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 * sb_permission - Check superblock-level permissions
396 * @sb: Superblock of inode to check permission on
397 * @inode: Inode to check permission on
398 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
400 * Separate out file-system wide checks from inode-specific permission checks.
402 static int sb_permission(struct super_block
*sb
, struct inode
*inode
, int mask
)
404 if (unlikely(mask
& MAY_WRITE
)) {
405 umode_t mode
= inode
->i_mode
;
407 /* Nobody gets write access to a read-only fs. */
408 if (sb_rdonly(sb
) && (S_ISREG(mode
) || S_ISDIR(mode
) || S_ISLNK(mode
)))
415 * inode_permission - Check for access rights to a given inode
416 * @inode: Inode to check permission on
417 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
419 * Check for read/write/execute permissions on an inode. We use fs[ug]id for
420 * this, letting us set arbitrary permissions for filesystem access without
421 * changing the "normal" UIDs which are used for other things.
423 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
425 int inode_permission(struct inode
*inode
, int mask
)
429 retval
= sb_permission(inode
->i_sb
, inode
, mask
);
433 if (unlikely(mask
& MAY_WRITE
)) {
435 * Nobody gets write access to an immutable file.
437 if (IS_IMMUTABLE(inode
))
441 * Updating mtime will likely cause i_uid and i_gid to be
442 * written back improperly if their true value is unknown
445 if (HAS_UNMAPPED_ID(inode
))
449 retval
= do_inode_permission(inode
, mask
);
453 retval
= devcgroup_inode_permission(inode
, mask
);
457 return security_inode_permission(inode
, mask
);
459 EXPORT_SYMBOL(inode_permission
);
462 * path_get - get a reference to a path
463 * @path: path to get the reference to
465 * Given a path increment the reference count to the dentry and the vfsmount.
467 void path_get(const struct path
*path
)
472 EXPORT_SYMBOL(path_get
);
475 * path_put - put a reference to a path
476 * @path: path to put the reference to
478 * Given a path decrement the reference count to the dentry and the vfsmount.
480 void path_put(const struct path
*path
)
485 EXPORT_SYMBOL(path_put
);
487 #define EMBEDDED_LEVELS 2
492 struct inode
*inode
; /* path.dentry.d_inode */
497 int total_link_count
;
500 struct delayed_call done
;
503 } *stack
, internal
[EMBEDDED_LEVELS
];
504 struct filename
*name
;
505 struct nameidata
*saved
;
506 struct inode
*link_inode
;
509 } __randomize_layout
;
511 static void set_nameidata(struct nameidata
*p
, int dfd
, struct filename
*name
)
513 struct nameidata
*old
= current
->nameidata
;
514 p
->stack
= p
->internal
;
517 p
->total_link_count
= old
? old
->total_link_count
: 0;
519 current
->nameidata
= p
;
522 static void restore_nameidata(void)
524 struct nameidata
*now
= current
->nameidata
, *old
= now
->saved
;
526 current
->nameidata
= old
;
528 old
->total_link_count
= now
->total_link_count
;
529 if (now
->stack
!= now
->internal
)
533 static int __nd_alloc_stack(struct nameidata
*nd
)
537 if (nd
->flags
& LOOKUP_RCU
) {
538 p
= kmalloc_array(MAXSYMLINKS
, sizeof(struct saved
),
543 p
= kmalloc_array(MAXSYMLINKS
, sizeof(struct saved
),
548 memcpy(p
, nd
->internal
, sizeof(nd
->internal
));
554 * path_connected - Verify that a path->dentry is below path->mnt.mnt_root
555 * @path: nameidate to verify
557 * Rename can sometimes move a file or directory outside of a bind
558 * mount, path_connected allows those cases to be detected.
560 static bool path_connected(const struct path
*path
)
562 struct vfsmount
*mnt
= path
->mnt
;
563 struct super_block
*sb
= mnt
->mnt_sb
;
565 /* Bind mounts and multi-root filesystems can have disconnected paths */
566 if (!(sb
->s_iflags
& SB_I_MULTIROOT
) && (mnt
->mnt_root
== sb
->s_root
))
569 return is_subdir(path
->dentry
, mnt
->mnt_root
);
572 static inline int nd_alloc_stack(struct nameidata
*nd
)
574 if (likely(nd
->depth
!= EMBEDDED_LEVELS
))
576 if (likely(nd
->stack
!= nd
->internal
))
578 return __nd_alloc_stack(nd
);
581 static void drop_links(struct nameidata
*nd
)
585 struct saved
*last
= nd
->stack
+ i
;
586 do_delayed_call(&last
->done
);
587 clear_delayed_call(&last
->done
);
591 static void terminate_walk(struct nameidata
*nd
)
594 if (!(nd
->flags
& LOOKUP_RCU
)) {
597 for (i
= 0; i
< nd
->depth
; i
++)
598 path_put(&nd
->stack
[i
].link
);
599 if (nd
->flags
& LOOKUP_ROOT_GRABBED
) {
601 nd
->flags
&= ~LOOKUP_ROOT_GRABBED
;
604 nd
->flags
&= ~LOOKUP_RCU
;
610 /* path_put is needed afterwards regardless of success or failure */
611 static bool legitimize_path(struct nameidata
*nd
,
612 struct path
*path
, unsigned seq
)
614 int res
= __legitimize_mnt(path
->mnt
, nd
->m_seq
);
621 if (unlikely(!lockref_get_not_dead(&path
->dentry
->d_lockref
))) {
625 return !read_seqcount_retry(&path
->dentry
->d_seq
, seq
);
628 static bool legitimize_links(struct nameidata
*nd
)
631 for (i
= 0; i
< nd
->depth
; i
++) {
632 struct saved
*last
= nd
->stack
+ i
;
633 if (unlikely(!legitimize_path(nd
, &last
->link
, last
->seq
))) {
642 static bool legitimize_root(struct nameidata
*nd
)
644 if (!nd
->root
.mnt
|| (nd
->flags
& LOOKUP_ROOT
))
646 nd
->flags
|= LOOKUP_ROOT_GRABBED
;
647 return legitimize_path(nd
, &nd
->root
, nd
->root_seq
);
651 * Path walking has 2 modes, rcu-walk and ref-walk (see
652 * Documentation/filesystems/path-lookup.txt). In situations when we can't
653 * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
654 * normal reference counts on dentries and vfsmounts to transition to ref-walk
655 * mode. Refcounts are grabbed at the last known good point before rcu-walk
656 * got stuck, so ref-walk may continue from there. If this is not successful
657 * (eg. a seqcount has changed), then failure is returned and it's up to caller
658 * to restart the path walk from the beginning in ref-walk mode.
662 * unlazy_walk - try to switch to ref-walk mode.
663 * @nd: nameidata pathwalk data
664 * Returns: 0 on success, -ECHILD on failure
666 * unlazy_walk attempts to legitimize the current nd->path and nd->root
668 * Must be called from rcu-walk context.
669 * Nothing should touch nameidata between unlazy_walk() failure and
672 static int unlazy_walk(struct nameidata
*nd
)
674 struct dentry
*parent
= nd
->path
.dentry
;
676 BUG_ON(!(nd
->flags
& LOOKUP_RCU
));
678 nd
->flags
&= ~LOOKUP_RCU
;
679 if (unlikely(!legitimize_links(nd
)))
681 if (unlikely(!legitimize_path(nd
, &nd
->path
, nd
->seq
)))
683 if (unlikely(!legitimize_root(nd
)))
686 BUG_ON(nd
->inode
!= parent
->d_inode
);
691 nd
->path
.dentry
= NULL
;
698 * unlazy_child - try to switch to ref-walk mode.
699 * @nd: nameidata pathwalk data
700 * @dentry: child of nd->path.dentry
701 * @seq: seq number to check dentry against
702 * Returns: 0 on success, -ECHILD on failure
704 * unlazy_child attempts to legitimize the current nd->path, nd->root and dentry
705 * for ref-walk mode. @dentry must be a path found by a do_lookup call on
706 * @nd. Must be called from rcu-walk context.
707 * Nothing should touch nameidata between unlazy_child() failure and
710 static int unlazy_child(struct nameidata
*nd
, struct dentry
*dentry
, unsigned seq
)
712 BUG_ON(!(nd
->flags
& LOOKUP_RCU
));
714 nd
->flags
&= ~LOOKUP_RCU
;
715 if (unlikely(!legitimize_links(nd
)))
717 if (unlikely(!legitimize_mnt(nd
->path
.mnt
, nd
->m_seq
)))
719 if (unlikely(!lockref_get_not_dead(&nd
->path
.dentry
->d_lockref
)))
723 * We need to move both the parent and the dentry from the RCU domain
724 * to be properly refcounted. And the sequence number in the dentry
725 * validates *both* dentry counters, since we checked the sequence
726 * number of the parent after we got the child sequence number. So we
727 * know the parent must still be valid if the child sequence number is
729 if (unlikely(!lockref_get_not_dead(&dentry
->d_lockref
)))
731 if (unlikely(read_seqcount_retry(&dentry
->d_seq
, seq
)))
734 * Sequence counts matched. Now make sure that the root is
735 * still valid and get it if required.
737 if (unlikely(!legitimize_root(nd
)))
745 nd
->path
.dentry
= NULL
;
755 static inline int d_revalidate(struct dentry
*dentry
, unsigned int flags
)
757 if (unlikely(dentry
->d_flags
& DCACHE_OP_REVALIDATE
))
758 return dentry
->d_op
->d_revalidate(dentry
, flags
);
764 * complete_walk - successful completion of path walk
765 * @nd: pointer nameidata
767 * If we had been in RCU mode, drop out of it and legitimize nd->path.
768 * Revalidate the final result, unless we'd already done that during
769 * the path walk or the filesystem doesn't ask for it. Return 0 on
770 * success, -error on failure. In case of failure caller does not
771 * need to drop nd->path.
773 static int complete_walk(struct nameidata
*nd
)
775 struct dentry
*dentry
= nd
->path
.dentry
;
778 if (nd
->flags
& LOOKUP_RCU
) {
779 if (!(nd
->flags
& LOOKUP_ROOT
))
781 if (unlikely(unlazy_walk(nd
)))
785 if (likely(!(nd
->flags
& LOOKUP_JUMPED
)))
788 if (likely(!(dentry
->d_flags
& DCACHE_OP_WEAK_REVALIDATE
)))
791 status
= dentry
->d_op
->d_weak_revalidate(dentry
, nd
->flags
);
801 static void set_root(struct nameidata
*nd
)
803 struct fs_struct
*fs
= current
->fs
;
805 if (nd
->flags
& LOOKUP_RCU
) {
809 seq
= read_seqcount_begin(&fs
->seq
);
811 nd
->root_seq
= __read_seqcount_begin(&nd
->root
.dentry
->d_seq
);
812 } while (read_seqcount_retry(&fs
->seq
, seq
));
814 get_fs_root(fs
, &nd
->root
);
815 nd
->flags
|= LOOKUP_ROOT_GRABBED
;
819 static void path_put_conditional(struct path
*path
, struct nameidata
*nd
)
822 if (path
->mnt
!= nd
->path
.mnt
)
826 static inline void path_to_nameidata(const struct path
*path
,
827 struct nameidata
*nd
)
829 if (!(nd
->flags
& LOOKUP_RCU
)) {
830 dput(nd
->path
.dentry
);
831 if (nd
->path
.mnt
!= path
->mnt
)
832 mntput(nd
->path
.mnt
);
834 nd
->path
.mnt
= path
->mnt
;
835 nd
->path
.dentry
= path
->dentry
;
838 static int nd_jump_root(struct nameidata
*nd
)
840 if (nd
->flags
& LOOKUP_RCU
) {
844 nd
->inode
= d
->d_inode
;
845 nd
->seq
= nd
->root_seq
;
846 if (unlikely(read_seqcount_retry(&d
->d_seq
, nd
->seq
)))
852 nd
->inode
= nd
->path
.dentry
->d_inode
;
854 nd
->flags
|= LOOKUP_JUMPED
;
859 * Helper to directly jump to a known parsed path from ->get_link,
860 * caller must have taken a reference to path beforehand.
862 void nd_jump_link(struct path
*path
)
864 struct nameidata
*nd
= current
->nameidata
;
868 nd
->inode
= nd
->path
.dentry
->d_inode
;
869 nd
->flags
|= LOOKUP_JUMPED
;
872 static inline void put_link(struct nameidata
*nd
)
874 struct saved
*last
= nd
->stack
+ --nd
->depth
;
875 do_delayed_call(&last
->done
);
876 if (!(nd
->flags
& LOOKUP_RCU
))
877 path_put(&last
->link
);
880 int sysctl_protected_symlinks __read_mostly
= 1;
881 int sysctl_protected_hardlinks __read_mostly
= 1;
882 int sysctl_protected_fifos __read_mostly
;
883 int sysctl_protected_regular __read_mostly
;
886 * may_follow_link - Check symlink following for unsafe situations
887 * @nd: nameidata pathwalk data
889 * In the case of the sysctl_protected_symlinks sysctl being enabled,
890 * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
891 * in a sticky world-writable directory. This is to protect privileged
892 * processes from failing races against path names that may change out
893 * from under them by way of other users creating malicious symlinks.
894 * It will permit symlinks to be followed only when outside a sticky
895 * world-writable directory, or when the uid of the symlink and follower
896 * match, or when the directory owner matches the symlink's owner.
898 * Returns 0 if following the symlink is allowed, -ve on error.
900 static inline int may_follow_link(struct nameidata
*nd
)
902 const struct inode
*inode
;
903 const struct inode
*parent
;
906 if (!sysctl_protected_symlinks
)
909 /* Allowed if owner and follower match. */
910 inode
= nd
->link_inode
;
911 if (uid_eq(current_cred()->fsuid
, inode
->i_uid
))
914 /* Allowed if parent directory not sticky and world-writable. */
916 if ((parent
->i_mode
& (S_ISVTX
|S_IWOTH
)) != (S_ISVTX
|S_IWOTH
))
919 /* Allowed if parent directory and link owner match. */
920 puid
= parent
->i_uid
;
921 if (uid_valid(puid
) && uid_eq(puid
, inode
->i_uid
))
924 if (nd
->flags
& LOOKUP_RCU
)
927 audit_inode(nd
->name
, nd
->stack
[0].link
.dentry
, 0);
928 audit_log_link_denied("follow_link");
933 * safe_hardlink_source - Check for safe hardlink conditions
934 * @inode: the source inode to hardlink from
936 * Return false if at least one of the following conditions:
937 * - inode is not a regular file
939 * - inode is setgid and group-exec
940 * - access failure for read and write
942 * Otherwise returns true.
944 static bool safe_hardlink_source(struct inode
*inode
)
946 umode_t mode
= inode
->i_mode
;
948 /* Special files should not get pinned to the filesystem. */
952 /* Setuid files should not get pinned to the filesystem. */
956 /* Executable setgid files should not get pinned to the filesystem. */
957 if ((mode
& (S_ISGID
| S_IXGRP
)) == (S_ISGID
| S_IXGRP
))
960 /* Hardlinking to unreadable or unwritable sources is dangerous. */
961 if (inode_permission(inode
, MAY_READ
| MAY_WRITE
))
968 * may_linkat - Check permissions for creating a hardlink
969 * @link: the source to hardlink from
971 * Block hardlink when all of:
972 * - sysctl_protected_hardlinks enabled
973 * - fsuid does not match inode
974 * - hardlink source is unsafe (see safe_hardlink_source() above)
975 * - not CAP_FOWNER in a namespace with the inode owner uid mapped
977 * Returns 0 if successful, -ve on error.
979 static int may_linkat(struct path
*link
)
981 struct inode
*inode
= link
->dentry
->d_inode
;
983 /* Inode writeback is not safe when the uid or gid are invalid. */
984 if (!uid_valid(inode
->i_uid
) || !gid_valid(inode
->i_gid
))
987 if (!sysctl_protected_hardlinks
)
990 /* Source inode owner (or CAP_FOWNER) can hardlink all they like,
991 * otherwise, it must be a safe source.
993 if (safe_hardlink_source(inode
) || inode_owner_or_capable(inode
))
996 audit_log_link_denied("linkat");
1001 * may_create_in_sticky - Check whether an O_CREAT open in a sticky directory
1002 * should be allowed, or not, on files that already
1004 * @dir_mode: mode bits of directory
1005 * @dir_uid: owner of directory
1006 * @inode: the inode of the file to open
1008 * Block an O_CREAT open of a FIFO (or a regular file) when:
1009 * - sysctl_protected_fifos (or sysctl_protected_regular) is enabled
1010 * - the file already exists
1011 * - we are in a sticky directory
1012 * - we don't own the file
1013 * - the owner of the directory doesn't own the file
1014 * - the directory is world writable
1015 * If the sysctl_protected_fifos (or sysctl_protected_regular) is set to 2
1016 * the directory doesn't have to be world writable: being group writable will
1019 * Returns 0 if the open is allowed, -ve on error.
1021 static int may_create_in_sticky(umode_t dir_mode
, kuid_t dir_uid
,
1022 struct inode
* const inode
)
1024 if ((!sysctl_protected_fifos
&& S_ISFIFO(inode
->i_mode
)) ||
1025 (!sysctl_protected_regular
&& S_ISREG(inode
->i_mode
)) ||
1026 likely(!(dir_mode
& S_ISVTX
)) ||
1027 uid_eq(inode
->i_uid
, dir_uid
) ||
1028 uid_eq(current_fsuid(), inode
->i_uid
))
1031 if (likely(dir_mode
& 0002) ||
1033 ((sysctl_protected_fifos
>= 2 && S_ISFIFO(inode
->i_mode
)) ||
1034 (sysctl_protected_regular
>= 2 && S_ISREG(inode
->i_mode
))))) {
1040 static __always_inline
1041 const char *get_link(struct nameidata
*nd
)
1043 struct saved
*last
= nd
->stack
+ nd
->depth
- 1;
1044 struct dentry
*dentry
= last
->link
.dentry
;
1045 struct inode
*inode
= nd
->link_inode
;
1049 if (!(nd
->flags
& LOOKUP_RCU
)) {
1050 touch_atime(&last
->link
);
1052 } else if (atime_needs_update(&last
->link
, inode
)) {
1053 if (unlikely(unlazy_walk(nd
)))
1054 return ERR_PTR(-ECHILD
);
1055 touch_atime(&last
->link
);
1058 error
= security_inode_follow_link(dentry
, inode
,
1059 nd
->flags
& LOOKUP_RCU
);
1060 if (unlikely(error
))
1061 return ERR_PTR(error
);
1063 nd
->last_type
= LAST_BIND
;
1064 res
= READ_ONCE(inode
->i_link
);
1066 const char * (*get
)(struct dentry
*, struct inode
*,
1067 struct delayed_call
*);
1068 get
= inode
->i_op
->get_link
;
1069 if (nd
->flags
& LOOKUP_RCU
) {
1070 res
= get(NULL
, inode
, &last
->done
);
1071 if (res
== ERR_PTR(-ECHILD
)) {
1072 if (unlikely(unlazy_walk(nd
)))
1073 return ERR_PTR(-ECHILD
);
1074 res
= get(dentry
, inode
, &last
->done
);
1077 res
= get(dentry
, inode
, &last
->done
);
1079 if (IS_ERR_OR_NULL(res
))
1085 if (unlikely(nd_jump_root(nd
)))
1086 return ERR_PTR(-ECHILD
);
1087 while (unlikely(*++res
== '/'))
1096 * follow_up - Find the mountpoint of path's vfsmount
1098 * Given a path, find the mountpoint of its source file system.
1099 * Replace @path with the path of the mountpoint in the parent mount.
1102 * Return 1 if we went up a level and 0 if we were already at the
1105 int follow_up(struct path
*path
)
1107 struct mount
*mnt
= real_mount(path
->mnt
);
1108 struct mount
*parent
;
1109 struct dentry
*mountpoint
;
1111 read_seqlock_excl(&mount_lock
);
1112 parent
= mnt
->mnt_parent
;
1113 if (parent
== mnt
) {
1114 read_sequnlock_excl(&mount_lock
);
1117 mntget(&parent
->mnt
);
1118 mountpoint
= dget(mnt
->mnt_mountpoint
);
1119 read_sequnlock_excl(&mount_lock
);
1121 path
->dentry
= mountpoint
;
1123 path
->mnt
= &parent
->mnt
;
1126 EXPORT_SYMBOL(follow_up
);
1129 * Perform an automount
1130 * - return -EISDIR to tell follow_managed() to stop and return the path we
1133 static int follow_automount(struct path
*path
, struct nameidata
*nd
,
1136 struct vfsmount
*mnt
;
1139 if (!path
->dentry
->d_op
|| !path
->dentry
->d_op
->d_automount
)
1142 /* We don't want to mount if someone's just doing a stat -
1143 * unless they're stat'ing a directory and appended a '/' to
1146 * We do, however, want to mount if someone wants to open or
1147 * create a file of any type under the mountpoint, wants to
1148 * traverse through the mountpoint or wants to open the
1149 * mounted directory. Also, autofs may mark negative dentries
1150 * as being automount points. These will need the attentions
1151 * of the daemon to instantiate them before they can be used.
1153 if (!(nd
->flags
& (LOOKUP_PARENT
| LOOKUP_DIRECTORY
|
1154 LOOKUP_OPEN
| LOOKUP_CREATE
| LOOKUP_AUTOMOUNT
)) &&
1155 path
->dentry
->d_inode
)
1158 nd
->total_link_count
++;
1159 if (nd
->total_link_count
>= 40)
1162 mnt
= path
->dentry
->d_op
->d_automount(path
);
1165 * The filesystem is allowed to return -EISDIR here to indicate
1166 * it doesn't want to automount. For instance, autofs would do
1167 * this so that its userspace daemon can mount on this dentry.
1169 * However, we can only permit this if it's a terminal point in
1170 * the path being looked up; if it wasn't then the remainder of
1171 * the path is inaccessible and we should say so.
1173 if (PTR_ERR(mnt
) == -EISDIR
&& (nd
->flags
& LOOKUP_PARENT
))
1175 return PTR_ERR(mnt
);
1178 if (!mnt
) /* mount collision */
1181 if (!*need_mntput
) {
1182 /* lock_mount() may release path->mnt on error */
1184 *need_mntput
= true;
1186 err
= finish_automount(mnt
, path
);
1190 /* Someone else made a mount here whilst we were busy */
1195 path
->dentry
= dget(mnt
->mnt_root
);
1204 * Handle a dentry that is managed in some way.
1205 * - Flagged for transit management (autofs)
1206 * - Flagged as mountpoint
1207 * - Flagged as automount point
1209 * This may only be called in refwalk mode.
1211 * Serialization is taken care of in namespace.c
1213 static int follow_managed(struct path
*path
, struct nameidata
*nd
)
1215 struct vfsmount
*mnt
= path
->mnt
; /* held by caller, must be left alone */
1217 bool need_mntput
= false;
1220 /* Given that we're not holding a lock here, we retain the value in a
1221 * local variable for each dentry as we look at it so that we don't see
1222 * the components of that value change under us */
1223 while (managed
= READ_ONCE(path
->dentry
->d_flags
),
1224 managed
&= DCACHE_MANAGED_DENTRY
,
1225 unlikely(managed
!= 0)) {
1226 /* Allow the filesystem to manage the transit without i_mutex
1228 if (managed
& DCACHE_MANAGE_TRANSIT
) {
1229 BUG_ON(!path
->dentry
->d_op
);
1230 BUG_ON(!path
->dentry
->d_op
->d_manage
);
1231 ret
= path
->dentry
->d_op
->d_manage(path
, false);
1236 /* Transit to a mounted filesystem. */
1237 if (managed
& DCACHE_MOUNTED
) {
1238 struct vfsmount
*mounted
= lookup_mnt(path
);
1243 path
->mnt
= mounted
;
1244 path
->dentry
= dget(mounted
->mnt_root
);
1249 /* Something is mounted on this dentry in another
1250 * namespace and/or whatever was mounted there in this
1251 * namespace got unmounted before lookup_mnt() could
1255 /* Handle an automount point */
1256 if (managed
& DCACHE_NEED_AUTOMOUNT
) {
1257 ret
= follow_automount(path
, nd
, &need_mntput
);
1263 /* We didn't change the current path point */
1267 if (need_mntput
&& path
->mnt
== mnt
)
1269 if (ret
== -EISDIR
|| !ret
)
1272 nd
->flags
|= LOOKUP_JUMPED
;
1273 if (unlikely(ret
< 0))
1274 path_put_conditional(path
, nd
);
1278 int follow_down_one(struct path
*path
)
1280 struct vfsmount
*mounted
;
1282 mounted
= lookup_mnt(path
);
1286 path
->mnt
= mounted
;
1287 path
->dentry
= dget(mounted
->mnt_root
);
1292 EXPORT_SYMBOL(follow_down_one
);
1294 static inline int managed_dentry_rcu(const struct path
*path
)
1296 return (path
->dentry
->d_flags
& DCACHE_MANAGE_TRANSIT
) ?
1297 path
->dentry
->d_op
->d_manage(path
, true) : 0;
1301 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
1302 * we meet a managed dentry that would need blocking.
1304 static bool __follow_mount_rcu(struct nameidata
*nd
, struct path
*path
,
1305 struct inode
**inode
, unsigned *seqp
)
1308 struct mount
*mounted
;
1310 * Don't forget we might have a non-mountpoint managed dentry
1311 * that wants to block transit.
1313 switch (managed_dentry_rcu(path
)) {
1323 if (!d_mountpoint(path
->dentry
))
1324 return !(path
->dentry
->d_flags
& DCACHE_NEED_AUTOMOUNT
);
1326 mounted
= __lookup_mnt(path
->mnt
, path
->dentry
);
1329 path
->mnt
= &mounted
->mnt
;
1330 path
->dentry
= mounted
->mnt
.mnt_root
;
1331 nd
->flags
|= LOOKUP_JUMPED
;
1332 *seqp
= read_seqcount_begin(&path
->dentry
->d_seq
);
1334 * Update the inode too. We don't need to re-check the
1335 * dentry sequence number here after this d_inode read,
1336 * because a mount-point is always pinned.
1338 *inode
= path
->dentry
->d_inode
;
1340 return !read_seqretry(&mount_lock
, nd
->m_seq
) &&
1341 !(path
->dentry
->d_flags
& DCACHE_NEED_AUTOMOUNT
);
1344 static int follow_dotdot_rcu(struct nameidata
*nd
)
1346 struct inode
*inode
= nd
->inode
;
1349 if (path_equal(&nd
->path
, &nd
->root
))
1351 if (nd
->path
.dentry
!= nd
->path
.mnt
->mnt_root
) {
1352 struct dentry
*old
= nd
->path
.dentry
;
1353 struct dentry
*parent
= old
->d_parent
;
1356 inode
= parent
->d_inode
;
1357 seq
= read_seqcount_begin(&parent
->d_seq
);
1358 if (unlikely(read_seqcount_retry(&old
->d_seq
, nd
->seq
)))
1360 nd
->path
.dentry
= parent
;
1362 if (unlikely(!path_connected(&nd
->path
)))
1366 struct mount
*mnt
= real_mount(nd
->path
.mnt
);
1367 struct mount
*mparent
= mnt
->mnt_parent
;
1368 struct dentry
*mountpoint
= mnt
->mnt_mountpoint
;
1369 struct inode
*inode2
= mountpoint
->d_inode
;
1370 unsigned seq
= read_seqcount_begin(&mountpoint
->d_seq
);
1371 if (unlikely(read_seqretry(&mount_lock
, nd
->m_seq
)))
1373 if (&mparent
->mnt
== nd
->path
.mnt
)
1375 /* we know that mountpoint was pinned */
1376 nd
->path
.dentry
= mountpoint
;
1377 nd
->path
.mnt
= &mparent
->mnt
;
1382 while (unlikely(d_mountpoint(nd
->path
.dentry
))) {
1383 struct mount
*mounted
;
1384 mounted
= __lookup_mnt(nd
->path
.mnt
, nd
->path
.dentry
);
1385 if (unlikely(read_seqretry(&mount_lock
, nd
->m_seq
)))
1389 nd
->path
.mnt
= &mounted
->mnt
;
1390 nd
->path
.dentry
= mounted
->mnt
.mnt_root
;
1391 inode
= nd
->path
.dentry
->d_inode
;
1392 nd
->seq
= read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
1399 * Follow down to the covering mount currently visible to userspace. At each
1400 * point, the filesystem owning that dentry may be queried as to whether the
1401 * caller is permitted to proceed or not.
1403 int follow_down(struct path
*path
)
1408 while (managed
= READ_ONCE(path
->dentry
->d_flags
),
1409 unlikely(managed
& DCACHE_MANAGED_DENTRY
)) {
1410 /* Allow the filesystem to manage the transit without i_mutex
1413 * We indicate to the filesystem if someone is trying to mount
1414 * something here. This gives autofs the chance to deny anyone
1415 * other than its daemon the right to mount on its
1418 * The filesystem may sleep at this point.
1420 if (managed
& DCACHE_MANAGE_TRANSIT
) {
1421 BUG_ON(!path
->dentry
->d_op
);
1422 BUG_ON(!path
->dentry
->d_op
->d_manage
);
1423 ret
= path
->dentry
->d_op
->d_manage(path
, false);
1425 return ret
== -EISDIR
? 0 : ret
;
1428 /* Transit to a mounted filesystem. */
1429 if (managed
& DCACHE_MOUNTED
) {
1430 struct vfsmount
*mounted
= lookup_mnt(path
);
1435 path
->mnt
= mounted
;
1436 path
->dentry
= dget(mounted
->mnt_root
);
1440 /* Don't handle automount points here */
1445 EXPORT_SYMBOL(follow_down
);
1448 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1450 static void follow_mount(struct path
*path
)
1452 while (d_mountpoint(path
->dentry
)) {
1453 struct vfsmount
*mounted
= lookup_mnt(path
);
1458 path
->mnt
= mounted
;
1459 path
->dentry
= dget(mounted
->mnt_root
);
1463 static int path_parent_directory(struct path
*path
)
1465 struct dentry
*old
= path
->dentry
;
1466 /* rare case of legitimate dget_parent()... */
1467 path
->dentry
= dget_parent(path
->dentry
);
1469 if (unlikely(!path_connected(path
)))
1474 static int follow_dotdot(struct nameidata
*nd
)
1477 if (path_equal(&nd
->path
, &nd
->root
))
1479 if (nd
->path
.dentry
!= nd
->path
.mnt
->mnt_root
) {
1480 int ret
= path_parent_directory(&nd
->path
);
1485 if (!follow_up(&nd
->path
))
1488 follow_mount(&nd
->path
);
1489 nd
->inode
= nd
->path
.dentry
->d_inode
;
1494 * This looks up the name in dcache and possibly revalidates the found dentry.
1495 * NULL is returned if the dentry does not exist in the cache.
1497 static struct dentry
*lookup_dcache(const struct qstr
*name
,
1501 struct dentry
*dentry
= d_lookup(dir
, name
);
1503 int error
= d_revalidate(dentry
, flags
);
1504 if (unlikely(error
<= 0)) {
1506 d_invalidate(dentry
);
1508 return ERR_PTR(error
);
1515 * Parent directory has inode locked exclusive. This is one
1516 * and only case when ->lookup() gets called on non in-lookup
1517 * dentries - as the matter of fact, this only gets called
1518 * when directory is guaranteed to have no in-lookup children
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
);
1526 struct inode
*dir
= base
->d_inode
;
1531 /* Don't create child dentry for a dead directory. */
1532 if (unlikely(IS_DEADDIR(dir
)))
1533 return ERR_PTR(-ENOENT
);
1535 dentry
= d_alloc(base
, name
);
1536 if (unlikely(!dentry
))
1537 return ERR_PTR(-ENOMEM
);
1539 old
= dir
->i_op
->lookup(dir
, dentry
, flags
);
1540 if (unlikely(old
)) {
1547 static int lookup_fast(struct nameidata
*nd
,
1548 struct path
*path
, struct inode
**inode
,
1551 struct vfsmount
*mnt
= nd
->path
.mnt
;
1552 struct dentry
*dentry
, *parent
= nd
->path
.dentry
;
1557 * Rename seqlock is not required here because in the off chance
1558 * of a false negative due to a concurrent rename, the caller is
1559 * going to fall back to non-racy lookup.
1561 if (nd
->flags
& LOOKUP_RCU
) {
1564 dentry
= __d_lookup_rcu(parent
, &nd
->last
, &seq
);
1565 if (unlikely(!dentry
)) {
1566 if (unlazy_walk(nd
))
1572 * This sequence count validates that the inode matches
1573 * the dentry name information from lookup.
1575 *inode
= d_backing_inode(dentry
);
1576 negative
= d_is_negative(dentry
);
1577 if (unlikely(read_seqcount_retry(&dentry
->d_seq
, seq
)))
1581 * This sequence count validates that the parent had no
1582 * changes while we did the lookup of the dentry above.
1584 * The memory barrier in read_seqcount_begin of child is
1585 * enough, we can use __read_seqcount_retry here.
1587 if (unlikely(__read_seqcount_retry(&parent
->d_seq
, nd
->seq
)))
1591 status
= d_revalidate(dentry
, nd
->flags
);
1592 if (likely(status
> 0)) {
1594 * Note: do negative dentry check after revalidation in
1595 * case that drops it.
1597 if (unlikely(negative
))
1600 path
->dentry
= dentry
;
1601 if (likely(__follow_mount_rcu(nd
, path
, inode
, seqp
)))
1604 if (unlazy_child(nd
, dentry
, seq
))
1606 if (unlikely(status
== -ECHILD
))
1607 /* we'd been told to redo it in non-rcu mode */
1608 status
= d_revalidate(dentry
, nd
->flags
);
1610 dentry
= __d_lookup(parent
, &nd
->last
);
1611 if (unlikely(!dentry
))
1613 status
= d_revalidate(dentry
, nd
->flags
);
1615 if (unlikely(status
<= 0)) {
1617 d_invalidate(dentry
);
1621 if (unlikely(d_is_negative(dentry
))) {
1627 path
->dentry
= dentry
;
1628 err
= follow_managed(path
, nd
);
1629 if (likely(err
> 0))
1630 *inode
= d_backing_inode(path
->dentry
);
1634 /* Fast lookup failed, do it the slow way */
1635 static struct dentry
*__lookup_slow(const struct qstr
*name
,
1639 struct dentry
*dentry
, *old
;
1640 struct inode
*inode
= dir
->d_inode
;
1641 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq
);
1643 /* Don't go there if it's already dead */
1644 if (unlikely(IS_DEADDIR(inode
)))
1645 return ERR_PTR(-ENOENT
);
1647 dentry
= d_alloc_parallel(dir
, name
, &wq
);
1650 if (unlikely(!d_in_lookup(dentry
))) {
1651 if (!(flags
& LOOKUP_NO_REVAL
)) {
1652 int error
= d_revalidate(dentry
, flags
);
1653 if (unlikely(error
<= 0)) {
1655 d_invalidate(dentry
);
1660 dentry
= ERR_PTR(error
);
1664 old
= inode
->i_op
->lookup(inode
, dentry
, flags
);
1665 d_lookup_done(dentry
);
1666 if (unlikely(old
)) {
1674 static struct dentry
*lookup_slow(const struct qstr
*name
,
1678 struct inode
*inode
= dir
->d_inode
;
1680 inode_lock_shared(inode
);
1681 res
= __lookup_slow(name
, dir
, flags
);
1682 inode_unlock_shared(inode
);
1686 static inline int may_lookup(struct nameidata
*nd
)
1688 if (nd
->flags
& LOOKUP_RCU
) {
1689 int err
= inode_permission(nd
->inode
, MAY_EXEC
|MAY_NOT_BLOCK
);
1692 if (unlazy_walk(nd
))
1695 return inode_permission(nd
->inode
, MAY_EXEC
);
1698 static inline int handle_dots(struct nameidata
*nd
, int type
)
1700 if (type
== LAST_DOTDOT
) {
1703 if (nd
->flags
& LOOKUP_RCU
) {
1704 return follow_dotdot_rcu(nd
);
1706 return follow_dotdot(nd
);
1711 static int pick_link(struct nameidata
*nd
, struct path
*link
,
1712 struct inode
*inode
, unsigned seq
)
1716 if (unlikely(nd
->total_link_count
++ >= MAXSYMLINKS
)) {
1717 path_to_nameidata(link
, nd
);
1720 if (!(nd
->flags
& LOOKUP_RCU
)) {
1721 if (link
->mnt
== nd
->path
.mnt
)
1724 error
= nd_alloc_stack(nd
);
1725 if (unlikely(error
)) {
1726 if (error
== -ECHILD
) {
1727 if (unlikely(!legitimize_path(nd
, link
, seq
))) {
1730 nd
->flags
&= ~LOOKUP_RCU
;
1731 nd
->path
.mnt
= NULL
;
1732 nd
->path
.dentry
= NULL
;
1734 } else if (likely(unlazy_walk(nd
)) == 0)
1735 error
= nd_alloc_stack(nd
);
1743 last
= nd
->stack
+ nd
->depth
++;
1745 clear_delayed_call(&last
->done
);
1746 nd
->link_inode
= inode
;
1751 enum {WALK_FOLLOW
= 1, WALK_MORE
= 2};
1754 * Do we need to follow links? We _really_ want to be able
1755 * to do this check without having to look at inode->i_op,
1756 * so we keep a cache of "no, this doesn't need follow_link"
1757 * for the common case.
1759 static inline int step_into(struct nameidata
*nd
, struct path
*path
,
1760 int flags
, struct inode
*inode
, unsigned seq
)
1762 if (!(flags
& WALK_MORE
) && nd
->depth
)
1764 if (likely(!d_is_symlink(path
->dentry
)) ||
1765 !(flags
& WALK_FOLLOW
|| nd
->flags
& LOOKUP_FOLLOW
)) {
1766 /* not a symlink or should not follow */
1767 path_to_nameidata(path
, nd
);
1772 /* make sure that d_is_symlink above matches inode */
1773 if (nd
->flags
& LOOKUP_RCU
) {
1774 if (read_seqcount_retry(&path
->dentry
->d_seq
, seq
))
1777 return pick_link(nd
, path
, inode
, seq
);
1780 static int walk_component(struct nameidata
*nd
, int flags
)
1783 struct inode
*inode
;
1787 * "." and ".." are special - ".." especially so because it has
1788 * to be able to know about the current root directory and
1789 * parent relationships.
1791 if (unlikely(nd
->last_type
!= LAST_NORM
)) {
1792 err
= handle_dots(nd
, nd
->last_type
);
1793 if (!(flags
& WALK_MORE
) && nd
->depth
)
1797 err
= lookup_fast(nd
, &path
, &inode
, &seq
);
1798 if (unlikely(err
<= 0)) {
1801 path
.dentry
= lookup_slow(&nd
->last
, nd
->path
.dentry
,
1803 if (IS_ERR(path
.dentry
))
1804 return PTR_ERR(path
.dentry
);
1806 path
.mnt
= nd
->path
.mnt
;
1807 err
= follow_managed(&path
, nd
);
1808 if (unlikely(err
< 0))
1811 if (unlikely(d_is_negative(path
.dentry
))) {
1812 path_to_nameidata(&path
, nd
);
1816 seq
= 0; /* we are already out of RCU mode */
1817 inode
= d_backing_inode(path
.dentry
);
1820 return step_into(nd
, &path
, flags
, inode
, seq
);
1824 * We can do the critical dentry name comparison and hashing
1825 * operations one word at a time, but we are limited to:
1827 * - Architectures with fast unaligned word accesses. We could
1828 * do a "get_unaligned()" if this helps and is sufficiently
1831 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
1832 * do not trap on the (extremely unlikely) case of a page
1833 * crossing operation.
1835 * - Furthermore, we need an efficient 64-bit compile for the
1836 * 64-bit case in order to generate the "number of bytes in
1837 * the final mask". Again, that could be replaced with a
1838 * efficient population count instruction or similar.
1840 #ifdef CONFIG_DCACHE_WORD_ACCESS
1842 #include <asm/word-at-a-time.h>
1846 /* Architecture provides HASH_MIX and fold_hash() in <asm/hash.h> */
1848 #elif defined(CONFIG_64BIT)
1850 * Register pressure in the mixing function is an issue, particularly
1851 * on 32-bit x86, but almost any function requires one state value and
1852 * one temporary. Instead, use a function designed for two state values
1853 * and no temporaries.
1855 * This function cannot create a collision in only two iterations, so
1856 * we have two iterations to achieve avalanche. In those two iterations,
1857 * we have six layers of mixing, which is enough to spread one bit's
1858 * influence out to 2^6 = 64 state bits.
1860 * Rotate constants are scored by considering either 64 one-bit input
1861 * deltas or 64*63/2 = 2016 two-bit input deltas, and finding the
1862 * probability of that delta causing a change to each of the 128 output
1863 * bits, using a sample of random initial states.
1865 * The Shannon entropy of the computed probabilities is then summed
1866 * to produce a score. Ideally, any input change has a 50% chance of
1867 * toggling any given output bit.
1869 * Mixing scores (in bits) for (12,45):
1870 * Input delta: 1-bit 2-bit
1871 * 1 round: 713.3 42542.6
1872 * 2 rounds: 2753.7 140389.8
1873 * 3 rounds: 5954.1 233458.2
1874 * 4 rounds: 7862.6 256672.2
1875 * Perfect: 8192 258048
1876 * (64*128) (64*63/2 * 128)
1878 #define HASH_MIX(x, y, a) \
1880 y ^= x, x = rol64(x,12),\
1881 x += y, y = rol64(y,45),\
1885 * Fold two longs into one 32-bit hash value. This must be fast, but
1886 * latency isn't quite as critical, as there is a fair bit of additional
1887 * work done before the hash value is used.
1889 static inline unsigned int fold_hash(unsigned long x
, unsigned long y
)
1891 y
^= x
* GOLDEN_RATIO_64
;
1892 y
*= GOLDEN_RATIO_64
;
1896 #else /* 32-bit case */
1899 * Mixing scores (in bits) for (7,20):
1900 * Input delta: 1-bit 2-bit
1901 * 1 round: 330.3 9201.6
1902 * 2 rounds: 1246.4 25475.4
1903 * 3 rounds: 1907.1 31295.1
1904 * 4 rounds: 2042.3 31718.6
1905 * Perfect: 2048 31744
1906 * (32*64) (32*31/2 * 64)
1908 #define HASH_MIX(x, y, a) \
1910 y ^= x, x = rol32(x, 7),\
1911 x += y, y = rol32(y,20),\
1914 static inline unsigned int fold_hash(unsigned long x
, unsigned long y
)
1916 /* Use arch-optimized multiply if one exists */
1917 return __hash_32(y
^ __hash_32(x
));
1923 * Return the hash of a string of known length. This is carfully
1924 * designed to match hash_name(), which is the more critical function.
1925 * In particular, we must end by hashing a final word containing 0..7
1926 * payload bytes, to match the way that hash_name() iterates until it
1927 * finds the delimiter after the name.
1929 unsigned int full_name_hash(const void *salt
, const char *name
, unsigned int len
)
1931 unsigned long a
, x
= 0, y
= (unsigned long)salt
;
1936 a
= load_unaligned_zeropad(name
);
1937 if (len
< sizeof(unsigned long))
1940 name
+= sizeof(unsigned long);
1941 len
-= sizeof(unsigned long);
1943 x
^= a
& bytemask_from_count(len
);
1945 return fold_hash(x
, y
);
1947 EXPORT_SYMBOL(full_name_hash
);
1949 /* Return the "hash_len" (hash and length) of a null-terminated string */
1950 u64
hashlen_string(const void *salt
, const char *name
)
1952 unsigned long a
= 0, x
= 0, y
= (unsigned long)salt
;
1953 unsigned long adata
, mask
, len
;
1954 const struct word_at_a_time constants
= WORD_AT_A_TIME_CONSTANTS
;
1961 len
+= sizeof(unsigned long);
1963 a
= load_unaligned_zeropad(name
+len
);
1964 } while (!has_zero(a
, &adata
, &constants
));
1966 adata
= prep_zero_mask(a
, adata
, &constants
);
1967 mask
= create_zero_mask(adata
);
1968 x
^= a
& zero_bytemask(mask
);
1970 return hashlen_create(fold_hash(x
, y
), len
+ find_zero(mask
));
1972 EXPORT_SYMBOL(hashlen_string
);
1975 * Calculate the length and hash of the path component, and
1976 * return the "hash_len" as the result.
1978 static inline u64
hash_name(const void *salt
, const char *name
)
1980 unsigned long a
= 0, b
, x
= 0, y
= (unsigned long)salt
;
1981 unsigned long adata
, bdata
, mask
, len
;
1982 const struct word_at_a_time constants
= WORD_AT_A_TIME_CONSTANTS
;
1989 len
+= sizeof(unsigned long);
1991 a
= load_unaligned_zeropad(name
+len
);
1992 b
= a
^ REPEAT_BYTE('/');
1993 } while (!(has_zero(a
, &adata
, &constants
) | has_zero(b
, &bdata
, &constants
)));
1995 adata
= prep_zero_mask(a
, adata
, &constants
);
1996 bdata
= prep_zero_mask(b
, bdata
, &constants
);
1997 mask
= create_zero_mask(adata
| bdata
);
1998 x
^= a
& zero_bytemask(mask
);
2000 return hashlen_create(fold_hash(x
, y
), len
+ find_zero(mask
));
2003 #else /* !CONFIG_DCACHE_WORD_ACCESS: Slow, byte-at-a-time version */
2005 /* Return the hash of a string of known length */
2006 unsigned int full_name_hash(const void *salt
, const char *name
, unsigned int len
)
2008 unsigned long hash
= init_name_hash(salt
);
2010 hash
= partial_name_hash((unsigned char)*name
++, hash
);
2011 return end_name_hash(hash
);
2013 EXPORT_SYMBOL(full_name_hash
);
2015 /* Return the "hash_len" (hash and length) of a null-terminated string */
2016 u64
hashlen_string(const void *salt
, const char *name
)
2018 unsigned long hash
= init_name_hash(salt
);
2019 unsigned long len
= 0, c
;
2021 c
= (unsigned char)*name
;
2024 hash
= partial_name_hash(c
, hash
);
2025 c
= (unsigned char)name
[len
];
2027 return hashlen_create(end_name_hash(hash
), len
);
2029 EXPORT_SYMBOL(hashlen_string
);
2032 * We know there's a real path component here of at least
2035 static inline u64
hash_name(const void *salt
, const char *name
)
2037 unsigned long hash
= init_name_hash(salt
);
2038 unsigned long len
= 0, c
;
2040 c
= (unsigned char)*name
;
2043 hash
= partial_name_hash(c
, hash
);
2044 c
= (unsigned char)name
[len
];
2045 } while (c
&& c
!= '/');
2046 return hashlen_create(end_name_hash(hash
), len
);
2053 * This is the basic name resolution function, turning a pathname into
2054 * the final dentry. We expect 'base' to be positive and a directory.
2056 * Returns 0 and nd will have valid dentry and mnt on success.
2057 * Returns error and drops reference to input namei data on failure.
2059 static int link_path_walk(const char *name
, struct nameidata
*nd
)
2064 return PTR_ERR(name
);
2070 /* At this point we know we have a real path component. */
2075 err
= may_lookup(nd
);
2079 hash_len
= hash_name(nd
->path
.dentry
, name
);
2082 if (name
[0] == '.') switch (hashlen_len(hash_len
)) {
2084 if (name
[1] == '.') {
2086 nd
->flags
|= LOOKUP_JUMPED
;
2092 if (likely(type
== LAST_NORM
)) {
2093 struct dentry
*parent
= nd
->path
.dentry
;
2094 nd
->flags
&= ~LOOKUP_JUMPED
;
2095 if (unlikely(parent
->d_flags
& DCACHE_OP_HASH
)) {
2096 struct qstr
this = { { .hash_len
= hash_len
}, .name
= name
};
2097 err
= parent
->d_op
->d_hash(parent
, &this);
2100 hash_len
= this.hash_len
;
2105 nd
->last
.hash_len
= hash_len
;
2106 nd
->last
.name
= name
;
2107 nd
->last_type
= type
;
2109 name
+= hashlen_len(hash_len
);
2113 * If it wasn't NUL, we know it was '/'. Skip that
2114 * slash, and continue until no more slashes.
2118 } while (unlikely(*name
== '/'));
2119 if (unlikely(!*name
)) {
2121 /* pathname body, done */
2124 name
= nd
->stack
[nd
->depth
- 1].name
;
2125 /* trailing symlink, done */
2128 /* last component of nested symlink */
2129 err
= walk_component(nd
, WALK_FOLLOW
);
2131 /* not the last component */
2132 err
= walk_component(nd
, WALK_FOLLOW
| WALK_MORE
);
2138 const char *s
= get_link(nd
);
2147 nd
->stack
[nd
->depth
- 1].name
= name
;
2152 if (unlikely(!d_can_lookup(nd
->path
.dentry
))) {
2153 if (nd
->flags
& LOOKUP_RCU
) {
2154 if (unlazy_walk(nd
))
2162 /* must be paired with terminate_walk() */
2163 static const char *path_init(struct nameidata
*nd
, unsigned flags
)
2165 const char *s
= nd
->name
->name
;
2168 flags
&= ~LOOKUP_RCU
;
2169 if (flags
& LOOKUP_RCU
)
2172 nd
->last_type
= LAST_ROOT
; /* if there are only slashes... */
2173 nd
->flags
= flags
| LOOKUP_JUMPED
| LOOKUP_PARENT
;
2175 if (flags
& LOOKUP_ROOT
) {
2176 struct dentry
*root
= nd
->root
.dentry
;
2177 struct inode
*inode
= root
->d_inode
;
2178 if (*s
&& unlikely(!d_can_lookup(root
)))
2179 return ERR_PTR(-ENOTDIR
);
2180 nd
->path
= nd
->root
;
2182 if (flags
& LOOKUP_RCU
) {
2183 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
2184 nd
->root_seq
= nd
->seq
;
2185 nd
->m_seq
= read_seqbegin(&mount_lock
);
2187 path_get(&nd
->path
);
2192 nd
->root
.mnt
= NULL
;
2193 nd
->path
.mnt
= NULL
;
2194 nd
->path
.dentry
= NULL
;
2196 nd
->m_seq
= read_seqbegin(&mount_lock
);
2199 if (likely(!nd_jump_root(nd
)))
2201 return ERR_PTR(-ECHILD
);
2202 } else if (nd
->dfd
== AT_FDCWD
) {
2203 if (flags
& LOOKUP_RCU
) {
2204 struct fs_struct
*fs
= current
->fs
;
2208 seq
= read_seqcount_begin(&fs
->seq
);
2210 nd
->inode
= nd
->path
.dentry
->d_inode
;
2211 nd
->seq
= __read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
2212 } while (read_seqcount_retry(&fs
->seq
, seq
));
2214 get_fs_pwd(current
->fs
, &nd
->path
);
2215 nd
->inode
= nd
->path
.dentry
->d_inode
;
2219 /* Caller must check execute permissions on the starting path component */
2220 struct fd f
= fdget_raw(nd
->dfd
);
2221 struct dentry
*dentry
;
2224 return ERR_PTR(-EBADF
);
2226 dentry
= f
.file
->f_path
.dentry
;
2228 if (*s
&& unlikely(!d_can_lookup(dentry
))) {
2230 return ERR_PTR(-ENOTDIR
);
2233 nd
->path
= f
.file
->f_path
;
2234 if (flags
& LOOKUP_RCU
) {
2235 nd
->inode
= nd
->path
.dentry
->d_inode
;
2236 nd
->seq
= read_seqcount_begin(&nd
->path
.dentry
->d_seq
);
2238 path_get(&nd
->path
);
2239 nd
->inode
= nd
->path
.dentry
->d_inode
;
2246 static const char *trailing_symlink(struct nameidata
*nd
)
2249 int error
= may_follow_link(nd
);
2250 if (unlikely(error
))
2251 return ERR_PTR(error
);
2252 nd
->flags
|= LOOKUP_PARENT
;
2253 nd
->stack
[0].name
= NULL
;
2258 static inline int lookup_last(struct nameidata
*nd
)
2260 if (nd
->last_type
== LAST_NORM
&& nd
->last
.name
[nd
->last
.len
])
2261 nd
->flags
|= LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
;
2263 nd
->flags
&= ~LOOKUP_PARENT
;
2264 return walk_component(nd
, 0);
2267 static int handle_lookup_down(struct nameidata
*nd
)
2269 struct path path
= nd
->path
;
2270 struct inode
*inode
= nd
->inode
;
2271 unsigned seq
= nd
->seq
;
2274 if (nd
->flags
& LOOKUP_RCU
) {
2276 * don't bother with unlazy_walk on failure - we are
2277 * at the very beginning of walk, so we lose nothing
2278 * if we simply redo everything in non-RCU mode
2280 if (unlikely(!__follow_mount_rcu(nd
, &path
, &inode
, &seq
)))
2284 err
= follow_managed(&path
, nd
);
2285 if (unlikely(err
< 0))
2287 inode
= d_backing_inode(path
.dentry
);
2290 path_to_nameidata(&path
, nd
);
2296 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
2297 static int path_lookupat(struct nameidata
*nd
, unsigned flags
, struct path
*path
)
2299 const char *s
= path_init(nd
, flags
);
2302 if (unlikely(flags
& LOOKUP_DOWN
) && !IS_ERR(s
)) {
2303 err
= handle_lookup_down(nd
);
2304 if (unlikely(err
< 0))
2308 while (!(err
= link_path_walk(s
, nd
))
2309 && ((err
= lookup_last(nd
)) > 0)) {
2310 s
= trailing_symlink(nd
);
2313 err
= complete_walk(nd
);
2315 if (!err
&& nd
->flags
& LOOKUP_DIRECTORY
)
2316 if (!d_can_lookup(nd
->path
.dentry
))
2320 nd
->path
.mnt
= NULL
;
2321 nd
->path
.dentry
= NULL
;
2327 int filename_lookup(int dfd
, struct filename
*name
, unsigned flags
,
2328 struct path
*path
, struct path
*root
)
2331 struct nameidata nd
;
2333 return PTR_ERR(name
);
2334 if (unlikely(root
)) {
2336 flags
|= LOOKUP_ROOT
;
2338 set_nameidata(&nd
, dfd
, name
);
2339 retval
= path_lookupat(&nd
, flags
| LOOKUP_RCU
, path
);
2340 if (unlikely(retval
== -ECHILD
))
2341 retval
= path_lookupat(&nd
, flags
, path
);
2342 if (unlikely(retval
== -ESTALE
))
2343 retval
= path_lookupat(&nd
, flags
| LOOKUP_REVAL
, path
);
2345 if (likely(!retval
))
2346 audit_inode(name
, path
->dentry
, 0);
2347 restore_nameidata();
2352 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
2353 static int path_parentat(struct nameidata
*nd
, unsigned flags
,
2354 struct path
*parent
)
2356 const char *s
= path_init(nd
, flags
);
2357 int err
= link_path_walk(s
, nd
);
2359 err
= complete_walk(nd
);
2362 nd
->path
.mnt
= NULL
;
2363 nd
->path
.dentry
= NULL
;
2369 static struct filename
*filename_parentat(int dfd
, struct filename
*name
,
2370 unsigned int flags
, struct path
*parent
,
2371 struct qstr
*last
, int *type
)
2374 struct nameidata nd
;
2378 set_nameidata(&nd
, dfd
, name
);
2379 retval
= path_parentat(&nd
, flags
| LOOKUP_RCU
, parent
);
2380 if (unlikely(retval
== -ECHILD
))
2381 retval
= path_parentat(&nd
, flags
, parent
);
2382 if (unlikely(retval
== -ESTALE
))
2383 retval
= path_parentat(&nd
, flags
| LOOKUP_REVAL
, parent
);
2384 if (likely(!retval
)) {
2386 *type
= nd
.last_type
;
2387 audit_inode(name
, parent
->dentry
, AUDIT_INODE_PARENT
);
2390 name
= ERR_PTR(retval
);
2392 restore_nameidata();
2396 /* does lookup, returns the object with parent locked */
2397 struct dentry
*kern_path_locked(const char *name
, struct path
*path
)
2399 struct filename
*filename
;
2404 filename
= filename_parentat(AT_FDCWD
, getname_kernel(name
), 0, path
,
2406 if (IS_ERR(filename
))
2407 return ERR_CAST(filename
);
2408 if (unlikely(type
!= LAST_NORM
)) {
2411 return ERR_PTR(-EINVAL
);
2413 inode_lock_nested(path
->dentry
->d_inode
, I_MUTEX_PARENT
);
2414 d
= __lookup_hash(&last
, path
->dentry
, 0);
2416 inode_unlock(path
->dentry
->d_inode
);
2423 int kern_path(const char *name
, unsigned int flags
, struct path
*path
)
2425 return filename_lookup(AT_FDCWD
, getname_kernel(name
),
2428 EXPORT_SYMBOL(kern_path
);
2431 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
2432 * @dentry: pointer to dentry of the base directory
2433 * @mnt: pointer to vfs mount of the base directory
2434 * @name: pointer to file name
2435 * @flags: lookup flags
2436 * @path: pointer to struct path to fill
2438 int vfs_path_lookup(struct dentry
*dentry
, struct vfsmount
*mnt
,
2439 const char *name
, unsigned int flags
,
2442 struct path root
= {.mnt
= mnt
, .dentry
= dentry
};
2443 /* the first argument of filename_lookup() is ignored with root */
2444 return filename_lookup(AT_FDCWD
, getname_kernel(name
),
2445 flags
, path
, &root
);
2447 EXPORT_SYMBOL(vfs_path_lookup
);
2449 static int lookup_one_len_common(const char *name
, struct dentry
*base
,
2450 int len
, struct qstr
*this)
2454 this->hash
= full_name_hash(base
, name
, len
);
2458 if (unlikely(name
[0] == '.')) {
2459 if (len
< 2 || (len
== 2 && name
[1] == '.'))
2464 unsigned int c
= *(const unsigned char *)name
++;
2465 if (c
== '/' || c
== '\0')
2469 * See if the low-level filesystem might want
2470 * to use its own hash..
2472 if (base
->d_flags
& DCACHE_OP_HASH
) {
2473 int err
= base
->d_op
->d_hash(base
, this);
2478 return inode_permission(base
->d_inode
, MAY_EXEC
);
2482 * try_lookup_one_len - filesystem helper to lookup single pathname component
2483 * @name: pathname component to lookup
2484 * @base: base directory to lookup from
2485 * @len: maximum length @len should be interpreted to
2487 * Look up a dentry by name in the dcache, returning NULL if it does not
2488 * currently exist. The function does not try to create a dentry.
2490 * Note that this routine is purely a helper for filesystem usage and should
2491 * not be called by generic code.
2493 * The caller must hold base->i_mutex.
2495 struct dentry
*try_lookup_one_len(const char *name
, struct dentry
*base
, int len
)
2500 WARN_ON_ONCE(!inode_is_locked(base
->d_inode
));
2502 err
= lookup_one_len_common(name
, base
, len
, &this);
2504 return ERR_PTR(err
);
2506 return lookup_dcache(&this, base
, 0);
2508 EXPORT_SYMBOL(try_lookup_one_len
);
2511 * lookup_one_len - filesystem helper to lookup single pathname component
2512 * @name: pathname component to lookup
2513 * @base: base directory to lookup from
2514 * @len: maximum length @len should be interpreted to
2516 * Note that this routine is purely a helper for filesystem usage and should
2517 * not be called by generic code.
2519 * The caller must hold base->i_mutex.
2521 struct dentry
*lookup_one_len(const char *name
, struct dentry
*base
, int len
)
2523 struct dentry
*dentry
;
2527 WARN_ON_ONCE(!inode_is_locked(base
->d_inode
));
2529 err
= lookup_one_len_common(name
, base
, len
, &this);
2531 return ERR_PTR(err
);
2533 dentry
= lookup_dcache(&this, base
, 0);
2534 return dentry
? dentry
: __lookup_slow(&this, base
, 0);
2536 EXPORT_SYMBOL(lookup_one_len
);
2539 * lookup_one_len_unlocked - filesystem helper to lookup single pathname component
2540 * @name: pathname component to lookup
2541 * @base: base directory to lookup from
2542 * @len: maximum length @len should be interpreted to
2544 * Note that this routine is purely a helper for filesystem usage and should
2545 * not be called by generic code.
2547 * Unlike lookup_one_len, it should be called without the parent
2548 * i_mutex held, and will take the i_mutex itself if necessary.
2550 struct dentry
*lookup_one_len_unlocked(const char *name
,
2551 struct dentry
*base
, int len
)
2557 err
= lookup_one_len_common(name
, base
, len
, &this);
2559 return ERR_PTR(err
);
2561 ret
= lookup_dcache(&this, base
, 0);
2563 ret
= lookup_slow(&this, base
, 0);
2566 EXPORT_SYMBOL(lookup_one_len_unlocked
);
2568 #ifdef CONFIG_UNIX98_PTYS
2569 int path_pts(struct path
*path
)
2571 /* Find something mounted on "pts" in the same directory as
2574 struct dentry
*child
, *parent
;
2578 ret
= path_parent_directory(path
);
2582 parent
= path
->dentry
;
2585 child
= d_hash_and_lookup(parent
, &this);
2589 path
->dentry
= child
;
2596 int user_path_at_empty(int dfd
, const char __user
*name
, unsigned flags
,
2597 struct path
*path
, int *empty
)
2599 return filename_lookup(dfd
, getname_flags(name
, flags
, empty
),
2602 EXPORT_SYMBOL(user_path_at_empty
);
2605 * mountpoint_last - look up last component for umount
2606 * @nd: pathwalk nameidata - currently pointing at parent directory of "last"
2608 * This is a special lookup_last function just for umount. In this case, we
2609 * need to resolve the path without doing any revalidation.
2611 * The nameidata should be the result of doing a LOOKUP_PARENT pathwalk. Since
2612 * mountpoints are always pinned in the dcache, their ancestors are too. Thus,
2613 * in almost all cases, this lookup will be served out of the dcache. The only
2614 * cases where it won't are if nd->last refers to a symlink or the path is
2615 * bogus and it doesn't exist.
2618 * -error: if there was an error during lookup. This includes -ENOENT if the
2619 * lookup found a negative dentry.
2621 * 0: if we successfully resolved nd->last and found it to not to be a
2622 * symlink that needs to be followed.
2624 * 1: if we successfully resolved nd->last and found it to be a symlink
2625 * that needs to be followed.
2628 mountpoint_last(struct nameidata
*nd
)
2631 struct dentry
*dir
= nd
->path
.dentry
;
2634 /* If we're in rcuwalk, drop out of it to handle last component */
2635 if (nd
->flags
& LOOKUP_RCU
) {
2636 if (unlazy_walk(nd
))
2640 nd
->flags
&= ~LOOKUP_PARENT
;
2642 if (unlikely(nd
->last_type
!= LAST_NORM
)) {
2643 error
= handle_dots(nd
, nd
->last_type
);
2646 path
.dentry
= dget(nd
->path
.dentry
);
2648 path
.dentry
= d_lookup(dir
, &nd
->last
);
2651 * No cached dentry. Mounted dentries are pinned in the
2652 * cache, so that means that this dentry is probably
2653 * a symlink or the path doesn't actually point
2654 * to a mounted dentry.
2656 path
.dentry
= lookup_slow(&nd
->last
, dir
,
2657 nd
->flags
| LOOKUP_NO_REVAL
);
2658 if (IS_ERR(path
.dentry
))
2659 return PTR_ERR(path
.dentry
);
2662 if (d_is_negative(path
.dentry
)) {
2666 path
.mnt
= nd
->path
.mnt
;
2667 return step_into(nd
, &path
, 0, d_backing_inode(path
.dentry
), 0);
2671 * path_mountpoint - look up a path to be umounted
2672 * @nd: lookup context
2673 * @flags: lookup flags
2674 * @path: pointer to container for result
2676 * Look up the given name, but don't attempt to revalidate the last component.
2677 * Returns 0 and "path" will be valid on success; Returns error otherwise.
2680 path_mountpoint(struct nameidata
*nd
, unsigned flags
, struct path
*path
)
2682 const char *s
= path_init(nd
, flags
);
2685 while (!(err
= link_path_walk(s
, nd
)) &&
2686 (err
= mountpoint_last(nd
)) > 0) {
2687 s
= trailing_symlink(nd
);
2691 nd
->path
.mnt
= NULL
;
2692 nd
->path
.dentry
= NULL
;
2700 filename_mountpoint(int dfd
, struct filename
*name
, struct path
*path
,
2703 struct nameidata nd
;
2706 return PTR_ERR(name
);
2707 set_nameidata(&nd
, dfd
, name
);
2708 error
= path_mountpoint(&nd
, flags
| LOOKUP_RCU
, path
);
2709 if (unlikely(error
== -ECHILD
))
2710 error
= path_mountpoint(&nd
, flags
, path
);
2711 if (unlikely(error
== -ESTALE
))
2712 error
= path_mountpoint(&nd
, flags
| LOOKUP_REVAL
, path
);
2714 audit_inode(name
, path
->dentry
, AUDIT_INODE_NOEVAL
);
2715 restore_nameidata();
2721 * user_path_mountpoint_at - lookup a path from userland in order to umount it
2722 * @dfd: directory file descriptor
2723 * @name: pathname from userland
2724 * @flags: lookup flags
2725 * @path: pointer to container to hold result
2727 * A umount is a special case for path walking. We're not actually interested
2728 * in the inode in this situation, and ESTALE errors can be a problem. We
2729 * simply want track down the dentry and vfsmount attached at the mountpoint
2730 * and avoid revalidating the last component.
2732 * Returns 0 and populates "path" on success.
2735 user_path_mountpoint_at(int dfd
, const char __user
*name
, unsigned int flags
,
2738 return filename_mountpoint(dfd
, getname(name
), path
, flags
);
2742 kern_path_mountpoint(int dfd
, const char *name
, struct path
*path
,
2745 return filename_mountpoint(dfd
, getname_kernel(name
), path
, flags
);
2747 EXPORT_SYMBOL(kern_path_mountpoint
);
2749 int __check_sticky(struct inode
*dir
, struct inode
*inode
)
2751 kuid_t fsuid
= current_fsuid();
2753 if (uid_eq(inode
->i_uid
, fsuid
))
2755 if (uid_eq(dir
->i_uid
, fsuid
))
2757 return !capable_wrt_inode_uidgid(inode
, CAP_FOWNER
);
2759 EXPORT_SYMBOL(__check_sticky
);
2762 * Check whether we can remove a link victim from directory dir, check
2763 * whether the type of victim is right.
2764 * 1. We can't do it if dir is read-only (done in permission())
2765 * 2. We should have write and exec permissions on dir
2766 * 3. We can't remove anything from append-only dir
2767 * 4. We can't do anything with immutable dir (done in permission())
2768 * 5. If the sticky bit on dir is set we should either
2769 * a. be owner of dir, or
2770 * b. be owner of victim, or
2771 * c. have CAP_FOWNER capability
2772 * 6. If the victim is append-only or immutable we can't do antyhing with
2773 * links pointing to it.
2774 * 7. If the victim has an unknown uid or gid we can't change the inode.
2775 * 8. If we were asked to remove a directory and victim isn't one - ENOTDIR.
2776 * 9. If we were asked to remove a non-directory and victim isn't one - EISDIR.
2777 * 10. We can't remove a root or mountpoint.
2778 * 11. We don't allow removal of NFS sillyrenamed files; it's handled by
2779 * nfs_async_unlink().
2781 static int may_delete(struct inode
*dir
, struct dentry
*victim
, bool isdir
)
2783 struct inode
*inode
= d_backing_inode(victim
);
2786 if (d_is_negative(victim
))
2790 BUG_ON(victim
->d_parent
->d_inode
!= dir
);
2792 /* Inode writeback is not safe when the uid or gid are invalid. */
2793 if (!uid_valid(inode
->i_uid
) || !gid_valid(inode
->i_gid
))
2796 audit_inode_child(dir
, victim
, AUDIT_TYPE_CHILD_DELETE
);
2798 error
= inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
2804 if (check_sticky(dir
, inode
) || IS_APPEND(inode
) ||
2805 IS_IMMUTABLE(inode
) || IS_SWAPFILE(inode
) || HAS_UNMAPPED_ID(inode
))
2808 if (!d_is_dir(victim
))
2810 if (IS_ROOT(victim
))
2812 } else if (d_is_dir(victim
))
2814 if (IS_DEADDIR(dir
))
2816 if (victim
->d_flags
& DCACHE_NFSFS_RENAMED
)
2821 /* Check whether we can create an object with dentry child in directory
2823 * 1. We can't do it if child already exists (open has special treatment for
2824 * this case, but since we are inlined it's OK)
2825 * 2. We can't do it if dir is read-only (done in permission())
2826 * 3. We can't do it if the fs can't represent the fsuid or fsgid.
2827 * 4. We should have write and exec permissions on dir
2828 * 5. We can't do it if dir is immutable (done in permission())
2830 static inline int may_create(struct inode
*dir
, struct dentry
*child
)
2832 struct user_namespace
*s_user_ns
;
2833 audit_inode_child(dir
, child
, AUDIT_TYPE_CHILD_CREATE
);
2836 if (IS_DEADDIR(dir
))
2838 s_user_ns
= dir
->i_sb
->s_user_ns
;
2839 if (!kuid_has_mapping(s_user_ns
, current_fsuid()) ||
2840 !kgid_has_mapping(s_user_ns
, current_fsgid()))
2842 return inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
2846 * p1 and p2 should be directories on the same fs.
2848 struct dentry
*lock_rename(struct dentry
*p1
, struct dentry
*p2
)
2853 inode_lock_nested(p1
->d_inode
, I_MUTEX_PARENT
);
2857 mutex_lock(&p1
->d_sb
->s_vfs_rename_mutex
);
2859 p
= d_ancestor(p2
, p1
);
2861 inode_lock_nested(p2
->d_inode
, I_MUTEX_PARENT
);
2862 inode_lock_nested(p1
->d_inode
, I_MUTEX_CHILD
);
2866 p
= d_ancestor(p1
, p2
);
2868 inode_lock_nested(p1
->d_inode
, I_MUTEX_PARENT
);
2869 inode_lock_nested(p2
->d_inode
, I_MUTEX_CHILD
);
2873 inode_lock_nested(p1
->d_inode
, I_MUTEX_PARENT
);
2874 inode_lock_nested(p2
->d_inode
, I_MUTEX_PARENT2
);
2877 EXPORT_SYMBOL(lock_rename
);
2879 void unlock_rename(struct dentry
*p1
, struct dentry
*p2
)
2881 inode_unlock(p1
->d_inode
);
2883 inode_unlock(p2
->d_inode
);
2884 mutex_unlock(&p1
->d_sb
->s_vfs_rename_mutex
);
2887 EXPORT_SYMBOL(unlock_rename
);
2889 int vfs_create(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
,
2892 int error
= may_create(dir
, dentry
);
2896 if (!dir
->i_op
->create
)
2897 return -EACCES
; /* shouldn't it be ENOSYS? */
2900 error
= security_inode_create(dir
, dentry
, mode
);
2903 error
= dir
->i_op
->create(dir
, dentry
, mode
, want_excl
);
2905 fsnotify_create(dir
, dentry
);
2908 EXPORT_SYMBOL(vfs_create
);
2910 int vfs_mkobj(struct dentry
*dentry
, umode_t mode
,
2911 int (*f
)(struct dentry
*, umode_t
, void *),
2914 struct inode
*dir
= dentry
->d_parent
->d_inode
;
2915 int error
= may_create(dir
, dentry
);
2921 error
= security_inode_create(dir
, dentry
, mode
);
2924 error
= f(dentry
, mode
, arg
);
2926 fsnotify_create(dir
, dentry
);
2929 EXPORT_SYMBOL(vfs_mkobj
);
2931 bool may_open_dev(const struct path
*path
)
2933 return !(path
->mnt
->mnt_flags
& MNT_NODEV
) &&
2934 !(path
->mnt
->mnt_sb
->s_iflags
& SB_I_NODEV
);
2937 static int may_open(const struct path
*path
, int acc_mode
, int flag
)
2939 struct dentry
*dentry
= path
->dentry
;
2940 struct inode
*inode
= dentry
->d_inode
;
2946 switch (inode
->i_mode
& S_IFMT
) {
2950 if (acc_mode
& MAY_WRITE
)
2955 if (!may_open_dev(path
))
2964 error
= inode_permission(inode
, MAY_OPEN
| acc_mode
);
2969 * An append-only file must be opened in append mode for writing.
2971 if (IS_APPEND(inode
)) {
2972 if ((flag
& O_ACCMODE
) != O_RDONLY
&& !(flag
& O_APPEND
))
2978 /* O_NOATIME can only be set by the owner or superuser */
2979 if (flag
& O_NOATIME
&& !inode_owner_or_capable(inode
))
2985 static int handle_truncate(struct file
*filp
)
2987 const struct path
*path
= &filp
->f_path
;
2988 struct inode
*inode
= path
->dentry
->d_inode
;
2989 int error
= get_write_access(inode
);
2993 * Refuse to truncate files with mandatory locks held on them.
2995 error
= locks_verify_locked(filp
);
2997 error
= security_path_truncate(path
);
2999 error
= do_truncate(path
->dentry
, 0,
3000 ATTR_MTIME
|ATTR_CTIME
|ATTR_OPEN
,
3003 put_write_access(inode
);
3007 static inline int open_to_namei_flags(int flag
)
3009 if ((flag
& O_ACCMODE
) == 3)
3014 static int may_o_create(const struct path
*dir
, struct dentry
*dentry
, umode_t mode
)
3016 struct user_namespace
*s_user_ns
;
3017 int error
= security_path_mknod(dir
, dentry
, mode
, 0);
3021 s_user_ns
= dir
->dentry
->d_sb
->s_user_ns
;
3022 if (!kuid_has_mapping(s_user_ns
, current_fsuid()) ||
3023 !kgid_has_mapping(s_user_ns
, current_fsgid()))
3026 error
= inode_permission(dir
->dentry
->d_inode
, MAY_WRITE
| MAY_EXEC
);
3030 return security_inode_create(dir
->dentry
->d_inode
, dentry
, mode
);
3034 * Attempt to atomically look up, create and open a file from a negative
3037 * Returns 0 if successful. The file will have been created and attached to
3038 * @file by the filesystem calling finish_open().
3040 * If the file was looked up only or didn't need creating, FMODE_OPENED won't
3041 * be set. The caller will need to perform the open themselves. @path will
3042 * have been updated to point to the new dentry. This may be negative.
3044 * Returns an error code otherwise.
3046 static int atomic_open(struct nameidata
*nd
, struct dentry
*dentry
,
3047 struct path
*path
, struct file
*file
,
3048 const struct open_flags
*op
,
3049 int open_flag
, umode_t mode
)
3051 struct dentry
*const DENTRY_NOT_SET
= (void *) -1UL;
3052 struct inode
*dir
= nd
->path
.dentry
->d_inode
;
3055 if (!(~open_flag
& (O_EXCL
| O_CREAT
))) /* both O_EXCL and O_CREAT */
3056 open_flag
&= ~O_TRUNC
;
3058 if (nd
->flags
& LOOKUP_DIRECTORY
)
3059 open_flag
|= O_DIRECTORY
;
3061 file
->f_path
.dentry
= DENTRY_NOT_SET
;
3062 file
->f_path
.mnt
= nd
->path
.mnt
;
3063 error
= dir
->i_op
->atomic_open(dir
, dentry
, file
,
3064 open_to_namei_flags(open_flag
), mode
);
3065 d_lookup_done(dentry
);
3067 if (file
->f_mode
& FMODE_OPENED
) {
3069 * We didn't have the inode before the open, so check open
3072 int acc_mode
= op
->acc_mode
;
3073 if (file
->f_mode
& FMODE_CREATED
) {
3074 WARN_ON(!(open_flag
& O_CREAT
));
3075 fsnotify_create(dir
, dentry
);
3078 error
= may_open(&file
->f_path
, acc_mode
, open_flag
);
3079 if (WARN_ON(error
> 0))
3081 } else if (WARN_ON(file
->f_path
.dentry
== DENTRY_NOT_SET
)) {
3084 if (file
->f_path
.dentry
) {
3086 dentry
= file
->f_path
.dentry
;
3088 if (file
->f_mode
& FMODE_CREATED
)
3089 fsnotify_create(dir
, dentry
);
3090 if (unlikely(d_is_negative(dentry
))) {
3093 path
->dentry
= dentry
;
3094 path
->mnt
= nd
->path
.mnt
;
3104 * Look up and maybe create and open the last component.
3106 * Must be called with parent locked (exclusive in O_CREAT case).
3108 * Returns 0 on success, that is, if
3109 * the file was successfully atomically created (if necessary) and opened, or
3110 * the file was not completely opened at this time, though lookups and
3111 * creations were performed.
3112 * These case are distinguished by presence of FMODE_OPENED on file->f_mode.
3113 * In the latter case dentry returned in @path might be negative if O_CREAT
3114 * hadn't been specified.
3116 * An error code is returned on failure.
3118 static int lookup_open(struct nameidata
*nd
, struct path
*path
,
3120 const struct open_flags
*op
,
3123 struct dentry
*dir
= nd
->path
.dentry
;
3124 struct inode
*dir_inode
= dir
->d_inode
;
3125 int open_flag
= op
->open_flag
;
3126 struct dentry
*dentry
;
3127 int error
, create_error
= 0;
3128 umode_t mode
= op
->mode
;
3129 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq
);
3131 if (unlikely(IS_DEADDIR(dir_inode
)))
3134 file
->f_mode
&= ~FMODE_CREATED
;
3135 dentry
= d_lookup(dir
, &nd
->last
);
3138 dentry
= d_alloc_parallel(dir
, &nd
->last
, &wq
);
3140 return PTR_ERR(dentry
);
3142 if (d_in_lookup(dentry
))
3145 error
= d_revalidate(dentry
, nd
->flags
);
3146 if (likely(error
> 0))
3150 d_invalidate(dentry
);
3154 if (dentry
->d_inode
) {
3155 /* Cached positive dentry: will open in f_op->open */
3160 * Checking write permission is tricky, bacuse we don't know if we are
3161 * going to actually need it: O_CREAT opens should work as long as the
3162 * file exists. But checking existence breaks atomicity. The trick is
3163 * to check access and if not granted clear O_CREAT from the flags.
3165 * Another problem is returing the "right" error value (e.g. for an
3166 * O_EXCL open we want to return EEXIST not EROFS).
3168 if (open_flag
& O_CREAT
) {
3169 if (!IS_POSIXACL(dir
->d_inode
))
3170 mode
&= ~current_umask();
3171 if (unlikely(!got_write
)) {
3172 create_error
= -EROFS
;
3173 open_flag
&= ~O_CREAT
;
3174 if (open_flag
& (O_EXCL
| O_TRUNC
))
3176 /* No side effects, safe to clear O_CREAT */
3178 create_error
= may_o_create(&nd
->path
, dentry
, mode
);
3180 open_flag
&= ~O_CREAT
;
3181 if (open_flag
& O_EXCL
)
3185 } else if ((open_flag
& (O_TRUNC
|O_WRONLY
|O_RDWR
)) &&
3186 unlikely(!got_write
)) {
3188 * No O_CREATE -> atomicity not a requirement -> fall
3189 * back to lookup + open
3194 if (dir_inode
->i_op
->atomic_open
) {
3195 error
= atomic_open(nd
, dentry
, path
, file
, op
, open_flag
,
3197 if (unlikely(error
== -ENOENT
) && create_error
)
3198 error
= create_error
;
3203 if (d_in_lookup(dentry
)) {
3204 struct dentry
*res
= dir_inode
->i_op
->lookup(dir_inode
, dentry
,
3206 d_lookup_done(dentry
);
3207 if (unlikely(res
)) {
3209 error
= PTR_ERR(res
);
3217 /* Negative dentry, just create the file */
3218 if (!dentry
->d_inode
&& (open_flag
& O_CREAT
)) {
3219 file
->f_mode
|= FMODE_CREATED
;
3220 audit_inode_child(dir_inode
, dentry
, AUDIT_TYPE_CHILD_CREATE
);
3221 if (!dir_inode
->i_op
->create
) {
3225 error
= dir_inode
->i_op
->create(dir_inode
, dentry
, mode
,
3226 open_flag
& O_EXCL
);
3229 fsnotify_create(dir_inode
, dentry
);
3231 if (unlikely(create_error
) && !dentry
->d_inode
) {
3232 error
= create_error
;
3236 path
->dentry
= dentry
;
3237 path
->mnt
= nd
->path
.mnt
;
3246 * Handle the last step of open()
3248 static int do_last(struct nameidata
*nd
,
3249 struct file
*file
, const struct open_flags
*op
)
3251 struct dentry
*dir
= nd
->path
.dentry
;
3252 kuid_t dir_uid
= nd
->inode
->i_uid
;
3253 umode_t dir_mode
= nd
->inode
->i_mode
;
3254 int open_flag
= op
->open_flag
;
3255 bool will_truncate
= (open_flag
& O_TRUNC
) != 0;
3256 bool got_write
= false;
3257 int acc_mode
= op
->acc_mode
;
3259 struct inode
*inode
;
3263 nd
->flags
&= ~LOOKUP_PARENT
;
3264 nd
->flags
|= op
->intent
;
3266 if (nd
->last_type
!= LAST_NORM
) {
3267 error
= handle_dots(nd
, nd
->last_type
);
3268 if (unlikely(error
))
3273 if (!(open_flag
& O_CREAT
)) {
3274 if (nd
->last
.name
[nd
->last
.len
])
3275 nd
->flags
|= LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
;
3276 /* we _can_ be in RCU mode here */
3277 error
= lookup_fast(nd
, &path
, &inode
, &seq
);
3278 if (likely(error
> 0))
3284 BUG_ON(nd
->inode
!= dir
->d_inode
);
3285 BUG_ON(nd
->flags
& LOOKUP_RCU
);
3287 /* create side of things */
3289 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED
3290 * has been cleared when we got to the last component we are
3293 error
= complete_walk(nd
);
3297 audit_inode(nd
->name
, dir
, AUDIT_INODE_PARENT
);
3298 /* trailing slashes? */
3299 if (unlikely(nd
->last
.name
[nd
->last
.len
]))
3303 if (open_flag
& (O_CREAT
| O_TRUNC
| O_WRONLY
| O_RDWR
)) {
3304 error
= mnt_want_write(nd
->path
.mnt
);
3308 * do _not_ fail yet - we might not need that or fail with
3309 * a different error; let lookup_open() decide; we'll be
3310 * dropping this one anyway.
3313 if (open_flag
& O_CREAT
)
3314 inode_lock(dir
->d_inode
);
3316 inode_lock_shared(dir
->d_inode
);
3317 error
= lookup_open(nd
, &path
, file
, op
, got_write
);
3318 if (open_flag
& O_CREAT
)
3319 inode_unlock(dir
->d_inode
);
3321 inode_unlock_shared(dir
->d_inode
);
3326 if (file
->f_mode
& FMODE_OPENED
) {
3327 if ((file
->f_mode
& FMODE_CREATED
) ||
3328 !S_ISREG(file_inode(file
)->i_mode
))
3329 will_truncate
= false;
3331 audit_inode(nd
->name
, file
->f_path
.dentry
, 0);
3335 if (file
->f_mode
& FMODE_CREATED
) {
3336 /* Don't check for write permission, don't truncate */
3337 open_flag
&= ~O_TRUNC
;
3338 will_truncate
= false;
3340 path_to_nameidata(&path
, nd
);
3341 goto finish_open_created
;
3345 * If atomic_open() acquired write access it is dropped now due to
3346 * possible mount and symlink following (this might be optimized away if
3350 mnt_drop_write(nd
->path
.mnt
);
3354 error
= follow_managed(&path
, nd
);
3355 if (unlikely(error
< 0))
3358 if (unlikely(d_is_negative(path
.dentry
))) {
3359 path_to_nameidata(&path
, nd
);
3364 * create/update audit record if it already exists.
3366 audit_inode(nd
->name
, path
.dentry
, 0);
3368 if (unlikely((open_flag
& (O_EXCL
| O_CREAT
)) == (O_EXCL
| O_CREAT
))) {
3369 path_to_nameidata(&path
, nd
);
3373 seq
= 0; /* out of RCU mode, so the value doesn't matter */
3374 inode
= d_backing_inode(path
.dentry
);
3376 error
= step_into(nd
, &path
, 0, inode
, seq
);
3377 if (unlikely(error
))
3380 /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
3381 error
= complete_walk(nd
);
3384 audit_inode(nd
->name
, nd
->path
.dentry
, 0);
3385 if (open_flag
& O_CREAT
) {
3387 if (d_is_dir(nd
->path
.dentry
))
3389 error
= may_create_in_sticky(dir_mode
, dir_uid
,
3390 d_backing_inode(nd
->path
.dentry
));
3391 if (unlikely(error
))
3395 if ((nd
->flags
& LOOKUP_DIRECTORY
) && !d_can_lookup(nd
->path
.dentry
))
3397 if (!d_is_reg(nd
->path
.dentry
))
3398 will_truncate
= false;
3400 if (will_truncate
) {
3401 error
= mnt_want_write(nd
->path
.mnt
);
3406 finish_open_created
:
3407 error
= may_open(&nd
->path
, acc_mode
, open_flag
);
3410 BUG_ON(file
->f_mode
& FMODE_OPENED
); /* once it's opened, it's opened */
3411 error
= vfs_open(&nd
->path
, file
);
3415 error
= ima_file_check(file
, op
->acc_mode
);
3416 if (!error
&& will_truncate
)
3417 error
= handle_truncate(file
);
3419 if (unlikely(error
> 0)) {
3424 mnt_drop_write(nd
->path
.mnt
);
3428 struct dentry
*vfs_tmpfile(struct dentry
*dentry
, umode_t mode
, int open_flag
)
3430 struct dentry
*child
= NULL
;
3431 struct inode
*dir
= dentry
->d_inode
;
3432 struct inode
*inode
;
3435 /* we want directory to be writable */
3436 error
= inode_permission(dir
, MAY_WRITE
| MAY_EXEC
);
3439 error
= -EOPNOTSUPP
;
3440 if (!dir
->i_op
->tmpfile
)
3443 child
= d_alloc(dentry
, &slash_name
);
3444 if (unlikely(!child
))
3446 error
= dir
->i_op
->tmpfile(dir
, child
, mode
);
3450 inode
= child
->d_inode
;
3451 if (unlikely(!inode
))
3453 if (!(open_flag
& O_EXCL
)) {
3454 spin_lock(&inode
->i_lock
);
3455 inode
->i_state
|= I_LINKABLE
;
3456 spin_unlock(&inode
->i_lock
);
3458 ima_post_create_tmpfile(inode
);
3463 return ERR_PTR(error
);
3465 EXPORT_SYMBOL(vfs_tmpfile
);
3467 static int do_tmpfile(struct nameidata
*nd
, unsigned flags
,
3468 const struct open_flags
*op
,
3471 struct dentry
*child
;
3473 int error
= path_lookupat(nd
, flags
| LOOKUP_DIRECTORY
, &path
);
3474 if (unlikely(error
))
3476 error
= mnt_want_write(path
.mnt
);
3477 if (unlikely(error
))
3479 child
= vfs_tmpfile(path
.dentry
, op
->mode
, op
->open_flag
);
3480 error
= PTR_ERR(child
);
3484 path
.dentry
= child
;
3485 audit_inode(nd
->name
, child
, 0);
3486 /* Don't check for other permissions, the inode was just created */
3487 error
= may_open(&path
, 0, op
->open_flag
);
3490 file
->f_path
.mnt
= path
.mnt
;
3491 error
= finish_open(file
, child
, NULL
);
3493 mnt_drop_write(path
.mnt
);
3499 static int do_o_path(struct nameidata
*nd
, unsigned flags
, struct file
*file
)
3502 int error
= path_lookupat(nd
, flags
, &path
);
3504 audit_inode(nd
->name
, path
.dentry
, 0);
3505 error
= vfs_open(&path
, file
);
3511 static struct file
*path_openat(struct nameidata
*nd
,
3512 const struct open_flags
*op
, unsigned flags
)
3517 file
= alloc_empty_file(op
->open_flag
, current_cred());
3521 if (unlikely(file
->f_flags
& __O_TMPFILE
)) {
3522 error
= do_tmpfile(nd
, flags
, op
, file
);
3523 } else if (unlikely(file
->f_flags
& O_PATH
)) {
3524 error
= do_o_path(nd
, flags
, file
);
3526 const char *s
= path_init(nd
, flags
);
3527 while (!(error
= link_path_walk(s
, nd
)) &&
3528 (error
= do_last(nd
, file
, op
)) > 0) {
3529 nd
->flags
&= ~(LOOKUP_OPEN
|LOOKUP_CREATE
|LOOKUP_EXCL
);
3530 s
= trailing_symlink(nd
);
3534 if (likely(!error
)) {
3535 if (likely(file
->f_mode
& FMODE_OPENED
))
3541 if (error
== -EOPENSTALE
) {
3542 if (flags
& LOOKUP_RCU
)
3547 return ERR_PTR(error
);
3550 struct file
*do_filp_open(int dfd
, struct filename
*pathname
,
3551 const struct open_flags
*op
)
3553 struct nameidata nd
;
3554 int flags
= op
->lookup_flags
;
3557 set_nameidata(&nd
, dfd
, pathname
);
3558 filp
= path_openat(&nd
, op
, flags
| LOOKUP_RCU
);
3559 if (unlikely(filp
== ERR_PTR(-ECHILD
)))
3560 filp
= path_openat(&nd
, op
, flags
);
3561 if (unlikely(filp
== ERR_PTR(-ESTALE
)))
3562 filp
= path_openat(&nd
, op
, flags
| LOOKUP_REVAL
);
3563 restore_nameidata();
3567 struct file
*do_file_open_root(struct dentry
*dentry
, struct vfsmount
*mnt
,
3568 const char *name
, const struct open_flags
*op
)
3570 struct nameidata nd
;
3572 struct filename
*filename
;
3573 int flags
= op
->lookup_flags
| LOOKUP_ROOT
;
3576 nd
.root
.dentry
= dentry
;
3578 if (d_is_symlink(dentry
) && op
->intent
& LOOKUP_OPEN
)
3579 return ERR_PTR(-ELOOP
);
3581 filename
= getname_kernel(name
);
3582 if (IS_ERR(filename
))
3583 return ERR_CAST(filename
);
3585 set_nameidata(&nd
, -1, filename
);
3586 file
= path_openat(&nd
, op
, flags
| LOOKUP_RCU
);
3587 if (unlikely(file
== ERR_PTR(-ECHILD
)))
3588 file
= path_openat(&nd
, op
, flags
);
3589 if (unlikely(file
== ERR_PTR(-ESTALE
)))
3590 file
= path_openat(&nd
, op
, flags
| LOOKUP_REVAL
);
3591 restore_nameidata();
3596 static struct dentry
*filename_create(int dfd
, struct filename
*name
,
3597 struct path
*path
, unsigned int lookup_flags
)
3599 struct dentry
*dentry
= ERR_PTR(-EEXIST
);
3604 bool is_dir
= (lookup_flags
& LOOKUP_DIRECTORY
);
3607 * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any
3608 * other flags passed in are ignored!
3610 lookup_flags
&= LOOKUP_REVAL
;
3612 name
= filename_parentat(dfd
, name
, lookup_flags
, path
, &last
, &type
);
3614 return ERR_CAST(name
);
3617 * Yucky last component or no last component at all?
3618 * (foo/., foo/.., /////)
3620 if (unlikely(type
!= LAST_NORM
))
3623 /* don't fail immediately if it's r/o, at least try to report other errors */
3624 err2
= mnt_want_write(path
->mnt
);
3626 * Do the final lookup.
3628 lookup_flags
|= LOOKUP_CREATE
| LOOKUP_EXCL
;
3629 inode_lock_nested(path
->dentry
->d_inode
, I_MUTEX_PARENT
);
3630 dentry
= __lookup_hash(&last
, path
->dentry
, lookup_flags
);
3635 if (d_is_positive(dentry
))
3639 * Special case - lookup gave negative, but... we had foo/bar/
3640 * From the vfs_mknod() POV we just have a negative dentry -
3641 * all is fine. Let's be bastards - you had / on the end, you've
3642 * been asking for (non-existent) directory. -ENOENT for you.
3644 if (unlikely(!is_dir
&& last
.name
[last
.len
])) {
3648 if (unlikely(err2
)) {
3656 dentry
= ERR_PTR(error
);
3658 inode_unlock(path
->dentry
->d_inode
);
3660 mnt_drop_write(path
->mnt
);
3667 struct dentry
*kern_path_create(int dfd
, const char *pathname
,
3668 struct path
*path
, unsigned int lookup_flags
)
3670 return filename_create(dfd
, getname_kernel(pathname
),
3671 path
, lookup_flags
);
3673 EXPORT_SYMBOL(kern_path_create
);
3675 void done_path_create(struct path
*path
, struct dentry
*dentry
)
3678 inode_unlock(path
->dentry
->d_inode
);
3679 mnt_drop_write(path
->mnt
);
3682 EXPORT_SYMBOL(done_path_create
);
3684 inline struct dentry
*user_path_create(int dfd
, const char __user
*pathname
,
3685 struct path
*path
, unsigned int lookup_flags
)
3687 return filename_create(dfd
, getname(pathname
), path
, lookup_flags
);
3689 EXPORT_SYMBOL(user_path_create
);
3691 int vfs_mknod(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
, dev_t dev
)
3693 int error
= may_create(dir
, dentry
);
3698 if ((S_ISCHR(mode
) || S_ISBLK(mode
)) && !capable(CAP_MKNOD
))
3701 if (!dir
->i_op
->mknod
)
3704 error
= devcgroup_inode_mknod(mode
, dev
);
3708 error
= security_inode_mknod(dir
, dentry
, mode
, dev
);
3712 error
= dir
->i_op
->mknod(dir
, dentry
, mode
, dev
);
3714 fsnotify_create(dir
, dentry
);
3717 EXPORT_SYMBOL(vfs_mknod
);
3719 static int may_mknod(umode_t mode
)
3721 switch (mode
& S_IFMT
) {
3727 case 0: /* zero mode translates to S_IFREG */
3736 long do_mknodat(int dfd
, const char __user
*filename
, umode_t mode
,
3739 struct dentry
*dentry
;
3742 unsigned int lookup_flags
= 0;
3744 error
= may_mknod(mode
);
3748 dentry
= user_path_create(dfd
, filename
, &path
, lookup_flags
);
3750 return PTR_ERR(dentry
);
3752 if (!IS_POSIXACL(path
.dentry
->d_inode
))
3753 mode
&= ~current_umask();
3754 error
= security_path_mknod(&path
, dentry
, mode
, dev
);
3757 switch (mode
& S_IFMT
) {
3758 case 0: case S_IFREG
:
3759 error
= vfs_create(path
.dentry
->d_inode
,dentry
,mode
,true);
3761 ima_post_path_mknod(dentry
);
3763 case S_IFCHR
: case S_IFBLK
:
3764 error
= vfs_mknod(path
.dentry
->d_inode
,dentry
,mode
,
3765 new_decode_dev(dev
));
3767 case S_IFIFO
: case S_IFSOCK
:
3768 error
= vfs_mknod(path
.dentry
->d_inode
,dentry
,mode
,0);
3772 done_path_create(&path
, dentry
);
3773 if (retry_estale(error
, lookup_flags
)) {
3774 lookup_flags
|= LOOKUP_REVAL
;
3780 SYSCALL_DEFINE4(mknodat
, int, dfd
, const char __user
*, filename
, umode_t
, mode
,
3783 return do_mknodat(dfd
, filename
, mode
, dev
);
3786 SYSCALL_DEFINE3(mknod
, const char __user
*, filename
, umode_t
, mode
, unsigned, dev
)
3788 return do_mknodat(AT_FDCWD
, filename
, mode
, dev
);
3791 int vfs_mkdir(struct inode
*dir
, struct dentry
*dentry
, umode_t mode
)
3793 int error
= may_create(dir
, dentry
);
3794 unsigned max_links
= dir
->i_sb
->s_max_links
;
3799 if (!dir
->i_op
->mkdir
)
3802 mode
&= (S_IRWXUGO
|S_ISVTX
);
3803 error
= security_inode_mkdir(dir
, dentry
, mode
);
3807 if (max_links
&& dir
->i_nlink
>= max_links
)
3810 error
= dir
->i_op
->mkdir(dir
, dentry
, mode
);
3812 fsnotify_mkdir(dir
, dentry
);
3815 EXPORT_SYMBOL(vfs_mkdir
);
3817 long do_mkdirat(int dfd
, const char __user
*pathname
, umode_t mode
)
3819 struct dentry
*dentry
;
3822 unsigned int lookup_flags
= LOOKUP_DIRECTORY
;
3825 dentry
= user_path_create(dfd
, pathname
, &path
, lookup_flags
);
3827 return PTR_ERR(dentry
);
3829 if (!IS_POSIXACL(path
.dentry
->d_inode
))
3830 mode
&= ~current_umask();
3831 error
= security_path_mkdir(&path
, dentry
, mode
);
3833 error
= vfs_mkdir(path
.dentry
->d_inode
, dentry
, mode
);
3834 done_path_create(&path
, dentry
);
3835 if (retry_estale(error
, lookup_flags
)) {
3836 lookup_flags
|= LOOKUP_REVAL
;
3842 SYSCALL_DEFINE3(mkdirat
, int, dfd
, const char __user
*, pathname
, umode_t
, mode
)
3844 return do_mkdirat(dfd
, pathname
, mode
);
3847 SYSCALL_DEFINE2(mkdir
, const char __user
*, pathname
, umode_t
, mode
)
3849 return do_mkdirat(AT_FDCWD
, pathname
, mode
);
3852 int vfs_rmdir(struct inode
*dir
, struct dentry
*dentry
)
3854 int error
= may_delete(dir
, dentry
, 1);
3859 if (!dir
->i_op
->rmdir
)
3863 inode_lock(dentry
->d_inode
);
3866 if (is_local_mountpoint(dentry
))
3869 error
= security_inode_rmdir(dir
, dentry
);
3873 error
= dir
->i_op
->rmdir(dir
, dentry
);
3877 shrink_dcache_parent(dentry
);
3878 dentry
->d_inode
->i_flags
|= S_DEAD
;
3880 detach_mounts(dentry
);
3881 fsnotify_rmdir(dir
, dentry
);
3884 inode_unlock(dentry
->d_inode
);
3890 EXPORT_SYMBOL(vfs_rmdir
);
3892 long do_rmdir(int dfd
, const char __user
*pathname
)
3895 struct filename
*name
;
3896 struct dentry
*dentry
;
3900 unsigned int lookup_flags
= 0;
3902 name
= filename_parentat(dfd
, getname(pathname
), lookup_flags
,
3903 &path
, &last
, &type
);
3905 return PTR_ERR(name
);
3919 error
= mnt_want_write(path
.mnt
);
3923 inode_lock_nested(path
.dentry
->d_inode
, I_MUTEX_PARENT
);
3924 dentry
= __lookup_hash(&last
, path
.dentry
, lookup_flags
);
3925 error
= PTR_ERR(dentry
);
3928 if (!dentry
->d_inode
) {
3932 error
= security_path_rmdir(&path
, dentry
);
3935 error
= vfs_rmdir(path
.dentry
->d_inode
, dentry
);
3939 inode_unlock(path
.dentry
->d_inode
);
3940 mnt_drop_write(path
.mnt
);
3944 if (retry_estale(error
, lookup_flags
)) {
3945 lookup_flags
|= LOOKUP_REVAL
;
3951 SYSCALL_DEFINE1(rmdir
, const char __user
*, pathname
)
3953 return do_rmdir(AT_FDCWD
, pathname
);
3957 * vfs_unlink - unlink a filesystem object
3958 * @dir: parent directory
3960 * @delegated_inode: returns victim inode, if the inode is delegated.
3962 * The caller must hold dir->i_mutex.
3964 * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and
3965 * return a reference to the inode in delegated_inode. The caller
3966 * should then break the delegation on that inode and retry. Because
3967 * breaking a delegation may take a long time, the caller should drop
3968 * dir->i_mutex before doing so.
3970 * Alternatively, a caller may pass NULL for delegated_inode. This may
3971 * be appropriate for callers that expect the underlying filesystem not
3972 * to be NFS exported.
3974 int vfs_unlink(struct inode
*dir
, struct dentry
*dentry
, struct inode
**delegated_inode
)
3976 struct inode
*target
= dentry
->d_inode
;
3977 int error
= may_delete(dir
, dentry
, 0);
3982 if (!dir
->i_op
->unlink
)
3986 if (is_local_mountpoint(dentry
))
3989 error
= security_inode_unlink(dir
, dentry
);
3991 error
= try_break_deleg(target
, delegated_inode
);
3994 error
= dir
->i_op
->unlink(dir
, dentry
);
3997 detach_mounts(dentry
);
3998 fsnotify_unlink(dir
, dentry
);
4003 inode_unlock(target
);
4005 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
4006 if (!error
&& !(dentry
->d_flags
& DCACHE_NFSFS_RENAMED
)) {
4007 fsnotify_link_count(target
);
4013 EXPORT_SYMBOL(vfs_unlink
);
4016 * Make sure that the actual truncation of the file will occur outside its
4017 * directory's i_mutex. Truncate can take a long time if there is a lot of
4018 * writeout happening, and we don't want to prevent access to the directory
4019 * while waiting on the I/O.
4021 long do_unlinkat(int dfd
, struct filename
*name
)
4024 struct dentry
*dentry
;
4028 struct inode
*inode
= NULL
;
4029 struct inode
*delegated_inode
= NULL
;
4030 unsigned int lookup_flags
= 0;
4032 name
= filename_parentat(dfd
, name
, lookup_flags
, &path
, &last
, &type
);
4034 return PTR_ERR(name
);
4037 if (type
!= LAST_NORM
)
4040 error
= mnt_want_write(path
.mnt
);
4044 inode_lock_nested(path
.dentry
->d_inode
, I_MUTEX_PARENT
);
4045 dentry
= __lookup_hash(&last
, path
.dentry
, lookup_flags
);
4046 error
= PTR_ERR(dentry
);
4047 if (!IS_ERR(dentry
)) {
4048 /* Why not before? Because we want correct error value */
4049 if (last
.name
[last
.len
])
4051 inode
= dentry
->d_inode
;
4052 if (d_is_negative(dentry
))
4055 error
= security_path_unlink(&path
, dentry
);
4058 error
= vfs_unlink(path
.dentry
->d_inode
, dentry
, &delegated_inode
);
4062 inode_unlock(path
.dentry
->d_inode
);
4064 iput(inode
); /* truncate the inode here */
4066 if (delegated_inode
) {
4067 error
= break_deleg_wait(&delegated_inode
);
4071 mnt_drop_write(path
.mnt
);
4074 if (retry_estale(error
, lookup_flags
)) {
4075 lookup_flags
|= LOOKUP_REVAL
;
4083 if (d_is_negative(dentry
))
4085 else if (d_is_dir(dentry
))
4092 SYSCALL_DEFINE3(unlinkat
, int, dfd
, const char __user
*, pathname
, int, flag
)
4094 if ((flag
& ~AT_REMOVEDIR
) != 0)
4097 if (flag
& AT_REMOVEDIR
)
4098 return do_rmdir(dfd
, pathname
);
4100 return do_unlinkat(dfd
, getname(pathname
));
4103 SYSCALL_DEFINE1(unlink
, const char __user
*, pathname
)
4105 return do_unlinkat(AT_FDCWD
, getname(pathname
));
4108 int vfs_symlink(struct inode
*dir
, struct dentry
*dentry
, const char *oldname
)
4110 int error
= may_create(dir
, dentry
);
4115 if (!dir
->i_op
->symlink
)
4118 error
= security_inode_symlink(dir
, dentry
, oldname
);
4122 error
= dir
->i_op
->symlink(dir
, dentry
, oldname
);
4124 fsnotify_create(dir
, dentry
);
4127 EXPORT_SYMBOL(vfs_symlink
);
4129 long do_symlinkat(const char __user
*oldname
, int newdfd
,
4130 const char __user
*newname
)
4133 struct filename
*from
;
4134 struct dentry
*dentry
;
4136 unsigned int lookup_flags
= 0;
4138 from
= getname(oldname
);
4140 return PTR_ERR(from
);
4142 dentry
= user_path_create(newdfd
, newname
, &path
, lookup_flags
);
4143 error
= PTR_ERR(dentry
);
4147 error
= security_path_symlink(&path
, dentry
, from
->name
);
4149 error
= vfs_symlink(path
.dentry
->d_inode
, dentry
, from
->name
);
4150 done_path_create(&path
, dentry
);
4151 if (retry_estale(error
, lookup_flags
)) {
4152 lookup_flags
|= LOOKUP_REVAL
;
4160 SYSCALL_DEFINE3(symlinkat
, const char __user
*, oldname
,
4161 int, newdfd
, const char __user
*, newname
)
4163 return do_symlinkat(oldname
, newdfd
, newname
);
4166 SYSCALL_DEFINE2(symlink
, const char __user
*, oldname
, const char __user
*, newname
)
4168 return do_symlinkat(oldname
, AT_FDCWD
, newname
);
4172 * vfs_link - create a new link
4173 * @old_dentry: object to be linked
4175 * @new_dentry: where to create the new link
4176 * @delegated_inode: returns inode needing a delegation break
4178 * The caller must hold dir->i_mutex
4180 * If vfs_link discovers a delegation on the to-be-linked file in need
4181 * of breaking, it will return -EWOULDBLOCK and return a reference to the
4182 * inode in delegated_inode. The caller should then break the delegation
4183 * and retry. Because breaking a delegation may take a long time, the
4184 * caller should drop the i_mutex before doing so.
4186 * Alternatively, a caller may pass NULL for delegated_inode. This may
4187 * be appropriate for callers that expect the underlying filesystem not
4188 * to be NFS exported.
4190 int vfs_link(struct dentry
*old_dentry
, struct inode
*dir
, struct dentry
*new_dentry
, struct inode
**delegated_inode
)
4192 struct inode
*inode
= old_dentry
->d_inode
;
4193 unsigned max_links
= dir
->i_sb
->s_max_links
;
4199 error
= may_create(dir
, new_dentry
);
4203 if (dir
->i_sb
!= inode
->i_sb
)
4207 * A link to an append-only or immutable file cannot be created.
4209 if (IS_APPEND(inode
) || IS_IMMUTABLE(inode
))
4212 * Updating the link count will likely cause i_uid and i_gid to
4213 * be writen back improperly if their true value is unknown to
4216 if (HAS_UNMAPPED_ID(inode
))
4218 if (!dir
->i_op
->link
)
4220 if (S_ISDIR(inode
->i_mode
))
4223 error
= security_inode_link(old_dentry
, dir
, new_dentry
);
4228 /* Make sure we don't allow creating hardlink to an unlinked file */
4229 if (inode
->i_nlink
== 0 && !(inode
->i_state
& I_LINKABLE
))
4231 else if (max_links
&& inode
->i_nlink
>= max_links
)
4234 error
= try_break_deleg(inode
, delegated_inode
);
4236 error
= dir
->i_op
->link(old_dentry
, dir
, new_dentry
);
4239 if (!error
&& (inode
->i_state
& I_LINKABLE
)) {
4240 spin_lock(&inode
->i_lock
);
4241 inode
->i_state
&= ~I_LINKABLE
;
4242 spin_unlock(&inode
->i_lock
);
4244 inode_unlock(inode
);
4246 fsnotify_link(dir
, inode
, new_dentry
);
4249 EXPORT_SYMBOL(vfs_link
);
4252 * Hardlinks are often used in delicate situations. We avoid
4253 * security-related surprises by not following symlinks on the
4256 * We don't follow them on the oldname either to be compatible
4257 * with linux 2.0, and to avoid hard-linking to directories
4258 * and other special files. --ADM
4260 int do_linkat(int olddfd
, const char __user
*oldname
, int newdfd
,
4261 const char __user
*newname
, int flags
)
4263 struct dentry
*new_dentry
;
4264 struct path old_path
, new_path
;
4265 struct inode
*delegated_inode
= NULL
;
4269 if ((flags
& ~(AT_SYMLINK_FOLLOW
| AT_EMPTY_PATH
)) != 0)
4272 * To use null names we require CAP_DAC_READ_SEARCH
4273 * This ensures that not everyone will be able to create
4274 * handlink using the passed filedescriptor.
4276 if (flags
& AT_EMPTY_PATH
) {
4277 if (!capable(CAP_DAC_READ_SEARCH
))
4282 if (flags
& AT_SYMLINK_FOLLOW
)
4283 how
|= LOOKUP_FOLLOW
;
4285 error
= user_path_at(olddfd
, oldname
, how
, &old_path
);
4289 new_dentry
= user_path_create(newdfd
, newname
, &new_path
,
4290 (how
& LOOKUP_REVAL
));
4291 error
= PTR_ERR(new_dentry
);
4292 if (IS_ERR(new_dentry
))
4296 if (old_path
.mnt
!= new_path
.mnt
)
4298 error
= may_linkat(&old_path
);
4299 if (unlikely(error
))
4301 error
= security_path_link(old_path
.dentry
, &new_path
, new_dentry
);
4304 error
= vfs_link(old_path
.dentry
, new_path
.dentry
->d_inode
, new_dentry
, &delegated_inode
);
4306 done_path_create(&new_path
, new_dentry
);
4307 if (delegated_inode
) {
4308 error
= break_deleg_wait(&delegated_inode
);
4310 path_put(&old_path
);
4314 if (retry_estale(error
, how
)) {
4315 path_put(&old_path
);
4316 how
|= LOOKUP_REVAL
;
4320 path_put(&old_path
);
4325 SYSCALL_DEFINE5(linkat
, int, olddfd
, const char __user
*, oldname
,
4326 int, newdfd
, const char __user
*, newname
, int, flags
)
4328 return do_linkat(olddfd
, oldname
, newdfd
, newname
, flags
);
4331 SYSCALL_DEFINE2(link
, const char __user
*, oldname
, const char __user
*, newname
)
4333 return do_linkat(AT_FDCWD
, oldname
, AT_FDCWD
, newname
, 0);
4337 * vfs_rename - rename a filesystem object
4338 * @old_dir: parent of source
4339 * @old_dentry: source
4340 * @new_dir: parent of destination
4341 * @new_dentry: destination
4342 * @delegated_inode: returns an inode needing a delegation break
4343 * @flags: rename flags
4345 * The caller must hold multiple mutexes--see lock_rename()).
4347 * If vfs_rename discovers a delegation in need of breaking at either
4348 * the source or destination, it will return -EWOULDBLOCK and return a
4349 * reference to the inode in delegated_inode. The caller should then
4350 * break the delegation and retry. Because breaking a delegation may
4351 * take a long time, the caller should drop all locks before doing
4354 * Alternatively, a caller may pass NULL for delegated_inode. This may
4355 * be appropriate for callers that expect the underlying filesystem not
4356 * to be NFS exported.
4358 * The worst of all namespace operations - renaming directory. "Perverted"
4359 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
4362 * a) we can get into loop creation.
4363 * b) race potential - two innocent renames can create a loop together.
4364 * That's where 4.4 screws up. Current fix: serialization on
4365 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
4367 * c) we have to lock _four_ objects - parents and victim (if it exists),
4368 * and source (if it is not a directory).
4369 * And that - after we got ->i_mutex on parents (until then we don't know
4370 * whether the target exists). Solution: try to be smart with locking
4371 * order for inodes. We rely on the fact that tree topology may change
4372 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
4373 * move will be locked. Thus we can rank directories by the tree
4374 * (ancestors first) and rank all non-directories after them.
4375 * That works since everybody except rename does "lock parent, lookup,
4376 * lock child" and rename is under ->s_vfs_rename_mutex.
4377 * HOWEVER, it relies on the assumption that any object with ->lookup()
4378 * has no more than 1 dentry. If "hybrid" objects will ever appear,
4379 * we'd better make sure that there's no link(2) for them.
4380 * d) conversion from fhandle to dentry may come in the wrong moment - when
4381 * we are removing the target. Solution: we will have to grab ->i_mutex
4382 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
4383 * ->i_mutex on parents, which works but leads to some truly excessive
4386 int vfs_rename(struct inode
*old_dir
, struct dentry
*old_dentry
,
4387 struct inode
*new_dir
, struct dentry
*new_dentry
,
4388 struct inode
**delegated_inode
, unsigned int flags
)
4391 bool is_dir
= d_is_dir(old_dentry
);
4392 struct inode
*source
= old_dentry
->d_inode
;
4393 struct inode
*target
= new_dentry
->d_inode
;
4394 bool new_is_dir
= false;
4395 unsigned max_links
= new_dir
->i_sb
->s_max_links
;
4396 struct name_snapshot old_name
;
4398 if (source
== target
)
4401 error
= may_delete(old_dir
, old_dentry
, is_dir
);
4406 error
= may_create(new_dir
, new_dentry
);
4408 new_is_dir
= d_is_dir(new_dentry
);
4410 if (!(flags
& RENAME_EXCHANGE
))
4411 error
= may_delete(new_dir
, new_dentry
, is_dir
);
4413 error
= may_delete(new_dir
, new_dentry
, new_is_dir
);
4418 if (!old_dir
->i_op
->rename
)
4422 * If we are going to change the parent - check write permissions,
4423 * we'll need to flip '..'.
4425 if (new_dir
!= old_dir
) {
4427 error
= inode_permission(source
, MAY_WRITE
);
4431 if ((flags
& RENAME_EXCHANGE
) && new_is_dir
) {
4432 error
= inode_permission(target
, MAY_WRITE
);
4438 error
= security_inode_rename(old_dir
, old_dentry
, new_dir
, new_dentry
,
4443 take_dentry_name_snapshot(&old_name
, old_dentry
);
4445 if (!is_dir
|| (flags
& RENAME_EXCHANGE
))
4446 lock_two_nondirectories(source
, target
);
4451 if (is_local_mountpoint(old_dentry
) || is_local_mountpoint(new_dentry
))
4454 if (max_links
&& new_dir
!= old_dir
) {
4456 if (is_dir
&& !new_is_dir
&& new_dir
->i_nlink
>= max_links
)
4458 if ((flags
& RENAME_EXCHANGE
) && !is_dir
&& new_is_dir
&&
4459 old_dir
->i_nlink
>= max_links
)
4463 error
= try_break_deleg(source
, delegated_inode
);
4467 if (target
&& !new_is_dir
) {
4468 error
= try_break_deleg(target
, delegated_inode
);
4472 error
= old_dir
->i_op
->rename(old_dir
, old_dentry
,
4473 new_dir
, new_dentry
, flags
);
4477 if (!(flags
& RENAME_EXCHANGE
) && target
) {
4479 shrink_dcache_parent(new_dentry
);
4480 target
->i_flags
|= S_DEAD
;
4482 dont_mount(new_dentry
);
4483 detach_mounts(new_dentry
);
4485 if (!(old_dir
->i_sb
->s_type
->fs_flags
& FS_RENAME_DOES_D_MOVE
)) {
4486 if (!(flags
& RENAME_EXCHANGE
))
4487 d_move(old_dentry
, new_dentry
);
4489 d_exchange(old_dentry
, new_dentry
);
4492 if (!is_dir
|| (flags
& RENAME_EXCHANGE
))
4493 unlock_two_nondirectories(source
, target
);
4495 inode_unlock(target
);
4498 fsnotify_move(old_dir
, new_dir
, &old_name
.name
, is_dir
,
4499 !(flags
& RENAME_EXCHANGE
) ? target
: NULL
, old_dentry
);
4500 if (flags
& RENAME_EXCHANGE
) {
4501 fsnotify_move(new_dir
, old_dir
, &old_dentry
->d_name
,
4502 new_is_dir
, NULL
, new_dentry
);
4505 release_dentry_name_snapshot(&old_name
);
4509 EXPORT_SYMBOL(vfs_rename
);
4511 static int do_renameat2(int olddfd
, const char __user
*oldname
, int newdfd
,
4512 const char __user
*newname
, unsigned int flags
)
4514 struct dentry
*old_dentry
, *new_dentry
;
4515 struct dentry
*trap
;
4516 struct path old_path
, new_path
;
4517 struct qstr old_last
, new_last
;
4518 int old_type
, new_type
;
4519 struct inode
*delegated_inode
= NULL
;
4520 struct filename
*from
;
4521 struct filename
*to
;
4522 unsigned int lookup_flags
= 0, target_flags
= LOOKUP_RENAME_TARGET
;
4523 bool should_retry
= false;
4526 if (flags
& ~(RENAME_NOREPLACE
| RENAME_EXCHANGE
| RENAME_WHITEOUT
))
4529 if ((flags
& (RENAME_NOREPLACE
| RENAME_WHITEOUT
)) &&
4530 (flags
& RENAME_EXCHANGE
))
4533 if ((flags
& RENAME_WHITEOUT
) && !capable(CAP_MKNOD
))
4536 if (flags
& RENAME_EXCHANGE
)
4540 from
= filename_parentat(olddfd
, getname(oldname
), lookup_flags
,
4541 &old_path
, &old_last
, &old_type
);
4543 error
= PTR_ERR(from
);
4547 to
= filename_parentat(newdfd
, getname(newname
), lookup_flags
,
4548 &new_path
, &new_last
, &new_type
);
4550 error
= PTR_ERR(to
);
4555 if (old_path
.mnt
!= new_path
.mnt
)
4559 if (old_type
!= LAST_NORM
)
4562 if (flags
& RENAME_NOREPLACE
)
4564 if (new_type
!= LAST_NORM
)
4567 error
= mnt_want_write(old_path
.mnt
);
4572 trap
= lock_rename(new_path
.dentry
, old_path
.dentry
);
4574 old_dentry
= __lookup_hash(&old_last
, old_path
.dentry
, lookup_flags
);
4575 error
= PTR_ERR(old_dentry
);
4576 if (IS_ERR(old_dentry
))
4578 /* source must exist */
4580 if (d_is_negative(old_dentry
))
4582 new_dentry
= __lookup_hash(&new_last
, new_path
.dentry
, lookup_flags
| target_flags
);
4583 error
= PTR_ERR(new_dentry
);
4584 if (IS_ERR(new_dentry
))
4587 if ((flags
& RENAME_NOREPLACE
) && d_is_positive(new_dentry
))
4589 if (flags
& RENAME_EXCHANGE
) {
4591 if (d_is_negative(new_dentry
))
4594 if (!d_is_dir(new_dentry
)) {
4596 if (new_last
.name
[new_last
.len
])
4600 /* unless the source is a directory trailing slashes give -ENOTDIR */
4601 if (!d_is_dir(old_dentry
)) {
4603 if (old_last
.name
[old_last
.len
])
4605 if (!(flags
& RENAME_EXCHANGE
) && new_last
.name
[new_last
.len
])
4608 /* source should not be ancestor of target */
4610 if (old_dentry
== trap
)
4612 /* target should not be an ancestor of source */
4613 if (!(flags
& RENAME_EXCHANGE
))
4615 if (new_dentry
== trap
)
4618 error
= security_path_rename(&old_path
, old_dentry
,
4619 &new_path
, new_dentry
, flags
);
4622 error
= vfs_rename(old_path
.dentry
->d_inode
, old_dentry
,
4623 new_path
.dentry
->d_inode
, new_dentry
,
4624 &delegated_inode
, flags
);
4630 unlock_rename(new_path
.dentry
, old_path
.dentry
);
4631 if (delegated_inode
) {
4632 error
= break_deleg_wait(&delegated_inode
);
4636 mnt_drop_write(old_path
.mnt
);
4638 if (retry_estale(error
, lookup_flags
))
4639 should_retry
= true;
4640 path_put(&new_path
);
4643 path_put(&old_path
);
4646 should_retry
= false;
4647 lookup_flags
|= LOOKUP_REVAL
;
4654 SYSCALL_DEFINE5(renameat2
, int, olddfd
, const char __user
*, oldname
,
4655 int, newdfd
, const char __user
*, newname
, unsigned int, flags
)
4657 return do_renameat2(olddfd
, oldname
, newdfd
, newname
, flags
);
4660 SYSCALL_DEFINE4(renameat
, int, olddfd
, const char __user
*, oldname
,
4661 int, newdfd
, const char __user
*, newname
)
4663 return do_renameat2(olddfd
, oldname
, newdfd
, newname
, 0);
4666 SYSCALL_DEFINE2(rename
, const char __user
*, oldname
, const char __user
*, newname
)
4668 return do_renameat2(AT_FDCWD
, oldname
, AT_FDCWD
, newname
, 0);
4671 int vfs_whiteout(struct inode
*dir
, struct dentry
*dentry
)
4673 int error
= may_create(dir
, dentry
);
4677 if (!dir
->i_op
->mknod
)
4680 return dir
->i_op
->mknod(dir
, dentry
,
4681 S_IFCHR
| WHITEOUT_MODE
, WHITEOUT_DEV
);
4683 EXPORT_SYMBOL(vfs_whiteout
);
4685 int readlink_copy(char __user
*buffer
, int buflen
, const char *link
)
4687 int len
= PTR_ERR(link
);
4692 if (len
> (unsigned) buflen
)
4694 if (copy_to_user(buffer
, link
, len
))
4701 * vfs_readlink - copy symlink body into userspace buffer
4702 * @dentry: dentry on which to get symbolic link
4703 * @buffer: user memory pointer
4704 * @buflen: size of buffer
4706 * Does not touch atime. That's up to the caller if necessary
4708 * Does not call security hook.
4710 int vfs_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
)
4712 struct inode
*inode
= d_inode(dentry
);
4713 DEFINE_DELAYED_CALL(done
);
4717 if (unlikely(!(inode
->i_opflags
& IOP_DEFAULT_READLINK
))) {
4718 if (unlikely(inode
->i_op
->readlink
))
4719 return inode
->i_op
->readlink(dentry
, buffer
, buflen
);
4721 if (!d_is_symlink(dentry
))
4724 spin_lock(&inode
->i_lock
);
4725 inode
->i_opflags
|= IOP_DEFAULT_READLINK
;
4726 spin_unlock(&inode
->i_lock
);
4729 link
= READ_ONCE(inode
->i_link
);
4731 link
= inode
->i_op
->get_link(dentry
, inode
, &done
);
4733 return PTR_ERR(link
);
4735 res
= readlink_copy(buffer
, buflen
, link
);
4736 do_delayed_call(&done
);
4739 EXPORT_SYMBOL(vfs_readlink
);
4742 * vfs_get_link - get symlink body
4743 * @dentry: dentry on which to get symbolic link
4744 * @done: caller needs to free returned data with this
4746 * Calls security hook and i_op->get_link() on the supplied inode.
4748 * It does not touch atime. That's up to the caller if necessary.
4750 * Does not work on "special" symlinks like /proc/$$/fd/N
4752 const char *vfs_get_link(struct dentry
*dentry
, struct delayed_call
*done
)
4754 const char *res
= ERR_PTR(-EINVAL
);
4755 struct inode
*inode
= d_inode(dentry
);
4757 if (d_is_symlink(dentry
)) {
4758 res
= ERR_PTR(security_inode_readlink(dentry
));
4760 res
= inode
->i_op
->get_link(dentry
, inode
, done
);
4764 EXPORT_SYMBOL(vfs_get_link
);
4766 /* get the link contents into pagecache */
4767 const char *page_get_link(struct dentry
*dentry
, struct inode
*inode
,
4768 struct delayed_call
*callback
)
4772 struct address_space
*mapping
= inode
->i_mapping
;
4775 page
= find_get_page(mapping
, 0);
4777 return ERR_PTR(-ECHILD
);
4778 if (!PageUptodate(page
)) {
4780 return ERR_PTR(-ECHILD
);
4783 page
= read_mapping_page(mapping
, 0, NULL
);
4787 set_delayed_call(callback
, page_put_link
, page
);
4788 BUG_ON(mapping_gfp_mask(mapping
) & __GFP_HIGHMEM
);
4789 kaddr
= page_address(page
);
4790 nd_terminate_link(kaddr
, inode
->i_size
, PAGE_SIZE
- 1);
4794 EXPORT_SYMBOL(page_get_link
);
4796 void page_put_link(void *arg
)
4800 EXPORT_SYMBOL(page_put_link
);
4802 int page_readlink(struct dentry
*dentry
, char __user
*buffer
, int buflen
)
4804 DEFINE_DELAYED_CALL(done
);
4805 int res
= readlink_copy(buffer
, buflen
,
4806 page_get_link(dentry
, d_inode(dentry
),
4808 do_delayed_call(&done
);
4811 EXPORT_SYMBOL(page_readlink
);
4814 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
4816 int __page_symlink(struct inode
*inode
, const char *symname
, int len
, int nofs
)
4818 struct address_space
*mapping
= inode
->i_mapping
;
4822 unsigned int flags
= 0;
4824 flags
|= AOP_FLAG_NOFS
;
4827 err
= pagecache_write_begin(NULL
, mapping
, 0, len
-1,
4828 flags
, &page
, &fsdata
);
4832 memcpy(page_address(page
), symname
, len
-1);
4834 err
= pagecache_write_end(NULL
, mapping
, 0, len
-1, len
-1,
4841 mark_inode_dirty(inode
);
4846 EXPORT_SYMBOL(__page_symlink
);
4848 int page_symlink(struct inode
*inode
, const char *symname
, int len
)
4850 return __page_symlink(inode
, symname
, len
,
4851 !mapping_gfp_constraint(inode
->i_mapping
, __GFP_FS
));
4853 EXPORT_SYMBOL(page_symlink
);
4855 const struct inode_operations page_symlink_inode_operations
= {
4856 .get_link
= page_get_link
,
4858 EXPORT_SYMBOL(page_symlink_inode_operations
);