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1 /*
2 * linux/fs/namei.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 */
6
7 /*
8 * Some corrections by tytso.
9 */
10
11 /* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
12 * lookup logic.
13 */
14 /* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.
15 */
16
17 #include <linux/init.h>
18 #include <linux/export.h>
19 #include <linux/kernel.h>
20 #include <linux/slab.h>
21 #include <linux/fs.h>
22 #include <linux/namei.h>
23 #include <linux/pagemap.h>
24 #include <linux/fsnotify.h>
25 #include <linux/personality.h>
26 #include <linux/security.h>
27 #include <linux/ima.h>
28 #include <linux/syscalls.h>
29 #include <linux/mount.h>
30 #include <linux/audit.h>
31 #include <linux/capability.h>
32 #include <linux/file.h>
33 #include <linux/fcntl.h>
34 #include <linux/device_cgroup.h>
35 #include <linux/fs_struct.h>
36 #include <linux/posix_acl.h>
37 #include <asm/uaccess.h>
38
39 #include "internal.h"
40 #include "mount.h"
41
42 /* [Feb-1997 T. Schoebel-Theuer]
43 * Fundamental changes in the pathname lookup mechanisms (namei)
44 * were necessary because of omirr. The reason is that omirr needs
45 * to know the _real_ pathname, not the user-supplied one, in case
46 * of symlinks (and also when transname replacements occur).
47 *
48 * The new code replaces the old recursive symlink resolution with
49 * an iterative one (in case of non-nested symlink chains). It does
50 * this with calls to <fs>_follow_link().
51 * As a side effect, dir_namei(), _namei() and follow_link() are now
52 * replaced with a single function lookup_dentry() that can handle all
53 * the special cases of the former code.
54 *
55 * With the new dcache, the pathname is stored at each inode, at least as
56 * long as the refcount of the inode is positive. As a side effect, the
57 * size of the dcache depends on the inode cache and thus is dynamic.
58 *
59 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
60 * resolution to correspond with current state of the code.
61 *
62 * Note that the symlink resolution is not *completely* iterative.
63 * There is still a significant amount of tail- and mid- recursion in
64 * the algorithm. Also, note that <fs>_readlink() is not used in
65 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
66 * may return different results than <fs>_follow_link(). Many virtual
67 * filesystems (including /proc) exhibit this behavior.
68 */
69
70 /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
71 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
72 * and the name already exists in form of a symlink, try to create the new
73 * name indicated by the symlink. The old code always complained that the
74 * name already exists, due to not following the symlink even if its target
75 * is nonexistent. The new semantics affects also mknod() and link() when
76 * the name is a symlink pointing to a non-existent name.
77 *
78 * I don't know which semantics is the right one, since I have no access
79 * to standards. But I found by trial that HP-UX 9.0 has the full "new"
80 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
81 * "old" one. Personally, I think the new semantics is much more logical.
82 * Note that "ln old new" where "new" is a symlink pointing to a non-existing
83 * file does succeed in both HP-UX and SunOs, but not in Solaris
84 * and in the old Linux semantics.
85 */
86
87 /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
88 * semantics. See the comments in "open_namei" and "do_link" below.
89 *
90 * [10-Sep-98 Alan Modra] Another symlink change.
91 */
92
93 /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
94 * inside the path - always follow.
95 * in the last component in creation/removal/renaming - never follow.
96 * if LOOKUP_FOLLOW passed - follow.
97 * if the pathname has trailing slashes - follow.
98 * otherwise - don't follow.
99 * (applied in that order).
100 *
101 * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
102 * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
103 * During the 2.4 we need to fix the userland stuff depending on it -
104 * hopefully we will be able to get rid of that wart in 2.5. So far only
105 * XEmacs seems to be relying on it...
106 */
107 /*
108 * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
109 * implemented. Let's see if raised priority of ->s_vfs_rename_mutex gives
110 * any extra contention...
111 */
112
113 /* In order to reduce some races, while at the same time doing additional
114 * checking and hopefully speeding things up, we copy filenames to the
115 * kernel data space before using them..
116 *
117 * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
118 * PATH_MAX includes the nul terminator --RR.
119 */
120 void final_putname(struct filename *name)
121 {
122 if (name->separate) {
123 __putname(name->name);
124 kfree(name);
125 } else {
126 __putname(name);
127 }
128 }
129
130 #define EMBEDDED_NAME_MAX (PATH_MAX - sizeof(struct filename))
131
132 static struct filename *
133 getname_flags(const char __user *filename, int flags, int *empty)
134 {
135 struct filename *result, *err;
136 int len;
137 long max;
138 char *kname;
139
140 result = audit_reusename(filename);
141 if (result)
142 return result;
143
144 result = __getname();
145 if (unlikely(!result))
146 return ERR_PTR(-ENOMEM);
147
148 /*
149 * First, try to embed the struct filename inside the names_cache
150 * allocation
151 */
152 kname = (char *)result + sizeof(*result);
153 result->name = kname;
154 result->separate = false;
155 max = EMBEDDED_NAME_MAX;
156
157 recopy:
158 len = strncpy_from_user(kname, filename, max);
159 if (unlikely(len < 0)) {
160 err = ERR_PTR(len);
161 goto error;
162 }
163
164 /*
165 * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a
166 * separate struct filename so we can dedicate the entire
167 * names_cache allocation for the pathname, and re-do the copy from
168 * userland.
169 */
170 if (len == EMBEDDED_NAME_MAX && max == EMBEDDED_NAME_MAX) {
171 kname = (char *)result;
172
173 result = kzalloc(sizeof(*result), GFP_KERNEL);
174 if (!result) {
175 err = ERR_PTR(-ENOMEM);
176 result = (struct filename *)kname;
177 goto error;
178 }
179 result->name = kname;
180 result->separate = true;
181 max = PATH_MAX;
182 goto recopy;
183 }
184
185 /* The empty path is special. */
186 if (unlikely(!len)) {
187 if (empty)
188 *empty = 1;
189 err = ERR_PTR(-ENOENT);
190 if (!(flags & LOOKUP_EMPTY))
191 goto error;
192 }
193
194 err = ERR_PTR(-ENAMETOOLONG);
195 if (unlikely(len >= PATH_MAX))
196 goto error;
197
198 result->uptr = filename;
199 result->aname = NULL;
200 audit_getname(result);
201 return result;
202
203 error:
204 final_putname(result);
205 return err;
206 }
207
208 struct filename *
209 getname(const char __user * filename)
210 {
211 return getname_flags(filename, 0, NULL);
212 }
213
214 /*
215 * The "getname_kernel()" interface doesn't do pathnames longer
216 * than EMBEDDED_NAME_MAX. Deal with it - you're a kernel user.
217 */
218 struct filename *
219 getname_kernel(const char * filename)
220 {
221 struct filename *result;
222 char *kname;
223 int len;
224
225 len = strlen(filename);
226 if (len >= EMBEDDED_NAME_MAX)
227 return ERR_PTR(-ENAMETOOLONG);
228
229 result = __getname();
230 if (unlikely(!result))
231 return ERR_PTR(-ENOMEM);
232
233 kname = (char *)result + sizeof(*result);
234 result->name = kname;
235 result->uptr = NULL;
236 result->aname = NULL;
237 result->separate = false;
238
239 strlcpy(kname, filename, EMBEDDED_NAME_MAX);
240 return result;
241 }
242
243 #ifdef CONFIG_AUDITSYSCALL
244 void putname(struct filename *name)
245 {
246 if (unlikely(!audit_dummy_context()))
247 return audit_putname(name);
248 final_putname(name);
249 }
250 #endif
251
252 static int check_acl(struct inode *inode, int mask)
253 {
254 #ifdef CONFIG_FS_POSIX_ACL
255 struct posix_acl *acl;
256
257 if (mask & MAY_NOT_BLOCK) {
258 acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS);
259 if (!acl)
260 return -EAGAIN;
261 /* no ->get_acl() calls in RCU mode... */
262 if (acl == ACL_NOT_CACHED)
263 return -ECHILD;
264 return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK);
265 }
266
267 acl = get_acl(inode, ACL_TYPE_ACCESS);
268 if (IS_ERR(acl))
269 return PTR_ERR(acl);
270 if (acl) {
271 int error = posix_acl_permission(inode, acl, mask);
272 posix_acl_release(acl);
273 return error;
274 }
275 #endif
276
277 return -EAGAIN;
278 }
279
280 /*
281 * This does the basic permission checking
282 */
283 static int acl_permission_check(struct inode *inode, int mask)
284 {
285 unsigned int mode = inode->i_mode;
286
287 if (likely(uid_eq(current_fsuid(), inode->i_uid)))
288 mode >>= 6;
289 else {
290 if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
291 int error = check_acl(inode, mask);
292 if (error != -EAGAIN)
293 return error;
294 }
295
296 if (in_group_p(inode->i_gid))
297 mode >>= 3;
298 }
299
300 /*
301 * If the DACs are ok we don't need any capability check.
302 */
303 if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0)
304 return 0;
305 return -EACCES;
306 }
307
308 /**
309 * generic_permission - check for access rights on a Posix-like filesystem
310 * @inode: inode to check access rights for
311 * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
312 *
313 * Used to check for read/write/execute permissions on a file.
314 * We use "fsuid" for this, letting us set arbitrary permissions
315 * for filesystem access without changing the "normal" uids which
316 * are used for other things.
317 *
318 * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
319 * request cannot be satisfied (eg. requires blocking or too much complexity).
320 * It would then be called again in ref-walk mode.
321 */
322 int generic_permission(struct inode *inode, int mask)
323 {
324 int ret;
325
326 /*
327 * Do the basic permission checks.
328 */
329 ret = acl_permission_check(inode, mask);
330 if (ret != -EACCES)
331 return ret;
332
333 if (S_ISDIR(inode->i_mode)) {
334 /* DACs are overridable for directories */
335 if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE))
336 return 0;
337 if (!(mask & MAY_WRITE))
338 if (capable_wrt_inode_uidgid(inode,
339 CAP_DAC_READ_SEARCH))
340 return 0;
341 return -EACCES;
342 }
343 /*
344 * Read/write DACs are always overridable.
345 * Executable DACs are overridable when there is
346 * at least one exec bit set.
347 */
348 if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
349 if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE))
350 return 0;
351
352 /*
353 * Searching includes executable on directories, else just read.
354 */
355 mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
356 if (mask == MAY_READ)
357 if (capable_wrt_inode_uidgid(inode, CAP_DAC_READ_SEARCH))
358 return 0;
359
360 return -EACCES;
361 }
362 EXPORT_SYMBOL(generic_permission);
363
364 /*
365 * We _really_ want to just do "generic_permission()" without
366 * even looking at the inode->i_op values. So we keep a cache
367 * flag in inode->i_opflags, that says "this has not special
368 * permission function, use the fast case".
369 */
370 static inline int do_inode_permission(struct inode *inode, int mask)
371 {
372 if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) {
373 if (likely(inode->i_op->permission))
374 return inode->i_op->permission(inode, mask);
375
376 /* This gets set once for the inode lifetime */
377 spin_lock(&inode->i_lock);
378 inode->i_opflags |= IOP_FASTPERM;
379 spin_unlock(&inode->i_lock);
380 }
381 return generic_permission(inode, mask);
382 }
383
384 /**
385 * __inode_permission - Check for access rights to a given inode
386 * @inode: Inode to check permission on
387 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
388 *
389 * Check for read/write/execute permissions on an inode.
390 *
391 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
392 *
393 * This does not check for a read-only file system. You probably want
394 * inode_permission().
395 */
396 int __inode_permission(struct inode *inode, int mask)
397 {
398 int retval;
399
400 if (unlikely(mask & MAY_WRITE)) {
401 /*
402 * Nobody gets write access to an immutable file.
403 */
404 if (IS_IMMUTABLE(inode))
405 return -EACCES;
406 }
407
408 retval = do_inode_permission(inode, mask);
409 if (retval)
410 return retval;
411
412 retval = devcgroup_inode_permission(inode, mask);
413 if (retval)
414 return retval;
415
416 return security_inode_permission(inode, mask);
417 }
418
419 /**
420 * sb_permission - Check superblock-level permissions
421 * @sb: Superblock of inode to check permission on
422 * @inode: Inode to check permission on
423 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
424 *
425 * Separate out file-system wide checks from inode-specific permission checks.
426 */
427 static int sb_permission(struct super_block *sb, struct inode *inode, int mask)
428 {
429 if (unlikely(mask & MAY_WRITE)) {
430 umode_t mode = inode->i_mode;
431
432 /* Nobody gets write access to a read-only fs. */
433 if ((sb->s_flags & MS_RDONLY) &&
434 (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
435 return -EROFS;
436 }
437 return 0;
438 }
439
440 /**
441 * inode_permission - Check for access rights to a given inode
442 * @inode: Inode to check permission on
443 * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
444 *
445 * Check for read/write/execute permissions on an inode. We use fs[ug]id for
446 * this, letting us set arbitrary permissions for filesystem access without
447 * changing the "normal" UIDs which are used for other things.
448 *
449 * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
450 */
451 int inode_permission(struct inode *inode, int mask)
452 {
453 int retval;
454
455 retval = sb_permission(inode->i_sb, inode, mask);
456 if (retval)
457 return retval;
458 return __inode_permission(inode, mask);
459 }
460 EXPORT_SYMBOL(inode_permission);
461
462 /**
463 * path_get - get a reference to a path
464 * @path: path to get the reference to
465 *
466 * Given a path increment the reference count to the dentry and the vfsmount.
467 */
468 void path_get(const struct path *path)
469 {
470 mntget(path->mnt);
471 dget(path->dentry);
472 }
473 EXPORT_SYMBOL(path_get);
474
475 /**
476 * path_put - put a reference to a path
477 * @path: path to put the reference to
478 *
479 * Given a path decrement the reference count to the dentry and the vfsmount.
480 */
481 void path_put(const struct path *path)
482 {
483 dput(path->dentry);
484 mntput(path->mnt);
485 }
486 EXPORT_SYMBOL(path_put);
487
488 /*
489 * Path walking has 2 modes, rcu-walk and ref-walk (see
490 * Documentation/filesystems/path-lookup.txt). In situations when we can't
491 * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
492 * normal reference counts on dentries and vfsmounts to transition to rcu-walk
493 * mode. Refcounts are grabbed at the last known good point before rcu-walk
494 * got stuck, so ref-walk may continue from there. If this is not successful
495 * (eg. a seqcount has changed), then failure is returned and it's up to caller
496 * to restart the path walk from the beginning in ref-walk mode.
497 */
498
499 /**
500 * unlazy_walk - try to switch to ref-walk mode.
501 * @nd: nameidata pathwalk data
502 * @dentry: child of nd->path.dentry or NULL
503 * Returns: 0 on success, -ECHILD on failure
504 *
505 * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry
506 * for ref-walk mode. @dentry must be a path found by a do_lookup call on
507 * @nd or NULL. Must be called from rcu-walk context.
508 */
509 static int unlazy_walk(struct nameidata *nd, struct dentry *dentry)
510 {
511 struct fs_struct *fs = current->fs;
512 struct dentry *parent = nd->path.dentry;
513
514 BUG_ON(!(nd->flags & LOOKUP_RCU));
515
516 /*
517 * After legitimizing the bastards, terminate_walk()
518 * will do the right thing for non-RCU mode, and all our
519 * subsequent exit cases should rcu_read_unlock()
520 * before returning. Do vfsmount first; if dentry
521 * can't be legitimized, just set nd->path.dentry to NULL
522 * and rely on dput(NULL) being a no-op.
523 */
524 if (!legitimize_mnt(nd->path.mnt, nd->m_seq))
525 return -ECHILD;
526 nd->flags &= ~LOOKUP_RCU;
527
528 if (!lockref_get_not_dead(&parent->d_lockref)) {
529 nd->path.dentry = NULL;
530 goto out;
531 }
532
533 /*
534 * For a negative lookup, the lookup sequence point is the parents
535 * sequence point, and it only needs to revalidate the parent dentry.
536 *
537 * For a positive lookup, we need to move both the parent and the
538 * dentry from the RCU domain to be properly refcounted. And the
539 * sequence number in the dentry validates *both* dentry counters,
540 * since we checked the sequence number of the parent after we got
541 * the child sequence number. So we know the parent must still
542 * be valid if the child sequence number is still valid.
543 */
544 if (!dentry) {
545 if (read_seqcount_retry(&parent->d_seq, nd->seq))
546 goto out;
547 BUG_ON(nd->inode != parent->d_inode);
548 } else {
549 if (!lockref_get_not_dead(&dentry->d_lockref))
550 goto out;
551 if (read_seqcount_retry(&dentry->d_seq, nd->seq))
552 goto drop_dentry;
553 }
554
555 /*
556 * Sequence counts matched. Now make sure that the root is
557 * still valid and get it if required.
558 */
559 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
560 spin_lock(&fs->lock);
561 if (nd->root.mnt != fs->root.mnt || nd->root.dentry != fs->root.dentry)
562 goto unlock_and_drop_dentry;
563 path_get(&nd->root);
564 spin_unlock(&fs->lock);
565 }
566
567 rcu_read_unlock();
568 return 0;
569
570 unlock_and_drop_dentry:
571 spin_unlock(&fs->lock);
572 drop_dentry:
573 rcu_read_unlock();
574 dput(dentry);
575 goto drop_root_mnt;
576 out:
577 rcu_read_unlock();
578 drop_root_mnt:
579 if (!(nd->flags & LOOKUP_ROOT))
580 nd->root.mnt = NULL;
581 return -ECHILD;
582 }
583
584 static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
585 {
586 return dentry->d_op->d_revalidate(dentry, flags);
587 }
588
589 /**
590 * complete_walk - successful completion of path walk
591 * @nd: pointer nameidata
592 *
593 * If we had been in RCU mode, drop out of it and legitimize nd->path.
594 * Revalidate the final result, unless we'd already done that during
595 * the path walk or the filesystem doesn't ask for it. Return 0 on
596 * success, -error on failure. In case of failure caller does not
597 * need to drop nd->path.
598 */
599 static int complete_walk(struct nameidata *nd)
600 {
601 struct dentry *dentry = nd->path.dentry;
602 int status;
603
604 if (nd->flags & LOOKUP_RCU) {
605 nd->flags &= ~LOOKUP_RCU;
606 if (!(nd->flags & LOOKUP_ROOT))
607 nd->root.mnt = NULL;
608
609 if (!legitimize_mnt(nd->path.mnt, nd->m_seq)) {
610 rcu_read_unlock();
611 return -ECHILD;
612 }
613 if (unlikely(!lockref_get_not_dead(&dentry->d_lockref))) {
614 rcu_read_unlock();
615 mntput(nd->path.mnt);
616 return -ECHILD;
617 }
618 if (read_seqcount_retry(&dentry->d_seq, nd->seq)) {
619 rcu_read_unlock();
620 dput(dentry);
621 mntput(nd->path.mnt);
622 return -ECHILD;
623 }
624 rcu_read_unlock();
625 }
626
627 if (likely(!(nd->flags & LOOKUP_JUMPED)))
628 return 0;
629
630 if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE)))
631 return 0;
632
633 status = dentry->d_op->d_weak_revalidate(dentry, nd->flags);
634 if (status > 0)
635 return 0;
636
637 if (!status)
638 status = -ESTALE;
639
640 path_put(&nd->path);
641 return status;
642 }
643
644 static __always_inline void set_root(struct nameidata *nd)
645 {
646 if (!nd->root.mnt)
647 get_fs_root(current->fs, &nd->root);
648 }
649
650 static int link_path_walk(const char *, struct nameidata *);
651
652 static __always_inline void set_root_rcu(struct nameidata *nd)
653 {
654 if (!nd->root.mnt) {
655 struct fs_struct *fs = current->fs;
656 unsigned seq;
657
658 do {
659 seq = read_seqcount_begin(&fs->seq);
660 nd->root = fs->root;
661 nd->seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
662 } while (read_seqcount_retry(&fs->seq, seq));
663 }
664 }
665
666 static void path_put_conditional(struct path *path, struct nameidata *nd)
667 {
668 dput(path->dentry);
669 if (path->mnt != nd->path.mnt)
670 mntput(path->mnt);
671 }
672
673 static inline void path_to_nameidata(const struct path *path,
674 struct nameidata *nd)
675 {
676 if (!(nd->flags & LOOKUP_RCU)) {
677 dput(nd->path.dentry);
678 if (nd->path.mnt != path->mnt)
679 mntput(nd->path.mnt);
680 }
681 nd->path.mnt = path->mnt;
682 nd->path.dentry = path->dentry;
683 }
684
685 /*
686 * Helper to directly jump to a known parsed path from ->follow_link,
687 * caller must have taken a reference to path beforehand.
688 */
689 void nd_jump_link(struct nameidata *nd, struct path *path)
690 {
691 path_put(&nd->path);
692
693 nd->path = *path;
694 nd->inode = nd->path.dentry->d_inode;
695 nd->flags |= LOOKUP_JUMPED;
696 }
697
698 static inline void put_link(struct nameidata *nd, struct path *link, void *cookie)
699 {
700 struct inode *inode = link->dentry->d_inode;
701 if (inode->i_op->put_link)
702 inode->i_op->put_link(link->dentry, nd, cookie);
703 path_put(link);
704 }
705
706 int sysctl_protected_symlinks __read_mostly = 0;
707 int sysctl_protected_hardlinks __read_mostly = 0;
708
709 /**
710 * may_follow_link - Check symlink following for unsafe situations
711 * @link: The path of the symlink
712 * @nd: nameidata pathwalk data
713 *
714 * In the case of the sysctl_protected_symlinks sysctl being enabled,
715 * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
716 * in a sticky world-writable directory. This is to protect privileged
717 * processes from failing races against path names that may change out
718 * from under them by way of other users creating malicious symlinks.
719 * It will permit symlinks to be followed only when outside a sticky
720 * world-writable directory, or when the uid of the symlink and follower
721 * match, or when the directory owner matches the symlink's owner.
722 *
723 * Returns 0 if following the symlink is allowed, -ve on error.
724 */
725 static inline int may_follow_link(struct path *link, struct nameidata *nd)
726 {
727 const struct inode *inode;
728 const struct inode *parent;
729
730 if (!sysctl_protected_symlinks)
731 return 0;
732
733 /* Allowed if owner and follower match. */
734 inode = link->dentry->d_inode;
735 if (uid_eq(current_cred()->fsuid, inode->i_uid))
736 return 0;
737
738 /* Allowed if parent directory not sticky and world-writable. */
739 parent = nd->path.dentry->d_inode;
740 if ((parent->i_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH))
741 return 0;
742
743 /* Allowed if parent directory and link owner match. */
744 if (uid_eq(parent->i_uid, inode->i_uid))
745 return 0;
746
747 audit_log_link_denied("follow_link", link);
748 path_put_conditional(link, nd);
749 path_put(&nd->path);
750 return -EACCES;
751 }
752
753 /**
754 * safe_hardlink_source - Check for safe hardlink conditions
755 * @inode: the source inode to hardlink from
756 *
757 * Return false if at least one of the following conditions:
758 * - inode is not a regular file
759 * - inode is setuid
760 * - inode is setgid and group-exec
761 * - access failure for read and write
762 *
763 * Otherwise returns true.
764 */
765 static bool safe_hardlink_source(struct inode *inode)
766 {
767 umode_t mode = inode->i_mode;
768
769 /* Special files should not get pinned to the filesystem. */
770 if (!S_ISREG(mode))
771 return false;
772
773 /* Setuid files should not get pinned to the filesystem. */
774 if (mode & S_ISUID)
775 return false;
776
777 /* Executable setgid files should not get pinned to the filesystem. */
778 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP))
779 return false;
780
781 /* Hardlinking to unreadable or unwritable sources is dangerous. */
782 if (inode_permission(inode, MAY_READ | MAY_WRITE))
783 return false;
784
785 return true;
786 }
787
788 /**
789 * may_linkat - Check permissions for creating a hardlink
790 * @link: the source to hardlink from
791 *
792 * Block hardlink when all of:
793 * - sysctl_protected_hardlinks enabled
794 * - fsuid does not match inode
795 * - hardlink source is unsafe (see safe_hardlink_source() above)
796 * - not CAP_FOWNER
797 *
798 * Returns 0 if successful, -ve on error.
799 */
800 static int may_linkat(struct path *link)
801 {
802 const struct cred *cred;
803 struct inode *inode;
804
805 if (!sysctl_protected_hardlinks)
806 return 0;
807
808 cred = current_cred();
809 inode = link->dentry->d_inode;
810
811 /* Source inode owner (or CAP_FOWNER) can hardlink all they like,
812 * otherwise, it must be a safe source.
813 */
814 if (uid_eq(cred->fsuid, inode->i_uid) || safe_hardlink_source(inode) ||
815 capable(CAP_FOWNER))
816 return 0;
817
818 audit_log_link_denied("linkat", link);
819 return -EPERM;
820 }
821
822 static __always_inline int
823 follow_link(struct path *link, struct nameidata *nd, void **p)
824 {
825 struct dentry *dentry = link->dentry;
826 int error;
827 char *s;
828
829 BUG_ON(nd->flags & LOOKUP_RCU);
830
831 if (link->mnt == nd->path.mnt)
832 mntget(link->mnt);
833
834 error = -ELOOP;
835 if (unlikely(current->total_link_count >= 40))
836 goto out_put_nd_path;
837
838 cond_resched();
839 current->total_link_count++;
840
841 touch_atime(link);
842 nd_set_link(nd, NULL);
843
844 error = security_inode_follow_link(link->dentry, nd);
845 if (error)
846 goto out_put_nd_path;
847
848 nd->last_type = LAST_BIND;
849 *p = dentry->d_inode->i_op->follow_link(dentry, nd);
850 error = PTR_ERR(*p);
851 if (IS_ERR(*p))
852 goto out_put_nd_path;
853
854 error = 0;
855 s = nd_get_link(nd);
856 if (s) {
857 if (unlikely(IS_ERR(s))) {
858 path_put(&nd->path);
859 put_link(nd, link, *p);
860 return PTR_ERR(s);
861 }
862 if (*s == '/') {
863 set_root(nd);
864 path_put(&nd->path);
865 nd->path = nd->root;
866 path_get(&nd->root);
867 nd->flags |= LOOKUP_JUMPED;
868 }
869 nd->inode = nd->path.dentry->d_inode;
870 error = link_path_walk(s, nd);
871 if (unlikely(error))
872 put_link(nd, link, *p);
873 }
874
875 return error;
876
877 out_put_nd_path:
878 *p = NULL;
879 path_put(&nd->path);
880 path_put(link);
881 return error;
882 }
883
884 static int follow_up_rcu(struct path *path)
885 {
886 struct mount *mnt = real_mount(path->mnt);
887 struct mount *parent;
888 struct dentry *mountpoint;
889
890 parent = mnt->mnt_parent;
891 if (&parent->mnt == path->mnt)
892 return 0;
893 mountpoint = mnt->mnt_mountpoint;
894 path->dentry = mountpoint;
895 path->mnt = &parent->mnt;
896 return 1;
897 }
898
899 /*
900 * follow_up - Find the mountpoint of path's vfsmount
901 *
902 * Given a path, find the mountpoint of its source file system.
903 * Replace @path with the path of the mountpoint in the parent mount.
904 * Up is towards /.
905 *
906 * Return 1 if we went up a level and 0 if we were already at the
907 * root.
908 */
909 int follow_up(struct path *path)
910 {
911 struct mount *mnt = real_mount(path->mnt);
912 struct mount *parent;
913 struct dentry *mountpoint;
914
915 read_seqlock_excl(&mount_lock);
916 parent = mnt->mnt_parent;
917 if (parent == mnt) {
918 read_sequnlock_excl(&mount_lock);
919 return 0;
920 }
921 mntget(&parent->mnt);
922 mountpoint = dget(mnt->mnt_mountpoint);
923 read_sequnlock_excl(&mount_lock);
924 dput(path->dentry);
925 path->dentry = mountpoint;
926 mntput(path->mnt);
927 path->mnt = &parent->mnt;
928 return 1;
929 }
930 EXPORT_SYMBOL(follow_up);
931
932 /*
933 * Perform an automount
934 * - return -EISDIR to tell follow_managed() to stop and return the path we
935 * were called with.
936 */
937 static int follow_automount(struct path *path, unsigned flags,
938 bool *need_mntput)
939 {
940 struct vfsmount *mnt;
941 int err;
942
943 if (!path->dentry->d_op || !path->dentry->d_op->d_automount)
944 return -EREMOTE;
945
946 /* We don't want to mount if someone's just doing a stat -
947 * unless they're stat'ing a directory and appended a '/' to
948 * the name.
949 *
950 * We do, however, want to mount if someone wants to open or
951 * create a file of any type under the mountpoint, wants to
952 * traverse through the mountpoint or wants to open the
953 * mounted directory. Also, autofs may mark negative dentries
954 * as being automount points. These will need the attentions
955 * of the daemon to instantiate them before they can be used.
956 */
957 if (!(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
958 LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
959 path->dentry->d_inode)
960 return -EISDIR;
961
962 current->total_link_count++;
963 if (current->total_link_count >= 40)
964 return -ELOOP;
965
966 mnt = path->dentry->d_op->d_automount(path);
967 if (IS_ERR(mnt)) {
968 /*
969 * The filesystem is allowed to return -EISDIR here to indicate
970 * it doesn't want to automount. For instance, autofs would do
971 * this so that its userspace daemon can mount on this dentry.
972 *
973 * However, we can only permit this if it's a terminal point in
974 * the path being looked up; if it wasn't then the remainder of
975 * the path is inaccessible and we should say so.
976 */
977 if (PTR_ERR(mnt) == -EISDIR && (flags & LOOKUP_PARENT))
978 return -EREMOTE;
979 return PTR_ERR(mnt);
980 }
981
982 if (!mnt) /* mount collision */
983 return 0;
984
985 if (!*need_mntput) {
986 /* lock_mount() may release path->mnt on error */
987 mntget(path->mnt);
988 *need_mntput = true;
989 }
990 err = finish_automount(mnt, path);
991
992 switch (err) {
993 case -EBUSY:
994 /* Someone else made a mount here whilst we were busy */
995 return 0;
996 case 0:
997 path_put(path);
998 path->mnt = mnt;
999 path->dentry = dget(mnt->mnt_root);
1000 return 0;
1001 default:
1002 return err;
1003 }
1004
1005 }
1006
1007 /*
1008 * Handle a dentry that is managed in some way.
1009 * - Flagged for transit management (autofs)
1010 * - Flagged as mountpoint
1011 * - Flagged as automount point
1012 *
1013 * This may only be called in refwalk mode.
1014 *
1015 * Serialization is taken care of in namespace.c
1016 */
1017 static int follow_managed(struct path *path, unsigned flags)
1018 {
1019 struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */
1020 unsigned managed;
1021 bool need_mntput = false;
1022 int ret = 0;
1023
1024 /* Given that we're not holding a lock here, we retain the value in a
1025 * local variable for each dentry as we look at it so that we don't see
1026 * the components of that value change under us */
1027 while (managed = ACCESS_ONCE(path->dentry->d_flags),
1028 managed &= DCACHE_MANAGED_DENTRY,
1029 unlikely(managed != 0)) {
1030 /* Allow the filesystem to manage the transit without i_mutex
1031 * being held. */
1032 if (managed & DCACHE_MANAGE_TRANSIT) {
1033 BUG_ON(!path->dentry->d_op);
1034 BUG_ON(!path->dentry->d_op->d_manage);
1035 ret = path->dentry->d_op->d_manage(path->dentry, false);
1036 if (ret < 0)
1037 break;
1038 }
1039
1040 /* Transit to a mounted filesystem. */
1041 if (managed & DCACHE_MOUNTED) {
1042 struct vfsmount *mounted = lookup_mnt(path);
1043 if (mounted) {
1044 dput(path->dentry);
1045 if (need_mntput)
1046 mntput(path->mnt);
1047 path->mnt = mounted;
1048 path->dentry = dget(mounted->mnt_root);
1049 need_mntput = true;
1050 continue;
1051 }
1052
1053 /* Something is mounted on this dentry in another
1054 * namespace and/or whatever was mounted there in this
1055 * namespace got unmounted before lookup_mnt() could
1056 * get it */
1057 }
1058
1059 /* Handle an automount point */
1060 if (managed & DCACHE_NEED_AUTOMOUNT) {
1061 ret = follow_automount(path, flags, &need_mntput);
1062 if (ret < 0)
1063 break;
1064 continue;
1065 }
1066
1067 /* We didn't change the current path point */
1068 break;
1069 }
1070
1071 if (need_mntput && path->mnt == mnt)
1072 mntput(path->mnt);
1073 if (ret == -EISDIR)
1074 ret = 0;
1075 return ret < 0 ? ret : need_mntput;
1076 }
1077
1078 int follow_down_one(struct path *path)
1079 {
1080 struct vfsmount *mounted;
1081
1082 mounted = lookup_mnt(path);
1083 if (mounted) {
1084 dput(path->dentry);
1085 mntput(path->mnt);
1086 path->mnt = mounted;
1087 path->dentry = dget(mounted->mnt_root);
1088 return 1;
1089 }
1090 return 0;
1091 }
1092 EXPORT_SYMBOL(follow_down_one);
1093
1094 static inline bool managed_dentry_might_block(struct dentry *dentry)
1095 {
1096 return (dentry->d_flags & DCACHE_MANAGE_TRANSIT &&
1097 dentry->d_op->d_manage(dentry, true) < 0);
1098 }
1099
1100 /*
1101 * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
1102 * we meet a managed dentry that would need blocking.
1103 */
1104 static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
1105 struct inode **inode)
1106 {
1107 for (;;) {
1108 struct mount *mounted;
1109 /*
1110 * Don't forget we might have a non-mountpoint managed dentry
1111 * that wants to block transit.
1112 */
1113 if (unlikely(managed_dentry_might_block(path->dentry)))
1114 return false;
1115
1116 if (!d_mountpoint(path->dentry))
1117 return true;
1118
1119 mounted = __lookup_mnt(path->mnt, path->dentry);
1120 if (!mounted)
1121 break;
1122 path->mnt = &mounted->mnt;
1123 path->dentry = mounted->mnt.mnt_root;
1124 nd->flags |= LOOKUP_JUMPED;
1125 nd->seq = read_seqcount_begin(&path->dentry->d_seq);
1126 /*
1127 * Update the inode too. We don't need to re-check the
1128 * dentry sequence number here after this d_inode read,
1129 * because a mount-point is always pinned.
1130 */
1131 *inode = path->dentry->d_inode;
1132 }
1133 return read_seqretry(&mount_lock, nd->m_seq);
1134 }
1135
1136 static int follow_dotdot_rcu(struct nameidata *nd)
1137 {
1138 set_root_rcu(nd);
1139
1140 while (1) {
1141 if (nd->path.dentry == nd->root.dentry &&
1142 nd->path.mnt == nd->root.mnt) {
1143 break;
1144 }
1145 if (nd->path.dentry != nd->path.mnt->mnt_root) {
1146 struct dentry *old = nd->path.dentry;
1147 struct dentry *parent = old->d_parent;
1148 unsigned seq;
1149
1150 seq = read_seqcount_begin(&parent->d_seq);
1151 if (read_seqcount_retry(&old->d_seq, nd->seq))
1152 goto failed;
1153 nd->path.dentry = parent;
1154 nd->seq = seq;
1155 break;
1156 }
1157 if (!follow_up_rcu(&nd->path))
1158 break;
1159 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
1160 }
1161 while (d_mountpoint(nd->path.dentry)) {
1162 struct mount *mounted;
1163 mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry);
1164 if (!mounted)
1165 break;
1166 nd->path.mnt = &mounted->mnt;
1167 nd->path.dentry = mounted->mnt.mnt_root;
1168 nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
1169 if (!read_seqretry(&mount_lock, nd->m_seq))
1170 goto failed;
1171 }
1172 nd->inode = nd->path.dentry->d_inode;
1173 return 0;
1174
1175 failed:
1176 nd->flags &= ~LOOKUP_RCU;
1177 if (!(nd->flags & LOOKUP_ROOT))
1178 nd->root.mnt = NULL;
1179 rcu_read_unlock();
1180 return -ECHILD;
1181 }
1182
1183 /*
1184 * Follow down to the covering mount currently visible to userspace. At each
1185 * point, the filesystem owning that dentry may be queried as to whether the
1186 * caller is permitted to proceed or not.
1187 */
1188 int follow_down(struct path *path)
1189 {
1190 unsigned managed;
1191 int ret;
1192
1193 while (managed = ACCESS_ONCE(path->dentry->d_flags),
1194 unlikely(managed & DCACHE_MANAGED_DENTRY)) {
1195 /* Allow the filesystem to manage the transit without i_mutex
1196 * being held.
1197 *
1198 * We indicate to the filesystem if someone is trying to mount
1199 * something here. This gives autofs the chance to deny anyone
1200 * other than its daemon the right to mount on its
1201 * superstructure.
1202 *
1203 * The filesystem may sleep at this point.
1204 */
1205 if (managed & DCACHE_MANAGE_TRANSIT) {
1206 BUG_ON(!path->dentry->d_op);
1207 BUG_ON(!path->dentry->d_op->d_manage);
1208 ret = path->dentry->d_op->d_manage(
1209 path->dentry, false);
1210 if (ret < 0)
1211 return ret == -EISDIR ? 0 : ret;
1212 }
1213
1214 /* Transit to a mounted filesystem. */
1215 if (managed & DCACHE_MOUNTED) {
1216 struct vfsmount *mounted = lookup_mnt(path);
1217 if (!mounted)
1218 break;
1219 dput(path->dentry);
1220 mntput(path->mnt);
1221 path->mnt = mounted;
1222 path->dentry = dget(mounted->mnt_root);
1223 continue;
1224 }
1225
1226 /* Don't handle automount points here */
1227 break;
1228 }
1229 return 0;
1230 }
1231 EXPORT_SYMBOL(follow_down);
1232
1233 /*
1234 * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1235 */
1236 static void follow_mount(struct path *path)
1237 {
1238 while (d_mountpoint(path->dentry)) {
1239 struct vfsmount *mounted = lookup_mnt(path);
1240 if (!mounted)
1241 break;
1242 dput(path->dentry);
1243 mntput(path->mnt);
1244 path->mnt = mounted;
1245 path->dentry = dget(mounted->mnt_root);
1246 }
1247 }
1248
1249 static void follow_dotdot(struct nameidata *nd)
1250 {
1251 set_root(nd);
1252
1253 while(1) {
1254 struct dentry *old = nd->path.dentry;
1255
1256 if (nd->path.dentry == nd->root.dentry &&
1257 nd->path.mnt == nd->root.mnt) {
1258 break;
1259 }
1260 if (nd->path.dentry != nd->path.mnt->mnt_root) {
1261 /* rare case of legitimate dget_parent()... */
1262 nd->path.dentry = dget_parent(nd->path.dentry);
1263 dput(old);
1264 break;
1265 }
1266 if (!follow_up(&nd->path))
1267 break;
1268 }
1269 follow_mount(&nd->path);
1270 nd->inode = nd->path.dentry->d_inode;
1271 }
1272
1273 /*
1274 * This looks up the name in dcache, possibly revalidates the old dentry and
1275 * allocates a new one if not found or not valid. In the need_lookup argument
1276 * returns whether i_op->lookup is necessary.
1277 *
1278 * dir->d_inode->i_mutex must be held
1279 */
1280 static struct dentry *lookup_dcache(struct qstr *name, struct dentry *dir,
1281 unsigned int flags, bool *need_lookup)
1282 {
1283 struct dentry *dentry;
1284 int error;
1285
1286 *need_lookup = false;
1287 dentry = d_lookup(dir, name);
1288 if (dentry) {
1289 if (dentry->d_flags & DCACHE_OP_REVALIDATE) {
1290 error = d_revalidate(dentry, flags);
1291 if (unlikely(error <= 0)) {
1292 if (error < 0) {
1293 dput(dentry);
1294 return ERR_PTR(error);
1295 } else if (!d_invalidate(dentry)) {
1296 dput(dentry);
1297 dentry = NULL;
1298 }
1299 }
1300 }
1301 }
1302
1303 if (!dentry) {
1304 dentry = d_alloc(dir, name);
1305 if (unlikely(!dentry))
1306 return ERR_PTR(-ENOMEM);
1307
1308 *need_lookup = true;
1309 }
1310 return dentry;
1311 }
1312
1313 /*
1314 * Call i_op->lookup on the dentry. The dentry must be negative and
1315 * unhashed.
1316 *
1317 * dir->d_inode->i_mutex must be held
1318 */
1319 static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry,
1320 unsigned int flags)
1321 {
1322 struct dentry *old;
1323
1324 /* Don't create child dentry for a dead directory. */
1325 if (unlikely(IS_DEADDIR(dir))) {
1326 dput(dentry);
1327 return ERR_PTR(-ENOENT);
1328 }
1329
1330 old = dir->i_op->lookup(dir, dentry, flags);
1331 if (unlikely(old)) {
1332 dput(dentry);
1333 dentry = old;
1334 }
1335 return dentry;
1336 }
1337
1338 static struct dentry *__lookup_hash(struct qstr *name,
1339 struct dentry *base, unsigned int flags)
1340 {
1341 bool need_lookup;
1342 struct dentry *dentry;
1343
1344 dentry = lookup_dcache(name, base, flags, &need_lookup);
1345 if (!need_lookup)
1346 return dentry;
1347
1348 return lookup_real(base->d_inode, dentry, flags);
1349 }
1350
1351 /*
1352 * It's more convoluted than I'd like it to be, but... it's still fairly
1353 * small and for now I'd prefer to have fast path as straight as possible.
1354 * It _is_ time-critical.
1355 */
1356 static int lookup_fast(struct nameidata *nd,
1357 struct path *path, struct inode **inode)
1358 {
1359 struct vfsmount *mnt = nd->path.mnt;
1360 struct dentry *dentry, *parent = nd->path.dentry;
1361 int need_reval = 1;
1362 int status = 1;
1363 int err;
1364
1365 /*
1366 * Rename seqlock is not required here because in the off chance
1367 * of a false negative due to a concurrent rename, we're going to
1368 * do the non-racy lookup, below.
1369 */
1370 if (nd->flags & LOOKUP_RCU) {
1371 unsigned seq;
1372 dentry = __d_lookup_rcu(parent, &nd->last, &seq);
1373 if (!dentry)
1374 goto unlazy;
1375
1376 /*
1377 * This sequence count validates that the inode matches
1378 * the dentry name information from lookup.
1379 */
1380 *inode = dentry->d_inode;
1381 if (read_seqcount_retry(&dentry->d_seq, seq))
1382 return -ECHILD;
1383
1384 /*
1385 * This sequence count validates that the parent had no
1386 * changes while we did the lookup of the dentry above.
1387 *
1388 * The memory barrier in read_seqcount_begin of child is
1389 * enough, we can use __read_seqcount_retry here.
1390 */
1391 if (__read_seqcount_retry(&parent->d_seq, nd->seq))
1392 return -ECHILD;
1393 nd->seq = seq;
1394
1395 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
1396 status = d_revalidate(dentry, nd->flags);
1397 if (unlikely(status <= 0)) {
1398 if (status != -ECHILD)
1399 need_reval = 0;
1400 goto unlazy;
1401 }
1402 }
1403 path->mnt = mnt;
1404 path->dentry = dentry;
1405 if (unlikely(!__follow_mount_rcu(nd, path, inode)))
1406 goto unlazy;
1407 if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
1408 goto unlazy;
1409 return 0;
1410 unlazy:
1411 if (unlazy_walk(nd, dentry))
1412 return -ECHILD;
1413 } else {
1414 dentry = __d_lookup(parent, &nd->last);
1415 }
1416
1417 if (unlikely(!dentry))
1418 goto need_lookup;
1419
1420 if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE) && need_reval)
1421 status = d_revalidate(dentry, nd->flags);
1422 if (unlikely(status <= 0)) {
1423 if (status < 0) {
1424 dput(dentry);
1425 return status;
1426 }
1427 if (!d_invalidate(dentry)) {
1428 dput(dentry);
1429 goto need_lookup;
1430 }
1431 }
1432
1433 path->mnt = mnt;
1434 path->dentry = dentry;
1435 err = follow_managed(path, nd->flags);
1436 if (unlikely(err < 0)) {
1437 path_put_conditional(path, nd);
1438 return err;
1439 }
1440 if (err)
1441 nd->flags |= LOOKUP_JUMPED;
1442 *inode = path->dentry->d_inode;
1443 return 0;
1444
1445 need_lookup:
1446 return 1;
1447 }
1448
1449 /* Fast lookup failed, do it the slow way */
1450 static int lookup_slow(struct nameidata *nd, struct path *path)
1451 {
1452 struct dentry *dentry, *parent;
1453 int err;
1454
1455 parent = nd->path.dentry;
1456 BUG_ON(nd->inode != parent->d_inode);
1457
1458 mutex_lock(&parent->d_inode->i_mutex);
1459 dentry = __lookup_hash(&nd->last, parent, nd->flags);
1460 mutex_unlock(&parent->d_inode->i_mutex);
1461 if (IS_ERR(dentry))
1462 return PTR_ERR(dentry);
1463 path->mnt = nd->path.mnt;
1464 path->dentry = dentry;
1465 err = follow_managed(path, nd->flags);
1466 if (unlikely(err < 0)) {
1467 path_put_conditional(path, nd);
1468 return err;
1469 }
1470 if (err)
1471 nd->flags |= LOOKUP_JUMPED;
1472 return 0;
1473 }
1474
1475 static inline int may_lookup(struct nameidata *nd)
1476 {
1477 if (nd->flags & LOOKUP_RCU) {
1478 int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
1479 if (err != -ECHILD)
1480 return err;
1481 if (unlazy_walk(nd, NULL))
1482 return -ECHILD;
1483 }
1484 return inode_permission(nd->inode, MAY_EXEC);
1485 }
1486
1487 static inline int handle_dots(struct nameidata *nd, int type)
1488 {
1489 if (type == LAST_DOTDOT) {
1490 if (nd->flags & LOOKUP_RCU) {
1491 if (follow_dotdot_rcu(nd))
1492 return -ECHILD;
1493 } else
1494 follow_dotdot(nd);
1495 }
1496 return 0;
1497 }
1498
1499 static void terminate_walk(struct nameidata *nd)
1500 {
1501 if (!(nd->flags & LOOKUP_RCU)) {
1502 path_put(&nd->path);
1503 } else {
1504 nd->flags &= ~LOOKUP_RCU;
1505 if (!(nd->flags & LOOKUP_ROOT))
1506 nd->root.mnt = NULL;
1507 rcu_read_unlock();
1508 }
1509 }
1510
1511 /*
1512 * Do we need to follow links? We _really_ want to be able
1513 * to do this check without having to look at inode->i_op,
1514 * so we keep a cache of "no, this doesn't need follow_link"
1515 * for the common case.
1516 */
1517 static inline int should_follow_link(struct dentry *dentry, int follow)
1518 {
1519 return unlikely(d_is_symlink(dentry)) ? follow : 0;
1520 }
1521
1522 static inline int walk_component(struct nameidata *nd, struct path *path,
1523 int follow)
1524 {
1525 struct inode *inode;
1526 int err;
1527 /*
1528 * "." and ".." are special - ".." especially so because it has
1529 * to be able to know about the current root directory and
1530 * parent relationships.
1531 */
1532 if (unlikely(nd->last_type != LAST_NORM))
1533 return handle_dots(nd, nd->last_type);
1534 err = lookup_fast(nd, path, &inode);
1535 if (unlikely(err)) {
1536 if (err < 0)
1537 goto out_err;
1538
1539 err = lookup_slow(nd, path);
1540 if (err < 0)
1541 goto out_err;
1542
1543 inode = path->dentry->d_inode;
1544 }
1545 err = -ENOENT;
1546 if (!inode || d_is_negative(path->dentry))
1547 goto out_path_put;
1548
1549 if (should_follow_link(path->dentry, follow)) {
1550 if (nd->flags & LOOKUP_RCU) {
1551 if (unlikely(unlazy_walk(nd, path->dentry))) {
1552 err = -ECHILD;
1553 goto out_err;
1554 }
1555 }
1556 BUG_ON(inode != path->dentry->d_inode);
1557 return 1;
1558 }
1559 path_to_nameidata(path, nd);
1560 nd->inode = inode;
1561 return 0;
1562
1563 out_path_put:
1564 path_to_nameidata(path, nd);
1565 out_err:
1566 terminate_walk(nd);
1567 return err;
1568 }
1569
1570 /*
1571 * This limits recursive symlink follows to 8, while
1572 * limiting consecutive symlinks to 40.
1573 *
1574 * Without that kind of total limit, nasty chains of consecutive
1575 * symlinks can cause almost arbitrarily long lookups.
1576 */
1577 static inline int nested_symlink(struct path *path, struct nameidata *nd)
1578 {
1579 int res;
1580
1581 if (unlikely(current->link_count >= MAX_NESTED_LINKS)) {
1582 path_put_conditional(path, nd);
1583 path_put(&nd->path);
1584 return -ELOOP;
1585 }
1586 BUG_ON(nd->depth >= MAX_NESTED_LINKS);
1587
1588 nd->depth++;
1589 current->link_count++;
1590
1591 do {
1592 struct path link = *path;
1593 void *cookie;
1594
1595 res = follow_link(&link, nd, &cookie);
1596 if (res)
1597 break;
1598 res = walk_component(nd, path, LOOKUP_FOLLOW);
1599 put_link(nd, &link, cookie);
1600 } while (res > 0);
1601
1602 current->link_count--;
1603 nd->depth--;
1604 return res;
1605 }
1606
1607 /*
1608 * We can do the critical dentry name comparison and hashing
1609 * operations one word at a time, but we are limited to:
1610 *
1611 * - Architectures with fast unaligned word accesses. We could
1612 * do a "get_unaligned()" if this helps and is sufficiently
1613 * fast.
1614 *
1615 * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
1616 * do not trap on the (extremely unlikely) case of a page
1617 * crossing operation.
1618 *
1619 * - Furthermore, we need an efficient 64-bit compile for the
1620 * 64-bit case in order to generate the "number of bytes in
1621 * the final mask". Again, that could be replaced with a
1622 * efficient population count instruction or similar.
1623 */
1624 #ifdef CONFIG_DCACHE_WORD_ACCESS
1625
1626 #include <asm/word-at-a-time.h>
1627
1628 #ifdef CONFIG_64BIT
1629
1630 static inline unsigned int fold_hash(unsigned long hash)
1631 {
1632 hash += hash >> (8*sizeof(int));
1633 return hash;
1634 }
1635
1636 #else /* 32-bit case */
1637
1638 #define fold_hash(x) (x)
1639
1640 #endif
1641
1642 unsigned int full_name_hash(const unsigned char *name, unsigned int len)
1643 {
1644 unsigned long a, mask;
1645 unsigned long hash = 0;
1646
1647 for (;;) {
1648 a = load_unaligned_zeropad(name);
1649 if (len < sizeof(unsigned long))
1650 break;
1651 hash += a;
1652 hash *= 9;
1653 name += sizeof(unsigned long);
1654 len -= sizeof(unsigned long);
1655 if (!len)
1656 goto done;
1657 }
1658 mask = bytemask_from_count(len);
1659 hash += mask & a;
1660 done:
1661 return fold_hash(hash);
1662 }
1663 EXPORT_SYMBOL(full_name_hash);
1664
1665 /*
1666 * Calculate the length and hash of the path component, and
1667 * return the length of the component;
1668 */
1669 static inline unsigned long hash_name(const char *name, unsigned int *hashp)
1670 {
1671 unsigned long a, b, adata, bdata, mask, hash, len;
1672 const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
1673
1674 hash = a = 0;
1675 len = -sizeof(unsigned long);
1676 do {
1677 hash = (hash + a) * 9;
1678 len += sizeof(unsigned long);
1679 a = load_unaligned_zeropad(name+len);
1680 b = a ^ REPEAT_BYTE('/');
1681 } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants)));
1682
1683 adata = prep_zero_mask(a, adata, &constants);
1684 bdata = prep_zero_mask(b, bdata, &constants);
1685
1686 mask = create_zero_mask(adata | bdata);
1687
1688 hash += a & zero_bytemask(mask);
1689 *hashp = fold_hash(hash);
1690
1691 return len + find_zero(mask);
1692 }
1693
1694 #else
1695
1696 unsigned int full_name_hash(const unsigned char *name, unsigned int len)
1697 {
1698 unsigned long hash = init_name_hash();
1699 while (len--)
1700 hash = partial_name_hash(*name++, hash);
1701 return end_name_hash(hash);
1702 }
1703 EXPORT_SYMBOL(full_name_hash);
1704
1705 /*
1706 * We know there's a real path component here of at least
1707 * one character.
1708 */
1709 static inline unsigned long hash_name(const char *name, unsigned int *hashp)
1710 {
1711 unsigned long hash = init_name_hash();
1712 unsigned long len = 0, c;
1713
1714 c = (unsigned char)*name;
1715 do {
1716 len++;
1717 hash = partial_name_hash(c, hash);
1718 c = (unsigned char)name[len];
1719 } while (c && c != '/');
1720 *hashp = end_name_hash(hash);
1721 return len;
1722 }
1723
1724 #endif
1725
1726 /*
1727 * Name resolution.
1728 * This is the basic name resolution function, turning a pathname into
1729 * the final dentry. We expect 'base' to be positive and a directory.
1730 *
1731 * Returns 0 and nd will have valid dentry and mnt on success.
1732 * Returns error and drops reference to input namei data on failure.
1733 */
1734 static int link_path_walk(const char *name, struct nameidata *nd)
1735 {
1736 struct path next;
1737 int err;
1738
1739 while (*name=='/')
1740 name++;
1741 if (!*name)
1742 return 0;
1743
1744 /* At this point we know we have a real path component. */
1745 for(;;) {
1746 struct qstr this;
1747 long len;
1748 int type;
1749
1750 err = may_lookup(nd);
1751 if (err)
1752 break;
1753
1754 len = hash_name(name, &this.hash);
1755 this.name = name;
1756 this.len = len;
1757
1758 type = LAST_NORM;
1759 if (name[0] == '.') switch (len) {
1760 case 2:
1761 if (name[1] == '.') {
1762 type = LAST_DOTDOT;
1763 nd->flags |= LOOKUP_JUMPED;
1764 }
1765 break;
1766 case 1:
1767 type = LAST_DOT;
1768 }
1769 if (likely(type == LAST_NORM)) {
1770 struct dentry *parent = nd->path.dentry;
1771 nd->flags &= ~LOOKUP_JUMPED;
1772 if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
1773 err = parent->d_op->d_hash(parent, &this);
1774 if (err < 0)
1775 break;
1776 }
1777 }
1778
1779 nd->last = this;
1780 nd->last_type = type;
1781
1782 if (!name[len])
1783 return 0;
1784 /*
1785 * If it wasn't NUL, we know it was '/'. Skip that
1786 * slash, and continue until no more slashes.
1787 */
1788 do {
1789 len++;
1790 } while (unlikely(name[len] == '/'));
1791 if (!name[len])
1792 return 0;
1793
1794 name += len;
1795
1796 err = walk_component(nd, &next, LOOKUP_FOLLOW);
1797 if (err < 0)
1798 return err;
1799
1800 if (err) {
1801 err = nested_symlink(&next, nd);
1802 if (err)
1803 return err;
1804 }
1805 if (!d_can_lookup(nd->path.dentry)) {
1806 err = -ENOTDIR;
1807 break;
1808 }
1809 }
1810 terminate_walk(nd);
1811 return err;
1812 }
1813
1814 static int path_init(int dfd, const char *name, unsigned int flags,
1815 struct nameidata *nd, struct file **fp)
1816 {
1817 int retval = 0;
1818
1819 nd->last_type = LAST_ROOT; /* if there are only slashes... */
1820 nd->flags = flags | LOOKUP_JUMPED;
1821 nd->depth = 0;
1822 if (flags & LOOKUP_ROOT) {
1823 struct dentry *root = nd->root.dentry;
1824 struct inode *inode = root->d_inode;
1825 if (*name) {
1826 if (!d_can_lookup(root))
1827 return -ENOTDIR;
1828 retval = inode_permission(inode, MAY_EXEC);
1829 if (retval)
1830 return retval;
1831 }
1832 nd->path = nd->root;
1833 nd->inode = inode;
1834 if (flags & LOOKUP_RCU) {
1835 rcu_read_lock();
1836 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1837 nd->m_seq = read_seqbegin(&mount_lock);
1838 } else {
1839 path_get(&nd->path);
1840 }
1841 return 0;
1842 }
1843
1844 nd->root.mnt = NULL;
1845
1846 nd->m_seq = read_seqbegin(&mount_lock);
1847 if (*name=='/') {
1848 if (flags & LOOKUP_RCU) {
1849 rcu_read_lock();
1850 set_root_rcu(nd);
1851 } else {
1852 set_root(nd);
1853 path_get(&nd->root);
1854 }
1855 nd->path = nd->root;
1856 } else if (dfd == AT_FDCWD) {
1857 if (flags & LOOKUP_RCU) {
1858 struct fs_struct *fs = current->fs;
1859 unsigned seq;
1860
1861 rcu_read_lock();
1862
1863 do {
1864 seq = read_seqcount_begin(&fs->seq);
1865 nd->path = fs->pwd;
1866 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1867 } while (read_seqcount_retry(&fs->seq, seq));
1868 } else {
1869 get_fs_pwd(current->fs, &nd->path);
1870 }
1871 } else {
1872 /* Caller must check execute permissions on the starting path component */
1873 struct fd f = fdget_raw(dfd);
1874 struct dentry *dentry;
1875
1876 if (!f.file)
1877 return -EBADF;
1878
1879 dentry = f.file->f_path.dentry;
1880
1881 if (*name) {
1882 if (!d_can_lookup(dentry)) {
1883 fdput(f);
1884 return -ENOTDIR;
1885 }
1886 }
1887
1888 nd->path = f.file->f_path;
1889 if (flags & LOOKUP_RCU) {
1890 if (f.flags & FDPUT_FPUT)
1891 *fp = f.file;
1892 nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1893 rcu_read_lock();
1894 } else {
1895 path_get(&nd->path);
1896 fdput(f);
1897 }
1898 }
1899
1900 nd->inode = nd->path.dentry->d_inode;
1901 return 0;
1902 }
1903
1904 static inline int lookup_last(struct nameidata *nd, struct path *path)
1905 {
1906 if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
1907 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
1908
1909 nd->flags &= ~LOOKUP_PARENT;
1910 return walk_component(nd, path, nd->flags & LOOKUP_FOLLOW);
1911 }
1912
1913 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
1914 static int path_lookupat(int dfd, const char *name,
1915 unsigned int flags, struct nameidata *nd)
1916 {
1917 struct file *base = NULL;
1918 struct path path;
1919 int err;
1920
1921 /*
1922 * Path walking is largely split up into 2 different synchronisation
1923 * schemes, rcu-walk and ref-walk (explained in
1924 * Documentation/filesystems/path-lookup.txt). These share much of the
1925 * path walk code, but some things particularly setup, cleanup, and
1926 * following mounts are sufficiently divergent that functions are
1927 * duplicated. Typically there is a function foo(), and its RCU
1928 * analogue, foo_rcu().
1929 *
1930 * -ECHILD is the error number of choice (just to avoid clashes) that
1931 * is returned if some aspect of an rcu-walk fails. Such an error must
1932 * be handled by restarting a traditional ref-walk (which will always
1933 * be able to complete).
1934 */
1935 err = path_init(dfd, name, flags | LOOKUP_PARENT, nd, &base);
1936
1937 if (unlikely(err))
1938 return err;
1939
1940 current->total_link_count = 0;
1941 err = link_path_walk(name, nd);
1942
1943 if (!err && !(flags & LOOKUP_PARENT)) {
1944 err = lookup_last(nd, &path);
1945 while (err > 0) {
1946 void *cookie;
1947 struct path link = path;
1948 err = may_follow_link(&link, nd);
1949 if (unlikely(err))
1950 break;
1951 nd->flags |= LOOKUP_PARENT;
1952 err = follow_link(&link, nd, &cookie);
1953 if (err)
1954 break;
1955 err = lookup_last(nd, &path);
1956 put_link(nd, &link, cookie);
1957 }
1958 }
1959
1960 if (!err)
1961 err = complete_walk(nd);
1962
1963 if (!err && nd->flags & LOOKUP_DIRECTORY) {
1964 if (!d_can_lookup(nd->path.dentry)) {
1965 path_put(&nd->path);
1966 err = -ENOTDIR;
1967 }
1968 }
1969
1970 if (base)
1971 fput(base);
1972
1973 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
1974 path_put(&nd->root);
1975 nd->root.mnt = NULL;
1976 }
1977 return err;
1978 }
1979
1980 static int filename_lookup(int dfd, struct filename *name,
1981 unsigned int flags, struct nameidata *nd)
1982 {
1983 int retval = path_lookupat(dfd, name->name, flags | LOOKUP_RCU, nd);
1984 if (unlikely(retval == -ECHILD))
1985 retval = path_lookupat(dfd, name->name, flags, nd);
1986 if (unlikely(retval == -ESTALE))
1987 retval = path_lookupat(dfd, name->name,
1988 flags | LOOKUP_REVAL, nd);
1989
1990 if (likely(!retval))
1991 audit_inode(name, nd->path.dentry, flags & LOOKUP_PARENT);
1992 return retval;
1993 }
1994
1995 static int do_path_lookup(int dfd, const char *name,
1996 unsigned int flags, struct nameidata *nd)
1997 {
1998 struct filename filename = { .name = name };
1999
2000 return filename_lookup(dfd, &filename, flags, nd);
2001 }
2002
2003 /* does lookup, returns the object with parent locked */
2004 struct dentry *kern_path_locked(const char *name, struct path *path)
2005 {
2006 struct nameidata nd;
2007 struct dentry *d;
2008 int err = do_path_lookup(AT_FDCWD, name, LOOKUP_PARENT, &nd);
2009 if (err)
2010 return ERR_PTR(err);
2011 if (nd.last_type != LAST_NORM) {
2012 path_put(&nd.path);
2013 return ERR_PTR(-EINVAL);
2014 }
2015 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2016 d = __lookup_hash(&nd.last, nd.path.dentry, 0);
2017 if (IS_ERR(d)) {
2018 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2019 path_put(&nd.path);
2020 return d;
2021 }
2022 *path = nd.path;
2023 return d;
2024 }
2025
2026 int kern_path(const char *name, unsigned int flags, struct path *path)
2027 {
2028 struct nameidata nd;
2029 int res = do_path_lookup(AT_FDCWD, name, flags, &nd);
2030 if (!res)
2031 *path = nd.path;
2032 return res;
2033 }
2034 EXPORT_SYMBOL(kern_path);
2035
2036 /**
2037 * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
2038 * @dentry: pointer to dentry of the base directory
2039 * @mnt: pointer to vfs mount of the base directory
2040 * @name: pointer to file name
2041 * @flags: lookup flags
2042 * @path: pointer to struct path to fill
2043 */
2044 int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
2045 const char *name, unsigned int flags,
2046 struct path *path)
2047 {
2048 struct nameidata nd;
2049 int err;
2050 nd.root.dentry = dentry;
2051 nd.root.mnt = mnt;
2052 BUG_ON(flags & LOOKUP_PARENT);
2053 /* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */
2054 err = do_path_lookup(AT_FDCWD, name, flags | LOOKUP_ROOT, &nd);
2055 if (!err)
2056 *path = nd.path;
2057 return err;
2058 }
2059 EXPORT_SYMBOL(vfs_path_lookup);
2060
2061 /*
2062 * Restricted form of lookup. Doesn't follow links, single-component only,
2063 * needs parent already locked. Doesn't follow mounts.
2064 * SMP-safe.
2065 */
2066 static struct dentry *lookup_hash(struct nameidata *nd)
2067 {
2068 return __lookup_hash(&nd->last, nd->path.dentry, nd->flags);
2069 }
2070
2071 /**
2072 * lookup_one_len - filesystem helper to lookup single pathname component
2073 * @name: pathname component to lookup
2074 * @base: base directory to lookup from
2075 * @len: maximum length @len should be interpreted to
2076 *
2077 * Note that this routine is purely a helper for filesystem usage and should
2078 * not be called by generic code. Also note that by using this function the
2079 * nameidata argument is passed to the filesystem methods and a filesystem
2080 * using this helper needs to be prepared for that.
2081 */
2082 struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
2083 {
2084 struct qstr this;
2085 unsigned int c;
2086 int err;
2087
2088 WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));
2089
2090 this.name = name;
2091 this.len = len;
2092 this.hash = full_name_hash(name, len);
2093 if (!len)
2094 return ERR_PTR(-EACCES);
2095
2096 if (unlikely(name[0] == '.')) {
2097 if (len < 2 || (len == 2 && name[1] == '.'))
2098 return ERR_PTR(-EACCES);
2099 }
2100
2101 while (len--) {
2102 c = *(const unsigned char *)name++;
2103 if (c == '/' || c == '\0')
2104 return ERR_PTR(-EACCES);
2105 }
2106 /*
2107 * See if the low-level filesystem might want
2108 * to use its own hash..
2109 */
2110 if (base->d_flags & DCACHE_OP_HASH) {
2111 int err = base->d_op->d_hash(base, &this);
2112 if (err < 0)
2113 return ERR_PTR(err);
2114 }
2115
2116 err = inode_permission(base->d_inode, MAY_EXEC);
2117 if (err)
2118 return ERR_PTR(err);
2119
2120 return __lookup_hash(&this, base, 0);
2121 }
2122 EXPORT_SYMBOL(lookup_one_len);
2123
2124 int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
2125 struct path *path, int *empty)
2126 {
2127 struct nameidata nd;
2128 struct filename *tmp = getname_flags(name, flags, empty);
2129 int err = PTR_ERR(tmp);
2130 if (!IS_ERR(tmp)) {
2131
2132 BUG_ON(flags & LOOKUP_PARENT);
2133
2134 err = filename_lookup(dfd, tmp, flags, &nd);
2135 putname(tmp);
2136 if (!err)
2137 *path = nd.path;
2138 }
2139 return err;
2140 }
2141
2142 int user_path_at(int dfd, const char __user *name, unsigned flags,
2143 struct path *path)
2144 {
2145 return user_path_at_empty(dfd, name, flags, path, NULL);
2146 }
2147 EXPORT_SYMBOL(user_path_at);
2148
2149 /*
2150 * NB: most callers don't do anything directly with the reference to the
2151 * to struct filename, but the nd->last pointer points into the name string
2152 * allocated by getname. So we must hold the reference to it until all
2153 * path-walking is complete.
2154 */
2155 static struct filename *
2156 user_path_parent(int dfd, const char __user *path, struct nameidata *nd,
2157 unsigned int flags)
2158 {
2159 struct filename *s = getname(path);
2160 int error;
2161
2162 /* only LOOKUP_REVAL is allowed in extra flags */
2163 flags &= LOOKUP_REVAL;
2164
2165 if (IS_ERR(s))
2166 return s;
2167
2168 error = filename_lookup(dfd, s, flags | LOOKUP_PARENT, nd);
2169 if (error) {
2170 putname(s);
2171 return ERR_PTR(error);
2172 }
2173
2174 return s;
2175 }
2176
2177 /**
2178 * mountpoint_last - look up last component for umount
2179 * @nd: pathwalk nameidata - currently pointing at parent directory of "last"
2180 * @path: pointer to container for result
2181 *
2182 * This is a special lookup_last function just for umount. In this case, we
2183 * need to resolve the path without doing any revalidation.
2184 *
2185 * The nameidata should be the result of doing a LOOKUP_PARENT pathwalk. Since
2186 * mountpoints are always pinned in the dcache, their ancestors are too. Thus,
2187 * in almost all cases, this lookup will be served out of the dcache. The only
2188 * cases where it won't are if nd->last refers to a symlink or the path is
2189 * bogus and it doesn't exist.
2190 *
2191 * Returns:
2192 * -error: if there was an error during lookup. This includes -ENOENT if the
2193 * lookup found a negative dentry. The nd->path reference will also be
2194 * put in this case.
2195 *
2196 * 0: if we successfully resolved nd->path and found it to not to be a
2197 * symlink that needs to be followed. "path" will also be populated.
2198 * The nd->path reference will also be put.
2199 *
2200 * 1: if we successfully resolved nd->last and found it to be a symlink
2201 * that needs to be followed. "path" will be populated with the path
2202 * to the link, and nd->path will *not* be put.
2203 */
2204 static int
2205 mountpoint_last(struct nameidata *nd, struct path *path)
2206 {
2207 int error = 0;
2208 struct dentry *dentry;
2209 struct dentry *dir = nd->path.dentry;
2210
2211 /* If we're in rcuwalk, drop out of it to handle last component */
2212 if (nd->flags & LOOKUP_RCU) {
2213 if (unlazy_walk(nd, NULL)) {
2214 error = -ECHILD;
2215 goto out;
2216 }
2217 }
2218
2219 nd->flags &= ~LOOKUP_PARENT;
2220
2221 if (unlikely(nd->last_type != LAST_NORM)) {
2222 error = handle_dots(nd, nd->last_type);
2223 if (error)
2224 goto out;
2225 dentry = dget(nd->path.dentry);
2226 goto done;
2227 }
2228
2229 mutex_lock(&dir->d_inode->i_mutex);
2230 dentry = d_lookup(dir, &nd->last);
2231 if (!dentry) {
2232 /*
2233 * No cached dentry. Mounted dentries are pinned in the cache,
2234 * so that means that this dentry is probably a symlink or the
2235 * path doesn't actually point to a mounted dentry.
2236 */
2237 dentry = d_alloc(dir, &nd->last);
2238 if (!dentry) {
2239 error = -ENOMEM;
2240 mutex_unlock(&dir->d_inode->i_mutex);
2241 goto out;
2242 }
2243 dentry = lookup_real(dir->d_inode, dentry, nd->flags);
2244 error = PTR_ERR(dentry);
2245 if (IS_ERR(dentry)) {
2246 mutex_unlock(&dir->d_inode->i_mutex);
2247 goto out;
2248 }
2249 }
2250 mutex_unlock(&dir->d_inode->i_mutex);
2251
2252 done:
2253 if (!dentry->d_inode || d_is_negative(dentry)) {
2254 error = -ENOENT;
2255 dput(dentry);
2256 goto out;
2257 }
2258 path->dentry = dentry;
2259 path->mnt = mntget(nd->path.mnt);
2260 if (should_follow_link(dentry, nd->flags & LOOKUP_FOLLOW))
2261 return 1;
2262 follow_mount(path);
2263 error = 0;
2264 out:
2265 terminate_walk(nd);
2266 return error;
2267 }
2268
2269 /**
2270 * path_mountpoint - look up a path to be umounted
2271 * @dfd: directory file descriptor to start walk from
2272 * @name: full pathname to walk
2273 * @path: pointer to container for result
2274 * @flags: lookup flags
2275 *
2276 * Look up the given name, but don't attempt to revalidate the last component.
2277 * Returns 0 and "path" will be valid on success; Returns error otherwise.
2278 */
2279 static int
2280 path_mountpoint(int dfd, const char *name, struct path *path, unsigned int flags)
2281 {
2282 struct file *base = NULL;
2283 struct nameidata nd;
2284 int err;
2285
2286 err = path_init(dfd, name, flags | LOOKUP_PARENT, &nd, &base);
2287 if (unlikely(err))
2288 return err;
2289
2290 current->total_link_count = 0;
2291 err = link_path_walk(name, &nd);
2292 if (err)
2293 goto out;
2294
2295 err = mountpoint_last(&nd, path);
2296 while (err > 0) {
2297 void *cookie;
2298 struct path link = *path;
2299 err = may_follow_link(&link, &nd);
2300 if (unlikely(err))
2301 break;
2302 nd.flags |= LOOKUP_PARENT;
2303 err = follow_link(&link, &nd, &cookie);
2304 if (err)
2305 break;
2306 err = mountpoint_last(&nd, path);
2307 put_link(&nd, &link, cookie);
2308 }
2309 out:
2310 if (base)
2311 fput(base);
2312
2313 if (nd.root.mnt && !(nd.flags & LOOKUP_ROOT))
2314 path_put(&nd.root);
2315
2316 return err;
2317 }
2318
2319 static int
2320 filename_mountpoint(int dfd, struct filename *s, struct path *path,
2321 unsigned int flags)
2322 {
2323 int error = path_mountpoint(dfd, s->name, path, flags | LOOKUP_RCU);
2324 if (unlikely(error == -ECHILD))
2325 error = path_mountpoint(dfd, s->name, path, flags);
2326 if (unlikely(error == -ESTALE))
2327 error = path_mountpoint(dfd, s->name, path, flags | LOOKUP_REVAL);
2328 if (likely(!error))
2329 audit_inode(s, path->dentry, 0);
2330 return error;
2331 }
2332
2333 /**
2334 * user_path_mountpoint_at - lookup a path from userland in order to umount it
2335 * @dfd: directory file descriptor
2336 * @name: pathname from userland
2337 * @flags: lookup flags
2338 * @path: pointer to container to hold result
2339 *
2340 * A umount is a special case for path walking. We're not actually interested
2341 * in the inode in this situation, and ESTALE errors can be a problem. We
2342 * simply want track down the dentry and vfsmount attached at the mountpoint
2343 * and avoid revalidating the last component.
2344 *
2345 * Returns 0 and populates "path" on success.
2346 */
2347 int
2348 user_path_mountpoint_at(int dfd, const char __user *name, unsigned int flags,
2349 struct path *path)
2350 {
2351 struct filename *s = getname(name);
2352 int error;
2353 if (IS_ERR(s))
2354 return PTR_ERR(s);
2355 error = filename_mountpoint(dfd, s, path, flags);
2356 putname(s);
2357 return error;
2358 }
2359
2360 int
2361 kern_path_mountpoint(int dfd, const char *name, struct path *path,
2362 unsigned int flags)
2363 {
2364 struct filename s = {.name = name};
2365 return filename_mountpoint(dfd, &s, path, flags);
2366 }
2367 EXPORT_SYMBOL(kern_path_mountpoint);
2368
2369 /*
2370 * It's inline, so penalty for filesystems that don't use sticky bit is
2371 * minimal.
2372 */
2373 static inline int check_sticky(struct inode *dir, struct inode *inode)
2374 {
2375 kuid_t fsuid = current_fsuid();
2376
2377 if (!(dir->i_mode & S_ISVTX))
2378 return 0;
2379 if (uid_eq(inode->i_uid, fsuid))
2380 return 0;
2381 if (uid_eq(dir->i_uid, fsuid))
2382 return 0;
2383 return !capable_wrt_inode_uidgid(inode, CAP_FOWNER);
2384 }
2385
2386 /*
2387 * Check whether we can remove a link victim from directory dir, check
2388 * whether the type of victim is right.
2389 * 1. We can't do it if dir is read-only (done in permission())
2390 * 2. We should have write and exec permissions on dir
2391 * 3. We can't remove anything from append-only dir
2392 * 4. We can't do anything with immutable dir (done in permission())
2393 * 5. If the sticky bit on dir is set we should either
2394 * a. be owner of dir, or
2395 * b. be owner of victim, or
2396 * c. have CAP_FOWNER capability
2397 * 6. If the victim is append-only or immutable we can't do antyhing with
2398 * links pointing to it.
2399 * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
2400 * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
2401 * 9. We can't remove a root or mountpoint.
2402 * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
2403 * nfs_async_unlink().
2404 */
2405 static int may_delete(struct inode *dir, struct dentry *victim, bool isdir)
2406 {
2407 struct inode *inode = victim->d_inode;
2408 int error;
2409
2410 if (d_is_negative(victim))
2411 return -ENOENT;
2412 BUG_ON(!inode);
2413
2414 BUG_ON(victim->d_parent->d_inode != dir);
2415 audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE);
2416
2417 error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
2418 if (error)
2419 return error;
2420 if (IS_APPEND(dir))
2421 return -EPERM;
2422
2423 if (check_sticky(dir, inode) || IS_APPEND(inode) ||
2424 IS_IMMUTABLE(inode) || IS_SWAPFILE(inode))
2425 return -EPERM;
2426 if (isdir) {
2427 if (!d_is_dir(victim))
2428 return -ENOTDIR;
2429 if (IS_ROOT(victim))
2430 return -EBUSY;
2431 } else if (d_is_dir(victim))
2432 return -EISDIR;
2433 if (IS_DEADDIR(dir))
2434 return -ENOENT;
2435 if (victim->d_flags & DCACHE_NFSFS_RENAMED)
2436 return -EBUSY;
2437 return 0;
2438 }
2439
2440 /* Check whether we can create an object with dentry child in directory
2441 * dir.
2442 * 1. We can't do it if child already exists (open has special treatment for
2443 * this case, but since we are inlined it's OK)
2444 * 2. We can't do it if dir is read-only (done in permission())
2445 * 3. We should have write and exec permissions on dir
2446 * 4. We can't do it if dir is immutable (done in permission())
2447 */
2448 static inline int may_create(struct inode *dir, struct dentry *child)
2449 {
2450 audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE);
2451 if (child->d_inode)
2452 return -EEXIST;
2453 if (IS_DEADDIR(dir))
2454 return -ENOENT;
2455 return inode_permission(dir, MAY_WRITE | MAY_EXEC);
2456 }
2457
2458 /*
2459 * p1 and p2 should be directories on the same fs.
2460 */
2461 struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
2462 {
2463 struct dentry *p;
2464
2465 if (p1 == p2) {
2466 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2467 return NULL;
2468 }
2469
2470 mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
2471
2472 p = d_ancestor(p2, p1);
2473 if (p) {
2474 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
2475 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
2476 return p;
2477 }
2478
2479 p = d_ancestor(p1, p2);
2480 if (p) {
2481 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2482 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
2483 return p;
2484 }
2485
2486 mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2487 mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
2488 return NULL;
2489 }
2490 EXPORT_SYMBOL(lock_rename);
2491
2492 void unlock_rename(struct dentry *p1, struct dentry *p2)
2493 {
2494 mutex_unlock(&p1->d_inode->i_mutex);
2495 if (p1 != p2) {
2496 mutex_unlock(&p2->d_inode->i_mutex);
2497 mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
2498 }
2499 }
2500 EXPORT_SYMBOL(unlock_rename);
2501
2502 int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
2503 bool want_excl)
2504 {
2505 int error = may_create(dir, dentry);
2506 if (error)
2507 return error;
2508
2509 if (!dir->i_op->create)
2510 return -EACCES; /* shouldn't it be ENOSYS? */
2511 mode &= S_IALLUGO;
2512 mode |= S_IFREG;
2513 error = security_inode_create(dir, dentry, mode);
2514 if (error)
2515 return error;
2516 error = dir->i_op->create(dir, dentry, mode, want_excl);
2517 if (!error)
2518 fsnotify_create(dir, dentry);
2519 return error;
2520 }
2521 EXPORT_SYMBOL(vfs_create);
2522
2523 static int may_open(struct path *path, int acc_mode, int flag)
2524 {
2525 struct dentry *dentry = path->dentry;
2526 struct inode *inode = dentry->d_inode;
2527 int error;
2528
2529 /* O_PATH? */
2530 if (!acc_mode)
2531 return 0;
2532
2533 if (!inode)
2534 return -ENOENT;
2535
2536 switch (inode->i_mode & S_IFMT) {
2537 case S_IFLNK:
2538 return -ELOOP;
2539 case S_IFDIR:
2540 if (acc_mode & MAY_WRITE)
2541 return -EISDIR;
2542 break;
2543 case S_IFBLK:
2544 case S_IFCHR:
2545 if (path->mnt->mnt_flags & MNT_NODEV)
2546 return -EACCES;
2547 /*FALLTHRU*/
2548 case S_IFIFO:
2549 case S_IFSOCK:
2550 flag &= ~O_TRUNC;
2551 break;
2552 }
2553
2554 error = inode_permission(inode, acc_mode);
2555 if (error)
2556 return error;
2557
2558 /*
2559 * An append-only file must be opened in append mode for writing.
2560 */
2561 if (IS_APPEND(inode)) {
2562 if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
2563 return -EPERM;
2564 if (flag & O_TRUNC)
2565 return -EPERM;
2566 }
2567
2568 /* O_NOATIME can only be set by the owner or superuser */
2569 if (flag & O_NOATIME && !inode_owner_or_capable(inode))
2570 return -EPERM;
2571
2572 return 0;
2573 }
2574
2575 static int handle_truncate(struct file *filp)
2576 {
2577 struct path *path = &filp->f_path;
2578 struct inode *inode = path->dentry->d_inode;
2579 int error = get_write_access(inode);
2580 if (error)
2581 return error;
2582 /*
2583 * Refuse to truncate files with mandatory locks held on them.
2584 */
2585 error = locks_verify_locked(filp);
2586 if (!error)
2587 error = security_path_truncate(path);
2588 if (!error) {
2589 error = do_truncate(path->dentry, 0,
2590 ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
2591 filp);
2592 }
2593 put_write_access(inode);
2594 return error;
2595 }
2596
2597 static inline int open_to_namei_flags(int flag)
2598 {
2599 if ((flag & O_ACCMODE) == 3)
2600 flag--;
2601 return flag;
2602 }
2603
2604 static int may_o_create(struct path *dir, struct dentry *dentry, umode_t mode)
2605 {
2606 int error = security_path_mknod(dir, dentry, mode, 0);
2607 if (error)
2608 return error;
2609
2610 error = inode_permission(dir->dentry->d_inode, MAY_WRITE | MAY_EXEC);
2611 if (error)
2612 return error;
2613
2614 return security_inode_create(dir->dentry->d_inode, dentry, mode);
2615 }
2616
2617 /*
2618 * Attempt to atomically look up, create and open a file from a negative
2619 * dentry.
2620 *
2621 * Returns 0 if successful. The file will have been created and attached to
2622 * @file by the filesystem calling finish_open().
2623 *
2624 * Returns 1 if the file was looked up only or didn't need creating. The
2625 * caller will need to perform the open themselves. @path will have been
2626 * updated to point to the new dentry. This may be negative.
2627 *
2628 * Returns an error code otherwise.
2629 */
2630 static int atomic_open(struct nameidata *nd, struct dentry *dentry,
2631 struct path *path, struct file *file,
2632 const struct open_flags *op,
2633 bool got_write, bool need_lookup,
2634 int *opened)
2635 {
2636 struct inode *dir = nd->path.dentry->d_inode;
2637 unsigned open_flag = open_to_namei_flags(op->open_flag);
2638 umode_t mode;
2639 int error;
2640 int acc_mode;
2641 int create_error = 0;
2642 struct dentry *const DENTRY_NOT_SET = (void *) -1UL;
2643 bool excl;
2644
2645 BUG_ON(dentry->d_inode);
2646
2647 /* Don't create child dentry for a dead directory. */
2648 if (unlikely(IS_DEADDIR(dir))) {
2649 error = -ENOENT;
2650 goto out;
2651 }
2652
2653 mode = op->mode;
2654 if ((open_flag & O_CREAT) && !IS_POSIXACL(dir))
2655 mode &= ~current_umask();
2656
2657 excl = (open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT);
2658 if (excl)
2659 open_flag &= ~O_TRUNC;
2660
2661 /*
2662 * Checking write permission is tricky, bacuse we don't know if we are
2663 * going to actually need it: O_CREAT opens should work as long as the
2664 * file exists. But checking existence breaks atomicity. The trick is
2665 * to check access and if not granted clear O_CREAT from the flags.
2666 *
2667 * Another problem is returing the "right" error value (e.g. for an
2668 * O_EXCL open we want to return EEXIST not EROFS).
2669 */
2670 if (((open_flag & (O_CREAT | O_TRUNC)) ||
2671 (open_flag & O_ACCMODE) != O_RDONLY) && unlikely(!got_write)) {
2672 if (!(open_flag & O_CREAT)) {
2673 /*
2674 * No O_CREATE -> atomicity not a requirement -> fall
2675 * back to lookup + open
2676 */
2677 goto no_open;
2678 } else if (open_flag & (O_EXCL | O_TRUNC)) {
2679 /* Fall back and fail with the right error */
2680 create_error = -EROFS;
2681 goto no_open;
2682 } else {
2683 /* No side effects, safe to clear O_CREAT */
2684 create_error = -EROFS;
2685 open_flag &= ~O_CREAT;
2686 }
2687 }
2688
2689 if (open_flag & O_CREAT) {
2690 error = may_o_create(&nd->path, dentry, mode);
2691 if (error) {
2692 create_error = error;
2693 if (open_flag & O_EXCL)
2694 goto no_open;
2695 open_flag &= ~O_CREAT;
2696 }
2697 }
2698
2699 if (nd->flags & LOOKUP_DIRECTORY)
2700 open_flag |= O_DIRECTORY;
2701
2702 file->f_path.dentry = DENTRY_NOT_SET;
2703 file->f_path.mnt = nd->path.mnt;
2704 error = dir->i_op->atomic_open(dir, dentry, file, open_flag, mode,
2705 opened);
2706 if (error < 0) {
2707 if (create_error && error == -ENOENT)
2708 error = create_error;
2709 goto out;
2710 }
2711
2712 if (error) { /* returned 1, that is */
2713 if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) {
2714 error = -EIO;
2715 goto out;
2716 }
2717 if (file->f_path.dentry) {
2718 dput(dentry);
2719 dentry = file->f_path.dentry;
2720 }
2721 if (*opened & FILE_CREATED)
2722 fsnotify_create(dir, dentry);
2723 if (!dentry->d_inode) {
2724 WARN_ON(*opened & FILE_CREATED);
2725 if (create_error) {
2726 error = create_error;
2727 goto out;
2728 }
2729 } else {
2730 if (excl && !(*opened & FILE_CREATED)) {
2731 error = -EEXIST;
2732 goto out;
2733 }
2734 }
2735 goto looked_up;
2736 }
2737
2738 /*
2739 * We didn't have the inode before the open, so check open permission
2740 * here.
2741 */
2742 acc_mode = op->acc_mode;
2743 if (*opened & FILE_CREATED) {
2744 WARN_ON(!(open_flag & O_CREAT));
2745 fsnotify_create(dir, dentry);
2746 acc_mode = MAY_OPEN;
2747 }
2748 error = may_open(&file->f_path, acc_mode, open_flag);
2749 if (error)
2750 fput(file);
2751
2752 out:
2753 dput(dentry);
2754 return error;
2755
2756 no_open:
2757 if (need_lookup) {
2758 dentry = lookup_real(dir, dentry, nd->flags);
2759 if (IS_ERR(dentry))
2760 return PTR_ERR(dentry);
2761
2762 if (create_error) {
2763 int open_flag = op->open_flag;
2764
2765 error = create_error;
2766 if ((open_flag & O_EXCL)) {
2767 if (!dentry->d_inode)
2768 goto out;
2769 } else if (!dentry->d_inode) {
2770 goto out;
2771 } else if ((open_flag & O_TRUNC) &&
2772 S_ISREG(dentry->d_inode->i_mode)) {
2773 goto out;
2774 }
2775 /* will fail later, go on to get the right error */
2776 }
2777 }
2778 looked_up:
2779 path->dentry = dentry;
2780 path->mnt = nd->path.mnt;
2781 return 1;
2782 }
2783
2784 /*
2785 * Look up and maybe create and open the last component.
2786 *
2787 * Must be called with i_mutex held on parent.
2788 *
2789 * Returns 0 if the file was successfully atomically created (if necessary) and
2790 * opened. In this case the file will be returned attached to @file.
2791 *
2792 * Returns 1 if the file was not completely opened at this time, though lookups
2793 * and creations will have been performed and the dentry returned in @path will
2794 * be positive upon return if O_CREAT was specified. If O_CREAT wasn't
2795 * specified then a negative dentry may be returned.
2796 *
2797 * An error code is returned otherwise.
2798 *
2799 * FILE_CREATE will be set in @*opened if the dentry was created and will be
2800 * cleared otherwise prior to returning.
2801 */
2802 static int lookup_open(struct nameidata *nd, struct path *path,
2803 struct file *file,
2804 const struct open_flags *op,
2805 bool got_write, int *opened)
2806 {
2807 struct dentry *dir = nd->path.dentry;
2808 struct inode *dir_inode = dir->d_inode;
2809 struct dentry *dentry;
2810 int error;
2811 bool need_lookup;
2812
2813 *opened &= ~FILE_CREATED;
2814 dentry = lookup_dcache(&nd->last, dir, nd->flags, &need_lookup);
2815 if (IS_ERR(dentry))
2816 return PTR_ERR(dentry);
2817
2818 /* Cached positive dentry: will open in f_op->open */
2819 if (!need_lookup && dentry->d_inode)
2820 goto out_no_open;
2821
2822 if ((nd->flags & LOOKUP_OPEN) && dir_inode->i_op->atomic_open) {
2823 return atomic_open(nd, dentry, path, file, op, got_write,
2824 need_lookup, opened);
2825 }
2826
2827 if (need_lookup) {
2828 BUG_ON(dentry->d_inode);
2829
2830 dentry = lookup_real(dir_inode, dentry, nd->flags);
2831 if (IS_ERR(dentry))
2832 return PTR_ERR(dentry);
2833 }
2834
2835 /* Negative dentry, just create the file */
2836 if (!dentry->d_inode && (op->open_flag & O_CREAT)) {
2837 umode_t mode = op->mode;
2838 if (!IS_POSIXACL(dir->d_inode))
2839 mode &= ~current_umask();
2840 /*
2841 * This write is needed to ensure that a
2842 * rw->ro transition does not occur between
2843 * the time when the file is created and when
2844 * a permanent write count is taken through
2845 * the 'struct file' in finish_open().
2846 */
2847 if (!got_write) {
2848 error = -EROFS;
2849 goto out_dput;
2850 }
2851 *opened |= FILE_CREATED;
2852 error = security_path_mknod(&nd->path, dentry, mode, 0);
2853 if (error)
2854 goto out_dput;
2855 error = vfs_create(dir->d_inode, dentry, mode,
2856 nd->flags & LOOKUP_EXCL);
2857 if (error)
2858 goto out_dput;
2859 }
2860 out_no_open:
2861 path->dentry = dentry;
2862 path->mnt = nd->path.mnt;
2863 return 1;
2864
2865 out_dput:
2866 dput(dentry);
2867 return error;
2868 }
2869
2870 /*
2871 * Handle the last step of open()
2872 */
2873 static int do_last(struct nameidata *nd, struct path *path,
2874 struct file *file, const struct open_flags *op,
2875 int *opened, struct filename *name)
2876 {
2877 struct dentry *dir = nd->path.dentry;
2878 int open_flag = op->open_flag;
2879 bool will_truncate = (open_flag & O_TRUNC) != 0;
2880 bool got_write = false;
2881 int acc_mode = op->acc_mode;
2882 struct inode *inode;
2883 bool symlink_ok = false;
2884 struct path save_parent = { .dentry = NULL, .mnt = NULL };
2885 bool retried = false;
2886 int error;
2887
2888 nd->flags &= ~LOOKUP_PARENT;
2889 nd->flags |= op->intent;
2890
2891 if (nd->last_type != LAST_NORM) {
2892 error = handle_dots(nd, nd->last_type);
2893 if (error)
2894 return error;
2895 goto finish_open;
2896 }
2897
2898 if (!(open_flag & O_CREAT)) {
2899 if (nd->last.name[nd->last.len])
2900 nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
2901 if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW))
2902 symlink_ok = true;
2903 /* we _can_ be in RCU mode here */
2904 error = lookup_fast(nd, path, &inode);
2905 if (likely(!error))
2906 goto finish_lookup;
2907
2908 if (error < 0)
2909 goto out;
2910
2911 BUG_ON(nd->inode != dir->d_inode);
2912 } else {
2913 /* create side of things */
2914 /*
2915 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED
2916 * has been cleared when we got to the last component we are
2917 * about to look up
2918 */
2919 error = complete_walk(nd);
2920 if (error)
2921 return error;
2922
2923 audit_inode(name, dir, LOOKUP_PARENT);
2924 error = -EISDIR;
2925 /* trailing slashes? */
2926 if (nd->last.name[nd->last.len])
2927 goto out;
2928 }
2929
2930 retry_lookup:
2931 if (op->open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
2932 error = mnt_want_write(nd->path.mnt);
2933 if (!error)
2934 got_write = true;
2935 /*
2936 * do _not_ fail yet - we might not need that or fail with
2937 * a different error; let lookup_open() decide; we'll be
2938 * dropping this one anyway.
2939 */
2940 }
2941 mutex_lock(&dir->d_inode->i_mutex);
2942 error = lookup_open(nd, path, file, op, got_write, opened);
2943 mutex_unlock(&dir->d_inode->i_mutex);
2944
2945 if (error <= 0) {
2946 if (error)
2947 goto out;
2948
2949 if ((*opened & FILE_CREATED) ||
2950 !S_ISREG(file_inode(file)->i_mode))
2951 will_truncate = false;
2952
2953 audit_inode(name, file->f_path.dentry, 0);
2954 goto opened;
2955 }
2956
2957 if (*opened & FILE_CREATED) {
2958 /* Don't check for write permission, don't truncate */
2959 open_flag &= ~O_TRUNC;
2960 will_truncate = false;
2961 acc_mode = MAY_OPEN;
2962 path_to_nameidata(path, nd);
2963 goto finish_open_created;
2964 }
2965
2966 /*
2967 * create/update audit record if it already exists.
2968 */
2969 if (d_is_positive(path->dentry))
2970 audit_inode(name, path->dentry, 0);
2971
2972 /*
2973 * If atomic_open() acquired write access it is dropped now due to
2974 * possible mount and symlink following (this might be optimized away if
2975 * necessary...)
2976 */
2977 if (got_write) {
2978 mnt_drop_write(nd->path.mnt);
2979 got_write = false;
2980 }
2981
2982 error = -EEXIST;
2983 if ((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT))
2984 goto exit_dput;
2985
2986 error = follow_managed(path, nd->flags);
2987 if (error < 0)
2988 goto exit_dput;
2989
2990 if (error)
2991 nd->flags |= LOOKUP_JUMPED;
2992
2993 BUG_ON(nd->flags & LOOKUP_RCU);
2994 inode = path->dentry->d_inode;
2995 finish_lookup:
2996 /* we _can_ be in RCU mode here */
2997 error = -ENOENT;
2998 if (!inode || d_is_negative(path->dentry)) {
2999 path_to_nameidata(path, nd);
3000 goto out;
3001 }
3002
3003 if (should_follow_link(path->dentry, !symlink_ok)) {
3004 if (nd->flags & LOOKUP_RCU) {
3005 if (unlikely(unlazy_walk(nd, path->dentry))) {
3006 error = -ECHILD;
3007 goto out;
3008 }
3009 }
3010 BUG_ON(inode != path->dentry->d_inode);
3011 return 1;
3012 }
3013
3014 if ((nd->flags & LOOKUP_RCU) || nd->path.mnt != path->mnt) {
3015 path_to_nameidata(path, nd);
3016 } else {
3017 save_parent.dentry = nd->path.dentry;
3018 save_parent.mnt = mntget(path->mnt);
3019 nd->path.dentry = path->dentry;
3020
3021 }
3022 nd->inode = inode;
3023 /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */
3024 finish_open:
3025 error = complete_walk(nd);
3026 if (error) {
3027 path_put(&save_parent);
3028 return error;
3029 }
3030 audit_inode(name, nd->path.dentry, 0);
3031 error = -EISDIR;
3032 if ((open_flag & O_CREAT) && d_is_dir(nd->path.dentry))
3033 goto out;
3034 error = -ENOTDIR;
3035 if ((nd->flags & LOOKUP_DIRECTORY) && !d_can_lookup(nd->path.dentry))
3036 goto out;
3037 if (!S_ISREG(nd->inode->i_mode))
3038 will_truncate = false;
3039
3040 if (will_truncate) {
3041 error = mnt_want_write(nd->path.mnt);
3042 if (error)
3043 goto out;
3044 got_write = true;
3045 }
3046 finish_open_created:
3047 error = may_open(&nd->path, acc_mode, open_flag);
3048 if (error)
3049 goto out;
3050 file->f_path.mnt = nd->path.mnt;
3051 error = finish_open(file, nd->path.dentry, NULL, opened);
3052 if (error) {
3053 if (error == -EOPENSTALE)
3054 goto stale_open;
3055 goto out;
3056 }
3057 opened:
3058 error = open_check_o_direct(file);
3059 if (error)
3060 goto exit_fput;
3061 error = ima_file_check(file, op->acc_mode);
3062 if (error)
3063 goto exit_fput;
3064
3065 if (will_truncate) {
3066 error = handle_truncate(file);
3067 if (error)
3068 goto exit_fput;
3069 }
3070 out:
3071 if (got_write)
3072 mnt_drop_write(nd->path.mnt);
3073 path_put(&save_parent);
3074 terminate_walk(nd);
3075 return error;
3076
3077 exit_dput:
3078 path_put_conditional(path, nd);
3079 goto out;
3080 exit_fput:
3081 fput(file);
3082 goto out;
3083
3084 stale_open:
3085 /* If no saved parent or already retried then can't retry */
3086 if (!save_parent.dentry || retried)
3087 goto out;
3088
3089 BUG_ON(save_parent.dentry != dir);
3090 path_put(&nd->path);
3091 nd->path = save_parent;
3092 nd->inode = dir->d_inode;
3093 save_parent.mnt = NULL;
3094 save_parent.dentry = NULL;
3095 if (got_write) {
3096 mnt_drop_write(nd->path.mnt);
3097 got_write = false;
3098 }
3099 retried = true;
3100 goto retry_lookup;
3101 }
3102
3103 static int do_tmpfile(int dfd, struct filename *pathname,
3104 struct nameidata *nd, int flags,
3105 const struct open_flags *op,
3106 struct file *file, int *opened)
3107 {
3108 static const struct qstr name = QSTR_INIT("/", 1);
3109 struct dentry *dentry, *child;
3110 struct inode *dir;
3111 int error = path_lookupat(dfd, pathname->name,
3112 flags | LOOKUP_DIRECTORY, nd);
3113 if (unlikely(error))
3114 return error;
3115 error = mnt_want_write(nd->path.mnt);
3116 if (unlikely(error))
3117 goto out;
3118 /* we want directory to be writable */
3119 error = inode_permission(nd->inode, MAY_WRITE | MAY_EXEC);
3120 if (error)
3121 goto out2;
3122 dentry = nd->path.dentry;
3123 dir = dentry->d_inode;
3124 if (!dir->i_op->tmpfile) {
3125 error = -EOPNOTSUPP;
3126 goto out2;
3127 }
3128 child = d_alloc(dentry, &name);
3129 if (unlikely(!child)) {
3130 error = -ENOMEM;
3131 goto out2;
3132 }
3133 nd->flags &= ~LOOKUP_DIRECTORY;
3134 nd->flags |= op->intent;
3135 dput(nd->path.dentry);
3136 nd->path.dentry = child;
3137 error = dir->i_op->tmpfile(dir, nd->path.dentry, op->mode);
3138 if (error)
3139 goto out2;
3140 audit_inode(pathname, nd->path.dentry, 0);
3141 error = may_open(&nd->path, op->acc_mode, op->open_flag);
3142 if (error)
3143 goto out2;
3144 file->f_path.mnt = nd->path.mnt;
3145 error = finish_open(file, nd->path.dentry, NULL, opened);
3146 if (error)
3147 goto out2;
3148 error = open_check_o_direct(file);
3149 if (error) {
3150 fput(file);
3151 } else if (!(op->open_flag & O_EXCL)) {
3152 struct inode *inode = file_inode(file);
3153 spin_lock(&inode->i_lock);
3154 inode->i_state |= I_LINKABLE;
3155 spin_unlock(&inode->i_lock);
3156 }
3157 out2:
3158 mnt_drop_write(nd->path.mnt);
3159 out:
3160 path_put(&nd->path);
3161 return error;
3162 }
3163
3164 static struct file *path_openat(int dfd, struct filename *pathname,
3165 struct nameidata *nd, const struct open_flags *op, int flags)
3166 {
3167 struct file *base = NULL;
3168 struct file *file;
3169 struct path path;
3170 int opened = 0;
3171 int error;
3172
3173 file = get_empty_filp();
3174 if (IS_ERR(file))
3175 return file;
3176
3177 file->f_flags = op->open_flag;
3178
3179 if (unlikely(file->f_flags & __O_TMPFILE)) {
3180 error = do_tmpfile(dfd, pathname, nd, flags, op, file, &opened);
3181 goto out;
3182 }
3183
3184 error = path_init(dfd, pathname->name, flags | LOOKUP_PARENT, nd, &base);
3185 if (unlikely(error))
3186 goto out;
3187
3188 current->total_link_count = 0;
3189 error = link_path_walk(pathname->name, nd);
3190 if (unlikely(error))
3191 goto out;
3192
3193 error = do_last(nd, &path, file, op, &opened, pathname);
3194 while (unlikely(error > 0)) { /* trailing symlink */
3195 struct path link = path;
3196 void *cookie;
3197 if (!(nd->flags & LOOKUP_FOLLOW)) {
3198 path_put_conditional(&path, nd);
3199 path_put(&nd->path);
3200 error = -ELOOP;
3201 break;
3202 }
3203 error = may_follow_link(&link, nd);
3204 if (unlikely(error))
3205 break;
3206 nd->flags |= LOOKUP_PARENT;
3207 nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
3208 error = follow_link(&link, nd, &cookie);
3209 if (unlikely(error))
3210 break;
3211 error = do_last(nd, &path, file, op, &opened, pathname);
3212 put_link(nd, &link, cookie);
3213 }
3214 out:
3215 if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT))
3216 path_put(&nd->root);
3217 if (base)
3218 fput(base);
3219 if (!(opened & FILE_OPENED)) {
3220 BUG_ON(!error);
3221 put_filp(file);
3222 }
3223 if (unlikely(error)) {
3224 if (error == -EOPENSTALE) {
3225 if (flags & LOOKUP_RCU)
3226 error = -ECHILD;
3227 else
3228 error = -ESTALE;
3229 }
3230 file = ERR_PTR(error);
3231 }
3232 return file;
3233 }
3234
3235 struct file *do_filp_open(int dfd, struct filename *pathname,
3236 const struct open_flags *op)
3237 {
3238 struct nameidata nd;
3239 int flags = op->lookup_flags;
3240 struct file *filp;
3241
3242 filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_RCU);
3243 if (unlikely(filp == ERR_PTR(-ECHILD)))
3244 filp = path_openat(dfd, pathname, &nd, op, flags);
3245 if (unlikely(filp == ERR_PTR(-ESTALE)))
3246 filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_REVAL);
3247 return filp;
3248 }
3249
3250 struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
3251 const char *name, const struct open_flags *op)
3252 {
3253 struct nameidata nd;
3254 struct file *file;
3255 struct filename filename = { .name = name };
3256 int flags = op->lookup_flags | LOOKUP_ROOT;
3257
3258 nd.root.mnt = mnt;
3259 nd.root.dentry = dentry;
3260
3261 if (d_is_symlink(dentry) && op->intent & LOOKUP_OPEN)
3262 return ERR_PTR(-ELOOP);
3263
3264 file = path_openat(-1, &filename, &nd, op, flags | LOOKUP_RCU);
3265 if (unlikely(file == ERR_PTR(-ECHILD)))
3266 file = path_openat(-1, &filename, &nd, op, flags);
3267 if (unlikely(file == ERR_PTR(-ESTALE)))
3268 file = path_openat(-1, &filename, &nd, op, flags | LOOKUP_REVAL);
3269 return file;
3270 }
3271
3272 struct dentry *kern_path_create(int dfd, const char *pathname,
3273 struct path *path, unsigned int lookup_flags)
3274 {
3275 struct dentry *dentry = ERR_PTR(-EEXIST);
3276 struct nameidata nd;
3277 int err2;
3278 int error;
3279 bool is_dir = (lookup_flags & LOOKUP_DIRECTORY);
3280
3281 /*
3282 * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any
3283 * other flags passed in are ignored!
3284 */
3285 lookup_flags &= LOOKUP_REVAL;
3286
3287 error = do_path_lookup(dfd, pathname, LOOKUP_PARENT|lookup_flags, &nd);
3288 if (error)
3289 return ERR_PTR(error);
3290
3291 /*
3292 * Yucky last component or no last component at all?
3293 * (foo/., foo/.., /////)
3294 */
3295 if (nd.last_type != LAST_NORM)
3296 goto out;
3297 nd.flags &= ~LOOKUP_PARENT;
3298 nd.flags |= LOOKUP_CREATE | LOOKUP_EXCL;
3299
3300 /* don't fail immediately if it's r/o, at least try to report other errors */
3301 err2 = mnt_want_write(nd.path.mnt);
3302 /*
3303 * Do the final lookup.
3304 */
3305 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
3306 dentry = lookup_hash(&nd);
3307 if (IS_ERR(dentry))
3308 goto unlock;
3309
3310 error = -EEXIST;
3311 if (d_is_positive(dentry))
3312 goto fail;
3313
3314 /*
3315 * Special case - lookup gave negative, but... we had foo/bar/
3316 * From the vfs_mknod() POV we just have a negative dentry -
3317 * all is fine. Let's be bastards - you had / on the end, you've
3318 * been asking for (non-existent) directory. -ENOENT for you.
3319 */
3320 if (unlikely(!is_dir && nd.last.name[nd.last.len])) {
3321 error = -ENOENT;
3322 goto fail;
3323 }
3324 if (unlikely(err2)) {
3325 error = err2;
3326 goto fail;
3327 }
3328 *path = nd.path;
3329 return dentry;
3330 fail:
3331 dput(dentry);
3332 dentry = ERR_PTR(error);
3333 unlock:
3334 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
3335 if (!err2)
3336 mnt_drop_write(nd.path.mnt);
3337 out:
3338 path_put(&nd.path);
3339 return dentry;
3340 }
3341 EXPORT_SYMBOL(kern_path_create);
3342
3343 void done_path_create(struct path *path, struct dentry *dentry)
3344 {
3345 dput(dentry);
3346 mutex_unlock(&path->dentry->d_inode->i_mutex);
3347 mnt_drop_write(path->mnt);
3348 path_put(path);
3349 }
3350 EXPORT_SYMBOL(done_path_create);
3351
3352 struct dentry *user_path_create(int dfd, const char __user *pathname,
3353 struct path *path, unsigned int lookup_flags)
3354 {
3355 struct filename *tmp = getname(pathname);
3356 struct dentry *res;
3357 if (IS_ERR(tmp))
3358 return ERR_CAST(tmp);
3359 res = kern_path_create(dfd, tmp->name, path, lookup_flags);
3360 putname(tmp);
3361 return res;
3362 }
3363 EXPORT_SYMBOL(user_path_create);
3364
3365 int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
3366 {
3367 int error = may_create(dir, dentry);
3368
3369 if (error)
3370 return error;
3371
3372 if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
3373 return -EPERM;
3374
3375 if (!dir->i_op->mknod)
3376 return -EPERM;
3377
3378 error = devcgroup_inode_mknod(mode, dev);
3379 if (error)
3380 return error;
3381
3382 error = security_inode_mknod(dir, dentry, mode, dev);
3383 if (error)
3384 return error;
3385
3386 error = dir->i_op->mknod(dir, dentry, mode, dev);
3387 if (!error)
3388 fsnotify_create(dir, dentry);
3389 return error;
3390 }
3391 EXPORT_SYMBOL(vfs_mknod);
3392
3393 static int may_mknod(umode_t mode)
3394 {
3395 switch (mode & S_IFMT) {
3396 case S_IFREG:
3397 case S_IFCHR:
3398 case S_IFBLK:
3399 case S_IFIFO:
3400 case S_IFSOCK:
3401 case 0: /* zero mode translates to S_IFREG */
3402 return 0;
3403 case S_IFDIR:
3404 return -EPERM;
3405 default:
3406 return -EINVAL;
3407 }
3408 }
3409
3410 SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,
3411 unsigned, dev)
3412 {
3413 struct dentry *dentry;
3414 struct path path;
3415 int error;
3416 unsigned int lookup_flags = 0;
3417
3418 error = may_mknod(mode);
3419 if (error)
3420 return error;
3421 retry:
3422 dentry = user_path_create(dfd, filename, &path, lookup_flags);
3423 if (IS_ERR(dentry))
3424 return PTR_ERR(dentry);
3425
3426 if (!IS_POSIXACL(path.dentry->d_inode))
3427 mode &= ~current_umask();
3428 error = security_path_mknod(&path, dentry, mode, dev);
3429 if (error)
3430 goto out;
3431 switch (mode & S_IFMT) {
3432 case 0: case S_IFREG:
3433 error = vfs_create(path.dentry->d_inode,dentry,mode,true);
3434 break;
3435 case S_IFCHR: case S_IFBLK:
3436 error = vfs_mknod(path.dentry->d_inode,dentry,mode,
3437 new_decode_dev(dev));
3438 break;
3439 case S_IFIFO: case S_IFSOCK:
3440 error = vfs_mknod(path.dentry->d_inode,dentry,mode,0);
3441 break;
3442 }
3443 out:
3444 done_path_create(&path, dentry);
3445 if (retry_estale(error, lookup_flags)) {
3446 lookup_flags |= LOOKUP_REVAL;
3447 goto retry;
3448 }
3449 return error;
3450 }
3451
3452 SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev)
3453 {
3454 return sys_mknodat(AT_FDCWD, filename, mode, dev);
3455 }
3456
3457 int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
3458 {
3459 int error = may_create(dir, dentry);
3460 unsigned max_links = dir->i_sb->s_max_links;
3461
3462 if (error)
3463 return error;
3464
3465 if (!dir->i_op->mkdir)
3466 return -EPERM;
3467
3468 mode &= (S_IRWXUGO|S_ISVTX);
3469 error = security_inode_mkdir(dir, dentry, mode);
3470 if (error)
3471 return error;
3472
3473 if (max_links && dir->i_nlink >= max_links)
3474 return -EMLINK;
3475
3476 error = dir->i_op->mkdir(dir, dentry, mode);
3477 if (!error)
3478 fsnotify_mkdir(dir, dentry);
3479 return error;
3480 }
3481 EXPORT_SYMBOL(vfs_mkdir);
3482
3483 SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
3484 {
3485 struct dentry *dentry;
3486 struct path path;
3487 int error;
3488 unsigned int lookup_flags = LOOKUP_DIRECTORY;
3489
3490 retry:
3491 dentry = user_path_create(dfd, pathname, &path, lookup_flags);
3492 if (IS_ERR(dentry))
3493 return PTR_ERR(dentry);
3494
3495 if (!IS_POSIXACL(path.dentry->d_inode))
3496 mode &= ~current_umask();
3497 error = security_path_mkdir(&path, dentry, mode);
3498 if (!error)
3499 error = vfs_mkdir(path.dentry->d_inode, dentry, mode);
3500 done_path_create(&path, dentry);
3501 if (retry_estale(error, lookup_flags)) {
3502 lookup_flags |= LOOKUP_REVAL;
3503 goto retry;
3504 }
3505 return error;
3506 }
3507
3508 SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode)
3509 {
3510 return sys_mkdirat(AT_FDCWD, pathname, mode);
3511 }
3512
3513 /*
3514 * The dentry_unhash() helper will try to drop the dentry early: we
3515 * should have a usage count of 1 if we're the only user of this
3516 * dentry, and if that is true (possibly after pruning the dcache),
3517 * then we drop the dentry now.
3518 *
3519 * A low-level filesystem can, if it choses, legally
3520 * do a
3521 *
3522 * if (!d_unhashed(dentry))
3523 * return -EBUSY;
3524 *
3525 * if it cannot handle the case of removing a directory
3526 * that is still in use by something else..
3527 */
3528 void dentry_unhash(struct dentry *dentry)
3529 {
3530 shrink_dcache_parent(dentry);
3531 spin_lock(&dentry->d_lock);
3532 if (dentry->d_lockref.count == 1)
3533 __d_drop(dentry);
3534 spin_unlock(&dentry->d_lock);
3535 }
3536 EXPORT_SYMBOL(dentry_unhash);
3537
3538 int vfs_rmdir(struct inode *dir, struct dentry *dentry)
3539 {
3540 int error = may_delete(dir, dentry, 1);
3541
3542 if (error)
3543 return error;
3544
3545 if (!dir->i_op->rmdir)
3546 return -EPERM;
3547
3548 dget(dentry);
3549 mutex_lock(&dentry->d_inode->i_mutex);
3550
3551 error = -EBUSY;
3552 if (d_mountpoint(dentry))
3553 goto out;
3554
3555 error = security_inode_rmdir(dir, dentry);
3556 if (error)
3557 goto out;
3558
3559 shrink_dcache_parent(dentry);
3560 error = dir->i_op->rmdir(dir, dentry);
3561 if (error)
3562 goto out;
3563
3564 dentry->d_inode->i_flags |= S_DEAD;
3565 dont_mount(dentry);
3566
3567 out:
3568 mutex_unlock(&dentry->d_inode->i_mutex);
3569 dput(dentry);
3570 if (!error)
3571 d_delete(dentry);
3572 return error;
3573 }
3574 EXPORT_SYMBOL(vfs_rmdir);
3575
3576 static long do_rmdir(int dfd, const char __user *pathname)
3577 {
3578 int error = 0;
3579 struct filename *name;
3580 struct dentry *dentry;
3581 struct nameidata nd;
3582 unsigned int lookup_flags = 0;
3583 retry:
3584 name = user_path_parent(dfd, pathname, &nd, lookup_flags);
3585 if (IS_ERR(name))
3586 return PTR_ERR(name);
3587
3588 switch(nd.last_type) {
3589 case LAST_DOTDOT:
3590 error = -ENOTEMPTY;
3591 goto exit1;
3592 case LAST_DOT:
3593 error = -EINVAL;
3594 goto exit1;
3595 case LAST_ROOT:
3596 error = -EBUSY;
3597 goto exit1;
3598 }
3599
3600 nd.flags &= ~LOOKUP_PARENT;
3601 error = mnt_want_write(nd.path.mnt);
3602 if (error)
3603 goto exit1;
3604
3605 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
3606 dentry = lookup_hash(&nd);
3607 error = PTR_ERR(dentry);
3608 if (IS_ERR(dentry))
3609 goto exit2;
3610 if (!dentry->d_inode) {
3611 error = -ENOENT;
3612 goto exit3;
3613 }
3614 error = security_path_rmdir(&nd.path, dentry);
3615 if (error)
3616 goto exit3;
3617 error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
3618 exit3:
3619 dput(dentry);
3620 exit2:
3621 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
3622 mnt_drop_write(nd.path.mnt);
3623 exit1:
3624 path_put(&nd.path);
3625 putname(name);
3626 if (retry_estale(error, lookup_flags)) {
3627 lookup_flags |= LOOKUP_REVAL;
3628 goto retry;
3629 }
3630 return error;
3631 }
3632
3633 SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
3634 {
3635 return do_rmdir(AT_FDCWD, pathname);
3636 }
3637
3638 /**
3639 * vfs_unlink - unlink a filesystem object
3640 * @dir: parent directory
3641 * @dentry: victim
3642 * @delegated_inode: returns victim inode, if the inode is delegated.
3643 *
3644 * The caller must hold dir->i_mutex.
3645 *
3646 * If vfs_unlink discovers a delegation, it will return -EWOULDBLOCK and
3647 * return a reference to the inode in delegated_inode. The caller
3648 * should then break the delegation on that inode and retry. Because
3649 * breaking a delegation may take a long time, the caller should drop
3650 * dir->i_mutex before doing so.
3651 *
3652 * Alternatively, a caller may pass NULL for delegated_inode. This may
3653 * be appropriate for callers that expect the underlying filesystem not
3654 * to be NFS exported.
3655 */
3656 int vfs_unlink(struct inode *dir, struct dentry *dentry, struct inode **delegated_inode)
3657 {
3658 struct inode *target = dentry->d_inode;
3659 int error = may_delete(dir, dentry, 0);
3660
3661 if (error)
3662 return error;
3663
3664 if (!dir->i_op->unlink)
3665 return -EPERM;
3666
3667 mutex_lock(&target->i_mutex);
3668 if (d_mountpoint(dentry))
3669 error = -EBUSY;
3670 else {
3671 error = security_inode_unlink(dir, dentry);
3672 if (!error) {
3673 error = try_break_deleg(target, delegated_inode);
3674 if (error)
3675 goto out;
3676 error = dir->i_op->unlink(dir, dentry);
3677 if (!error)
3678 dont_mount(dentry);
3679 }
3680 }
3681 out:
3682 mutex_unlock(&target->i_mutex);
3683
3684 /* We don't d_delete() NFS sillyrenamed files--they still exist. */
3685 if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
3686 fsnotify_link_count(target);
3687 d_delete(dentry);
3688 }
3689
3690 return error;
3691 }
3692 EXPORT_SYMBOL(vfs_unlink);
3693
3694 /*
3695 * Make sure that the actual truncation of the file will occur outside its
3696 * directory's i_mutex. Truncate can take a long time if there is a lot of
3697 * writeout happening, and we don't want to prevent access to the directory
3698 * while waiting on the I/O.
3699 */
3700 static long do_unlinkat(int dfd, const char __user *pathname)
3701 {
3702 int error;
3703 struct filename *name;
3704 struct dentry *dentry;
3705 struct nameidata nd;
3706 struct inode *inode = NULL;
3707 struct inode *delegated_inode = NULL;
3708 unsigned int lookup_flags = 0;
3709 retry:
3710 name = user_path_parent(dfd, pathname, &nd, lookup_flags);
3711 if (IS_ERR(name))
3712 return PTR_ERR(name);
3713
3714 error = -EISDIR;
3715 if (nd.last_type != LAST_NORM)
3716 goto exit1;
3717
3718 nd.flags &= ~LOOKUP_PARENT;
3719 error = mnt_want_write(nd.path.mnt);
3720 if (error)
3721 goto exit1;
3722 retry_deleg:
3723 mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
3724 dentry = lookup_hash(&nd);
3725 error = PTR_ERR(dentry);
3726 if (!IS_ERR(dentry)) {
3727 /* Why not before? Because we want correct error value */
3728 if (nd.last.name[nd.last.len])
3729 goto slashes;
3730 inode = dentry->d_inode;
3731 if (d_is_negative(dentry))
3732 goto slashes;
3733 ihold(inode);
3734 error = security_path_unlink(&nd.path, dentry);
3735 if (error)
3736 goto exit2;
3737 error = vfs_unlink(nd.path.dentry->d_inode, dentry, &delegated_inode);
3738 exit2:
3739 dput(dentry);
3740 }
3741 mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
3742 if (inode)
3743 iput(inode); /* truncate the inode here */
3744 inode = NULL;
3745 if (delegated_inode) {
3746 error = break_deleg_wait(&delegated_inode);
3747 if (!error)
3748 goto retry_deleg;
3749 }
3750 mnt_drop_write(nd.path.mnt);
3751 exit1:
3752 path_put(&nd.path);
3753 putname(name);
3754 if (retry_estale(error, lookup_flags)) {
3755 lookup_flags |= LOOKUP_REVAL;
3756 inode = NULL;
3757 goto retry;
3758 }
3759 return error;
3760
3761 slashes:
3762 if (d_is_negative(dentry))
3763 error = -ENOENT;
3764 else if (d_is_dir(dentry))
3765 error = -EISDIR;
3766 else
3767 error = -ENOTDIR;
3768 goto exit2;
3769 }
3770
3771 SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
3772 {
3773 if ((flag & ~AT_REMOVEDIR) != 0)
3774 return -EINVAL;
3775
3776 if (flag & AT_REMOVEDIR)
3777 return do_rmdir(dfd, pathname);
3778
3779 return do_unlinkat(dfd, pathname);
3780 }
3781
3782 SYSCALL_DEFINE1(unlink, const char __user *, pathname)
3783 {
3784 return do_unlinkat(AT_FDCWD, pathname);
3785 }
3786
3787 int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
3788 {
3789 int error = may_create(dir, dentry);
3790
3791 if (error)
3792 return error;
3793
3794 if (!dir->i_op->symlink)
3795 return -EPERM;
3796
3797 error = security_inode_symlink(dir, dentry, oldname);
3798 if (error)
3799 return error;
3800
3801 error = dir->i_op->symlink(dir, dentry, oldname);
3802 if (!error)
3803 fsnotify_create(dir, dentry);
3804 return error;
3805 }
3806 EXPORT_SYMBOL(vfs_symlink);
3807
3808 SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
3809 int, newdfd, const char __user *, newname)
3810 {
3811 int error;
3812 struct filename *from;
3813 struct dentry *dentry;
3814 struct path path;
3815 unsigned int lookup_flags = 0;
3816
3817 from = getname(oldname);
3818 if (IS_ERR(from))
3819 return PTR_ERR(from);
3820 retry:
3821 dentry = user_path_create(newdfd, newname, &path, lookup_flags);
3822 error = PTR_ERR(dentry);
3823 if (IS_ERR(dentry))
3824 goto out_putname;
3825
3826 error = security_path_symlink(&path, dentry, from->name);
3827 if (!error)
3828 error = vfs_symlink(path.dentry->d_inode, dentry, from->name);
3829 done_path_create(&path, dentry);
3830 if (retry_estale(error, lookup_flags)) {
3831 lookup_flags |= LOOKUP_REVAL;
3832 goto retry;
3833 }
3834 out_putname:
3835 putname(from);
3836 return error;
3837 }
3838
3839 SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
3840 {
3841 return sys_symlinkat(oldname, AT_FDCWD, newname);
3842 }
3843
3844 /**
3845 * vfs_link - create a new link
3846 * @old_dentry: object to be linked
3847 * @dir: new parent
3848 * @new_dentry: where to create the new link
3849 * @delegated_inode: returns inode needing a delegation break
3850 *
3851 * The caller must hold dir->i_mutex
3852 *
3853 * If vfs_link discovers a delegation on the to-be-linked file in need
3854 * of breaking, it will return -EWOULDBLOCK and return a reference to the
3855 * inode in delegated_inode. The caller should then break the delegation
3856 * and retry. Because breaking a delegation may take a long time, the
3857 * caller should drop the i_mutex before doing so.
3858 *
3859 * Alternatively, a caller may pass NULL for delegated_inode. This may
3860 * be appropriate for callers that expect the underlying filesystem not
3861 * to be NFS exported.
3862 */
3863 int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry, struct inode **delegated_inode)
3864 {
3865 struct inode *inode = old_dentry->d_inode;
3866 unsigned max_links = dir->i_sb->s_max_links;
3867 int error;
3868
3869 if (!inode)
3870 return -ENOENT;
3871
3872 error = may_create(dir, new_dentry);
3873 if (error)
3874 return error;
3875
3876 if (dir->i_sb != inode->i_sb)
3877 return -EXDEV;
3878
3879 /*
3880 * A link to an append-only or immutable file cannot be created.
3881 */
3882 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
3883 return -EPERM;
3884 if (!dir->i_op->link)
3885 return -EPERM;
3886 if (S_ISDIR(inode->i_mode))
3887 return -EPERM;
3888
3889 error = security_inode_link(old_dentry, dir, new_dentry);
3890 if (error)
3891 return error;
3892
3893 mutex_lock(&inode->i_mutex);
3894 /* Make sure we don't allow creating hardlink to an unlinked file */
3895 if (inode->i_nlink == 0 && !(inode->i_state & I_LINKABLE))
3896 error = -ENOENT;
3897 else if (max_links && inode->i_nlink >= max_links)
3898 error = -EMLINK;
3899 else {
3900 error = try_break_deleg(inode, delegated_inode);
3901 if (!error)
3902 error = dir->i_op->link(old_dentry, dir, new_dentry);
3903 }
3904
3905 if (!error && (inode->i_state & I_LINKABLE)) {
3906 spin_lock(&inode->i_lock);
3907 inode->i_state &= ~I_LINKABLE;
3908 spin_unlock(&inode->i_lock);
3909 }
3910 mutex_unlock(&inode->i_mutex);
3911 if (!error)
3912 fsnotify_link(dir, inode, new_dentry);
3913 return error;
3914 }
3915 EXPORT_SYMBOL(vfs_link);
3916
3917 /*
3918 * Hardlinks are often used in delicate situations. We avoid
3919 * security-related surprises by not following symlinks on the
3920 * newname. --KAB
3921 *
3922 * We don't follow them on the oldname either to be compatible
3923 * with linux 2.0, and to avoid hard-linking to directories
3924 * and other special files. --ADM
3925 */
3926 SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
3927 int, newdfd, const char __user *, newname, int, flags)
3928 {
3929 struct dentry *new_dentry;
3930 struct path old_path, new_path;
3931 struct inode *delegated_inode = NULL;
3932 int how = 0;
3933 int error;
3934
3935 if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
3936 return -EINVAL;
3937 /*
3938 * To use null names we require CAP_DAC_READ_SEARCH
3939 * This ensures that not everyone will be able to create
3940 * handlink using the passed filedescriptor.
3941 */
3942 if (flags & AT_EMPTY_PATH) {
3943 if (!capable(CAP_DAC_READ_SEARCH))
3944 return -ENOENT;
3945 how = LOOKUP_EMPTY;
3946 }
3947
3948 if (flags & AT_SYMLINK_FOLLOW)
3949 how |= LOOKUP_FOLLOW;
3950 retry:
3951 error = user_path_at(olddfd, oldname, how, &old_path);
3952 if (error)
3953 return error;
3954
3955 new_dentry = user_path_create(newdfd, newname, &new_path,
3956 (how & LOOKUP_REVAL));
3957 error = PTR_ERR(new_dentry);
3958 if (IS_ERR(new_dentry))
3959 goto out;
3960
3961 error = -EXDEV;
3962 if (old_path.mnt != new_path.mnt)
3963 goto out_dput;
3964 error = may_linkat(&old_path);
3965 if (unlikely(error))
3966 goto out_dput;
3967 error = security_path_link(old_path.dentry, &new_path, new_dentry);
3968 if (error)
3969 goto out_dput;
3970 error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry, &delegated_inode);
3971 out_dput:
3972 done_path_create(&new_path, new_dentry);
3973 if (delegated_inode) {
3974 error = break_deleg_wait(&delegated_inode);
3975 if (!error) {
3976 path_put(&old_path);
3977 goto retry;
3978 }
3979 }
3980 if (retry_estale(error, how)) {
3981 path_put(&old_path);
3982 how |= LOOKUP_REVAL;
3983 goto retry;
3984 }
3985 out:
3986 path_put(&old_path);
3987
3988 return error;
3989 }
3990
3991 SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
3992 {
3993 return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
3994 }
3995
3996 /**
3997 * vfs_rename - rename a filesystem object
3998 * @old_dir: parent of source
3999 * @old_dentry: source
4000 * @new_dir: parent of destination
4001 * @new_dentry: destination
4002 * @delegated_inode: returns an inode needing a delegation break
4003 * @flags: rename flags
4004 *
4005 * The caller must hold multiple mutexes--see lock_rename()).
4006 *
4007 * If vfs_rename discovers a delegation in need of breaking at either
4008 * the source or destination, it will return -EWOULDBLOCK and return a
4009 * reference to the inode in delegated_inode. The caller should then
4010 * break the delegation and retry. Because breaking a delegation may
4011 * take a long time, the caller should drop all locks before doing
4012 * so.
4013 *
4014 * Alternatively, a caller may pass NULL for delegated_inode. This may
4015 * be appropriate for callers that expect the underlying filesystem not
4016 * to be NFS exported.
4017 *
4018 * The worst of all namespace operations - renaming directory. "Perverted"
4019 * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
4020 * Problems:
4021 * a) we can get into loop creation. Check is done in is_subdir().
4022 * b) race potential - two innocent renames can create a loop together.
4023 * That's where 4.4 screws up. Current fix: serialization on
4024 * sb->s_vfs_rename_mutex. We might be more accurate, but that's another
4025 * story.
4026 * c) we have to lock _four_ objects - parents and victim (if it exists),
4027 * and source (if it is not a directory).
4028 * And that - after we got ->i_mutex on parents (until then we don't know
4029 * whether the target exists). Solution: try to be smart with locking
4030 * order for inodes. We rely on the fact that tree topology may change
4031 * only under ->s_vfs_rename_mutex _and_ that parent of the object we
4032 * move will be locked. Thus we can rank directories by the tree
4033 * (ancestors first) and rank all non-directories after them.
4034 * That works since everybody except rename does "lock parent, lookup,
4035 * lock child" and rename is under ->s_vfs_rename_mutex.
4036 * HOWEVER, it relies on the assumption that any object with ->lookup()
4037 * has no more than 1 dentry. If "hybrid" objects will ever appear,
4038 * we'd better make sure that there's no link(2) for them.
4039 * d) conversion from fhandle to dentry may come in the wrong moment - when
4040 * we are removing the target. Solution: we will have to grab ->i_mutex
4041 * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
4042 * ->i_mutex on parents, which works but leads to some truly excessive
4043 * locking].
4044 */
4045 int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
4046 struct inode *new_dir, struct dentry *new_dentry,
4047 struct inode **delegated_inode, unsigned int flags)
4048 {
4049 int error;
4050 bool is_dir = d_is_dir(old_dentry);
4051 const unsigned char *old_name;
4052 struct inode *source = old_dentry->d_inode;
4053 struct inode *target = new_dentry->d_inode;
4054 bool new_is_dir = false;
4055 unsigned max_links = new_dir->i_sb->s_max_links;
4056
4057 if (source == target)
4058 return 0;
4059
4060 error = may_delete(old_dir, old_dentry, is_dir);
4061 if (error)
4062 return error;
4063
4064 if (!target) {
4065 error = may_create(new_dir, new_dentry);
4066 } else {
4067 new_is_dir = d_is_dir(new_dentry);
4068
4069 if (!(flags & RENAME_EXCHANGE))
4070 error = may_delete(new_dir, new_dentry, is_dir);
4071 else
4072 error = may_delete(new_dir, new_dentry, new_is_dir);
4073 }
4074 if (error)
4075 return error;
4076
4077 if (!old_dir->i_op->rename)
4078 return -EPERM;
4079
4080 if (flags && !old_dir->i_op->rename2)
4081 return -EINVAL;
4082
4083 /*
4084 * If we are going to change the parent - check write permissions,
4085 * we'll need to flip '..'.
4086 */
4087 if (new_dir != old_dir) {
4088 if (is_dir) {
4089 error = inode_permission(source, MAY_WRITE);
4090 if (error)
4091 return error;
4092 }
4093 if ((flags & RENAME_EXCHANGE) && new_is_dir) {
4094 error = inode_permission(target, MAY_WRITE);
4095 if (error)
4096 return error;
4097 }
4098 }
4099
4100 error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry,
4101 flags);
4102 if (error)
4103 return error;
4104
4105 old_name = fsnotify_oldname_init(old_dentry->d_name.name);
4106 dget(new_dentry);
4107 if (!is_dir || (flags & RENAME_EXCHANGE))
4108 lock_two_nondirectories(source, target);
4109 else if (target)
4110 mutex_lock(&target->i_mutex);
4111
4112 error = -EBUSY;
4113 if (d_mountpoint(old_dentry) || d_mountpoint(new_dentry))
4114 goto out;
4115
4116 if (max_links && new_dir != old_dir) {
4117 error = -EMLINK;
4118 if (is_dir && !new_is_dir && new_dir->i_nlink >= max_links)
4119 goto out;
4120 if ((flags & RENAME_EXCHANGE) && !is_dir && new_is_dir &&
4121 old_dir->i_nlink >= max_links)
4122 goto out;
4123 }
4124 if (is_dir && !(flags & RENAME_EXCHANGE) && target)
4125 shrink_dcache_parent(new_dentry);
4126 if (!is_dir) {
4127 error = try_break_deleg(source, delegated_inode);
4128 if (error)
4129 goto out;
4130 }
4131 if (target && !new_is_dir) {
4132 error = try_break_deleg(target, delegated_inode);
4133 if (error)
4134 goto out;
4135 }
4136 if (!flags) {
4137 error = old_dir->i_op->rename(old_dir, old_dentry,
4138 new_dir, new_dentry);
4139 } else {
4140 error = old_dir->i_op->rename2(old_dir, old_dentry,
4141 new_dir, new_dentry, flags);
4142 }
4143 if (error)
4144 goto out;
4145
4146 if (!(flags & RENAME_EXCHANGE) && target) {
4147 if (is_dir)
4148 target->i_flags |= S_DEAD;
4149 dont_mount(new_dentry);
4150 }
4151 if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) {
4152 if (!(flags & RENAME_EXCHANGE))
4153 d_move(old_dentry, new_dentry);
4154 else
4155 d_exchange(old_dentry, new_dentry);
4156 }
4157 out:
4158 if (!is_dir || (flags & RENAME_EXCHANGE))
4159 unlock_two_nondirectories(source, target);
4160 else if (target)
4161 mutex_unlock(&target->i_mutex);
4162 dput(new_dentry);
4163 if (!error) {
4164 fsnotify_move(old_dir, new_dir, old_name, is_dir,
4165 !(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry);
4166 if (flags & RENAME_EXCHANGE) {
4167 fsnotify_move(new_dir, old_dir, old_dentry->d_name.name,
4168 new_is_dir, NULL, new_dentry);
4169 }
4170 }
4171 fsnotify_oldname_free(old_name);
4172
4173 return error;
4174 }
4175 EXPORT_SYMBOL(vfs_rename);
4176
4177 SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname,
4178 int, newdfd, const char __user *, newname, unsigned int, flags)
4179 {
4180 struct dentry *old_dir, *new_dir;
4181 struct dentry *old_dentry, *new_dentry;
4182 struct dentry *trap;
4183 struct nameidata oldnd, newnd;
4184 struct inode *delegated_inode = NULL;
4185 struct filename *from;
4186 struct filename *to;
4187 unsigned int lookup_flags = 0;
4188 bool should_retry = false;
4189 int error;
4190
4191 if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
4192 return -EINVAL;
4193
4194 if ((flags & RENAME_NOREPLACE) && (flags & RENAME_EXCHANGE))
4195 return -EINVAL;
4196
4197 retry:
4198 from = user_path_parent(olddfd, oldname, &oldnd, lookup_flags);
4199 if (IS_ERR(from)) {
4200 error = PTR_ERR(from);
4201 goto exit;
4202 }
4203
4204 to = user_path_parent(newdfd, newname, &newnd, lookup_flags);
4205 if (IS_ERR(to)) {
4206 error = PTR_ERR(to);
4207 goto exit1;
4208 }
4209
4210 error = -EXDEV;
4211 if (oldnd.path.mnt != newnd.path.mnt)
4212 goto exit2;
4213
4214 old_dir = oldnd.path.dentry;
4215 error = -EBUSY;
4216 if (oldnd.last_type != LAST_NORM)
4217 goto exit2;
4218
4219 new_dir = newnd.path.dentry;
4220 if (flags & RENAME_NOREPLACE)
4221 error = -EEXIST;
4222 if (newnd.last_type != LAST_NORM)
4223 goto exit2;
4224
4225 error = mnt_want_write(oldnd.path.mnt);
4226 if (error)
4227 goto exit2;
4228
4229 oldnd.flags &= ~LOOKUP_PARENT;
4230 newnd.flags &= ~LOOKUP_PARENT;
4231 if (!(flags & RENAME_EXCHANGE))
4232 newnd.flags |= LOOKUP_RENAME_TARGET;
4233
4234 retry_deleg:
4235 trap = lock_rename(new_dir, old_dir);
4236
4237 old_dentry = lookup_hash(&oldnd);
4238 error = PTR_ERR(old_dentry);
4239 if (IS_ERR(old_dentry))
4240 goto exit3;
4241 /* source must exist */
4242 error = -ENOENT;
4243 if (d_is_negative(old_dentry))
4244 goto exit4;
4245 new_dentry = lookup_hash(&newnd);
4246 error = PTR_ERR(new_dentry);
4247 if (IS_ERR(new_dentry))
4248 goto exit4;
4249 error = -EEXIST;
4250 if ((flags & RENAME_NOREPLACE) && d_is_positive(new_dentry))
4251 goto exit5;
4252 if (flags & RENAME_EXCHANGE) {
4253 error = -ENOENT;
4254 if (d_is_negative(new_dentry))
4255 goto exit5;
4256
4257 if (!d_is_dir(new_dentry)) {
4258 error = -ENOTDIR;
4259 if (newnd.last.name[newnd.last.len])
4260 goto exit5;
4261 }
4262 }
4263 /* unless the source is a directory trailing slashes give -ENOTDIR */
4264 if (!d_is_dir(old_dentry)) {
4265 error = -ENOTDIR;
4266 if (oldnd.last.name[oldnd.last.len])
4267 goto exit5;
4268 if (!(flags & RENAME_EXCHANGE) && newnd.last.name[newnd.last.len])
4269 goto exit5;
4270 }
4271 /* source should not be ancestor of target */
4272 error = -EINVAL;
4273 if (old_dentry == trap)
4274 goto exit5;
4275 /* target should not be an ancestor of source */
4276 if (!(flags & RENAME_EXCHANGE))
4277 error = -ENOTEMPTY;
4278 if (new_dentry == trap)
4279 goto exit5;
4280
4281 error = security_path_rename(&oldnd.path, old_dentry,
4282 &newnd.path, new_dentry, flags);
4283 if (error)
4284 goto exit5;
4285 error = vfs_rename(old_dir->d_inode, old_dentry,
4286 new_dir->d_inode, new_dentry,
4287 &delegated_inode, flags);
4288 exit5:
4289 dput(new_dentry);
4290 exit4:
4291 dput(old_dentry);
4292 exit3:
4293 unlock_rename(new_dir, old_dir);
4294 if (delegated_inode) {
4295 error = break_deleg_wait(&delegated_inode);
4296 if (!error)
4297 goto retry_deleg;
4298 }
4299 mnt_drop_write(oldnd.path.mnt);
4300 exit2:
4301 if (retry_estale(error, lookup_flags))
4302 should_retry = true;
4303 path_put(&newnd.path);
4304 putname(to);
4305 exit1:
4306 path_put(&oldnd.path);
4307 putname(from);
4308 if (should_retry) {
4309 should_retry = false;
4310 lookup_flags |= LOOKUP_REVAL;
4311 goto retry;
4312 }
4313 exit:
4314 return error;
4315 }
4316
4317 SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
4318 int, newdfd, const char __user *, newname)
4319 {
4320 return sys_renameat2(olddfd, oldname, newdfd, newname, 0);
4321 }
4322
4323 SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
4324 {
4325 return sys_renameat2(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
4326 }
4327
4328 int readlink_copy(char __user *buffer, int buflen, const char *link)
4329 {
4330 int len = PTR_ERR(link);
4331 if (IS_ERR(link))
4332 goto out;
4333
4334 len = strlen(link);
4335 if (len > (unsigned) buflen)
4336 len = buflen;
4337 if (copy_to_user(buffer, link, len))
4338 len = -EFAULT;
4339 out:
4340 return len;
4341 }
4342 EXPORT_SYMBOL(readlink_copy);
4343
4344 /*
4345 * A helper for ->readlink(). This should be used *ONLY* for symlinks that
4346 * have ->follow_link() touching nd only in nd_set_link(). Using (or not
4347 * using) it for any given inode is up to filesystem.
4348 */
4349 int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
4350 {
4351 struct nameidata nd;
4352 void *cookie;
4353 int res;
4354
4355 nd.depth = 0;
4356 cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
4357 if (IS_ERR(cookie))
4358 return PTR_ERR(cookie);
4359
4360 res = readlink_copy(buffer, buflen, nd_get_link(&nd));
4361 if (dentry->d_inode->i_op->put_link)
4362 dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
4363 return res;
4364 }
4365 EXPORT_SYMBOL(generic_readlink);
4366
4367 /* get the link contents into pagecache */
4368 static char *page_getlink(struct dentry * dentry, struct page **ppage)
4369 {
4370 char *kaddr;
4371 struct page *page;
4372 struct address_space *mapping = dentry->d_inode->i_mapping;
4373 page = read_mapping_page(mapping, 0, NULL);
4374 if (IS_ERR(page))
4375 return (char*)page;
4376 *ppage = page;
4377 kaddr = kmap(page);
4378 nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1);
4379 return kaddr;
4380 }
4381
4382 int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
4383 {
4384 struct page *page = NULL;
4385 int res = readlink_copy(buffer, buflen, page_getlink(dentry, &page));
4386 if (page) {
4387 kunmap(page);
4388 page_cache_release(page);
4389 }
4390 return res;
4391 }
4392 EXPORT_SYMBOL(page_readlink);
4393
4394 void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
4395 {
4396 struct page *page = NULL;
4397 nd_set_link(nd, page_getlink(dentry, &page));
4398 return page;
4399 }
4400 EXPORT_SYMBOL(page_follow_link_light);
4401
4402 void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
4403 {
4404 struct page *page = cookie;
4405
4406 if (page) {
4407 kunmap(page);
4408 page_cache_release(page);
4409 }
4410 }
4411 EXPORT_SYMBOL(page_put_link);
4412
4413 /*
4414 * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
4415 */
4416 int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
4417 {
4418 struct address_space *mapping = inode->i_mapping;
4419 struct page *page;
4420 void *fsdata;
4421 int err;
4422 char *kaddr;
4423 unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
4424 if (nofs)
4425 flags |= AOP_FLAG_NOFS;
4426
4427 retry:
4428 err = pagecache_write_begin(NULL, mapping, 0, len-1,
4429 flags, &page, &fsdata);
4430 if (err)
4431 goto fail;
4432
4433 kaddr = kmap_atomic(page);
4434 memcpy(kaddr, symname, len-1);
4435 kunmap_atomic(kaddr);
4436
4437 err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
4438 page, fsdata);
4439 if (err < 0)
4440 goto fail;
4441 if (err < len-1)
4442 goto retry;
4443
4444 mark_inode_dirty(inode);
4445 return 0;
4446 fail:
4447 return err;
4448 }
4449 EXPORT_SYMBOL(__page_symlink);
4450
4451 int page_symlink(struct inode *inode, const char *symname, int len)
4452 {
4453 return __page_symlink(inode, symname, len,
4454 !(mapping_gfp_mask(inode->i_mapping) & __GFP_FS));
4455 }
4456 EXPORT_SYMBOL(page_symlink);
4457
4458 const struct inode_operations page_symlink_inode_operations = {
4459 .readlink = generic_readlink,
4460 .follow_link = page_follow_link_light,
4461 .put_link = page_put_link,
4462 };
4463 EXPORT_SYMBOL(page_symlink_inode_operations);