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[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / fs / namei.c
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1 /*
2 * linux/fs/namei.c
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 */
7 /*
8 * Some corrections by tytso.
9 */
11 /* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
12 * lookup logic.
14 /* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.
17 #include <linux/init.h>
18 #include <linux/module.h>
19 #include <linux/slab.h>
20 #include <linux/fs.h>
21 #include <linux/namei.h>
22 #include <linux/pagemap.h>
23 #include <linux/fsnotify.h>
24 #include <linux/personality.h>
25 #include <linux/security.h>
26 #include <linux/ima.h>
27 #include <linux/syscalls.h>
28 #include <linux/mount.h>
29 #include <linux/audit.h>
30 #include <linux/capability.h>
31 #include <linux/file.h>
32 #include <linux/fcntl.h>
33 #include <linux/device_cgroup.h>
34 #include <linux/fs_struct.h>
35 #include <asm/uaccess.h>
37 #include "internal.h"
39 /* [Feb-1997 T. Schoebel-Theuer]
40 * Fundamental changes in the pathname lookup mechanisms (namei)
41 * were necessary because of omirr. The reason is that omirr needs
42 * to know the _real_ pathname, not the user-supplied one, in case
43 * of symlinks (and also when transname replacements occur).
45 * The new code replaces the old recursive symlink resolution with
46 * an iterative one (in case of non-nested symlink chains). It does
47 * this with calls to <fs>_follow_link().
48 * As a side effect, dir_namei(), _namei() and follow_link() are now
49 * replaced with a single function lookup_dentry() that can handle all
50 * the special cases of the former code.
52 * With the new dcache, the pathname is stored at each inode, at least as
53 * long as the refcount of the inode is positive. As a side effect, the
54 * size of the dcache depends on the inode cache and thus is dynamic.
56 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
57 * resolution to correspond with current state of the code.
59 * Note that the symlink resolution is not *completely* iterative.
60 * There is still a significant amount of tail- and mid- recursion in
61 * the algorithm. Also, note that <fs>_readlink() is not used in
62 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
63 * may return different results than <fs>_follow_link(). Many virtual
64 * filesystems (including /proc) exhibit this behavior.
67 /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
68 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
69 * and the name already exists in form of a symlink, try to create the new
70 * name indicated by the symlink. The old code always complained that the
71 * name already exists, due to not following the symlink even if its target
72 * is nonexistent. The new semantics affects also mknod() and link() when
73 * the name is a symlink pointing to a non-existant name.
75 * I don't know which semantics is the right one, since I have no access
76 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
77 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
78 * "old" one. Personally, I think the new semantics is much more logical.
79 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
80 * file does succeed in both HP-UX and SunOs, but not in Solaris
81 * and in the old Linux semantics.
84 /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
85 * semantics. See the comments in "open_namei" and "do_link" below.
87 * [10-Sep-98 Alan Modra] Another symlink change.
90 /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
91 * inside the path - always follow.
92 * in the last component in creation/removal/renaming - never follow.
93 * if LOOKUP_FOLLOW passed - follow.
94 * if the pathname has trailing slashes - follow.
95 * otherwise - don't follow.
96 * (applied in that order).
98 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
99 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
100 * During the 2.4 we need to fix the userland stuff depending on it -
101 * hopefully we will be able to get rid of that wart in 2.5. So far only
102 * XEmacs seems to be relying on it...
105 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
106 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
107 * any extra contention...
110 /* In order to reduce some races, while at the same time doing additional
111 * checking and hopefully speeding things up, we copy filenames to the
112 * kernel data space before using them..
114 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
115 * PATH_MAX includes the nul terminator --RR.
117 static int do_getname(const char __user *filename, char *page)
119 int retval;
120 unsigned long len = PATH_MAX;
122 if (!segment_eq(get_fs(), KERNEL_DS)) {
123 if ((unsigned long) filename >= TASK_SIZE)
124 return -EFAULT;
125 if (TASK_SIZE - (unsigned long) filename < PATH_MAX)
126 len = TASK_SIZE - (unsigned long) filename;
129 retval = strncpy_from_user(page, filename, len);
130 if (retval > 0) {
131 if (retval < len)
132 return 0;
133 return -ENAMETOOLONG;
134 } else if (!retval)
135 retval = -ENOENT;
136 return retval;
139 char * getname(const char __user * filename)
141 char *tmp, *result;
143 result = ERR_PTR(-ENOMEM);
144 tmp = __getname();
145 if (tmp) {
146 int retval = do_getname(filename, tmp);
148 result = tmp;
149 if (retval < 0) {
150 __putname(tmp);
151 result = ERR_PTR(retval);
154 audit_getname(result);
155 return result;
158 #ifdef CONFIG_AUDITSYSCALL
159 void putname(const char *name)
161 if (unlikely(!audit_dummy_context()))
162 audit_putname(name);
163 else
164 __putname(name);
166 EXPORT_SYMBOL(putname);
167 #endif
170 * This does basic POSIX ACL permission checking
172 static int acl_permission_check(struct inode *inode, int mask, unsigned int flags,
173 int (*check_acl)(struct inode *inode, int mask, unsigned int flags))
175 umode_t mode = inode->i_mode;
177 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
179 if (current_fsuid() == inode->i_uid)
180 mode >>= 6;
181 else {
182 if (IS_POSIXACL(inode) && (mode & S_IRWXG) && check_acl) {
183 int error = check_acl(inode, mask, flags);
184 if (error != -EAGAIN)
185 return error;
188 if (in_group_p(inode->i_gid))
189 mode >>= 3;
193 * If the DACs are ok we don't need any capability check.
195 if ((mask & ~mode) == 0)
196 return 0;
197 return -EACCES;
201 * generic_permission - check for access rights on a Posix-like filesystem
202 * @inode: inode to check access rights for
203 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
204 * @check_acl: optional callback to check for Posix ACLs
205 * @flags: IPERM_FLAG_ flags.
207 * Used to check for read/write/execute permissions on a file.
208 * We use "fsuid" for this, letting us set arbitrary permissions
209 * for filesystem access without changing the "normal" uids which
210 * are used for other things.
212 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
213 * request cannot be satisfied (eg. requires blocking or too much complexity).
214 * It would then be called again in ref-walk mode.
216 int generic_permission(struct inode *inode, int mask, unsigned int flags,
217 int (*check_acl)(struct inode *inode, int mask, unsigned int flags))
219 int ret;
222 * Do the basic POSIX ACL permission checks.
224 ret = acl_permission_check(inode, mask, flags, check_acl);
225 if (ret != -EACCES)
226 return ret;
229 * Read/write DACs are always overridable.
230 * Executable DACs are overridable if at least one exec bit is set.
232 if (!(mask & MAY_EXEC) || execute_ok(inode))
233 if (capable(CAP_DAC_OVERRIDE))
234 return 0;
237 * Searching includes executable on directories, else just read.
239 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
240 if (mask == MAY_READ || (S_ISDIR(inode->i_mode) && !(mask & MAY_WRITE)))
241 if (capable(CAP_DAC_READ_SEARCH))
242 return 0;
244 return -EACCES;
248 * inode_permission - check for access rights to a given inode
249 * @inode: inode to check permission on
250 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
252 * Used to check for read/write/execute permissions on an inode.
253 * We use "fsuid" for this, letting us set arbitrary permissions
254 * for filesystem access without changing the "normal" uids which
255 * are used for other things.
257 int inode_permission(struct inode *inode, int mask)
259 int retval;
261 if (mask & MAY_WRITE) {
262 umode_t mode = inode->i_mode;
265 * Nobody gets write access to a read-only fs.
267 if (IS_RDONLY(inode) &&
268 (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
269 return -EROFS;
272 * Nobody gets write access to an immutable file.
274 if (IS_IMMUTABLE(inode))
275 return -EACCES;
278 if (inode->i_op->permission)
279 retval = inode->i_op->permission(inode, mask, 0);
280 else
281 retval = generic_permission(inode, mask, 0,
282 inode->i_op->check_acl);
284 if (retval)
285 return retval;
287 retval = devcgroup_inode_permission(inode, mask);
288 if (retval)
289 return retval;
291 return security_inode_permission(inode, mask);
295 * file_permission - check for additional access rights to a given file
296 * @file: file to check access rights for
297 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
299 * Used to check for read/write/execute permissions on an already opened
300 * file.
302 * Note:
303 * Do not use this function in new code. All access checks should
304 * be done using inode_permission().
306 int file_permission(struct file *file, int mask)
308 return inode_permission(file->f_path.dentry->d_inode, mask);
312 * get_write_access() gets write permission for a file.
313 * put_write_access() releases this write permission.
314 * This is used for regular files.
315 * We cannot support write (and maybe mmap read-write shared) accesses and
316 * MAP_DENYWRITE mmappings simultaneously. The i_writecount field of an inode
317 * can have the following values:
318 * 0: no writers, no VM_DENYWRITE mappings
319 * < 0: (-i_writecount) vm_area_structs with VM_DENYWRITE set exist
320 * > 0: (i_writecount) users are writing to the file.
322 * Normally we operate on that counter with atomic_{inc,dec} and it's safe
323 * except for the cases where we don't hold i_writecount yet. Then we need to
324 * use {get,deny}_write_access() - these functions check the sign and refuse
325 * to do the change if sign is wrong. Exclusion between them is provided by
326 * the inode->i_lock spinlock.
329 int get_write_access(struct inode * inode)
331 spin_lock(&inode->i_lock);
332 if (atomic_read(&inode->i_writecount) < 0) {
333 spin_unlock(&inode->i_lock);
334 return -ETXTBSY;
336 atomic_inc(&inode->i_writecount);
337 spin_unlock(&inode->i_lock);
339 return 0;
342 int deny_write_access(struct file * file)
344 struct inode *inode = file->f_path.dentry->d_inode;
346 spin_lock(&inode->i_lock);
347 if (atomic_read(&inode->i_writecount) > 0) {
348 spin_unlock(&inode->i_lock);
349 return -ETXTBSY;
351 atomic_dec(&inode->i_writecount);
352 spin_unlock(&inode->i_lock);
354 return 0;
358 * path_get - get a reference to a path
359 * @path: path to get the reference to
361 * Given a path increment the reference count to the dentry and the vfsmount.
363 void path_get(struct path *path)
365 mntget(path->mnt);
366 dget(path->dentry);
368 EXPORT_SYMBOL(path_get);
371 * path_put - put a reference to a path
372 * @path: path to put the reference to
374 * Given a path decrement the reference count to the dentry and the vfsmount.
376 void path_put(struct path *path)
378 dput(path->dentry);
379 mntput(path->mnt);
381 EXPORT_SYMBOL(path_put);
384 * nameidata_drop_rcu - drop this nameidata out of rcu-walk
385 * @nd: nameidata pathwalk data to drop
386 * Returns: 0 on success, -ECHILD on failure
388 * Path walking has 2 modes, rcu-walk and ref-walk (see
389 * Documentation/filesystems/path-lookup.txt). __drop_rcu* functions attempt
390 * to drop out of rcu-walk mode and take normal reference counts on dentries
391 * and vfsmounts to transition to rcu-walk mode. __drop_rcu* functions take
392 * refcounts at the last known good point before rcu-walk got stuck, so
393 * ref-walk may continue from there. If this is not successful (eg. a seqcount
394 * has changed), then failure is returned and path walk restarts from the
395 * beginning in ref-walk mode.
397 * nameidata_drop_rcu attempts to drop the current nd->path and nd->root into
398 * ref-walk. Must be called from rcu-walk context.
400 static int nameidata_drop_rcu(struct nameidata *nd)
402 struct fs_struct *fs = current->fs;
403 struct dentry *dentry = nd->path.dentry;
405 BUG_ON(!(nd->flags & LOOKUP_RCU));
406 if (nd->root.mnt) {
407 spin_lock(&fs->lock);
408 if (nd->root.mnt != fs->root.mnt ||
409 nd->root.dentry != fs->root.dentry)
410 goto err_root;
412 spin_lock(&dentry->d_lock);
413 if (!__d_rcu_to_refcount(dentry, nd->seq))
414 goto err;
415 BUG_ON(nd->inode != dentry->d_inode);
416 spin_unlock(&dentry->d_lock);
417 if (nd->root.mnt) {
418 path_get(&nd->root);
419 spin_unlock(&fs->lock);
421 mntget(nd->path.mnt);
423 rcu_read_unlock();
424 br_read_unlock(vfsmount_lock);
425 nd->flags &= ~LOOKUP_RCU;
426 return 0;
427 err:
428 spin_unlock(&dentry->d_lock);
429 err_root:
430 if (nd->root.mnt)
431 spin_unlock(&fs->lock);
432 return -ECHILD;
435 /* Try to drop out of rcu-walk mode if we were in it, otherwise do nothing. */
436 static inline int nameidata_drop_rcu_maybe(struct nameidata *nd)
438 if (nd->flags & LOOKUP_RCU)
439 return nameidata_drop_rcu(nd);
440 return 0;
444 * nameidata_dentry_drop_rcu - drop nameidata and dentry out of rcu-walk
445 * @nd: nameidata pathwalk data to drop
446 * @dentry: dentry to drop
447 * Returns: 0 on success, -ECHILD on failure
449 * nameidata_dentry_drop_rcu attempts to drop the current nd->path and nd->root,
450 * and dentry into ref-walk. @dentry must be a path found by a do_lookup call on
451 * @nd. Must be called from rcu-walk context.
453 static int nameidata_dentry_drop_rcu(struct nameidata *nd, struct dentry *dentry)
455 struct fs_struct *fs = current->fs;
456 struct dentry *parent = nd->path.dentry;
458 BUG_ON(!(nd->flags & LOOKUP_RCU));
459 if (nd->root.mnt) {
460 spin_lock(&fs->lock);
461 if (nd->root.mnt != fs->root.mnt ||
462 nd->root.dentry != fs->root.dentry)
463 goto err_root;
465 spin_lock(&parent->d_lock);
466 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
467 if (!__d_rcu_to_refcount(dentry, nd->seq))
468 goto err;
470 * If the sequence check on the child dentry passed, then the child has
471 * not been removed from its parent. This means the parent dentry must
472 * be valid and able to take a reference at this point.
474 BUG_ON(!IS_ROOT(dentry) && dentry->d_parent != parent);
475 BUG_ON(!parent->d_count);
476 parent->d_count++;
477 spin_unlock(&dentry->d_lock);
478 spin_unlock(&parent->d_lock);
479 if (nd->root.mnt) {
480 path_get(&nd->root);
481 spin_unlock(&fs->lock);
483 mntget(nd->path.mnt);
485 rcu_read_unlock();
486 br_read_unlock(vfsmount_lock);
487 nd->flags &= ~LOOKUP_RCU;
488 return 0;
489 err:
490 spin_unlock(&dentry->d_lock);
491 spin_unlock(&parent->d_lock);
492 err_root:
493 if (nd->root.mnt)
494 spin_unlock(&fs->lock);
495 return -ECHILD;
498 /* Try to drop out of rcu-walk mode if we were in it, otherwise do nothing. */
499 static inline int nameidata_dentry_drop_rcu_maybe(struct nameidata *nd, struct dentry *dentry)
501 if (nd->flags & LOOKUP_RCU)
502 return nameidata_dentry_drop_rcu(nd, dentry);
503 return 0;
507 * nameidata_drop_rcu_last - drop nameidata ending path walk out of rcu-walk
508 * @nd: nameidata pathwalk data to drop
509 * Returns: 0 on success, -ECHILD on failure
511 * nameidata_drop_rcu_last attempts to drop the current nd->path into ref-walk.
512 * nd->path should be the final element of the lookup, so nd->root is discarded.
513 * Must be called from rcu-walk context.
515 static int nameidata_drop_rcu_last(struct nameidata *nd)
517 struct dentry *dentry = nd->path.dentry;
519 BUG_ON(!(nd->flags & LOOKUP_RCU));
520 nd->flags &= ~LOOKUP_RCU;
521 nd->root.mnt = NULL;
522 spin_lock(&dentry->d_lock);
523 if (!__d_rcu_to_refcount(dentry, nd->seq))
524 goto err_unlock;
525 BUG_ON(nd->inode != dentry->d_inode);
526 spin_unlock(&dentry->d_lock);
528 mntget(nd->path.mnt);
530 rcu_read_unlock();
531 br_read_unlock(vfsmount_lock);
533 return 0;
535 err_unlock:
536 spin_unlock(&dentry->d_lock);
537 rcu_read_unlock();
538 br_read_unlock(vfsmount_lock);
539 return -ECHILD;
542 /* Try to drop out of rcu-walk mode if we were in it, otherwise do nothing. */
543 static inline int nameidata_drop_rcu_last_maybe(struct nameidata *nd)
545 if (likely(nd->flags & LOOKUP_RCU))
546 return nameidata_drop_rcu_last(nd);
547 return 0;
551 * release_open_intent - free up open intent resources
552 * @nd: pointer to nameidata
554 void release_open_intent(struct nameidata *nd)
556 struct file *file = nd->intent.open.file;
558 if (file && !IS_ERR(file)) {
559 if (file->f_path.dentry == NULL)
560 put_filp(file);
561 else
562 fput(file);
566 static inline int d_revalidate(struct dentry *dentry, struct nameidata *nd)
568 return dentry->d_op->d_revalidate(dentry, nd);
571 static struct dentry *
572 do_revalidate(struct dentry *dentry, struct nameidata *nd)
574 int status = d_revalidate(dentry, nd);
575 if (unlikely(status <= 0)) {
577 * The dentry failed validation.
578 * If d_revalidate returned 0 attempt to invalidate
579 * the dentry otherwise d_revalidate is asking us
580 * to return a fail status.
582 if (status < 0) {
583 dput(dentry);
584 dentry = ERR_PTR(status);
585 } else if (!d_invalidate(dentry)) {
586 dput(dentry);
587 dentry = NULL;
590 return dentry;
593 static inline struct dentry *
594 do_revalidate_rcu(struct dentry *dentry, struct nameidata *nd)
596 int status = d_revalidate(dentry, nd);
597 if (likely(status > 0))
598 return dentry;
599 if (status == -ECHILD) {
600 if (nameidata_dentry_drop_rcu(nd, dentry))
601 return ERR_PTR(-ECHILD);
602 return do_revalidate(dentry, nd);
604 if (status < 0)
605 return ERR_PTR(status);
606 /* Don't d_invalidate in rcu-walk mode */
607 if (nameidata_dentry_drop_rcu(nd, dentry))
608 return ERR_PTR(-ECHILD);
609 if (!d_invalidate(dentry)) {
610 dput(dentry);
611 dentry = NULL;
613 return dentry;
616 static inline int need_reval_dot(struct dentry *dentry)
618 if (likely(!(dentry->d_flags & DCACHE_OP_REVALIDATE)))
619 return 0;
621 if (likely(!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)))
622 return 0;
624 return 1;
628 * force_reval_path - force revalidation of a dentry
630 * In some situations the path walking code will trust dentries without
631 * revalidating them. This causes problems for filesystems that depend on
632 * d_revalidate to handle file opens (e.g. NFSv4). When FS_REVAL_DOT is set
633 * (which indicates that it's possible for the dentry to go stale), force
634 * a d_revalidate call before proceeding.
636 * Returns 0 if the revalidation was successful. If the revalidation fails,
637 * either return the error returned by d_revalidate or -ESTALE if the
638 * revalidation it just returned 0. If d_revalidate returns 0, we attempt to
639 * invalidate the dentry. It's up to the caller to handle putting references
640 * to the path if necessary.
642 static int
643 force_reval_path(struct path *path, struct nameidata *nd)
645 int status;
646 struct dentry *dentry = path->dentry;
649 * only check on filesystems where it's possible for the dentry to
650 * become stale.
652 if (!need_reval_dot(dentry))
653 return 0;
655 status = d_revalidate(dentry, nd);
656 if (status > 0)
657 return 0;
659 if (!status) {
660 d_invalidate(dentry);
661 status = -ESTALE;
663 return status;
667 * Short-cut version of permission(), for calling on directories
668 * during pathname resolution. Combines parts of permission()
669 * and generic_permission(), and tests ONLY for MAY_EXEC permission.
671 * If appropriate, check DAC only. If not appropriate, or
672 * short-cut DAC fails, then call ->permission() to do more
673 * complete permission check.
675 static inline int exec_permission(struct inode *inode, unsigned int flags)
677 int ret;
679 if (inode->i_op->permission) {
680 ret = inode->i_op->permission(inode, MAY_EXEC, flags);
681 } else {
682 ret = acl_permission_check(inode, MAY_EXEC, flags,
683 inode->i_op->check_acl);
685 if (likely(!ret))
686 goto ok;
687 if (ret == -ECHILD)
688 return ret;
690 if (capable(CAP_DAC_OVERRIDE) || capable(CAP_DAC_READ_SEARCH))
691 goto ok;
693 return ret;
695 return security_inode_exec_permission(inode, flags);
698 static __always_inline void set_root(struct nameidata *nd)
700 if (!nd->root.mnt)
701 get_fs_root(current->fs, &nd->root);
704 static int link_path_walk(const char *, struct nameidata *);
706 static __always_inline void set_root_rcu(struct nameidata *nd)
708 if (!nd->root.mnt) {
709 struct fs_struct *fs = current->fs;
710 unsigned seq;
712 do {
713 seq = read_seqcount_begin(&fs->seq);
714 nd->root = fs->root;
715 } while (read_seqcount_retry(&fs->seq, seq));
719 static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link)
721 int ret;
723 if (IS_ERR(link))
724 goto fail;
726 if (*link == '/') {
727 set_root(nd);
728 path_put(&nd->path);
729 nd->path = nd->root;
730 path_get(&nd->root);
732 nd->inode = nd->path.dentry->d_inode;
734 ret = link_path_walk(link, nd);
735 return ret;
736 fail:
737 path_put(&nd->path);
738 return PTR_ERR(link);
741 static void path_put_conditional(struct path *path, struct nameidata *nd)
743 dput(path->dentry);
744 if (path->mnt != nd->path.mnt)
745 mntput(path->mnt);
748 static inline void path_to_nameidata(const struct path *path,
749 struct nameidata *nd)
751 if (!(nd->flags & LOOKUP_RCU)) {
752 dput(nd->path.dentry);
753 if (nd->path.mnt != path->mnt)
754 mntput(nd->path.mnt);
756 nd->path.mnt = path->mnt;
757 nd->path.dentry = path->dentry;
760 static __always_inline int
761 __do_follow_link(const struct path *link, struct nameidata *nd, void **p)
763 int error;
764 struct dentry *dentry = link->dentry;
766 BUG_ON(nd->flags & LOOKUP_RCU);
768 touch_atime(link->mnt, dentry);
769 nd_set_link(nd, NULL);
771 if (link->mnt == nd->path.mnt)
772 mntget(link->mnt);
774 nd->last_type = LAST_BIND;
775 *p = dentry->d_inode->i_op->follow_link(dentry, nd);
776 error = PTR_ERR(*p);
777 if (!IS_ERR(*p)) {
778 char *s = nd_get_link(nd);
779 error = 0;
780 if (s)
781 error = __vfs_follow_link(nd, s);
782 else if (nd->last_type == LAST_BIND) {
783 error = force_reval_path(&nd->path, nd);
784 if (error)
785 path_put(&nd->path);
788 return error;
792 * This limits recursive symlink follows to 8, while
793 * limiting consecutive symlinks to 40.
795 * Without that kind of total limit, nasty chains of consecutive
796 * symlinks can cause almost arbitrarily long lookups.
798 static inline int do_follow_link(struct path *path, struct nameidata *nd)
800 void *cookie;
801 int err = -ELOOP;
803 /* We drop rcu-walk here */
804 if (nameidata_dentry_drop_rcu_maybe(nd, path->dentry))
805 return -ECHILD;
807 if (current->link_count >= MAX_NESTED_LINKS)
808 goto loop;
809 if (current->total_link_count >= 40)
810 goto loop;
811 BUG_ON(nd->depth >= MAX_NESTED_LINKS);
812 cond_resched();
813 err = security_inode_follow_link(path->dentry, nd);
814 if (err)
815 goto loop;
816 current->link_count++;
817 current->total_link_count++;
818 nd->depth++;
819 err = __do_follow_link(path, nd, &cookie);
820 if (!IS_ERR(cookie) && path->dentry->d_inode->i_op->put_link)
821 path->dentry->d_inode->i_op->put_link(path->dentry, nd, cookie);
822 path_put(path);
823 current->link_count--;
824 nd->depth--;
825 return err;
826 loop:
827 path_put_conditional(path, nd);
828 path_put(&nd->path);
829 return err;
832 static int follow_up_rcu(struct path *path)
834 struct vfsmount *parent;
835 struct dentry *mountpoint;
837 parent = path->mnt->mnt_parent;
838 if (parent == path->mnt)
839 return 0;
840 mountpoint = path->mnt->mnt_mountpoint;
841 path->dentry = mountpoint;
842 path->mnt = parent;
843 return 1;
846 int follow_up(struct path *path)
848 struct vfsmount *parent;
849 struct dentry *mountpoint;
851 br_read_lock(vfsmount_lock);
852 parent = path->mnt->mnt_parent;
853 if (parent == path->mnt) {
854 br_read_unlock(vfsmount_lock);
855 return 0;
857 mntget(parent);
858 mountpoint = dget(path->mnt->mnt_mountpoint);
859 br_read_unlock(vfsmount_lock);
860 dput(path->dentry);
861 path->dentry = mountpoint;
862 mntput(path->mnt);
863 path->mnt = parent;
864 return 1;
868 * Perform an automount
869 * - return -EISDIR to tell follow_managed() to stop and return the path we
870 * were called with.
872 static int follow_automount(struct path *path, unsigned flags,
873 bool *need_mntput)
875 struct vfsmount *mnt;
876 int err;
878 if (!path->dentry->d_op || !path->dentry->d_op->d_automount)
879 return -EREMOTE;
881 /* We don't want to mount if someone supplied AT_NO_AUTOMOUNT
882 * and this is the terminal part of the path.
884 if ((flags & LOOKUP_NO_AUTOMOUNT) && !(flags & LOOKUP_CONTINUE))
885 return -EISDIR; /* we actually want to stop here */
887 /* We want to mount if someone is trying to open/create a file of any
888 * type under the mountpoint, wants to traverse through the mountpoint
889 * or wants to open the mounted directory.
891 * We don't want to mount if someone's just doing a stat and they've
892 * set AT_SYMLINK_NOFOLLOW - unless they're stat'ing a directory and
893 * appended a '/' to the name.
895 if (!(flags & LOOKUP_FOLLOW) &&
896 !(flags & (LOOKUP_CONTINUE | LOOKUP_DIRECTORY |
897 LOOKUP_OPEN | LOOKUP_CREATE)))
898 return -EISDIR;
900 current->total_link_count++;
901 if (current->total_link_count >= 40)
902 return -ELOOP;
904 mnt = path->dentry->d_op->d_automount(path);
905 if (IS_ERR(mnt)) {
907 * The filesystem is allowed to return -EISDIR here to indicate
908 * it doesn't want to automount. For instance, autofs would do
909 * this so that its userspace daemon can mount on this dentry.
911 * However, we can only permit this if it's a terminal point in
912 * the path being looked up; if it wasn't then the remainder of
913 * the path is inaccessible and we should say so.
915 if (PTR_ERR(mnt) == -EISDIR && (flags & LOOKUP_CONTINUE))
916 return -EREMOTE;
917 return PTR_ERR(mnt);
920 if (!mnt) /* mount collision */
921 return 0;
923 err = finish_automount(mnt, path);
925 switch (err) {
926 case -EBUSY:
927 /* Someone else made a mount here whilst we were busy */
928 return 0;
929 case 0:
930 dput(path->dentry);
931 if (*need_mntput)
932 mntput(path->mnt);
933 path->mnt = mnt;
934 path->dentry = dget(mnt->mnt_root);
935 *need_mntput = true;
936 return 0;
937 default:
938 return err;
944 * Handle a dentry that is managed in some way.
945 * - Flagged for transit management (autofs)
946 * - Flagged as mountpoint
947 * - Flagged as automount point
949 * This may only be called in refwalk mode.
951 * Serialization is taken care of in namespace.c
953 static int follow_managed(struct path *path, unsigned flags)
955 unsigned managed;
956 bool need_mntput = false;
957 int ret;
959 /* Given that we're not holding a lock here, we retain the value in a
960 * local variable for each dentry as we look at it so that we don't see
961 * the components of that value change under us */
962 while (managed = ACCESS_ONCE(path->dentry->d_flags),
963 managed &= DCACHE_MANAGED_DENTRY,
964 unlikely(managed != 0)) {
965 /* Allow the filesystem to manage the transit without i_mutex
966 * being held. */
967 if (managed & DCACHE_MANAGE_TRANSIT) {
968 BUG_ON(!path->dentry->d_op);
969 BUG_ON(!path->dentry->d_op->d_manage);
970 ret = path->dentry->d_op->d_manage(path->dentry,
971 false, false);
972 if (ret < 0)
973 return ret == -EISDIR ? 0 : ret;
976 /* Transit to a mounted filesystem. */
977 if (managed & DCACHE_MOUNTED) {
978 struct vfsmount *mounted = lookup_mnt(path);
979 if (mounted) {
980 dput(path->dentry);
981 if (need_mntput)
982 mntput(path->mnt);
983 path->mnt = mounted;
984 path->dentry = dget(mounted->mnt_root);
985 need_mntput = true;
986 continue;
989 /* Something is mounted on this dentry in another
990 * namespace and/or whatever was mounted there in this
991 * namespace got unmounted before we managed to get the
992 * vfsmount_lock */
995 /* Handle an automount point */
996 if (managed & DCACHE_NEED_AUTOMOUNT) {
997 ret = follow_automount(path, flags, &need_mntput);
998 if (ret < 0)
999 return ret == -EISDIR ? 0 : ret;
1000 continue;
1003 /* We didn't change the current path point */
1004 break;
1006 return 0;
1009 int follow_down_one(struct path *path)
1011 struct vfsmount *mounted;
1013 mounted = lookup_mnt(path);
1014 if (mounted) {
1015 dput(path->dentry);
1016 mntput(path->mnt);
1017 path->mnt = mounted;
1018 path->dentry = dget(mounted->mnt_root);
1019 return 1;
1021 return 0;
1025 * Skip to top of mountpoint pile in rcuwalk mode. We abort the rcu-walk if we
1026 * meet a managed dentry and we're not walking to "..". True is returned to
1027 * continue, false to abort.
1029 static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
1030 struct inode **inode, bool reverse_transit)
1032 while (d_mountpoint(path->dentry)) {
1033 struct vfsmount *mounted;
1034 if (unlikely(path->dentry->d_flags & DCACHE_MANAGE_TRANSIT) &&
1035 !reverse_transit &&
1036 path->dentry->d_op->d_manage(path->dentry, false, true) < 0)
1037 return false;
1038 mounted = __lookup_mnt(path->mnt, path->dentry, 1);
1039 if (!mounted)
1040 break;
1041 path->mnt = mounted;
1042 path->dentry = mounted->mnt_root;
1043 nd->seq = read_seqcount_begin(&path->dentry->d_seq);
1044 *inode = path->dentry->d_inode;
1047 if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
1048 return reverse_transit;
1049 return true;
1052 static int follow_dotdot_rcu(struct nameidata *nd)
1054 struct inode *inode = nd->inode;
1056 set_root_rcu(nd);
1058 while (1) {
1059 if (nd->path.dentry == nd->root.dentry &&
1060 nd->path.mnt == nd->root.mnt) {
1061 break;
1063 if (nd->path.dentry != nd->path.mnt->mnt_root) {
1064 struct dentry *old = nd->path.dentry;
1065 struct dentry *parent = old->d_parent;
1066 unsigned seq;
1068 seq = read_seqcount_begin(&parent->d_seq);
1069 if (read_seqcount_retry(&old->d_seq, nd->seq))
1070 return -ECHILD;
1071 inode = parent->d_inode;
1072 nd->path.dentry = parent;
1073 nd->seq = seq;
1074 break;
1076 if (!follow_up_rcu(&nd->path))
1077 break;
1078 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
1079 inode = nd->path.dentry->d_inode;
1081 __follow_mount_rcu(nd, &nd->path, &inode, true);
1082 nd->inode = inode;
1084 return 0;
1088 * Follow down to the covering mount currently visible to userspace. At each
1089 * point, the filesystem owning that dentry may be queried as to whether the
1090 * caller is permitted to proceed or not.
1092 * Care must be taken as namespace_sem may be held (indicated by mounting_here
1093 * being true).
1095 int follow_down(struct path *path, bool mounting_here)
1097 unsigned managed;
1098 int ret;
1100 while (managed = ACCESS_ONCE(path->dentry->d_flags),
1101 unlikely(managed & DCACHE_MANAGED_DENTRY)) {
1102 /* Allow the filesystem to manage the transit without i_mutex
1103 * being held.
1105 * We indicate to the filesystem if someone is trying to mount
1106 * something here. This gives autofs the chance to deny anyone
1107 * other than its daemon the right to mount on its
1108 * superstructure.
1110 * The filesystem may sleep at this point.
1112 if (managed & DCACHE_MANAGE_TRANSIT) {
1113 BUG_ON(!path->dentry->d_op);
1114 BUG_ON(!path->dentry->d_op->d_manage);
1115 ret = path->dentry->d_op->d_manage(
1116 path->dentry, mounting_here, false);
1117 if (ret < 0)
1118 return ret == -EISDIR ? 0 : ret;
1121 /* Transit to a mounted filesystem. */
1122 if (managed & DCACHE_MOUNTED) {
1123 struct vfsmount *mounted = lookup_mnt(path);
1124 if (!mounted)
1125 break;
1126 dput(path->dentry);
1127 mntput(path->mnt);
1128 path->mnt = mounted;
1129 path->dentry = dget(mounted->mnt_root);
1130 continue;
1133 /* Don't handle automount points here */
1134 break;
1136 return 0;
1140 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1142 static void follow_mount(struct path *path)
1144 while (d_mountpoint(path->dentry)) {
1145 struct vfsmount *mounted = lookup_mnt(path);
1146 if (!mounted)
1147 break;
1148 dput(path->dentry);
1149 mntput(path->mnt);
1150 path->mnt = mounted;
1151 path->dentry = dget(mounted->mnt_root);
1155 static void follow_dotdot(struct nameidata *nd)
1157 set_root(nd);
1159 while(1) {
1160 struct dentry *old = nd->path.dentry;
1162 if (nd->path.dentry == nd->root.dentry &&
1163 nd->path.mnt == nd->root.mnt) {
1164 break;
1166 if (nd->path.dentry != nd->path.mnt->mnt_root) {
1167 /* rare case of legitimate dget_parent()... */
1168 nd->path.dentry = dget_parent(nd->path.dentry);
1169 dput(old);
1170 break;
1172 if (!follow_up(&nd->path))
1173 break;
1175 follow_mount(&nd->path);
1176 nd->inode = nd->path.dentry->d_inode;
1180 * Allocate a dentry with name and parent, and perform a parent
1181 * directory ->lookup on it. Returns the new dentry, or ERR_PTR
1182 * on error. parent->d_inode->i_mutex must be held. d_lookup must
1183 * have verified that no child exists while under i_mutex.
1185 static struct dentry *d_alloc_and_lookup(struct dentry *parent,
1186 struct qstr *name, struct nameidata *nd)
1188 struct inode *inode = parent->d_inode;
1189 struct dentry *dentry;
1190 struct dentry *old;
1192 /* Don't create child dentry for a dead directory. */
1193 if (unlikely(IS_DEADDIR(inode)))
1194 return ERR_PTR(-ENOENT);
1196 dentry = d_alloc(parent, name);
1197 if (unlikely(!dentry))
1198 return ERR_PTR(-ENOMEM);
1200 old = inode->i_op->lookup(inode, dentry, nd);
1201 if (unlikely(old)) {
1202 dput(dentry);
1203 dentry = old;
1205 return dentry;
1209 * It's more convoluted than I'd like it to be, but... it's still fairly
1210 * small and for now I'd prefer to have fast path as straight as possible.
1211 * It _is_ time-critical.
1213 static int do_lookup(struct nameidata *nd, struct qstr *name,
1214 struct path *path, struct inode **inode)
1216 struct vfsmount *mnt = nd->path.mnt;
1217 struct dentry *dentry, *parent = nd->path.dentry;
1218 struct inode *dir;
1219 int err;
1222 * See if the low-level filesystem might want
1223 * to use its own hash..
1225 if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
1226 err = parent->d_op->d_hash(parent, nd->inode, name);
1227 if (err < 0)
1228 return err;
1232 * Rename seqlock is not required here because in the off chance
1233 * of a false negative due to a concurrent rename, we're going to
1234 * do the non-racy lookup, below.
1236 if (nd->flags & LOOKUP_RCU) {
1237 unsigned seq;
1239 *inode = nd->inode;
1240 dentry = __d_lookup_rcu(parent, name, &seq, inode);
1241 if (!dentry) {
1242 if (nameidata_drop_rcu(nd))
1243 return -ECHILD;
1244 goto need_lookup;
1246 /* Memory barrier in read_seqcount_begin of child is enough */
1247 if (__read_seqcount_retry(&parent->d_seq, nd->seq))
1248 return -ECHILD;
1250 nd->seq = seq;
1251 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
1252 dentry = do_revalidate_rcu(dentry, nd);
1253 if (!dentry)
1254 goto need_lookup;
1255 if (IS_ERR(dentry))
1256 goto fail;
1257 if (!(nd->flags & LOOKUP_RCU))
1258 goto done;
1260 path->mnt = mnt;
1261 path->dentry = dentry;
1262 if (likely(__follow_mount_rcu(nd, path, inode, false)))
1263 return 0;
1264 if (nameidata_drop_rcu(nd))
1265 return -ECHILD;
1266 /* fallthru */
1268 dentry = __d_lookup(parent, name);
1269 if (!dentry)
1270 goto need_lookup;
1271 found:
1272 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
1273 dentry = do_revalidate(dentry, nd);
1274 if (!dentry)
1275 goto need_lookup;
1276 if (IS_ERR(dentry))
1277 goto fail;
1279 done:
1280 path->mnt = mnt;
1281 path->dentry = dentry;
1282 err = follow_managed(path, nd->flags);
1283 if (unlikely(err < 0)) {
1284 path_put_conditional(path, nd);
1285 return err;
1287 *inode = path->dentry->d_inode;
1288 return 0;
1290 need_lookup:
1291 dir = parent->d_inode;
1292 BUG_ON(nd->inode != dir);
1294 mutex_lock(&dir->i_mutex);
1296 * First re-do the cached lookup just in case it was created
1297 * while we waited for the directory semaphore, or the first
1298 * lookup failed due to an unrelated rename.
1300 * This could use version numbering or similar to avoid unnecessary
1301 * cache lookups, but then we'd have to do the first lookup in the
1302 * non-racy way. However in the common case here, everything should
1303 * be hot in cache, so would it be a big win?
1305 dentry = d_lookup(parent, name);
1306 if (likely(!dentry)) {
1307 dentry = d_alloc_and_lookup(parent, name, nd);
1308 mutex_unlock(&dir->i_mutex);
1309 if (IS_ERR(dentry))
1310 goto fail;
1311 goto done;
1314 * Uhhuh! Nasty case: the cache was re-populated while
1315 * we waited on the semaphore. Need to revalidate.
1317 mutex_unlock(&dir->i_mutex);
1318 goto found;
1320 fail:
1321 return PTR_ERR(dentry);
1325 * Name resolution.
1326 * This is the basic name resolution function, turning a pathname into
1327 * the final dentry. We expect 'base' to be positive and a directory.
1329 * Returns 0 and nd will have valid dentry and mnt on success.
1330 * Returns error and drops reference to input namei data on failure.
1332 static int link_path_walk(const char *name, struct nameidata *nd)
1334 struct path next;
1335 int err;
1336 unsigned int lookup_flags = nd->flags;
1338 while (*name=='/')
1339 name++;
1340 if (!*name)
1341 goto return_reval;
1343 if (nd->depth)
1344 lookup_flags = LOOKUP_FOLLOW | (nd->flags & LOOKUP_CONTINUE);
1346 /* At this point we know we have a real path component. */
1347 for(;;) {
1348 struct inode *inode;
1349 unsigned long hash;
1350 struct qstr this;
1351 unsigned int c;
1353 nd->flags |= LOOKUP_CONTINUE;
1354 if (nd->flags & LOOKUP_RCU) {
1355 err = exec_permission(nd->inode, IPERM_FLAG_RCU);
1356 if (err == -ECHILD) {
1357 if (nameidata_drop_rcu(nd))
1358 return -ECHILD;
1359 goto exec_again;
1361 } else {
1362 exec_again:
1363 err = exec_permission(nd->inode, 0);
1365 if (err)
1366 break;
1368 this.name = name;
1369 c = *(const unsigned char *)name;
1371 hash = init_name_hash();
1372 do {
1373 name++;
1374 hash = partial_name_hash(c, hash);
1375 c = *(const unsigned char *)name;
1376 } while (c && (c != '/'));
1377 this.len = name - (const char *) this.name;
1378 this.hash = end_name_hash(hash);
1380 /* remove trailing slashes? */
1381 if (!c)
1382 goto last_component;
1383 while (*++name == '/');
1384 if (!*name)
1385 goto last_with_slashes;
1388 * "." and ".." are special - ".." especially so because it has
1389 * to be able to know about the current root directory and
1390 * parent relationships.
1392 if (this.name[0] == '.') switch (this.len) {
1393 default:
1394 break;
1395 case 2:
1396 if (this.name[1] != '.')
1397 break;
1398 if (nd->flags & LOOKUP_RCU) {
1399 if (follow_dotdot_rcu(nd))
1400 return -ECHILD;
1401 } else
1402 follow_dotdot(nd);
1403 /* fallthrough */
1404 case 1:
1405 continue;
1407 /* This does the actual lookups.. */
1408 err = do_lookup(nd, &this, &next, &inode);
1409 if (err)
1410 break;
1411 err = -ENOENT;
1412 if (!inode)
1413 goto out_dput;
1415 if (inode->i_op->follow_link) {
1416 BUG_ON(inode != next.dentry->d_inode);
1417 err = do_follow_link(&next, nd);
1418 if (err)
1419 goto return_err;
1420 nd->inode = nd->path.dentry->d_inode;
1421 err = -ENOENT;
1422 if (!nd->inode)
1423 break;
1424 } else {
1425 path_to_nameidata(&next, nd);
1426 nd->inode = inode;
1428 err = -ENOTDIR;
1429 if (!nd->inode->i_op->lookup)
1430 break;
1431 continue;
1432 /* here ends the main loop */
1434 last_with_slashes:
1435 lookup_flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
1436 last_component:
1437 /* Clear LOOKUP_CONTINUE iff it was previously unset */
1438 nd->flags &= lookup_flags | ~LOOKUP_CONTINUE;
1439 if (lookup_flags & LOOKUP_PARENT)
1440 goto lookup_parent;
1441 if (this.name[0] == '.') switch (this.len) {
1442 default:
1443 break;
1444 case 2:
1445 if (this.name[1] != '.')
1446 break;
1447 if (nd->flags & LOOKUP_RCU) {
1448 if (follow_dotdot_rcu(nd))
1449 return -ECHILD;
1450 } else
1451 follow_dotdot(nd);
1452 /* fallthrough */
1453 case 1:
1454 goto return_reval;
1456 err = do_lookup(nd, &this, &next, &inode);
1457 if (err)
1458 break;
1459 if (inode && unlikely(inode->i_op->follow_link) &&
1460 (lookup_flags & LOOKUP_FOLLOW)) {
1461 BUG_ON(inode != next.dentry->d_inode);
1462 err = do_follow_link(&next, nd);
1463 if (err)
1464 goto return_err;
1465 nd->inode = nd->path.dentry->d_inode;
1466 } else {
1467 path_to_nameidata(&next, nd);
1468 nd->inode = inode;
1470 err = -ENOENT;
1471 if (!nd->inode)
1472 break;
1473 if (lookup_flags & LOOKUP_DIRECTORY) {
1474 err = -ENOTDIR;
1475 if (!nd->inode->i_op->lookup)
1476 break;
1478 goto return_base;
1479 lookup_parent:
1480 nd->last = this;
1481 nd->last_type = LAST_NORM;
1482 if (this.name[0] != '.')
1483 goto return_base;
1484 if (this.len == 1)
1485 nd->last_type = LAST_DOT;
1486 else if (this.len == 2 && this.name[1] == '.')
1487 nd->last_type = LAST_DOTDOT;
1488 else
1489 goto return_base;
1490 return_reval:
1492 * We bypassed the ordinary revalidation routines.
1493 * We may need to check the cached dentry for staleness.
1495 if (need_reval_dot(nd->path.dentry)) {
1496 if (nameidata_drop_rcu_last_maybe(nd))
1497 return -ECHILD;
1498 /* Note: we do not d_invalidate() */
1499 err = d_revalidate(nd->path.dentry, nd);
1500 if (!err)
1501 err = -ESTALE;
1502 if (err < 0)
1503 break;
1504 return 0;
1506 return_base:
1507 if (nameidata_drop_rcu_last_maybe(nd))
1508 return -ECHILD;
1509 return 0;
1510 out_dput:
1511 if (!(nd->flags & LOOKUP_RCU))
1512 path_put_conditional(&next, nd);
1513 break;
1515 if (!(nd->flags & LOOKUP_RCU))
1516 path_put(&nd->path);
1517 return_err:
1518 return err;
1521 static inline int path_walk_rcu(const char *name, struct nameidata *nd)
1523 current->total_link_count = 0;
1525 return link_path_walk(name, nd);
1528 static inline int path_walk_simple(const char *name, struct nameidata *nd)
1530 current->total_link_count = 0;
1532 return link_path_walk(name, nd);
1535 static int path_walk(const char *name, struct nameidata *nd)
1537 struct path save = nd->path;
1538 int result;
1540 current->total_link_count = 0;
1542 /* make sure the stuff we saved doesn't go away */
1543 path_get(&save);
1545 result = link_path_walk(name, nd);
1546 if (result == -ESTALE) {
1547 /* nd->path had been dropped */
1548 current->total_link_count = 0;
1549 nd->path = save;
1550 path_get(&nd->path);
1551 nd->flags |= LOOKUP_REVAL;
1552 result = link_path_walk(name, nd);
1555 path_put(&save);
1557 return result;
1560 static void path_finish_rcu(struct nameidata *nd)
1562 if (nd->flags & LOOKUP_RCU) {
1563 /* RCU dangling. Cancel it. */
1564 nd->flags &= ~LOOKUP_RCU;
1565 nd->root.mnt = NULL;
1566 rcu_read_unlock();
1567 br_read_unlock(vfsmount_lock);
1569 if (nd->file)
1570 fput(nd->file);
1573 static int path_init_rcu(int dfd, const char *name, unsigned int flags, struct nameidata *nd)
1575 int retval = 0;
1576 int fput_needed;
1577 struct file *file;
1579 nd->last_type = LAST_ROOT; /* if there are only slashes... */
1580 nd->flags = flags | LOOKUP_RCU;
1581 nd->depth = 0;
1582 nd->root.mnt = NULL;
1583 nd->file = NULL;
1585 if (*name=='/') {
1586 struct fs_struct *fs = current->fs;
1587 unsigned seq;
1589 br_read_lock(vfsmount_lock);
1590 rcu_read_lock();
1592 do {
1593 seq = read_seqcount_begin(&fs->seq);
1594 nd->root = fs->root;
1595 nd->path = nd->root;
1596 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1597 } while (read_seqcount_retry(&fs->seq, seq));
1599 } else if (dfd == AT_FDCWD) {
1600 struct fs_struct *fs = current->fs;
1601 unsigned seq;
1603 br_read_lock(vfsmount_lock);
1604 rcu_read_lock();
1606 do {
1607 seq = read_seqcount_begin(&fs->seq);
1608 nd->path = fs->pwd;
1609 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1610 } while (read_seqcount_retry(&fs->seq, seq));
1612 } else {
1613 struct dentry *dentry;
1615 file = fget_light(dfd, &fput_needed);
1616 retval = -EBADF;
1617 if (!file)
1618 goto out_fail;
1620 dentry = file->f_path.dentry;
1622 retval = -ENOTDIR;
1623 if (!S_ISDIR(dentry->d_inode->i_mode))
1624 goto fput_fail;
1626 retval = file_permission(file, MAY_EXEC);
1627 if (retval)
1628 goto fput_fail;
1630 nd->path = file->f_path;
1631 if (fput_needed)
1632 nd->file = file;
1634 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1635 br_read_lock(vfsmount_lock);
1636 rcu_read_lock();
1638 nd->inode = nd->path.dentry->d_inode;
1639 return 0;
1641 fput_fail:
1642 fput_light(file, fput_needed);
1643 out_fail:
1644 return retval;
1647 static int path_init(int dfd, const char *name, unsigned int flags, struct nameidata *nd)
1649 int retval = 0;
1650 int fput_needed;
1651 struct file *file;
1653 nd->last_type = LAST_ROOT; /* if there are only slashes... */
1654 nd->flags = flags;
1655 nd->depth = 0;
1656 nd->root.mnt = NULL;
1658 if (*name=='/') {
1659 set_root(nd);
1660 nd->path = nd->root;
1661 path_get(&nd->root);
1662 } else if (dfd == AT_FDCWD) {
1663 get_fs_pwd(current->fs, &nd->path);
1664 } else {
1665 struct dentry *dentry;
1667 file = fget_light(dfd, &fput_needed);
1668 retval = -EBADF;
1669 if (!file)
1670 goto out_fail;
1672 dentry = file->f_path.dentry;
1674 retval = -ENOTDIR;
1675 if (!S_ISDIR(dentry->d_inode->i_mode))
1676 goto fput_fail;
1678 retval = file_permission(file, MAY_EXEC);
1679 if (retval)
1680 goto fput_fail;
1682 nd->path = file->f_path;
1683 path_get(&file->f_path);
1685 fput_light(file, fput_needed);
1687 nd->inode = nd->path.dentry->d_inode;
1688 return 0;
1690 fput_fail:
1691 fput_light(file, fput_needed);
1692 out_fail:
1693 return retval;
1696 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
1697 static int do_path_lookup(int dfd, const char *name,
1698 unsigned int flags, struct nameidata *nd)
1700 int retval;
1703 * Path walking is largely split up into 2 different synchronisation
1704 * schemes, rcu-walk and ref-walk (explained in
1705 * Documentation/filesystems/path-lookup.txt). These share much of the
1706 * path walk code, but some things particularly setup, cleanup, and
1707 * following mounts are sufficiently divergent that functions are
1708 * duplicated. Typically there is a function foo(), and its RCU
1709 * analogue, foo_rcu().
1711 * -ECHILD is the error number of choice (just to avoid clashes) that
1712 * is returned if some aspect of an rcu-walk fails. Such an error must
1713 * be handled by restarting a traditional ref-walk (which will always
1714 * be able to complete).
1716 retval = path_init_rcu(dfd, name, flags, nd);
1717 if (unlikely(retval))
1718 return retval;
1719 retval = path_walk_rcu(name, nd);
1720 path_finish_rcu(nd);
1721 if (nd->root.mnt) {
1722 path_put(&nd->root);
1723 nd->root.mnt = NULL;
1726 if (unlikely(retval == -ECHILD || retval == -ESTALE)) {
1727 /* slower, locked walk */
1728 if (retval == -ESTALE)
1729 flags |= LOOKUP_REVAL;
1730 retval = path_init(dfd, name, flags, nd);
1731 if (unlikely(retval))
1732 return retval;
1733 retval = path_walk(name, nd);
1734 if (nd->root.mnt) {
1735 path_put(&nd->root);
1736 nd->root.mnt = NULL;
1740 if (likely(!retval)) {
1741 if (unlikely(!audit_dummy_context())) {
1742 if (nd->path.dentry && nd->inode)
1743 audit_inode(name, nd->path.dentry);
1747 return retval;
1750 int path_lookup(const char *name, unsigned int flags,
1751 struct nameidata *nd)
1753 return do_path_lookup(AT_FDCWD, name, flags, nd);
1756 int kern_path(const char *name, unsigned int flags, struct path *path)
1758 struct nameidata nd;
1759 int res = do_path_lookup(AT_FDCWD, name, flags, &nd);
1760 if (!res)
1761 *path = nd.path;
1762 return res;
1766 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
1767 * @dentry: pointer to dentry of the base directory
1768 * @mnt: pointer to vfs mount of the base directory
1769 * @name: pointer to file name
1770 * @flags: lookup flags
1771 * @nd: pointer to nameidata
1773 int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
1774 const char *name, unsigned int flags,
1775 struct nameidata *nd)
1777 int retval;
1779 /* same as do_path_lookup */
1780 nd->last_type = LAST_ROOT;
1781 nd->flags = flags;
1782 nd->depth = 0;
1784 nd->path.dentry = dentry;
1785 nd->path.mnt = mnt;
1786 path_get(&nd->path);
1787 nd->root = nd->path;
1788 path_get(&nd->root);
1789 nd->inode = nd->path.dentry->d_inode;
1791 retval = path_walk(name, nd);
1792 if (unlikely(!retval && !audit_dummy_context() && nd->path.dentry &&
1793 nd->inode))
1794 audit_inode(name, nd->path.dentry);
1796 path_put(&nd->root);
1797 nd->root.mnt = NULL;
1799 return retval;
1802 static struct dentry *__lookup_hash(struct qstr *name,
1803 struct dentry *base, struct nameidata *nd)
1805 struct inode *inode = base->d_inode;
1806 struct dentry *dentry;
1807 int err;
1809 err = exec_permission(inode, 0);
1810 if (err)
1811 return ERR_PTR(err);
1814 * See if the low-level filesystem might want
1815 * to use its own hash..
1817 if (base->d_flags & DCACHE_OP_HASH) {
1818 err = base->d_op->d_hash(base, inode, name);
1819 dentry = ERR_PTR(err);
1820 if (err < 0)
1821 goto out;
1825 * Don't bother with __d_lookup: callers are for creat as
1826 * well as unlink, so a lot of the time it would cost
1827 * a double lookup.
1829 dentry = d_lookup(base, name);
1831 if (dentry && (dentry->d_flags & DCACHE_OP_REVALIDATE))
1832 dentry = do_revalidate(dentry, nd);
1834 if (!dentry)
1835 dentry = d_alloc_and_lookup(base, name, nd);
1836 out:
1837 return dentry;
1841 * Restricted form of lookup. Doesn't follow links, single-component only,
1842 * needs parent already locked. Doesn't follow mounts.
1843 * SMP-safe.
1845 static struct dentry *lookup_hash(struct nameidata *nd)
1847 return __lookup_hash(&nd->last, nd->path.dentry, nd);
1850 static int __lookup_one_len(const char *name, struct qstr *this,
1851 struct dentry *base, int len)
1853 unsigned long hash;
1854 unsigned int c;
1856 this->name = name;
1857 this->len = len;
1858 if (!len)
1859 return -EACCES;
1861 hash = init_name_hash();
1862 while (len--) {
1863 c = *(const unsigned char *)name++;
1864 if (c == '/' || c == '\0')
1865 return -EACCES;
1866 hash = partial_name_hash(c, hash);
1868 this->hash = end_name_hash(hash);
1869 return 0;
1873 * lookup_one_len - filesystem helper to lookup single pathname component
1874 * @name: pathname component to lookup
1875 * @base: base directory to lookup from
1876 * @len: maximum length @len should be interpreted to
1878 * Note that this routine is purely a helper for filesystem usage and should
1879 * not be called by generic code. Also note that by using this function the
1880 * nameidata argument is passed to the filesystem methods and a filesystem
1881 * using this helper needs to be prepared for that.
1883 struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
1885 int err;
1886 struct qstr this;
1888 WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));
1890 err = __lookup_one_len(name, &this, base, len);
1891 if (err)
1892 return ERR_PTR(err);
1894 return __lookup_hash(&this, base, NULL);
1897 int user_path_at(int dfd, const char __user *name, unsigned flags,
1898 struct path *path)
1900 struct nameidata nd;
1901 char *tmp = getname(name);
1902 int err = PTR_ERR(tmp);
1903 if (!IS_ERR(tmp)) {
1905 BUG_ON(flags & LOOKUP_PARENT);
1907 err = do_path_lookup(dfd, tmp, flags, &nd);
1908 putname(tmp);
1909 if (!err)
1910 *path = nd.path;
1912 return err;
1915 static int user_path_parent(int dfd, const char __user *path,
1916 struct nameidata *nd, char **name)
1918 char *s = getname(path);
1919 int error;
1921 if (IS_ERR(s))
1922 return PTR_ERR(s);
1924 error = do_path_lookup(dfd, s, LOOKUP_PARENT, nd);
1925 if (error)
1926 putname(s);
1927 else
1928 *name = s;
1930 return error;
1934 * It's inline, so penalty for filesystems that don't use sticky bit is
1935 * minimal.
1937 static inline int check_sticky(struct inode *dir, struct inode *inode)
1939 uid_t fsuid = current_fsuid();
1941 if (!(dir->i_mode & S_ISVTX))
1942 return 0;
1943 if (inode->i_uid == fsuid)
1944 return 0;
1945 if (dir->i_uid == fsuid)
1946 return 0;
1947 return !capable(CAP_FOWNER);
1951 * Check whether we can remove a link victim from directory dir, check
1952 * whether the type of victim is right.
1953 * 1. We can't do it if dir is read-only (done in permission())
1954 * 2. We should have write and exec permissions on dir
1955 * 3. We can't remove anything from append-only dir
1956 * 4. We can't do anything with immutable dir (done in permission())
1957 * 5. If the sticky bit on dir is set we should either
1958 * a. be owner of dir, or
1959 * b. be owner of victim, or
1960 * c. have CAP_FOWNER capability
1961 * 6. If the victim is append-only or immutable we can't do antyhing with
1962 * links pointing to it.
1963 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
1964 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
1965 * 9. We can't remove a root or mountpoint.
1966 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
1967 * nfs_async_unlink().
1969 static int may_delete(struct inode *dir,struct dentry *victim,int isdir)
1971 int error;
1973 if (!victim->d_inode)
1974 return -ENOENT;
1976 BUG_ON(victim->d_parent->d_inode != dir);
1977 audit_inode_child(victim, dir);
1979 error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
1980 if (error)
1981 return error;
1982 if (IS_APPEND(dir))
1983 return -EPERM;
1984 if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
1985 IS_IMMUTABLE(victim->d_inode) || IS_SWAPFILE(victim->d_inode))
1986 return -EPERM;
1987 if (isdir) {
1988 if (!S_ISDIR(victim->d_inode->i_mode))
1989 return -ENOTDIR;
1990 if (IS_ROOT(victim))
1991 return -EBUSY;
1992 } else if (S_ISDIR(victim->d_inode->i_mode))
1993 return -EISDIR;
1994 if (IS_DEADDIR(dir))
1995 return -ENOENT;
1996 if (victim->d_flags & DCACHE_NFSFS_RENAMED)
1997 return -EBUSY;
1998 return 0;
2001 /* Check whether we can create an object with dentry child in directory
2002 * dir.
2003 * 1. We can't do it if child already exists (open has special treatment for
2004 * this case, but since we are inlined it's OK)
2005 * 2. We can't do it if dir is read-only (done in permission())
2006 * 3. We should have write and exec permissions on dir
2007 * 4. We can't do it if dir is immutable (done in permission())
2009 static inline int may_create(struct inode *dir, struct dentry *child)
2011 if (child->d_inode)
2012 return -EEXIST;
2013 if (IS_DEADDIR(dir))
2014 return -ENOENT;
2015 return inode_permission(dir, MAY_WRITE | MAY_EXEC);
2019 * p1 and p2 should be directories on the same fs.
2021 struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
2023 struct dentry *p;
2025 if (p1 == p2) {
2026 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2027 return NULL;
2030 mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
2032 p = d_ancestor(p2, p1);
2033 if (p) {
2034 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
2035 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
2036 return p;
2039 p = d_ancestor(p1, p2);
2040 if (p) {
2041 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2042 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
2043 return p;
2046 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2047 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
2048 return NULL;
2051 void unlock_rename(struct dentry *p1, struct dentry *p2)
2053 mutex_unlock(&p1->d_inode->i_mutex);
2054 if (p1 != p2) {
2055 mutex_unlock(&p2->d_inode->i_mutex);
2056 mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
2060 int vfs_create(struct inode *dir, struct dentry *dentry, int mode,
2061 struct nameidata *nd)
2063 int error = may_create(dir, dentry);
2065 if (error)
2066 return error;
2068 if (!dir->i_op->create)
2069 return -EACCES; /* shouldn't it be ENOSYS? */
2070 mode &= S_IALLUGO;
2071 mode |= S_IFREG;
2072 error = security_inode_create(dir, dentry, mode);
2073 if (error)
2074 return error;
2075 error = dir->i_op->create(dir, dentry, mode, nd);
2076 if (!error)
2077 fsnotify_create(dir, dentry);
2078 return error;
2081 int may_open(struct path *path, int acc_mode, int flag)
2083 struct dentry *dentry = path->dentry;
2084 struct inode *inode = dentry->d_inode;
2085 int error;
2087 if (!inode)
2088 return -ENOENT;
2090 switch (inode->i_mode & S_IFMT) {
2091 case S_IFLNK:
2092 return -ELOOP;
2093 case S_IFDIR:
2094 if (acc_mode & MAY_WRITE)
2095 return -EISDIR;
2096 break;
2097 case S_IFBLK:
2098 case S_IFCHR:
2099 if (path->mnt->mnt_flags & MNT_NODEV)
2100 return -EACCES;
2101 /*FALLTHRU*/
2102 case S_IFIFO:
2103 case S_IFSOCK:
2104 flag &= ~O_TRUNC;
2105 break;
2108 error = inode_permission(inode, acc_mode);
2109 if (error)
2110 return error;
2113 * An append-only file must be opened in append mode for writing.
2115 if (IS_APPEND(inode)) {
2116 if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
2117 return -EPERM;
2118 if (flag & O_TRUNC)
2119 return -EPERM;
2122 /* O_NOATIME can only be set by the owner or superuser */
2123 if (flag & O_NOATIME && !is_owner_or_cap(inode))
2124 return -EPERM;
2127 * Ensure there are no outstanding leases on the file.
2129 return break_lease(inode, flag);
2132 static int handle_truncate(struct file *filp)
2134 struct path *path = &filp->f_path;
2135 struct inode *inode = path->dentry->d_inode;
2136 int error = get_write_access(inode);
2137 if (error)
2138 return error;
2140 * Refuse to truncate files with mandatory locks held on them.
2142 error = locks_verify_locked(inode);
2143 if (!error)
2144 error = security_path_truncate(path);
2145 if (!error) {
2146 error = do_truncate(path->dentry, 0,
2147 ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
2148 filp);
2150 put_write_access(inode);
2151 return error;
2155 * Be careful about ever adding any more callers of this
2156 * function. Its flags must be in the namei format, not
2157 * what get passed to sys_open().
2159 static int __open_namei_create(struct nameidata *nd, struct path *path,
2160 int open_flag, int mode)
2162 int error;
2163 struct dentry *dir = nd->path.dentry;
2165 if (!IS_POSIXACL(dir->d_inode))
2166 mode &= ~current_umask();
2167 error = security_path_mknod(&nd->path, path->dentry, mode, 0);
2168 if (error)
2169 goto out_unlock;
2170 error = vfs_create(dir->d_inode, path->dentry, mode, nd);
2171 out_unlock:
2172 mutex_unlock(&dir->d_inode->i_mutex);
2173 dput(nd->path.dentry);
2174 nd->path.dentry = path->dentry;
2176 if (error)
2177 return error;
2178 /* Don't check for write permission, don't truncate */
2179 return may_open(&nd->path, 0, open_flag & ~O_TRUNC);
2183 * Note that while the flag value (low two bits) for sys_open means:
2184 * 00 - read-only
2185 * 01 - write-only
2186 * 10 - read-write
2187 * 11 - special
2188 * it is changed into
2189 * 00 - no permissions needed
2190 * 01 - read-permission
2191 * 10 - write-permission
2192 * 11 - read-write
2193 * for the internal routines (ie open_namei()/follow_link() etc)
2194 * This is more logical, and also allows the 00 "no perm needed"
2195 * to be used for symlinks (where the permissions are checked
2196 * later).
2199 static inline int open_to_namei_flags(int flag)
2201 if ((flag+1) & O_ACCMODE)
2202 flag++;
2203 return flag;
2206 static int open_will_truncate(int flag, struct inode *inode)
2209 * We'll never write to the fs underlying
2210 * a device file.
2212 if (special_file(inode->i_mode))
2213 return 0;
2214 return (flag & O_TRUNC);
2217 static struct file *finish_open(struct nameidata *nd,
2218 int open_flag, int acc_mode)
2220 struct file *filp;
2221 int will_truncate;
2222 int error;
2224 will_truncate = open_will_truncate(open_flag, nd->path.dentry->d_inode);
2225 if (will_truncate) {
2226 error = mnt_want_write(nd->path.mnt);
2227 if (error)
2228 goto exit;
2230 error = may_open(&nd->path, acc_mode, open_flag);
2231 if (error) {
2232 if (will_truncate)
2233 mnt_drop_write(nd->path.mnt);
2234 goto exit;
2236 filp = nameidata_to_filp(nd);
2237 if (!IS_ERR(filp)) {
2238 error = ima_file_check(filp, acc_mode);
2239 if (error) {
2240 fput(filp);
2241 filp = ERR_PTR(error);
2244 if (!IS_ERR(filp)) {
2245 if (will_truncate) {
2246 error = handle_truncate(filp);
2247 if (error) {
2248 fput(filp);
2249 filp = ERR_PTR(error);
2254 * It is now safe to drop the mnt write
2255 * because the filp has had a write taken
2256 * on its behalf.
2258 if (will_truncate)
2259 mnt_drop_write(nd->path.mnt);
2260 path_put(&nd->path);
2261 return filp;
2263 exit:
2264 path_put(&nd->path);
2265 return ERR_PTR(error);
2269 * Handle O_CREAT case for do_filp_open
2271 static struct file *do_last(struct nameidata *nd, struct path *path,
2272 int open_flag, int acc_mode,
2273 int mode, const char *pathname)
2275 struct dentry *dir = nd->path.dentry;
2276 struct file *filp;
2277 int error = -EISDIR;
2279 switch (nd->last_type) {
2280 case LAST_DOTDOT:
2281 follow_dotdot(nd);
2282 dir = nd->path.dentry;
2283 case LAST_DOT:
2284 if (need_reval_dot(dir)) {
2285 int status = d_revalidate(nd->path.dentry, nd);
2286 if (!status)
2287 status = -ESTALE;
2288 if (status < 0) {
2289 error = status;
2290 goto exit;
2293 /* fallthrough */
2294 case LAST_ROOT:
2295 goto exit;
2296 case LAST_BIND:
2297 audit_inode(pathname, dir);
2298 goto ok;
2301 /* trailing slashes? */
2302 if (nd->last.name[nd->last.len])
2303 goto exit;
2305 mutex_lock(&dir->d_inode->i_mutex);
2307 path->dentry = lookup_hash(nd);
2308 path->mnt = nd->path.mnt;
2310 error = PTR_ERR(path->dentry);
2311 if (IS_ERR(path->dentry)) {
2312 mutex_unlock(&dir->d_inode->i_mutex);
2313 goto exit;
2316 if (IS_ERR(nd->intent.open.file)) {
2317 error = PTR_ERR(nd->intent.open.file);
2318 goto exit_mutex_unlock;
2321 /* Negative dentry, just create the file */
2322 if (!path->dentry->d_inode) {
2324 * This write is needed to ensure that a
2325 * ro->rw transition does not occur between
2326 * the time when the file is created and when
2327 * a permanent write count is taken through
2328 * the 'struct file' in nameidata_to_filp().
2330 error = mnt_want_write(nd->path.mnt);
2331 if (error)
2332 goto exit_mutex_unlock;
2333 error = __open_namei_create(nd, path, open_flag, mode);
2334 if (error) {
2335 mnt_drop_write(nd->path.mnt);
2336 goto exit;
2338 filp = nameidata_to_filp(nd);
2339 mnt_drop_write(nd->path.mnt);
2340 path_put(&nd->path);
2341 if (!IS_ERR(filp)) {
2342 error = ima_file_check(filp, acc_mode);
2343 if (error) {
2344 fput(filp);
2345 filp = ERR_PTR(error);
2348 return filp;
2352 * It already exists.
2354 mutex_unlock(&dir->d_inode->i_mutex);
2355 audit_inode(pathname, path->dentry);
2357 error = -EEXIST;
2358 if (open_flag & O_EXCL)
2359 goto exit_dput;
2361 error = follow_managed(path, nd->flags);
2362 if (error < 0)
2363 goto exit_dput;
2365 error = -ENOENT;
2366 if (!path->dentry->d_inode)
2367 goto exit_dput;
2369 if (path->dentry->d_inode->i_op->follow_link)
2370 return NULL;
2372 path_to_nameidata(path, nd);
2373 nd->inode = path->dentry->d_inode;
2374 error = -EISDIR;
2375 if (S_ISDIR(nd->inode->i_mode))
2376 goto exit;
2378 filp = finish_open(nd, open_flag, acc_mode);
2379 return filp;
2381 exit_mutex_unlock:
2382 mutex_unlock(&dir->d_inode->i_mutex);
2383 exit_dput:
2384 path_put_conditional(path, nd);
2385 exit:
2386 path_put(&nd->path);
2387 return ERR_PTR(error);
2391 * Note that the low bits of the passed in "open_flag"
2392 * are not the same as in the local variable "flag". See
2393 * open_to_namei_flags() for more details.
2395 struct file *do_filp_open(int dfd, const char *pathname,
2396 int open_flag, int mode, int acc_mode)
2398 struct file *filp;
2399 struct nameidata nd;
2400 int error;
2401 struct path path;
2402 int count = 0;
2403 int flag = open_to_namei_flags(open_flag);
2404 int flags;
2406 if (!(open_flag & O_CREAT))
2407 mode = 0;
2409 /* Must never be set by userspace */
2410 open_flag &= ~FMODE_NONOTIFY;
2413 * O_SYNC is implemented as __O_SYNC|O_DSYNC. As many places only
2414 * check for O_DSYNC if the need any syncing at all we enforce it's
2415 * always set instead of having to deal with possibly weird behaviour
2416 * for malicious applications setting only __O_SYNC.
2418 if (open_flag & __O_SYNC)
2419 open_flag |= O_DSYNC;
2421 if (!acc_mode)
2422 acc_mode = MAY_OPEN | ACC_MODE(open_flag);
2424 /* O_TRUNC implies we need access checks for write permissions */
2425 if (open_flag & O_TRUNC)
2426 acc_mode |= MAY_WRITE;
2428 /* Allow the LSM permission hook to distinguish append
2429 access from general write access. */
2430 if (open_flag & O_APPEND)
2431 acc_mode |= MAY_APPEND;
2433 flags = LOOKUP_OPEN;
2434 if (open_flag & O_CREAT) {
2435 flags |= LOOKUP_CREATE;
2436 if (open_flag & O_EXCL)
2437 flags |= LOOKUP_EXCL;
2439 if (open_flag & O_DIRECTORY)
2440 flags |= LOOKUP_DIRECTORY;
2441 if (!(open_flag & O_NOFOLLOW))
2442 flags |= LOOKUP_FOLLOW;
2444 filp = get_empty_filp();
2445 if (!filp)
2446 return ERR_PTR(-ENFILE);
2448 filp->f_flags = open_flag;
2449 nd.intent.open.file = filp;
2450 nd.intent.open.flags = flag;
2451 nd.intent.open.create_mode = mode;
2453 if (open_flag & O_CREAT)
2454 goto creat;
2456 /* !O_CREAT, simple open */
2457 error = do_path_lookup(dfd, pathname, flags, &nd);
2458 if (unlikely(error))
2459 goto out_filp;
2460 error = -ELOOP;
2461 if (!(nd.flags & LOOKUP_FOLLOW)) {
2462 if (nd.inode->i_op->follow_link)
2463 goto out_path;
2465 error = -ENOTDIR;
2466 if (nd.flags & LOOKUP_DIRECTORY) {
2467 if (!nd.inode->i_op->lookup)
2468 goto out_path;
2470 audit_inode(pathname, nd.path.dentry);
2471 filp = finish_open(&nd, open_flag, acc_mode);
2472 release_open_intent(&nd);
2473 return filp;
2475 creat:
2476 /* OK, have to create the file. Find the parent. */
2477 error = path_init_rcu(dfd, pathname,
2478 LOOKUP_PARENT | (flags & LOOKUP_REVAL), &nd);
2479 if (error)
2480 goto out_filp;
2481 error = path_walk_rcu(pathname, &nd);
2482 path_finish_rcu(&nd);
2483 if (unlikely(error == -ECHILD || error == -ESTALE)) {
2484 /* slower, locked walk */
2485 if (error == -ESTALE) {
2486 reval:
2487 flags |= LOOKUP_REVAL;
2489 error = path_init(dfd, pathname,
2490 LOOKUP_PARENT | (flags & LOOKUP_REVAL), &nd);
2491 if (error)
2492 goto out_filp;
2494 error = path_walk_simple(pathname, &nd);
2496 if (unlikely(error))
2497 goto out_filp;
2498 if (unlikely(!audit_dummy_context()))
2499 audit_inode(pathname, nd.path.dentry);
2502 * We have the parent and last component.
2504 nd.flags = flags;
2505 filp = do_last(&nd, &path, open_flag, acc_mode, mode, pathname);
2506 while (unlikely(!filp)) { /* trailing symlink */
2507 struct path link = path;
2508 struct inode *linki = link.dentry->d_inode;
2509 void *cookie;
2510 error = -ELOOP;
2511 if (!(nd.flags & LOOKUP_FOLLOW))
2512 goto exit_dput;
2513 if (count++ == 32)
2514 goto exit_dput;
2516 * This is subtle. Instead of calling do_follow_link() we do
2517 * the thing by hands. The reason is that this way we have zero
2518 * link_count and path_walk() (called from ->follow_link)
2519 * honoring LOOKUP_PARENT. After that we have the parent and
2520 * last component, i.e. we are in the same situation as after
2521 * the first path_walk(). Well, almost - if the last component
2522 * is normal we get its copy stored in nd->last.name and we will
2523 * have to putname() it when we are done. Procfs-like symlinks
2524 * just set LAST_BIND.
2526 nd.flags |= LOOKUP_PARENT;
2527 error = security_inode_follow_link(link.dentry, &nd);
2528 if (error)
2529 goto exit_dput;
2530 error = __do_follow_link(&link, &nd, &cookie);
2531 if (unlikely(error)) {
2532 if (!IS_ERR(cookie) && linki->i_op->put_link)
2533 linki->i_op->put_link(link.dentry, &nd, cookie);
2534 /* nd.path had been dropped */
2535 nd.path = link;
2536 goto out_path;
2538 nd.flags &= ~LOOKUP_PARENT;
2539 filp = do_last(&nd, &path, open_flag, acc_mode, mode, pathname);
2540 if (linki->i_op->put_link)
2541 linki->i_op->put_link(link.dentry, &nd, cookie);
2542 path_put(&link);
2544 out:
2545 if (nd.root.mnt)
2546 path_put(&nd.root);
2547 if (filp == ERR_PTR(-ESTALE) && !(flags & LOOKUP_REVAL))
2548 goto reval;
2549 release_open_intent(&nd);
2550 return filp;
2552 exit_dput:
2553 path_put_conditional(&path, &nd);
2554 out_path:
2555 path_put(&nd.path);
2556 out_filp:
2557 filp = ERR_PTR(error);
2558 goto out;
2562 * filp_open - open file and return file pointer
2564 * @filename: path to open
2565 * @flags: open flags as per the open(2) second argument
2566 * @mode: mode for the new file if O_CREAT is set, else ignored
2568 * This is the helper to open a file from kernelspace if you really
2569 * have to. But in generally you should not do this, so please move
2570 * along, nothing to see here..
2572 struct file *filp_open(const char *filename, int flags, int mode)
2574 return do_filp_open(AT_FDCWD, filename, flags, mode, 0);
2576 EXPORT_SYMBOL(filp_open);
2579 * lookup_create - lookup a dentry, creating it if it doesn't exist
2580 * @nd: nameidata info
2581 * @is_dir: directory flag
2583 * Simple function to lookup and return a dentry and create it
2584 * if it doesn't exist. Is SMP-safe.
2586 * Returns with nd->path.dentry->d_inode->i_mutex locked.
2588 struct dentry *lookup_create(struct nameidata *nd, int is_dir)
2590 struct dentry *dentry = ERR_PTR(-EEXIST);
2592 mutex_lock_nested(&nd->path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2594 * Yucky last component or no last component at all?
2595 * (foo/., foo/.., /////)
2597 if (nd->last_type != LAST_NORM)
2598 goto fail;
2599 nd->flags &= ~LOOKUP_PARENT;
2600 nd->flags |= LOOKUP_CREATE | LOOKUP_EXCL;
2601 nd->intent.open.flags = O_EXCL;
2604 * Do the final lookup.
2606 dentry = lookup_hash(nd);
2607 if (IS_ERR(dentry))
2608 goto fail;
2610 if (dentry->d_inode)
2611 goto eexist;
2613 * Special case - lookup gave negative, but... we had foo/bar/
2614 * From the vfs_mknod() POV we just have a negative dentry -
2615 * all is fine. Let's be bastards - you had / on the end, you've
2616 * been asking for (non-existent) directory. -ENOENT for you.
2618 if (unlikely(!is_dir && nd->last.name[nd->last.len])) {
2619 dput(dentry);
2620 dentry = ERR_PTR(-ENOENT);
2622 return dentry;
2623 eexist:
2624 dput(dentry);
2625 dentry = ERR_PTR(-EEXIST);
2626 fail:
2627 return dentry;
2629 EXPORT_SYMBOL_GPL(lookup_create);
2631 int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
2633 int error = may_create(dir, dentry);
2635 if (error)
2636 return error;
2638 if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
2639 return -EPERM;
2641 if (!dir->i_op->mknod)
2642 return -EPERM;
2644 error = devcgroup_inode_mknod(mode, dev);
2645 if (error)
2646 return error;
2648 error = security_inode_mknod(dir, dentry, mode, dev);
2649 if (error)
2650 return error;
2652 error = dir->i_op->mknod(dir, dentry, mode, dev);
2653 if (!error)
2654 fsnotify_create(dir, dentry);
2655 return error;
2658 static int may_mknod(mode_t mode)
2660 switch (mode & S_IFMT) {
2661 case S_IFREG:
2662 case S_IFCHR:
2663 case S_IFBLK:
2664 case S_IFIFO:
2665 case S_IFSOCK:
2666 case 0: /* zero mode translates to S_IFREG */
2667 return 0;
2668 case S_IFDIR:
2669 return -EPERM;
2670 default:
2671 return -EINVAL;
2675 SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, int, mode,
2676 unsigned, dev)
2678 int error;
2679 char *tmp;
2680 struct dentry *dentry;
2681 struct nameidata nd;
2683 if (S_ISDIR(mode))
2684 return -EPERM;
2686 error = user_path_parent(dfd, filename, &nd, &tmp);
2687 if (error)
2688 return error;
2690 dentry = lookup_create(&nd, 0);
2691 if (IS_ERR(dentry)) {
2692 error = PTR_ERR(dentry);
2693 goto out_unlock;
2695 if (!IS_POSIXACL(nd.path.dentry->d_inode))
2696 mode &= ~current_umask();
2697 error = may_mknod(mode);
2698 if (error)
2699 goto out_dput;
2700 error = mnt_want_write(nd.path.mnt);
2701 if (error)
2702 goto out_dput;
2703 error = security_path_mknod(&nd.path, dentry, mode, dev);
2704 if (error)
2705 goto out_drop_write;
2706 switch (mode & S_IFMT) {
2707 case 0: case S_IFREG:
2708 error = vfs_create(nd.path.dentry->d_inode,dentry,mode,&nd);
2709 break;
2710 case S_IFCHR: case S_IFBLK:
2711 error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,
2712 new_decode_dev(dev));
2713 break;
2714 case S_IFIFO: case S_IFSOCK:
2715 error = vfs_mknod(nd.path.dentry->d_inode,dentry,mode,0);
2716 break;
2718 out_drop_write:
2719 mnt_drop_write(nd.path.mnt);
2720 out_dput:
2721 dput(dentry);
2722 out_unlock:
2723 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2724 path_put(&nd.path);
2725 putname(tmp);
2727 return error;
2730 SYSCALL_DEFINE3(mknod, const char __user *, filename, int, mode, unsigned, dev)
2732 return sys_mknodat(AT_FDCWD, filename, mode, dev);
2735 int vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
2737 int error = may_create(dir, dentry);
2739 if (error)
2740 return error;
2742 if (!dir->i_op->mkdir)
2743 return -EPERM;
2745 mode &= (S_IRWXUGO|S_ISVTX);
2746 error = security_inode_mkdir(dir, dentry, mode);
2747 if (error)
2748 return error;
2750 error = dir->i_op->mkdir(dir, dentry, mode);
2751 if (!error)
2752 fsnotify_mkdir(dir, dentry);
2753 return error;
2756 SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, int, mode)
2758 int error = 0;
2759 char * tmp;
2760 struct dentry *dentry;
2761 struct nameidata nd;
2763 error = user_path_parent(dfd, pathname, &nd, &tmp);
2764 if (error)
2765 goto out_err;
2767 dentry = lookup_create(&nd, 1);
2768 error = PTR_ERR(dentry);
2769 if (IS_ERR(dentry))
2770 goto out_unlock;
2772 if (!IS_POSIXACL(nd.path.dentry->d_inode))
2773 mode &= ~current_umask();
2774 error = mnt_want_write(nd.path.mnt);
2775 if (error)
2776 goto out_dput;
2777 error = security_path_mkdir(&nd.path, dentry, mode);
2778 if (error)
2779 goto out_drop_write;
2780 error = vfs_mkdir(nd.path.dentry->d_inode, dentry, mode);
2781 out_drop_write:
2782 mnt_drop_write(nd.path.mnt);
2783 out_dput:
2784 dput(dentry);
2785 out_unlock:
2786 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2787 path_put(&nd.path);
2788 putname(tmp);
2789 out_err:
2790 return error;
2793 SYSCALL_DEFINE2(mkdir, const char __user *, pathname, int, mode)
2795 return sys_mkdirat(AT_FDCWD, pathname, mode);
2799 * We try to drop the dentry early: we should have
2800 * a usage count of 2 if we're the only user of this
2801 * dentry, and if that is true (possibly after pruning
2802 * the dcache), then we drop the dentry now.
2804 * A low-level filesystem can, if it choses, legally
2805 * do a
2807 * if (!d_unhashed(dentry))
2808 * return -EBUSY;
2810 * if it cannot handle the case of removing a directory
2811 * that is still in use by something else..
2813 void dentry_unhash(struct dentry *dentry)
2815 dget(dentry);
2816 shrink_dcache_parent(dentry);
2817 spin_lock(&dentry->d_lock);
2818 if (dentry->d_count == 2)
2819 __d_drop(dentry);
2820 spin_unlock(&dentry->d_lock);
2823 int vfs_rmdir(struct inode *dir, struct dentry *dentry)
2825 int error = may_delete(dir, dentry, 1);
2827 if (error)
2828 return error;
2830 if (!dir->i_op->rmdir)
2831 return -EPERM;
2833 mutex_lock(&dentry->d_inode->i_mutex);
2834 dentry_unhash(dentry);
2835 if (d_mountpoint(dentry))
2836 error = -EBUSY;
2837 else {
2838 error = security_inode_rmdir(dir, dentry);
2839 if (!error) {
2840 error = dir->i_op->rmdir(dir, dentry);
2841 if (!error) {
2842 dentry->d_inode->i_flags |= S_DEAD;
2843 dont_mount(dentry);
2847 mutex_unlock(&dentry->d_inode->i_mutex);
2848 if (!error) {
2849 d_delete(dentry);
2851 dput(dentry);
2853 return error;
2856 static long do_rmdir(int dfd, const char __user *pathname)
2858 int error = 0;
2859 char * name;
2860 struct dentry *dentry;
2861 struct nameidata nd;
2863 error = user_path_parent(dfd, pathname, &nd, &name);
2864 if (error)
2865 return error;
2867 switch(nd.last_type) {
2868 case LAST_DOTDOT:
2869 error = -ENOTEMPTY;
2870 goto exit1;
2871 case LAST_DOT:
2872 error = -EINVAL;
2873 goto exit1;
2874 case LAST_ROOT:
2875 error = -EBUSY;
2876 goto exit1;
2879 nd.flags &= ~LOOKUP_PARENT;
2881 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2882 dentry = lookup_hash(&nd);
2883 error = PTR_ERR(dentry);
2884 if (IS_ERR(dentry))
2885 goto exit2;
2886 error = mnt_want_write(nd.path.mnt);
2887 if (error)
2888 goto exit3;
2889 error = security_path_rmdir(&nd.path, dentry);
2890 if (error)
2891 goto exit4;
2892 error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
2893 exit4:
2894 mnt_drop_write(nd.path.mnt);
2895 exit3:
2896 dput(dentry);
2897 exit2:
2898 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2899 exit1:
2900 path_put(&nd.path);
2901 putname(name);
2902 return error;
2905 SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
2907 return do_rmdir(AT_FDCWD, pathname);
2910 int vfs_unlink(struct inode *dir, struct dentry *dentry)
2912 int error = may_delete(dir, dentry, 0);
2914 if (error)
2915 return error;
2917 if (!dir->i_op->unlink)
2918 return -EPERM;
2920 mutex_lock(&dentry->d_inode->i_mutex);
2921 if (d_mountpoint(dentry))
2922 error = -EBUSY;
2923 else {
2924 error = security_inode_unlink(dir, dentry);
2925 if (!error) {
2926 error = dir->i_op->unlink(dir, dentry);
2927 if (!error)
2928 dont_mount(dentry);
2931 mutex_unlock(&dentry->d_inode->i_mutex);
2933 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
2934 if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
2935 fsnotify_link_count(dentry->d_inode);
2936 d_delete(dentry);
2939 return error;
2943 * Make sure that the actual truncation of the file will occur outside its
2944 * directory's i_mutex. Truncate can take a long time if there is a lot of
2945 * writeout happening, and we don't want to prevent access to the directory
2946 * while waiting on the I/O.
2948 static long do_unlinkat(int dfd, const char __user *pathname)
2950 int error;
2951 char *name;
2952 struct dentry *dentry;
2953 struct nameidata nd;
2954 struct inode *inode = NULL;
2956 error = user_path_parent(dfd, pathname, &nd, &name);
2957 if (error)
2958 return error;
2960 error = -EISDIR;
2961 if (nd.last_type != LAST_NORM)
2962 goto exit1;
2964 nd.flags &= ~LOOKUP_PARENT;
2966 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2967 dentry = lookup_hash(&nd);
2968 error = PTR_ERR(dentry);
2969 if (!IS_ERR(dentry)) {
2970 /* Why not before? Because we want correct error value */
2971 if (nd.last.name[nd.last.len])
2972 goto slashes;
2973 inode = dentry->d_inode;
2974 if (inode)
2975 ihold(inode);
2976 error = mnt_want_write(nd.path.mnt);
2977 if (error)
2978 goto exit2;
2979 error = security_path_unlink(&nd.path, dentry);
2980 if (error)
2981 goto exit3;
2982 error = vfs_unlink(nd.path.dentry->d_inode, dentry);
2983 exit3:
2984 mnt_drop_write(nd.path.mnt);
2985 exit2:
2986 dput(dentry);
2988 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2989 if (inode)
2990 iput(inode); /* truncate the inode here */
2991 exit1:
2992 path_put(&nd.path);
2993 putname(name);
2994 return error;
2996 slashes:
2997 error = !dentry->d_inode ? -ENOENT :
2998 S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
2999 goto exit2;
3002 SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
3004 if ((flag & ~AT_REMOVEDIR) != 0)
3005 return -EINVAL;
3007 if (flag & AT_REMOVEDIR)
3008 return do_rmdir(dfd, pathname);
3010 return do_unlinkat(dfd, pathname);
3013 SYSCALL_DEFINE1(unlink, const char __user *, pathname)
3015 return do_unlinkat(AT_FDCWD, pathname);
3018 int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
3020 int error = may_create(dir, dentry);
3022 if (error)
3023 return error;
3025 if (!dir->i_op->symlink)
3026 return -EPERM;
3028 error = security_inode_symlink(dir, dentry, oldname);
3029 if (error)
3030 return error;
3032 error = dir->i_op->symlink(dir, dentry, oldname);
3033 if (!error)
3034 fsnotify_create(dir, dentry);
3035 return error;
3038 SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
3039 int, newdfd, const char __user *, newname)
3041 int error;
3042 char *from;
3043 char *to;
3044 struct dentry *dentry;
3045 struct nameidata nd;
3047 from = getname(oldname);
3048 if (IS_ERR(from))
3049 return PTR_ERR(from);
3051 error = user_path_parent(newdfd, newname, &nd, &to);
3052 if (error)
3053 goto out_putname;
3055 dentry = lookup_create(&nd, 0);
3056 error = PTR_ERR(dentry);
3057 if (IS_ERR(dentry))
3058 goto out_unlock;
3060 error = mnt_want_write(nd.path.mnt);
3061 if (error)
3062 goto out_dput;
3063 error = security_path_symlink(&nd.path, dentry, from);
3064 if (error)
3065 goto out_drop_write;
3066 error = vfs_symlink(nd.path.dentry->d_inode, dentry, from);
3067 out_drop_write:
3068 mnt_drop_write(nd.path.mnt);
3069 out_dput:
3070 dput(dentry);
3071 out_unlock:
3072 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
3073 path_put(&nd.path);
3074 putname(to);
3075 out_putname:
3076 putname(from);
3077 return error;
3080 SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
3082 return sys_symlinkat(oldname, AT_FDCWD, newname);
3085 int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry)
3087 struct inode *inode = old_dentry->d_inode;
3088 int error;
3090 if (!inode)
3091 return -ENOENT;
3093 error = may_create(dir, new_dentry);
3094 if (error)
3095 return error;
3097 if (dir->i_sb != inode->i_sb)
3098 return -EXDEV;
3101 * A link to an append-only or immutable file cannot be created.
3103 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
3104 return -EPERM;
3105 if (!dir->i_op->link)
3106 return -EPERM;
3107 if (S_ISDIR(inode->i_mode))
3108 return -EPERM;
3110 error = security_inode_link(old_dentry, dir, new_dentry);
3111 if (error)
3112 return error;
3114 mutex_lock(&inode->i_mutex);
3115 error = dir->i_op->link(old_dentry, dir, new_dentry);
3116 mutex_unlock(&inode->i_mutex);
3117 if (!error)
3118 fsnotify_link(dir, inode, new_dentry);
3119 return error;
3123 * Hardlinks are often used in delicate situations. We avoid
3124 * security-related surprises by not following symlinks on the
3125 * newname. --KAB
3127 * We don't follow them on the oldname either to be compatible
3128 * with linux 2.0, and to avoid hard-linking to directories
3129 * and other special files. --ADM
3131 SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
3132 int, newdfd, const char __user *, newname, int, flags)
3134 struct dentry *new_dentry;
3135 struct nameidata nd;
3136 struct path old_path;
3137 int error;
3138 char *to;
3140 if ((flags & ~AT_SYMLINK_FOLLOW) != 0)
3141 return -EINVAL;
3143 error = user_path_at(olddfd, oldname,
3144 flags & AT_SYMLINK_FOLLOW ? LOOKUP_FOLLOW : 0,
3145 &old_path);
3146 if (error)
3147 return error;
3149 error = user_path_parent(newdfd, newname, &nd, &to);
3150 if (error)
3151 goto out;
3152 error = -EXDEV;
3153 if (old_path.mnt != nd.path.mnt)
3154 goto out_release;
3155 new_dentry = lookup_create(&nd, 0);
3156 error = PTR_ERR(new_dentry);
3157 if (IS_ERR(new_dentry))
3158 goto out_unlock;
3159 error = mnt_want_write(nd.path.mnt);
3160 if (error)
3161 goto out_dput;
3162 error = security_path_link(old_path.dentry, &nd.path, new_dentry);
3163 if (error)
3164 goto out_drop_write;
3165 error = vfs_link(old_path.dentry, nd.path.dentry->d_inode, new_dentry);
3166 out_drop_write:
3167 mnt_drop_write(nd.path.mnt);
3168 out_dput:
3169 dput(new_dentry);
3170 out_unlock:
3171 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
3172 out_release:
3173 path_put(&nd.path);
3174 putname(to);
3175 out:
3176 path_put(&old_path);
3178 return error;
3181 SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
3183 return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
3187 * The worst of all namespace operations - renaming directory. "Perverted"
3188 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
3189 * Problems:
3190 * a) we can get into loop creation. Check is done in is_subdir().
3191 * b) race potential - two innocent renames can create a loop together.
3192 * That's where 4.4 screws up. Current fix: serialization on
3193 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
3194 * story.
3195 * c) we have to lock _three_ objects - parents and victim (if it exists).
3196 * And that - after we got ->i_mutex on parents (until then we don't know
3197 * whether the target exists). Solution: try to be smart with locking
3198 * order for inodes. We rely on the fact that tree topology may change
3199 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
3200 * move will be locked. Thus we can rank directories by the tree
3201 * (ancestors first) and rank all non-directories after them.
3202 * That works since everybody except rename does "lock parent, lookup,
3203 * lock child" and rename is under ->s_vfs_rename_mutex.
3204 * HOWEVER, it relies on the assumption that any object with ->lookup()
3205 * has no more than 1 dentry. If "hybrid" objects will ever appear,
3206 * we'd better make sure that there's no link(2) for them.
3207 * d) some filesystems don't support opened-but-unlinked directories,
3208 * either because of layout or because they are not ready to deal with
3209 * all cases correctly. The latter will be fixed (taking this sort of
3210 * stuff into VFS), but the former is not going away. Solution: the same
3211 * trick as in rmdir().
3212 * e) conversion from fhandle to dentry may come in the wrong moment - when
3213 * we are removing the target. Solution: we will have to grab ->i_mutex
3214 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
3215 * ->i_mutex on parents, which works but leads to some truly excessive
3216 * locking].
3218 static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
3219 struct inode *new_dir, struct dentry *new_dentry)
3221 int error = 0;
3222 struct inode *target;
3225 * If we are going to change the parent - check write permissions,
3226 * we'll need to flip '..'.
3228 if (new_dir != old_dir) {
3229 error = inode_permission(old_dentry->d_inode, MAY_WRITE);
3230 if (error)
3231 return error;
3234 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
3235 if (error)
3236 return error;
3238 target = new_dentry->d_inode;
3239 if (target)
3240 mutex_lock(&target->i_mutex);
3241 if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
3242 error = -EBUSY;
3243 else {
3244 if (target)
3245 dentry_unhash(new_dentry);
3246 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
3248 if (target) {
3249 if (!error) {
3250 target->i_flags |= S_DEAD;
3251 dont_mount(new_dentry);
3253 mutex_unlock(&target->i_mutex);
3254 if (d_unhashed(new_dentry))
3255 d_rehash(new_dentry);
3256 dput(new_dentry);
3258 if (!error)
3259 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
3260 d_move(old_dentry,new_dentry);
3261 return error;
3264 static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
3265 struct inode *new_dir, struct dentry *new_dentry)
3267 struct inode *target;
3268 int error;
3270 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
3271 if (error)
3272 return error;
3274 dget(new_dentry);
3275 target = new_dentry->d_inode;
3276 if (target)
3277 mutex_lock(&target->i_mutex);
3278 if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
3279 error = -EBUSY;
3280 else
3281 error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
3282 if (!error) {
3283 if (target)
3284 dont_mount(new_dentry);
3285 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
3286 d_move(old_dentry, new_dentry);
3288 if (target)
3289 mutex_unlock(&target->i_mutex);
3290 dput(new_dentry);
3291 return error;
3294 int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
3295 struct inode *new_dir, struct dentry *new_dentry)
3297 int error;
3298 int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
3299 const unsigned char *old_name;
3301 if (old_dentry->d_inode == new_dentry->d_inode)
3302 return 0;
3304 error = may_delete(old_dir, old_dentry, is_dir);
3305 if (error)
3306 return error;
3308 if (!new_dentry->d_inode)
3309 error = may_create(new_dir, new_dentry);
3310 else
3311 error = may_delete(new_dir, new_dentry, is_dir);
3312 if (error)
3313 return error;
3315 if (!old_dir->i_op->rename)
3316 return -EPERM;
3318 old_name = fsnotify_oldname_init(old_dentry->d_name.name);
3320 if (is_dir)
3321 error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
3322 else
3323 error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
3324 if (!error)
3325 fsnotify_move(old_dir, new_dir, old_name, is_dir,
3326 new_dentry->d_inode, old_dentry);
3327 fsnotify_oldname_free(old_name);
3329 return error;
3332 SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
3333 int, newdfd, const char __user *, newname)
3335 struct dentry *old_dir, *new_dir;
3336 struct dentry *old_dentry, *new_dentry;
3337 struct dentry *trap;
3338 struct nameidata oldnd, newnd;
3339 char *from;
3340 char *to;
3341 int error;
3343 error = user_path_parent(olddfd, oldname, &oldnd, &from);
3344 if (error)
3345 goto exit;
3347 error = user_path_parent(newdfd, newname, &newnd, &to);
3348 if (error)
3349 goto exit1;
3351 error = -EXDEV;
3352 if (oldnd.path.mnt != newnd.path.mnt)
3353 goto exit2;
3355 old_dir = oldnd.path.dentry;
3356 error = -EBUSY;
3357 if (oldnd.last_type != LAST_NORM)
3358 goto exit2;
3360 new_dir = newnd.path.dentry;
3361 if (newnd.last_type != LAST_NORM)
3362 goto exit2;
3364 oldnd.flags &= ~LOOKUP_PARENT;
3365 newnd.flags &= ~LOOKUP_PARENT;
3366 newnd.flags |= LOOKUP_RENAME_TARGET;
3368 trap = lock_rename(new_dir, old_dir);
3370 old_dentry = lookup_hash(&oldnd);
3371 error = PTR_ERR(old_dentry);
3372 if (IS_ERR(old_dentry))
3373 goto exit3;
3374 /* source must exist */
3375 error = -ENOENT;
3376 if (!old_dentry->d_inode)
3377 goto exit4;
3378 /* unless the source is a directory trailing slashes give -ENOTDIR */
3379 if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
3380 error = -ENOTDIR;
3381 if (oldnd.last.name[oldnd.last.len])
3382 goto exit4;
3383 if (newnd.last.name[newnd.last.len])
3384 goto exit4;
3386 /* source should not be ancestor of target */
3387 error = -EINVAL;
3388 if (old_dentry == trap)
3389 goto exit4;
3390 new_dentry = lookup_hash(&newnd);
3391 error = PTR_ERR(new_dentry);
3392 if (IS_ERR(new_dentry))
3393 goto exit4;
3394 /* target should not be an ancestor of source */
3395 error = -ENOTEMPTY;
3396 if (new_dentry == trap)
3397 goto exit5;
3399 error = mnt_want_write(oldnd.path.mnt);
3400 if (error)
3401 goto exit5;
3402 error = security_path_rename(&oldnd.path, old_dentry,
3403 &newnd.path, new_dentry);
3404 if (error)
3405 goto exit6;
3406 error = vfs_rename(old_dir->d_inode, old_dentry,
3407 new_dir->d_inode, new_dentry);
3408 exit6:
3409 mnt_drop_write(oldnd.path.mnt);
3410 exit5:
3411 dput(new_dentry);
3412 exit4:
3413 dput(old_dentry);
3414 exit3:
3415 unlock_rename(new_dir, old_dir);
3416 exit2:
3417 path_put(&newnd.path);
3418 putname(to);
3419 exit1:
3420 path_put(&oldnd.path);
3421 putname(from);
3422 exit:
3423 return error;
3426 SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
3428 return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname);
3431 int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link)
3433 int len;
3435 len = PTR_ERR(link);
3436 if (IS_ERR(link))
3437 goto out;
3439 len = strlen(link);
3440 if (len > (unsigned) buflen)
3441 len = buflen;
3442 if (copy_to_user(buffer, link, len))
3443 len = -EFAULT;
3444 out:
3445 return len;
3449 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
3450 * have ->follow_link() touching nd only in nd_set_link(). Using (or not
3451 * using) it for any given inode is up to filesystem.
3453 int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
3455 struct nameidata nd;
3456 void *cookie;
3457 int res;
3459 nd.depth = 0;
3460 cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
3461 if (IS_ERR(cookie))
3462 return PTR_ERR(cookie);
3464 res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
3465 if (dentry->d_inode->i_op->put_link)
3466 dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
3467 return res;
3470 int vfs_follow_link(struct nameidata *nd, const char *link)
3472 return __vfs_follow_link(nd, link);
3475 /* get the link contents into pagecache */
3476 static char *page_getlink(struct dentry * dentry, struct page **ppage)
3478 char *kaddr;
3479 struct page *page;
3480 struct address_space *mapping = dentry->d_inode->i_mapping;
3481 page = read_mapping_page(mapping, 0, NULL);
3482 if (IS_ERR(page))
3483 return (char*)page;
3484 *ppage = page;
3485 kaddr = kmap(page);
3486 nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1);
3487 return kaddr;
3490 int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
3492 struct page *page = NULL;
3493 char *s = page_getlink(dentry, &page);
3494 int res = vfs_readlink(dentry,buffer,buflen,s);
3495 if (page) {
3496 kunmap(page);
3497 page_cache_release(page);
3499 return res;
3502 void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
3504 struct page *page = NULL;
3505 nd_set_link(nd, page_getlink(dentry, &page));
3506 return page;
3509 void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
3511 struct page *page = cookie;
3513 if (page) {
3514 kunmap(page);
3515 page_cache_release(page);
3520 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
3522 int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
3524 struct address_space *mapping = inode->i_mapping;
3525 struct page *page;
3526 void *fsdata;
3527 int err;
3528 char *kaddr;
3529 unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
3530 if (nofs)
3531 flags |= AOP_FLAG_NOFS;
3533 retry:
3534 err = pagecache_write_begin(NULL, mapping, 0, len-1,
3535 flags, &page, &fsdata);
3536 if (err)
3537 goto fail;
3539 kaddr = kmap_atomic(page, KM_USER0);
3540 memcpy(kaddr, symname, len-1);
3541 kunmap_atomic(kaddr, KM_USER0);
3543 err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
3544 page, fsdata);
3545 if (err < 0)
3546 goto fail;
3547 if (err < len-1)
3548 goto retry;
3550 mark_inode_dirty(inode);
3551 return 0;
3552 fail:
3553 return err;
3556 int page_symlink(struct inode *inode, const char *symname, int len)
3558 return __page_symlink(inode, symname, len,
3559 !(mapping_gfp_mask(inode->i_mapping) & __GFP_FS));
3562 const struct inode_operations page_symlink_inode_operations = {
3563 .readlink = generic_readlink,
3564 .follow_link = page_follow_link_light,
3565 .put_link = page_put_link,
3568 EXPORT_SYMBOL(user_path_at);
3569 EXPORT_SYMBOL(follow_down_one);
3570 EXPORT_SYMBOL(follow_down);
3571 EXPORT_SYMBOL(follow_up);
3572 EXPORT_SYMBOL(get_write_access); /* binfmt_aout */
3573 EXPORT_SYMBOL(getname);
3574 EXPORT_SYMBOL(lock_rename);
3575 EXPORT_SYMBOL(lookup_one_len);
3576 EXPORT_SYMBOL(page_follow_link_light);
3577 EXPORT_SYMBOL(page_put_link);
3578 EXPORT_SYMBOL(page_readlink);
3579 EXPORT_SYMBOL(__page_symlink);
3580 EXPORT_SYMBOL(page_symlink);
3581 EXPORT_SYMBOL(page_symlink_inode_operations);
3582 EXPORT_SYMBOL(path_lookup);
3583 EXPORT_SYMBOL(kern_path);
3584 EXPORT_SYMBOL(vfs_path_lookup);
3585 EXPORT_SYMBOL(inode_permission);
3586 EXPORT_SYMBOL(file_permission);
3587 EXPORT_SYMBOL(unlock_rename);
3588 EXPORT_SYMBOL(vfs_create);
3589 EXPORT_SYMBOL(vfs_follow_link);
3590 EXPORT_SYMBOL(vfs_link);
3591 EXPORT_SYMBOL(vfs_mkdir);
3592 EXPORT_SYMBOL(vfs_mknod);
3593 EXPORT_SYMBOL(generic_permission);
3594 EXPORT_SYMBOL(vfs_readlink);
3595 EXPORT_SYMBOL(vfs_rename);
3596 EXPORT_SYMBOL(vfs_rmdir);
3597 EXPORT_SYMBOL(vfs_symlink);
3598 EXPORT_SYMBOL(vfs_unlink);
3599 EXPORT_SYMBOL(dentry_unhash);
3600 EXPORT_SYMBOL(generic_readlink);