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_uflags(const char __user *filename, int uflags)
209 int flags = (uflags & AT_EMPTY_PATH) ? LOOKUP_EMPTY : 0;
211 return getname_flags(filename, flags, NULL);
215 getname(const char __user * filename)
217 return getname_flags(filename, 0, NULL);
221 getname_kernel(const char * filename)
223 struct filename *result;
224 int len = strlen(filename) + 1;
226 result = __getname();
227 if (unlikely(!result))
228 return ERR_PTR(-ENOMEM);
230 if (len <= EMBEDDED_NAME_MAX) {
231 result->name = (char *)result->iname;
232 } else if (len <= PATH_MAX) {
233 const size_t size = offsetof(struct filename, iname[1]);
234 struct filename *tmp;
236 tmp = kmalloc(size, GFP_KERNEL);
237 if (unlikely(!tmp)) {
239 return ERR_PTR(-ENOMEM);
241 tmp->name = (char *)result;
245 return ERR_PTR(-ENAMETOOLONG);
247 memcpy((char *)result->name, filename, len);
249 result->aname = NULL;
251 audit_getname(result);
256 void putname(struct filename *name)
258 if (IS_ERR_OR_NULL(name))
261 BUG_ON(name->refcnt <= 0);
263 if (--name->refcnt > 0)
266 if (name->name != name->iname) {
267 __putname(name->name);
274 * check_acl - perform ACL permission checking
275 * @mnt_userns: user namespace of the mount the inode was found from
276 * @inode: inode to check permissions on
277 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC ...)
279 * This function performs the ACL permission checking. Since this function
280 * retrieve POSIX acls it needs to know whether it is called from a blocking or
281 * non-blocking context and thus cares about the MAY_NOT_BLOCK bit.
283 * If the inode has been found through an idmapped mount the user namespace of
284 * the vfsmount must be passed through @mnt_userns. This function will then take
285 * care to map the inode according to @mnt_userns before checking permissions.
286 * On non-idmapped mounts or if permission checking is to be performed on the
287 * raw inode simply passs init_user_ns.
289 static int check_acl(struct user_namespace *mnt_userns,
290 struct inode *inode, int mask)
292 #ifdef CONFIG_FS_POSIX_ACL
293 struct posix_acl *acl;
295 if (mask & MAY_NOT_BLOCK) {
296 acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS);
299 /* no ->get_acl() calls in RCU mode... */
300 if (is_uncached_acl(acl))
302 return posix_acl_permission(mnt_userns, inode, acl, mask);
305 acl = get_acl(inode, ACL_TYPE_ACCESS);
309 int error = posix_acl_permission(mnt_userns, inode, acl, mask);
310 posix_acl_release(acl);
319 * acl_permission_check - perform basic UNIX permission checking
320 * @mnt_userns: user namespace of the mount the inode was found from
321 * @inode: inode to check permissions on
322 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC ...)
324 * This function performs the basic UNIX permission checking. Since this
325 * function may retrieve POSIX acls it needs to know whether it is called from a
326 * blocking or non-blocking context and thus cares about the MAY_NOT_BLOCK bit.
328 * If the inode has been found through an idmapped mount the user namespace of
329 * the vfsmount must be passed through @mnt_userns. This function will then take
330 * care to map the inode according to @mnt_userns before checking permissions.
331 * On non-idmapped mounts or if permission checking is to be performed on the
332 * raw inode simply passs init_user_ns.
334 static int acl_permission_check(struct user_namespace *mnt_userns,
335 struct inode *inode, int mask)
337 unsigned int mode = inode->i_mode;
340 /* Are we the owner? If so, ACL's don't matter */
341 i_uid = i_uid_into_mnt(mnt_userns, inode);
342 if (likely(uid_eq(current_fsuid(), i_uid))) {
345 return (mask & ~mode) ? -EACCES : 0;
348 /* Do we have ACL's? */
349 if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
350 int error = check_acl(mnt_userns, inode, mask);
351 if (error != -EAGAIN)
355 /* Only RWX matters for group/other mode bits */
359 * Are the group permissions different from
360 * the other permissions in the bits we care
361 * about? Need to check group ownership if so.
363 if (mask & (mode ^ (mode >> 3))) {
364 kgid_t kgid = i_gid_into_mnt(mnt_userns, inode);
365 if (in_group_p(kgid))
369 /* Bits in 'mode' clear that we require? */
370 return (mask & ~mode) ? -EACCES : 0;
374 * generic_permission - check for access rights on a Posix-like filesystem
375 * @mnt_userns: user namespace of the mount the inode was found from
376 * @inode: inode to check access rights for
377 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC,
378 * %MAY_NOT_BLOCK ...)
380 * Used to check for read/write/execute permissions on a file.
381 * We use "fsuid" for this, letting us set arbitrary permissions
382 * for filesystem access without changing the "normal" uids which
383 * are used for other things.
385 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
386 * request cannot be satisfied (eg. requires blocking or too much complexity).
387 * It would then be called again in ref-walk mode.
389 * If the inode has been found through an idmapped mount the user namespace of
390 * the vfsmount must be passed through @mnt_userns. This function will then take
391 * care to map the inode according to @mnt_userns before checking permissions.
392 * On non-idmapped mounts or if permission checking is to be performed on the
393 * raw inode simply passs init_user_ns.
395 int generic_permission(struct user_namespace *mnt_userns, struct inode *inode,
401 * Do the basic permission checks.
403 ret = acl_permission_check(mnt_userns, inode, mask);
407 if (S_ISDIR(inode->i_mode)) {
408 /* DACs are overridable for directories */
409 if (!(mask & MAY_WRITE))
410 if (capable_wrt_inode_uidgid(mnt_userns, inode,
411 CAP_DAC_READ_SEARCH))
413 if (capable_wrt_inode_uidgid(mnt_userns, inode,
420 * Searching includes executable on directories, else just read.
422 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
423 if (mask == MAY_READ)
424 if (capable_wrt_inode_uidgid(mnt_userns, inode,
425 CAP_DAC_READ_SEARCH))
428 * Read/write DACs are always overridable.
429 * Executable DACs are overridable when there is
430 * at least one exec bit set.
432 if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
433 if (capable_wrt_inode_uidgid(mnt_userns, inode,
439 EXPORT_SYMBOL(generic_permission);
442 * do_inode_permission - UNIX permission checking
443 * @mnt_userns: user namespace of the mount the inode was found from
444 * @inode: inode to check permissions on
445 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC ...)
447 * We _really_ want to just do "generic_permission()" without
448 * even looking at the inode->i_op values. So we keep a cache
449 * flag in inode->i_opflags, that says "this has not special
450 * permission function, use the fast case".
452 static inline int do_inode_permission(struct user_namespace *mnt_userns,
453 struct inode *inode, int mask)
455 if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) {
456 if (likely(inode->i_op->permission))
457 return inode->i_op->permission(mnt_userns, inode, mask);
459 /* This gets set once for the inode lifetime */
460 spin_lock(&inode->i_lock);
461 inode->i_opflags |= IOP_FASTPERM;
462 spin_unlock(&inode->i_lock);
464 return generic_permission(mnt_userns, inode, mask);
468 * sb_permission - Check superblock-level permissions
469 * @sb: Superblock of inode to check permission on
470 * @inode: Inode to check permission on
471 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
473 * Separate out file-system wide checks from inode-specific permission checks.
475 static int sb_permission(struct super_block *sb, struct inode *inode, int mask)
477 if (unlikely(mask & MAY_WRITE)) {
478 umode_t mode = inode->i_mode;
480 /* Nobody gets write access to a read-only fs. */
481 if (sb_rdonly(sb) && (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
488 * inode_permission - Check for access rights to a given inode
489 * @mnt_userns: User namespace of the mount the inode was found from
490 * @inode: Inode to check permission on
491 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
493 * Check for read/write/execute permissions on an inode. We use fs[ug]id for
494 * this, letting us set arbitrary permissions for filesystem access without
495 * changing the "normal" UIDs which are used for other things.
497 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
499 int inode_permission(struct user_namespace *mnt_userns,
500 struct inode *inode, int mask)
504 retval = sb_permission(inode->i_sb, inode, mask);
508 if (unlikely(mask & MAY_WRITE)) {
510 * Nobody gets write access to an immutable file.
512 if (IS_IMMUTABLE(inode))
516 * Updating mtime will likely cause i_uid and i_gid to be
517 * written back improperly if their true value is unknown
520 if (HAS_UNMAPPED_ID(mnt_userns, inode))
524 retval = do_inode_permission(mnt_userns, inode, mask);
528 retval = devcgroup_inode_permission(inode, mask);
532 return security_inode_permission(inode, mask);
534 EXPORT_SYMBOL(inode_permission);
537 * path_get - get a reference to a path
538 * @path: path to get the reference to
540 * Given a path increment the reference count to the dentry and the vfsmount.
542 void path_get(const struct path *path)
547 EXPORT_SYMBOL(path_get);
550 * path_put - put a reference to a path
551 * @path: path to put the reference to
553 * Given a path decrement the reference count to the dentry and the vfsmount.
555 void path_put(const struct path *path)
560 EXPORT_SYMBOL(path_put);
562 #define EMBEDDED_LEVELS 2
567 struct inode *inode; /* path.dentry.d_inode */
568 unsigned int flags, state;
569 unsigned seq, m_seq, r_seq;
572 int total_link_count;
575 struct delayed_call done;
578 } *stack, internal[EMBEDDED_LEVELS];
579 struct filename *name;
580 struct nameidata *saved;
585 } __randomize_layout;
587 #define ND_ROOT_PRESET 1
588 #define ND_ROOT_GRABBED 2
591 static void __set_nameidata(struct nameidata *p, int dfd, struct filename *name)
593 struct nameidata *old = current->nameidata;
594 p->stack = p->internal;
599 p->path.dentry = NULL;
600 p->total_link_count = old ? old->total_link_count : 0;
602 current->nameidata = p;
605 static inline void set_nameidata(struct nameidata *p, int dfd, struct filename *name,
606 const struct path *root)
608 __set_nameidata(p, dfd, name);
610 if (unlikely(root)) {
611 p->state = ND_ROOT_PRESET;
616 static void restore_nameidata(void)
618 struct nameidata *now = current->nameidata, *old = now->saved;
620 current->nameidata = old;
622 old->total_link_count = now->total_link_count;
623 if (now->stack != now->internal)
627 static bool nd_alloc_stack(struct nameidata *nd)
631 p= kmalloc_array(MAXSYMLINKS, sizeof(struct saved),
632 nd->flags & LOOKUP_RCU ? GFP_ATOMIC : GFP_KERNEL);
635 memcpy(p, nd->internal, sizeof(nd->internal));
641 * path_connected - Verify that a dentry is below mnt.mnt_root
643 * Rename can sometimes move a file or directory outside of a bind
644 * mount, path_connected allows those cases to be detected.
646 static bool path_connected(struct vfsmount *mnt, struct dentry *dentry)
648 struct super_block *sb = mnt->mnt_sb;
650 /* Bind mounts can have disconnected paths */
651 if (mnt->mnt_root == sb->s_root)
654 return is_subdir(dentry, mnt->mnt_root);
657 static void drop_links(struct nameidata *nd)
661 struct saved *last = nd->stack + i;
662 do_delayed_call(&last->done);
663 clear_delayed_call(&last->done);
667 static void terminate_walk(struct nameidata *nd)
670 if (!(nd->flags & LOOKUP_RCU)) {
673 for (i = 0; i < nd->depth; i++)
674 path_put(&nd->stack[i].link);
675 if (nd->state & ND_ROOT_GRABBED) {
677 nd->state &= ~ND_ROOT_GRABBED;
680 nd->flags &= ~LOOKUP_RCU;
685 nd->path.dentry = NULL;
688 /* path_put is needed afterwards regardless of success or failure */
689 static bool __legitimize_path(struct path *path, unsigned seq, unsigned mseq)
691 int res = __legitimize_mnt(path->mnt, mseq);
698 if (unlikely(!lockref_get_not_dead(&path->dentry->d_lockref))) {
702 return !read_seqcount_retry(&path->dentry->d_seq, seq);
705 static inline bool legitimize_path(struct nameidata *nd,
706 struct path *path, unsigned seq)
708 return __legitimize_path(path, seq, nd->m_seq);
711 static bool legitimize_links(struct nameidata *nd)
714 if (unlikely(nd->flags & LOOKUP_CACHED)) {
719 for (i = 0; i < nd->depth; i++) {
720 struct saved *last = nd->stack + i;
721 if (unlikely(!legitimize_path(nd, &last->link, last->seq))) {
730 static bool legitimize_root(struct nameidata *nd)
733 * For scoped-lookups (where nd->root has been zeroed), we need to
734 * restart the whole lookup from scratch -- because set_root() is wrong
735 * for these lookups (nd->dfd is the root, not the filesystem root).
737 if (!nd->root.mnt && (nd->flags & LOOKUP_IS_SCOPED))
739 /* Nothing to do if nd->root is zero or is managed by the VFS user. */
740 if (!nd->root.mnt || (nd->state & ND_ROOT_PRESET))
742 nd->state |= ND_ROOT_GRABBED;
743 return legitimize_path(nd, &nd->root, nd->root_seq);
747 * Path walking has 2 modes, rcu-walk and ref-walk (see
748 * Documentation/filesystems/path-lookup.txt). In situations when we can't
749 * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
750 * normal reference counts on dentries and vfsmounts to transition to ref-walk
751 * mode. Refcounts are grabbed at the last known good point before rcu-walk
752 * got stuck, so ref-walk may continue from there. If this is not successful
753 * (eg. a seqcount has changed), then failure is returned and it's up to caller
754 * to restart the path walk from the beginning in ref-walk mode.
758 * try_to_unlazy - try to switch to ref-walk mode.
759 * @nd: nameidata pathwalk data
760 * Returns: true on success, false on failure
762 * try_to_unlazy attempts to legitimize the current nd->path and nd->root
764 * Must be called from rcu-walk context.
765 * Nothing should touch nameidata between try_to_unlazy() failure and
768 static bool try_to_unlazy(struct nameidata *nd)
770 struct dentry *parent = nd->path.dentry;
772 BUG_ON(!(nd->flags & LOOKUP_RCU));
774 nd->flags &= ~LOOKUP_RCU;
775 if (unlikely(!legitimize_links(nd)))
777 if (unlikely(!legitimize_path(nd, &nd->path, nd->seq)))
779 if (unlikely(!legitimize_root(nd)))
782 BUG_ON(nd->inode != parent->d_inode);
787 nd->path.dentry = NULL;
794 * try_to_unlazy_next - try to switch to ref-walk mode.
795 * @nd: nameidata pathwalk data
796 * @dentry: next dentry to step into
797 * @seq: seq number to check @dentry against
798 * Returns: true on success, false on failure
800 * Similar to to try_to_unlazy(), but here we have the next dentry already
801 * picked by rcu-walk and want to legitimize that in addition to the current
802 * nd->path and nd->root for ref-walk mode. Must be called from rcu-walk context.
803 * Nothing should touch nameidata between try_to_unlazy_next() failure and
806 static bool try_to_unlazy_next(struct nameidata *nd, struct dentry *dentry, unsigned seq)
808 BUG_ON(!(nd->flags & LOOKUP_RCU));
810 nd->flags &= ~LOOKUP_RCU;
811 if (unlikely(!legitimize_links(nd)))
813 if (unlikely(!legitimize_mnt(nd->path.mnt, nd->m_seq)))
815 if (unlikely(!lockref_get_not_dead(&nd->path.dentry->d_lockref)))
819 * We need to move both the parent and the dentry from the RCU domain
820 * to be properly refcounted. And the sequence number in the dentry
821 * validates *both* dentry counters, since we checked the sequence
822 * number of the parent after we got the child sequence number. So we
823 * know the parent must still be valid if the child sequence number is
825 if (unlikely(!lockref_get_not_dead(&dentry->d_lockref)))
827 if (unlikely(read_seqcount_retry(&dentry->d_seq, seq)))
830 * Sequence counts matched. Now make sure that the root is
831 * still valid and get it if required.
833 if (unlikely(!legitimize_root(nd)))
841 nd->path.dentry = NULL;
851 static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
853 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE))
854 return dentry->d_op->d_revalidate(dentry, flags);
860 * complete_walk - successful completion of path walk
861 * @nd: pointer nameidata
863 * If we had been in RCU mode, drop out of it and legitimize nd->path.
864 * Revalidate the final result, unless we'd already done that during
865 * the path walk or the filesystem doesn't ask for it. Return 0 on
866 * success, -error on failure. In case of failure caller does not
867 * need to drop nd->path.
869 static int complete_walk(struct nameidata *nd)
871 struct dentry *dentry = nd->path.dentry;
874 if (nd->flags & LOOKUP_RCU) {
876 * We don't want to zero nd->root for scoped-lookups or
877 * externally-managed nd->root.
879 if (!(nd->state & ND_ROOT_PRESET))
880 if (!(nd->flags & LOOKUP_IS_SCOPED))
882 nd->flags &= ~LOOKUP_CACHED;
883 if (!try_to_unlazy(nd))
887 if (unlikely(nd->flags & LOOKUP_IS_SCOPED)) {
889 * While the guarantee of LOOKUP_IS_SCOPED is (roughly) "don't
890 * ever step outside the root during lookup" and should already
891 * be guaranteed by the rest of namei, we want to avoid a namei
892 * BUG resulting in userspace being given a path that was not
893 * scoped within the root at some point during the lookup.
895 * So, do a final sanity-check to make sure that in the
896 * worst-case scenario (a complete bypass of LOOKUP_IS_SCOPED)
897 * we won't silently return an fd completely outside of the
898 * requested root to userspace.
900 * Userspace could move the path outside the root after this
901 * check, but as discussed elsewhere this is not a concern (the
902 * resolved file was inside the root at some point).
904 if (!path_is_under(&nd->path, &nd->root))
908 if (likely(!(nd->state & ND_JUMPED)))
911 if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE)))
914 status = dentry->d_op->d_weak_revalidate(dentry, nd->flags);
924 static int set_root(struct nameidata *nd)
926 struct fs_struct *fs = current->fs;
929 * Jumping to the real root in a scoped-lookup is a BUG in namei, but we
930 * still have to ensure it doesn't happen because it will cause a breakout
933 if (WARN_ON(nd->flags & LOOKUP_IS_SCOPED))
934 return -ENOTRECOVERABLE;
936 if (nd->flags & LOOKUP_RCU) {
940 seq = read_seqcount_begin(&fs->seq);
942 nd->root_seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
943 } while (read_seqcount_retry(&fs->seq, seq));
945 get_fs_root(fs, &nd->root);
946 nd->state |= ND_ROOT_GRABBED;
951 static int nd_jump_root(struct nameidata *nd)
953 if (unlikely(nd->flags & LOOKUP_BENEATH))
955 if (unlikely(nd->flags & LOOKUP_NO_XDEV)) {
956 /* Absolute path arguments to path_init() are allowed. */
957 if (nd->path.mnt != NULL && nd->path.mnt != nd->root.mnt)
961 int error = set_root(nd);
965 if (nd->flags & LOOKUP_RCU) {
969 nd->inode = d->d_inode;
970 nd->seq = nd->root_seq;
971 if (unlikely(read_seqcount_retry(&d->d_seq, nd->seq)))
977 nd->inode = nd->path.dentry->d_inode;
979 nd->state |= ND_JUMPED;
984 * Helper to directly jump to a known parsed path from ->get_link,
985 * caller must have taken a reference to path beforehand.
987 int nd_jump_link(struct path *path)
990 struct nameidata *nd = current->nameidata;
992 if (unlikely(nd->flags & LOOKUP_NO_MAGICLINKS))
996 if (unlikely(nd->flags & LOOKUP_NO_XDEV)) {
997 if (nd->path.mnt != path->mnt)
1000 /* Not currently safe for scoped-lookups. */
1001 if (unlikely(nd->flags & LOOKUP_IS_SCOPED))
1004 path_put(&nd->path);
1006 nd->inode = nd->path.dentry->d_inode;
1007 nd->state |= ND_JUMPED;
1015 static inline void put_link(struct nameidata *nd)
1017 struct saved *last = nd->stack + --nd->depth;
1018 do_delayed_call(&last->done);
1019 if (!(nd->flags & LOOKUP_RCU))
1020 path_put(&last->link);
1023 int sysctl_protected_symlinks __read_mostly = 0;
1024 int sysctl_protected_hardlinks __read_mostly = 0;
1025 int sysctl_protected_fifos __read_mostly;
1026 int sysctl_protected_regular __read_mostly;
1029 * may_follow_link - Check symlink following for unsafe situations
1030 * @nd: nameidata pathwalk data
1032 * In the case of the sysctl_protected_symlinks sysctl being enabled,
1033 * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
1034 * in a sticky world-writable directory. This is to protect privileged
1035 * processes from failing races against path names that may change out
1036 * from under them by way of other users creating malicious symlinks.
1037 * It will permit symlinks to be followed only when outside a sticky
1038 * world-writable directory, or when the uid of the symlink and follower
1039 * match, or when the directory owner matches the symlink's owner.
1041 * Returns 0 if following the symlink is allowed, -ve on error.
1043 static inline int may_follow_link(struct nameidata *nd, const struct inode *inode)
1045 struct user_namespace *mnt_userns;
1048 if (!sysctl_protected_symlinks)
1051 mnt_userns = mnt_user_ns(nd->path.mnt);
1052 i_uid = i_uid_into_mnt(mnt_userns, inode);
1053 /* Allowed if owner and follower match. */
1054 if (uid_eq(current_cred()->fsuid, i_uid))
1057 /* Allowed if parent directory not sticky and world-writable. */
1058 if ((nd->dir_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH))
1061 /* Allowed if parent directory and link owner match. */
1062 if (uid_valid(nd->dir_uid) && uid_eq(nd->dir_uid, i_uid))
1065 if (nd->flags & LOOKUP_RCU)
1068 audit_inode(nd->name, nd->stack[0].link.dentry, 0);
1069 audit_log_path_denied(AUDIT_ANOM_LINK, "follow_link");
1074 * safe_hardlink_source - Check for safe hardlink conditions
1075 * @mnt_userns: user namespace of the mount the inode was found from
1076 * @inode: the source inode to hardlink from
1078 * Return false if at least one of the following conditions:
1079 * - inode is not a regular file
1081 * - inode is setgid and group-exec
1082 * - access failure for read and write
1084 * Otherwise returns true.
1086 static bool safe_hardlink_source(struct user_namespace *mnt_userns,
1087 struct inode *inode)
1089 umode_t mode = inode->i_mode;
1091 /* Special files should not get pinned to the filesystem. */
1095 /* Setuid files should not get pinned to the filesystem. */
1099 /* Executable setgid files should not get pinned to the filesystem. */
1100 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP))
1103 /* Hardlinking to unreadable or unwritable sources is dangerous. */
1104 if (inode_permission(mnt_userns, inode, MAY_READ | MAY_WRITE))
1111 * may_linkat - Check permissions for creating a hardlink
1112 * @mnt_userns: user namespace of the mount the inode was found from
1113 * @link: the source to hardlink from
1115 * Block hardlink when all of:
1116 * - sysctl_protected_hardlinks enabled
1117 * - fsuid does not match inode
1118 * - hardlink source is unsafe (see safe_hardlink_source() above)
1119 * - not CAP_FOWNER in a namespace with the inode owner uid mapped
1121 * If the inode has been found through an idmapped mount the user namespace of
1122 * the vfsmount must be passed through @mnt_userns. This function will then take
1123 * care to map the inode according to @mnt_userns before checking permissions.
1124 * On non-idmapped mounts or if permission checking is to be performed on the
1125 * raw inode simply passs init_user_ns.
1127 * Returns 0 if successful, -ve on error.
1129 int may_linkat(struct user_namespace *mnt_userns, struct path *link)
1131 struct inode *inode = link->dentry->d_inode;
1133 /* Inode writeback is not safe when the uid or gid are invalid. */
1134 if (!uid_valid(i_uid_into_mnt(mnt_userns, inode)) ||
1135 !gid_valid(i_gid_into_mnt(mnt_userns, inode)))
1138 if (!sysctl_protected_hardlinks)
1141 /* Source inode owner (or CAP_FOWNER) can hardlink all they like,
1142 * otherwise, it must be a safe source.
1144 if (safe_hardlink_source(mnt_userns, inode) ||
1145 inode_owner_or_capable(mnt_userns, inode))
1148 audit_log_path_denied(AUDIT_ANOM_LINK, "linkat");
1153 * may_create_in_sticky - Check whether an O_CREAT open in a sticky directory
1154 * should be allowed, or not, on files that already
1156 * @mnt_userns: user namespace of the mount the inode was found from
1157 * @nd: nameidata pathwalk data
1158 * @inode: the inode of the file to open
1160 * Block an O_CREAT open of a FIFO (or a regular file) when:
1161 * - sysctl_protected_fifos (or sysctl_protected_regular) is enabled
1162 * - the file already exists
1163 * - we are in a sticky directory
1164 * - we don't own the file
1165 * - the owner of the directory doesn't own the file
1166 * - the directory is world writable
1167 * If the sysctl_protected_fifos (or sysctl_protected_regular) is set to 2
1168 * the directory doesn't have to be world writable: being group writable will
1171 * If the inode has been found through an idmapped mount the user namespace of
1172 * the vfsmount must be passed through @mnt_userns. This function will then take
1173 * care to map the inode according to @mnt_userns before checking permissions.
1174 * On non-idmapped mounts or if permission checking is to be performed on the
1175 * raw inode simply passs init_user_ns.
1177 * Returns 0 if the open is allowed, -ve on error.
1179 static int may_create_in_sticky(struct user_namespace *mnt_userns,
1180 struct nameidata *nd, struct inode *const inode)
1182 umode_t dir_mode = nd->dir_mode;
1183 kuid_t dir_uid = nd->dir_uid;
1185 if ((!sysctl_protected_fifos && S_ISFIFO(inode->i_mode)) ||
1186 (!sysctl_protected_regular && S_ISREG(inode->i_mode)) ||
1187 likely(!(dir_mode & S_ISVTX)) ||
1188 uid_eq(i_uid_into_mnt(mnt_userns, inode), dir_uid) ||
1189 uid_eq(current_fsuid(), i_uid_into_mnt(mnt_userns, inode)))
1192 if (likely(dir_mode & 0002) ||
1194 ((sysctl_protected_fifos >= 2 && S_ISFIFO(inode->i_mode)) ||
1195 (sysctl_protected_regular >= 2 && S_ISREG(inode->i_mode))))) {
1196 const char *operation = S_ISFIFO(inode->i_mode) ?
1197 "sticky_create_fifo" :
1198 "sticky_create_regular";
1199 audit_log_path_denied(AUDIT_ANOM_CREAT, operation);
1206 * follow_up - Find the mountpoint of path's vfsmount
1208 * Given a path, find the mountpoint of its source file system.
1209 * Replace @path with the path of the mountpoint in the parent mount.
1212 * Return 1 if we went up a level and 0 if we were already at the
1215 int follow_up(struct path *path)
1217 struct mount *mnt = real_mount(path->mnt);
1218 struct mount *parent;
1219 struct dentry *mountpoint;
1221 read_seqlock_excl(&mount_lock);
1222 parent = mnt->mnt_parent;
1223 if (parent == mnt) {
1224 read_sequnlock_excl(&mount_lock);
1227 mntget(&parent->mnt);
1228 mountpoint = dget(mnt->mnt_mountpoint);
1229 read_sequnlock_excl(&mount_lock);
1231 path->dentry = mountpoint;
1233 path->mnt = &parent->mnt;
1236 EXPORT_SYMBOL(follow_up);
1238 static bool choose_mountpoint_rcu(struct mount *m, const struct path *root,
1239 struct path *path, unsigned *seqp)
1241 while (mnt_has_parent(m)) {
1242 struct dentry *mountpoint = m->mnt_mountpoint;
1245 if (unlikely(root->dentry == mountpoint &&
1246 root->mnt == &m->mnt))
1248 if (mountpoint != m->mnt.mnt_root) {
1249 path->mnt = &m->mnt;
1250 path->dentry = mountpoint;
1251 *seqp = read_seqcount_begin(&mountpoint->d_seq);
1258 static bool choose_mountpoint(struct mount *m, const struct path *root,
1265 unsigned seq, mseq = read_seqbegin(&mount_lock);
1267 found = choose_mountpoint_rcu(m, root, path, &seq);
1268 if (unlikely(!found)) {
1269 if (!read_seqretry(&mount_lock, mseq))
1272 if (likely(__legitimize_path(path, seq, mseq)))
1284 * Perform an automount
1285 * - return -EISDIR to tell follow_managed() to stop and return the path we
1288 static int follow_automount(struct path *path, int *count, unsigned lookup_flags)
1290 struct dentry *dentry = path->dentry;
1292 /* We don't want to mount if someone's just doing a stat -
1293 * unless they're stat'ing a directory and appended a '/' to
1296 * We do, however, want to mount if someone wants to open or
1297 * create a file of any type under the mountpoint, wants to
1298 * traverse through the mountpoint or wants to open the
1299 * mounted directory. Also, autofs may mark negative dentries
1300 * as being automount points. These will need the attentions
1301 * of the daemon to instantiate them before they can be used.
1303 if (!(lookup_flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
1304 LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
1308 if (count && (*count)++ >= MAXSYMLINKS)
1311 return finish_automount(dentry->d_op->d_automount(path), path);
1315 * mount traversal - out-of-line part. One note on ->d_flags accesses -
1316 * dentries are pinned but not locked here, so negative dentry can go
1317 * positive right under us. Use of smp_load_acquire() provides a barrier
1318 * sufficient for ->d_inode and ->d_flags consistency.
1320 static int __traverse_mounts(struct path *path, unsigned flags, bool *jumped,
1321 int *count, unsigned lookup_flags)
1323 struct vfsmount *mnt = path->mnt;
1324 bool need_mntput = false;
1327 while (flags & DCACHE_MANAGED_DENTRY) {
1328 /* Allow the filesystem to manage the transit without i_mutex
1330 if (flags & DCACHE_MANAGE_TRANSIT) {
1331 ret = path->dentry->d_op->d_manage(path, false);
1332 flags = smp_load_acquire(&path->dentry->d_flags);
1337 if (flags & DCACHE_MOUNTED) { // something's mounted on it..
1338 struct vfsmount *mounted = lookup_mnt(path);
1339 if (mounted) { // ... in our namespace
1343 path->mnt = mounted;
1344 path->dentry = dget(mounted->mnt_root);
1345 // here we know it's positive
1346 flags = path->dentry->d_flags;
1352 if (!(flags & DCACHE_NEED_AUTOMOUNT))
1355 // uncovered automount point
1356 ret = follow_automount(path, count, lookup_flags);
1357 flags = smp_load_acquire(&path->dentry->d_flags);
1364 // possible if you race with several mount --move
1365 if (need_mntput && path->mnt == mnt)
1367 if (!ret && unlikely(d_flags_negative(flags)))
1369 *jumped = need_mntput;
1373 static inline int traverse_mounts(struct path *path, bool *jumped,
1374 int *count, unsigned lookup_flags)
1376 unsigned flags = smp_load_acquire(&path->dentry->d_flags);
1379 if (likely(!(flags & DCACHE_MANAGED_DENTRY))) {
1381 if (unlikely(d_flags_negative(flags)))
1385 return __traverse_mounts(path, flags, jumped, count, lookup_flags);
1388 int follow_down_one(struct path *path)
1390 struct vfsmount *mounted;
1392 mounted = lookup_mnt(path);
1396 path->mnt = mounted;
1397 path->dentry = dget(mounted->mnt_root);
1402 EXPORT_SYMBOL(follow_down_one);
1405 * Follow down to the covering mount currently visible to userspace. At each
1406 * point, the filesystem owning that dentry may be queried as to whether the
1407 * caller is permitted to proceed or not.
1409 int follow_down(struct path *path)
1411 struct vfsmount *mnt = path->mnt;
1413 int ret = traverse_mounts(path, &jumped, NULL, 0);
1415 if (path->mnt != mnt)
1419 EXPORT_SYMBOL(follow_down);
1422 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
1423 * we meet a managed dentry that would need blocking.
1425 static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
1426 struct inode **inode, unsigned *seqp)
1428 struct dentry *dentry = path->dentry;
1429 unsigned int flags = dentry->d_flags;
1431 if (likely(!(flags & DCACHE_MANAGED_DENTRY)))
1434 if (unlikely(nd->flags & LOOKUP_NO_XDEV))
1439 * Don't forget we might have a non-mountpoint managed dentry
1440 * that wants to block transit.
1442 if (unlikely(flags & DCACHE_MANAGE_TRANSIT)) {
1443 int res = dentry->d_op->d_manage(path, true);
1445 return res == -EISDIR;
1446 flags = dentry->d_flags;
1449 if (flags & DCACHE_MOUNTED) {
1450 struct mount *mounted = __lookup_mnt(path->mnt, dentry);
1452 path->mnt = &mounted->mnt;
1453 dentry = path->dentry = mounted->mnt.mnt_root;
1454 nd->state |= ND_JUMPED;
1455 *seqp = read_seqcount_begin(&dentry->d_seq);
1456 *inode = dentry->d_inode;
1458 * We don't need to re-check ->d_seq after this
1459 * ->d_inode read - there will be an RCU delay
1460 * between mount hash removal and ->mnt_root
1461 * becoming unpinned.
1463 flags = dentry->d_flags;
1466 if (read_seqretry(&mount_lock, nd->m_seq))
1469 return !(flags & DCACHE_NEED_AUTOMOUNT);
1473 static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry,
1474 struct path *path, struct inode **inode,
1480 path->mnt = nd->path.mnt;
1481 path->dentry = dentry;
1482 if (nd->flags & LOOKUP_RCU) {
1483 unsigned int seq = *seqp;
1484 if (unlikely(!*inode))
1486 if (likely(__follow_mount_rcu(nd, path, inode, seqp)))
1488 if (!try_to_unlazy_next(nd, dentry, seq))
1490 // *path might've been clobbered by __follow_mount_rcu()
1491 path->mnt = nd->path.mnt;
1492 path->dentry = dentry;
1494 ret = traverse_mounts(path, &jumped, &nd->total_link_count, nd->flags);
1496 if (unlikely(nd->flags & LOOKUP_NO_XDEV))
1499 nd->state |= ND_JUMPED;
1501 if (unlikely(ret)) {
1503 if (path->mnt != nd->path.mnt)
1506 *inode = d_backing_inode(path->dentry);
1507 *seqp = 0; /* out of RCU mode, so the value doesn't matter */
1513 * This looks up the name in dcache and possibly revalidates the found dentry.
1514 * NULL is returned if the dentry does not exist in the cache.
1516 static struct dentry *lookup_dcache(const struct qstr *name,
1520 struct dentry *dentry = d_lookup(dir, name);
1522 int error = d_revalidate(dentry, flags);
1523 if (unlikely(error <= 0)) {
1525 d_invalidate(dentry);
1527 return ERR_PTR(error);
1534 * Parent directory has inode locked exclusive. This is one
1535 * and only case when ->lookup() gets called on non in-lookup
1536 * dentries - as the matter of fact, this only gets called
1537 * when directory is guaranteed to have no in-lookup children
1540 static struct dentry *__lookup_hash(const struct qstr *name,
1541 struct dentry *base, unsigned int flags)
1543 struct dentry *dentry = lookup_dcache(name, base, flags);
1545 struct inode *dir = base->d_inode;
1550 /* Don't create child dentry for a dead directory. */
1551 if (unlikely(IS_DEADDIR(dir)))
1552 return ERR_PTR(-ENOENT);
1554 dentry = d_alloc(base, name);
1555 if (unlikely(!dentry))
1556 return ERR_PTR(-ENOMEM);
1558 old = dir->i_op->lookup(dir, dentry, flags);
1559 if (unlikely(old)) {
1566 static struct dentry *lookup_fast(struct nameidata *nd,
1567 struct inode **inode,
1570 struct dentry *dentry, *parent = nd->path.dentry;
1574 * Rename seqlock is not required here because in the off chance
1575 * of a false negative due to a concurrent rename, the caller is
1576 * going to fall back to non-racy lookup.
1578 if (nd->flags & LOOKUP_RCU) {
1580 dentry = __d_lookup_rcu(parent, &nd->last, &seq);
1581 if (unlikely(!dentry)) {
1582 if (!try_to_unlazy(nd))
1583 return ERR_PTR(-ECHILD);
1588 * This sequence count validates that the inode matches
1589 * the dentry name information from lookup.
1591 *inode = d_backing_inode(dentry);
1592 if (unlikely(read_seqcount_retry(&dentry->d_seq, seq)))
1593 return ERR_PTR(-ECHILD);
1596 * This sequence count validates that the parent had no
1597 * changes while we did the lookup of the dentry above.
1599 * The memory barrier in read_seqcount_begin of child is
1600 * enough, we can use __read_seqcount_retry here.
1602 if (unlikely(__read_seqcount_retry(&parent->d_seq, nd->seq)))
1603 return ERR_PTR(-ECHILD);
1606 status = d_revalidate(dentry, nd->flags);
1607 if (likely(status > 0))
1609 if (!try_to_unlazy_next(nd, dentry, seq))
1610 return ERR_PTR(-ECHILD);
1611 if (status == -ECHILD)
1612 /* we'd been told to redo it in non-rcu mode */
1613 status = d_revalidate(dentry, nd->flags);
1615 dentry = __d_lookup(parent, &nd->last);
1616 if (unlikely(!dentry))
1618 status = d_revalidate(dentry, nd->flags);
1620 if (unlikely(status <= 0)) {
1622 d_invalidate(dentry);
1624 return ERR_PTR(status);
1629 /* Fast lookup failed, do it the slow way */
1630 static struct dentry *__lookup_slow(const struct qstr *name,
1634 struct dentry *dentry, *old;
1635 struct inode *inode = dir->d_inode;
1636 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
1638 /* Don't go there if it's already dead */
1639 if (unlikely(IS_DEADDIR(inode)))
1640 return ERR_PTR(-ENOENT);
1642 dentry = d_alloc_parallel(dir, name, &wq);
1645 if (unlikely(!d_in_lookup(dentry))) {
1646 int error = d_revalidate(dentry, flags);
1647 if (unlikely(error <= 0)) {
1649 d_invalidate(dentry);
1654 dentry = ERR_PTR(error);
1657 old = inode->i_op->lookup(inode, dentry, flags);
1658 d_lookup_done(dentry);
1659 if (unlikely(old)) {
1667 static struct dentry *lookup_slow(const struct qstr *name,
1671 struct inode *inode = dir->d_inode;
1673 inode_lock_shared(inode);
1674 res = __lookup_slow(name, dir, flags);
1675 inode_unlock_shared(inode);
1679 static inline int may_lookup(struct user_namespace *mnt_userns,
1680 struct nameidata *nd)
1682 if (nd->flags & LOOKUP_RCU) {
1683 int err = inode_permission(mnt_userns, nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
1684 if (err != -ECHILD || !try_to_unlazy(nd))
1687 return inode_permission(mnt_userns, nd->inode, MAY_EXEC);
1690 static int reserve_stack(struct nameidata *nd, struct path *link, unsigned seq)
1692 if (unlikely(nd->total_link_count++ >= MAXSYMLINKS))
1695 if (likely(nd->depth != EMBEDDED_LEVELS))
1697 if (likely(nd->stack != nd->internal))
1699 if (likely(nd_alloc_stack(nd)))
1702 if (nd->flags & LOOKUP_RCU) {
1703 // we need to grab link before we do unlazy. And we can't skip
1704 // unlazy even if we fail to grab the link - cleanup needs it
1705 bool grabbed_link = legitimize_path(nd, link, seq);
1707 if (!try_to_unlazy(nd) != 0 || !grabbed_link)
1710 if (nd_alloc_stack(nd))
1716 enum {WALK_TRAILING = 1, WALK_MORE = 2, WALK_NOFOLLOW = 4};
1718 static const char *pick_link(struct nameidata *nd, struct path *link,
1719 struct inode *inode, unsigned seq, int flags)
1723 int error = reserve_stack(nd, link, seq);
1725 if (unlikely(error)) {
1726 if (!(nd->flags & LOOKUP_RCU))
1728 return ERR_PTR(error);
1730 last = nd->stack + nd->depth++;
1732 clear_delayed_call(&last->done);
1735 if (flags & WALK_TRAILING) {
1736 error = may_follow_link(nd, inode);
1737 if (unlikely(error))
1738 return ERR_PTR(error);
1741 if (unlikely(nd->flags & LOOKUP_NO_SYMLINKS) ||
1742 unlikely(link->mnt->mnt_flags & MNT_NOSYMFOLLOW))
1743 return ERR_PTR(-ELOOP);
1745 if (!(nd->flags & LOOKUP_RCU)) {
1746 touch_atime(&last->link);
1748 } else if (atime_needs_update(&last->link, inode)) {
1749 if (!try_to_unlazy(nd))
1750 return ERR_PTR(-ECHILD);
1751 touch_atime(&last->link);
1754 error = security_inode_follow_link(link->dentry, inode,
1755 nd->flags & LOOKUP_RCU);
1756 if (unlikely(error))
1757 return ERR_PTR(error);
1759 res = READ_ONCE(inode->i_link);
1761 const char * (*get)(struct dentry *, struct inode *,
1762 struct delayed_call *);
1763 get = inode->i_op->get_link;
1764 if (nd->flags & LOOKUP_RCU) {
1765 res = get(NULL, inode, &last->done);
1766 if (res == ERR_PTR(-ECHILD) && try_to_unlazy(nd))
1767 res = get(link->dentry, inode, &last->done);
1769 res = get(link->dentry, inode, &last->done);
1777 error = nd_jump_root(nd);
1778 if (unlikely(error))
1779 return ERR_PTR(error);
1780 while (unlikely(*++res == '/'))
1785 all_done: // pure jump
1791 * Do we need to follow links? We _really_ want to be able
1792 * to do this check without having to look at inode->i_op,
1793 * so we keep a cache of "no, this doesn't need follow_link"
1794 * for the common case.
1796 static const char *step_into(struct nameidata *nd, int flags,
1797 struct dentry *dentry, struct inode *inode, unsigned seq)
1800 int err = handle_mounts(nd, dentry, &path, &inode, &seq);
1803 return ERR_PTR(err);
1804 if (likely(!d_is_symlink(path.dentry)) ||
1805 ((flags & WALK_TRAILING) && !(nd->flags & LOOKUP_FOLLOW)) ||
1806 (flags & WALK_NOFOLLOW)) {
1807 /* not a symlink or should not follow */
1808 if (!(nd->flags & LOOKUP_RCU)) {
1809 dput(nd->path.dentry);
1810 if (nd->path.mnt != path.mnt)
1811 mntput(nd->path.mnt);
1818 if (nd->flags & LOOKUP_RCU) {
1819 /* make sure that d_is_symlink above matches inode */
1820 if (read_seqcount_retry(&path.dentry->d_seq, seq))
1821 return ERR_PTR(-ECHILD);
1823 if (path.mnt == nd->path.mnt)
1826 return pick_link(nd, &path, inode, seq, flags);
1829 static struct dentry *follow_dotdot_rcu(struct nameidata *nd,
1830 struct inode **inodep,
1833 struct dentry *parent, *old;
1835 if (path_equal(&nd->path, &nd->root))
1837 if (unlikely(nd->path.dentry == nd->path.mnt->mnt_root)) {
1840 if (!choose_mountpoint_rcu(real_mount(nd->path.mnt),
1841 &nd->root, &path, &seq))
1843 if (unlikely(nd->flags & LOOKUP_NO_XDEV))
1844 return ERR_PTR(-ECHILD);
1846 nd->inode = path.dentry->d_inode;
1848 if (unlikely(read_seqretry(&mount_lock, nd->m_seq)))
1849 return ERR_PTR(-ECHILD);
1850 /* we know that mountpoint was pinned */
1852 old = nd->path.dentry;
1853 parent = old->d_parent;
1854 *inodep = parent->d_inode;
1855 *seqp = read_seqcount_begin(&parent->d_seq);
1856 if (unlikely(read_seqcount_retry(&old->d_seq, nd->seq)))
1857 return ERR_PTR(-ECHILD);
1858 if (unlikely(!path_connected(nd->path.mnt, parent)))
1859 return ERR_PTR(-ECHILD);
1862 if (unlikely(read_seqretry(&mount_lock, nd->m_seq)))
1863 return ERR_PTR(-ECHILD);
1864 if (unlikely(nd->flags & LOOKUP_BENEATH))
1865 return ERR_PTR(-ECHILD);
1869 static struct dentry *follow_dotdot(struct nameidata *nd,
1870 struct inode **inodep,
1873 struct dentry *parent;
1875 if (path_equal(&nd->path, &nd->root))
1877 if (unlikely(nd->path.dentry == nd->path.mnt->mnt_root)) {
1880 if (!choose_mountpoint(real_mount(nd->path.mnt),
1883 path_put(&nd->path);
1885 nd->inode = path.dentry->d_inode;
1886 if (unlikely(nd->flags & LOOKUP_NO_XDEV))
1887 return ERR_PTR(-EXDEV);
1889 /* rare case of legitimate dget_parent()... */
1890 parent = dget_parent(nd->path.dentry);
1891 if (unlikely(!path_connected(nd->path.mnt, parent))) {
1893 return ERR_PTR(-ENOENT);
1896 *inodep = parent->d_inode;
1900 if (unlikely(nd->flags & LOOKUP_BENEATH))
1901 return ERR_PTR(-EXDEV);
1902 dget(nd->path.dentry);
1906 static const char *handle_dots(struct nameidata *nd, int type)
1908 if (type == LAST_DOTDOT) {
1909 const char *error = NULL;
1910 struct dentry *parent;
1911 struct inode *inode;
1914 if (!nd->root.mnt) {
1915 error = ERR_PTR(set_root(nd));
1919 if (nd->flags & LOOKUP_RCU)
1920 parent = follow_dotdot_rcu(nd, &inode, &seq);
1922 parent = follow_dotdot(nd, &inode, &seq);
1924 return ERR_CAST(parent);
1925 if (unlikely(!parent))
1926 error = step_into(nd, WALK_NOFOLLOW,
1927 nd->path.dentry, nd->inode, nd->seq);
1929 error = step_into(nd, WALK_NOFOLLOW,
1930 parent, inode, seq);
1931 if (unlikely(error))
1934 if (unlikely(nd->flags & LOOKUP_IS_SCOPED)) {
1936 * If there was a racing rename or mount along our
1937 * path, then we can't be sure that ".." hasn't jumped
1938 * above nd->root (and so userspace should retry or use
1942 if (unlikely(__read_seqcount_retry(&mount_lock.seqcount, nd->m_seq)))
1943 return ERR_PTR(-EAGAIN);
1944 if (unlikely(__read_seqcount_retry(&rename_lock.seqcount, nd->r_seq)))
1945 return ERR_PTR(-EAGAIN);
1951 static const char *walk_component(struct nameidata *nd, int flags)
1953 struct dentry *dentry;
1954 struct inode *inode;
1957 * "." and ".." are special - ".." especially so because it has
1958 * to be able to know about the current root directory and
1959 * parent relationships.
1961 if (unlikely(nd->last_type != LAST_NORM)) {
1962 if (!(flags & WALK_MORE) && nd->depth)
1964 return handle_dots(nd, nd->last_type);
1966 dentry = lookup_fast(nd, &inode, &seq);
1968 return ERR_CAST(dentry);
1969 if (unlikely(!dentry)) {
1970 dentry = lookup_slow(&nd->last, nd->path.dentry, nd->flags);
1972 return ERR_CAST(dentry);
1974 if (!(flags & WALK_MORE) && nd->depth)
1976 return step_into(nd, flags, dentry, inode, seq);
1980 * We can do the critical dentry name comparison and hashing
1981 * operations one word at a time, but we are limited to:
1983 * - Architectures with fast unaligned word accesses. We could
1984 * do a "get_unaligned()" if this helps and is sufficiently
1987 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
1988 * do not trap on the (extremely unlikely) case of a page
1989 * crossing operation.
1991 * - Furthermore, we need an efficient 64-bit compile for the
1992 * 64-bit case in order to generate the "number of bytes in
1993 * the final mask". Again, that could be replaced with a
1994 * efficient population count instruction or similar.
1996 #ifdef CONFIG_DCACHE_WORD_ACCESS
1998 #include <asm/word-at-a-time.h>
2002 /* Architecture provides HASH_MIX and fold_hash() in <asm/hash.h> */
2004 #elif defined(CONFIG_64BIT)
2006 * Register pressure in the mixing function is an issue, particularly
2007 * on 32-bit x86, but almost any function requires one state value and
2008 * one temporary. Instead, use a function designed for two state values
2009 * and no temporaries.
2011 * This function cannot create a collision in only two iterations, so
2012 * we have two iterations to achieve avalanche. In those two iterations,
2013 * we have six layers of mixing, which is enough to spread one bit's
2014 * influence out to 2^6 = 64 state bits.
2016 * Rotate constants are scored by considering either 64 one-bit input
2017 * deltas or 64*63/2 = 2016 two-bit input deltas, and finding the
2018 * probability of that delta causing a change to each of the 128 output
2019 * bits, using a sample of random initial states.
2021 * The Shannon entropy of the computed probabilities is then summed
2022 * to produce a score. Ideally, any input change has a 50% chance of
2023 * toggling any given output bit.
2025 * Mixing scores (in bits) for (12,45):
2026 * Input delta: 1-bit 2-bit
2027 * 1 round: 713.3 42542.6
2028 * 2 rounds: 2753.7 140389.8
2029 * 3 rounds: 5954.1 233458.2
2030 * 4 rounds: 7862.6 256672.2
2031 * Perfect: 8192 258048
2032 * (64*128) (64*63/2 * 128)
2034 #define HASH_MIX(x, y, a) \
2036 y ^= x, x = rol64(x,12),\
2037 x += y, y = rol64(y,45),\
2041 * Fold two longs into one 32-bit hash value. This must be fast, but
2042 * latency isn't quite as critical, as there is a fair bit of additional
2043 * work done before the hash value is used.
2045 static inline unsigned int fold_hash(unsigned long x, unsigned long y)
2047 y ^= x * GOLDEN_RATIO_64;
2048 y *= GOLDEN_RATIO_64;
2052 #else /* 32-bit case */
2055 * Mixing scores (in bits) for (7,20):
2056 * Input delta: 1-bit 2-bit
2057 * 1 round: 330.3 9201.6
2058 * 2 rounds: 1246.4 25475.4
2059 * 3 rounds: 1907.1 31295.1
2060 * 4 rounds: 2042.3 31718.6
2061 * Perfect: 2048 31744
2062 * (32*64) (32*31/2 * 64)
2064 #define HASH_MIX(x, y, a) \
2066 y ^= x, x = rol32(x, 7),\
2067 x += y, y = rol32(y,20),\
2070 static inline unsigned int fold_hash(unsigned long x, unsigned long y)
2072 /* Use arch-optimized multiply if one exists */
2073 return __hash_32(y ^ __hash_32(x));
2079 * Return the hash of a string of known length. This is carfully
2080 * designed to match hash_name(), which is the more critical function.
2081 * In particular, we must end by hashing a final word containing 0..7
2082 * payload bytes, to match the way that hash_name() iterates until it
2083 * finds the delimiter after the name.
2085 unsigned int full_name_hash(const void *salt, const char *name, unsigned int len)
2087 unsigned long a, x = 0, y = (unsigned long)salt;
2092 a = load_unaligned_zeropad(name);
2093 if (len < sizeof(unsigned long))
2096 name += sizeof(unsigned long);
2097 len -= sizeof(unsigned long);
2099 x ^= a & bytemask_from_count(len);
2101 return fold_hash(x, y);
2103 EXPORT_SYMBOL(full_name_hash);
2105 /* Return the "hash_len" (hash and length) of a null-terminated string */
2106 u64 hashlen_string(const void *salt, const char *name)
2108 unsigned long a = 0, x = 0, y = (unsigned long)salt;
2109 unsigned long adata, mask, len;
2110 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
2117 len += sizeof(unsigned long);
2119 a = load_unaligned_zeropad(name+len);
2120 } while (!has_zero(a, &adata, &constants));
2122 adata = prep_zero_mask(a, adata, &constants);
2123 mask = create_zero_mask(adata);
2124 x ^= a & zero_bytemask(mask);
2126 return hashlen_create(fold_hash(x, y), len + find_zero(mask));
2128 EXPORT_SYMBOL(hashlen_string);
2131 * Calculate the length and hash of the path component, and
2132 * return the "hash_len" as the result.
2134 static inline u64 hash_name(const void *salt, const char *name)
2136 unsigned long a = 0, b, x = 0, y = (unsigned long)salt;
2137 unsigned long adata, bdata, mask, len;
2138 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
2145 len += sizeof(unsigned long);
2147 a = load_unaligned_zeropad(name+len);
2148 b = a ^ REPEAT_BYTE('/');
2149 } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants)));
2151 adata = prep_zero_mask(a, adata, &constants);
2152 bdata = prep_zero_mask(b, bdata, &constants);
2153 mask = create_zero_mask(adata | bdata);
2154 x ^= a & zero_bytemask(mask);
2156 return hashlen_create(fold_hash(x, y), len + find_zero(mask));
2159 #else /* !CONFIG_DCACHE_WORD_ACCESS: Slow, byte-at-a-time version */
2161 /* Return the hash of a string of known length */
2162 unsigned int full_name_hash(const void *salt, const char *name, unsigned int len)
2164 unsigned long hash = init_name_hash(salt);
2166 hash = partial_name_hash((unsigned char)*name++, hash);
2167 return end_name_hash(hash);
2169 EXPORT_SYMBOL(full_name_hash);
2171 /* Return the "hash_len" (hash and length) of a null-terminated string */
2172 u64 hashlen_string(const void *salt, const char *name)
2174 unsigned long hash = init_name_hash(salt);
2175 unsigned long len = 0, c;
2177 c = (unsigned char)*name;
2180 hash = partial_name_hash(c, hash);
2181 c = (unsigned char)name[len];
2183 return hashlen_create(end_name_hash(hash), len);
2185 EXPORT_SYMBOL(hashlen_string);
2188 * We know there's a real path component here of at least
2191 static inline u64 hash_name(const void *salt, const char *name)
2193 unsigned long hash = init_name_hash(salt);
2194 unsigned long len = 0, c;
2196 c = (unsigned char)*name;
2199 hash = partial_name_hash(c, hash);
2200 c = (unsigned char)name[len];
2201 } while (c && c != '/');
2202 return hashlen_create(end_name_hash(hash), len);
2209 * This is the basic name resolution function, turning a pathname into
2210 * the final dentry. We expect 'base' to be positive and a directory.
2212 * Returns 0 and nd will have valid dentry and mnt on success.
2213 * Returns error and drops reference to input namei data on failure.
2215 static int link_path_walk(const char *name, struct nameidata *nd)
2217 int depth = 0; // depth <= nd->depth
2220 nd->last_type = LAST_ROOT;
2221 nd->flags |= LOOKUP_PARENT;
2223 return PTR_ERR(name);
2227 nd->dir_mode = 0; // short-circuit the 'hardening' idiocy
2231 /* At this point we know we have a real path component. */
2233 struct user_namespace *mnt_userns;
2238 mnt_userns = mnt_user_ns(nd->path.mnt);
2239 err = may_lookup(mnt_userns, nd);
2243 hash_len = hash_name(nd->path.dentry, name);
2246 if (name[0] == '.') switch (hashlen_len(hash_len)) {
2248 if (name[1] == '.') {
2250 nd->state |= ND_JUMPED;
2256 if (likely(type == LAST_NORM)) {
2257 struct dentry *parent = nd->path.dentry;
2258 nd->state &= ~ND_JUMPED;
2259 if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
2260 struct qstr this = { { .hash_len = hash_len }, .name = name };
2261 err = parent->d_op->d_hash(parent, &this);
2264 hash_len = this.hash_len;
2269 nd->last.hash_len = hash_len;
2270 nd->last.name = name;
2271 nd->last_type = type;
2273 name += hashlen_len(hash_len);
2277 * If it wasn't NUL, we know it was '/'. Skip that
2278 * slash, and continue until no more slashes.
2282 } while (unlikely(*name == '/'));
2283 if (unlikely(!*name)) {
2285 /* pathname or trailing symlink, done */
2287 nd->dir_uid = i_uid_into_mnt(mnt_userns, nd->inode);
2288 nd->dir_mode = nd->inode->i_mode;
2289 nd->flags &= ~LOOKUP_PARENT;
2292 /* last component of nested symlink */
2293 name = nd->stack[--depth].name;
2294 link = walk_component(nd, 0);
2296 /* not the last component */
2297 link = walk_component(nd, WALK_MORE);
2299 if (unlikely(link)) {
2301 return PTR_ERR(link);
2302 /* a symlink to follow */
2303 nd->stack[depth++].name = name;
2307 if (unlikely(!d_can_lookup(nd->path.dentry))) {
2308 if (nd->flags & LOOKUP_RCU) {
2309 if (!try_to_unlazy(nd))
2317 /* must be paired with terminate_walk() */
2318 static const char *path_init(struct nameidata *nd, unsigned flags)
2321 const char *s = nd->name->name;
2323 /* LOOKUP_CACHED requires RCU, ask caller to retry */
2324 if ((flags & (LOOKUP_RCU | LOOKUP_CACHED)) == LOOKUP_CACHED)
2325 return ERR_PTR(-EAGAIN);
2328 flags &= ~LOOKUP_RCU;
2329 if (flags & LOOKUP_RCU)
2333 nd->state |= ND_JUMPED;
2335 nd->m_seq = __read_seqcount_begin(&mount_lock.seqcount);
2336 nd->r_seq = __read_seqcount_begin(&rename_lock.seqcount);
2339 if (nd->state & ND_ROOT_PRESET) {
2340 struct dentry *root = nd->root.dentry;
2341 struct inode *inode = root->d_inode;
2342 if (*s && unlikely(!d_can_lookup(root)))
2343 return ERR_PTR(-ENOTDIR);
2344 nd->path = nd->root;
2346 if (flags & LOOKUP_RCU) {
2347 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
2348 nd->root_seq = nd->seq;
2350 path_get(&nd->path);
2355 nd->root.mnt = NULL;
2357 /* Absolute pathname -- fetch the root (LOOKUP_IN_ROOT uses nd->dfd). */
2358 if (*s == '/' && !(flags & LOOKUP_IN_ROOT)) {
2359 error = nd_jump_root(nd);
2360 if (unlikely(error))
2361 return ERR_PTR(error);
2365 /* Relative pathname -- get the starting-point it is relative to. */
2366 if (nd->dfd == AT_FDCWD) {
2367 if (flags & LOOKUP_RCU) {
2368 struct fs_struct *fs = current->fs;
2372 seq = read_seqcount_begin(&fs->seq);
2374 nd->inode = nd->path.dentry->d_inode;
2375 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
2376 } while (read_seqcount_retry(&fs->seq, seq));
2378 get_fs_pwd(current->fs, &nd->path);
2379 nd->inode = nd->path.dentry->d_inode;
2382 /* Caller must check execute permissions on the starting path component */
2383 struct fd f = fdget_raw(nd->dfd);
2384 struct dentry *dentry;
2387 return ERR_PTR(-EBADF);
2389 dentry = f.file->f_path.dentry;
2391 if (*s && unlikely(!d_can_lookup(dentry))) {
2393 return ERR_PTR(-ENOTDIR);
2396 nd->path = f.file->f_path;
2397 if (flags & LOOKUP_RCU) {
2398 nd->inode = nd->path.dentry->d_inode;
2399 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
2401 path_get(&nd->path);
2402 nd->inode = nd->path.dentry->d_inode;
2407 /* For scoped-lookups we need to set the root to the dirfd as well. */
2408 if (flags & LOOKUP_IS_SCOPED) {
2409 nd->root = nd->path;
2410 if (flags & LOOKUP_RCU) {
2411 nd->root_seq = nd->seq;
2413 path_get(&nd->root);
2414 nd->state |= ND_ROOT_GRABBED;
2420 static inline const char *lookup_last(struct nameidata *nd)
2422 if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
2423 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
2425 return walk_component(nd, WALK_TRAILING);
2428 static int handle_lookup_down(struct nameidata *nd)
2430 if (!(nd->flags & LOOKUP_RCU))
2431 dget(nd->path.dentry);
2432 return PTR_ERR(step_into(nd, WALK_NOFOLLOW,
2433 nd->path.dentry, nd->inode, nd->seq));
2436 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
2437 static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path)
2439 const char *s = path_init(nd, flags);
2442 if (unlikely(flags & LOOKUP_DOWN) && !IS_ERR(s)) {
2443 err = handle_lookup_down(nd);
2444 if (unlikely(err < 0))
2448 while (!(err = link_path_walk(s, nd)) &&
2449 (s = lookup_last(nd)) != NULL)
2451 if (!err && unlikely(nd->flags & LOOKUP_MOUNTPOINT)) {
2452 err = handle_lookup_down(nd);
2453 nd->state &= ~ND_JUMPED; // no d_weak_revalidate(), please...
2456 err = complete_walk(nd);
2458 if (!err && nd->flags & LOOKUP_DIRECTORY)
2459 if (!d_can_lookup(nd->path.dentry))
2463 nd->path.mnt = NULL;
2464 nd->path.dentry = NULL;
2470 static int __filename_lookup(int dfd, struct filename *name, unsigned flags,
2471 struct path *path, struct path *root)
2474 struct nameidata nd;
2476 return PTR_ERR(name);
2477 set_nameidata(&nd, dfd, name, root);
2478 retval = path_lookupat(&nd, flags | LOOKUP_RCU, path);
2479 if (unlikely(retval == -ECHILD))
2480 retval = path_lookupat(&nd, flags, path);
2481 if (unlikely(retval == -ESTALE))
2482 retval = path_lookupat(&nd, flags | LOOKUP_REVAL, path);
2484 if (likely(!retval))
2485 audit_inode(name, path->dentry,
2486 flags & LOOKUP_MOUNTPOINT ? AUDIT_INODE_NOEVAL : 0);
2487 restore_nameidata();
2491 int filename_lookup(int dfd, struct filename *name, unsigned flags,
2492 struct path *path, struct path *root)
2494 int retval = __filename_lookup(dfd, name, flags, path, root);
2500 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
2501 static int path_parentat(struct nameidata *nd, unsigned flags,
2502 struct path *parent)
2504 const char *s = path_init(nd, flags);
2505 int err = link_path_walk(s, nd);
2507 err = complete_walk(nd);
2510 nd->path.mnt = NULL;
2511 nd->path.dentry = NULL;
2517 /* Note: this does not consume "name" */
2518 static int filename_parentat(int dfd, struct filename *name,
2519 unsigned int flags, struct path *parent,
2520 struct qstr *last, int *type)
2523 struct nameidata nd;
2526 return PTR_ERR(name);
2527 set_nameidata(&nd, dfd, name, NULL);
2528 retval = path_parentat(&nd, flags | LOOKUP_RCU, parent);
2529 if (unlikely(retval == -ECHILD))
2530 retval = path_parentat(&nd, flags, parent);
2531 if (unlikely(retval == -ESTALE))
2532 retval = path_parentat(&nd, flags | LOOKUP_REVAL, parent);
2533 if (likely(!retval)) {
2535 *type = nd.last_type;
2536 audit_inode(name, parent->dentry, AUDIT_INODE_PARENT);
2538 restore_nameidata();
2542 /* does lookup, returns the object with parent locked */
2543 static struct dentry *__kern_path_locked(struct filename *name, struct path *path)
2549 error = filename_parentat(AT_FDCWD, name, 0, path, &last, &type);
2551 return ERR_PTR(error);
2552 if (unlikely(type != LAST_NORM)) {
2554 return ERR_PTR(-EINVAL);
2556 inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
2557 d = __lookup_hash(&last, path->dentry, 0);
2559 inode_unlock(path->dentry->d_inode);
2565 struct dentry *kern_path_locked(const char *name, struct path *path)
2567 struct filename *filename = getname_kernel(name);
2568 struct dentry *res = __kern_path_locked(filename, path);
2574 int kern_path(const char *name, unsigned int flags, struct path *path)
2576 return filename_lookup(AT_FDCWD, getname_kernel(name),
2579 EXPORT_SYMBOL(kern_path);
2582 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
2583 * @dentry: pointer to dentry of the base directory
2584 * @mnt: pointer to vfs mount of the base directory
2585 * @name: pointer to file name
2586 * @flags: lookup flags
2587 * @path: pointer to struct path to fill
2589 int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
2590 const char *name, unsigned int flags,
2593 struct path root = {.mnt = mnt, .dentry = dentry};
2594 /* the first argument of filename_lookup() is ignored with root */
2595 return filename_lookup(AT_FDCWD, getname_kernel(name),
2596 flags , path, &root);
2598 EXPORT_SYMBOL(vfs_path_lookup);
2600 static int lookup_one_common(struct user_namespace *mnt_userns,
2601 const char *name, struct dentry *base, int len,
2606 this->hash = full_name_hash(base, name, len);
2610 if (unlikely(name[0] == '.')) {
2611 if (len < 2 || (len == 2 && name[1] == '.'))
2616 unsigned int c = *(const unsigned char *)name++;
2617 if (c == '/' || c == '\0')
2621 * See if the low-level filesystem might want
2622 * to use its own hash..
2624 if (base->d_flags & DCACHE_OP_HASH) {
2625 int err = base->d_op->d_hash(base, this);
2630 return inode_permission(mnt_userns, base->d_inode, MAY_EXEC);
2634 * try_lookup_one_len - filesystem helper to lookup single pathname component
2635 * @name: pathname component to lookup
2636 * @base: base directory to lookup from
2637 * @len: maximum length @len should be interpreted to
2639 * Look up a dentry by name in the dcache, returning NULL if it does not
2640 * currently exist. The function does not try to create a dentry.
2642 * Note that this routine is purely a helper for filesystem usage and should
2643 * not be called by generic code.
2645 * The caller must hold base->i_mutex.
2647 struct dentry *try_lookup_one_len(const char *name, struct dentry *base, int len)
2652 WARN_ON_ONCE(!inode_is_locked(base->d_inode));
2654 err = lookup_one_common(&init_user_ns, name, base, len, &this);
2656 return ERR_PTR(err);
2658 return lookup_dcache(&this, base, 0);
2660 EXPORT_SYMBOL(try_lookup_one_len);
2663 * lookup_one_len - filesystem helper to lookup single pathname component
2664 * @name: pathname component to lookup
2665 * @base: base directory to lookup from
2666 * @len: maximum length @len should be interpreted to
2668 * Note that this routine is purely a helper for filesystem usage and should
2669 * not be called by generic code.
2671 * The caller must hold base->i_mutex.
2673 struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
2675 struct dentry *dentry;
2679 WARN_ON_ONCE(!inode_is_locked(base->d_inode));
2681 err = lookup_one_common(&init_user_ns, name, base, len, &this);
2683 return ERR_PTR(err);
2685 dentry = lookup_dcache(&this, base, 0);
2686 return dentry ? dentry : __lookup_slow(&this, base, 0);
2688 EXPORT_SYMBOL(lookup_one_len);
2691 * lookup_one - filesystem helper to lookup single pathname component
2692 * @mnt_userns: user namespace of the mount the lookup is performed from
2693 * @name: pathname component to lookup
2694 * @base: base directory to lookup from
2695 * @len: maximum length @len should be interpreted to
2697 * Note that this routine is purely a helper for filesystem usage and should
2698 * not be called by generic code.
2700 * The caller must hold base->i_mutex.
2702 struct dentry *lookup_one(struct user_namespace *mnt_userns, const char *name,
2703 struct dentry *base, int len)
2705 struct dentry *dentry;
2709 WARN_ON_ONCE(!inode_is_locked(base->d_inode));
2711 err = lookup_one_common(mnt_userns, name, base, len, &this);
2713 return ERR_PTR(err);
2715 dentry = lookup_dcache(&this, base, 0);
2716 return dentry ? dentry : __lookup_slow(&this, base, 0);
2718 EXPORT_SYMBOL(lookup_one);
2721 * lookup_one_len_unlocked - filesystem helper to lookup single pathname component
2722 * @name: pathname component to lookup
2723 * @base: base directory to lookup from
2724 * @len: maximum length @len should be interpreted to
2726 * Note that this routine is purely a helper for filesystem usage and should
2727 * not be called by generic code.
2729 * Unlike lookup_one_len, it should be called without the parent
2730 * i_mutex held, and will take the i_mutex itself if necessary.
2732 struct dentry *lookup_one_len_unlocked(const char *name,
2733 struct dentry *base, int len)
2739 err = lookup_one_common(&init_user_ns, name, base, len, &this);
2741 return ERR_PTR(err);
2743 ret = lookup_dcache(&this, base, 0);
2745 ret = lookup_slow(&this, base, 0);
2748 EXPORT_SYMBOL(lookup_one_len_unlocked);
2751 * Like lookup_one_len_unlocked(), except that it yields ERR_PTR(-ENOENT)
2752 * on negatives. Returns known positive or ERR_PTR(); that's what
2753 * most of the users want. Note that pinned negative with unlocked parent
2754 * _can_ become positive at any time, so callers of lookup_one_len_unlocked()
2755 * need to be very careful; pinned positives have ->d_inode stable, so
2756 * this one avoids such problems.
2758 struct dentry *lookup_positive_unlocked(const char *name,
2759 struct dentry *base, int len)
2761 struct dentry *ret = lookup_one_len_unlocked(name, base, len);
2762 if (!IS_ERR(ret) && d_flags_negative(smp_load_acquire(&ret->d_flags))) {
2764 ret = ERR_PTR(-ENOENT);
2768 EXPORT_SYMBOL(lookup_positive_unlocked);
2770 #ifdef CONFIG_UNIX98_PTYS
2771 int path_pts(struct path *path)
2773 /* Find something mounted on "pts" in the same directory as
2776 struct dentry *parent = dget_parent(path->dentry);
2777 struct dentry *child;
2778 struct qstr this = QSTR_INIT("pts", 3);
2780 if (unlikely(!path_connected(path->mnt, parent))) {
2785 path->dentry = parent;
2786 child = d_hash_and_lookup(parent, &this);
2790 path->dentry = child;
2797 int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
2798 struct path *path, int *empty)
2800 return filename_lookup(dfd, getname_flags(name, flags, empty),
2803 EXPORT_SYMBOL(user_path_at_empty);
2805 int __check_sticky(struct user_namespace *mnt_userns, struct inode *dir,
2806 struct inode *inode)
2808 kuid_t fsuid = current_fsuid();
2810 if (uid_eq(i_uid_into_mnt(mnt_userns, inode), fsuid))
2812 if (uid_eq(i_uid_into_mnt(mnt_userns, dir), fsuid))
2814 return !capable_wrt_inode_uidgid(mnt_userns, inode, CAP_FOWNER);
2816 EXPORT_SYMBOL(__check_sticky);
2819 * Check whether we can remove a link victim from directory dir, check
2820 * whether the type of victim is right.
2821 * 1. We can't do it if dir is read-only (done in permission())
2822 * 2. We should have write and exec permissions on dir
2823 * 3. We can't remove anything from append-only dir
2824 * 4. We can't do anything with immutable dir (done in permission())
2825 * 5. If the sticky bit on dir is set we should either
2826 * a. be owner of dir, or
2827 * b. be owner of victim, or
2828 * c. have CAP_FOWNER capability
2829 * 6. If the victim is append-only or immutable we can't do antyhing with
2830 * links pointing to it.
2831 * 7. If the victim has an unknown uid or gid we can't change the inode.
2832 * 8. If we were asked to remove a directory and victim isn't one - ENOTDIR.
2833 * 9. If we were asked to remove a non-directory and victim isn't one - EISDIR.
2834 * 10. We can't remove a root or mountpoint.
2835 * 11. We don't allow removal of NFS sillyrenamed files; it's handled by
2836 * nfs_async_unlink().
2838 static int may_delete(struct user_namespace *mnt_userns, struct inode *dir,
2839 struct dentry *victim, bool isdir)
2841 struct inode *inode = d_backing_inode(victim);
2844 if (d_is_negative(victim))
2848 BUG_ON(victim->d_parent->d_inode != dir);
2850 /* Inode writeback is not safe when the uid or gid are invalid. */
2851 if (!uid_valid(i_uid_into_mnt(mnt_userns, inode)) ||
2852 !gid_valid(i_gid_into_mnt(mnt_userns, inode)))
2855 audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE);
2857 error = inode_permission(mnt_userns, dir, MAY_WRITE | MAY_EXEC);
2863 if (check_sticky(mnt_userns, dir, inode) || IS_APPEND(inode) ||
2864 IS_IMMUTABLE(inode) || IS_SWAPFILE(inode) ||
2865 HAS_UNMAPPED_ID(mnt_userns, inode))
2868 if (!d_is_dir(victim))
2870 if (IS_ROOT(victim))
2872 } else if (d_is_dir(victim))
2874 if (IS_DEADDIR(dir))
2876 if (victim->d_flags & DCACHE_NFSFS_RENAMED)
2881 /* Check whether we can create an object with dentry child in directory
2883 * 1. We can't do it if child already exists (open has special treatment for
2884 * this case, but since we are inlined it's OK)
2885 * 2. We can't do it if dir is read-only (done in permission())
2886 * 3. We can't do it if the fs can't represent the fsuid or fsgid.
2887 * 4. We should have write and exec permissions on dir
2888 * 5. We can't do it if dir is immutable (done in permission())
2890 static inline int may_create(struct user_namespace *mnt_userns,
2891 struct inode *dir, struct dentry *child)
2893 audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE);
2896 if (IS_DEADDIR(dir))
2898 if (!fsuidgid_has_mapping(dir->i_sb, mnt_userns))
2901 return inode_permission(mnt_userns, dir, MAY_WRITE | MAY_EXEC);
2905 * p1 and p2 should be directories on the same fs.
2907 struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
2912 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
2916 mutex_lock(&p1->d_sb->s_vfs_rename_mutex);
2918 p = d_ancestor(p2, p1);
2920 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT);
2921 inode_lock_nested(p1->d_inode, I_MUTEX_CHILD);
2925 p = d_ancestor(p1, p2);
2927 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
2928 inode_lock_nested(p2->d_inode, I_MUTEX_CHILD);
2932 inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
2933 inode_lock_nested(p2->d_inode, I_MUTEX_PARENT2);
2936 EXPORT_SYMBOL(lock_rename);
2938 void unlock_rename(struct dentry *p1, struct dentry *p2)
2940 inode_unlock(p1->d_inode);
2942 inode_unlock(p2->d_inode);
2943 mutex_unlock(&p1->d_sb->s_vfs_rename_mutex);
2946 EXPORT_SYMBOL(unlock_rename);
2949 * vfs_create - create new file
2950 * @mnt_userns: user namespace of the mount the inode was found from
2951 * @dir: inode of @dentry
2952 * @dentry: pointer to dentry of the base directory
2953 * @mode: mode of the new file
2954 * @want_excl: whether the file must not yet exist
2956 * Create a new file.
2958 * If the inode has been found through an idmapped mount the user namespace of
2959 * the vfsmount must be passed through @mnt_userns. This function will then take
2960 * care to map the inode according to @mnt_userns before checking permissions.
2961 * On non-idmapped mounts or if permission checking is to be performed on the
2962 * raw inode simply passs init_user_ns.
2964 int vfs_create(struct user_namespace *mnt_userns, struct inode *dir,
2965 struct dentry *dentry, umode_t mode, bool want_excl)
2967 int error = may_create(mnt_userns, dir, dentry);
2971 if (!dir->i_op->create)
2972 return -EACCES; /* shouldn't it be ENOSYS? */
2975 error = security_inode_create(dir, dentry, mode);
2978 error = dir->i_op->create(mnt_userns, dir, dentry, mode, want_excl);
2980 fsnotify_create(dir, dentry);
2983 EXPORT_SYMBOL(vfs_create);
2985 int vfs_mkobj(struct dentry *dentry, umode_t mode,
2986 int (*f)(struct dentry *, umode_t, void *),
2989 struct inode *dir = dentry->d_parent->d_inode;
2990 int error = may_create(&init_user_ns, dir, dentry);
2996 error = security_inode_create(dir, dentry, mode);
2999 error = f(dentry, mode, arg);
3001 fsnotify_create(dir, dentry);
3004 EXPORT_SYMBOL(vfs_mkobj);
3006 bool may_open_dev(const struct path *path)
3008 return !(path->mnt->mnt_flags & MNT_NODEV) &&
3009 !(path->mnt->mnt_sb->s_iflags & SB_I_NODEV);
3012 static int may_open(struct user_namespace *mnt_userns, const struct path *path,
3013 int acc_mode, int flag)
3015 struct dentry *dentry = path->dentry;
3016 struct inode *inode = dentry->d_inode;
3022 switch (inode->i_mode & S_IFMT) {
3026 if (acc_mode & MAY_WRITE)
3028 if (acc_mode & MAY_EXEC)
3033 if (!may_open_dev(path))
3038 if (acc_mode & MAY_EXEC)
3043 if ((acc_mode & MAY_EXEC) && path_noexec(path))
3048 error = inode_permission(mnt_userns, inode, MAY_OPEN | acc_mode);
3053 * An append-only file must be opened in append mode for writing.
3055 if (IS_APPEND(inode)) {
3056 if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
3062 /* O_NOATIME can only be set by the owner or superuser */
3063 if (flag & O_NOATIME && !inode_owner_or_capable(mnt_userns, inode))
3069 static int handle_truncate(struct user_namespace *mnt_userns, struct file *filp)
3071 const struct path *path = &filp->f_path;
3072 struct inode *inode = path->dentry->d_inode;
3073 int error = get_write_access(inode);
3077 * Refuse to truncate files with mandatory locks held on them.
3079 error = security_path_truncate(path);
3081 error = do_truncate(mnt_userns, path->dentry, 0,
3082 ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
3085 put_write_access(inode);
3089 static inline int open_to_namei_flags(int flag)
3091 if ((flag & O_ACCMODE) == 3)
3096 static int may_o_create(struct user_namespace *mnt_userns,
3097 const struct path *dir, struct dentry *dentry,
3100 int error = security_path_mknod(dir, dentry, mode, 0);
3104 if (!fsuidgid_has_mapping(dir->dentry->d_sb, mnt_userns))
3107 error = inode_permission(mnt_userns, dir->dentry->d_inode,
3108 MAY_WRITE | MAY_EXEC);
3112 return security_inode_create(dir->dentry->d_inode, dentry, mode);
3116 * Attempt to atomically look up, create and open a file from a negative
3119 * Returns 0 if successful. The file will have been created and attached to
3120 * @file by the filesystem calling finish_open().
3122 * If the file was looked up only or didn't need creating, FMODE_OPENED won't
3123 * be set. The caller will need to perform the open themselves. @path will
3124 * have been updated to point to the new dentry. This may be negative.
3126 * Returns an error code otherwise.
3128 static struct dentry *atomic_open(struct nameidata *nd, struct dentry *dentry,
3130 int open_flag, umode_t mode)
3132 struct dentry *const DENTRY_NOT_SET = (void *) -1UL;
3133 struct inode *dir = nd->path.dentry->d_inode;
3136 if (nd->flags & LOOKUP_DIRECTORY)
3137 open_flag |= O_DIRECTORY;
3139 file->f_path.dentry = DENTRY_NOT_SET;
3140 file->f_path.mnt = nd->path.mnt;
3141 error = dir->i_op->atomic_open(dir, dentry, file,
3142 open_to_namei_flags(open_flag), mode);
3143 d_lookup_done(dentry);
3145 if (file->f_mode & FMODE_OPENED) {
3146 if (unlikely(dentry != file->f_path.dentry)) {
3148 dentry = dget(file->f_path.dentry);
3150 } else if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) {
3153 if (file->f_path.dentry) {
3155 dentry = file->f_path.dentry;
3157 if (unlikely(d_is_negative(dentry)))
3163 dentry = ERR_PTR(error);
3169 * Look up and maybe create and open the last component.
3171 * Must be called with parent locked (exclusive in O_CREAT case).
3173 * Returns 0 on success, that is, if
3174 * the file was successfully atomically created (if necessary) and opened, or
3175 * the file was not completely opened at this time, though lookups and
3176 * creations were performed.
3177 * These case are distinguished by presence of FMODE_OPENED on file->f_mode.
3178 * In the latter case dentry returned in @path might be negative if O_CREAT
3179 * hadn't been specified.
3181 * An error code is returned on failure.
3183 static struct dentry *lookup_open(struct nameidata *nd, struct file *file,
3184 const struct open_flags *op,
3187 struct user_namespace *mnt_userns;
3188 struct dentry *dir = nd->path.dentry;
3189 struct inode *dir_inode = dir->d_inode;
3190 int open_flag = op->open_flag;
3191 struct dentry *dentry;
3192 int error, create_error = 0;
3193 umode_t mode = op->mode;
3194 DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
3196 if (unlikely(IS_DEADDIR(dir_inode)))
3197 return ERR_PTR(-ENOENT);
3199 file->f_mode &= ~FMODE_CREATED;
3200 dentry = d_lookup(dir, &nd->last);
3203 dentry = d_alloc_parallel(dir, &nd->last, &wq);
3207 if (d_in_lookup(dentry))
3210 error = d_revalidate(dentry, nd->flags);
3211 if (likely(error > 0))
3215 d_invalidate(dentry);
3219 if (dentry->d_inode) {
3220 /* Cached positive dentry: will open in f_op->open */
3225 * Checking write permission is tricky, bacuse we don't know if we are
3226 * going to actually need it: O_CREAT opens should work as long as the
3227 * file exists. But checking existence breaks atomicity. The trick is
3228 * to check access and if not granted clear O_CREAT from the flags.
3230 * Another problem is returing the "right" error value (e.g. for an
3231 * O_EXCL open we want to return EEXIST not EROFS).
3233 if (unlikely(!got_write))
3234 open_flag &= ~O_TRUNC;
3235 mnt_userns = mnt_user_ns(nd->path.mnt);
3236 if (open_flag & O_CREAT) {
3237 if (open_flag & O_EXCL)
3238 open_flag &= ~O_TRUNC;
3239 if (!IS_POSIXACL(dir->d_inode))
3240 mode &= ~current_umask();
3241 if (likely(got_write))
3242 create_error = may_o_create(mnt_userns, &nd->path,
3245 create_error = -EROFS;
3248 open_flag &= ~O_CREAT;
3249 if (dir_inode->i_op->atomic_open) {
3250 dentry = atomic_open(nd, dentry, file, open_flag, mode);
3251 if (unlikely(create_error) && dentry == ERR_PTR(-ENOENT))
3252 dentry = ERR_PTR(create_error);
3256 if (d_in_lookup(dentry)) {
3257 struct dentry *res = dir_inode->i_op->lookup(dir_inode, dentry,
3259 d_lookup_done(dentry);
3260 if (unlikely(res)) {
3262 error = PTR_ERR(res);
3270 /* Negative dentry, just create the file */
3271 if (!dentry->d_inode && (open_flag & O_CREAT)) {
3272 file->f_mode |= FMODE_CREATED;
3273 audit_inode_child(dir_inode, dentry, AUDIT_TYPE_CHILD_CREATE);
3274 if (!dir_inode->i_op->create) {
3279 error = dir_inode->i_op->create(mnt_userns, dir_inode, dentry,
3280 mode, open_flag & O_EXCL);
3284 if (unlikely(create_error) && !dentry->d_inode) {
3285 error = create_error;
3292 return ERR_PTR(error);
3295 static const char *open_last_lookups(struct nameidata *nd,
3296 struct file *file, const struct open_flags *op)
3298 struct dentry *dir = nd->path.dentry;
3299 int open_flag = op->open_flag;
3300 bool got_write = false;
3302 struct inode *inode;
3303 struct dentry *dentry;
3306 nd->flags |= op->intent;
3308 if (nd->last_type != LAST_NORM) {
3311 return handle_dots(nd, nd->last_type);
3314 if (!(open_flag & O_CREAT)) {
3315 if (nd->last.name[nd->last.len])
3316 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
3317 /* we _can_ be in RCU mode here */
3318 dentry = lookup_fast(nd, &inode, &seq);
3320 return ERR_CAST(dentry);
3324 BUG_ON(nd->flags & LOOKUP_RCU);
3326 /* create side of things */
3327 if (nd->flags & LOOKUP_RCU) {
3328 if (!try_to_unlazy(nd))
3329 return ERR_PTR(-ECHILD);
3331 audit_inode(nd->name, dir, AUDIT_INODE_PARENT);
3332 /* trailing slashes? */
3333 if (unlikely(nd->last.name[nd->last.len]))
3334 return ERR_PTR(-EISDIR);
3337 if (open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
3338 got_write = !mnt_want_write(nd->path.mnt);
3340 * do _not_ fail yet - we might not need that or fail with
3341 * a different error; let lookup_open() decide; we'll be
3342 * dropping this one anyway.
3345 if (open_flag & O_CREAT)
3346 inode_lock(dir->d_inode);
3348 inode_lock_shared(dir->d_inode);
3349 dentry = lookup_open(nd, file, op, got_write);
3350 if (!IS_ERR(dentry) && (file->f_mode & FMODE_CREATED))
3351 fsnotify_create(dir->d_inode, dentry);
3352 if (open_flag & O_CREAT)
3353 inode_unlock(dir->d_inode);
3355 inode_unlock_shared(dir->d_inode);
3358 mnt_drop_write(nd->path.mnt);
3361 return ERR_CAST(dentry);
3363 if (file->f_mode & (FMODE_OPENED | FMODE_CREATED)) {
3364 dput(nd->path.dentry);
3365 nd->path.dentry = dentry;
3372 res = step_into(nd, WALK_TRAILING, dentry, inode, seq);
3374 nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
3379 * Handle the last step of open()
3381 static int do_open(struct nameidata *nd,
3382 struct file *file, const struct open_flags *op)
3384 struct user_namespace *mnt_userns;
3385 int open_flag = op->open_flag;
3390 if (!(file->f_mode & (FMODE_OPENED | FMODE_CREATED))) {
3391 error = complete_walk(nd);
3395 if (!(file->f_mode & FMODE_CREATED))
3396 audit_inode(nd->name, nd->path.dentry, 0);
3397 mnt_userns = mnt_user_ns(nd->path.mnt);
3398 if (open_flag & O_CREAT) {
3399 if ((open_flag & O_EXCL) && !(file->f_mode & FMODE_CREATED))
3401 if (d_is_dir(nd->path.dentry))
3403 error = may_create_in_sticky(mnt_userns, nd,
3404 d_backing_inode(nd->path.dentry));
3405 if (unlikely(error))
3408 if ((nd->flags & LOOKUP_DIRECTORY) && !d_can_lookup(nd->path.dentry))
3411 do_truncate = false;
3412 acc_mode = op->acc_mode;
3413 if (file->f_mode & FMODE_CREATED) {
3414 /* Don't check for write permission, don't truncate */
3415 open_flag &= ~O_TRUNC;
3417 } else if (d_is_reg(nd->path.dentry) && open_flag & O_TRUNC) {
3418 error = mnt_want_write(nd->path.mnt);
3423 error = may_open(mnt_userns, &nd->path, acc_mode, open_flag);
3424 if (!error && !(file->f_mode & FMODE_OPENED))
3425 error = vfs_open(&nd->path, file);
3427 error = ima_file_check(file, op->acc_mode);
3428 if (!error && do_truncate)
3429 error = handle_truncate(mnt_userns, file);
3430 if (unlikely(error > 0)) {
3435 mnt_drop_write(nd->path.mnt);
3440 * vfs_tmpfile - create tmpfile
3441 * @mnt_userns: user namespace of the mount the inode was found from
3442 * @dentry: pointer to dentry of the base directory
3443 * @mode: mode of the new tmpfile
3446 * Create a temporary file.
3448 * If the inode has been found through an idmapped mount the user namespace of
3449 * the vfsmount must be passed through @mnt_userns. This function will then take
3450 * care to map the inode according to @mnt_userns before checking permissions.
3451 * On non-idmapped mounts or if permission checking is to be performed on the
3452 * raw inode simply passs init_user_ns.
3454 struct dentry *vfs_tmpfile(struct user_namespace *mnt_userns,
3455 struct dentry *dentry, umode_t mode, int open_flag)
3457 struct dentry *child = NULL;
3458 struct inode *dir = dentry->d_inode;
3459 struct inode *inode;
3462 /* we want directory to be writable */
3463 error = inode_permission(mnt_userns, dir, MAY_WRITE | MAY_EXEC);
3466 error = -EOPNOTSUPP;
3467 if (!dir->i_op->tmpfile)
3470 child = d_alloc(dentry, &slash_name);
3471 if (unlikely(!child))
3473 error = dir->i_op->tmpfile(mnt_userns, dir, child, mode);
3477 inode = child->d_inode;
3478 if (unlikely(!inode))
3480 if (!(open_flag & O_EXCL)) {
3481 spin_lock(&inode->i_lock);
3482 inode->i_state |= I_LINKABLE;
3483 spin_unlock(&inode->i_lock);
3485 ima_post_create_tmpfile(mnt_userns, inode);
3490 return ERR_PTR(error);
3492 EXPORT_SYMBOL(vfs_tmpfile);
3494 static int do_tmpfile(struct nameidata *nd, unsigned flags,
3495 const struct open_flags *op,
3498 struct user_namespace *mnt_userns;
3499 struct dentry *child;
3501 int error = path_lookupat(nd, flags | LOOKUP_DIRECTORY, &path);
3502 if (unlikely(error))
3504 error = mnt_want_write(path.mnt);
3505 if (unlikely(error))
3507 mnt_userns = mnt_user_ns(path.mnt);
3508 child = vfs_tmpfile(mnt_userns, path.dentry, op->mode, op->open_flag);
3509 error = PTR_ERR(child);
3513 path.dentry = child;
3514 audit_inode(nd->name, child, 0);
3515 /* Don't check for other permissions, the inode was just created */
3516 error = may_open(mnt_userns, &path, 0, op->open_flag);
3518 error = vfs_open(&path, file);
3520 mnt_drop_write(path.mnt);
3526 static int do_o_path(struct nameidata *nd, unsigned flags, struct file *file)
3529 int error = path_lookupat(nd, flags, &path);
3531 audit_inode(nd->name, path.dentry, 0);
3532 error = vfs_open(&path, file);
3538 static struct file *path_openat(struct nameidata *nd,
3539 const struct open_flags *op, unsigned flags)
3544 file = alloc_empty_file(op->open_flag, current_cred());
3548 if (unlikely(file->f_flags & __O_TMPFILE)) {
3549 error = do_tmpfile(nd, flags, op, file);
3550 } else if (unlikely(file->f_flags & O_PATH)) {
3551 error = do_o_path(nd, flags, file);
3553 const char *s = path_init(nd, flags);
3554 while (!(error = link_path_walk(s, nd)) &&
3555 (s = open_last_lookups(nd, file, op)) != NULL)
3558 error = do_open(nd, file, op);
3561 if (likely(!error)) {
3562 if (likely(file->f_mode & FMODE_OPENED))
3568 if (error == -EOPENSTALE) {
3569 if (flags & LOOKUP_RCU)
3574 return ERR_PTR(error);
3577 struct file *do_filp_open(int dfd, struct filename *pathname,
3578 const struct open_flags *op)
3580 struct nameidata nd;
3581 int flags = op->lookup_flags;
3584 set_nameidata(&nd, dfd, pathname, NULL);
3585 filp = path_openat(&nd, op, flags | LOOKUP_RCU);
3586 if (unlikely(filp == ERR_PTR(-ECHILD)))
3587 filp = path_openat(&nd, op, flags);
3588 if (unlikely(filp == ERR_PTR(-ESTALE)))
3589 filp = path_openat(&nd, op, flags | LOOKUP_REVAL);
3590 restore_nameidata();
3594 struct file *do_file_open_root(const struct path *root,
3595 const char *name, const struct open_flags *op)
3597 struct nameidata nd;
3599 struct filename *filename;
3600 int flags = op->lookup_flags;
3602 if (d_is_symlink(root->dentry) && op->intent & LOOKUP_OPEN)
3603 return ERR_PTR(-ELOOP);
3605 filename = getname_kernel(name);
3606 if (IS_ERR(filename))
3607 return ERR_CAST(filename);
3609 set_nameidata(&nd, -1, filename, root);
3610 file = path_openat(&nd, op, flags | LOOKUP_RCU);
3611 if (unlikely(file == ERR_PTR(-ECHILD)))
3612 file = path_openat(&nd, op, flags);
3613 if (unlikely(file == ERR_PTR(-ESTALE)))
3614 file = path_openat(&nd, op, flags | LOOKUP_REVAL);
3615 restore_nameidata();
3620 static struct dentry *__filename_create(int dfd, struct filename *name,
3621 struct path *path, unsigned int lookup_flags)
3623 struct dentry *dentry = ERR_PTR(-EEXIST);
3628 bool is_dir = (lookup_flags & LOOKUP_DIRECTORY);
3631 * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any
3632 * other flags passed in are ignored!
3634 lookup_flags &= LOOKUP_REVAL;
3636 error = filename_parentat(dfd, name, lookup_flags, path, &last, &type);
3638 return ERR_PTR(error);
3641 * Yucky last component or no last component at all?
3642 * (foo/., foo/.., /////)
3644 if (unlikely(type != LAST_NORM))
3647 /* don't fail immediately if it's r/o, at least try to report other errors */
3648 err2 = mnt_want_write(path->mnt);
3650 * Do the final lookup.
3652 lookup_flags |= LOOKUP_CREATE | LOOKUP_EXCL;
3653 inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
3654 dentry = __lookup_hash(&last, path->dentry, lookup_flags);
3659 if (d_is_positive(dentry))
3663 * Special case - lookup gave negative, but... we had foo/bar/
3664 * From the vfs_mknod() POV we just have a negative dentry -
3665 * all is fine. Let's be bastards - you had / on the end, you've
3666 * been asking for (non-existent) directory. -ENOENT for you.
3668 if (unlikely(!is_dir && last.name[last.len])) {
3672 if (unlikely(err2)) {
3679 dentry = ERR_PTR(error);
3681 inode_unlock(path->dentry->d_inode);
3683 mnt_drop_write(path->mnt);
3689 static inline struct dentry *filename_create(int dfd, struct filename *name,
3690 struct path *path, unsigned int lookup_flags)
3692 struct dentry *res = __filename_create(dfd, name, path, lookup_flags);
3698 struct dentry *kern_path_create(int dfd, const char *pathname,
3699 struct path *path, unsigned int lookup_flags)
3701 return filename_create(dfd, getname_kernel(pathname),
3702 path, lookup_flags);
3704 EXPORT_SYMBOL(kern_path_create);
3706 void done_path_create(struct path *path, struct dentry *dentry)
3709 inode_unlock(path->dentry->d_inode);
3710 mnt_drop_write(path->mnt);
3713 EXPORT_SYMBOL(done_path_create);
3715 inline struct dentry *user_path_create(int dfd, const char __user *pathname,
3716 struct path *path, unsigned int lookup_flags)
3718 return filename_create(dfd, getname(pathname), path, lookup_flags);
3720 EXPORT_SYMBOL(user_path_create);
3723 * vfs_mknod - create device node or file
3724 * @mnt_userns: user namespace of the mount the inode was found from
3725 * @dir: inode of @dentry
3726 * @dentry: pointer to dentry of the base directory
3727 * @mode: mode of the new device node or file
3728 * @dev: device number of device to create
3730 * Create a device node or file.
3732 * If the inode has been found through an idmapped mount the user namespace of
3733 * the vfsmount must be passed through @mnt_userns. This function will then take
3734 * care to map the inode according to @mnt_userns before checking permissions.
3735 * On non-idmapped mounts or if permission checking is to be performed on the
3736 * raw inode simply passs init_user_ns.
3738 int vfs_mknod(struct user_namespace *mnt_userns, struct inode *dir,
3739 struct dentry *dentry, umode_t mode, dev_t dev)
3741 bool is_whiteout = S_ISCHR(mode) && dev == WHITEOUT_DEV;
3742 int error = may_create(mnt_userns, dir, dentry);
3747 if ((S_ISCHR(mode) || S_ISBLK(mode)) && !is_whiteout &&
3748 !capable(CAP_MKNOD))
3751 if (!dir->i_op->mknod)
3754 error = devcgroup_inode_mknod(mode, dev);
3758 error = security_inode_mknod(dir, dentry, mode, dev);
3762 error = dir->i_op->mknod(mnt_userns, dir, dentry, mode, dev);
3764 fsnotify_create(dir, dentry);
3767 EXPORT_SYMBOL(vfs_mknod);
3769 static int may_mknod(umode_t mode)
3771 switch (mode & S_IFMT) {
3777 case 0: /* zero mode translates to S_IFREG */
3786 static int do_mknodat(int dfd, struct filename *name, umode_t mode,
3789 struct user_namespace *mnt_userns;
3790 struct dentry *dentry;
3793 unsigned int lookup_flags = 0;
3795 error = may_mknod(mode);
3799 dentry = __filename_create(dfd, name, &path, lookup_flags);
3800 error = PTR_ERR(dentry);
3804 if (!IS_POSIXACL(path.dentry->d_inode))
3805 mode &= ~current_umask();
3806 error = security_path_mknod(&path, dentry, mode, dev);
3810 mnt_userns = mnt_user_ns(path.mnt);
3811 switch (mode & S_IFMT) {
3812 case 0: case S_IFREG:
3813 error = vfs_create(mnt_userns, path.dentry->d_inode,
3814 dentry, mode, true);
3816 ima_post_path_mknod(mnt_userns, dentry);
3818 case S_IFCHR: case S_IFBLK:
3819 error = vfs_mknod(mnt_userns, path.dentry->d_inode,
3820 dentry, mode, new_decode_dev(dev));
3822 case S_IFIFO: case S_IFSOCK:
3823 error = vfs_mknod(mnt_userns, path.dentry->d_inode,
3828 done_path_create(&path, dentry);
3829 if (retry_estale(error, lookup_flags)) {
3830 lookup_flags |= LOOKUP_REVAL;
3838 SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,
3841 return do_mknodat(dfd, getname(filename), mode, dev);
3844 SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev)
3846 return do_mknodat(AT_FDCWD, getname(filename), mode, dev);
3850 * vfs_mkdir - create directory
3851 * @mnt_userns: user namespace of the mount the inode was found from
3852 * @dir: inode of @dentry
3853 * @dentry: pointer to dentry of the base directory
3854 * @mode: mode of the new directory
3856 * Create a directory.
3858 * If the inode has been found through an idmapped mount the user namespace of
3859 * the vfsmount must be passed through @mnt_userns. This function will then take
3860 * care to map the inode according to @mnt_userns before checking permissions.
3861 * On non-idmapped mounts or if permission checking is to be performed on the
3862 * raw inode simply passs init_user_ns.
3864 int vfs_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
3865 struct dentry *dentry, umode_t mode)
3867 int error = may_create(mnt_userns, dir, dentry);
3868 unsigned max_links = dir->i_sb->s_max_links;
3873 if (!dir->i_op->mkdir)
3876 mode &= (S_IRWXUGO|S_ISVTX);
3877 error = security_inode_mkdir(dir, dentry, mode);
3881 if (max_links && dir->i_nlink >= max_links)
3884 error = dir->i_op->mkdir(mnt_userns, dir, dentry, mode);
3886 fsnotify_mkdir(dir, dentry);
3889 EXPORT_SYMBOL(vfs_mkdir);
3891 int do_mkdirat(int dfd, struct filename *name, umode_t mode)
3893 struct dentry *dentry;
3896 unsigned int lookup_flags = LOOKUP_DIRECTORY;
3899 dentry = __filename_create(dfd, name, &path, lookup_flags);
3900 error = PTR_ERR(dentry);
3904 if (!IS_POSIXACL(path.dentry->d_inode))
3905 mode &= ~current_umask();
3906 error = security_path_mkdir(&path, dentry, mode);
3908 struct user_namespace *mnt_userns;
3909 mnt_userns = mnt_user_ns(path.mnt);
3910 error = vfs_mkdir(mnt_userns, path.dentry->d_inode, dentry,
3913 done_path_create(&path, dentry);
3914 if (retry_estale(error, lookup_flags)) {
3915 lookup_flags |= LOOKUP_REVAL;
3923 SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
3925 return do_mkdirat(dfd, getname(pathname), mode);
3928 SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode)
3930 return do_mkdirat(AT_FDCWD, getname(pathname), mode);
3934 * vfs_rmdir - remove directory
3935 * @mnt_userns: user namespace of the mount the inode was found from
3936 * @dir: inode of @dentry
3937 * @dentry: pointer to dentry of the base directory
3939 * Remove a directory.
3941 * If the inode has been found through an idmapped mount the user namespace of
3942 * the vfsmount must be passed through @mnt_userns. This function will then take
3943 * care to map the inode according to @mnt_userns before checking permissions.
3944 * On non-idmapped mounts or if permission checking is to be performed on the
3945 * raw inode simply passs init_user_ns.
3947 int vfs_rmdir(struct user_namespace *mnt_userns, struct inode *dir,
3948 struct dentry *dentry)
3950 int error = may_delete(mnt_userns, dir, dentry, 1);
3955 if (!dir->i_op->rmdir)
3959 inode_lock(dentry->d_inode);
3962 if (is_local_mountpoint(dentry))
3965 error = security_inode_rmdir(dir, dentry);
3969 error = dir->i_op->rmdir(dir, dentry);
3973 shrink_dcache_parent(dentry);
3974 dentry->d_inode->i_flags |= S_DEAD;
3976 detach_mounts(dentry);
3977 fsnotify_rmdir(dir, dentry);
3980 inode_unlock(dentry->d_inode);
3986 EXPORT_SYMBOL(vfs_rmdir);
3988 int do_rmdir(int dfd, struct filename *name)
3990 struct user_namespace *mnt_userns;
3992 struct dentry *dentry;
3996 unsigned int lookup_flags = 0;
3998 error = filename_parentat(dfd, name, lookup_flags, &path, &last, &type);
4014 error = mnt_want_write(path.mnt);
4018 inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT);
4019 dentry = __lookup_hash(&last, path.dentry, lookup_flags);
4020 error = PTR_ERR(dentry);
4023 if (!dentry->d_inode) {
4027 error = security_path_rmdir(&path, dentry);
4030 mnt_userns = mnt_user_ns(path.mnt);
4031 error = vfs_rmdir(mnt_userns, path.dentry->d_inode, dentry);
4035 inode_unlock(path.dentry->d_inode);
4036 mnt_drop_write(path.mnt);
4039 if (retry_estale(error, lookup_flags)) {
4040 lookup_flags |= LOOKUP_REVAL;
4048 SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
4050 return do_rmdir(AT_FDCWD, getname(pathname));
4054 * vfs_unlink - unlink a filesystem object
4055 * @mnt_userns: user namespace of the mount the inode was found from
4056 * @dir: parent directory
4058 * @delegated_inode: returns victim inode, if the inode is delegated.
4060 * The caller must hold dir->i_mutex.
4062 * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and
4063 * return a reference to the inode in delegated_inode. The caller
4064 * should then break the delegation on that inode and retry. Because
4065 * breaking a delegation may take a long time, the caller should drop
4066 * dir->i_mutex before doing so.
4068 * Alternatively, a caller may pass NULL for delegated_inode. This may
4069 * be appropriate for callers that expect the underlying filesystem not
4070 * to be NFS exported.
4072 * If the inode has been found through an idmapped mount the user namespace of
4073 * the vfsmount must be passed through @mnt_userns. This function will then take
4074 * care to map the inode according to @mnt_userns before checking permissions.
4075 * On non-idmapped mounts or if permission checking is to be performed on the
4076 * raw inode simply passs init_user_ns.
4078 int vfs_unlink(struct user_namespace *mnt_userns, struct inode *dir,
4079 struct dentry *dentry, struct inode **delegated_inode)
4081 struct inode *target = dentry->d_inode;
4082 int error = may_delete(mnt_userns, dir, dentry, 0);
4087 if (!dir->i_op->unlink)
4091 if (IS_SWAPFILE(target))
4093 else if (is_local_mountpoint(dentry))
4096 error = security_inode_unlink(dir, dentry);
4098 error = try_break_deleg(target, delegated_inode);
4101 error = dir->i_op->unlink(dir, dentry);
4104 detach_mounts(dentry);
4105 fsnotify_unlink(dir, dentry);
4110 inode_unlock(target);
4112 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
4113 if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
4114 fsnotify_link_count(target);
4120 EXPORT_SYMBOL(vfs_unlink);
4123 * Make sure that the actual truncation of the file will occur outside its
4124 * directory's i_mutex. Truncate can take a long time if there is a lot of
4125 * writeout happening, and we don't want to prevent access to the directory
4126 * while waiting on the I/O.
4128 int do_unlinkat(int dfd, struct filename *name)
4131 struct dentry *dentry;
4135 struct inode *inode = NULL;
4136 struct inode *delegated_inode = NULL;
4137 unsigned int lookup_flags = 0;
4139 error = filename_parentat(dfd, name, lookup_flags, &path, &last, &type);
4144 if (type != LAST_NORM)
4147 error = mnt_want_write(path.mnt);
4151 inode_lock_nested(path.dentry->d_inode, I_MUTEX_PARENT);
4152 dentry = __lookup_hash(&last, path.dentry, lookup_flags);
4153 error = PTR_ERR(dentry);
4154 if (!IS_ERR(dentry)) {
4155 struct user_namespace *mnt_userns;
4157 /* Why not before? Because we want correct error value */
4158 if (last.name[last.len])
4160 inode = dentry->d_inode;
4161 if (d_is_negative(dentry))
4164 error = security_path_unlink(&path, dentry);
4167 mnt_userns = mnt_user_ns(path.mnt);
4168 error = vfs_unlink(mnt_userns, path.dentry->d_inode, dentry,
4173 inode_unlock(path.dentry->d_inode);
4175 iput(inode); /* truncate the inode here */
4177 if (delegated_inode) {
4178 error = break_deleg_wait(&delegated_inode);
4182 mnt_drop_write(path.mnt);
4185 if (retry_estale(error, lookup_flags)) {
4186 lookup_flags |= LOOKUP_REVAL;
4195 if (d_is_negative(dentry))
4197 else if (d_is_dir(dentry))
4204 SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
4206 if ((flag & ~AT_REMOVEDIR) != 0)
4209 if (flag & AT_REMOVEDIR)
4210 return do_rmdir(dfd, getname(pathname));
4211 return do_unlinkat(dfd, getname(pathname));
4214 SYSCALL_DEFINE1(unlink, const char __user *, pathname)
4216 return do_unlinkat(AT_FDCWD, getname(pathname));
4220 * vfs_symlink - create symlink
4221 * @mnt_userns: user namespace of the mount the inode was found from
4222 * @dir: inode of @dentry
4223 * @dentry: pointer to dentry of the base directory
4224 * @oldname: name of the file to link to
4228 * If the inode has been found through an idmapped mount the user namespace of
4229 * the vfsmount must be passed through @mnt_userns. This function will then take
4230 * care to map the inode according to @mnt_userns before checking permissions.
4231 * On non-idmapped mounts or if permission checking is to be performed on the
4232 * raw inode simply passs init_user_ns.
4234 int vfs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
4235 struct dentry *dentry, const char *oldname)
4237 int error = may_create(mnt_userns, dir, dentry);
4242 if (!dir->i_op->symlink)
4245 error = security_inode_symlink(dir, dentry, oldname);
4249 error = dir->i_op->symlink(mnt_userns, dir, dentry, oldname);
4251 fsnotify_create(dir, dentry);
4254 EXPORT_SYMBOL(vfs_symlink);
4256 int do_symlinkat(struct filename *from, int newdfd, struct filename *to)
4259 struct dentry *dentry;
4261 unsigned int lookup_flags = 0;
4264 error = PTR_ERR(from);
4268 dentry = __filename_create(newdfd, to, &path, lookup_flags);
4269 error = PTR_ERR(dentry);
4273 error = security_path_symlink(&path, dentry, from->name);
4275 struct user_namespace *mnt_userns;
4277 mnt_userns = mnt_user_ns(path.mnt);
4278 error = vfs_symlink(mnt_userns, path.dentry->d_inode, dentry,
4281 done_path_create(&path, dentry);
4282 if (retry_estale(error, lookup_flags)) {
4283 lookup_flags |= LOOKUP_REVAL;
4292 SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
4293 int, newdfd, const char __user *, newname)
4295 return do_symlinkat(getname(oldname), newdfd, getname(newname));
4298 SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
4300 return do_symlinkat(getname(oldname), AT_FDCWD, getname(newname));
4304 * vfs_link - create a new link
4305 * @old_dentry: object to be linked
4306 * @mnt_userns: the user namespace of the mount
4308 * @new_dentry: where to create the new link
4309 * @delegated_inode: returns inode needing a delegation break
4311 * The caller must hold dir->i_mutex
4313 * If vfs_link discovers a delegation on the to-be-linked file in need
4314 * of breaking, it will return -EWOULDBLOCK and return a reference to the
4315 * inode in delegated_inode. The caller should then break the delegation
4316 * and retry. Because breaking a delegation may take a long time, the
4317 * caller should drop the i_mutex before doing so.
4319 * Alternatively, a caller may pass NULL for delegated_inode. This may
4320 * be appropriate for callers that expect the underlying filesystem not
4321 * to be NFS exported.
4323 * If the inode has been found through an idmapped mount the user namespace of
4324 * the vfsmount must be passed through @mnt_userns. This function will then take
4325 * care to map the inode according to @mnt_userns before checking permissions.
4326 * On non-idmapped mounts or if permission checking is to be performed on the
4327 * raw inode simply passs init_user_ns.
4329 int vfs_link(struct dentry *old_dentry, struct user_namespace *mnt_userns,
4330 struct inode *dir, struct dentry *new_dentry,
4331 struct inode **delegated_inode)
4333 struct inode *inode = old_dentry->d_inode;
4334 unsigned max_links = dir->i_sb->s_max_links;
4340 error = may_create(mnt_userns, dir, new_dentry);
4344 if (dir->i_sb != inode->i_sb)
4348 * A link to an append-only or immutable file cannot be created.
4350 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
4353 * Updating the link count will likely cause i_uid and i_gid to
4354 * be writen back improperly if their true value is unknown to
4357 if (HAS_UNMAPPED_ID(mnt_userns, inode))
4359 if (!dir->i_op->link)
4361 if (S_ISDIR(inode->i_mode))
4364 error = security_inode_link(old_dentry, dir, new_dentry);
4369 /* Make sure we don't allow creating hardlink to an unlinked file */
4370 if (inode->i_nlink == 0 && !(inode->i_state & I_LINKABLE))
4372 else if (max_links && inode->i_nlink >= max_links)
4375 error = try_break_deleg(inode, delegated_inode);
4377 error = dir->i_op->link(old_dentry, dir, new_dentry);
4380 if (!error && (inode->i_state & I_LINKABLE)) {
4381 spin_lock(&inode->i_lock);
4382 inode->i_state &= ~I_LINKABLE;
4383 spin_unlock(&inode->i_lock);
4385 inode_unlock(inode);
4387 fsnotify_link(dir, inode, new_dentry);
4390 EXPORT_SYMBOL(vfs_link);
4393 * Hardlinks are often used in delicate situations. We avoid
4394 * security-related surprises by not following symlinks on the
4397 * We don't follow them on the oldname either to be compatible
4398 * with linux 2.0, and to avoid hard-linking to directories
4399 * and other special files. --ADM
4401 int do_linkat(int olddfd, struct filename *old, int newdfd,
4402 struct filename *new, int flags)
4404 struct user_namespace *mnt_userns;
4405 struct dentry *new_dentry;
4406 struct path old_path, new_path;
4407 struct inode *delegated_inode = NULL;
4411 if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0) {
4416 * To use null names we require CAP_DAC_READ_SEARCH
4417 * This ensures that not everyone will be able to create
4418 * handlink using the passed filedescriptor.
4420 if (flags & AT_EMPTY_PATH && !capable(CAP_DAC_READ_SEARCH)) {
4425 if (flags & AT_SYMLINK_FOLLOW)
4426 how |= LOOKUP_FOLLOW;
4428 error = __filename_lookup(olddfd, old, how, &old_path, NULL);
4432 new_dentry = __filename_create(newdfd, new, &new_path,
4433 (how & LOOKUP_REVAL));
4434 error = PTR_ERR(new_dentry);
4435 if (IS_ERR(new_dentry))
4439 if (old_path.mnt != new_path.mnt)
4441 mnt_userns = mnt_user_ns(new_path.mnt);
4442 error = may_linkat(mnt_userns, &old_path);
4443 if (unlikely(error))
4445 error = security_path_link(old_path.dentry, &new_path, new_dentry);
4448 error = vfs_link(old_path.dentry, mnt_userns, new_path.dentry->d_inode,
4449 new_dentry, &delegated_inode);
4451 done_path_create(&new_path, new_dentry);
4452 if (delegated_inode) {
4453 error = break_deleg_wait(&delegated_inode);
4455 path_put(&old_path);
4459 if (retry_estale(error, how)) {
4460 path_put(&old_path);
4461 how |= LOOKUP_REVAL;
4465 path_put(&old_path);
4473 SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
4474 int, newdfd, const char __user *, newname, int, flags)
4476 return do_linkat(olddfd, getname_uflags(oldname, flags),
4477 newdfd, getname(newname), flags);
4480 SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
4482 return do_linkat(AT_FDCWD, getname(oldname), AT_FDCWD, getname(newname), 0);
4486 * vfs_rename - rename a filesystem object
4487 * @rd: pointer to &struct renamedata info
4489 * The caller must hold multiple mutexes--see lock_rename()).
4491 * If vfs_rename discovers a delegation in need of breaking at either
4492 * the source or destination, it will return -EWOULDBLOCK and return a
4493 * reference to the inode in delegated_inode. The caller should then
4494 * break the delegation and retry. Because breaking a delegation may
4495 * take a long time, the caller should drop all locks before doing
4498 * Alternatively, a caller may pass NULL for delegated_inode. This may
4499 * be appropriate for callers that expect the underlying filesystem not
4500 * to be NFS exported.
4502 * The worst of all namespace operations - renaming directory. "Perverted"
4503 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
4506 * a) we can get into loop creation.
4507 * b) race potential - two innocent renames can create a loop together.
4508 * That's where 4.4 screws up. Current fix: serialization on
4509 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
4511 * c) we have to lock _four_ objects - parents and victim (if it exists),
4512 * and source (if it is not a directory).
4513 * And that - after we got ->i_mutex on parents (until then we don't know
4514 * whether the target exists). Solution: try to be smart with locking
4515 * order for inodes. We rely on the fact that tree topology may change
4516 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
4517 * move will be locked. Thus we can rank directories by the tree
4518 * (ancestors first) and rank all non-directories after them.
4519 * That works since everybody except rename does "lock parent, lookup,
4520 * lock child" and rename is under ->s_vfs_rename_mutex.
4521 * HOWEVER, it relies on the assumption that any object with ->lookup()
4522 * has no more than 1 dentry. If "hybrid" objects will ever appear,
4523 * we'd better make sure that there's no link(2) for them.
4524 * d) conversion from fhandle to dentry may come in the wrong moment - when
4525 * we are removing the target. Solution: we will have to grab ->i_mutex
4526 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
4527 * ->i_mutex on parents, which works but leads to some truly excessive
4530 int vfs_rename(struct renamedata *rd)
4533 struct inode *old_dir = rd->old_dir, *new_dir = rd->new_dir;
4534 struct dentry *old_dentry = rd->old_dentry;
4535 struct dentry *new_dentry = rd->new_dentry;
4536 struct inode **delegated_inode = rd->delegated_inode;
4537 unsigned int flags = rd->flags;
4538 bool is_dir = d_is_dir(old_dentry);
4539 struct inode *source = old_dentry->d_inode;
4540 struct inode *target = new_dentry->d_inode;
4541 bool new_is_dir = false;
4542 unsigned max_links = new_dir->i_sb->s_max_links;
4543 struct name_snapshot old_name;
4545 if (source == target)
4548 error = may_delete(rd->old_mnt_userns, old_dir, old_dentry, is_dir);
4553 error = may_create(rd->new_mnt_userns, new_dir, new_dentry);
4555 new_is_dir = d_is_dir(new_dentry);
4557 if (!(flags & RENAME_EXCHANGE))
4558 error = may_delete(rd->new_mnt_userns, new_dir,
4559 new_dentry, is_dir);
4561 error = may_delete(rd->new_mnt_userns, new_dir,
4562 new_dentry, new_is_dir);
4567 if (!old_dir->i_op->rename)
4571 * If we are going to change the parent - check write permissions,
4572 * we'll need to flip '..'.
4574 if (new_dir != old_dir) {
4576 error = inode_permission(rd->old_mnt_userns, source,
4581 if ((flags & RENAME_EXCHANGE) && new_is_dir) {
4582 error = inode_permission(rd->new_mnt_userns, target,
4589 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry,
4594 take_dentry_name_snapshot(&old_name, old_dentry);
4596 if (!is_dir || (flags & RENAME_EXCHANGE))
4597 lock_two_nondirectories(source, target);
4602 if (IS_SWAPFILE(source) || (target && IS_SWAPFILE(target)))
4606 if (is_local_mountpoint(old_dentry) || is_local_mountpoint(new_dentry))
4609 if (max_links && new_dir != old_dir) {
4611 if (is_dir && !new_is_dir && new_dir->i_nlink >= max_links)
4613 if ((flags & RENAME_EXCHANGE) && !is_dir && new_is_dir &&
4614 old_dir->i_nlink >= max_links)
4618 error = try_break_deleg(source, delegated_inode);
4622 if (target && !new_is_dir) {
4623 error = try_break_deleg(target, delegated_inode);
4627 error = old_dir->i_op->rename(rd->new_mnt_userns, old_dir, old_dentry,
4628 new_dir, new_dentry, flags);
4632 if (!(flags & RENAME_EXCHANGE) && target) {
4634 shrink_dcache_parent(new_dentry);
4635 target->i_flags |= S_DEAD;
4637 dont_mount(new_dentry);
4638 detach_mounts(new_dentry);
4640 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) {
4641 if (!(flags & RENAME_EXCHANGE))
4642 d_move(old_dentry, new_dentry);
4644 d_exchange(old_dentry, new_dentry);
4647 if (!is_dir || (flags & RENAME_EXCHANGE))
4648 unlock_two_nondirectories(source, target);
4650 inode_unlock(target);
4653 fsnotify_move(old_dir, new_dir, &old_name.name, is_dir,
4654 !(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry);
4655 if (flags & RENAME_EXCHANGE) {
4656 fsnotify_move(new_dir, old_dir, &old_dentry->d_name,
4657 new_is_dir, NULL, new_dentry);
4660 release_dentry_name_snapshot(&old_name);
4664 EXPORT_SYMBOL(vfs_rename);
4666 int do_renameat2(int olddfd, struct filename *from, int newdfd,
4667 struct filename *to, unsigned int flags)
4669 struct renamedata rd;
4670 struct dentry *old_dentry, *new_dentry;
4671 struct dentry *trap;
4672 struct path old_path, new_path;
4673 struct qstr old_last, new_last;
4674 int old_type, new_type;
4675 struct inode *delegated_inode = NULL;
4676 unsigned int lookup_flags = 0, target_flags = LOOKUP_RENAME_TARGET;
4677 bool should_retry = false;
4678 int error = -EINVAL;
4680 if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
4683 if ((flags & (RENAME_NOREPLACE | RENAME_WHITEOUT)) &&
4684 (flags & RENAME_EXCHANGE))
4687 if (flags & RENAME_EXCHANGE)
4691 error = filename_parentat(olddfd, from, lookup_flags, &old_path,
4692 &old_last, &old_type);
4696 error = filename_parentat(newdfd, to, lookup_flags, &new_path, &new_last,
4702 if (old_path.mnt != new_path.mnt)
4706 if (old_type != LAST_NORM)
4709 if (flags & RENAME_NOREPLACE)
4711 if (new_type != LAST_NORM)
4714 error = mnt_want_write(old_path.mnt);
4719 trap = lock_rename(new_path.dentry, old_path.dentry);
4721 old_dentry = __lookup_hash(&old_last, old_path.dentry, lookup_flags);
4722 error = PTR_ERR(old_dentry);
4723 if (IS_ERR(old_dentry))
4725 /* source must exist */
4727 if (d_is_negative(old_dentry))
4729 new_dentry = __lookup_hash(&new_last, new_path.dentry, lookup_flags | target_flags);
4730 error = PTR_ERR(new_dentry);
4731 if (IS_ERR(new_dentry))
4734 if ((flags & RENAME_NOREPLACE) && d_is_positive(new_dentry))
4736 if (flags & RENAME_EXCHANGE) {
4738 if (d_is_negative(new_dentry))
4741 if (!d_is_dir(new_dentry)) {
4743 if (new_last.name[new_last.len])
4747 /* unless the source is a directory trailing slashes give -ENOTDIR */
4748 if (!d_is_dir(old_dentry)) {
4750 if (old_last.name[old_last.len])
4752 if (!(flags & RENAME_EXCHANGE) && new_last.name[new_last.len])
4755 /* source should not be ancestor of target */
4757 if (old_dentry == trap)
4759 /* target should not be an ancestor of source */
4760 if (!(flags & RENAME_EXCHANGE))
4762 if (new_dentry == trap)
4765 error = security_path_rename(&old_path, old_dentry,
4766 &new_path, new_dentry, flags);
4770 rd.old_dir = old_path.dentry->d_inode;
4771 rd.old_dentry = old_dentry;
4772 rd.old_mnt_userns = mnt_user_ns(old_path.mnt);
4773 rd.new_dir = new_path.dentry->d_inode;
4774 rd.new_dentry = new_dentry;
4775 rd.new_mnt_userns = mnt_user_ns(new_path.mnt);
4776 rd.delegated_inode = &delegated_inode;
4778 error = vfs_rename(&rd);
4784 unlock_rename(new_path.dentry, old_path.dentry);
4785 if (delegated_inode) {
4786 error = break_deleg_wait(&delegated_inode);
4790 mnt_drop_write(old_path.mnt);
4792 if (retry_estale(error, lookup_flags))
4793 should_retry = true;
4794 path_put(&new_path);
4796 path_put(&old_path);
4798 should_retry = false;
4799 lookup_flags |= LOOKUP_REVAL;
4808 SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname,
4809 int, newdfd, const char __user *, newname, unsigned int, flags)
4811 return do_renameat2(olddfd, getname(oldname), newdfd, getname(newname),
4815 SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
4816 int, newdfd, const char __user *, newname)
4818 return do_renameat2(olddfd, getname(oldname), newdfd, getname(newname),
4822 SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
4824 return do_renameat2(AT_FDCWD, getname(oldname), AT_FDCWD,
4825 getname(newname), 0);
4828 int readlink_copy(char __user *buffer, int buflen, const char *link)
4830 int len = PTR_ERR(link);
4835 if (len > (unsigned) buflen)
4837 if (copy_to_user(buffer, link, len))
4844 * vfs_readlink - copy symlink body into userspace buffer
4845 * @dentry: dentry on which to get symbolic link
4846 * @buffer: user memory pointer
4847 * @buflen: size of buffer
4849 * Does not touch atime. That's up to the caller if necessary
4851 * Does not call security hook.
4853 int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen)
4855 struct inode *inode = d_inode(dentry);
4856 DEFINE_DELAYED_CALL(done);
4860 if (unlikely(!(inode->i_opflags & IOP_DEFAULT_READLINK))) {
4861 if (unlikely(inode->i_op->readlink))
4862 return inode->i_op->readlink(dentry, buffer, buflen);
4864 if (!d_is_symlink(dentry))
4867 spin_lock(&inode->i_lock);
4868 inode->i_opflags |= IOP_DEFAULT_READLINK;
4869 spin_unlock(&inode->i_lock);
4872 link = READ_ONCE(inode->i_link);
4874 link = inode->i_op->get_link(dentry, inode, &done);
4876 return PTR_ERR(link);
4878 res = readlink_copy(buffer, buflen, link);
4879 do_delayed_call(&done);
4882 EXPORT_SYMBOL(vfs_readlink);
4885 * vfs_get_link - get symlink body
4886 * @dentry: dentry on which to get symbolic link
4887 * @done: caller needs to free returned data with this
4889 * Calls security hook and i_op->get_link() on the supplied inode.
4891 * It does not touch atime. That's up to the caller if necessary.
4893 * Does not work on "special" symlinks like /proc/$$/fd/N
4895 const char *vfs_get_link(struct dentry *dentry, struct delayed_call *done)
4897 const char *res = ERR_PTR(-EINVAL);
4898 struct inode *inode = d_inode(dentry);
4900 if (d_is_symlink(dentry)) {
4901 res = ERR_PTR(security_inode_readlink(dentry));
4903 res = inode->i_op->get_link(dentry, inode, done);
4907 EXPORT_SYMBOL(vfs_get_link);
4909 /* get the link contents into pagecache */
4910 const char *page_get_link(struct dentry *dentry, struct inode *inode,
4911 struct delayed_call *callback)
4915 struct address_space *mapping = inode->i_mapping;
4918 page = find_get_page(mapping, 0);
4920 return ERR_PTR(-ECHILD);
4921 if (!PageUptodate(page)) {
4923 return ERR_PTR(-ECHILD);
4926 page = read_mapping_page(mapping, 0, NULL);
4930 set_delayed_call(callback, page_put_link, page);
4931 BUG_ON(mapping_gfp_mask(mapping) & __GFP_HIGHMEM);
4932 kaddr = page_address(page);
4933 nd_terminate_link(kaddr, inode->i_size, PAGE_SIZE - 1);
4937 EXPORT_SYMBOL(page_get_link);
4939 void page_put_link(void *arg)
4943 EXPORT_SYMBOL(page_put_link);
4945 int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
4947 DEFINE_DELAYED_CALL(done);
4948 int res = readlink_copy(buffer, buflen,
4949 page_get_link(dentry, d_inode(dentry),
4951 do_delayed_call(&done);
4954 EXPORT_SYMBOL(page_readlink);
4957 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
4959 int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
4961 struct address_space *mapping = inode->i_mapping;
4965 unsigned int flags = 0;
4967 flags |= AOP_FLAG_NOFS;
4970 err = pagecache_write_begin(NULL, mapping, 0, len-1,
4971 flags, &page, &fsdata);
4975 memcpy(page_address(page), symname, len-1);
4977 err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
4984 mark_inode_dirty(inode);
4989 EXPORT_SYMBOL(__page_symlink);
4991 int page_symlink(struct inode *inode, const char *symname, int len)
4993 return __page_symlink(inode, symname, len,
4994 !mapping_gfp_constraint(inode->i_mapping, __GFP_FS));
4996 EXPORT_SYMBOL(page_symlink);
4998 const struct inode_operations page_symlink_inode_operations = {
4999 .get_link = page_get_link,
5001 EXPORT_SYMBOL(page_symlink_inode_operations);