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/module.h>
19 #include <linux/slab.h>
21 #include <linux/namei.h>
22 #include <linux/pagemap.h>
23 #include <linux/fsnotify.h>
24 #include <linux/personality.h>
25 #include <linux/security.h>
26 #include <linux/ima.h>
27 #include <linux/syscalls.h>
28 #include <linux/mount.h>
29 #include <linux/audit.h>
30 #include <linux/capability.h>
31 #include <linux/file.h>
32 #include <linux/fcntl.h>
33 #include <linux/device_cgroup.h>
34 #include <linux/fs_struct.h>
35 #include <asm/uaccess.h>
39 /* [Feb-1997 T. Schoebel-Theuer]
40 * Fundamental changes in the pathname lookup mechanisms (namei)
41 * were necessary because of omirr. The reason is that omirr needs
42 * to know the _real_ pathname, not the user-supplied one, in case
43 * of symlinks (and also when transname replacements occur).
45 * The new code replaces the old recursive symlink resolution with
46 * an iterative one (in case of non-nested symlink chains). It does
47 * this with calls to <fs>_follow_link().
48 * As a side effect, dir_namei(), _namei() and follow_link() are now
49 * replaced with a single function lookup_dentry() that can handle all
50 * the special cases of the former code.
52 * With the new dcache, the pathname is stored at each inode, at least as
53 * long as the refcount of the inode is positive. As a side effect, the
54 * size of the dcache depends on the inode cache and thus is dynamic.
56 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
57 * resolution to correspond with current state of the code.
59 * Note that the symlink resolution is not *completely* iterative.
60 * There is still a significant amount of tail- and mid- recursion in
61 * the algorithm. Also, note that <fs>_readlink() is not used in
62 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
63 * may return different results than <fs>_follow_link(). Many virtual
64 * filesystems (including /proc) exhibit this behavior.
67 /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
68 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
69 * and the name already exists in form of a symlink, try to create the new
70 * name indicated by the symlink. The old code always complained that the
71 * name already exists, due to not following the symlink even if its target
72 * is nonexistent. The new semantics affects also mknod() and link() when
73 * the name is a symlink pointing to a non-existant name.
75 * I don't know which semantics is the right one, since I have no access
76 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
77 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
78 * "old" one. Personally, I think the new semantics is much more logical.
79 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
80 * file does succeed in both HP-UX and SunOs, but not in Solaris
81 * and in the old Linux semantics.
84 /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
85 * semantics. See the comments in "open_namei" and "do_link" below.
87 * [10-Sep-98 Alan Modra] Another symlink change.
90 /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
91 * inside the path - always follow.
92 * in the last component in creation/removal/renaming - never follow.
93 * if LOOKUP_FOLLOW passed - follow.
94 * if the pathname has trailing slashes - follow.
95 * otherwise - don't follow.
96 * (applied in that order).
98 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
99 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
100 * During the 2.4 we need to fix the userland stuff depending on it -
101 * hopefully we will be able to get rid of that wart in 2.5. So far only
102 * XEmacs seems to be relying on it...
105 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
106 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
107 * any extra contention...
110 /* In order to reduce some races, while at the same time doing additional
111 * checking and hopefully speeding things up, we copy filenames to the
112 * kernel data space before using them..
114 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
115 * PATH_MAX includes the nul terminator --RR.
117 static int do_getname(const char __user
*filename
, char *page
)
120 unsigned long len
= PATH_MAX
;
122 if (!segment_eq(get_fs(), KERNEL_DS
)) {
123 if ((unsigned long) filename
>= TASK_SIZE
)
125 if (TASK_SIZE
- (unsigned long) filename
< PATH_MAX
)
126 len
= TASK_SIZE
- (unsigned long) filename
;
129 retval
= strncpy_from_user(page
, filename
, len
);
133 return -ENAMETOOLONG
;
139 static char *getname_flags(const char __user
* filename
, int flags
)
143 result
= ERR_PTR(-ENOMEM
);
146 int retval
= do_getname(filename
, tmp
);
150 if (retval
!= -ENOENT
|| !(flags
& LOOKUP_EMPTY
)) {
152 result
= ERR_PTR(retval
);
156 audit_getname(result
);
160 char *getname(const char __user
* filename
)
162 return getname_flags(filename
, 0);
165 #ifdef CONFIG_AUDITSYSCALL
166 void putname(const char *name
)
168 if (unlikely(!audit_dummy_context()))
173 EXPORT_SYMBOL(putname
);
177 * This does basic POSIX ACL permission checking
179 static int acl_permission_check(struct inode
*inode
, int mask
, unsigned int flags
,
180 int (*check_acl
)(struct inode
*inode
, int mask
, unsigned int flags
))
182 umode_t mode
= inode
->i_mode
;
184 mask
&= MAY_READ
| MAY_WRITE
| MAY_EXEC
;
186 if (current_fsuid() == inode
->i_uid
)
189 if (IS_POSIXACL(inode
) && (mode
& S_IRWXG
) && check_acl
) {
190 int error
= check_acl(inode
, mask
, flags
);
191 if (error
!= -EAGAIN
)
195 if (in_group_p(inode
->i_gid
))
200 * If the DACs are ok we don't need any capability check.
202 if ((mask
& ~mode
) == 0)
208 * generic_permission - check for access rights on a Posix-like filesystem
209 * @inode: inode to check access rights for
210 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
211 * @check_acl: optional callback to check for Posix ACLs
212 * @flags: IPERM_FLAG_ flags.
214 * Used to check for read/write/execute permissions on a file.
215 * We use "fsuid" for this, letting us set arbitrary permissions
216 * for filesystem access without changing the "normal" uids which
217 * are used for other things.
219 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
220 * request cannot be satisfied (eg. requires blocking or too much complexity).
221 * It would then be called again in ref-walk mode.
223 int generic_permission(struct inode
*inode
, int mask
, unsigned int flags
,
224 int (*check_acl
)(struct inode
*inode
, int mask
, unsigned int flags
))
229 * Do the basic POSIX ACL permission checks.
231 ret
= acl_permission_check(inode
, mask
, flags
, check_acl
);
236 * Read/write DACs are always overridable.
237 * Executable DACs are overridable if at least one exec bit is set.
239 if (!(mask
& MAY_EXEC
) || execute_ok(inode
))
240 if (capable(CAP_DAC_OVERRIDE
))
244 * Searching includes executable on directories, else just read.
246 mask
&= MAY_READ
| MAY_WRITE
| MAY_EXEC
;
247 if (mask
== MAY_READ
|| (S_ISDIR(inode
->i_mode
) && !(mask
& MAY_WRITE
)))
248 if (capable(CAP_DAC_READ_SEARCH
))
255 * inode_permission - check for access rights to a given inode
256 * @inode: inode to check permission on
257 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
259 * Used to check for read/write/execute permissions on an inode.
260 * We use "fsuid" for this, letting us set arbitrary permissions
261 * for filesystem access without changing the "normal" uids which
262 * are used for other things.
264 int inode_permission(struct inode
*inode
, int mask
)
268 if (mask
& MAY_WRITE
) {
269 umode_t mode
= inode
->i_mode
;
272 * Nobody gets write access to a read-only fs.
274 if (IS_RDONLY(inode
) &&
275 (S_ISREG(mode
) || S_ISDIR(mode
) || S_ISLNK(mode
)))
279 * Nobody gets write access to an immutable file.
281 if (IS_IMMUTABLE(inode
))
285 if (inode
->i_op
->permission
)
286 retval
= inode
->i_op
->permission(inode
, mask
, 0);
288 retval
= generic_permission(inode
, mask
, 0,
289 inode
->i_op
->check_acl
);
294 retval
= devcgroup_inode_permission(inode
, mask
);
298 return security_inode_permission(inode
, mask
);
302 * file_permission - check for additional access rights to a given file
303 * @file: file to check access rights for
304 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
306 * Used to check for read/write/execute permissions on an already opened
310 * Do not use this function in new code. All access checks should
311 * be done using inode_permission().
313 int file_permission(struct file
*file
, int mask
)
315 return inode_permission(file
->f_path
.dentry
->d_inode
, mask
);
319 * get_write_access() gets write permission for a file.
320 * put_write_access() releases this write permission.
321 * This is used for regular files.
322 * We cannot support write (and maybe mmap read-write shared) accesses and
323 * MAP_DENYWRITE mmappings simultaneously. The i_writecount field of an inode
324 * can have the following values:
325 * 0: no writers, no VM_DENYWRITE mappings
326 * < 0: (-i_writecount) vm_area_structs with VM_DENYWRITE set exist
327 * > 0: (i_writecount) users are writing to the file.
329 * Normally we operate on that counter with atomic_{inc,dec} and it's safe
330 * except for the cases where we don't hold i_writecount yet. Then we need to
331 * use {get,deny}_write_access() - these functions check the sign and refuse
332 * to do the change if sign is wrong. Exclusion between them is provided by
333 * the inode->i_lock spinlock.
336 int get_write_access(struct inode
* inode
)
338 spin_lock(&inode
->i_lock
);
339 if (atomic_read(&inode
->i_writecount
) < 0) {
340 spin_unlock(&inode
->i_lock
);
343 atomic_inc(&inode
->i_writecount
);
344 spin_unlock(&inode
->i_lock
);
349 int deny_write_access(struct file
* file
)
351 struct inode
*inode
= file
->f_path
.dentry
->d_inode
;
353 spin_lock(&inode
->i_lock
);
354 if (atomic_read(&inode
->i_writecount
) > 0) {
355 spin_unlock(&inode
->i_lock
);
358 atomic_dec(&inode
->i_writecount
);
359 spin_unlock(&inode
->i_lock
);
365 * path_get - get a reference to a path
366 * @path: path to get the reference to
368 * Given a path increment the reference count to the dentry and the vfsmount.
370 void path_get(struct path
*path
)
375 EXPORT_SYMBOL(path_get
);
378 * path_put - put a reference to a path
379 * @path: path to put the reference to
381 * Given a path decrement the reference count to the dentry and the vfsmount.
383 void path_put(struct path
*path
)
388 EXPORT_SYMBOL(path_put
);
391 * nameidata_drop_rcu - drop this nameidata out of rcu-walk
392 * @nd: nameidata pathwalk data to drop
393 * Returns: 0 on success, -ECHILD on failure
395 * Path walking has 2 modes, rcu-walk and ref-walk (see
396 * Documentation/filesystems/path-lookup.txt). __drop_rcu* functions attempt
397 * to drop out of rcu-walk mode and take normal reference counts on dentries
398 * and vfsmounts to transition to rcu-walk mode. __drop_rcu* functions take
399 * refcounts at the last known good point before rcu-walk got stuck, so
400 * ref-walk may continue from there. If this is not successful (eg. a seqcount
401 * has changed), then failure is returned and path walk restarts from the
402 * beginning in ref-walk mode.
404 * nameidata_drop_rcu attempts to drop the current nd->path and nd->root into
405 * ref-walk. Must be called from rcu-walk context.
407 static int nameidata_drop_rcu(struct nameidata
*nd
)
409 struct fs_struct
*fs
= current
->fs
;
410 struct dentry
*dentry
= nd
->path
.dentry
;
413 BUG_ON(!(nd
->flags
& LOOKUP_RCU
));
414 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
)) {
416 spin_lock(&fs
->lock
);
417 if (nd
->root
.mnt
!= fs
->root
.mnt
||
418 nd
->root
.dentry
!= fs
->root
.dentry
)
421 spin_lock(&dentry
->d_lock
);
422 if (!__d_rcu_to_refcount(dentry
, nd
->seq
))
424 BUG_ON(nd
->inode
!= dentry
->d_inode
);
425 spin_unlock(&dentry
->d_lock
);
428 spin_unlock(&fs
->lock
);
430 mntget(nd
->path
.mnt
);
433 br_read_unlock(vfsmount_lock
);
434 nd
->flags
&= ~LOOKUP_RCU
;
437 spin_unlock(&dentry
->d_lock
);
440 spin_unlock(&fs
->lock
);
444 /* Try to drop out of rcu-walk mode if we were in it, otherwise do nothing. */
445 static inline int nameidata_drop_rcu_maybe(struct nameidata
*nd
)
447 if (nd
->flags
& LOOKUP_RCU
)
448 return nameidata_drop_rcu(nd
);
453 * nameidata_dentry_drop_rcu - drop nameidata and dentry out of rcu-walk
454 * @nd: nameidata pathwalk data to drop
455 * @dentry: dentry to drop
456 * Returns: 0 on success, -ECHILD on failure
458 * nameidata_dentry_drop_rcu attempts to drop the current nd->path and nd->root,
459 * and dentry into ref-walk. @dentry must be a path found by a do_lookup call on
460 * @nd. Must be called from rcu-walk context.
462 static int nameidata_dentry_drop_rcu(struct nameidata
*nd
, struct dentry
*dentry
)
464 struct fs_struct
*fs
= current
->fs
;
465 struct dentry
*parent
= nd
->path
.dentry
;
468 BUG_ON(!(nd
->flags
& LOOKUP_RCU
));
469 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
)) {
471 spin_lock(&fs
->lock
);
472 if (nd
->root
.mnt
!= fs
->root
.mnt
||
473 nd
->root
.dentry
!= fs
->root
.dentry
)
476 spin_lock(&parent
->d_lock
);
477 spin_lock_nested(&dentry
->d_lock
, DENTRY_D_LOCK_NESTED
);
478 if (!__d_rcu_to_refcount(dentry
, nd
->seq
))
481 * If the sequence check on the child dentry passed, then the child has
482 * not been removed from its parent. This means the parent dentry must
483 * be valid and able to take a reference at this point.
485 BUG_ON(!IS_ROOT(dentry
) && dentry
->d_parent
!= parent
);
486 BUG_ON(!parent
->d_count
);
488 spin_unlock(&dentry
->d_lock
);
489 spin_unlock(&parent
->d_lock
);
492 spin_unlock(&fs
->lock
);
494 mntget(nd
->path
.mnt
);
497 br_read_unlock(vfsmount_lock
);
498 nd
->flags
&= ~LOOKUP_RCU
;
501 spin_unlock(&dentry
->d_lock
);
502 spin_unlock(&parent
->d_lock
);
505 spin_unlock(&fs
->lock
);
509 /* Try to drop out of rcu-walk mode if we were in it, otherwise do nothing. */
510 static inline int nameidata_dentry_drop_rcu_maybe(struct nameidata
*nd
, struct dentry
*dentry
)
512 if (nd
->flags
& LOOKUP_RCU
) {
513 if (unlikely(nameidata_dentry_drop_rcu(nd
, dentry
))) {
514 nd
->flags
&= ~LOOKUP_RCU
;
515 if (!(nd
->flags
& LOOKUP_ROOT
))
518 br_read_unlock(vfsmount_lock
);
526 * nameidata_drop_rcu_last - drop nameidata ending path walk out of rcu-walk
527 * @nd: nameidata pathwalk data to drop
528 * Returns: 0 on success, -ECHILD on failure
530 * nameidata_drop_rcu_last attempts to drop the current nd->path into ref-walk.
531 * nd->path should be the final element of the lookup, so nd->root is discarded.
532 * Must be called from rcu-walk context.
534 static int nameidata_drop_rcu_last(struct nameidata
*nd
)
536 struct dentry
*dentry
= nd
->path
.dentry
;
538 BUG_ON(!(nd
->flags
& LOOKUP_RCU
));
539 nd
->flags
&= ~LOOKUP_RCU
;
540 if (!(nd
->flags
& LOOKUP_ROOT
))
542 spin_lock(&dentry
->d_lock
);
543 if (!__d_rcu_to_refcount(dentry
, nd
->seq
))
545 BUG_ON(nd
->inode
!= dentry
->d_inode
);
546 spin_unlock(&dentry
->d_lock
);
548 mntget(nd
->path
.mnt
);
551 br_read_unlock(vfsmount_lock
);
556 spin_unlock(&dentry
->d_lock
);
558 br_read_unlock(vfsmount_lock
);
563 * release_open_intent - free up open intent resources
564 * @nd: pointer to nameidata
566 void release_open_intent(struct nameidata
*nd
)
568 struct file
*file
= nd
->intent
.open
.file
;
570 if (file
&& !IS_ERR(file
)) {
571 if (file
->f_path
.dentry
== NULL
)
578 static inline int d_revalidate(struct dentry
*dentry
, struct nameidata
*nd
)
580 return dentry
->d_op
->d_revalidate(dentry
, nd
);
583 static struct dentry
*
584 do_revalidate(struct dentry
*dentry
, struct nameidata
*nd
)
586 int status
= d_revalidate(dentry
, nd
);
587 if (unlikely(status
<= 0)) {
589 * The dentry failed validation.
590 * If d_revalidate returned 0 attempt to invalidate
591 * the dentry otherwise d_revalidate is asking us
592 * to return a fail status.
596 dentry
= ERR_PTR(status
);
597 } else if (!d_invalidate(dentry
)) {
606 * handle_reval_path - force revalidation of a dentry
608 * In some situations the path walking code will trust dentries without
609 * revalidating them. This causes problems for filesystems that depend on
610 * d_revalidate to handle file opens (e.g. NFSv4). When FS_REVAL_DOT is set
611 * (which indicates that it's possible for the dentry to go stale), force
612 * a d_revalidate call before proceeding.
614 * Returns 0 if the revalidation was successful. If the revalidation fails,
615 * either return the error returned by d_revalidate or -ESTALE if the
616 * revalidation it just returned 0. If d_revalidate returns 0, we attempt to
617 * invalidate the dentry. It's up to the caller to handle putting references
618 * to the path if necessary.
620 static inline int handle_reval_path(struct nameidata
*nd
)
622 struct dentry
*dentry
= nd
->path
.dentry
;
625 if (likely(!(nd
->flags
& LOOKUP_JUMPED
)))
628 if (likely(!(dentry
->d_flags
& DCACHE_OP_REVALIDATE
)))
631 if (likely(!(dentry
->d_sb
->s_type
->fs_flags
& FS_REVAL_DOT
)))
634 /* Note: we do not d_invalidate() */
635 status
= d_revalidate(dentry
, nd
);
646 * Short-cut version of permission(), for calling on directories
647 * during pathname resolution. Combines parts of permission()
648 * and generic_permission(), and tests ONLY for MAY_EXEC permission.
650 * If appropriate, check DAC only. If not appropriate, or
651 * short-cut DAC fails, then call ->permission() to do more
652 * complete permission check.
654 static inline int exec_permission(struct inode
*inode
, unsigned int flags
)
658 if (inode
->i_op
->permission
) {
659 ret
= inode
->i_op
->permission(inode
, MAY_EXEC
, flags
);
661 ret
= acl_permission_check(inode
, MAY_EXEC
, flags
,
662 inode
->i_op
->check_acl
);
669 if (capable(CAP_DAC_OVERRIDE
) || capable(CAP_DAC_READ_SEARCH
))
674 return security_inode_exec_permission(inode
, flags
);
677 static __always_inline
void set_root(struct nameidata
*nd
)
680 get_fs_root(current
->fs
, &nd
->root
);
683 static int link_path_walk(const char *, struct nameidata
*);
685 static __always_inline
void set_root_rcu(struct nameidata
*nd
)
688 struct fs_struct
*fs
= current
->fs
;
692 seq
= read_seqcount_begin(&fs
->seq
);
694 } while (read_seqcount_retry(&fs
->seq
, seq
));
698 static __always_inline
int __vfs_follow_link(struct nameidata
*nd
, const char *link
)
710 nd
->flags
|= LOOKUP_JUMPED
;
712 nd
->inode
= nd
->path
.dentry
->d_inode
;
714 ret
= link_path_walk(link
, nd
);
718 return PTR_ERR(link
);
721 static void path_put_conditional(struct path
*path
, struct nameidata
*nd
)
724 if (path
->mnt
!= nd
->path
.mnt
)
728 static inline void path_to_nameidata(const struct path
*path
,
729 struct nameidata
*nd
)
731 if (!(nd
->flags
& LOOKUP_RCU
)) {
732 dput(nd
->path
.dentry
);
733 if (nd
->path
.mnt
!= path
->mnt
)
734 mntput(nd
->path
.mnt
);
736 nd
->path
.mnt
= path
->mnt
;
737 nd
->path
.dentry
= path
->dentry
;
740 static inline void put_link(struct nameidata
*nd
, struct path
*link
, void *cookie
)
742 struct inode
*inode
= link
->dentry
->d_inode
;
743 if (!IS_ERR(cookie
) && inode
->i_op
->put_link
)
744 inode
->i_op
->put_link(link
->dentry
, nd
, cookie
);
748 static __always_inline
int
749 follow_link(struct path
*link
, struct nameidata
*nd
, void **p
)
752 struct dentry
*dentry
= link
->dentry
;
754 BUG_ON(nd
->flags
& LOOKUP_RCU
);
756 if (unlikely(current
->total_link_count
>= 40)) {
757 *p
= ERR_PTR(-ELOOP
); /* no ->put_link(), please */
758 path_put_conditional(link
, nd
);
763 current
->total_link_count
++;
765 touch_atime(link
->mnt
, dentry
);
766 nd_set_link(nd
, NULL
);
768 if (link
->mnt
== nd
->path
.mnt
)
771 error
= security_inode_follow_link(link
->dentry
, nd
);
773 *p
= ERR_PTR(error
); /* no ->put_link(), please */
778 nd
->last_type
= LAST_BIND
;
779 *p
= dentry
->d_inode
->i_op
->follow_link(dentry
, nd
);
782 char *s
= nd_get_link(nd
);
785 error
= __vfs_follow_link(nd
, s
);
786 else if (nd
->last_type
== LAST_BIND
) {
787 nd
->flags
|= LOOKUP_JUMPED
;
788 nd
->inode
= nd
->path
.dentry
->d_inode
;
789 if (nd
->inode
->i_op
->follow_link
) {
790 /* stepped on a _really_ weird one */
799 static int follow_up_rcu(struct path
*path
)
801 struct vfsmount
*parent
;
802 struct dentry
*mountpoint
;
804 parent
= path
->mnt
->mnt_parent
;
805 if (parent
== path
->mnt
)
807 mountpoint
= path
->mnt
->mnt_mountpoint
;
808 path
->dentry
= mountpoint
;
813 int follow_up(struct path
*path
)
815 struct vfsmount
*parent
;
816 struct dentry
*mountpoint
;
818 br_read_lock(vfsmount_lock
);
819 parent
= path
->mnt
->mnt_parent
;
820 if (parent
== path
->mnt
) {
821 br_read_unlock(vfsmount_lock
);
825 mountpoint
= dget(path
->mnt
->mnt_mountpoint
);
826 br_read_unlock(vfsmount_lock
);
828 path
->dentry
= mountpoint
;
835 * Perform an automount
836 * - return -EISDIR to tell follow_managed() to stop and return the path we
839 static int follow_automount(struct path
*path
, unsigned flags
,
842 struct vfsmount
*mnt
;
845 if (!path
->dentry
->d_op
|| !path
->dentry
->d_op
->d_automount
)
848 /* We don't want to mount if someone supplied AT_NO_AUTOMOUNT
849 * and this is the terminal part of the path.
851 if ((flags
& LOOKUP_NO_AUTOMOUNT
) && !(flags
& LOOKUP_CONTINUE
))
852 return -EISDIR
; /* we actually want to stop here */
854 /* We want to mount if someone is trying to open/create a file of any
855 * type under the mountpoint, wants to traverse through the mountpoint
856 * or wants to open the mounted directory.
858 * We don't want to mount if someone's just doing a stat and they've
859 * set AT_SYMLINK_NOFOLLOW - unless they're stat'ing a directory and
860 * appended a '/' to the name.
862 if (!(flags
& LOOKUP_FOLLOW
) &&
863 !(flags
& (LOOKUP_CONTINUE
| LOOKUP_DIRECTORY
|
864 LOOKUP_OPEN
| LOOKUP_CREATE
)))
867 current
->total_link_count
++;
868 if (current
->total_link_count
>= 40)
871 mnt
= path
->dentry
->d_op
->d_automount(path
);
874 * The filesystem is allowed to return -EISDIR here to indicate
875 * it doesn't want to automount. For instance, autofs would do
876 * this so that its userspace daemon can mount on this dentry.
878 * However, we can only permit this if it's a terminal point in
879 * the path being looked up; if it wasn't then the remainder of
880 * the path is inaccessible and we should say so.
882 if (PTR_ERR(mnt
) == -EISDIR
&& (flags
& LOOKUP_CONTINUE
))
887 if (!mnt
) /* mount collision */
890 err
= finish_automount(mnt
, path
);
894 /* Someone else made a mount here whilst we were busy */
901 path
->dentry
= dget(mnt
->mnt_root
);
911 * Handle a dentry that is managed in some way.
912 * - Flagged for transit management (autofs)
913 * - Flagged as mountpoint
914 * - Flagged as automount point
916 * This may only be called in refwalk mode.
918 * Serialization is taken care of in namespace.c
920 static int follow_managed(struct path
*path
, unsigned flags
)
923 bool need_mntput
= false;
926 /* Given that we're not holding a lock here, we retain the value in a
927 * local variable for each dentry as we look at it so that we don't see
928 * the components of that value change under us */
929 while (managed
= ACCESS_ONCE(path
->dentry
->d_flags
),
930 managed
&= DCACHE_MANAGED_DENTRY
,
931 unlikely(managed
!= 0)) {
932 /* Allow the filesystem to manage the transit without i_mutex
934 if (managed
& DCACHE_MANAGE_TRANSIT
) {
935 BUG_ON(!path
->dentry
->d_op
);
936 BUG_ON(!path
->dentry
->d_op
->d_manage
);
937 ret
= path
->dentry
->d_op
->d_manage(path
->dentry
,
940 return ret
== -EISDIR
? 0 : ret
;
943 /* Transit to a mounted filesystem. */
944 if (managed
& DCACHE_MOUNTED
) {
945 struct vfsmount
*mounted
= lookup_mnt(path
);
951 path
->dentry
= dget(mounted
->mnt_root
);
956 /* Something is mounted on this dentry in another
957 * namespace and/or whatever was mounted there in this
958 * namespace got unmounted before we managed to get the
962 /* Handle an automount point */
963 if (managed
& DCACHE_NEED_AUTOMOUNT
) {
964 ret
= follow_automount(path
, flags
, &need_mntput
);
966 return ret
== -EISDIR
? 0 : ret
;
970 /* We didn't change the current path point */
976 int follow_down_one(struct path
*path
)
978 struct vfsmount
*mounted
;
980 mounted
= lookup_mnt(path
);
985 path
->dentry
= dget(mounted
->mnt_root
);
992 * Skip to top of mountpoint pile in rcuwalk mode. We abort the rcu-walk if we
993 * meet a managed dentry and we're not walking to "..". True is returned to
994 * continue, false to abort.
996 static bool __follow_mount_rcu(struct nameidata
*nd
, struct path
*path
,
997 struct inode
**inode
, bool reverse_transit
)
999 while (d_mountpoint(path
->dentry
)) {
1000 struct vfsmount
*mounted
;
1001 if (unlikely(path
->dentry
->d_flags
& DCACHE_MANAGE_TRANSIT
) &&
1003 path
->dentry
->d_op
->d_manage(path
->dentry
, false, true) < 0)
1005 mounted
= __lookup_mnt(path
->mnt
, path
->dentry
, 1);
1008 path
->mnt
= mounted
;
1009 path
->dentry
= mounted
->mnt_root
;
1010 nd
->seq
= read_seqcount_begin(&path
->dentry
->d_seq
);
1011 *inode
= path
->dentry
->d_inode
;
1014 if (unlikely(path
->dentry
->d_flags
& DCACHE_NEED_AUTOMOUNT
))
1015 return reverse_transit
;
1019 static int follow_dotdot_rcu(struct nameidata
*nd
)
1021 struct inode
*inode
= nd
->inode
;
1026 if (nd
->path
.dentry
== nd
->root
.dentry
&&
1027 nd
->path
.mnt
== nd
->root
.mnt
) {
1030 if (nd
->path
.dentry
!= nd
->path
.mnt
->mnt_root
) {
1031 struct dentry
*old
= nd
->path
.dentry
;
1032 struct dentry
*parent
= old
->d_parent
;
1035 seq
= read_seqcount_begin(&parent
->d_seq
);
1036 if (read_seqcount_retry(&old
->d_seq
, nd
->seq
))
1038 inode
= parent
->d_inode
;
1039 nd
->path
.dentry
= parent
;
1043 if (!follow_up_rcu(&nd
->path
))
1045 nd
->seq
= read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1046 inode
= nd
->path
.dentry
->d_inode
;
1048 __follow_mount_rcu(nd
, &nd
->path
, &inode
, true);
1053 nd
->flags
&= ~LOOKUP_RCU
;
1054 if (!(nd
->flags
& LOOKUP_ROOT
))
1055 nd
->root
.mnt
= NULL
;
1057 br_read_unlock(vfsmount_lock
);
1062 * Follow down to the covering mount currently visible to userspace. At each
1063 * point, the filesystem owning that dentry may be queried as to whether the
1064 * caller is permitted to proceed or not.
1066 * Care must be taken as namespace_sem may be held (indicated by mounting_here
1069 int follow_down(struct path
*path
, bool mounting_here
)
1074 while (managed
= ACCESS_ONCE(path
->dentry
->d_flags
),
1075 unlikely(managed
& DCACHE_MANAGED_DENTRY
)) {
1076 /* Allow the filesystem to manage the transit without i_mutex
1079 * We indicate to the filesystem if someone is trying to mount
1080 * something here. This gives autofs the chance to deny anyone
1081 * other than its daemon the right to mount on its
1084 * The filesystem may sleep at this point.
1086 if (managed
& DCACHE_MANAGE_TRANSIT
) {
1087 BUG_ON(!path
->dentry
->d_op
);
1088 BUG_ON(!path
->dentry
->d_op
->d_manage
);
1089 ret
= path
->dentry
->d_op
->d_manage(
1090 path
->dentry
, mounting_here
, false);
1092 return ret
== -EISDIR
? 0 : ret
;
1095 /* Transit to a mounted filesystem. */
1096 if (managed
& DCACHE_MOUNTED
) {
1097 struct vfsmount
*mounted
= lookup_mnt(path
);
1102 path
->mnt
= mounted
;
1103 path
->dentry
= dget(mounted
->mnt_root
);
1107 /* Don't handle automount points here */
1114 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1116 static void follow_mount(struct path
*path
)
1118 while (d_mountpoint(path
->dentry
)) {
1119 struct vfsmount
*mounted
= lookup_mnt(path
);
1124 path
->mnt
= mounted
;
1125 path
->dentry
= dget(mounted
->mnt_root
);
1129 static void follow_dotdot(struct nameidata
*nd
)
1134 struct dentry
*old
= nd
->path
.dentry
;
1136 if (nd
->path
.dentry
== nd
->root
.dentry
&&
1137 nd
->path
.mnt
== nd
->root
.mnt
) {
1140 if (nd
->path
.dentry
!= nd
->path
.mnt
->mnt_root
) {
1141 /* rare case of legitimate dget_parent()... */
1142 nd
->path
.dentry
= dget_parent(nd
->path
.dentry
);
1146 if (!follow_up(&nd
->path
))
1149 follow_mount(&nd
->path
);
1150 nd
->inode
= nd
->path
.dentry
->d_inode
;
1154 * Allocate a dentry with name and parent, and perform a parent
1155 * directory ->lookup on it. Returns the new dentry, or ERR_PTR
1156 * on error. parent->d_inode->i_mutex must be held. d_lookup must
1157 * have verified that no child exists while under i_mutex.
1159 static struct dentry
*d_alloc_and_lookup(struct dentry
*parent
,
1160 struct qstr
*name
, struct nameidata
*nd
)
1162 struct inode
*inode
= parent
->d_inode
;
1163 struct dentry
*dentry
;
1166 /* Don't create child dentry for a dead directory. */
1167 if (unlikely(IS_DEADDIR(inode
)))
1168 return ERR_PTR(-ENOENT
);
1170 dentry
= d_alloc(parent
, name
);
1171 if (unlikely(!dentry
))
1172 return ERR_PTR(-ENOMEM
);
1174 old
= inode
->i_op
->lookup(inode
, dentry
, nd
);
1175 if (unlikely(old
)) {
1183 * It's more convoluted than I'd like it to be, but... it's still fairly
1184 * small and for now I'd prefer to have fast path as straight as possible.
1185 * It _is_ time-critical.
1187 static int do_lookup(struct nameidata
*nd
, struct qstr
*name
,
1188 struct path
*path
, struct inode
**inode
)
1190 struct vfsmount
*mnt
= nd
->path
.mnt
;
1191 struct dentry
*dentry
, *parent
= nd
->path
.dentry
;
1197 * Rename seqlock is not required here because in the off chance
1198 * of a false negative due to a concurrent rename, we're going to
1199 * do the non-racy lookup, below.
1201 if (nd
->flags
& LOOKUP_RCU
) {
1204 dentry
= __d_lookup_rcu(parent
, name
, &seq
, inode
);
1208 /* Memory barrier in read_seqcount_begin of child is enough */
1209 if (__read_seqcount_retry(&parent
->d_seq
, nd
->seq
))
1213 if (unlikely(dentry
->d_flags
& DCACHE_OP_REVALIDATE
)) {
1214 status
= d_revalidate(dentry
, nd
);
1215 if (unlikely(status
<= 0)) {
1216 if (status
!= -ECHILD
)
1222 path
->dentry
= dentry
;
1223 if (likely(__follow_mount_rcu(nd
, path
, inode
, false)))
1227 if (nameidata_dentry_drop_rcu(nd
, dentry
))
1230 if (nameidata_drop_rcu(nd
))
1234 dentry
= __d_lookup(parent
, name
);
1238 if (unlikely(!dentry
)) {
1239 struct inode
*dir
= parent
->d_inode
;
1240 BUG_ON(nd
->inode
!= dir
);
1242 mutex_lock(&dir
->i_mutex
);
1243 dentry
= d_lookup(parent
, name
);
1244 if (likely(!dentry
)) {
1245 dentry
= d_alloc_and_lookup(parent
, name
, nd
);
1246 if (IS_ERR(dentry
)) {
1247 mutex_unlock(&dir
->i_mutex
);
1248 return PTR_ERR(dentry
);
1254 mutex_unlock(&dir
->i_mutex
);
1256 if (unlikely(dentry
->d_flags
& DCACHE_OP_REVALIDATE
) && need_reval
)
1257 status
= d_revalidate(dentry
, nd
);
1258 if (unlikely(status
<= 0)) {
1263 if (!d_invalidate(dentry
)) {
1272 path
->dentry
= dentry
;
1273 err
= follow_managed(path
, nd
->flags
);
1274 if (unlikely(err
< 0)) {
1275 path_put_conditional(path
, nd
);
1278 *inode
= path
->dentry
->d_inode
;
1282 static inline int may_lookup(struct nameidata
*nd
)
1284 if (nd
->flags
& LOOKUP_RCU
) {
1285 int err
= exec_permission(nd
->inode
, IPERM_FLAG_RCU
);
1288 if (nameidata_drop_rcu(nd
))
1291 return exec_permission(nd
->inode
, 0);
1294 static inline int handle_dots(struct nameidata
*nd
, int type
)
1296 if (type
== LAST_DOTDOT
) {
1297 if (nd
->flags
& LOOKUP_RCU
) {
1298 if (follow_dotdot_rcu(nd
))
1306 static void terminate_walk(struct nameidata
*nd
)
1308 if (!(nd
->flags
& LOOKUP_RCU
)) {
1309 path_put(&nd
->path
);
1311 nd
->flags
&= ~LOOKUP_RCU
;
1312 if (!(nd
->flags
& LOOKUP_ROOT
))
1313 nd
->root
.mnt
= NULL
;
1315 br_read_unlock(vfsmount_lock
);
1319 static inline int walk_component(struct nameidata
*nd
, struct path
*path
,
1320 struct qstr
*name
, int type
, int follow
)
1322 struct inode
*inode
;
1325 * "." and ".." are special - ".." especially so because it has
1326 * to be able to know about the current root directory and
1327 * parent relationships.
1329 if (unlikely(type
!= LAST_NORM
))
1330 return handle_dots(nd
, type
);
1331 err
= do_lookup(nd
, name
, path
, &inode
);
1332 if (unlikely(err
)) {
1337 path_to_nameidata(path
, nd
);
1341 if (unlikely(inode
->i_op
->follow_link
) && follow
) {
1342 if (nameidata_dentry_drop_rcu_maybe(nd
, path
->dentry
))
1344 BUG_ON(inode
!= path
->dentry
->d_inode
);
1347 path_to_nameidata(path
, nd
);
1353 * This limits recursive symlink follows to 8, while
1354 * limiting consecutive symlinks to 40.
1356 * Without that kind of total limit, nasty chains of consecutive
1357 * symlinks can cause almost arbitrarily long lookups.
1359 static inline int nested_symlink(struct path
*path
, struct nameidata
*nd
)
1363 BUG_ON(nd
->depth
>= MAX_NESTED_LINKS
);
1364 if (unlikely(current
->link_count
>= MAX_NESTED_LINKS
)) {
1365 path_put_conditional(path
, nd
);
1366 path_put(&nd
->path
);
1371 current
->link_count
++;
1374 struct path link
= *path
;
1377 res
= follow_link(&link
, nd
, &cookie
);
1379 res
= walk_component(nd
, path
, &nd
->last
,
1380 nd
->last_type
, LOOKUP_FOLLOW
);
1381 put_link(nd
, &link
, cookie
);
1384 current
->link_count
--;
1391 * This is the basic name resolution function, turning a pathname into
1392 * the final dentry. We expect 'base' to be positive and a directory.
1394 * Returns 0 and nd will have valid dentry and mnt on success.
1395 * Returns error and drops reference to input namei data on failure.
1397 static int link_path_walk(const char *name
, struct nameidata
*nd
)
1401 unsigned int lookup_flags
= nd
->flags
;
1408 /* At this point we know we have a real path component. */
1415 nd
->flags
|= LOOKUP_CONTINUE
;
1417 err
= may_lookup(nd
);
1422 c
= *(const unsigned char *)name
;
1424 hash
= init_name_hash();
1427 hash
= partial_name_hash(c
, hash
);
1428 c
= *(const unsigned char *)name
;
1429 } while (c
&& (c
!= '/'));
1430 this.len
= name
- (const char *) this.name
;
1431 this.hash
= end_name_hash(hash
);
1434 if (this.name
[0] == '.') switch (this.len
) {
1436 if (this.name
[1] == '.') {
1438 nd
->flags
|= LOOKUP_JUMPED
;
1444 if (likely(type
== LAST_NORM
)) {
1445 struct dentry
*parent
= nd
->path
.dentry
;
1446 nd
->flags
&= ~LOOKUP_JUMPED
;
1447 if (unlikely(parent
->d_flags
& DCACHE_OP_HASH
)) {
1448 err
= parent
->d_op
->d_hash(parent
, nd
->inode
,
1455 /* remove trailing slashes? */
1457 goto last_component
;
1458 while (*++name
== '/');
1460 goto last_component
;
1462 err
= walk_component(nd
, &next
, &this, type
, LOOKUP_FOLLOW
);
1467 err
= nested_symlink(&next
, nd
);
1472 if (!nd
->inode
->i_op
->lookup
)
1475 /* here ends the main loop */
1478 /* Clear LOOKUP_CONTINUE iff it was previously unset */
1479 nd
->flags
&= lookup_flags
| ~LOOKUP_CONTINUE
;
1481 nd
->last_type
= type
;
1488 static int path_init(int dfd
, const char *name
, unsigned int flags
,
1489 struct nameidata
*nd
, struct file
**fp
)
1495 nd
->last_type
= LAST_ROOT
; /* if there are only slashes... */
1496 nd
->flags
= flags
| LOOKUP_JUMPED
;
1498 if (flags
& LOOKUP_ROOT
) {
1499 struct inode
*inode
= nd
->root
.dentry
->d_inode
;
1501 if (!inode
->i_op
->lookup
)
1503 retval
= inode_permission(inode
, MAY_EXEC
);
1507 nd
->path
= nd
->root
;
1509 if (flags
& LOOKUP_RCU
) {
1510 br_read_lock(vfsmount_lock
);
1512 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1514 path_get(&nd
->path
);
1519 nd
->root
.mnt
= NULL
;
1522 if (flags
& LOOKUP_RCU
) {
1523 br_read_lock(vfsmount_lock
);
1528 path_get(&nd
->root
);
1530 nd
->path
= nd
->root
;
1531 } else if (dfd
== AT_FDCWD
) {
1532 if (flags
& LOOKUP_RCU
) {
1533 struct fs_struct
*fs
= current
->fs
;
1536 br_read_lock(vfsmount_lock
);
1540 seq
= read_seqcount_begin(&fs
->seq
);
1542 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1543 } while (read_seqcount_retry(&fs
->seq
, seq
));
1545 get_fs_pwd(current
->fs
, &nd
->path
);
1548 struct dentry
*dentry
;
1550 file
= fget_raw_light(dfd
, &fput_needed
);
1555 dentry
= file
->f_path
.dentry
;
1559 if (!S_ISDIR(dentry
->d_inode
->i_mode
))
1562 retval
= file_permission(file
, MAY_EXEC
);
1567 nd
->path
= file
->f_path
;
1568 if (flags
& LOOKUP_RCU
) {
1571 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1572 br_read_lock(vfsmount_lock
);
1575 path_get(&file
->f_path
);
1576 fput_light(file
, fput_needed
);
1580 nd
->inode
= nd
->path
.dentry
->d_inode
;
1584 fput_light(file
, fput_needed
);
1589 static inline int lookup_last(struct nameidata
*nd
, struct path
*path
)
1591 if (nd
->last_type
== LAST_NORM
&& nd
->last
.name
[nd
->last
.len
])
1592 nd
->flags
|= LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
;
1594 nd
->flags
&= ~LOOKUP_PARENT
;
1595 return walk_component(nd
, path
, &nd
->last
, nd
->last_type
,
1596 nd
->flags
& LOOKUP_FOLLOW
);
1599 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
1600 static int path_lookupat(int dfd
, const char *name
,
1601 unsigned int flags
, struct nameidata
*nd
)
1603 struct file
*base
= NULL
;
1608 * Path walking is largely split up into 2 different synchronisation
1609 * schemes, rcu-walk and ref-walk (explained in
1610 * Documentation/filesystems/path-lookup.txt). These share much of the
1611 * path walk code, but some things particularly setup, cleanup, and
1612 * following mounts are sufficiently divergent that functions are
1613 * duplicated. Typically there is a function foo(), and its RCU
1614 * analogue, foo_rcu().
1616 * -ECHILD is the error number of choice (just to avoid clashes) that
1617 * is returned if some aspect of an rcu-walk fails. Such an error must
1618 * be handled by restarting a traditional ref-walk (which will always
1619 * be able to complete).
1621 err
= path_init(dfd
, name
, flags
| LOOKUP_PARENT
, nd
, &base
);
1626 current
->total_link_count
= 0;
1627 err
= link_path_walk(name
, nd
);
1629 if (!err
&& !(flags
& LOOKUP_PARENT
)) {
1630 err
= lookup_last(nd
, &path
);
1633 struct path link
= path
;
1634 nd
->flags
|= LOOKUP_PARENT
;
1635 err
= follow_link(&link
, nd
, &cookie
);
1637 err
= lookup_last(nd
, &path
);
1638 put_link(nd
, &link
, cookie
);
1642 if (nd
->flags
& LOOKUP_RCU
) {
1643 /* went all way through without dropping RCU */
1645 if (nameidata_drop_rcu_last(nd
))
1650 err
= handle_reval_path(nd
);
1652 if (!err
&& nd
->flags
& LOOKUP_DIRECTORY
) {
1653 if (!nd
->inode
->i_op
->lookup
) {
1654 path_put(&nd
->path
);
1662 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
)) {
1663 path_put(&nd
->root
);
1664 nd
->root
.mnt
= NULL
;
1669 static int do_path_lookup(int dfd
, const char *name
,
1670 unsigned int flags
, struct nameidata
*nd
)
1672 int retval
= path_lookupat(dfd
, name
, flags
| LOOKUP_RCU
, nd
);
1673 if (unlikely(retval
== -ECHILD
))
1674 retval
= path_lookupat(dfd
, name
, flags
, nd
);
1675 if (unlikely(retval
== -ESTALE
))
1676 retval
= path_lookupat(dfd
, name
, flags
| LOOKUP_REVAL
, nd
);
1678 if (likely(!retval
)) {
1679 if (unlikely(!audit_dummy_context())) {
1680 if (nd
->path
.dentry
&& nd
->inode
)
1681 audit_inode(name
, nd
->path
.dentry
);
1687 int kern_path_parent(const char *name
, struct nameidata
*nd
)
1689 return do_path_lookup(AT_FDCWD
, name
, LOOKUP_PARENT
, nd
);
1692 int kern_path(const char *name
, unsigned int flags
, struct path
*path
)
1694 struct nameidata nd
;
1695 int res
= do_path_lookup(AT_FDCWD
, name
, flags
, &nd
);
1702 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
1703 * @dentry: pointer to dentry of the base directory
1704 * @mnt: pointer to vfs mount of the base directory
1705 * @name: pointer to file name
1706 * @flags: lookup flags
1707 * @nd: pointer to nameidata
1709 int vfs_path_lookup(struct dentry
*dentry
, struct vfsmount
*mnt
,
1710 const char *name
, unsigned int flags
,
1711 struct nameidata
*nd
)
1713 nd
->root
.dentry
= dentry
;
1715 /* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */
1716 return do_path_lookup(AT_FDCWD
, name
, flags
| LOOKUP_ROOT
, nd
);
1719 static struct dentry
*__lookup_hash(struct qstr
*name
,
1720 struct dentry
*base
, struct nameidata
*nd
)
1722 struct inode
*inode
= base
->d_inode
;
1723 struct dentry
*dentry
;
1726 err
= exec_permission(inode
, 0);
1728 return ERR_PTR(err
);
1731 * Don't bother with __d_lookup: callers are for creat as
1732 * well as unlink, so a lot of the time it would cost
1735 dentry
= d_lookup(base
, name
);
1737 if (dentry
&& (dentry
->d_flags
& DCACHE_OP_REVALIDATE
))
1738 dentry
= do_revalidate(dentry
, nd
);
1741 dentry
= d_alloc_and_lookup(base
, name
, nd
);
1747 * Restricted form of lookup. Doesn't follow links, single-component only,
1748 * needs parent already locked. Doesn't follow mounts.
1751 static struct dentry
*lookup_hash(struct nameidata
*nd
)
1753 return __lookup_hash(&nd
->last
, nd
->path
.dentry
, nd
);
1757 * lookup_one_len - filesystem helper to lookup single pathname component
1758 * @name: pathname component to lookup
1759 * @base: base directory to lookup from
1760 * @len: maximum length @len should be interpreted to
1762 * Note that this routine is purely a helper for filesystem usage and should
1763 * not be called by generic code. Also note that by using this function the
1764 * nameidata argument is passed to the filesystem methods and a filesystem
1765 * using this helper needs to be prepared for that.
1767 struct dentry
*lookup_one_len(const char *name
, struct dentry
*base
, int len
)
1773 WARN_ON_ONCE(!mutex_is_locked(&base
->d_inode
->i_mutex
));
1778 return ERR_PTR(-EACCES
);
1780 hash
= init_name_hash();
1782 c
= *(const unsigned char *)name
++;
1783 if (c
== '/' || c
== '\0')
1784 return ERR_PTR(-EACCES
);
1785 hash
= partial_name_hash(c
, hash
);
1787 this.hash
= end_name_hash(hash
);
1789 * See if the low-level filesystem might want
1790 * to use its own hash..
1792 if (base
->d_flags
& DCACHE_OP_HASH
) {
1793 int err
= base
->d_op
->d_hash(base
, base
->d_inode
, &this);
1795 return ERR_PTR(err
);
1798 return __lookup_hash(&this, base
, NULL
);
1801 int user_path_at(int dfd
, const char __user
*name
, unsigned flags
,
1804 struct nameidata nd
;
1805 char *tmp
= getname_flags(name
, flags
);
1806 int err
= PTR_ERR(tmp
);
1809 BUG_ON(flags
& LOOKUP_PARENT
);
1811 err
= do_path_lookup(dfd
, tmp
, flags
, &nd
);
1819 static int user_path_parent(int dfd
, const char __user
*path
,
1820 struct nameidata
*nd
, char **name
)
1822 char *s
= getname(path
);
1828 error
= do_path_lookup(dfd
, s
, LOOKUP_PARENT
, nd
);
1838 * It's inline, so penalty for filesystems that don't use sticky bit is
1841 static inline int check_sticky(struct inode
*dir
, struct inode
*inode
)
1843 uid_t fsuid
= current_fsuid();
1845 if (!(dir
->i_mode
& S_ISVTX
))
1847 if (inode
->i_uid
== fsuid
)
1849 if (dir
->i_uid
== fsuid
)
1851 return !capable(CAP_FOWNER
);
1855 * Check whether we can remove a link victim from directory dir, check
1856 * whether the type of victim is right.
1857 * 1. We can't do it if dir is read-only (done in permission())
1858 * 2. We should have write and exec permissions on dir
1859 * 3. We can't remove anything from append-only dir
1860 * 4. We can't do anything with immutable dir (done in permission())
1861 * 5. If the sticky bit on dir is set we should either
1862 * a. be owner of dir, or
1863 * b. be owner of victim, or
1864 * c. have CAP_FOWNER capability
1865 * 6. If the victim is append-only or immutable we can't do antyhing with
1866 * links pointing to it.
1867 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
1868 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
1869 * 9. We can't remove a root or mountpoint.
1870 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
1871 * nfs_async_unlink().
1873 static int may_delete(struct inode
*dir
,struct dentry
*victim
,int isdir
)
1877 if (!victim
->d_inode
)
1880 BUG_ON(victim
->d_parent
->d_inode
!= dir
);
1881 audit_inode_child(victim
, dir
);
1883 error
= inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
1888 if (check_sticky(dir
, victim
->d_inode
)||IS_APPEND(victim
->d_inode
)||
1889 IS_IMMUTABLE(victim
->d_inode
) || IS_SWAPFILE(victim
->d_inode
))
1892 if (!S_ISDIR(victim
->d_inode
->i_mode
))
1894 if (IS_ROOT(victim
))
1896 } else if (S_ISDIR(victim
->d_inode
->i_mode
))
1898 if (IS_DEADDIR(dir
))
1900 if (victim
->d_flags
& DCACHE_NFSFS_RENAMED
)
1905 /* Check whether we can create an object with dentry child in directory
1907 * 1. We can't do it if child already exists (open has special treatment for
1908 * this case, but since we are inlined it's OK)
1909 * 2. We can't do it if dir is read-only (done in permission())
1910 * 3. We should have write and exec permissions on dir
1911 * 4. We can't do it if dir is immutable (done in permission())
1913 static inline int may_create(struct inode
*dir
, struct dentry
*child
)
1917 if (IS_DEADDIR(dir
))
1919 return inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
1923 * p1 and p2 should be directories on the same fs.
1925 struct dentry
*lock_rename(struct dentry
*p1
, struct dentry
*p2
)
1930 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
1934 mutex_lock(&p1
->d_inode
->i_sb
->s_vfs_rename_mutex
);
1936 p
= d_ancestor(p2
, p1
);
1938 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
1939 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_CHILD
);
1943 p
= d_ancestor(p1
, p2
);
1945 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
1946 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_CHILD
);
1950 mutex_lock_nested(&p1
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
1951 mutex_lock_nested(&p2
->d_inode
->i_mutex
, I_MUTEX_CHILD
);
1955 void unlock_rename(struct dentry
*p1
, struct dentry
*p2
)
1957 mutex_unlock(&p1
->d_inode
->i_mutex
);
1959 mutex_unlock(&p2
->d_inode
->i_mutex
);
1960 mutex_unlock(&p1
->d_inode
->i_sb
->s_vfs_rename_mutex
);
1964 int vfs_create(struct inode
*dir
, struct dentry
*dentry
, int mode
,
1965 struct nameidata
*nd
)
1967 int error
= may_create(dir
, dentry
);
1972 if (!dir
->i_op
->create
)
1973 return -EACCES
; /* shouldn't it be ENOSYS? */
1976 error
= security_inode_create(dir
, dentry
, mode
);
1979 error
= dir
->i_op
->create(dir
, dentry
, mode
, nd
);
1981 fsnotify_create(dir
, dentry
);
1985 static int may_open(struct path
*path
, int acc_mode
, int flag
)
1987 struct dentry
*dentry
= path
->dentry
;
1988 struct inode
*inode
= dentry
->d_inode
;
1998 switch (inode
->i_mode
& S_IFMT
) {
2002 if (acc_mode
& MAY_WRITE
)
2007 if (path
->mnt
->mnt_flags
& MNT_NODEV
)
2016 error
= inode_permission(inode
, acc_mode
);
2021 * An append-only file must be opened in append mode for writing.
2023 if (IS_APPEND(inode
)) {
2024 if ((flag
& O_ACCMODE
) != O_RDONLY
&& !(flag
& O_APPEND
))
2030 /* O_NOATIME can only be set by the owner or superuser */
2031 if (flag
& O_NOATIME
&& !is_owner_or_cap(inode
))
2035 * Ensure there are no outstanding leases on the file.
2037 return break_lease(inode
, flag
);
2040 static int handle_truncate(struct file
*filp
)
2042 struct path
*path
= &filp
->f_path
;
2043 struct inode
*inode
= path
->dentry
->d_inode
;
2044 int error
= get_write_access(inode
);
2048 * Refuse to truncate files with mandatory locks held on them.
2050 error
= locks_verify_locked(inode
);
2052 error
= security_path_truncate(path
);
2054 error
= do_truncate(path
->dentry
, 0,
2055 ATTR_MTIME
|ATTR_CTIME
|ATTR_OPEN
,
2058 put_write_access(inode
);
2063 * Note that while the flag value (low two bits) for sys_open means:
2068 * it is changed into
2069 * 00 - no permissions needed
2070 * 01 - read-permission
2071 * 10 - write-permission
2073 * for the internal routines (ie open_namei()/follow_link() etc)
2074 * This is more logical, and also allows the 00 "no perm needed"
2075 * to be used for symlinks (where the permissions are checked
2079 static inline int open_to_namei_flags(int flag
)
2081 if ((flag
+1) & O_ACCMODE
)
2087 * Handle the last step of open()
2089 static struct file
*do_last(struct nameidata
*nd
, struct path
*path
,
2090 const struct open_flags
*op
, const char *pathname
)
2092 struct dentry
*dir
= nd
->path
.dentry
;
2093 struct dentry
*dentry
;
2094 int open_flag
= op
->open_flag
;
2095 int will_truncate
= open_flag
& O_TRUNC
;
2097 int acc_mode
= op
->acc_mode
;
2101 nd
->flags
&= ~LOOKUP_PARENT
;
2102 nd
->flags
|= op
->intent
;
2104 switch (nd
->last_type
) {
2107 error
= handle_dots(nd
, nd
->last_type
);
2109 return ERR_PTR(error
);
2112 if (nd
->flags
& LOOKUP_RCU
) {
2113 if (nameidata_drop_rcu_last(nd
))
2114 return ERR_PTR(-ECHILD
);
2116 error
= handle_reval_path(nd
);
2119 audit_inode(pathname
, nd
->path
.dentry
);
2120 if (open_flag
& O_CREAT
) {
2126 /* can't be RCU mode here */
2127 error
= handle_reval_path(nd
);
2130 audit_inode(pathname
, dir
);
2134 if (!(open_flag
& O_CREAT
)) {
2136 if (nd
->last
.name
[nd
->last
.len
])
2137 nd
->flags
|= LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
;
2138 if (open_flag
& O_PATH
&& !(nd
->flags
& LOOKUP_FOLLOW
))
2140 /* we _can_ be in RCU mode here */
2141 error
= walk_component(nd
, path
, &nd
->last
, LAST_NORM
,
2144 return ERR_PTR(error
);
2145 if (error
) /* symlink */
2148 if (nd
->flags
& LOOKUP_RCU
) {
2149 if (nameidata_drop_rcu_last(nd
))
2150 return ERR_PTR(-ECHILD
);
2154 if (nd
->flags
& LOOKUP_DIRECTORY
) {
2155 if (!nd
->inode
->i_op
->lookup
)
2158 audit_inode(pathname
, nd
->path
.dentry
);
2162 /* create side of things */
2164 if (nd
->flags
& LOOKUP_RCU
) {
2165 if (nameidata_drop_rcu_last(nd
))
2166 return ERR_PTR(-ECHILD
);
2169 audit_inode(pathname
, dir
);
2171 /* trailing slashes? */
2172 if (nd
->last
.name
[nd
->last
.len
])
2175 mutex_lock(&dir
->d_inode
->i_mutex
);
2177 dentry
= lookup_hash(nd
);
2178 error
= PTR_ERR(dentry
);
2179 if (IS_ERR(dentry
)) {
2180 mutex_unlock(&dir
->d_inode
->i_mutex
);
2184 path
->dentry
= dentry
;
2185 path
->mnt
= nd
->path
.mnt
;
2187 /* Negative dentry, just create the file */
2188 if (!dentry
->d_inode
) {
2189 int mode
= op
->mode
;
2190 if (!IS_POSIXACL(dir
->d_inode
))
2191 mode
&= ~current_umask();
2193 * This write is needed to ensure that a
2194 * rw->ro transition does not occur between
2195 * the time when the file is created and when
2196 * a permanent write count is taken through
2197 * the 'struct file' in nameidata_to_filp().
2199 error
= mnt_want_write(nd
->path
.mnt
);
2201 goto exit_mutex_unlock
;
2203 /* Don't check for write permission, don't truncate */
2204 open_flag
&= ~O_TRUNC
;
2206 acc_mode
= MAY_OPEN
;
2207 error
= security_path_mknod(&nd
->path
, dentry
, mode
, 0);
2209 goto exit_mutex_unlock
;
2210 error
= vfs_create(dir
->d_inode
, dentry
, mode
, nd
);
2212 goto exit_mutex_unlock
;
2213 mutex_unlock(&dir
->d_inode
->i_mutex
);
2214 dput(nd
->path
.dentry
);
2215 nd
->path
.dentry
= dentry
;
2220 * It already exists.
2222 mutex_unlock(&dir
->d_inode
->i_mutex
);
2223 audit_inode(pathname
, path
->dentry
);
2226 if (open_flag
& O_EXCL
)
2229 error
= follow_managed(path
, nd
->flags
);
2234 if (!path
->dentry
->d_inode
)
2237 if (path
->dentry
->d_inode
->i_op
->follow_link
)
2240 path_to_nameidata(path
, nd
);
2241 nd
->inode
= path
->dentry
->d_inode
;
2243 if (S_ISDIR(nd
->inode
->i_mode
))
2246 if (!S_ISREG(nd
->inode
->i_mode
))
2249 if (will_truncate
) {
2250 error
= mnt_want_write(nd
->path
.mnt
);
2256 error
= may_open(&nd
->path
, acc_mode
, open_flag
);
2259 filp
= nameidata_to_filp(nd
);
2260 if (!IS_ERR(filp
)) {
2261 error
= ima_file_check(filp
, op
->acc_mode
);
2264 filp
= ERR_PTR(error
);
2267 if (!IS_ERR(filp
)) {
2268 if (will_truncate
) {
2269 error
= handle_truncate(filp
);
2272 filp
= ERR_PTR(error
);
2278 mnt_drop_write(nd
->path
.mnt
);
2279 path_put(&nd
->path
);
2283 mutex_unlock(&dir
->d_inode
->i_mutex
);
2285 path_put_conditional(path
, nd
);
2287 filp
= ERR_PTR(error
);
2291 static struct file
*path_openat(int dfd
, const char *pathname
,
2292 struct nameidata
*nd
, const struct open_flags
*op
, int flags
)
2294 struct file
*base
= NULL
;
2299 filp
= get_empty_filp();
2301 return ERR_PTR(-ENFILE
);
2303 filp
->f_flags
= op
->open_flag
;
2304 nd
->intent
.open
.file
= filp
;
2305 nd
->intent
.open
.flags
= open_to_namei_flags(op
->open_flag
);
2306 nd
->intent
.open
.create_mode
= op
->mode
;
2308 error
= path_init(dfd
, pathname
, flags
| LOOKUP_PARENT
, nd
, &base
);
2309 if (unlikely(error
))
2312 current
->total_link_count
= 0;
2313 error
= link_path_walk(pathname
, nd
);
2314 if (unlikely(error
))
2317 filp
= do_last(nd
, &path
, op
, pathname
);
2318 while (unlikely(!filp
)) { /* trailing symlink */
2319 struct path link
= path
;
2321 if (!(nd
->flags
& LOOKUP_FOLLOW
)) {
2322 path_put_conditional(&path
, nd
);
2323 path_put(&nd
->path
);
2324 filp
= ERR_PTR(-ELOOP
);
2327 nd
->flags
|= LOOKUP_PARENT
;
2328 nd
->flags
&= ~(LOOKUP_OPEN
|LOOKUP_CREATE
|LOOKUP_EXCL
);
2329 error
= follow_link(&link
, nd
, &cookie
);
2330 if (unlikely(error
))
2331 filp
= ERR_PTR(error
);
2333 filp
= do_last(nd
, &path
, op
, pathname
);
2334 put_link(nd
, &link
, cookie
);
2337 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
))
2338 path_put(&nd
->root
);
2341 release_open_intent(nd
);
2345 filp
= ERR_PTR(error
);
2349 struct file
*do_filp_open(int dfd
, const char *pathname
,
2350 const struct open_flags
*op
, int flags
)
2352 struct nameidata nd
;
2355 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
| LOOKUP_RCU
);
2356 if (unlikely(filp
== ERR_PTR(-ECHILD
)))
2357 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
);
2358 if (unlikely(filp
== ERR_PTR(-ESTALE
)))
2359 filp
= path_openat(dfd
, pathname
, &nd
, op
, flags
| LOOKUP_REVAL
);
2363 struct file
*do_file_open_root(struct dentry
*dentry
, struct vfsmount
*mnt
,
2364 const char *name
, const struct open_flags
*op
, int flags
)
2366 struct nameidata nd
;
2370 nd
.root
.dentry
= dentry
;
2372 flags
|= LOOKUP_ROOT
;
2374 if (dentry
->d_inode
->i_op
->follow_link
&& op
->intent
& LOOKUP_OPEN
)
2375 return ERR_PTR(-ELOOP
);
2377 file
= path_openat(-1, name
, &nd
, op
, flags
| LOOKUP_RCU
);
2378 if (unlikely(file
== ERR_PTR(-ECHILD
)))
2379 file
= path_openat(-1, name
, &nd
, op
, flags
);
2380 if (unlikely(file
== ERR_PTR(-ESTALE
)))
2381 file
= path_openat(-1, name
, &nd
, op
, flags
| LOOKUP_REVAL
);
2386 * lookup_create - lookup a dentry, creating it if it doesn't exist
2387 * @nd: nameidata info
2388 * @is_dir: directory flag
2390 * Simple function to lookup and return a dentry and create it
2391 * if it doesn't exist. Is SMP-safe.
2393 * Returns with nd->path.dentry->d_inode->i_mutex locked.
2395 struct dentry
*lookup_create(struct nameidata
*nd
, int is_dir
)
2397 struct dentry
*dentry
= ERR_PTR(-EEXIST
);
2399 mutex_lock_nested(&nd
->path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2401 * Yucky last component or no last component at all?
2402 * (foo/., foo/.., /////)
2404 if (nd
->last_type
!= LAST_NORM
)
2406 nd
->flags
&= ~LOOKUP_PARENT
;
2407 nd
->flags
|= LOOKUP_CREATE
| LOOKUP_EXCL
;
2408 nd
->intent
.open
.flags
= O_EXCL
;
2411 * Do the final lookup.
2413 dentry
= lookup_hash(nd
);
2417 if (dentry
->d_inode
)
2420 * Special case - lookup gave negative, but... we had foo/bar/
2421 * From the vfs_mknod() POV we just have a negative dentry -
2422 * all is fine. Let's be bastards - you had / on the end, you've
2423 * been asking for (non-existent) directory. -ENOENT for you.
2425 if (unlikely(!is_dir
&& nd
->last
.name
[nd
->last
.len
])) {
2427 dentry
= ERR_PTR(-ENOENT
);
2432 dentry
= ERR_PTR(-EEXIST
);
2436 EXPORT_SYMBOL_GPL(lookup_create
);
2438 int vfs_mknod(struct inode
*dir
, struct dentry
*dentry
, int mode
, dev_t dev
)
2440 int error
= may_create(dir
, dentry
);
2445 if ((S_ISCHR(mode
) || S_ISBLK(mode
)) && !capable(CAP_MKNOD
))
2448 if (!dir
->i_op
->mknod
)
2451 error
= devcgroup_inode_mknod(mode
, dev
);
2455 error
= security_inode_mknod(dir
, dentry
, mode
, dev
);
2459 error
= dir
->i_op
->mknod(dir
, dentry
, mode
, dev
);
2461 fsnotify_create(dir
, dentry
);
2465 static int may_mknod(mode_t mode
)
2467 switch (mode
& S_IFMT
) {
2473 case 0: /* zero mode translates to S_IFREG */
2482 SYSCALL_DEFINE4(mknodat
, int, dfd
, const char __user
*, filename
, int, mode
,
2487 struct dentry
*dentry
;
2488 struct nameidata nd
;
2493 error
= user_path_parent(dfd
, filename
, &nd
, &tmp
);
2497 dentry
= lookup_create(&nd
, 0);
2498 if (IS_ERR(dentry
)) {
2499 error
= PTR_ERR(dentry
);
2502 if (!IS_POSIXACL(nd
.path
.dentry
->d_inode
))
2503 mode
&= ~current_umask();
2504 error
= may_mknod(mode
);
2507 error
= mnt_want_write(nd
.path
.mnt
);
2510 error
= security_path_mknod(&nd
.path
, dentry
, mode
, dev
);
2512 goto out_drop_write
;
2513 switch (mode
& S_IFMT
) {
2514 case 0: case S_IFREG
:
2515 error
= vfs_create(nd
.path
.dentry
->d_inode
,dentry
,mode
,&nd
);
2517 case S_IFCHR
: case S_IFBLK
:
2518 error
= vfs_mknod(nd
.path
.dentry
->d_inode
,dentry
,mode
,
2519 new_decode_dev(dev
));
2521 case S_IFIFO
: case S_IFSOCK
:
2522 error
= vfs_mknod(nd
.path
.dentry
->d_inode
,dentry
,mode
,0);
2526 mnt_drop_write(nd
.path
.mnt
);
2530 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
2537 SYSCALL_DEFINE3(mknod
, const char __user
*, filename
, int, mode
, unsigned, dev
)
2539 return sys_mknodat(AT_FDCWD
, filename
, mode
, dev
);
2542 int vfs_mkdir(struct inode
*dir
, struct dentry
*dentry
, int mode
)
2544 int error
= may_create(dir
, dentry
);
2549 if (!dir
->i_op
->mkdir
)
2552 mode
&= (S_IRWXUGO
|S_ISVTX
);
2553 error
= security_inode_mkdir(dir
, dentry
, mode
);
2557 error
= dir
->i_op
->mkdir(dir
, dentry
, mode
);
2559 fsnotify_mkdir(dir
, dentry
);
2563 SYSCALL_DEFINE3(mkdirat
, int, dfd
, const char __user
*, pathname
, int, mode
)
2567 struct dentry
*dentry
;
2568 struct nameidata nd
;
2570 error
= user_path_parent(dfd
, pathname
, &nd
, &tmp
);
2574 dentry
= lookup_create(&nd
, 1);
2575 error
= PTR_ERR(dentry
);
2579 if (!IS_POSIXACL(nd
.path
.dentry
->d_inode
))
2580 mode
&= ~current_umask();
2581 error
= mnt_want_write(nd
.path
.mnt
);
2584 error
= security_path_mkdir(&nd
.path
, dentry
, mode
);
2586 goto out_drop_write
;
2587 error
= vfs_mkdir(nd
.path
.dentry
->d_inode
, dentry
, mode
);
2589 mnt_drop_write(nd
.path
.mnt
);
2593 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
2600 SYSCALL_DEFINE2(mkdir
, const char __user
*, pathname
, int, mode
)
2602 return sys_mkdirat(AT_FDCWD
, pathname
, mode
);
2606 * We try to drop the dentry early: we should have
2607 * a usage count of 2 if we're the only user of this
2608 * dentry, and if that is true (possibly after pruning
2609 * the dcache), then we drop the dentry now.
2611 * A low-level filesystem can, if it choses, legally
2614 * if (!d_unhashed(dentry))
2617 * if it cannot handle the case of removing a directory
2618 * that is still in use by something else..
2620 void dentry_unhash(struct dentry
*dentry
)
2623 shrink_dcache_parent(dentry
);
2624 spin_lock(&dentry
->d_lock
);
2625 if (dentry
->d_count
== 2)
2627 spin_unlock(&dentry
->d_lock
);
2630 int vfs_rmdir(struct inode
*dir
, struct dentry
*dentry
)
2632 int error
= may_delete(dir
, dentry
, 1);
2637 if (!dir
->i_op
->rmdir
)
2640 mutex_lock(&dentry
->d_inode
->i_mutex
);
2641 dentry_unhash(dentry
);
2642 if (d_mountpoint(dentry
))
2645 error
= security_inode_rmdir(dir
, dentry
);
2647 error
= dir
->i_op
->rmdir(dir
, dentry
);
2649 dentry
->d_inode
->i_flags
|= S_DEAD
;
2654 mutex_unlock(&dentry
->d_inode
->i_mutex
);
2663 static long do_rmdir(int dfd
, const char __user
*pathname
)
2667 struct dentry
*dentry
;
2668 struct nameidata nd
;
2670 error
= user_path_parent(dfd
, pathname
, &nd
, &name
);
2674 switch(nd
.last_type
) {
2686 nd
.flags
&= ~LOOKUP_PARENT
;
2688 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2689 dentry
= lookup_hash(&nd
);
2690 error
= PTR_ERR(dentry
);
2693 error
= mnt_want_write(nd
.path
.mnt
);
2696 error
= security_path_rmdir(&nd
.path
, dentry
);
2699 error
= vfs_rmdir(nd
.path
.dentry
->d_inode
, dentry
);
2701 mnt_drop_write(nd
.path
.mnt
);
2705 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
2712 SYSCALL_DEFINE1(rmdir
, const char __user
*, pathname
)
2714 return do_rmdir(AT_FDCWD
, pathname
);
2717 int vfs_unlink(struct inode
*dir
, struct dentry
*dentry
)
2719 int error
= may_delete(dir
, dentry
, 0);
2724 if (!dir
->i_op
->unlink
)
2727 mutex_lock(&dentry
->d_inode
->i_mutex
);
2728 if (d_mountpoint(dentry
))
2731 error
= security_inode_unlink(dir
, dentry
);
2733 error
= dir
->i_op
->unlink(dir
, dentry
);
2738 mutex_unlock(&dentry
->d_inode
->i_mutex
);
2740 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
2741 if (!error
&& !(dentry
->d_flags
& DCACHE_NFSFS_RENAMED
)) {
2742 fsnotify_link_count(dentry
->d_inode
);
2750 * Make sure that the actual truncation of the file will occur outside its
2751 * directory's i_mutex. Truncate can take a long time if there is a lot of
2752 * writeout happening, and we don't want to prevent access to the directory
2753 * while waiting on the I/O.
2755 static long do_unlinkat(int dfd
, const char __user
*pathname
)
2759 struct dentry
*dentry
;
2760 struct nameidata nd
;
2761 struct inode
*inode
= NULL
;
2763 error
= user_path_parent(dfd
, pathname
, &nd
, &name
);
2768 if (nd
.last_type
!= LAST_NORM
)
2771 nd
.flags
&= ~LOOKUP_PARENT
;
2773 mutex_lock_nested(&nd
.path
.dentry
->d_inode
->i_mutex
, I_MUTEX_PARENT
);
2774 dentry
= lookup_hash(&nd
);
2775 error
= PTR_ERR(dentry
);
2776 if (!IS_ERR(dentry
)) {
2777 /* Why not before? Because we want correct error value */
2778 if (nd
.last
.name
[nd
.last
.len
])
2780 inode
= dentry
->d_inode
;
2783 error
= mnt_want_write(nd
.path
.mnt
);
2786 error
= security_path_unlink(&nd
.path
, dentry
);
2789 error
= vfs_unlink(nd
.path
.dentry
->d_inode
, dentry
);
2791 mnt_drop_write(nd
.path
.mnt
);
2795 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
2797 iput(inode
); /* truncate the inode here */
2804 error
= !dentry
->d_inode
? -ENOENT
:
2805 S_ISDIR(dentry
->d_inode
->i_mode
) ? -EISDIR
: -ENOTDIR
;
2809 SYSCALL_DEFINE3(unlinkat
, int, dfd
, const char __user
*, pathname
, int, flag
)
2811 if ((flag
& ~AT_REMOVEDIR
) != 0)
2814 if (flag
& AT_REMOVEDIR
)
2815 return do_rmdir(dfd
, pathname
);
2817 return do_unlinkat(dfd
, pathname
);
2820 SYSCALL_DEFINE1(unlink
, const char __user
*, pathname
)
2822 return do_unlinkat(AT_FDCWD
, pathname
);
2825 int vfs_symlink(struct inode
*dir
, struct dentry
*dentry
, const char *oldname
)
2827 int error
= may_create(dir
, dentry
);
2832 if (!dir
->i_op
->symlink
)
2835 error
= security_inode_symlink(dir
, dentry
, oldname
);
2839 error
= dir
->i_op
->symlink(dir
, dentry
, oldname
);
2841 fsnotify_create(dir
, dentry
);
2845 SYSCALL_DEFINE3(symlinkat
, const char __user
*, oldname
,
2846 int, newdfd
, const char __user
*, newname
)
2851 struct dentry
*dentry
;
2852 struct nameidata nd
;
2854 from
= getname(oldname
);
2856 return PTR_ERR(from
);
2858 error
= user_path_parent(newdfd
, newname
, &nd
, &to
);
2862 dentry
= lookup_create(&nd
, 0);
2863 error
= PTR_ERR(dentry
);
2867 error
= mnt_want_write(nd
.path
.mnt
);
2870 error
= security_path_symlink(&nd
.path
, dentry
, from
);
2872 goto out_drop_write
;
2873 error
= vfs_symlink(nd
.path
.dentry
->d_inode
, dentry
, from
);
2875 mnt_drop_write(nd
.path
.mnt
);
2879 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
2887 SYSCALL_DEFINE2(symlink
, const char __user
*, oldname
, const char __user
*, newname
)
2889 return sys_symlinkat(oldname
, AT_FDCWD
, newname
);
2892 int vfs_link(struct dentry
*old_dentry
, struct inode
*dir
, struct dentry
*new_dentry
)
2894 struct inode
*inode
= old_dentry
->d_inode
;
2900 error
= may_create(dir
, new_dentry
);
2904 if (dir
->i_sb
!= inode
->i_sb
)
2908 * A link to an append-only or immutable file cannot be created.
2910 if (IS_APPEND(inode
) || IS_IMMUTABLE(inode
))
2912 if (!dir
->i_op
->link
)
2914 if (S_ISDIR(inode
->i_mode
))
2917 error
= security_inode_link(old_dentry
, dir
, new_dentry
);
2921 mutex_lock(&inode
->i_mutex
);
2922 /* Make sure we don't allow creating hardlink to an unlinked file */
2923 if (inode
->i_nlink
== 0)
2926 error
= dir
->i_op
->link(old_dentry
, dir
, new_dentry
);
2927 mutex_unlock(&inode
->i_mutex
);
2929 fsnotify_link(dir
, inode
, new_dentry
);
2934 * Hardlinks are often used in delicate situations. We avoid
2935 * security-related surprises by not following symlinks on the
2938 * We don't follow them on the oldname either to be compatible
2939 * with linux 2.0, and to avoid hard-linking to directories
2940 * and other special files. --ADM
2942 SYSCALL_DEFINE5(linkat
, int, olddfd
, const char __user
*, oldname
,
2943 int, newdfd
, const char __user
*, newname
, int, flags
)
2945 struct dentry
*new_dentry
;
2946 struct nameidata nd
;
2947 struct path old_path
;
2952 if ((flags
& ~(AT_SYMLINK_FOLLOW
| AT_EMPTY_PATH
)) != 0)
2955 * To use null names we require CAP_DAC_READ_SEARCH
2956 * This ensures that not everyone will be able to create
2957 * handlink using the passed filedescriptor.
2959 if (flags
& AT_EMPTY_PATH
) {
2960 if (!capable(CAP_DAC_READ_SEARCH
))
2965 if (flags
& AT_SYMLINK_FOLLOW
)
2966 how
|= LOOKUP_FOLLOW
;
2968 error
= user_path_at(olddfd
, oldname
, how
, &old_path
);
2972 error
= user_path_parent(newdfd
, newname
, &nd
, &to
);
2976 if (old_path
.mnt
!= nd
.path
.mnt
)
2978 new_dentry
= lookup_create(&nd
, 0);
2979 error
= PTR_ERR(new_dentry
);
2980 if (IS_ERR(new_dentry
))
2982 error
= mnt_want_write(nd
.path
.mnt
);
2985 error
= security_path_link(old_path
.dentry
, &nd
.path
, new_dentry
);
2987 goto out_drop_write
;
2988 error
= vfs_link(old_path
.dentry
, nd
.path
.dentry
->d_inode
, new_dentry
);
2990 mnt_drop_write(nd
.path
.mnt
);
2994 mutex_unlock(&nd
.path
.dentry
->d_inode
->i_mutex
);
2999 path_put(&old_path
);
3004 SYSCALL_DEFINE2(link
, const char __user
*, oldname
, const char __user
*, newname
)
3006 return sys_linkat(AT_FDCWD
, oldname
, AT_FDCWD
, newname
, 0);
3010 * The worst of all namespace operations - renaming directory. "Perverted"
3011 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
3013 * a) we can get into loop creation. Check is done in is_subdir().
3014 * b) race potential - two innocent renames can create a loop together.
3015 * That's where 4.4 screws up. Current fix: serialization on
3016 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
3018 * c) we have to lock _three_ objects - parents and victim (if it exists).
3019 * And that - after we got ->i_mutex on parents (until then we don't know
3020 * whether the target exists). Solution: try to be smart with locking
3021 * order for inodes. We rely on the fact that tree topology may change
3022 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
3023 * move will be locked. Thus we can rank directories by the tree
3024 * (ancestors first) and rank all non-directories after them.
3025 * That works since everybody except rename does "lock parent, lookup,
3026 * lock child" and rename is under ->s_vfs_rename_mutex.
3027 * HOWEVER, it relies on the assumption that any object with ->lookup()
3028 * has no more than 1 dentry. If "hybrid" objects will ever appear,
3029 * we'd better make sure that there's no link(2) for them.
3030 * d) some filesystems don't support opened-but-unlinked directories,
3031 * either because of layout or because they are not ready to deal with
3032 * all cases correctly. The latter will be fixed (taking this sort of
3033 * stuff into VFS), but the former is not going away. Solution: the same
3034 * trick as in rmdir().
3035 * e) conversion from fhandle to dentry may come in the wrong moment - when
3036 * we are removing the target. Solution: we will have to grab ->i_mutex
3037 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
3038 * ->i_mutex on parents, which works but leads to some truly excessive
3041 static int vfs_rename_dir(struct inode
*old_dir
, struct dentry
*old_dentry
,
3042 struct inode
*new_dir
, struct dentry
*new_dentry
)
3045 struct inode
*target
;
3048 * If we are going to change the parent - check write permissions,
3049 * we'll need to flip '..'.
3051 if (new_dir
!= old_dir
) {
3052 error
= inode_permission(old_dentry
->d_inode
, MAY_WRITE
);
3057 error
= security_inode_rename(old_dir
, old_dentry
, new_dir
, new_dentry
);
3061 target
= new_dentry
->d_inode
;
3063 mutex_lock(&target
->i_mutex
);
3064 if (d_mountpoint(old_dentry
)||d_mountpoint(new_dentry
))
3068 dentry_unhash(new_dentry
);
3069 error
= old_dir
->i_op
->rename(old_dir
, old_dentry
, new_dir
, new_dentry
);
3073 target
->i_flags
|= S_DEAD
;
3074 dont_mount(new_dentry
);
3076 mutex_unlock(&target
->i_mutex
);
3077 if (d_unhashed(new_dentry
))
3078 d_rehash(new_dentry
);
3082 if (!(old_dir
->i_sb
->s_type
->fs_flags
& FS_RENAME_DOES_D_MOVE
))
3083 d_move(old_dentry
,new_dentry
);
3087 static int vfs_rename_other(struct inode
*old_dir
, struct dentry
*old_dentry
,
3088 struct inode
*new_dir
, struct dentry
*new_dentry
)
3090 struct inode
*target
;
3093 error
= security_inode_rename(old_dir
, old_dentry
, new_dir
, new_dentry
);
3098 target
= new_dentry
->d_inode
;
3100 mutex_lock(&target
->i_mutex
);
3101 if (d_mountpoint(old_dentry
)||d_mountpoint(new_dentry
))
3104 error
= old_dir
->i_op
->rename(old_dir
, old_dentry
, new_dir
, new_dentry
);
3107 dont_mount(new_dentry
);
3108 if (!(old_dir
->i_sb
->s_type
->fs_flags
& FS_RENAME_DOES_D_MOVE
))
3109 d_move(old_dentry
, new_dentry
);
3112 mutex_unlock(&target
->i_mutex
);
3117 int vfs_rename(struct inode
*old_dir
, struct dentry
*old_dentry
,
3118 struct inode
*new_dir
, struct dentry
*new_dentry
)
3121 int is_dir
= S_ISDIR(old_dentry
->d_inode
->i_mode
);
3122 const unsigned char *old_name
;
3124 if (old_dentry
->d_inode
== new_dentry
->d_inode
)
3127 error
= may_delete(old_dir
, old_dentry
, is_dir
);
3131 if (!new_dentry
->d_inode
)
3132 error
= may_create(new_dir
, new_dentry
);
3134 error
= may_delete(new_dir
, new_dentry
, is_dir
);
3138 if (!old_dir
->i_op
->rename
)
3141 old_name
= fsnotify_oldname_init(old_dentry
->d_name
.name
);
3144 error
= vfs_rename_dir(old_dir
,old_dentry
,new_dir
,new_dentry
);
3146 error
= vfs_rename_other(old_dir
,old_dentry
,new_dir
,new_dentry
);
3148 fsnotify_move(old_dir
, new_dir
, old_name
, is_dir
,
3149 new_dentry
->d_inode
, old_dentry
);
3150 fsnotify_oldname_free(old_name
);
3155 SYSCALL_DEFINE4(renameat
, int, olddfd
, const char __user
*, oldname
,
3156 int, newdfd
, const char __user
*, newname
)
3158 struct dentry
*old_dir
, *new_dir
;
3159 struct dentry
*old_dentry
, *new_dentry
;
3160 struct dentry
*trap
;
3161 struct nameidata oldnd
, newnd
;
3166 error
= user_path_parent(olddfd
, oldname
, &oldnd
, &from
);
3170 error
= user_path_parent(newdfd
, newname
, &newnd
, &to
);
3175 if (oldnd
.path
.mnt
!= newnd
.path
.mnt
)
3178 old_dir
= oldnd
.path
.dentry
;
3180 if (oldnd
.last_type
!= LAST_NORM
)
3183 new_dir
= newnd
.path
.dentry
;
3184 if (newnd
.last_type
!= LAST_NORM
)
3187 oldnd
.flags
&= ~LOOKUP_PARENT
;
3188 newnd
.flags
&= ~LOOKUP_PARENT
;
3189 newnd
.flags
|= LOOKUP_RENAME_TARGET
;
3191 trap
= lock_rename(new_dir
, old_dir
);
3193 old_dentry
= lookup_hash(&oldnd
);
3194 error
= PTR_ERR(old_dentry
);
3195 if (IS_ERR(old_dentry
))
3197 /* source must exist */
3199 if (!old_dentry
->d_inode
)
3201 /* unless the source is a directory trailing slashes give -ENOTDIR */
3202 if (!S_ISDIR(old_dentry
->d_inode
->i_mode
)) {
3204 if (oldnd
.last
.name
[oldnd
.last
.len
])
3206 if (newnd
.last
.name
[newnd
.last
.len
])
3209 /* source should not be ancestor of target */
3211 if (old_dentry
== trap
)
3213 new_dentry
= lookup_hash(&newnd
);
3214 error
= PTR_ERR(new_dentry
);
3215 if (IS_ERR(new_dentry
))
3217 /* target should not be an ancestor of source */
3219 if (new_dentry
== trap
)
3222 error
= mnt_want_write(oldnd
.path
.mnt
);
3225 error
= security_path_rename(&oldnd
.path
, old_dentry
,
3226 &newnd
.path
, new_dentry
);
3229 error
= vfs_rename(old_dir
->d_inode
, old_dentry
,
3230 new_dir
->d_inode
, new_dentry
);
3232 mnt_drop_write(oldnd
.path
.mnt
);
3238 unlock_rename(new_dir
, old_dir
);
3240 path_put(&newnd
.path
);
3243 path_put(&oldnd
.path
);
3249 SYSCALL_DEFINE2(rename
, const char __user
*, oldname
, const char __user
*, newname
)
3251 return sys_renameat(AT_FDCWD
, oldname
, AT_FDCWD
, newname
);
3254 int vfs_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
, const char *link
)
3258 len
= PTR_ERR(link
);
3263 if (len
> (unsigned) buflen
)
3265 if (copy_to_user(buffer
, link
, len
))
3272 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
3273 * have ->follow_link() touching nd only in nd_set_link(). Using (or not
3274 * using) it for any given inode is up to filesystem.
3276 int generic_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
)
3278 struct nameidata nd
;
3283 cookie
= dentry
->d_inode
->i_op
->follow_link(dentry
, &nd
);
3285 return PTR_ERR(cookie
);
3287 res
= vfs_readlink(dentry
, buffer
, buflen
, nd_get_link(&nd
));
3288 if (dentry
->d_inode
->i_op
->put_link
)
3289 dentry
->d_inode
->i_op
->put_link(dentry
, &nd
, cookie
);
3293 int vfs_follow_link(struct nameidata
*nd
, const char *link
)
3295 return __vfs_follow_link(nd
, link
);
3298 /* get the link contents into pagecache */
3299 static char *page_getlink(struct dentry
* dentry
, struct page
**ppage
)
3303 struct address_space
*mapping
= dentry
->d_inode
->i_mapping
;
3304 page
= read_mapping_page(mapping
, 0, NULL
);
3309 nd_terminate_link(kaddr
, dentry
->d_inode
->i_size
, PAGE_SIZE
- 1);
3313 int page_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
)
3315 struct page
*page
= NULL
;
3316 char *s
= page_getlink(dentry
, &page
);
3317 int res
= vfs_readlink(dentry
,buffer
,buflen
,s
);
3320 page_cache_release(page
);
3325 void *page_follow_link_light(struct dentry
*dentry
, struct nameidata
*nd
)
3327 struct page
*page
= NULL
;
3328 nd_set_link(nd
, page_getlink(dentry
, &page
));
3332 void page_put_link(struct dentry
*dentry
, struct nameidata
*nd
, void *cookie
)
3334 struct page
*page
= cookie
;
3338 page_cache_release(page
);
3343 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
3345 int __page_symlink(struct inode
*inode
, const char *symname
, int len
, int nofs
)
3347 struct address_space
*mapping
= inode
->i_mapping
;
3352 unsigned int flags
= AOP_FLAG_UNINTERRUPTIBLE
;
3354 flags
|= AOP_FLAG_NOFS
;
3357 err
= pagecache_write_begin(NULL
, mapping
, 0, len
-1,
3358 flags
, &page
, &fsdata
);
3362 kaddr
= kmap_atomic(page
, KM_USER0
);
3363 memcpy(kaddr
, symname
, len
-1);
3364 kunmap_atomic(kaddr
, KM_USER0
);
3366 err
= pagecache_write_end(NULL
, mapping
, 0, len
-1, len
-1,
3373 mark_inode_dirty(inode
);
3379 int page_symlink(struct inode
*inode
, const char *symname
, int len
)
3381 return __page_symlink(inode
, symname
, len
,
3382 !(mapping_gfp_mask(inode
->i_mapping
) & __GFP_FS
));
3385 const struct inode_operations page_symlink_inode_operations
= {
3386 .readlink
= generic_readlink
,
3387 .follow_link
= page_follow_link_light
,
3388 .put_link
= page_put_link
,
3391 EXPORT_SYMBOL(user_path_at
);
3392 EXPORT_SYMBOL(follow_down_one
);
3393 EXPORT_SYMBOL(follow_down
);
3394 EXPORT_SYMBOL(follow_up
);
3395 EXPORT_SYMBOL(get_write_access
); /* binfmt_aout */
3396 EXPORT_SYMBOL(getname
);
3397 EXPORT_SYMBOL(lock_rename
);
3398 EXPORT_SYMBOL(lookup_one_len
);
3399 EXPORT_SYMBOL(page_follow_link_light
);
3400 EXPORT_SYMBOL(page_put_link
);
3401 EXPORT_SYMBOL(page_readlink
);
3402 EXPORT_SYMBOL(__page_symlink
);
3403 EXPORT_SYMBOL(page_symlink
);
3404 EXPORT_SYMBOL(page_symlink_inode_operations
);
3405 EXPORT_SYMBOL(kern_path_parent
);
3406 EXPORT_SYMBOL(kern_path
);
3407 EXPORT_SYMBOL(vfs_path_lookup
);
3408 EXPORT_SYMBOL(inode_permission
);
3409 EXPORT_SYMBOL(file_permission
);
3410 EXPORT_SYMBOL(unlock_rename
);
3411 EXPORT_SYMBOL(vfs_create
);
3412 EXPORT_SYMBOL(vfs_follow_link
);
3413 EXPORT_SYMBOL(vfs_link
);
3414 EXPORT_SYMBOL(vfs_mkdir
);
3415 EXPORT_SYMBOL(vfs_mknod
);
3416 EXPORT_SYMBOL(generic_permission
);
3417 EXPORT_SYMBOL(vfs_readlink
);
3418 EXPORT_SYMBOL(vfs_rename
);
3419 EXPORT_SYMBOL(vfs_rmdir
);
3420 EXPORT_SYMBOL(vfs_symlink
);
3421 EXPORT_SYMBOL(vfs_unlink
);
3422 EXPORT_SYMBOL(dentry_unhash
);
3423 EXPORT_SYMBOL(generic_readlink
);