcpy(kaddr
, symname
, len
-1);
4512 kunmap_atomic(kaddr
);
4514 err
= pagecache_write_end(NULL
, mapping
, 0, len
-1, len
-1,
4521 mark_inode_dirty(inode
);
4526 EXPORT_SYMBOL(__page_symlink
);
4528 int page_symlink(struct inode
*inode
, const char *symname
, int len
)
4530 return __page_symlink(inode
, symname
, len
,
4531 !(mapping_gfp_mask(inode
->i_mapping
) & __GFP_FS
));
4533 EXPORT_SYMBOL(page_symlink
);
4535 const struct inode_operations page_symlink_inode_operations
= {
4536 .readlink
= generic_readlink
,
4537 .follow_link
= page_follow_link_light
,
4538 .put_link
= page_put_link
,
4540 EXPORT_SYMBOL(page_symlink_inode_operations
);