1 // SPDX-License-Identifier: GPL-2.0
5 * Copyright (C) 1991, 1992 Linus Torvalds
9 * Some corrections by tytso.
12 /* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
15 /* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.
18 #include <linux/init.h>
19 #include <linux/export.h>
20 #include <linux/kernel.h>
21 #include <linux/slab.h>
23 #include <linux/namei.h>
24 #include <linux/pagemap.h>
25 #include <linux/fsnotify.h>
26 #include <linux/personality.h>
27 #include <linux/security.h>
28 #include <linux/ima.h>
29 #include <linux/syscalls.h>
30 #include <linux/mount.h>
31 #include <linux/audit.h>
32 #include <linux/capability.h>
33 #include <linux/file.h>
34 #include <linux/fcntl.h>
35 #include <linux/device_cgroup.h>
36 #include <linux/fs_struct.h>
37 #include <linux/posix_acl.h>
38 #include <linux/hash.h>
39 #include <linux/bitops.h>
40 #include <linux/init_task.h>
41 #include <linux/uaccess.h>
46 /* [Feb-1997 T. Schoebel-Theuer]
47 * Fundamental changes in the pathname lookup mechanisms (namei)
48 * were necessary because of omirr. The reason is that omirr needs
49 * to know the _real_ pathname, not the user-supplied one, in case
50 * of symlinks (and also when transname replacements occur).
52 * The new code replaces the old recursive symlink resolution with
53 * an iterative one (in case of non-nested symlink chains). It does
54 * this with calls to <fs>_follow_link().
55 * As a side effect, dir_namei(), _namei() and follow_link() are now
56 * replaced with a single function lookup_dentry() that can handle all
57 * the special cases of the former code.
59 * With the new dcache, the pathname is stored at each inode, at least as
60 * long as the refcount of the inode is positive. As a side effect, the
61 * size of the dcache depends on the inode cache and thus is dynamic.
63 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
64 * resolution to correspond with current state of the code.
66 * Note that the symlink resolution is not *completely* iterative.
67 * There is still a significant amount of tail- and mid- recursion in
68 * the algorithm. Also, note that <fs>_readlink() is not used in
69 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
70 * may return different results than <fs>_follow_link(). Many virtual
71 * filesystems (including /proc) exhibit this behavior.
74 /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
75 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
76 * and the name already exists in form of a symlink, try to create the new
77 * name indicated by the symlink. The old code always complained that the
78 * name already exists, due to not following the symlink even if its target
79 * is nonexistent. The new semantics affects also mknod() and link() when
80 * the name is a symlink pointing to a non-existent name.
82 * I don't know which semantics is the right one, since I have no access
83 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
84 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
85 * "old" one. Personally, I think the new semantics is much more logical.
86 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
87 * file does succeed in both HP-UX and SunOs, but not in Solaris
88 * and in the old Linux semantics.
91 /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
92 * semantics. See the comments in "open_namei" and "do_link" below.
94 * [10-Sep-98 Alan Modra] Another symlink change.
97 /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
98 * inside the path - always follow.
99 * in the last component in creation/removal/renaming - never follow.
100 * if LOOKUP_FOLLOW passed - follow.
101 * if the pathname has trailing slashes - follow.
102 * otherwise - don't follow.
103 * (applied in that order).
105 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
106 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
107 * During the 2.4 we need to fix the userland stuff depending on it -
108 * hopefully we will be able to get rid of that wart in 2.5. So far only
109 * XEmacs seems to be relying on it...
112 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
113 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
114 * any extra contention...
117 /* In order to reduce some races, while at the same time doing additional
118 * checking and hopefully speeding things up, we copy filenames to the
119 * kernel data space before using them..
121 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
122 * PATH_MAX includes the nul terminator --RR.
125 #define EMBEDDED_NAME_MAX (PATH_MAX - offsetof(struct filename, iname))
128 getname_flags(const char __user
*filename
, int flags
, int *empty
)
130 struct filename
*result
;
134 result
= audit_reusename(filename
);
138 result
= __getname();
139 if (unlikely(!result
))
140 return ERR_PTR(-ENOMEM
);
143 * First, try to embed the struct filename inside the names_cache
146 kname
= (char *)result
->iname
;
147 result
->name
= kname
;
149 len
= strncpy_from_user(kname
, filename
, EMBEDDED_NAME_MAX
);
150 if (unlikely(len
< 0)) {
156 * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a
157 * separate struct filename so we can dedicate the entire
158 * names_cache allocation for the pathname, and re-do the copy from
161 if (unlikely(len
== EMBEDDED_NAME_MAX
)) {
162 const size_t size
= offsetof(struct filename
, iname
[1]);
163 kname
= (char *)result
;
166 * size is chosen that way we to guarantee that
167 * result->iname[0] is within the same object and that
168 * kname can't be equal to result->iname, no matter what.
170 result
= kzalloc(size
, GFP_KERNEL
);
171 if (unlikely(!result
)) {
173 return ERR_PTR(-ENOMEM
);
175 result
->name
= kname
;
176 len
= strncpy_from_user(kname
, filename
, PATH_MAX
);
177 if (unlikely(len
< 0)) {
182 if (unlikely(len
== PATH_MAX
)) {
185 return ERR_PTR(-ENAMETOOLONG
);
190 /* The empty path is special. */
191 if (unlikely(!len
)) {
194 if (!(flags
& LOOKUP_EMPTY
)) {
196 return ERR_PTR(-ENOENT
);
200 result
->uptr
= filename
;
201 result
->aname
= NULL
;
202 audit_getname(result
);
207 getname(const char __user
* filename
)
209 return getname_flags(filename
, 0, NULL
);
213 getname_kernel(const char * filename
)
215 struct filename
*result
;
216 int len
= strlen(filename
) + 1;
218 result
= __getname();
219 if (unlikely(!result
))
220 return ERR_PTR(-ENOMEM
);
222 if (len
<= EMBEDDED_NAME_MAX
) {
223 result
->name
= (char *)result
->iname
;
224 } else if (len
<= PATH_MAX
) {
225 const size_t size
= offsetof(struct filename
, iname
[1]);
226 struct filename
*tmp
;
228 tmp
= kmalloc(size
, GFP_KERNEL
);
229 if (unlikely(!tmp
)) {
231 return ERR_PTR(-ENOMEM
);
233 tmp
->name
= (char *)result
;
237 return ERR_PTR(-ENAMETOOLONG
);
239 memcpy((char *)result
->name
, filename
, len
);
241 result
->aname
= NULL
;
243 audit_getname(result
);
248 void putname(struct filename
*name
)
250 BUG_ON(name
->refcnt
<= 0);
252 if (--name
->refcnt
> 0)
255 if (name
->name
!= name
->iname
) {
256 __putname(name
->name
);
262 static int check_acl(struct inode
*inode
, int mask
)
264 #ifdef CONFIG_FS_POSIX_ACL
265 struct posix_acl
*acl
;
267 if (mask
& MAY_NOT_BLOCK
) {
268 acl
= get_cached_acl_rcu(inode
, ACL_TYPE_ACCESS
);
271 /* no ->get_acl() calls in RCU mode... */
272 if (is_uncached_acl(acl
))
274 return posix_acl_permission(inode
, acl
, mask
& ~MAY_NOT_BLOCK
);
277 acl
= get_acl(inode
, ACL_TYPE_ACCESS
);
281 int error
= posix_acl_permission(inode
, acl
, mask
);
282 posix_acl_release(acl
);
291 * This does the basic permission checking
293 static int acl_permission_check(struct inode
*inode
, int mask
)
295 unsigned int mode
= inode
->i_mode
;
297 if (likely(uid_eq(current_fsuid(), inode
->i_uid
)))
300 if (IS_POSIXACL(inode
) && (mode
& S_IRWXG
)) {
301 int error
= check_acl(inode
, mask
);
302 if (error
!= -EAGAIN
)
306 if (in_group_p(inode
->i_gid
))
311 * If the DACs are ok we don't need any capability check.
313 if ((mask
& ~mode
& (MAY_READ
| MAY_WRITE
| MAY_EXEC
)) == 0)
319 * generic_permission - check for access rights on a Posix-like filesystem
320 * @inode: inode to check access rights for
321 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
323 * Used to check for read/write/execute permissions on a file.
324 * We use "fsuid" for this, letting us set arbitrary permissions
325 * for filesystem access without changing the "normal" uids which
326 * are used for other things.
328 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
329 * request cannot be satisfied (eg. requires blocking or too much complexity).
330 * It would then be called again in ref-walk mode.
332 int generic_permission(struct inode
*inode
, int mask
)
337 * Do the basic permission checks.
339 ret
= acl_permission_check(inode
, mask
);
343 if (S_ISDIR(inode
->i_mode
)) {
344 /* DACs are overridable for directories */
345 if (!(mask
& MAY_WRITE
))
346 if (capable_wrt_inode_uidgid(inode
,
347 CAP_DAC_READ_SEARCH
))
349 if (capable_wrt_inode_uidgid(inode
, CAP_DAC_OVERRIDE
))
355 * Searching includes executable on directories, else just read.
357 mask
&= MAY_READ
| MAY_WRITE
| MAY_EXEC
;
358 if (mask
== MAY_READ
)
359 if (capable_wrt_inode_uidgid(inode
, CAP_DAC_READ_SEARCH
))
362 * Read/write DACs are always overridable.
363 * Executable DACs are overridable when there is
364 * at least one exec bit set.
366 if (!(mask
& MAY_EXEC
) || (inode
->i_mode
& S_IXUGO
))
367 if (capable_wrt_inode_uidgid(inode
, CAP_DAC_OVERRIDE
))
372 EXPORT_SYMBOL(generic_permission
);
375 * We _really_ want to just do "generic_permission()" without
376 * even looking at the inode->i_op values. So we keep a cache
377 * flag in inode->i_opflags, that says "this has not special
378 * permission function, use the fast case".
380 static inline int do_inode_permission(struct inode
*inode
, int mask
)
382 if (unlikely(!(inode
->i_opflags
& IOP_FASTPERM
))) {
383 if (likely(inode
->i_op
->permission
))
384 return inode
->i_op
->permission(inode
, mask
);
386 /* This gets set once for the inode lifetime */
387 spin_lock(&inode
->i_lock
);
388 inode
->i_opflags
|= IOP_FASTPERM
;
389 spin_unlock(&inode
->i_lock
);
391 return generic_permission(inode
, mask
);
395 * __inode_permission - Check for access rights to a given inode
396 * @inode: Inode to check permission on
397 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
399 * Check for read/write/execute permissions on an inode.
401 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
403 * This does not check for a read-only file system. You probably want
404 * inode_permission().
406 int __inode_permission(struct inode
*inode
, int mask
)
410 if (unlikely(mask
& MAY_WRITE
)) {
412 * Nobody gets write access to an immutable file.
414 if (IS_IMMUTABLE(inode
))
418 * Updating mtime will likely cause i_uid and i_gid to be
419 * written back improperly if their true value is unknown
422 if (HAS_UNMAPPED_ID(inode
))
426 retval
= do_inode_permission(inode
, mask
);
430 retval
= devcgroup_inode_permission(inode
, mask
);
434 return security_inode_permission(inode
, mask
);
436 EXPORT_SYMBOL(__inode_permission
);
439 * sb_permission - Check superblock-level permissions
440 * @sb: Superblock of inode to check permission on
441 * @inode: Inode to check permission on
442 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
444 * Separate out file-system wide checks from inode-specific permission checks.
446 static int sb_permission(struct super_block
*sb
, struct inode
*inode
, int mask
)
448 if (unlikely(mask
& MAY_WRITE
)) {
449 umode_t mode
= inode
->i_mode
;
451 /* Nobody gets write access to a read-only fs. */
452 if (sb_rdonly(sb
) && (S_ISREG(mode
) || S_ISDIR(mode
) || S_ISLNK(mode
)))
459 * inode_permission - Check for access rights to a given inode
460 * @inode: Inode to check permission on
461 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
463 * Check for read/write/execute permissions on an inode. We use fs[ug]id for
464 * this, letting us set arbitrary permissions for filesystem access without
465 * changing the "normal" UIDs which are used for other things.
467 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
469 int inode_permission(struct inode
*inode
, int mask
)
473 retval
= sb_permission(inode
->i_sb
, inode
, mask
);
476 return __inode_permission(inode
, mask
);
478 EXPORT_SYMBOL(inode_permission
);
481 * path_get - get a reference to a path
482 * @path: path to get the reference to
484 * Given a path increment the reference count to the dentry and the vfsmount.
486 void path_get(const struct path
*path
)
491 EXPORT_SYMBOL(path_get
);
494 * path_put - put a reference to a path
495 * @path: path to put the reference to
497 * Given a path decrement the reference count to the dentry and the vfsmount.
499 void path_put(const struct path
*path
)
504 EXPORT_SYMBOL(path_put
);
506 #define EMBEDDED_LEVELS 2
511 struct inode
*inode
; /* path.dentry.d_inode */
516 int total_link_count
;
519 struct delayed_call done
;
522 } *stack
, internal
[EMBEDDED_LEVELS
];
523 struct filename
*name
;
524 struct nameidata
*saved
;
525 struct inode
*link_inode
;
528 } __randomize_layout
;
530 static void set_nameidata(struct nameidata
*p
, int dfd
, struct filename
*name
)
532 struct nameidata
*old
= current
->nameidata
;
533 p
->stack
= p
->internal
;
536 p
->total_link_count
= old
? old
->total_link_count
: 0;
538 current
->nameidata
= p
;
541 static void restore_nameidata(void)
543 struct nameidata
*now
= current
->nameidata
, *old
= now
->saved
;
545 current
->nameidata
= old
;
547 old
->total_link_count
= now
->total_link_count
;
548 if (now
->stack
!= now
->internal
)
552 static int __nd_alloc_stack(struct nameidata
*nd
)
556 if (nd
->flags
& LOOKUP_RCU
) {
557 p
= kmalloc(MAXSYMLINKS
* sizeof(struct saved
),
562 p
= kmalloc(MAXSYMLINKS
* sizeof(struct saved
),
567 memcpy(p
, nd
->internal
, sizeof(nd
->internal
));
573 * path_connected - Verify that a path->dentry is below path->mnt.mnt_root
574 * @path: nameidate to verify
576 * Rename can sometimes move a file or directory outside of a bind
577 * mount, path_connected allows those cases to be detected.
579 static bool path_connected(const struct path
*path
)
581 struct vfsmount
*mnt
= path
->mnt
;
582 struct super_block
*sb
= mnt
->mnt_sb
;
584 /* Bind mounts and multi-root filesystems can have disconnected paths */
585 if (!(sb
->s_iflags
& SB_I_MULTIROOT
) && (mnt
->mnt_root
== sb
->s_root
))
588 return is_subdir(path
->dentry
, mnt
->mnt_root
);
591 static inline int nd_alloc_stack(struct nameidata
*nd
)
593 if (likely(nd
->depth
!= EMBEDDED_LEVELS
))
595 if (likely(nd
->stack
!= nd
->internal
))
597 return __nd_alloc_stack(nd
);
600 static void drop_links(struct nameidata
*nd
)
604 struct saved
*last
= nd
->stack
+ i
;
605 do_delayed_call(&last
->done
);
606 clear_delayed_call(&last
->done
);
610 static void terminate_walk(struct nameidata
*nd
)
613 if (!(nd
->flags
& LOOKUP_RCU
)) {
616 for (i
= 0; i
< nd
->depth
; i
++)
617 path_put(&nd
->stack
[i
].link
);
618 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
)) {
623 nd
->flags
&= ~LOOKUP_RCU
;
624 if (!(nd
->flags
& LOOKUP_ROOT
))
631 /* path_put is needed afterwards regardless of success or failure */
632 static bool legitimize_path(struct nameidata
*nd
,
633 struct path
*path
, unsigned seq
)
635 int res
= __legitimize_mnt(path
->mnt
, nd
->m_seq
);
642 if (unlikely(!lockref_get_not_dead(&path
->dentry
->d_lockref
))) {
646 return !read_seqcount_retry(&path
->dentry
->d_seq
, seq
);
649 static bool legitimize_links(struct nameidata
*nd
)
652 for (i
= 0; i
< nd
->depth
; i
++) {
653 struct saved
*last
= nd
->stack
+ i
;
654 if (unlikely(!legitimize_path(nd
, &last
->link
, last
->seq
))) {
664 * Path walking has 2 modes, rcu-walk and ref-walk (see
665 * Documentation/filesystems/path-lookup.txt). In situations when we can't
666 * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
667 * normal reference counts on dentries and vfsmounts to transition to ref-walk
668 * mode. Refcounts are grabbed at the last known good point before rcu-walk
669 * got stuck, so ref-walk may continue from there. If this is not successful
670 * (eg. a seqcount has changed), then failure is returned and it's up to caller
671 * to restart the path walk from the beginning in ref-walk mode.
675 * unlazy_walk - try to switch to ref-walk mode.
676 * @nd: nameidata pathwalk data
677 * Returns: 0 on success, -ECHILD on failure
679 * unlazy_walk attempts to legitimize the current nd->path and nd->root
681 * Must be called from rcu-walk context.
682 * Nothing should touch nameidata between unlazy_walk() failure and
685 static int unlazy_walk(struct nameidata
*nd
)
687 struct dentry
*parent
= nd
->path
.dentry
;
689 BUG_ON(!(nd
->flags
& LOOKUP_RCU
));
691 nd
->flags
&= ~LOOKUP_RCU
;
692 if (unlikely(!legitimize_links(nd
)))
694 if (unlikely(!legitimize_path(nd
, &nd
->path
, nd
->seq
)))
696 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
)) {
697 if (unlikely(!legitimize_path(nd
, &nd
->root
, nd
->root_seq
)))
701 BUG_ON(nd
->inode
!= parent
->d_inode
);
706 nd
->path
.dentry
= NULL
;
708 if (!(nd
->flags
& LOOKUP_ROOT
))
716 * unlazy_child - try to switch to ref-walk mode.
717 * @nd: nameidata pathwalk data
718 * @dentry: child of nd->path.dentry
719 * @seq: seq number to check dentry against
720 * Returns: 0 on success, -ECHILD on failure
722 * unlazy_child attempts to legitimize the current nd->path, nd->root and dentry
723 * for ref-walk mode. @dentry must be a path found by a do_lookup call on
724 * @nd. Must be called from rcu-walk context.
725 * Nothing should touch nameidata between unlazy_child() failure and
728 static int unlazy_child(struct nameidata
*nd
, struct dentry
*dentry
, unsigned seq
)
730 BUG_ON(!(nd
->flags
& LOOKUP_RCU
));
732 nd
->flags
&= ~LOOKUP_RCU
;
733 if (unlikely(!legitimize_links(nd
)))
735 if (unlikely(!legitimize_mnt(nd
->path
.mnt
, nd
->m_seq
)))
737 if (unlikely(!lockref_get_not_dead(&nd
->path
.dentry
->d_lockref
)))
741 * We need to move both the parent and the dentry from the RCU domain
742 * to be properly refcounted. And the sequence number in the dentry
743 * validates *both* dentry counters, since we checked the sequence
744 * number of the parent after we got the child sequence number. So we
745 * know the parent must still be valid if the child sequence number is
747 if (unlikely(!lockref_get_not_dead(&dentry
->d_lockref
)))
749 if (unlikely(read_seqcount_retry(&dentry
->d_seq
, seq
))) {
755 * Sequence counts matched. Now make sure that the root is
756 * still valid and get it if required.
758 if (nd
->root
.mnt
&& !(nd
->flags
& LOOKUP_ROOT
)) {
759 if (unlikely(!legitimize_path(nd
, &nd
->root
, nd
->root_seq
))) {
772 nd
->path
.dentry
= NULL
;
776 if (!(nd
->flags
& LOOKUP_ROOT
))
781 static inline int d_revalidate(struct dentry
*dentry
, unsigned int flags
)
783 if (unlikely(dentry
->d_flags
& DCACHE_OP_REVALIDATE
))
784 return dentry
->d_op
->d_revalidate(dentry
, flags
);
790 * complete_walk - successful completion of path walk
791 * @nd: pointer nameidata
793 * If we had been in RCU mode, drop out of it and legitimize nd->path.
794 * Revalidate the final result, unless we'd already done that during
795 * the path walk or the filesystem doesn't ask for it. Return 0 on
796 * success, -error on failure. In case of failure caller does not
797 * need to drop nd->path.
799 static int complete_walk(struct nameidata
*nd
)
801 struct dentry
*dentry
= nd
->path
.dentry
;
804 if (nd
->flags
& LOOKUP_RCU
) {
805 if (!(nd
->flags
& LOOKUP_ROOT
))
807 if (unlikely(unlazy_walk(nd
)))
811 if (likely(!(nd
->flags
& LOOKUP_JUMPED
)))
814 if (likely(!(dentry
->d_flags
& DCACHE_OP_WEAK_REVALIDATE
)))
817 status
= dentry
->d_op
->d_weak_revalidate(dentry
, nd
->flags
);
827 static void set_root(struct nameidata
*nd
)
829 struct fs_struct
*fs
= current
->fs
;
831 if (nd
->flags
& LOOKUP_RCU
) {
835 seq
= read_seqcount_begin(&fs
->seq
);
837 nd
->root_seq
= __read_seqcount_begin(&nd
->root
.dentry
->d_seq
);
838 } while (read_seqcount_retry(&fs
->seq
, seq
));
840 get_fs_root(fs
, &nd
->root
);
844 static void path_put_conditional(struct path
*path
, struct nameidata
*nd
)
847 if (path
->mnt
!= nd
->path
.mnt
)
851 static inline void path_to_nameidata(const struct path
*path
,
852 struct nameidata
*nd
)
854 if (!(nd
->flags
& LOOKUP_RCU
)) {
855 dput(nd
->path
.dentry
);
856 if (nd
->path
.mnt
!= path
->mnt
)
857 mntput(nd
->path
.mnt
);
859 nd
->path
.mnt
= path
->mnt
;
860 nd
->path
.dentry
= path
->dentry
;
863 static int nd_jump_root(struct nameidata
*nd
)
865 if (nd
->flags
& LOOKUP_RCU
) {
869 nd
->inode
= d
->d_inode
;
870 nd
->seq
= nd
->root_seq
;
871 if (unlikely(read_seqcount_retry(&d
->d_seq
, nd
->seq
)))
877 nd
->inode
= nd
->path
.dentry
->d_inode
;
879 nd
->flags
|= LOOKUP_JUMPED
;
884 * Helper to directly jump to a known parsed path from ->get_link,
885 * caller must have taken a reference to path beforehand.
887 void nd_jump_link(struct path
*path
)
889 struct nameidata
*nd
= current
->nameidata
;
893 nd
->inode
= nd
->path
.dentry
->d_inode
;
894 nd
->flags
|= LOOKUP_JUMPED
;
897 static inline void put_link(struct nameidata
*nd
)
899 struct saved
*last
= nd
->stack
+ --nd
->depth
;
900 do_delayed_call(&last
->done
);
901 if (!(nd
->flags
& LOOKUP_RCU
))
902 path_put(&last
->link
);
905 int sysctl_protected_symlinks __read_mostly
= 1;
906 int sysctl_protected_hardlinks __read_mostly
= 1;
909 * may_follow_link - Check symlink following for unsafe situations
910 * @nd: nameidata pathwalk data
912 * In the case of the sysctl_protected_symlinks sysctl being enabled,
913 * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
914 * in a sticky world-writable directory. This is to protect privileged
915 * processes from failing races against path names that may change out
916 * from under them by way of other users creating malicious symlinks.
917 * It will permit symlinks to be followed only when outside a sticky
918 * world-writable directory, or when the uid of the symlink and follower
919 * match, or when the directory owner matches the symlink's owner.
921 * Returns 0 if following the symlink is allowed, -ve on error.
923 static inline int may_follow_link(struct nameidata
*nd
)
925 const struct inode
*inode
;
926 const struct inode
*parent
;
929 if (!sysctl_protected_symlinks
)
932 /* Allowed if owner and follower match. */
933 inode
= nd
->link_inode
;
934 if (uid_eq(current_cred()->fsuid
, inode
->i_uid
))
937 /* Allowed if parent directory not sticky and world-writable. */
939 if ((parent
->i_mode
& (S_ISVTX
|S_IWOTH
)) != (S_ISVTX
|S_IWOTH
))
942 /* Allowed if parent directory and link owner match. */
943 puid
= parent
->i_uid
;
944 if (uid_valid(puid
) && uid_eq(puid
, inode
->i_uid
))
947 if (nd
->flags
& LOOKUP_RCU
)
950 audit_log_link_denied("follow_link", &nd
->stack
[0].link
);
955 * safe_hardlink_source - Check for safe hardlink conditions
956 * @inode: the source inode to hardlink from
958 * Return false if at least one of the following conditions:
959 * - inode is not a regular file
961 * - inode is setgid and group-exec
962 * - access failure for read and write
964 * Otherwise returns true.
966 static bool safe_hardlink_source(struct inode
*inode
)
968 umode_t mode
= inode
->i_mode
;
970 /* Special files should not get pinned to the filesystem. */
974 /* Setuid files should not get pinned to the filesystem. */
978 /* Executable setgid files should not get pinned to the filesystem. */
979 if ((mode
& (S_ISGID
| S_IXGRP
)) == (S_ISGID
| S_IXGRP
))
982 /* Hardlinking to unreadable or unwritable sources is dangerous. */
983 if (inode_permission(inode
, MAY_READ
| MAY_WRITE
))
990 * may_linkat - Check permissions for creating a hardlink
991 * @link: the source to hardlink from
993 * Block hardlink when all of:
994 * - sysctl_protected_hardlinks enabled
995 * - fsuid does not match inode
996 * - hardlink source is unsafe (see safe_hardlink_source() above)
997 * - not CAP_FOWNER in a namespace with the inode owner uid mapped
999 * Returns 0 if successful, -ve on error.
1001 static int may_linkat(struct path
*link
)
1003 struct inode
*inode
;
1005 if (!sysctl_protected_hardlinks
)
1008 inode
= link
->dentry
->d_inode
;
1010 /* Source inode owner (or CAP_FOWNER) can hardlink all they like,
1011 * otherwise, it must be a safe source.
1013 if (safe_hardlink_source(inode
) || inode_owner_or_capable(inode
))
1016 audit_log_link_denied("linkat", link
);
1020 static __always_inline
1021 const char *get_link(struct nameidata
*nd
)
1023 struct saved
*last
= nd
->stack
+ nd
->depth
- 1;
1024 struct dentry
*dentry
= last
->link
.dentry
;
1025 struct inode
*inode
= nd
->link_inode
;
1029 if (!(nd
->flags
& LOOKUP_RCU
)) {
1030 touch_atime(&last
->link
);
1032 } else if (atime_needs_update_rcu(&last
->link
, inode
)) {
1033 if (unlikely(unlazy_walk(nd
)))
1034 return ERR_PTR(-ECHILD
);
1035 touch_atime(&last
->link
);
1038 error
= security_inode_follow_link(dentry
, inode
,
1039 nd
->flags
& LOOKUP_RCU
);
1040 if (unlikely(error
))
1041 return ERR_PTR(error
);
1043 nd
->last_type
= LAST_BIND
;
1044 res
= inode
->i_link
;
1046 const char * (*get
)(struct dentry
*, struct inode
*,
1047 struct delayed_call
*);
1048 get
= inode
->i_op
->get_link
;
1049 if (nd
->flags
& LOOKUP_RCU
) {
1050 res
= get(NULL
, inode
, &last
->done
);
1051 if (res
== ERR_PTR(-ECHILD
)) {
1052 if (unlikely(unlazy_walk(nd
)))
1053 return ERR_PTR(-ECHILD
);
1054 res
= get(dentry
, inode
, &last
->done
);
1057 res
= get(dentry
, inode
, &last
->done
);
1059 if (IS_ERR_OR_NULL(res
))
1065 if (unlikely(nd_jump_root(nd
)))
1066 return ERR_PTR(-ECHILD
);
1067 while (unlikely(*++res
== '/'))
1076 * follow_up - Find the mountpoint of path's vfsmount
1078 * Given a path, find the mountpoint of its source file system.
1079 * Replace @path with the path of the mountpoint in the parent mount.
1082 * Return 1 if we went up a level and 0 if we were already at the
1085 int follow_up(struct path
*path
)
1087 struct mount
*mnt
= real_mount(path
->mnt
);
1088 struct mount
*parent
;
1089 struct dentry
*mountpoint
;
1091 read_seqlock_excl(&mount_lock
);
1092 parent
= mnt
->mnt_parent
;
1093 if (parent
== mnt
) {
1094 read_sequnlock_excl(&mount_lock
);
1097 mntget(&parent
->mnt
);
1098 mountpoint
= dget(mnt
->mnt_mountpoint
);
1099 read_sequnlock_excl(&mount_lock
);
1101 path
->dentry
= mountpoint
;
1103 path
->mnt
= &parent
->mnt
;
1106 EXPORT_SYMBOL(follow_up
);
1109 * Perform an automount
1110 * - return -EISDIR to tell follow_managed() to stop and return the path we
1113 static int follow_automount(struct path
*path
, struct nameidata
*nd
,
1116 struct vfsmount
*mnt
;
1119 if (!path
->dentry
->d_op
|| !path
->dentry
->d_op
->d_automount
)
1122 /* We don't want to mount if someone's just doing a stat -
1123 * unless they're stat'ing a directory and appended a '/' to
1126 * We do, however, want to mount if someone wants to open or
1127 * create a file of any type under the mountpoint, wants to
1128 * traverse through the mountpoint or wants to open the
1129 * mounted directory. Also, autofs may mark negative dentries
1130 * as being automount points. These will need the attentions
1131 * of the daemon to instantiate them before they can be used.
1133 if (!(nd
->flags
& (LOOKUP_PARENT
| LOOKUP_DIRECTORY
|
1134 LOOKUP_OPEN
| LOOKUP_CREATE
| LOOKUP_AUTOMOUNT
)) &&
1135 path
->dentry
->d_inode
)
1138 nd
->total_link_count
++;
1139 if (nd
->total_link_count
>= 40)
1142 mnt
= path
->dentry
->d_op
->d_automount(path
);
1145 * The filesystem is allowed to return -EISDIR here to indicate
1146 * it doesn't want to automount. For instance, autofs would do
1147 * this so that its userspace daemon can mount on this dentry.
1149 * However, we can only permit this if it's a terminal point in
1150 * the path being looked up; if it wasn't then the remainder of
1151 * the path is inaccessible and we should say so.
1153 if (PTR_ERR(mnt
) == -EISDIR
&& (nd
->flags
& LOOKUP_PARENT
))
1155 return PTR_ERR(mnt
);
1158 if (!mnt
) /* mount collision */
1161 if (!*need_mntput
) {
1162 /* lock_mount() may release path->mnt on error */
1164 *need_mntput
= true;
1166 err
= finish_automount(mnt
, path
);
1170 /* Someone else made a mount here whilst we were busy */
1175 path
->dentry
= dget(mnt
->mnt_root
);
1184 * Handle a dentry that is managed in some way.
1185 * - Flagged for transit management (autofs)
1186 * - Flagged as mountpoint
1187 * - Flagged as automount point
1189 * This may only be called in refwalk mode.
1191 * Serialization is taken care of in namespace.c
1193 static int follow_managed(struct path
*path
, struct nameidata
*nd
)
1195 struct vfsmount
*mnt
= path
->mnt
; /* held by caller, must be left alone */
1197 bool need_mntput
= false;
1200 /* Given that we're not holding a lock here, we retain the value in a
1201 * local variable for each dentry as we look at it so that we don't see
1202 * the components of that value change under us */
1203 while (managed
= READ_ONCE(path
->dentry
->d_flags
),
1204 managed
&= DCACHE_MANAGED_DENTRY
,
1205 unlikely(managed
!= 0)) {
1206 /* Allow the filesystem to manage the transit without i_mutex
1208 if (managed
& DCACHE_MANAGE_TRANSIT
) {
1209 BUG_ON(!path
->dentry
->d_op
);
1210 BUG_ON(!path
->dentry
->d_op
->d_manage
);
1211 ret
= path
->dentry
->d_op
->d_manage(path
, false);
1216 /* Transit to a mounted filesystem. */
1217 if (managed
& DCACHE_MOUNTED
) {
1218 struct vfsmount
*mounted
= lookup_mnt(path
);
1223 path
->mnt
= mounted
;
1224 path
->dentry
= dget(mounted
->mnt_root
);
1229 /* Something is mounted on this dentry in another
1230 * namespace and/or whatever was mounted there in this
1231 * namespace got unmounted before lookup_mnt() could
1235 /* Handle an automount point */
1236 if (managed
& DCACHE_NEED_AUTOMOUNT
) {
1237 ret
= follow_automount(path
, nd
, &need_mntput
);
1243 /* We didn't change the current path point */
1247 if (need_mntput
&& path
->mnt
== mnt
)
1249 if (ret
== -EISDIR
|| !ret
)
1252 nd
->flags
|= LOOKUP_JUMPED
;
1253 if (unlikely(ret
< 0))
1254 path_put_conditional(path
, nd
);
1258 int follow_down_one(struct path
*path
)
1260 struct vfsmount
*mounted
;
1262 mounted
= lookup_mnt(path
);
1266 path
->mnt
= mounted
;
1267 path
->dentry
= dget(mounted
->mnt_root
);
1272 EXPORT_SYMBOL(follow_down_one
);
1274 static inline int managed_dentry_rcu(const struct path
*path
)
1276 return (path
->dentry
->d_flags
& DCACHE_MANAGE_TRANSIT
) ?
1277 path
->dentry
->d_op
->d_manage(path
, true) : 0;
1281 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
1282 * we meet a managed dentry that would need blocking.
1284 static bool __follow_mount_rcu(struct nameidata
*nd
, struct path
*path
,
1285 struct inode
**inode
, unsigned *seqp
)
1288 struct mount
*mounted
;
1290 * Don't forget we might have a non-mountpoint managed dentry
1291 * that wants to block transit.
1293 switch (managed_dentry_rcu(path
)) {
1303 if (!d_mountpoint(path
->dentry
))
1304 return !(path
->dentry
->d_flags
& DCACHE_NEED_AUTOMOUNT
);
1306 mounted
= __lookup_mnt(path
->mnt
, path
->dentry
);
1309 path
->mnt
= &mounted
->mnt
;
1310 path
->dentry
= mounted
->mnt
.mnt_root
;
1311 nd
->flags
|= LOOKUP_JUMPED
;
1312 *seqp
= read_seqcount_begin(&path
->dentry
->d_seq
);
1314 * Update the inode too. We don't need to re-check the
1315 * dentry sequence number here after this d_inode read,
1316 * because a mount-point is always pinned.
1318 *inode
= path
->dentry
->d_inode
;
1320 return !read_seqretry(&mount_lock
, nd
->m_seq
) &&
1321 !(path
->dentry
->d_flags
& DCACHE_NEED_AUTOMOUNT
);
1324 static int follow_dotdot_rcu(struct nameidata
*nd
)
1326 struct inode
*inode
= nd
->inode
;
1329 if (path_equal(&nd
->path
, &nd
->root
))
1331 if (nd
->path
.dentry
!= nd
->path
.mnt
->mnt_root
) {
1332 struct dentry
*old
= nd
->path
.dentry
;
1333 struct dentry
*parent
= old
->d_parent
;
1336 inode
= parent
->d_inode
;
1337 seq
= read_seqcount_begin(&parent
->d_seq
);
1338 if (unlikely(read_seqcount_retry(&old
->d_seq
, nd
->seq
)))
1340 nd
->path
.dentry
= parent
;
1342 if (unlikely(!path_connected(&nd
->path
)))
1346 struct mount
*mnt
= real_mount(nd
->path
.mnt
);
1347 struct mount
*mparent
= mnt
->mnt_parent
;
1348 struct dentry
*mountpoint
= mnt
->mnt_mountpoint
;
1349 struct inode
*inode2
= mountpoint
->d_inode
;
1350 unsigned seq
= read_seqcount_begin(&mountpoint
->d_seq
);
1351 if (unlikely(read_seqretry(&mount_lock
, nd
->m_seq
)))
1353 if (&mparent
->mnt
== nd
->path
.mnt
)
1355 /* we know that mountpoint was pinned */
1356 nd
->path
.dentry
= mountpoint
;
1357 nd
->path
.mnt
= &mparent
->mnt
;
1362 while (unlikely(d_mountpoint(nd
->path
.dentry
))) {
1363 struct mount
*mounted
;
1364 mounted
= __lookup_mnt(nd
->path
.mnt
, nd
->path
.dentry
);
1365 if (unlikely(read_seqretry(&mount_lock
, nd
->m_seq
)))
1369 nd
->path
.mnt
= &mounted
->mnt
;
1370 nd
->path
.dentry
= mounted
->mnt
.mnt_root
;
1371 inode
= nd
->path
.dentry
->d_inode
;
1372 nd
->seq
= read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1379 * Follow down to the covering mount currently visible to userspace. At each
1380 * point, the filesystem owning that dentry may be queried as to whether the
1381 * caller is permitted to proceed or not.
1383 int follow_down(struct path
*path
)
1388 while (managed
= READ_ONCE(path
->dentry
->d_flags
),
1389 unlikely(managed
& DCACHE_MANAGED_DENTRY
)) {
1390 /* Allow the filesystem to manage the transit without i_mutex
1393 * We indicate to the filesystem if someone is trying to mount
1394 * something here. This gives autofs the chance to deny anyone
1395 * other than its daemon the right to mount on its
1398 * The filesystem may sleep at this point.
1400 if (managed
& DCACHE_MANAGE_TRANSIT
) {
1401 BUG_ON(!path
->dentry
->d_op
);
1402 BUG_ON(!path
->dentry
->d_op
->d_manage
);
1403 ret
= path
->dentry
->d_op
->d_manage(path
, false);
1405 return ret
== -EISDIR
? 0 : ret
;
1408 /* Transit to a mounted filesystem. */
1409 if (managed
& DCACHE_MOUNTED
) {
1410 struct vfsmount
*mounted
= lookup_mnt(path
);
1415 path
->mnt
= mounted
;
1416 path
->dentry
= dget(mounted
->mnt_root
);
1420 /* Don't handle automount points here */
1425 EXPORT_SYMBOL(follow_down
);
1428 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1430 static void follow_mount(struct path
*path
)
1432 while (d_mountpoint(path
->dentry
)) {
1433 struct vfsmount
*mounted
= lookup_mnt(path
);
1438 path
->mnt
= mounted
;
1439 path
->dentry
= dget(mounted
->mnt_root
);
1443 static int path_parent_directory(struct path
*path
)
1445 struct dentry
*old
= path
->dentry
;
1446 /* rare case of legitimate dget_parent()... */
1447 path
->dentry
= dget_parent(path
->dentry
);
1449 if (unlikely(!path_connected(path
)))
1454 static int follow_dotdot(struct nameidata
*nd
)
1457 if (nd
->path
.dentry
== nd
->root
.dentry
&&
1458 nd
->path
.mnt
== nd
->root
.mnt
) {
1461 if (nd
->path
.dentry
!= nd
->path
.mnt
->mnt_root
) {
1462 int ret
= path_parent_directory(&nd
->path
);
1467 if (!follow_up(&nd
->path
))
1470 follow_mount(&nd
->path
);
1471 nd
->inode
= nd
->path
.dentry
->d_inode
;
1476 * This looks up the name in dcache and possibly revalidates the found dentry.
1477 * NULL is returned if the dentry does not exist in the cache.
1479 static struct dentry
*lookup_dcache(const struct qstr
*name
,
1483 struct dentry
*dentry
= d_lookup(dir
, name
);
1485 int error
= d_revalidate(dentry
, flags
);
1486 if (unlikely(error
<= 0)) {
1488 d_invalidate(dentry
);
1490 return ERR_PTR(error
);
1497 * Call i_op->lookup on the dentry. The dentry must be negative and
1500 * dir->d_inode->i_mutex must be held
1502 static struct dentry
*lookup_real(struct inode
*dir
, struct dentry
*dentry
,
1507 /* Don't create child dentry for a dead directory. */
1508 if (unlikely(IS_DEADDIR(dir
))) {
1510 return ERR_PTR(-ENOENT
);
1513 old
= dir
->i_op
->lookup(dir
, dentry
, flags
);
1514 if (unlikely(old
)) {
1521 static struct dentry
*__lookup_hash(const struct qstr
*name
,
1522 struct dentry
*base
, unsigned int flags
)
1524 struct dentry
*dentry
= lookup_dcache(name
, base
, flags
);
1529 dentry
= d_alloc(base
, name
);
1530 if (unlikely(!dentry
))
1531 return ERR_PTR(-ENOMEM
);
1533 return lookup_real(base
->d_inode
, dentry
, flags
);
1536 static int lookup_fast(struct nameidata
*nd
,
1537 struct path
*path
, struct inode
**inode
,
1540 struct vfsmount
*mnt
= nd
->path
.mnt
;
1541 struct dentry
*dentry
, *parent
= nd
->path
.dentry
;
1546 * Rename seqlock is not required here because in the off chance
1547 * of a false negative due to a concurrent rename, the caller is
1548 * going to fall back to non-racy lookup.
1550 if (nd
->flags
& LOOKUP_RCU
) {
1553 dentry
= __d_lookup_rcu(parent
, &nd
->last
, &seq
);
1554 if (unlikely(!dentry
)) {
1555 if (unlazy_walk(nd
))
1561 * This sequence count validates that the inode matches
1562 * the dentry name information from lookup.
1564 *inode
= d_backing_inode(dentry
);
1565 negative
= d_is_negative(dentry
);
1566 if (unlikely(read_seqcount_retry(&dentry
->d_seq
, seq
)))
1570 * This sequence count validates that the parent had no
1571 * changes while we did the lookup of the dentry above.
1573 * The memory barrier in read_seqcount_begin of child is
1574 * enough, we can use __read_seqcount_retry here.
1576 if (unlikely(__read_seqcount_retry(&parent
->d_seq
, nd
->seq
)))
1580 status
= d_revalidate(dentry
, nd
->flags
);
1581 if (likely(status
> 0)) {
1583 * Note: do negative dentry check after revalidation in
1584 * case that drops it.
1586 if (unlikely(negative
))
1589 path
->dentry
= dentry
;
1590 if (likely(__follow_mount_rcu(nd
, path
, inode
, seqp
)))
1593 if (unlazy_child(nd
, dentry
, seq
))
1595 if (unlikely(status
== -ECHILD
))
1596 /* we'd been told to redo it in non-rcu mode */
1597 status
= d_revalidate(dentry
, nd
->flags
);
1599 dentry
= __d_lookup(parent
, &nd
->last
);
1600 if (unlikely(!dentry
))
1602 status
= d_revalidate(dentry
, nd
->flags
);
1604 if (unlikely(status
<= 0)) {
1606 d_invalidate(dentry
);
1610 if (unlikely(d_is_negative(dentry
))) {
1616 path
->dentry
= dentry
;
1617 err
= follow_managed(path
, nd
);
1618 if (likely(err
> 0))
1619 *inode
= d_backing_inode(path
->dentry
);
1623 /* Fast lookup failed, do it the slow way */
1624 static struct dentry
*lookup_slow(const struct qstr
*name
,
1628 struct dentry
*dentry
= ERR_PTR(-ENOENT
), *old
;
1629 struct inode
*inode
= dir
->d_inode
;
1630 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq
);
1632 inode_lock_shared(inode
);
1633 /* Don't go there if it's already dead */
1634 if (unlikely(IS_DEADDIR(inode
)))
1637 dentry
= d_alloc_parallel(dir
, name
, &wq
);
1640 if (unlikely(!d_in_lookup(dentry
))) {
1641 if (!(flags
& LOOKUP_NO_REVAL
)) {
1642 int error
= d_revalidate(dentry
, flags
);
1643 if (unlikely(error
<= 0)) {
1645 d_invalidate(dentry
);
1650 dentry
= ERR_PTR(error
);
1654 old
= inode
->i_op
->lookup(inode
, dentry
, flags
);
1655 d_lookup_done(dentry
);
1656 if (unlikely(old
)) {
1662 inode_unlock_shared(inode
);
1666 static inline int may_lookup(struct nameidata
*nd
)
1668 if (nd
->flags
& LOOKUP_RCU
) {
1669 int err
= inode_permission(nd
->inode
, MAY_EXEC
|MAY_NOT_BLOCK
);
1672 if (unlazy_walk(nd
))
1675 return inode_permission(nd
->inode
, MAY_EXEC
);
1678 static inline int handle_dots(struct nameidata
*nd
, int type
)
1680 if (type
== LAST_DOTDOT
) {
1683 if (nd
->flags
& LOOKUP_RCU
) {
1684 return follow_dotdot_rcu(nd
);
1686 return follow_dotdot(nd
);
1691 static int pick_link(struct nameidata
*nd
, struct path
*link
,
1692 struct inode
*inode
, unsigned seq
)
1696 if (unlikely(nd
->total_link_count
++ >= MAXSYMLINKS
)) {
1697 path_to_nameidata(link
, nd
);
1700 if (!(nd
->flags
& LOOKUP_RCU
)) {
1701 if (link
->mnt
== nd
->path
.mnt
)
1704 error
= nd_alloc_stack(nd
);
1705 if (unlikely(error
)) {
1706 if (error
== -ECHILD
) {
1707 if (unlikely(!legitimize_path(nd
, link
, seq
))) {
1710 nd
->flags
&= ~LOOKUP_RCU
;
1711 nd
->path
.mnt
= NULL
;
1712 nd
->path
.dentry
= NULL
;
1713 if (!(nd
->flags
& LOOKUP_ROOT
))
1714 nd
->root
.mnt
= NULL
;
1716 } else if (likely(unlazy_walk(nd
)) == 0)
1717 error
= nd_alloc_stack(nd
);
1725 last
= nd
->stack
+ nd
->depth
++;
1727 clear_delayed_call(&last
->done
);
1728 nd
->link_inode
= inode
;
1733 enum {WALK_FOLLOW
= 1, WALK_MORE
= 2};
1736 * Do we need to follow links? We _really_ want to be able
1737 * to do this check without having to look at inode->i_op,
1738 * so we keep a cache of "no, this doesn't need follow_link"
1739 * for the common case.
1741 static inline int step_into(struct nameidata
*nd
, struct path
*path
,
1742 int flags
, struct inode
*inode
, unsigned seq
)
1744 if (!(flags
& WALK_MORE
) && nd
->depth
)
1746 if (likely(!d_is_symlink(path
->dentry
)) ||
1747 !(flags
& WALK_FOLLOW
|| nd
->flags
& LOOKUP_FOLLOW
)) {
1748 /* not a symlink or should not follow */
1749 path_to_nameidata(path
, nd
);
1754 /* make sure that d_is_symlink above matches inode */
1755 if (nd
->flags
& LOOKUP_RCU
) {
1756 if (read_seqcount_retry(&path
->dentry
->d_seq
, seq
))
1759 return pick_link(nd
, path
, inode
, seq
);
1762 static int walk_component(struct nameidata
*nd
, int flags
)
1765 struct inode
*inode
;
1769 * "." and ".." are special - ".." especially so because it has
1770 * to be able to know about the current root directory and
1771 * parent relationships.
1773 if (unlikely(nd
->last_type
!= LAST_NORM
)) {
1774 err
= handle_dots(nd
, nd
->last_type
);
1775 if (!(flags
& WALK_MORE
) && nd
->depth
)
1779 err
= lookup_fast(nd
, &path
, &inode
, &seq
);
1780 if (unlikely(err
<= 0)) {
1783 path
.dentry
= lookup_slow(&nd
->last
, nd
->path
.dentry
,
1785 if (IS_ERR(path
.dentry
))
1786 return PTR_ERR(path
.dentry
);
1788 path
.mnt
= nd
->path
.mnt
;
1789 err
= follow_managed(&path
, nd
);
1790 if (unlikely(err
< 0))
1793 if (unlikely(d_is_negative(path
.dentry
))) {
1794 path_to_nameidata(&path
, nd
);
1798 seq
= 0; /* we are already out of RCU mode */
1799 inode
= d_backing_inode(path
.dentry
);
1802 return step_into(nd
, &path
, flags
, inode
, seq
);
1806 * We can do the critical dentry name comparison and hashing
1807 * operations one word at a time, but we are limited to:
1809 * - Architectures with fast unaligned word accesses. We could
1810 * do a "get_unaligned()" if this helps and is sufficiently
1813 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
1814 * do not trap on the (extremely unlikely) case of a page
1815 * crossing operation.
1817 * - Furthermore, we need an efficient 64-bit compile for the
1818 * 64-bit case in order to generate the "number of bytes in
1819 * the final mask". Again, that could be replaced with a
1820 * efficient population count instruction or similar.
1822 #ifdef CONFIG_DCACHE_WORD_ACCESS
1824 #include <asm/word-at-a-time.h>
1828 /* Architecture provides HASH_MIX and fold_hash() in <asm/hash.h> */
1830 #elif defined(CONFIG_64BIT)
1832 * Register pressure in the mixing function is an issue, particularly
1833 * on 32-bit x86, but almost any function requires one state value and
1834 * one temporary. Instead, use a function designed for two state values
1835 * and no temporaries.
1837 * This function cannot create a collision in only two iterations, so
1838 * we have two iterations to achieve avalanche. In those two iterations,
1839 * we have six layers of mixing, which is enough to spread one bit's
1840 * influence out to 2^6 = 64 state bits.
1842 * Rotate constants are scored by considering either 64 one-bit input
1843 * deltas or 64*63/2 = 2016 two-bit input deltas, and finding the
1844 * probability of that delta causing a change to each of the 128 output
1845 * bits, using a sample of random initial states.
1847 * The Shannon entropy of the computed probabilities is then summed
1848 * to produce a score. Ideally, any input change has a 50% chance of
1849 * toggling any given output bit.
1851 * Mixing scores (in bits) for (12,45):
1852 * Input delta: 1-bit 2-bit
1853 * 1 round: 713.3 42542.6
1854 * 2 rounds: 2753.7 140389.8
1855 * 3 rounds: 5954.1 233458.2
1856 * 4 rounds: 7862.6 256672.2
1857 * Perfect: 8192 258048
1858 * (64*128) (64*63/2 * 128)
1860 #define HASH_MIX(x, y, a) \
1862 y ^= x, x = rol64(x,12),\
1863 x += y, y = rol64(y,45),\
1867 * Fold two longs into one 32-bit hash value. This must be fast, but
1868 * latency isn't quite as critical, as there is a fair bit of additional
1869 * work done before the hash value is used.
1871 static inline unsigned int fold_hash(unsigned long x
, unsigned long y
)
1873 y
^= x
* GOLDEN_RATIO_64
;
1874 y
*= GOLDEN_RATIO_64
;
1878 #else /* 32-bit case */
1881 * Mixing scores (in bits) for (7,20):
1882 * Input delta: 1-bit 2-bit
1883 * 1 round: 330.3 9201.6
1884 * 2 rounds: 1246.4 25475.4
1885 * 3 rounds: 1907.1 31295.1
1886 * 4 rounds: 2042.3 31718.6
1887 * Perfect: 2048 31744
1888 * (32*64) (32*31/2 * 64)
1890 #define HASH_MIX(x, y, a) \
1892 y ^= x, x = rol32(x, 7),\
1893 x += y, y = rol32(y,20),\
1896 static inline unsigned int fold_hash(unsigned long x
, unsigned long y
)
1898 /* Use arch-optimized multiply if one exists */
1899 return __hash_32(y
^ __hash_32(x
));
1905 * Return the hash of a string of known length. This is carfully
1906 * designed to match hash_name(), which is the more critical function.
1907 * In particular, we must end by hashing a final word containing 0..7
1908 * payload bytes, to match the way that hash_name() iterates until it
1909 * finds the delimiter after the name.
1911 unsigned int full_name_hash(const void *salt
, const char *name
, unsigned int len
)
1913 unsigned long a
, x
= 0, y
= (unsigned long)salt
;
1918 a
= load_unaligned_zeropad(name
);
1919 if (len
< sizeof(unsigned long))
1922 name
+= sizeof(unsigned long);
1923 len
-= sizeof(unsigned long);
1925 x
^= a
& bytemask_from_count(len
);
1927 return fold_hash(x
, y
);
1929 EXPORT_SYMBOL(full_name_hash
);
1931 /* Return the "hash_len" (hash and length) of a null-terminated string */
1932 u64
hashlen_string(const void *salt
, const char *name
)
1934 unsigned long a
= 0, x
= 0, y
= (unsigned long)salt
;
1935 unsigned long adata
, mask
, len
;
1936 const struct word_at_a_time constants
= WORD_AT_A_TIME_CONSTANTS
;
1943 len
+= sizeof(unsigned long);
1945 a
= load_unaligned_zeropad(name
+len
);
1946 } while (!has_zero(a
, &adata
, &constants
));
1948 adata
= prep_zero_mask(a
, adata
, &constants
);
1949 mask
= create_zero_mask(adata
);
1950 x
^= a
& zero_bytemask(mask
);
1952 return hashlen_create(fold_hash(x
, y
), len
+ find_zero(mask
));
1954 EXPORT_SYMBOL(hashlen_string
);
1957 * Calculate the length and hash of the path component, and
1958 * return the "hash_len" as the result.
1960 static inline u64
hash_name(const void *salt
, const char *name
)
1962 unsigned long a
= 0, b
, x
= 0, y
= (unsigned long)salt
;
1963 unsigned long adata
, bdata
, mask
, len
;
1964 const struct word_at_a_time constants
= WORD_AT_A_TIME_CONSTANTS
;
1971 len
+= sizeof(unsigned long);
1973 a
= load_unaligned_zeropad(name
+len
);
1974 b
= a
^ REPEAT_BYTE('/');
1975 } while (!(has_zero(a
, &adata
, &constants
) | has_zero(b
, &bdata
, &constants
)));
1977 adata
= prep_zero_mask(a
, adata
, &constants
);
1978 bdata
= prep_zero_mask(b
, bdata
, &constants
);
1979 mask
= create_zero_mask(adata
| bdata
);
1980 x
^= a
& zero_bytemask(mask
);
1982 return hashlen_create(fold_hash(x
, y
), len
+ find_zero(mask
));
1985 #else /* !CONFIG_DCACHE_WORD_ACCESS: Slow, byte-at-a-time version */
1987 /* Return the hash of a string of known length */
1988 unsigned int full_name_hash(const void *salt
, const char *name
, unsigned int len
)
1990 unsigned long hash
= init_name_hash(salt
);
1992 hash
= partial_name_hash((unsigned char)*name
++, hash
);
1993 return end_name_hash(hash
);
1995 EXPORT_SYMBOL(full_name_hash
);
1997 /* Return the "hash_len" (hash and length) of a null-terminated string */
1998 u64
hashlen_string(const void *salt
, const char *name
)
2000 unsigned long hash
= init_name_hash(salt
);
2001 unsigned long len
= 0, c
;
2003 c
= (unsigned char)*name
;
2006 hash
= partial_name_hash(c
, hash
);
2007 c
= (unsigned char)name
[len
];
2009 return hashlen_create(end_name_hash(hash
), len
);
2011 EXPORT_SYMBOL(hashlen_string
);
2014 * We know there's a real path component here of at least
2017 static inline u64
hash_name(const void *salt
, const char *name
)
2019 unsigned long hash
= init_name_hash(salt
);
2020 unsigned long len
= 0, c
;
2022 c
= (unsigned char)*name
;
2025 hash
= partial_name_hash(c
, hash
);
2026 c
= (unsigned char)name
[len
];
2027 } while (c
&& c
!= '/');
2028 return hashlen_create(end_name_hash(hash
), len
);
2035 * This is the basic name resolution function, turning a pathname into
2036 * the final dentry. We expect 'base' to be positive and a directory.
2038 * Returns 0 and nd will have valid dentry and mnt on success.
2039 * Returns error and drops reference to input namei data on failure.
2041 static int link_path_walk(const char *name
, struct nameidata
*nd
)
2050 /* At this point we know we have a real path component. */
2055 err
= may_lookup(nd
);
2059 hash_len
= hash_name(nd
->path
.dentry
, name
);
2062 if (name
[0] == '.') switch (hashlen_len(hash_len
)) {
2064 if (name
[1] == '.') {
2066 nd
->flags
|= LOOKUP_JUMPED
;
2072 if (likely(type
== LAST_NORM
)) {
2073 struct dentry
*parent
= nd
->path
.dentry
;
2074 nd
->flags
&= ~LOOKUP_JUMPED
;
2075 if (unlikely(parent
->d_flags
& DCACHE_OP_HASH
)) {
2076 struct qstr
this = { { .hash_len
= hash_len
}, .name
= name
};
2077 err
= parent
->d_op
->d_hash(parent
, &this);
2080 hash_len
= this.hash_len
;
2085 nd
->last
.hash_len
= hash_len
;
2086 nd
->last
.name
= name
;
2087 nd
->last_type
= type
;
2089 name
+= hashlen_len(hash_len
);
2093 * If it wasn't NUL, we know it was '/'. Skip that
2094 * slash, and continue until no more slashes.
2098 } while (unlikely(*name
== '/'));
2099 if (unlikely(!*name
)) {
2101 /* pathname body, done */
2104 name
= nd
->stack
[nd
->depth
- 1].name
;
2105 /* trailing symlink, done */
2108 /* last component of nested symlink */
2109 err
= walk_component(nd
, WALK_FOLLOW
);
2111 /* not the last component */
2112 err
= walk_component(nd
, WALK_FOLLOW
| WALK_MORE
);
2118 const char *s
= get_link(nd
);
2127 nd
->stack
[nd
->depth
- 1].name
= name
;
2132 if (unlikely(!d_can_lookup(nd
->path
.dentry
))) {
2133 if (nd
->flags
& LOOKUP_RCU
) {
2134 if (unlazy_walk(nd
))
2142 static const char *path_init(struct nameidata
*nd
, unsigned flags
)
2144 const char *s
= nd
->name
->name
;
2147 flags
&= ~LOOKUP_RCU
;
2149 nd
->last_type
= LAST_ROOT
; /* if there are only slashes... */
2150 nd
->flags
= flags
| LOOKUP_JUMPED
| LOOKUP_PARENT
;
2152 if (flags
& LOOKUP_ROOT
) {
2153 struct dentry
*root
= nd
->root
.dentry
;
2154 struct inode
*inode
= root
->d_inode
;
2155 if (*s
&& unlikely(!d_can_lookup(root
)))
2156 return ERR_PTR(-ENOTDIR
);
2157 nd
->path
= nd
->root
;
2159 if (flags
& LOOKUP_RCU
) {
2161 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
2162 nd
->root_seq
= nd
->seq
;
2163 nd
->m_seq
= read_seqbegin(&mount_lock
);
2165 path_get(&nd
->path
);
2170 nd
->root
.mnt
= NULL
;
2171 nd
->path
.mnt
= NULL
;
2172 nd
->path
.dentry
= NULL
;
2174 nd
->m_seq
= read_seqbegin(&mount_lock
);
2176 if (flags
& LOOKUP_RCU
)
2179 if (likely(!nd_jump_root(nd
)))
2181 nd
->root
.mnt
= NULL
;
2183 return ERR_PTR(-ECHILD
);
2184 } else if (nd
->dfd
== AT_FDCWD
) {
2185 if (flags
& LOOKUP_RCU
) {
2186 struct fs_struct
*fs
= current
->fs
;
2192 seq
= read_seqcount_begin(&fs
->seq
);
2194 nd
->inode
= nd
->path
.dentry
->d_inode
;
2195 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
2196 } while (read_seqcount_retry(&fs
->seq
, seq
));
2198 get_fs_pwd(current
->fs
, &nd
->path
);
2199 nd
->inode
= nd
->path
.dentry
->d_inode
;
2203 /* Caller must check execute permissions on the starting path component */
2204 struct fd f
= fdget_raw(nd
->dfd
);
2205 struct dentry
*dentry
;
2208 return ERR_PTR(-EBADF
);
2210 dentry
= f
.file
->f_path
.dentry
;
2213 if (!d_can_lookup(dentry
)) {
2215 return ERR_PTR(-ENOTDIR
);
2219 nd
->path
= f
.file
->f_path
;
2220 if (flags
& LOOKUP_RCU
) {
2222 nd
->inode
= nd
->path
.dentry
->d_inode
;
2223 nd
->seq
= read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
2225 path_get(&nd
->path
);
2226 nd
->inode
= nd
->path
.dentry
->d_inode
;
2233 static const char *trailing_symlink(struct nameidata
*nd
)
2236 int error
= may_follow_link(nd
);
2237 if (unlikely(error
))
2238 return ERR_PTR(error
);
2239 nd
->flags
|= LOOKUP_PARENT
;
2240 nd
->stack
[0].name
= NULL
;
2245 static inline int lookup_last(struct nameidata
*nd
)
2247 if (nd
->last_type
== LAST_NORM
&& nd
->last
.name
[nd
->last
.len
])
2248 nd
->flags
|= LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
;
2250 nd
->flags
&= ~LOOKUP_PARENT
;
2251 return walk_component(nd
, 0);
2254 static int handle_lookup_down(struct nameidata
*nd
)
2256 struct path path
= nd
->path
;
2257 struct inode
*inode
= nd
->inode
;
2258 unsigned seq
= nd
->seq
;
2261 if (nd
->flags
& LOOKUP_RCU
) {
2263 * don't bother with unlazy_walk on failure - we are
2264 * at the very beginning of walk, so we lose nothing
2265 * if we simply redo everything in non-RCU mode
2267 if (unlikely(!__follow_mount_rcu(nd
, &path
, &inode
, &seq
)))
2271 err
= follow_managed(&path
, nd
);
2272 if (unlikely(err
< 0))
2274 inode
= d_backing_inode(path
.dentry
);
2277 path_to_nameidata(&path
, nd
);
2283 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
2284 static int path_lookupat(struct nameidata
*nd
, unsigned flags
, struct path
*path
)
2286 const char *s
= path_init(nd
, flags
);
2292 if (unlikely(flags
& LOOKUP_DOWN
)) {
2293 err
= handle_lookup_down(nd
);
2294 if (unlikely(err
< 0)) {
2300 while (!(err
= link_path_walk(s
, nd
))
2301 && ((err
= lookup_last(nd
)) > 0)) {
2302 s
= trailing_symlink(nd
);
2309 err
= complete_walk(nd
);
2311 if (!err
&& nd
->flags
& LOOKUP_DIRECTORY
)
2312 if (!d_can_lookup(nd
->path
.dentry
))
2316 nd
->path
.mnt
= NULL
;
2317 nd
->path
.dentry
= NULL
;
2323 static int filename_lookup(int dfd
, struct filename
*name
, unsigned flags
,
2324 struct path
*path
, struct path
*root
)
2327 struct nameidata nd
;
2329 return PTR_ERR(name
);
2330 if (unlikely(root
)) {
2332 flags
|= LOOKUP_ROOT
;
2334 set_nameidata(&nd
, dfd
, name
);
2335 retval
= path_lookupat(&nd
, flags
| LOOKUP_RCU
, path
);
2336 if (unlikely(retval
== -ECHILD
))
2337 retval
= path_lookupat(&nd
, flags
, path
);
2338 if (unlikely(retval
== -ESTALE
))
2339 retval
= path_lookupat(&nd
, flags
| LOOKUP_REVAL
, path
);
2341 if (likely(!retval
))
2342 audit_inode(name
, path
->dentry
, flags
& LOOKUP_PARENT
);
2343 restore_nameidata();
2348 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
2349 static int path_parentat(struct nameidata
*nd
, unsigned flags
,
2350 struct path
*parent
)
2352 const char *s
= path_init(nd
, flags
);
2356 err
= link_path_walk(s
, nd
);
2358 err
= complete_walk(nd
);
2361 nd
->path
.mnt
= NULL
;
2362 nd
->path
.dentry
= NULL
;
2368 static struct filename
*filename_parentat(int dfd
, struct filename
*name
,
2369 unsigned int flags
, struct path
*parent
,
2370 struct qstr
*last
, int *type
)
2373 struct nameidata nd
;
2377 set_nameidata(&nd
, dfd
, name
);
2378 retval
= path_parentat(&nd
, flags
| LOOKUP_RCU
, parent
);
2379 if (unlikely(retval
== -ECHILD
))
2380 retval
= path_parentat(&nd
, flags
, parent
);
2381 if (unlikely(retval
== -ESTALE
))
2382 retval
= path_parentat(&nd
, flags
| LOOKUP_REVAL
, parent
);
2383 if (likely(!retval
)) {
2385 *type
= nd
.last_type
;
2386 audit_inode(name
, parent
->dentry
, LOOKUP_PARENT
);
2389 name
= ERR_PTR(retval
);
2391 restore_nameidata();
2395 /* does lookup, returns the object with parent locked */
2396 struct dentry
*kern_path_locked(const char *name
, struct path
*path
)
2398 struct filename
*filename
;
2403 filename
= filename_parentat(AT_FDCWD
, getname_kernel(name
), 0, path
,
2405 if (IS_ERR(filename
))
2406 return ERR_CAST(filename
);
2407 if (unlikely(type
!= LAST_NORM
)) {
2410 return ERR_PTR(-EINVAL
);
2412 inode_lock_nested(path
->dentry
->d_inode
, I_MUTEX_PARENT
);
2413 d
= __lookup_hash(&last
, path
->dentry
, 0);
2415 inode_unlock(path
->dentry
->d_inode
);
2422 int kern_path(const char *name
, unsigned int flags
, struct path
*path
)
2424 return filename_lookup(AT_FDCWD
, getname_kernel(name
),
2427 EXPORT_SYMBOL(kern_path
);
2430 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
2431 * @dentry: pointer to dentry of the base directory
2432 * @mnt: pointer to vfs mount of the base directory
2433 * @name: pointer to file name
2434 * @flags: lookup flags
2435 * @path: pointer to struct path to fill
2437 int vfs_path_lookup(struct dentry
*dentry
, struct vfsmount
*mnt
,
2438 const char *name
, unsigned int flags
,
2441 struct path root
= {.mnt
= mnt
, .dentry
= dentry
};
2442 /* the first argument of filename_lookup() is ignored with root */
2443 return filename_lookup(AT_FDCWD
, getname_kernel(name
),
2444 flags
, path
, &root
);
2446 EXPORT_SYMBOL(vfs_path_lookup
);
2449 * lookup_one_len - filesystem helper to lookup single pathname component
2450 * @name: pathname component to lookup
2451 * @base: base directory to lookup from
2452 * @len: maximum length @len should be interpreted to
2454 * Note that this routine is purely a helper for filesystem usage and should
2455 * not be called by generic code.
2457 * The caller must hold base->i_mutex.
2459 struct dentry
*lookup_one_len(const char *name
, struct dentry
*base
, int len
)
2465 WARN_ON_ONCE(!inode_is_locked(base
->d_inode
));
2469 this.hash
= full_name_hash(base
, name
, len
);
2471 return ERR_PTR(-EACCES
);
2473 if (unlikely(name
[0] == '.')) {
2474 if (len
< 2 || (len
== 2 && name
[1] == '.'))
2475 return ERR_PTR(-EACCES
);
2479 c
= *(const unsigned char *)name
++;
2480 if (c
== '/' || c
== '\0')
2481 return ERR_PTR(-EACCES
);
2484 * See if the low-level filesystem might want
2485 * to use its own hash..
2487 if (base
->d_flags
& DCACHE_OP_HASH
) {
2488 int err
= base
->d_op
->d_hash(base
, &this);
2490 return ERR_PTR(err
);
2493 err
= inode_permission(base
->d_inode
, MAY_EXEC
);
2495 return ERR_PTR(err
);
2497 return __lookup_hash(&this, base
, 0);
2499 EXPORT_SYMBOL(lookup_one_len
);
2502 * lookup_one_len_unlocked - filesystem helper to lookup single pathname component
2503 * @name: pathname component to lookup
2504 * @base: base directory to lookup from
2505 * @len: maximum length @len should be interpreted to
2507 * Note that this routine is purely a helper for filesystem usage and should
2508 * not be called by generic code.
2510 * Unlike lookup_one_len, it should be called without the parent
2511 * i_mutex held, and will take the i_mutex itself if necessary.
2513 struct dentry
*lookup_one_len_unlocked(const char *name
,
2514 struct dentry
*base
, int len
)
2523 this.hash
= full_name_hash(base
, name
, len
);
2525 return ERR_PTR(-EACCES
);
2527 if (unlikely(name
[0] == '.')) {
2528 if (len
< 2 || (len
== 2 && name
[1] == '.'))
2529 return ERR_PTR(-EACCES
);
2533 c
= *(const unsigned char *)name
++;
2534 if (c
== '/' || c
== '\0')
2535 return ERR_PTR(-EACCES
);
2538 * See if the low-level filesystem might want
2539 * to use its own hash..
2541 if (base
->d_flags
& DCACHE_OP_HASH
) {
2542 int err
= base
->d_op
->d_hash(base
, &this);
2544 return ERR_PTR(err
);
2547 err
= inode_permission(base
->d_inode
, MAY_EXEC
);
2549 return ERR_PTR(err
);
2551 ret
= lookup_dcache(&this, base
, 0);
2553 ret
= lookup_slow(&this, base
, 0);
2556 EXPORT_SYMBOL(lookup_one_len_unlocked
);
2558 #ifdef CONFIG_UNIX98_PTYS
2559 int path_pts(struct path
*path
)
2561 /* Find something mounted on "pts" in the same directory as
2564 struct dentry
*child
, *parent
;
2568 ret
= path_parent_directory(path
);
2572 parent
= path
->dentry
;
2575 child
= d_hash_and_lookup(parent
, &this);
2579 path
->dentry
= child
;
2586 int user_path_at_empty(int dfd
, const char __user
*name
, unsigned flags
,
2587 struct path
*path
, int *empty
)
2589 return filename_lookup(dfd
, getname_flags(name
, flags
, empty
),
2592 EXPORT_SYMBOL(user_path_at_empty
);
2595 * mountpoint_last - look up last component for umount
2596 * @nd: pathwalk nameidata - currently pointing at parent directory of "last"
2598 * This is a special lookup_last function just for umount. In this case, we
2599 * need to resolve the path without doing any revalidation.
2601 * The nameidata should be the result of doing a LOOKUP_PARENT pathwalk. Since
2602 * mountpoints are always pinned in the dcache, their ancestors are too. Thus,
2603 * in almost all cases, this lookup will be served out of the dcache. The only
2604 * cases where it won't are if nd->last refers to a symlink or the path is
2605 * bogus and it doesn't exist.
2608 * -error: if there was an error during lookup. This includes -ENOENT if the
2609 * lookup found a negative dentry.
2611 * 0: if we successfully resolved nd->last and found it to not to be a
2612 * symlink that needs to be followed.
2614 * 1: if we successfully resolved nd->last and found it to be a symlink
2615 * that needs to be followed.
2618 mountpoint_last(struct nameidata
*nd
)
2621 struct dentry
*dir
= nd
->path
.dentry
;
2624 /* If we're in rcuwalk, drop out of it to handle last component */
2625 if (nd
->flags
& LOOKUP_RCU
) {
2626 if (unlazy_walk(nd
))
2630 nd
->flags
&= ~LOOKUP_PARENT
;
2632 if (unlikely(nd
->last_type
!= LAST_NORM
)) {
2633 error
= handle_dots(nd
, nd
->last_type
);
2636 path
.dentry
= dget(nd
->path
.dentry
);
2638 path
.dentry
= d_lookup(dir
, &nd
->last
);
2641 * No cached dentry. Mounted dentries are pinned in the
2642 * cache, so that means that this dentry is probably
2643 * a symlink or the path doesn't actually point
2644 * to a mounted dentry.
2646 path
.dentry
= lookup_slow(&nd
->last
, dir
,
2647 nd
->flags
| LOOKUP_NO_REVAL
);
2648 if (IS_ERR(path
.dentry
))
2649 return PTR_ERR(path
.dentry
);
2652 if (d_is_negative(path
.dentry
)) {
2656 path
.mnt
= nd
->path
.mnt
;
2657 return step_into(nd
, &path
, 0, d_backing_inode(path
.dentry
), 0);
2661 * path_mountpoint - look up a path to be umounted
2662 * @nd: lookup context
2663 * @flags: lookup flags
2664 * @path: pointer to container for result
2666 * Look up the given name, but don't attempt to revalidate the last component.
2667 * Returns 0 and "path" will be valid on success; Returns error otherwise.
2670 path_mountpoint(struct nameidata
*nd
, unsigned flags
, struct path
*path
)
2672 const char *s
= path_init(nd
, flags
);
2676 while (!(err
= link_path_walk(s
, nd
)) &&
2677 (err
= mountpoint_last(nd
)) > 0) {
2678 s
= trailing_symlink(nd
);
2686 nd
->path
.mnt
= NULL
;
2687 nd
->path
.dentry
= NULL
;
2695 filename_mountpoint(int dfd
, struct filename
*name
, struct path
*path
,
2698 struct nameidata nd
;
2701 return PTR_ERR(name
);
2702 set_nameidata(&nd
, dfd
, name
);
2703 error
= path_mountpoint(&nd
, flags
| LOOKUP_RCU
, path
);
2704 if (unlikely(error
== -ECHILD
))
2705 error
= path_mountpoint(&nd
, flags
, path
);
2706 if (unlikely(error
== -ESTALE
))
2707 error
= path_mountpoint(&nd
, flags
| LOOKUP_REVAL
, path
);
2709 audit_inode(name
, path
->dentry
, 0);
2710 restore_nameidata();
2716 * user_path_mountpoint_at - lookup a path from userland in order to umount it
2717 * @dfd: directory file descriptor
2718 * @name: pathname from userland
2719 * @flags: lookup flags
2720 * @path: pointer to container to hold result
2722 * A umount is a special case for path walking. We're not actually interested
2723 * in the inode in this situation, and ESTALE errors can be a problem. We
2724 * simply want track down the dentry and vfsmount attached at the mountpoint
2725 * and avoid revalidating the last component.
2727 * Returns 0 and populates "path" on success.
2730 user_path_mountpoint_at(int dfd
, const char __user
*name
, unsigned int flags
,
2733 return filename_mountpoint(dfd
, getname(name
), path
, flags
);
2737 kern_path_mountpoint(int dfd
, const char *name
, struct path
*path
,
2740 return filename_mountpoint(dfd
, getname_kernel(name
), path
, flags
);
2742 EXPORT_SYMBOL(kern_path_mountpoint
);
2744 int __check_sticky(struct inode
*dir
, struct inode
*inode
)
2746 kuid_t fsuid
= current_fsuid();
2748 if (uid_eq(inode
->i_uid
, fsuid
))
2750 if (uid_eq(dir
->i_uid
, fsuid
))
2752 return !capable_wrt_inode_uidgid(inode
, CAP_FOWNER
);
2754 EXPORT_SYMBOL(__check_sticky
);
2757 * Check whether we can remove a link victim from directory dir, check
2758 * whether the type of victim is right.
2759 * 1. We can't do it if dir is read-only (done in permission())
2760 * 2. We should have write and exec permissions on dir
2761 * 3. We can't remove anything from append-only dir
2762 * 4. We can't do anything with immutable dir (done in permission())
2763 * 5. If the sticky bit on dir is set we should either
2764 * a. be owner of dir, or
2765 * b. be owner of victim, or
2766 * c. have CAP_FOWNER capability
2767 * 6. If the victim is append-only or immutable we can't do antyhing with
2768 * links pointing to it.
2769 * 7. If the victim has an unknown uid or gid we can't change the inode.
2770 * 8. If we were asked to remove a directory and victim isn't one - ENOTDIR.
2771 * 9. If we were asked to remove a non-directory and victim isn't one - EISDIR.
2772 * 10. We can't remove a root or mountpoint.
2773 * 11. We don't allow removal of NFS sillyrenamed files; it's handled by
2774 * nfs_async_unlink().
2776 static int may_delete(struct inode
*dir
, struct dentry
*victim
, bool isdir
)
2778 struct inode
*inode
= d_backing_inode(victim
);
2781 if (d_is_negative(victim
))
2785 BUG_ON(victim
->d_parent
->d_inode
!= dir
);
2786 audit_inode_child(dir
, victim
, AUDIT_TYPE_CHILD_DELETE
);
2788 error
= inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
2794 if (check_sticky(dir
, inode
) || IS_APPEND(inode
) ||
2795 IS_IMMUTABLE(inode
) || IS_SWAPFILE(inode
) || HAS_UNMAPPED_ID(inode
))
2798 if (!d_is_dir(victim
))
2800 if (IS_ROOT(victim
))
2802 } else if (d_is_dir(victim
))
2804 if (IS_DEADDIR(dir
))
2806 if (victim
->d_flags
& DCACHE_NFSFS_RENAMED
)
2811 /* Check whether we can create an object with dentry child in directory
2813 * 1. We can't do it if child already exists (open has special treatment for
2814 * this case, but since we are inlined it's OK)
2815 * 2. We can't do it if dir is read-only (done in permission())
2816 * 3. We can't do it if the fs can't represent the fsuid or fsgid.
2817 * 4. We should have write and exec permissions on dir
2818 * 5. We can't do it if dir is immutable (done in permission())
2820 static inline int may_create(struct inode
*dir
, struct dentry
*child
)
2822 struct user_namespace
*s_user_ns
;
2823 audit_inode_child(dir
, child
, AUDIT_TYPE_CHILD_CREATE
);
2826 if (IS_DEADDIR(dir
))
2828 s_user_ns
= dir
->i_sb
->s_user_ns
;
2829 if (!kuid_has_mapping(s_user_ns
, current_fsuid()) ||
2830 !kgid_has_mapping(s_user_ns
, current_fsgid()))
2832 return inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
2836 * p1 and p2 should be directories on the same fs.
2838 struct dentry
*lock_rename(struct dentry
*p1
, struct dentry
*p2
)
2843 inode_lock_nested(p1
->d_inode
, I_MUTEX_PARENT
);
2847 mutex_lock(&p1
->d_sb
->s_vfs_rename_mutex
);
2849 p
= d_ancestor(p2
, p1
);
2851 inode_lock_nested(p2
->d_inode
, I_MUTEX_PARENT
);
2852 inode_lock_nested(p1
->d_inode
, I_MUTEX_CHILD
);
2856 p
= d_ancestor(p1
, p2
);
2858 inode_lock_nested(p1
->d_inode
, I_MUTEX_PARENT
);
2859 inode_lock_nested(p2
->d_inode
, I_MUTEX_CHILD
);
2863 inode_lock_nested(p1
->d_inode
, I_MUTEX_PARENT
);
2864 inode_lock_nested(p2
->d_inode
, I_MUTEX_PARENT2
);
2867 EXPORT_SYMBOL(lock_rename
);
2869 void unlock_rename(struct dentry
*p1
, struct dentry
*p2
)
2871 inode_unlock(p1
->d_inode
);
2873 inode_unlock(p2
->d_inode
);
2874 mutex_unlock(&p1
->d_sb
->s_vfs_rename_mutex
);
2877 EXPORT_SYMBOL(unlock_rename
);
2879 int vfs_create(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
,
2882 int error
= may_create(dir
, dentry
);
2886 if (!dir
->i_op
->create
)
2887 return -EACCES
; /* shouldn't it be ENOSYS? */
2890 error
= security_inode_create(dir
, dentry
, mode
);
2893 error
= dir
->i_op
->create(dir
, dentry
, mode
, want_excl
);
2895 fsnotify_create(dir
, dentry
);
2898 EXPORT_SYMBOL(vfs_create
);
2900 bool may_open_dev(const struct path
*path
)
2902 return !(path
->mnt
->mnt_flags
& MNT_NODEV
) &&
2903 !(path
->mnt
->mnt_sb
->s_iflags
& SB_I_NODEV
);
2906 static int may_open(const struct path
*path
, int acc_mode
, int flag
)
2908 struct dentry
*dentry
= path
->dentry
;
2909 struct inode
*inode
= dentry
->d_inode
;
2915 switch (inode
->i_mode
& S_IFMT
) {
2919 if (acc_mode
& MAY_WRITE
)
2924 if (!may_open_dev(path
))
2933 error
= inode_permission(inode
, MAY_OPEN
| acc_mode
);
2938 * An append-only file must be opened in append mode for writing.
2940 if (IS_APPEND(inode
)) {
2941 if ((flag
& O_ACCMODE
) != O_RDONLY
&& !(flag
& O_APPEND
))
2947 /* O_NOATIME can only be set by the owner or superuser */
2948 if (flag
& O_NOATIME
&& !inode_owner_or_capable(inode
))
2954 static int handle_truncate(struct file
*filp
)
2956 const struct path
*path
= &filp
->f_path
;
2957 struct inode
*inode
= path
->dentry
->d_inode
;
2958 int error
= get_write_access(inode
);
2962 * Refuse to truncate files with mandatory locks held on them.
2964 error
= locks_verify_locked(filp
);
2966 error
= security_path_truncate(path
);
2968 error
= do_truncate(path
->dentry
, 0,
2969 ATTR_MTIME
|ATTR_CTIME
|ATTR_OPEN
,
2972 put_write_access(inode
);
2976 static inline int open_to_namei_flags(int flag
)
2978 if ((flag
& O_ACCMODE
) == 3)
2983 static int may_o_create(const struct path
*dir
, struct dentry
*dentry
, umode_t mode
)
2985 struct user_namespace
*s_user_ns
;
2986 int error
= security_path_mknod(dir
, dentry
, mode
, 0);
2990 s_user_ns
= dir
->dentry
->d_sb
->s_user_ns
;
2991 if (!kuid_has_mapping(s_user_ns
, current_fsuid()) ||
2992 !kgid_has_mapping(s_user_ns
, current_fsgid()))
2995 error
= inode_permission(dir
->dentry
->d_inode
, MAY_WRITE
| MAY_EXEC
);
2999 return security_inode_create(dir
->dentry
->d_inode
, dentry
, mode
);
3003 * Attempt to atomically look up, create and open a file from a negative
3006 * Returns 0 if successful. The file will have been created and attached to
3007 * @file by the filesystem calling finish_open().
3009 * Returns 1 if the file was looked up only or didn't need creating. The
3010 * caller will need to perform the open themselves. @path will have been
3011 * updated to point to the new dentry. This may be negative.
3013 * Returns an error code otherwise.
3015 static int atomic_open(struct nameidata
*nd
, struct dentry
*dentry
,
3016 struct path
*path
, struct file
*file
,
3017 const struct open_flags
*op
,
3018 int open_flag
, umode_t mode
,
3021 struct dentry
*const DENTRY_NOT_SET
= (void *) -1UL;
3022 struct inode
*dir
= nd
->path
.dentry
->d_inode
;
3025 if (!(~open_flag
& (O_EXCL
| O_CREAT
))) /* both O_EXCL and O_CREAT */
3026 open_flag
&= ~O_TRUNC
;
3028 if (nd
->flags
& LOOKUP_DIRECTORY
)
3029 open_flag
|= O_DIRECTORY
;
3031 file
->f_path
.dentry
= DENTRY_NOT_SET
;
3032 file
->f_path
.mnt
= nd
->path
.mnt
;
3033 error
= dir
->i_op
->atomic_open(dir
, dentry
, file
,
3034 open_to_namei_flags(open_flag
),
3036 d_lookup_done(dentry
);
3039 * We didn't have the inode before the open, so check open
3042 int acc_mode
= op
->acc_mode
;
3043 if (*opened
& FILE_CREATED
) {
3044 WARN_ON(!(open_flag
& O_CREAT
));
3045 fsnotify_create(dir
, dentry
);
3048 error
= may_open(&file
->f_path
, acc_mode
, open_flag
);
3049 if (WARN_ON(error
> 0))
3051 } else if (error
> 0) {
3052 if (WARN_ON(file
->f_path
.dentry
== DENTRY_NOT_SET
)) {
3055 if (file
->f_path
.dentry
) {
3057 dentry
= file
->f_path
.dentry
;
3059 if (*opened
& FILE_CREATED
)
3060 fsnotify_create(dir
, dentry
);
3061 if (unlikely(d_is_negative(dentry
))) {
3064 path
->dentry
= dentry
;
3065 path
->mnt
= nd
->path
.mnt
;
3075 * Look up and maybe create and open the last component.
3077 * Must be called with i_mutex held on parent.
3079 * Returns 0 if the file was successfully atomically created (if necessary) and
3080 * opened. In this case the file will be returned attached to @file.
3082 * Returns 1 if the file was not completely opened at this time, though lookups
3083 * and creations will have been performed and the dentry returned in @path will
3084 * be positive upon return if O_CREAT was specified. If O_CREAT wasn't
3085 * specified then a negative dentry may be returned.
3087 * An error code is returned otherwise.
3089 * FILE_CREATE will be set in @*opened if the dentry was created and will be
3090 * cleared otherwise prior to returning.
3092 static int lookup_open(struct nameidata
*nd
, struct path
*path
,
3094 const struct open_flags
*op
,
3095 bool got_write
, int *opened
)
3097 struct dentry
*dir
= nd
->path
.dentry
;
3098 struct inode
*dir_inode
= dir
->d_inode
;
3099 int open_flag
= op
->open_flag
;
3100 struct dentry
*dentry
;
3101 int error
, create_error
= 0;
3102 umode_t mode
= op
->mode
;
3103 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq
);
3105 if (unlikely(IS_DEADDIR(dir_inode
)))
3108 *opened
&= ~FILE_CREATED
;
3109 dentry
= d_lookup(dir
, &nd
->last
);
3112 dentry
= d_alloc_parallel(dir
, &nd
->last
, &wq
);
3114 return PTR_ERR(dentry
);
3116 if (d_in_lookup(dentry
))
3119 error
= d_revalidate(dentry
, nd
->flags
);
3120 if (likely(error
> 0))
3124 d_invalidate(dentry
);
3128 if (dentry
->d_inode
) {
3129 /* Cached positive dentry: will open in f_op->open */
3134 * Checking write permission is tricky, bacuse we don't know if we are
3135 * going to actually need it: O_CREAT opens should work as long as the
3136 * file exists. But checking existence breaks atomicity. The trick is
3137 * to check access and if not granted clear O_CREAT from the flags.
3139 * Another problem is returing the "right" error value (e.g. for an
3140 * O_EXCL open we want to return EEXIST not EROFS).
3142 if (open_flag
& O_CREAT
) {
3143 if (!IS_POSIXACL(dir
->d_inode
))
3144 mode
&= ~current_umask();
3145 if (unlikely(!got_write
)) {
3146 create_error
= -EROFS
;
3147 open_flag
&= ~O_CREAT
;
3148 if (open_flag
& (O_EXCL
| O_TRUNC
))
3150 /* No side effects, safe to clear O_CREAT */
3152 create_error
= may_o_create(&nd
->path
, dentry
, mode
);
3154 open_flag
&= ~O_CREAT
;
3155 if (open_flag
& O_EXCL
)
3159 } else if ((open_flag
& (O_TRUNC
|O_WRONLY
|O_RDWR
)) &&
3160 unlikely(!got_write
)) {
3162 * No O_CREATE -> atomicity not a requirement -> fall
3163 * back to lookup + open
3168 if (dir_inode
->i_op
->atomic_open
) {
3169 error
= atomic_open(nd
, dentry
, path
, file
, op
, open_flag
,
3171 if (unlikely(error
== -ENOENT
) && create_error
)
3172 error
= create_error
;
3177 if (d_in_lookup(dentry
)) {
3178 struct dentry
*res
= dir_inode
->i_op
->lookup(dir_inode
, dentry
,
3180 d_lookup_done(dentry
);
3181 if (unlikely(res
)) {
3183 error
= PTR_ERR(res
);
3191 /* Negative dentry, just create the file */
3192 if (!dentry
->d_inode
&& (open_flag
& O_CREAT
)) {
3193 *opened
|= FILE_CREATED
;
3194 audit_inode_child(dir_inode
, dentry
, AUDIT_TYPE_CHILD_CREATE
);
3195 if (!dir_inode
->i_op
->create
) {
3199 error
= dir_inode
->i_op
->create(dir_inode
, dentry
, mode
,
3200 open_flag
& O_EXCL
);
3203 fsnotify_create(dir_inode
, dentry
);
3205 if (unlikely(create_error
) && !dentry
->d_inode
) {
3206 error
= create_error
;
3210 path
->dentry
= dentry
;
3211 path
->mnt
= nd
->path
.mnt
;
3220 * Handle the last step of open()
3222 static int do_last(struct nameidata
*nd
,
3223 struct file
*file
, const struct open_flags
*op
,
3226 struct dentry
*dir
= nd
->path
.dentry
;
3227 int open_flag
= op
->open_flag
;
3228 bool will_truncate
= (open_flag
& O_TRUNC
) != 0;
3229 bool got_write
= false;
3230 int acc_mode
= op
->acc_mode
;
3232 struct inode
*inode
;
3236 nd
->flags
&= ~LOOKUP_PARENT
;
3237 nd
->flags
|= op
->intent
;
3239 if (nd
->last_type
!= LAST_NORM
) {
3240 error
= handle_dots(nd
, nd
->last_type
);
3241 if (unlikely(error
))
3246 if (!(open_flag
& O_CREAT
)) {
3247 if (nd
->last
.name
[nd
->last
.len
])
3248 nd
->flags
|= LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
;
3249 /* we _can_ be in RCU mode here */
3250 error
= lookup_fast(nd
, &path
, &inode
, &seq
);
3251 if (likely(error
> 0))
3257 BUG_ON(nd
->inode
!= dir
->d_inode
);
3258 BUG_ON(nd
->flags
& LOOKUP_RCU
);
3260 /* create side of things */
3262 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED
3263 * has been cleared when we got to the last component we are
3266 error
= complete_walk(nd
);
3270 audit_inode(nd
->name
, dir
, LOOKUP_PARENT
);
3271 /* trailing slashes? */
3272 if (unlikely(nd
->last
.name
[nd
->last
.len
]))
3276 if (open_flag
& (O_CREAT
| O_TRUNC
| O_WRONLY
| O_RDWR
)) {
3277 error
= mnt_want_write(nd
->path
.mnt
);
3281 * do _not_ fail yet - we might not need that or fail with
3282 * a different error; let lookup_open() decide; we'll be
3283 * dropping this one anyway.
3286 if (open_flag
& O_CREAT
)
3287 inode_lock(dir
->d_inode
);
3289 inode_lock_shared(dir
->d_inode
);
3290 error
= lookup_open(nd
, &path
, file
, op
, got_write
, opened
);
3291 if (open_flag
& O_CREAT
)
3292 inode_unlock(dir
->d_inode
);
3294 inode_unlock_shared(dir
->d_inode
);
3300 if ((*opened
& FILE_CREATED
) ||
3301 !S_ISREG(file_inode(file
)->i_mode
))
3302 will_truncate
= false;
3304 audit_inode(nd
->name
, file
->f_path
.dentry
, 0);
3308 if (*opened
& FILE_CREATED
) {
3309 /* Don't check for write permission, don't truncate */
3310 open_flag
&= ~O_TRUNC
;
3311 will_truncate
= false;
3313 path_to_nameidata(&path
, nd
);
3314 goto finish_open_created
;
3318 * If atomic_open() acquired write access it is dropped now due to
3319 * possible mount and symlink following (this might be optimized away if
3323 mnt_drop_write(nd
->path
.mnt
);
3327 error
= follow_managed(&path
, nd
);
3328 if (unlikely(error
< 0))
3331 if (unlikely(d_is_negative(path
.dentry
))) {
3332 path_to_nameidata(&path
, nd
);
3337 * create/update audit record if it already exists.
3339 audit_inode(nd
->name
, path
.dentry
, 0);
3341 if (unlikely((open_flag
& (O_EXCL
| O_CREAT
)) == (O_EXCL
| O_CREAT
))) {
3342 path_to_nameidata(&path
, nd
);
3346 seq
= 0; /* out of RCU mode, so the value doesn't matter */
3347 inode
= d_backing_inode(path
.dentry
);
3349 error
= step_into(nd
, &path
, 0, inode
, seq
);
3350 if (unlikely(error
))
3353 /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
3354 error
= complete_walk(nd
);
3357 audit_inode(nd
->name
, nd
->path
.dentry
, 0);
3359 if ((open_flag
& O_CREAT
) && d_is_dir(nd
->path
.dentry
))
3362 if ((nd
->flags
& LOOKUP_DIRECTORY
) && !d_can_lookup(nd
->path
.dentry
))
3364 if (!d_is_reg(nd
->path
.dentry
))
3365 will_truncate
= false;
3367 if (will_truncate
) {
3368 error
= mnt_want_write(nd
->path
.mnt
);
3373 finish_open_created
:
3374 error
= may_open(&nd
->path
, acc_mode
, open_flag
);
3377 BUG_ON(*opened
& FILE_OPENED
); /* once it's opened, it's opened */
3378 error
= vfs_open(&nd
->path
, file
, current_cred());
3381 *opened
|= FILE_OPENED
;
3383 error
= open_check_o_direct(file
);
3385 error
= ima_file_check(file
, op
->acc_mode
, *opened
);
3386 if (!error
&& will_truncate
)
3387 error
= handle_truncate(file
);
3389 if (unlikely(error
) && (*opened
& FILE_OPENED
))
3391 if (unlikely(error
> 0)) {
3396 mnt_drop_write(nd
->path
.mnt
);
3400 struct dentry
*vfs_tmpfile(struct dentry
*dentry
, umode_t mode
, int open_flag
)
3402 struct dentry
*child
= NULL
;
3403 struct inode
*dir
= dentry
->d_inode
;
3404 struct inode
*inode
;
3407 /* we want directory to be writable */
3408 error
= inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
3411 error
= -EOPNOTSUPP
;
3412 if (!dir
->i_op
->tmpfile
)
3415 child
= d_alloc(dentry
, &slash_name
);
3416 if (unlikely(!child
))
3418 error
= dir
->i_op
->tmpfile(dir
, child
, mode
);
3422 inode
= child
->d_inode
;
3423 if (unlikely(!inode
))
3425 if (!(open_flag
& O_EXCL
)) {
3426 spin_lock(&inode
->i_lock
);
3427 inode
->i_state
|= I_LINKABLE
;
3428 spin_unlock(&inode
->i_lock
);
3434 return ERR_PTR(error
);
3436 EXPORT_SYMBOL(vfs_tmpfile
);
3438 static int do_tmpfile(struct nameidata
*nd
, unsigned flags
,
3439 const struct open_flags
*op
,
3440 struct file
*file
, int *opened
)
3442 struct dentry
*child
;
3444 int error
= path_lookupat(nd
, flags
| LOOKUP_DIRECTORY
, &path
);
3445 if (unlikely(error
))
3447 error
= mnt_want_write(path
.mnt
);
3448 if (unlikely(error
))
3450 child
= vfs_tmpfile(path
.dentry
, op
->mode
, op
->open_flag
);
3451 error
= PTR_ERR(child
);
3455 path
.dentry
= child
;
3456 audit_inode(nd
->name
, child
, 0);
3457 /* Don't check for other permissions, the inode was just created */
3458 error
= may_open(&path
, 0, op
->open_flag
);
3461 file
->f_path
.mnt
= path
.mnt
;
3462 error
= finish_open(file
, child
, NULL
, opened
);
3465 error
= open_check_o_direct(file
);
3469 mnt_drop_write(path
.mnt
);
3475 static int do_o_path(struct nameidata
*nd
, unsigned flags
, struct file
*file
)
3478 int error
= path_lookupat(nd
, flags
, &path
);
3480 audit_inode(nd
->name
, path
.dentry
, 0);
3481 error
= vfs_open(&path
, file
, current_cred());
3487 static struct file
*path_openat(struct nameidata
*nd
,
3488 const struct open_flags
*op
, unsigned flags
)
3495 file
= get_empty_filp();
3499 file
->f_flags
= op
->open_flag
;
3501 if (unlikely(file
->f_flags
& __O_TMPFILE
)) {
3502 error
= do_tmpfile(nd
, flags
, op
, file
, &opened
);
3506 if (unlikely(file
->f_flags
& O_PATH
)) {
3507 error
= do_o_path(nd
, flags
, file
);
3509 opened
|= FILE_OPENED
;
3513 s
= path_init(nd
, flags
);
3518 while (!(error
= link_path_walk(s
, nd
)) &&
3519 (error
= do_last(nd
, file
, op
, &opened
)) > 0) {
3520 nd
->flags
&= ~(LOOKUP_OPEN
|LOOKUP_CREATE
|LOOKUP_EXCL
);
3521 s
= trailing_symlink(nd
);
3529 if (!(opened
& FILE_OPENED
)) {
3533 if (unlikely(error
)) {
3534 if (error
== -EOPENSTALE
) {
3535 if (flags
& LOOKUP_RCU
)
3540 file
= ERR_PTR(error
);
3545 struct file
*do_filp_open(int dfd
, struct filename
*pathname
,
3546 const struct open_flags
*op
)
3548 struct nameidata nd
;
3549 int flags
= op
->lookup_flags
;
3552 set_nameidata(&nd
, dfd
, pathname
);
3553 filp
= path_openat(&nd
, op
, flags
| LOOKUP_RCU
);
3554 if (unlikely(filp
== ERR_PTR(-ECHILD
)))
3555 filp
= path_openat(&nd
, op
, flags
);
3556 if (unlikely(filp
== ERR_PTR(-ESTALE
)))
3557 filp
= path_openat(&nd
, op
, flags
| LOOKUP_REVAL
);
3558 restore_nameidata();
3562 struct file
*do_file_open_root(struct dentry
*dentry
, struct vfsmount
*mnt
,
3563 const char *name
, const struct open_flags
*op
)
3565 struct nameidata nd
;
3567 struct filename
*filename
;
3568 int flags
= op
->lookup_flags
| LOOKUP_ROOT
;
3571 nd
.root
.dentry
= dentry
;
3573 if (d_is_symlink(dentry
) && op
->intent
& LOOKUP_OPEN
)
3574 return ERR_PTR(-ELOOP
);
3576 filename
= getname_kernel(name
);
3577 if (IS_ERR(filename
))
3578 return ERR_CAST(filename
);
3580 set_nameidata(&nd
, -1, filename
);
3581 file
= path_openat(&nd
, op
, flags
| LOOKUP_RCU
);
3582 if (unlikely(file
== ERR_PTR(-ECHILD
)))
3583 file
= path_openat(&nd
, op
, flags
);
3584 if (unlikely(file
== ERR_PTR(-ESTALE
)))
3585 file
= path_openat(&nd
, op
, flags
| LOOKUP_REVAL
);
3586 restore_nameidata();
3591 static struct dentry
*filename_create(int dfd
, struct filename
*name
,
3592 struct path
*path
, unsigned int lookup_flags
)
3594 struct dentry
*dentry
= ERR_PTR(-EEXIST
);
3599 bool is_dir
= (lookup_flags
& LOOKUP_DIRECTORY
);
3602 * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any
3603 * other flags passed in are ignored!
3605 lookup_flags
&= LOOKUP_REVAL
;
3607 name
= filename_parentat(dfd
, name
, lookup_flags
, path
, &last
, &type
);
3609 return ERR_CAST(name
);
3612 * Yucky last component or no last component at all?
3613 * (foo/., foo/.., /////)
3615 if (unlikely(type
!= LAST_NORM
))
3618 /* don't fail immediately if it's r/o, at least try to report other errors */
3619 err2
= mnt_want_write(path
->mnt
);
3621 * Do the final lookup.
3623 lookup_flags
|= LOOKUP_CREATE
| LOOKUP_EXCL
;
3624 inode_lock_nested(path
->dentry
->d_inode
, I_MUTEX_PARENT
);
3625 dentry
= __lookup_hash(&last
, path
->dentry
, lookup_flags
);
3630 if (d_is_positive(dentry
))
3634 * Special case - lookup gave negative, but... we had foo/bar/
3635 * From the vfs_mknod() POV we just have a negative dentry -
3636 * all is fine. Let's be bastards - you had / on the end, you've
3637 * been asking for (non-existent) directory. -ENOENT for you.
3639 if (unlikely(!is_dir
&& last
.name
[last
.len
])) {
3643 if (unlikely(err2
)) {
3651 dentry
= ERR_PTR(error
);
3653 inode_unlock(path
->dentry
->d_inode
);
3655 mnt_drop_write(path
->mnt
);
3662 struct dentry
*kern_path_create(int dfd
, const char *pathname
,
3663 struct path
*path
, unsigned int lookup_flags
)
3665 return filename_create(dfd
, getname_kernel(pathname
),
3666 path
, lookup_flags
);
3668 EXPORT_SYMBOL(kern_path_create
);
3670 void done_path_create(struct path
*path
, struct dentry
*dentry
)
3673 inode_unlock(path
->dentry
->d_inode
);
3674 mnt_drop_write(path
->mnt
);
3677 EXPORT_SYMBOL(done_path_create
);
3679 inline struct dentry
*user_path_create(int dfd
, const char __user
*pathname
,
3680 struct path
*path
, unsigned int lookup_flags
)
3682 return filename_create(dfd
, getname(pathname
), path
, lookup_flags
);
3684 EXPORT_SYMBOL(user_path_create
);
3686 int vfs_mknod(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
, dev_t dev
)
3688 int error
= may_create(dir
, dentry
);
3693 if ((S_ISCHR(mode
) || S_ISBLK(mode
)) && !capable(CAP_MKNOD
))
3696 if (!dir
->i_op
->mknod
)
3699 error
= devcgroup_inode_mknod(mode
, dev
);
3703 error
= security_inode_mknod(dir
, dentry
, mode
, dev
);
3707 error
= dir
->i_op
->mknod(dir
, dentry
, mode
, dev
);
3709 fsnotify_create(dir
, dentry
);
3712 EXPORT_SYMBOL(vfs_mknod
);
3714 static int may_mknod(umode_t mode
)
3716 switch (mode
& S_IFMT
) {
3722 case 0: /* zero mode translates to S_IFREG */
3731 SYSCALL_DEFINE4(mknodat
, int, dfd
, const char __user
*, filename
, umode_t
, mode
,
3734 struct dentry
*dentry
;
3737 unsigned int lookup_flags
= 0;
3739 error
= may_mknod(mode
);
3743 dentry
= user_path_create(dfd
, filename
, &path
, lookup_flags
);
3745 return PTR_ERR(dentry
);
3747 if (!IS_POSIXACL(path
.dentry
->d_inode
))
3748 mode
&= ~current_umask();
3749 error
= security_path_mknod(&path
, dentry
, mode
, dev
);
3752 switch (mode
& S_IFMT
) {
3753 case 0: case S_IFREG
:
3754 error
= vfs_create(path
.dentry
->d_inode
,dentry
,mode
,true);
3756 ima_post_path_mknod(dentry
);
3758 case S_IFCHR
: case S_IFBLK
:
3759 error
= vfs_mknod(path
.dentry
->d_inode
,dentry
,mode
,
3760 new_decode_dev(dev
));
3762 case S_IFIFO
: case S_IFSOCK
:
3763 error
= vfs_mknod(path
.dentry
->d_inode
,dentry
,mode
,0);
3767 done_path_create(&path
, dentry
);
3768 if (retry_estale(error
, lookup_flags
)) {
3769 lookup_flags
|= LOOKUP_REVAL
;
3775 SYSCALL_DEFINE3(mknod
, const char __user
*, filename
, umode_t
, mode
, unsigned, dev
)
3777 return sys_mknodat(AT_FDCWD
, filename
, mode
, dev
);
3780 int vfs_mkdir(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
)
3782 int error
= may_create(dir
, dentry
);
3783 unsigned max_links
= dir
->i_sb
->s_max_links
;
3788 if (!dir
->i_op
->mkdir
)
3791 mode
&= (S_IRWXUGO
|S_ISVTX
);
3792 error
= security_inode_mkdir(dir
, dentry
, mode
);
3796 if (max_links
&& dir
->i_nlink
>= max_links
)
3799 error
= dir
->i_op
->mkdir(dir
, dentry
, mode
);
3801 fsnotify_mkdir(dir
, dentry
);
3804 EXPORT_SYMBOL(vfs_mkdir
);
3806 SYSCALL_DEFINE3(mkdirat
, int, dfd
, const char __user
*, pathname
, umode_t
, mode
)
3808 struct dentry
*dentry
;
3811 unsigned int lookup_flags
= LOOKUP_DIRECTORY
;
3814 dentry
= user_path_create(dfd
, pathname
, &path
, lookup_flags
);
3816 return PTR_ERR(dentry
);
3818 if (!IS_POSIXACL(path
.dentry
->d_inode
))
3819 mode
&= ~current_umask();
3820 error
= security_path_mkdir(&path
, dentry
, mode
);
3822 error
= vfs_mkdir(path
.dentry
->d_inode
, dentry
, mode
);
3823 done_path_create(&path
, dentry
);
3824 if (retry_estale(error
, lookup_flags
)) {
3825 lookup_flags
|= LOOKUP_REVAL
;
3831 SYSCALL_DEFINE2(mkdir
, const char __user
*, pathname
, umode_t
, mode
)
3833 return sys_mkdirat(AT_FDCWD
, pathname
, mode
);
3836 int vfs_rmdir(struct inode
*dir
, struct dentry
*dentry
)
3838 int error
= may_delete(dir
, dentry
, 1);
3843 if (!dir
->i_op
->rmdir
)
3847 inode_lock(dentry
->d_inode
);
3850 if (is_local_mountpoint(dentry
))
3853 error
= security_inode_rmdir(dir
, dentry
);
3857 shrink_dcache_parent(dentry
);
3858 error
= dir
->i_op
->rmdir(dir
, dentry
);
3862 dentry
->d_inode
->i_flags
|= S_DEAD
;
3864 detach_mounts(dentry
);
3867 inode_unlock(dentry
->d_inode
);
3873 EXPORT_SYMBOL(vfs_rmdir
);
3875 static long do_rmdir(int dfd
, const char __user
*pathname
)
3878 struct filename
*name
;
3879 struct dentry
*dentry
;
3883 unsigned int lookup_flags
= 0;
3885 name
= filename_parentat(dfd
, getname(pathname
), lookup_flags
,
3886 &path
, &last
, &type
);
3888 return PTR_ERR(name
);
3902 error
= mnt_want_write(path
.mnt
);
3906 inode_lock_nested(path
.dentry
->d_inode
, I_MUTEX_PARENT
);
3907 dentry
= __lookup_hash(&last
, path
.dentry
, lookup_flags
);
3908 error
= PTR_ERR(dentry
);
3911 if (!dentry
->d_inode
) {
3915 error
= security_path_rmdir(&path
, dentry
);
3918 error
= vfs_rmdir(path
.dentry
->d_inode
, dentry
);
3922 inode_unlock(path
.dentry
->d_inode
);
3923 mnt_drop_write(path
.mnt
);
3927 if (retry_estale(error
, lookup_flags
)) {
3928 lookup_flags
|= LOOKUP_REVAL
;
3934 SYSCALL_DEFINE1(rmdir
, const char __user
*, pathname
)
3936 return do_rmdir(AT_FDCWD
, pathname
);
3940 * vfs_unlink - unlink a filesystem object
3941 * @dir: parent directory
3943 * @delegated_inode: returns victim inode, if the inode is delegated.
3945 * The caller must hold dir->i_mutex.
3947 * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and
3948 * return a reference to the inode in delegated_inode. The caller
3949 * should then break the delegation on that inode and retry. Because
3950 * breaking a delegation may take a long time, the caller should drop
3951 * dir->i_mutex before doing so.
3953 * Alternatively, a caller may pass NULL for delegated_inode. This may
3954 * be appropriate for callers that expect the underlying filesystem not
3955 * to be NFS exported.
3957 int vfs_unlink(struct inode
*dir
, struct dentry
*dentry
, struct inode
**delegated_inode
)
3959 struct inode
*target
= dentry
->d_inode
;
3960 int error
= may_delete(dir
, dentry
, 0);
3965 if (!dir
->i_op
->unlink
)
3969 if (is_local_mountpoint(dentry
))
3972 error
= security_inode_unlink(dir
, dentry
);
3974 error
= try_break_deleg(target
, delegated_inode
);
3977 error
= dir
->i_op
->unlink(dir
, dentry
);
3980 detach_mounts(dentry
);
3985 inode_unlock(target
);
3987 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
3988 if (!error
&& !(dentry
->d_flags
& DCACHE_NFSFS_RENAMED
)) {
3989 fsnotify_link_count(target
);
3995 EXPORT_SYMBOL(vfs_unlink
);
3998 * Make sure that the actual truncation of the file will occur outside its
3999 * directory's i_mutex. Truncate can take a long time if there is a lot of
4000 * writeout happening, and we don't want to prevent access to the directory
4001 * while waiting on the I/O.
4003 long do_unlinkat(int dfd
, struct filename
*name
)
4006 struct dentry
*dentry
;
4010 struct inode
*inode
= NULL
;
4011 struct inode
*delegated_inode
= NULL
;
4012 unsigned int lookup_flags
= 0;
4014 name
= filename_parentat(dfd
, name
, lookup_flags
, &path
, &last
, &type
);
4016 return PTR_ERR(name
);
4019 if (type
!= LAST_NORM
)
4022 error
= mnt_want_write(path
.mnt
);
4026 inode_lock_nested(path
.dentry
->d_inode
, I_MUTEX_PARENT
);
4027 dentry
= __lookup_hash(&last
, path
.dentry
, lookup_flags
);
4028 error
= PTR_ERR(dentry
);
4029 if (!IS_ERR(dentry
)) {
4030 /* Why not before? Because we want correct error value */
4031 if (last
.name
[last
.len
])
4033 inode
= dentry
->d_inode
;
4034 if (d_is_negative(dentry
))
4037 error
= security_path_unlink(&path
, dentry
);
4040 error
= vfs_unlink(path
.dentry
->d_inode
, dentry
, &delegated_inode
);
4044 inode_unlock(path
.dentry
->d_inode
);
4046 iput(inode
); /* truncate the inode here */
4048 if (delegated_inode
) {
4049 error
= break_deleg_wait(&delegated_inode
);
4053 mnt_drop_write(path
.mnt
);
4056 if (retry_estale(error
, lookup_flags
)) {
4057 lookup_flags
|= LOOKUP_REVAL
;
4065 if (d_is_negative(dentry
))
4067 else if (d_is_dir(dentry
))
4074 SYSCALL_DEFINE3(unlinkat
, int, dfd
, const char __user
*, pathname
, int, flag
)
4076 if ((flag
& ~AT_REMOVEDIR
) != 0)
4079 if (flag
& AT_REMOVEDIR
)
4080 return do_rmdir(dfd
, pathname
);
4082 return do_unlinkat(dfd
, getname(pathname
));
4085 SYSCALL_DEFINE1(unlink
, const char __user
*, pathname
)
4087 return do_unlinkat(AT_FDCWD
, getname(pathname
));
4090 int vfs_symlink(struct inode
*dir
, struct dentry
*dentry
, const char *oldname
)
4092 int error
= may_create(dir
, dentry
);
4097 if (!dir
->i_op
->symlink
)
4100 error
= security_inode_symlink(dir
, dentry
, oldname
);
4104 error
= dir
->i_op
->symlink(dir
, dentry
, oldname
);
4106 fsnotify_create(dir
, dentry
);
4109 EXPORT_SYMBOL(vfs_symlink
);
4111 SYSCALL_DEFINE3(symlinkat
, const char __user
*, oldname
,
4112 int, newdfd
, const char __user
*, newname
)
4115 struct filename
*from
;
4116 struct dentry
*dentry
;
4118 unsigned int lookup_flags
= 0;
4120 from
= getname(oldname
);
4122 return PTR_ERR(from
);
4124 dentry
= user_path_create(newdfd
, newname
, &path
, lookup_flags
);
4125 error
= PTR_ERR(dentry
);
4129 error
= security_path_symlink(&path
, dentry
, from
->name
);
4131 error
= vfs_symlink(path
.dentry
->d_inode
, dentry
, from
->name
);
4132 done_path_create(&path
, dentry
);
4133 if (retry_estale(error
, lookup_flags
)) {
4134 lookup_flags
|= LOOKUP_REVAL
;
4142 SYSCALL_DEFINE2(symlink
, const char __user
*, oldname
, const char __user
*, newname
)
4144 return sys_symlinkat(oldname
, AT_FDCWD
, newname
);
4148 * vfs_link - create a new link
4149 * @old_dentry: object to be linked
4151 * @new_dentry: where to create the new link
4152 * @delegated_inode: returns inode needing a delegation break
4154 * The caller must hold dir->i_mutex
4156 * If vfs_link discovers a delegation on the to-be-linked file in need
4157 * of breaking, it will return -EWOULDBLOCK and return a reference to the
4158 * inode in delegated_inode. The caller should then break the delegation
4159 * and retry. Because breaking a delegation may take a long time, the
4160 * caller should drop the i_mutex before doing so.
4162 * Alternatively, a caller may pass NULL for delegated_inode. This may
4163 * be appropriate for callers that expect the underlying filesystem not
4164 * to be NFS exported.
4166 int vfs_link(struct dentry
*old_dentry
, struct inode
*dir
, struct dentry
*new_dentry
, struct inode
**delegated_inode
)
4168 struct inode
*inode
= old_dentry
->d_inode
;
4169 unsigned max_links
= dir
->i_sb
->s_max_links
;
4175 error
= may_create(dir
, new_dentry
);
4179 if (dir
->i_sb
!= inode
->i_sb
)
4183 * A link to an append-only or immutable file cannot be created.
4185 if (IS_APPEND(inode
) || IS_IMMUTABLE(inode
))
4188 * Updating the link count will likely cause i_uid and i_gid to
4189 * be writen back improperly if their true value is unknown to
4192 if (HAS_UNMAPPED_ID(inode
))
4194 if (!dir
->i_op
->link
)
4196 if (S_ISDIR(inode
->i_mode
))
4199 error
= security_inode_link(old_dentry
, dir
, new_dentry
);
4204 /* Make sure we don't allow creating hardlink to an unlinked file */
4205 if (inode
->i_nlink
== 0 && !(inode
->i_state
& I_LINKABLE
))
4207 else if (max_links
&& inode
->i_nlink
>= max_links
)
4210 error
= try_break_deleg(inode
, delegated_inode
);
4212 error
= dir
->i_op
->link(old_dentry
, dir
, new_dentry
);
4215 if (!error
&& (inode
->i_state
& I_LINKABLE
)) {
4216 spin_lock(&inode
->i_lock
);
4217 inode
->i_state
&= ~I_LINKABLE
;
4218 spin_unlock(&inode
->i_lock
);
4220 inode_unlock(inode
);
4222 fsnotify_link(dir
, inode
, new_dentry
);
4225 EXPORT_SYMBOL(vfs_link
);
4228 * Hardlinks are often used in delicate situations. We avoid
4229 * security-related surprises by not following symlinks on the
4232 * We don't follow them on the oldname either to be compatible
4233 * with linux 2.0, and to avoid hard-linking to directories
4234 * and other special files. --ADM
4236 SYSCALL_DEFINE5(linkat
, int, olddfd
, const char __user
*, oldname
,
4237 int, newdfd
, const char __user
*, newname
, int, flags
)
4239 struct dentry
*new_dentry
;
4240 struct path old_path
, new_path
;
4241 struct inode
*delegated_inode
= NULL
;
4245 if ((flags
& ~(AT_SYMLINK_FOLLOW
| AT_EMPTY_PATH
)) != 0)
4248 * To use null names we require CAP_DAC_READ_SEARCH
4249 * This ensures that not everyone will be able to create
4250 * handlink using the passed filedescriptor.
4252 if (flags
& AT_EMPTY_PATH
) {
4253 if (!capable(CAP_DAC_READ_SEARCH
))
4258 if (flags
& AT_SYMLINK_FOLLOW
)
4259 how
|= LOOKUP_FOLLOW
;
4261 error
= user_path_at(olddfd
, oldname
, how
, &old_path
);
4265 new_dentry
= user_path_create(newdfd
, newname
, &new_path
,
4266 (how
& LOOKUP_REVAL
));
4267 error
= PTR_ERR(new_dentry
);
4268 if (IS_ERR(new_dentry
))
4272 if (old_path
.mnt
!= new_path
.mnt
)
4274 error
= may_linkat(&old_path
);
4275 if (unlikely(error
))
4277 error
= security_path_link(old_path
.dentry
, &new_path
, new_dentry
);
4280 error
= vfs_link(old_path
.dentry
, new_path
.dentry
->d_inode
, new_dentry
, &delegated_inode
);
4282 done_path_create(&new_path
, new_dentry
);
4283 if (delegated_inode
) {
4284 error
= break_deleg_wait(&delegated_inode
);
4286 path_put(&old_path
);
4290 if (retry_estale(error
, how
)) {
4291 path_put(&old_path
);
4292 how
|= LOOKUP_REVAL
;
4296 path_put(&old_path
);
4301 SYSCALL_DEFINE2(link
, const char __user
*, oldname
, const char __user
*, newname
)
4303 return sys_linkat(AT_FDCWD
, oldname
, AT_FDCWD
, newname
, 0);
4307 * vfs_rename - rename a filesystem object
4308 * @old_dir: parent of source
4309 * @old_dentry: source
4310 * @new_dir: parent of destination
4311 * @new_dentry: destination
4312 * @delegated_inode: returns an inode needing a delegation break
4313 * @flags: rename flags
4315 * The caller must hold multiple mutexes--see lock_rename()).
4317 * If vfs_rename discovers a delegation in need of breaking at either
4318 * the source or destination, it will return -EWOULDBLOCK and return a
4319 * reference to the inode in delegated_inode. The caller should then
4320 * break the delegation and retry. Because breaking a delegation may
4321 * take a long time, the caller should drop all locks before doing
4324 * Alternatively, a caller may pass NULL for delegated_inode. This may
4325 * be appropriate for callers that expect the underlying filesystem not
4326 * to be NFS exported.
4328 * The worst of all namespace operations - renaming directory. "Perverted"
4329 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
4332 * a) we can get into loop creation.
4333 * b) race potential - two innocent renames can create a loop together.
4334 * That's where 4.4 screws up. Current fix: serialization on
4335 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
4337 * c) we have to lock _four_ objects - parents and victim (if it exists),
4338 * and source (if it is not a directory).
4339 * And that - after we got ->i_mutex on parents (until then we don't know
4340 * whether the target exists). Solution: try to be smart with locking
4341 * order for inodes. We rely on the fact that tree topology may change
4342 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
4343 * move will be locked. Thus we can rank directories by the tree
4344 * (ancestors first) and rank all non-directories after them.
4345 * That works since everybody except rename does "lock parent, lookup,
4346 * lock child" and rename is under ->s_vfs_rename_mutex.
4347 * HOWEVER, it relies on the assumption that any object with ->lookup()
4348 * has no more than 1 dentry. If "hybrid" objects will ever appear,
4349 * we'd better make sure that there's no link(2) for them.
4350 * d) conversion from fhandle to dentry may come in the wrong moment - when
4351 * we are removing the target. Solution: we will have to grab ->i_mutex
4352 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
4353 * ->i_mutex on parents, which works but leads to some truly excessive
4356 int vfs_rename(struct inode
*old_dir
, struct dentry
*old_dentry
,
4357 struct inode
*new_dir
, struct dentry
*new_dentry
,
4358 struct inode
**delegated_inode
, unsigned int flags
)
4361 bool is_dir
= d_is_dir(old_dentry
);
4362 struct inode
*source
= old_dentry
->d_inode
;
4363 struct inode
*target
= new_dentry
->d_inode
;
4364 bool new_is_dir
= false;
4365 unsigned max_links
= new_dir
->i_sb
->s_max_links
;
4366 struct name_snapshot old_name
;
4368 if (source
== target
)
4371 error
= may_delete(old_dir
, old_dentry
, is_dir
);
4376 error
= may_create(new_dir
, new_dentry
);
4378 new_is_dir
= d_is_dir(new_dentry
);
4380 if (!(flags
& RENAME_EXCHANGE
))
4381 error
= may_delete(new_dir
, new_dentry
, is_dir
);
4383 error
= may_delete(new_dir
, new_dentry
, new_is_dir
);
4388 if (!old_dir
->i_op
->rename
)
4392 * If we are going to change the parent - check write permissions,
4393 * we'll need to flip '..'.
4395 if (new_dir
!= old_dir
) {
4397 error
= inode_permission(source
, MAY_WRITE
);
4401 if ((flags
& RENAME_EXCHANGE
) && new_is_dir
) {
4402 error
= inode_permission(target
, MAY_WRITE
);
4408 error
= security_inode_rename(old_dir
, old_dentry
, new_dir
, new_dentry
,
4413 take_dentry_name_snapshot(&old_name
, old_dentry
);
4415 if (!is_dir
|| (flags
& RENAME_EXCHANGE
))
4416 lock_two_nondirectories(source
, target
);
4421 if (is_local_mountpoint(old_dentry
) || is_local_mountpoint(new_dentry
))
4424 if (max_links
&& new_dir
!= old_dir
) {
4426 if (is_dir
&& !new_is_dir
&& new_dir
->i_nlink
>= max_links
)
4428 if ((flags
& RENAME_EXCHANGE
) && !is_dir
&& new_is_dir
&&
4429 old_dir
->i_nlink
>= max_links
)
4432 if (is_dir
&& !(flags
& RENAME_EXCHANGE
) && target
)
4433 shrink_dcache_parent(new_dentry
);
4435 error
= try_break_deleg(source
, delegated_inode
);
4439 if (target
&& !new_is_dir
) {
4440 error
= try_break_deleg(target
, delegated_inode
);
4444 error
= old_dir
->i_op
->rename(old_dir
, old_dentry
,
4445 new_dir
, new_dentry
, flags
);
4449 if (!(flags
& RENAME_EXCHANGE
) && target
) {
4451 target
->i_flags
|= S_DEAD
;
4452 dont_mount(new_dentry
);
4453 detach_mounts(new_dentry
);
4455 if (!(old_dir
->i_sb
->s_type
->fs_flags
& FS_RENAME_DOES_D_MOVE
)) {
4456 if (!(flags
& RENAME_EXCHANGE
))
4457 d_move(old_dentry
, new_dentry
);
4459 d_exchange(old_dentry
, new_dentry
);
4462 if (!is_dir
|| (flags
& RENAME_EXCHANGE
))
4463 unlock_two_nondirectories(source
, target
);
4465 inode_unlock(target
);
4468 fsnotify_move(old_dir
, new_dir
, old_name
.name
, is_dir
,
4469 !(flags
& RENAME_EXCHANGE
) ? target
: NULL
, old_dentry
);
4470 if (flags
& RENAME_EXCHANGE
) {
4471 fsnotify_move(new_dir
, old_dir
, old_dentry
->d_name
.name
,
4472 new_is_dir
, NULL
, new_dentry
);
4475 release_dentry_name_snapshot(&old_name
);
4479 EXPORT_SYMBOL(vfs_rename
);
4481 SYSCALL_DEFINE5(renameat2
, int, olddfd
, const char __user
*, oldname
,
4482 int, newdfd
, const char __user
*, newname
, unsigned int, flags
)
4484 struct dentry
*old_dentry
, *new_dentry
;
4485 struct dentry
*trap
;
4486 struct path old_path
, new_path
;
4487 struct qstr old_last
, new_last
;
4488 int old_type
, new_type
;
4489 struct inode
*delegated_inode
= NULL
;
4490 struct filename
*from
;
4491 struct filename
*to
;
4492 unsigned int lookup_flags
= 0, target_flags
= LOOKUP_RENAME_TARGET
;
4493 bool should_retry
= false;
4496 if (flags
& ~(RENAME_NOREPLACE
| RENAME_EXCHANGE
| RENAME_WHITEOUT
))
4499 if ((flags
& (RENAME_NOREPLACE
| RENAME_WHITEOUT
)) &&
4500 (flags
& RENAME_EXCHANGE
))
4503 if ((flags
& RENAME_WHITEOUT
) && !capable(CAP_MKNOD
))
4506 if (flags
& RENAME_EXCHANGE
)
4510 from
= filename_parentat(olddfd
, getname(oldname
), lookup_flags
,
4511 &old_path
, &old_last
, &old_type
);
4513 error
= PTR_ERR(from
);
4517 to
= filename_parentat(newdfd
, getname(newname
), lookup_flags
,
4518 &new_path
, &new_last
, &new_type
);
4520 error
= PTR_ERR(to
);
4525 if (old_path
.mnt
!= new_path
.mnt
)
4529 if (old_type
!= LAST_NORM
)
4532 if (flags
& RENAME_NOREPLACE
)
4534 if (new_type
!= LAST_NORM
)
4537 error
= mnt_want_write(old_path
.mnt
);
4542 trap
= lock_rename(new_path
.dentry
, old_path
.dentry
);
4544 old_dentry
= __lookup_hash(&old_last
, old_path
.dentry
, lookup_flags
);
4545 error
= PTR_ERR(old_dentry
);
4546 if (IS_ERR(old_dentry
))
4548 /* source must exist */
4550 if (d_is_negative(old_dentry
))
4552 new_dentry
= __lookup_hash(&new_last
, new_path
.dentry
, lookup_flags
| target_flags
);
4553 error
= PTR_ERR(new_dentry
);
4554 if (IS_ERR(new_dentry
))
4557 if ((flags
& RENAME_NOREPLACE
) && d_is_positive(new_dentry
))
4559 if (flags
& RENAME_EXCHANGE
) {
4561 if (d_is_negative(new_dentry
))
4564 if (!d_is_dir(new_dentry
)) {
4566 if (new_last
.name
[new_last
.len
])
4570 /* unless the source is a directory trailing slashes give -ENOTDIR */
4571 if (!d_is_dir(old_dentry
)) {
4573 if (old_last
.name
[old_last
.len
])
4575 if (!(flags
& RENAME_EXCHANGE
) && new_last
.name
[new_last
.len
])
4578 /* source should not be ancestor of target */
4580 if (old_dentry
== trap
)
4582 /* target should not be an ancestor of source */
4583 if (!(flags
& RENAME_EXCHANGE
))
4585 if (new_dentry
== trap
)
4588 error
= security_path_rename(&old_path
, old_dentry
,
4589 &new_path
, new_dentry
, flags
);
4592 error
= vfs_rename(old_path
.dentry
->d_inode
, old_dentry
,
4593 new_path
.dentry
->d_inode
, new_dentry
,
4594 &delegated_inode
, flags
);
4600 unlock_rename(new_path
.dentry
, old_path
.dentry
);
4601 if (delegated_inode
) {
4602 error
= break_deleg_wait(&delegated_inode
);
4606 mnt_drop_write(old_path
.mnt
);
4608 if (retry_estale(error
, lookup_flags
))
4609 should_retry
= true;
4610 path_put(&new_path
);
4613 path_put(&old_path
);
4616 should_retry
= false;
4617 lookup_flags
|= LOOKUP_REVAL
;
4624 SYSCALL_DEFINE4(renameat
, int, olddfd
, const char __user
*, oldname
,
4625 int, newdfd
, const char __user
*, newname
)
4627 return sys_renameat2(olddfd
, oldname
, newdfd
, newname
, 0);
4630 SYSCALL_DEFINE2(rename
, const char __user
*, oldname
, const char __user
*, newname
)
4632 return sys_renameat2(AT_FDCWD
, oldname
, AT_FDCWD
, newname
, 0);
4635 int vfs_whiteout(struct inode
*dir
, struct dentry
*dentry
)
4637 int error
= may_create(dir
, dentry
);
4641 if (!dir
->i_op
->mknod
)
4644 return dir
->i_op
->mknod(dir
, dentry
,
4645 S_IFCHR
| WHITEOUT_MODE
, WHITEOUT_DEV
);
4647 EXPORT_SYMBOL(vfs_whiteout
);
4649 int readlink_copy(char __user
*buffer
, int buflen
, const char *link
)
4651 int len
= PTR_ERR(link
);
4656 if (len
> (unsigned) buflen
)
4658 if (copy_to_user(buffer
, link
, len
))
4665 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
4666 * have ->get_link() not calling nd_jump_link(). Using (or not using) it
4667 * for any given inode is up to filesystem.
4669 static int generic_readlink(struct dentry
*dentry
, char __user
*buffer
,
4672 DEFINE_DELAYED_CALL(done
);
4673 struct inode
*inode
= d_inode(dentry
);
4674 const char *link
= inode
->i_link
;
4678 link
= inode
->i_op
->get_link(dentry
, inode
, &done
);
4680 return PTR_ERR(link
);
4682 res
= readlink_copy(buffer
, buflen
, link
);
4683 do_delayed_call(&done
);
4688 * vfs_readlink - copy symlink body into userspace buffer
4689 * @dentry: dentry on which to get symbolic link
4690 * @buffer: user memory pointer
4691 * @buflen: size of buffer
4693 * Does not touch atime. That's up to the caller if necessary
4695 * Does not call security hook.
4697 int vfs_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
)
4699 struct inode
*inode
= d_inode(dentry
);
4701 if (unlikely(!(inode
->i_opflags
& IOP_DEFAULT_READLINK
))) {
4702 if (unlikely(inode
->i_op
->readlink
))
4703 return inode
->i_op
->readlink(dentry
, buffer
, buflen
);
4705 if (!d_is_symlink(dentry
))
4708 spin_lock(&inode
->i_lock
);
4709 inode
->i_opflags
|= IOP_DEFAULT_READLINK
;
4710 spin_unlock(&inode
->i_lock
);
4713 return generic_readlink(dentry
, buffer
, buflen
);
4715 EXPORT_SYMBOL(vfs_readlink
);
4718 * vfs_get_link - get symlink body
4719 * @dentry: dentry on which to get symbolic link
4720 * @done: caller needs to free returned data with this
4722 * Calls security hook and i_op->get_link() on the supplied inode.
4724 * It does not touch atime. That's up to the caller if necessary.
4726 * Does not work on "special" symlinks like /proc/$$/fd/N
4728 const char *vfs_get_link(struct dentry
*dentry
, struct delayed_call
*done
)
4730 const char *res
= ERR_PTR(-EINVAL
);
4731 struct inode
*inode
= d_inode(dentry
);
4733 if (d_is_symlink(dentry
)) {
4734 res
= ERR_PTR(security_inode_readlink(dentry
));
4736 res
= inode
->i_op
->get_link(dentry
, inode
, done
);
4740 EXPORT_SYMBOL(vfs_get_link
);
4742 /* get the link contents into pagecache */
4743 const char *page_get_link(struct dentry
*dentry
, struct inode
*inode
,
4744 struct delayed_call
*callback
)
4748 struct address_space
*mapping
= inode
->i_mapping
;
4751 page
= find_get_page(mapping
, 0);
4753 return ERR_PTR(-ECHILD
);
4754 if (!PageUptodate(page
)) {
4756 return ERR_PTR(-ECHILD
);
4759 page
= read_mapping_page(mapping
, 0, NULL
);
4763 set_delayed_call(callback
, page_put_link
, page
);
4764 BUG_ON(mapping_gfp_mask(mapping
) & __GFP_HIGHMEM
);
4765 kaddr
= page_address(page
);
4766 nd_terminate_link(kaddr
, inode
->i_size
, PAGE_SIZE
- 1);
4770 EXPORT_SYMBOL(page_get_link
);
4772 void page_put_link(void *arg
)
4776 EXPORT_SYMBOL(page_put_link
);
4778 int page_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
)
4780 DEFINE_DELAYED_CALL(done
);
4781 int res
= readlink_copy(buffer
, buflen
,
4782 page_get_link(dentry
, d_inode(dentry
),
4784 do_delayed_call(&done
);
4787 EXPORT_SYMBOL(page_readlink
);
4790 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
4792 int __page_symlink(struct inode
*inode
, const char *symname
, int len
, int nofs
)
4794 struct address_space
*mapping
= inode
->i_mapping
;
4798 unsigned int flags
= 0;
4800 flags
|= AOP_FLAG_NOFS
;
4803 err
= pagecache_write_begin(NULL
, mapping
, 0, len
-1,
4804 flags
, &page
, &fsdata
);
4808 memcpy(page_address(page
), symname
, len
-1);
4810 err
= pagecache_write_end(NULL
, mapping
, 0, len
-1, len
-1,
4817 mark_inode_dirty(inode
);
4822 EXPORT_SYMBOL(__page_symlink
);
4824 int page_symlink(struct inode
*inode
, const char *symname
, int len
)
4826 return __page_symlink(inode
, symname
, len
,
4827 !mapping_gfp_constraint(inode
->i_mapping
, __GFP_FS
));
4829 EXPORT_SYMBOL(page_symlink
);
4831 const struct inode_operations page_symlink_inode_operations
= {
4832 .get_link
= page_get_link
,
4834 EXPORT_SYMBOL(page_symlink_inode_operations
);