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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 | audit_getname(result); |
200 | return result; |
201 | |
202 | error: |
203 | final_putname(result); |
204 | return err; |
205 | } |
206 | |
207 | struct filename * |
208 | getname(const char __user * filename) |
209 | { |
210 | return getname_flags(filename, 0, NULL); |
211 | } |
212 | EXPORT_SYMBOL(getname); |
213 | |
214 | #ifdef CONFIG_AUDITSYSCALL |
215 | void putname(struct filename *name) |
216 | { |
217 | if (unlikely(!audit_dummy_context())) |
218 | return audit_putname(name); |
219 | final_putname(name); |
220 | } |
221 | #endif |
222 | |
223 | static int check_acl(struct inode *inode, int mask) |
224 | { |
225 | #ifdef CONFIG_FS_POSIX_ACL |
226 | struct posix_acl *acl; |
227 | |
228 | if (mask & MAY_NOT_BLOCK) { |
229 | acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS); |
230 | if (!acl) |
231 | return -EAGAIN; |
232 | /* no ->get_acl() calls in RCU mode... */ |
233 | if (acl == ACL_NOT_CACHED) |
234 | return -ECHILD; |
235 | return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK); |
236 | } |
237 | |
238 | acl = get_cached_acl(inode, ACL_TYPE_ACCESS); |
239 | |
240 | /* |
241 | * A filesystem can force a ACL callback by just never filling the |
242 | * ACL cache. But normally you'd fill the cache either at inode |
243 | * instantiation time, or on the first ->get_acl call. |
244 | * |
245 | * If the filesystem doesn't have a get_acl() function at all, we'll |
246 | * just create the negative cache entry. |
247 | */ |
248 | if (acl == ACL_NOT_CACHED) { |
249 | if (inode->i_op->get_acl) { |
250 | acl = inode->i_op->get_acl(inode, ACL_TYPE_ACCESS); |
251 | if (IS_ERR(acl)) |
252 | return PTR_ERR(acl); |
253 | } else { |
254 | set_cached_acl(inode, ACL_TYPE_ACCESS, NULL); |
255 | return -EAGAIN; |
256 | } |
257 | } |
258 | |
259 | if (acl) { |
260 | int error = posix_acl_permission(inode, acl, mask); |
261 | posix_acl_release(acl); |
262 | return error; |
263 | } |
264 | #endif |
265 | |
266 | return -EAGAIN; |
267 | } |
268 | |
269 | /* |
270 | * This does the basic permission checking |
271 | */ |
272 | static int acl_permission_check(struct inode *inode, int mask) |
273 | { |
274 | unsigned int mode = inode->i_mode; |
275 | |
276 | if (likely(uid_eq(current_fsuid(), inode->i_uid))) |
277 | mode >>= 6; |
278 | else { |
279 | if (IS_POSIXACL(inode) && (mode & S_IRWXG)) { |
280 | int error = check_acl(inode, mask); |
281 | if (error != -EAGAIN) |
282 | return error; |
283 | } |
284 | |
285 | if (in_group_p(inode->i_gid)) |
286 | mode >>= 3; |
287 | } |
288 | |
289 | /* |
290 | * If the DACs are ok we don't need any capability check. |
291 | */ |
292 | if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0) |
293 | return 0; |
294 | return -EACCES; |
295 | } |
296 | |
297 | /** |
298 | * generic_permission - check for access rights on a Posix-like filesystem |
299 | * @inode: inode to check access rights for |
300 | * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...) |
301 | * |
302 | * Used to check for read/write/execute permissions on a file. |
303 | * We use "fsuid" for this, letting us set arbitrary permissions |
304 | * for filesystem access without changing the "normal" uids which |
305 | * are used for other things. |
306 | * |
307 | * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk |
308 | * request cannot be satisfied (eg. requires blocking or too much complexity). |
309 | * It would then be called again in ref-walk mode. |
310 | */ |
311 | int generic_permission(struct inode *inode, int mask) |
312 | { |
313 | int ret; |
314 | |
315 | /* |
316 | * Do the basic permission checks. |
317 | */ |
318 | ret = acl_permission_check(inode, mask); |
319 | if (ret != -EACCES) |
320 | return ret; |
321 | |
322 | if (S_ISDIR(inode->i_mode)) { |
323 | /* DACs are overridable for directories */ |
324 | if (inode_capable(inode, CAP_DAC_OVERRIDE)) |
325 | return 0; |
326 | if (!(mask & MAY_WRITE)) |
327 | if (inode_capable(inode, CAP_DAC_READ_SEARCH)) |
328 | return 0; |
329 | return -EACCES; |
330 | } |
331 | /* |
332 | * Read/write DACs are always overridable. |
333 | * Executable DACs are overridable when there is |
334 | * at least one exec bit set. |
335 | */ |
336 | if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO)) |
337 | if (inode_capable(inode, CAP_DAC_OVERRIDE)) |
338 | return 0; |
339 | |
340 | /* |
341 | * Searching includes executable on directories, else just read. |
342 | */ |
343 | mask &= MAY_READ | MAY_WRITE | MAY_EXEC; |
344 | if (mask == MAY_READ) |
345 | if (inode_capable(inode, CAP_DAC_READ_SEARCH)) |
346 | return 0; |
347 | |
348 | return -EACCES; |
349 | } |
350 | |
351 | /* |
352 | * We _really_ want to just do "generic_permission()" without |
353 | * even looking at the inode->i_op values. So we keep a cache |
354 | * flag in inode->i_opflags, that says "this has not special |
355 | * permission function, use the fast case". |
356 | */ |
357 | static inline int do_inode_permission(struct inode *inode, int mask) |
358 | { |
359 | if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) { |
360 | if (likely(inode->i_op->permission)) |
361 | return inode->i_op->permission(inode, mask); |
362 | |
363 | /* This gets set once for the inode lifetime */ |
364 | spin_lock(&inode->i_lock); |
365 | inode->i_opflags |= IOP_FASTPERM; |
366 | spin_unlock(&inode->i_lock); |
367 | } |
368 | return generic_permission(inode, mask); |
369 | } |
370 | |
371 | /** |
372 | * __inode_permission - Check for access rights to a given inode |
373 | * @inode: Inode to check permission on |
374 | * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) |
375 | * |
376 | * Check for read/write/execute permissions on an inode. |
377 | * |
378 | * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask. |
379 | * |
380 | * This does not check for a read-only file system. You probably want |
381 | * inode_permission(). |
382 | */ |
383 | int __inode_permission(struct inode *inode, int mask) |
384 | { |
385 | int retval; |
386 | |
387 | if (unlikely(mask & MAY_WRITE)) { |
388 | /* |
389 | * Nobody gets write access to an immutable file. |
390 | */ |
391 | if (IS_IMMUTABLE(inode)) |
392 | return -EACCES; |
393 | } |
394 | |
395 | retval = do_inode_permission(inode, mask); |
396 | if (retval) |
397 | return retval; |
398 | |
399 | retval = devcgroup_inode_permission(inode, mask); |
400 | if (retval) |
401 | return retval; |
402 | |
403 | return security_inode_permission(inode, mask); |
404 | } |
405 | |
406 | /** |
407 | * sb_permission - Check superblock-level permissions |
408 | * @sb: Superblock of inode to check permission on |
409 | * @inode: Inode to check permission on |
410 | * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) |
411 | * |
412 | * Separate out file-system wide checks from inode-specific permission checks. |
413 | */ |
414 | static int sb_permission(struct super_block *sb, struct inode *inode, int mask) |
415 | { |
416 | if (unlikely(mask & MAY_WRITE)) { |
417 | umode_t mode = inode->i_mode; |
418 | |
419 | /* Nobody gets write access to a read-only fs. */ |
420 | if ((sb->s_flags & MS_RDONLY) && |
421 | (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) |
422 | return -EROFS; |
423 | } |
424 | return 0; |
425 | } |
426 | |
427 | /** |
428 | * inode_permission - Check for access rights to a given inode |
429 | * @inode: Inode to check permission on |
430 | * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC) |
431 | * |
432 | * Check for read/write/execute permissions on an inode. We use fs[ug]id for |
433 | * this, letting us set arbitrary permissions for filesystem access without |
434 | * changing the "normal" UIDs which are used for other things. |
435 | * |
436 | * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask. |
437 | */ |
438 | int inode_permission(struct inode *inode, int mask) |
439 | { |
440 | int retval; |
441 | |
442 | retval = sb_permission(inode->i_sb, inode, mask); |
443 | if (retval) |
444 | return retval; |
445 | return __inode_permission(inode, mask); |
446 | } |
447 | |
448 | /** |
449 | * path_get - get a reference to a path |
450 | * @path: path to get the reference to |
451 | * |
452 | * Given a path increment the reference count to the dentry and the vfsmount. |
453 | */ |
454 | void path_get(const struct path *path) |
455 | { |
456 | mntget(path->mnt); |
457 | dget(path->dentry); |
458 | } |
459 | EXPORT_SYMBOL(path_get); |
460 | |
461 | /** |
462 | * path_put - put a reference to a path |
463 | * @path: path to put the reference to |
464 | * |
465 | * Given a path decrement the reference count to the dentry and the vfsmount. |
466 | */ |
467 | void path_put(const struct path *path) |
468 | { |
469 | dput(path->dentry); |
470 | mntput(path->mnt); |
471 | } |
472 | EXPORT_SYMBOL(path_put); |
473 | |
474 | /* |
475 | * Path walking has 2 modes, rcu-walk and ref-walk (see |
476 | * Documentation/filesystems/path-lookup.txt). In situations when we can't |
477 | * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab |
478 | * normal reference counts on dentries and vfsmounts to transition to rcu-walk |
479 | * mode. Refcounts are grabbed at the last known good point before rcu-walk |
480 | * got stuck, so ref-walk may continue from there. If this is not successful |
481 | * (eg. a seqcount has changed), then failure is returned and it's up to caller |
482 | * to restart the path walk from the beginning in ref-walk mode. |
483 | */ |
484 | |
485 | static inline void lock_rcu_walk(void) |
486 | { |
487 | br_read_lock(&vfsmount_lock); |
488 | rcu_read_lock(); |
489 | } |
490 | |
491 | static inline void unlock_rcu_walk(void) |
492 | { |
493 | rcu_read_unlock(); |
494 | br_read_unlock(&vfsmount_lock); |
495 | } |
496 | |
497 | /** |
498 | * unlazy_walk - try to switch to ref-walk mode. |
499 | * @nd: nameidata pathwalk data |
500 | * @dentry: child of nd->path.dentry or NULL |
501 | * Returns: 0 on success, -ECHILD on failure |
502 | * |
503 | * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry |
504 | * for ref-walk mode. @dentry must be a path found by a do_lookup call on |
505 | * @nd or NULL. Must be called from rcu-walk context. |
506 | */ |
507 | static int unlazy_walk(struct nameidata *nd, struct dentry *dentry) |
508 | { |
509 | struct fs_struct *fs = current->fs; |
510 | struct dentry *parent = nd->path.dentry; |
511 | int want_root = 0; |
512 | |
513 | BUG_ON(!(nd->flags & LOOKUP_RCU)); |
514 | if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) { |
515 | want_root = 1; |
516 | spin_lock(&fs->lock); |
517 | if (nd->root.mnt != fs->root.mnt || |
518 | nd->root.dentry != fs->root.dentry) |
519 | goto err_root; |
520 | } |
521 | spin_lock(&parent->d_lock); |
522 | if (!dentry) { |
523 | if (!__d_rcu_to_refcount(parent, nd->seq)) |
524 | goto err_parent; |
525 | BUG_ON(nd->inode != parent->d_inode); |
526 | } else { |
527 | if (dentry->d_parent != parent) |
528 | goto err_parent; |
529 | spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); |
530 | if (!__d_rcu_to_refcount(dentry, nd->seq)) |
531 | goto err_child; |
532 | /* |
533 | * If the sequence check on the child dentry passed, then |
534 | * the child has not been removed from its parent. This |
535 | * means the parent dentry must be valid and able to take |
536 | * a reference at this point. |
537 | */ |
538 | BUG_ON(!IS_ROOT(dentry) && dentry->d_parent != parent); |
539 | BUG_ON(!parent->d_count); |
540 | parent->d_count++; |
541 | spin_unlock(&dentry->d_lock); |
542 | } |
543 | spin_unlock(&parent->d_lock); |
544 | if (want_root) { |
545 | path_get(&nd->root); |
546 | spin_unlock(&fs->lock); |
547 | } |
548 | mntget(nd->path.mnt); |
549 | |
550 | unlock_rcu_walk(); |
551 | nd->flags &= ~LOOKUP_RCU; |
552 | return 0; |
553 | |
554 | err_child: |
555 | spin_unlock(&dentry->d_lock); |
556 | err_parent: |
557 | spin_unlock(&parent->d_lock); |
558 | err_root: |
559 | if (want_root) |
560 | spin_unlock(&fs->lock); |
561 | return -ECHILD; |
562 | } |
563 | |
564 | static inline int d_revalidate(struct dentry *dentry, unsigned int flags) |
565 | { |
566 | return dentry->d_op->d_revalidate(dentry, flags); |
567 | } |
568 | |
569 | /** |
570 | * complete_walk - successful completion of path walk |
571 | * @nd: pointer nameidata |
572 | * |
573 | * If we had been in RCU mode, drop out of it and legitimize nd->path. |
574 | * Revalidate the final result, unless we'd already done that during |
575 | * the path walk or the filesystem doesn't ask for it. Return 0 on |
576 | * success, -error on failure. In case of failure caller does not |
577 | * need to drop nd->path. |
578 | */ |
579 | static int complete_walk(struct nameidata *nd) |
580 | { |
581 | struct dentry *dentry = nd->path.dentry; |
582 | int status; |
583 | |
584 | if (nd->flags & LOOKUP_RCU) { |
585 | nd->flags &= ~LOOKUP_RCU; |
586 | if (!(nd->flags & LOOKUP_ROOT)) |
587 | nd->root.mnt = NULL; |
588 | spin_lock(&dentry->d_lock); |
589 | if (unlikely(!__d_rcu_to_refcount(dentry, nd->seq))) { |
590 | spin_unlock(&dentry->d_lock); |
591 | unlock_rcu_walk(); |
592 | return -ECHILD; |
593 | } |
594 | BUG_ON(nd->inode != dentry->d_inode); |
595 | spin_unlock(&dentry->d_lock); |
596 | mntget(nd->path.mnt); |
597 | unlock_rcu_walk(); |
598 | } |
599 | |
600 | if (likely(!(nd->flags & LOOKUP_JUMPED))) |
601 | return 0; |
602 | |
603 | if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE))) |
604 | return 0; |
605 | |
606 | status = dentry->d_op->d_weak_revalidate(dentry, nd->flags); |
607 | if (status > 0) |
608 | return 0; |
609 | |
610 | if (!status) |
611 | status = -ESTALE; |
612 | |
613 | path_put(&nd->path); |
614 | return status; |
615 | } |
616 | |
617 | static __always_inline void set_root(struct nameidata *nd) |
618 | { |
619 | if (!nd->root.mnt) |
620 | get_fs_root(current->fs, &nd->root); |
621 | } |
622 | |
623 | static int link_path_walk(const char *, struct nameidata *); |
624 | |
625 | static __always_inline void set_root_rcu(struct nameidata *nd) |
626 | { |
627 | if (!nd->root.mnt) { |
628 | struct fs_struct *fs = current->fs; |
629 | unsigned seq; |
630 | |
631 | do { |
632 | seq = read_seqcount_begin(&fs->seq); |
633 | nd->root = fs->root; |
634 | nd->seq = __read_seqcount_begin(&nd->root.dentry->d_seq); |
635 | } while (read_seqcount_retry(&fs->seq, seq)); |
636 | } |
637 | } |
638 | |
639 | static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link) |
640 | { |
641 | int ret; |
642 | |
643 | if (IS_ERR(link)) |
644 | goto fail; |
645 | |
646 | if (*link == '/') { |
647 | set_root(nd); |
648 | path_put(&nd->path); |
649 | nd->path = nd->root; |
650 | path_get(&nd->root); |
651 | nd->flags |= LOOKUP_JUMPED; |
652 | } |
653 | nd->inode = nd->path.dentry->d_inode; |
654 | |
655 | ret = link_path_walk(link, nd); |
656 | return ret; |
657 | fail: |
658 | path_put(&nd->path); |
659 | return PTR_ERR(link); |
660 | } |
661 | |
662 | static void path_put_conditional(struct path *path, struct nameidata *nd) |
663 | { |
664 | dput(path->dentry); |
665 | if (path->mnt != nd->path.mnt) |
666 | mntput(path->mnt); |
667 | } |
668 | |
669 | static inline void path_to_nameidata(const struct path *path, |
670 | struct nameidata *nd) |
671 | { |
672 | if (!(nd->flags & LOOKUP_RCU)) { |
673 | dput(nd->path.dentry); |
674 | if (nd->path.mnt != path->mnt) |
675 | mntput(nd->path.mnt); |
676 | } |
677 | nd->path.mnt = path->mnt; |
678 | nd->path.dentry = path->dentry; |
679 | } |
680 | |
681 | /* |
682 | * Helper to directly jump to a known parsed path from ->follow_link, |
683 | * caller must have taken a reference to path beforehand. |
684 | */ |
685 | void nd_jump_link(struct nameidata *nd, struct path *path) |
686 | { |
687 | path_put(&nd->path); |
688 | |
689 | nd->path = *path; |
690 | nd->inode = nd->path.dentry->d_inode; |
691 | nd->flags |= LOOKUP_JUMPED; |
692 | } |
693 | |
694 | static inline void put_link(struct nameidata *nd, struct path *link, void *cookie) |
695 | { |
696 | struct inode *inode = link->dentry->d_inode; |
697 | if (inode->i_op->put_link) |
698 | inode->i_op->put_link(link->dentry, nd, cookie); |
699 | path_put(link); |
700 | } |
701 | |
702 | int sysctl_protected_symlinks __read_mostly = 0; |
703 | int sysctl_protected_hardlinks __read_mostly = 0; |
704 | |
705 | /** |
706 | * may_follow_link - Check symlink following for unsafe situations |
707 | * @link: The path of the symlink |
708 | * @nd: nameidata pathwalk data |
709 | * |
710 | * In the case of the sysctl_protected_symlinks sysctl being enabled, |
711 | * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is |
712 | * in a sticky world-writable directory. This is to protect privileged |
713 | * processes from failing races against path names that may change out |
714 | * from under them by way of other users creating malicious symlinks. |
715 | * It will permit symlinks to be followed only when outside a sticky |
716 | * world-writable directory, or when the uid of the symlink and follower |
717 | * match, or when the directory owner matches the symlink's owner. |
718 | * |
719 | * Returns 0 if following the symlink is allowed, -ve on error. |
720 | */ |
721 | static inline int may_follow_link(struct path *link, struct nameidata *nd) |
722 | { |
723 | const struct inode *inode; |
724 | const struct inode *parent; |
725 | |
726 | if (!sysctl_protected_symlinks) |
727 | return 0; |
728 | |
729 | /* Allowed if owner and follower match. */ |
730 | inode = link->dentry->d_inode; |
731 | if (uid_eq(current_cred()->fsuid, inode->i_uid)) |
732 | return 0; |
733 | |
734 | /* Allowed if parent directory not sticky and world-writable. */ |
735 | parent = nd->path.dentry->d_inode; |
736 | if ((parent->i_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH)) |
737 | return 0; |
738 | |
739 | /* Allowed if parent directory and link owner match. */ |
740 | if (uid_eq(parent->i_uid, inode->i_uid)) |
741 | return 0; |
742 | |
743 | audit_log_link_denied("follow_link", link); |
744 | path_put_conditional(link, nd); |
745 | path_put(&nd->path); |
746 | return -EACCES; |
747 | } |
748 | |
749 | /** |
750 | * safe_hardlink_source - Check for safe hardlink conditions |
751 | * @inode: the source inode to hardlink from |
752 | * |
753 | * Return false if at least one of the following conditions: |
754 | * - inode is not a regular file |
755 | * - inode is setuid |
756 | * - inode is setgid and group-exec |
757 | * - access failure for read and write |
758 | * |
759 | * Otherwise returns true. |
760 | */ |
761 | static bool safe_hardlink_source(struct inode *inode) |
762 | { |
763 | umode_t mode = inode->i_mode; |
764 | |
765 | /* Special files should not get pinned to the filesystem. */ |
766 | if (!S_ISREG(mode)) |
767 | return false; |
768 | |
769 | /* Setuid files should not get pinned to the filesystem. */ |
770 | if (mode & S_ISUID) |
771 | return false; |
772 | |
773 | /* Executable setgid files should not get pinned to the filesystem. */ |
774 | if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) |
775 | return false; |
776 | |
777 | /* Hardlinking to unreadable or unwritable sources is dangerous. */ |
778 | if (inode_permission(inode, MAY_READ | MAY_WRITE)) |
779 | return false; |
780 | |
781 | return true; |
782 | } |
783 | |
784 | /** |
785 | * may_linkat - Check permissions for creating a hardlink |
786 | * @link: the source to hardlink from |
787 | * |
788 | * Block hardlink when all of: |
789 | * - sysctl_protected_hardlinks enabled |
790 | * - fsuid does not match inode |
791 | * - hardlink source is unsafe (see safe_hardlink_source() above) |
792 | * - not CAP_FOWNER |
793 | * |
794 | * Returns 0 if successful, -ve on error. |
795 | */ |
796 | static int may_linkat(struct path *link) |
797 | { |
798 | const struct cred *cred; |
799 | struct inode *inode; |
800 | |
801 | if (!sysctl_protected_hardlinks) |
802 | return 0; |
803 | |
804 | cred = current_cred(); |
805 | inode = link->dentry->d_inode; |
806 | |
807 | /* Source inode owner (or CAP_FOWNER) can hardlink all they like, |
808 | * otherwise, it must be a safe source. |
809 | */ |
810 | if (uid_eq(cred->fsuid, inode->i_uid) || safe_hardlink_source(inode) || |
811 | capable(CAP_FOWNER)) |
812 | return 0; |
813 | |
814 | audit_log_link_denied("linkat", link); |
815 | return -EPERM; |
816 | } |
817 | |
818 | static __always_inline int |
819 | follow_link(struct path *link, struct nameidata *nd, void **p) |
820 | { |
821 | struct dentry *dentry = link->dentry; |
822 | int error; |
823 | char *s; |
824 | |
825 | BUG_ON(nd->flags & LOOKUP_RCU); |
826 | |
827 | if (link->mnt == nd->path.mnt) |
828 | mntget(link->mnt); |
829 | |
830 | error = -ELOOP; |
831 | if (unlikely(current->total_link_count >= 40)) |
832 | goto out_put_nd_path; |
833 | |
834 | cond_resched(); |
835 | current->total_link_count++; |
836 | |
837 | touch_atime(link); |
838 | nd_set_link(nd, NULL); |
839 | |
840 | error = security_inode_follow_link(link->dentry, nd); |
841 | if (error) |
842 | goto out_put_nd_path; |
843 | |
844 | nd->last_type = LAST_BIND; |
845 | *p = dentry->d_inode->i_op->follow_link(dentry, nd); |
846 | error = PTR_ERR(*p); |
847 | if (IS_ERR(*p)) |
848 | goto out_put_nd_path; |
849 | |
850 | error = 0; |
851 | s = nd_get_link(nd); |
852 | if (s) { |
853 | error = __vfs_follow_link(nd, s); |
854 | if (unlikely(error)) |
855 | put_link(nd, link, *p); |
856 | } |
857 | |
858 | return error; |
859 | |
860 | out_put_nd_path: |
861 | *p = NULL; |
862 | path_put(&nd->path); |
863 | path_put(link); |
864 | return error; |
865 | } |
866 | |
867 | static int follow_up_rcu(struct path *path) |
868 | { |
869 | struct mount *mnt = real_mount(path->mnt); |
870 | struct mount *parent; |
871 | struct dentry *mountpoint; |
872 | |
873 | parent = mnt->mnt_parent; |
874 | if (&parent->mnt == path->mnt) |
875 | return 0; |
876 | mountpoint = mnt->mnt_mountpoint; |
877 | path->dentry = mountpoint; |
878 | path->mnt = &parent->mnt; |
879 | return 1; |
880 | } |
881 | |
882 | /* |
883 | * follow_up - Find the mountpoint of path's vfsmount |
884 | * |
885 | * Given a path, find the mountpoint of its source file system. |
886 | * Replace @path with the path of the mountpoint in the parent mount. |
887 | * Up is towards /. |
888 | * |
889 | * Return 1 if we went up a level and 0 if we were already at the |
890 | * root. |
891 | */ |
892 | int follow_up(struct path *path) |
893 | { |
894 | struct mount *mnt = real_mount(path->mnt); |
895 | struct mount *parent; |
896 | struct dentry *mountpoint; |
897 | |
898 | br_read_lock(&vfsmount_lock); |
899 | parent = mnt->mnt_parent; |
900 | if (parent == mnt) { |
901 | br_read_unlock(&vfsmount_lock); |
902 | return 0; |
903 | } |
904 | mntget(&parent->mnt); |
905 | mountpoint = dget(mnt->mnt_mountpoint); |
906 | br_read_unlock(&vfsmount_lock); |
907 | dput(path->dentry); |
908 | path->dentry = mountpoint; |
909 | mntput(path->mnt); |
910 | path->mnt = &parent->mnt; |
911 | return 1; |
912 | } |
913 | |
914 | /* |
915 | * Perform an automount |
916 | * - return -EISDIR to tell follow_managed() to stop and return the path we |
917 | * were called with. |
918 | */ |
919 | static int follow_automount(struct path *path, unsigned flags, |
920 | bool *need_mntput) |
921 | { |
922 | struct vfsmount *mnt; |
923 | int err; |
924 | |
925 | if (!path->dentry->d_op || !path->dentry->d_op->d_automount) |
926 | return -EREMOTE; |
927 | |
928 | /* We don't want to mount if someone's just doing a stat - |
929 | * unless they're stat'ing a directory and appended a '/' to |
930 | * the name. |
931 | * |
932 | * We do, however, want to mount if someone wants to open or |
933 | * create a file of any type under the mountpoint, wants to |
934 | * traverse through the mountpoint or wants to open the |
935 | * mounted directory. Also, autofs may mark negative dentries |
936 | * as being automount points. These will need the attentions |
937 | * of the daemon to instantiate them before they can be used. |
938 | */ |
939 | if (!(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY | |
940 | LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) && |
941 | path->dentry->d_inode) |
942 | return -EISDIR; |
943 | |
944 | current->total_link_count++; |
945 | if (current->total_link_count >= 40) |
946 | return -ELOOP; |
947 | |
948 | mnt = path->dentry->d_op->d_automount(path); |
949 | if (IS_ERR(mnt)) { |
950 | /* |
951 | * The filesystem is allowed to return -EISDIR here to indicate |
952 | * it doesn't want to automount. For instance, autofs would do |
953 | * this so that its userspace daemon can mount on this dentry. |
954 | * |
955 | * However, we can only permit this if it's a terminal point in |
956 | * the path being looked up; if it wasn't then the remainder of |
957 | * the path is inaccessible and we should say so. |
958 | */ |
959 | if (PTR_ERR(mnt) == -EISDIR && (flags & LOOKUP_PARENT)) |
960 | return -EREMOTE; |
961 | return PTR_ERR(mnt); |
962 | } |
963 | |
964 | if (!mnt) /* mount collision */ |
965 | return 0; |
966 | |
967 | if (!*need_mntput) { |
968 | /* lock_mount() may release path->mnt on error */ |
969 | mntget(path->mnt); |
970 | *need_mntput = true; |
971 | } |
972 | err = finish_automount(mnt, path); |
973 | |
974 | switch (err) { |
975 | case -EBUSY: |
976 | /* Someone else made a mount here whilst we were busy */ |
977 | return 0; |
978 | case 0: |
979 | path_put(path); |
980 | path->mnt = mnt; |
981 | path->dentry = dget(mnt->mnt_root); |
982 | return 0; |
983 | default: |
984 | return err; |
985 | } |
986 | |
987 | } |
988 | |
989 | /* |
990 | * Handle a dentry that is managed in some way. |
991 | * - Flagged for transit management (autofs) |
992 | * - Flagged as mountpoint |
993 | * - Flagged as automount point |
994 | * |
995 | * This may only be called in refwalk mode. |
996 | * |
997 | * Serialization is taken care of in namespace.c |
998 | */ |
999 | static int follow_managed(struct path *path, unsigned flags) |
1000 | { |
1001 | struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */ |
1002 | unsigned managed; |
1003 | bool need_mntput = false; |
1004 | int ret = 0; |
1005 | |
1006 | /* Given that we're not holding a lock here, we retain the value in a |
1007 | * local variable for each dentry as we look at it so that we don't see |
1008 | * the components of that value change under us */ |
1009 | while (managed = ACCESS_ONCE(path->dentry->d_flags), |
1010 | managed &= DCACHE_MANAGED_DENTRY, |
1011 | unlikely(managed != 0)) { |
1012 | /* Allow the filesystem to manage the transit without i_mutex |
1013 | * being held. */ |
1014 | if (managed & DCACHE_MANAGE_TRANSIT) { |
1015 | BUG_ON(!path->dentry->d_op); |
1016 | BUG_ON(!path->dentry->d_op->d_manage); |
1017 | ret = path->dentry->d_op->d_manage(path->dentry, false); |
1018 | if (ret < 0) |
1019 | break; |
1020 | } |
1021 | |
1022 | /* Transit to a mounted filesystem. */ |
1023 | if (managed & DCACHE_MOUNTED) { |
1024 | struct vfsmount *mounted = lookup_mnt(path); |
1025 | if (mounted) { |
1026 | dput(path->dentry); |
1027 | if (need_mntput) |
1028 | mntput(path->mnt); |
1029 | path->mnt = mounted; |
1030 | path->dentry = dget(mounted->mnt_root); |
1031 | need_mntput = true; |
1032 | continue; |
1033 | } |
1034 | |
1035 | /* Something is mounted on this dentry in another |
1036 | * namespace and/or whatever was mounted there in this |
1037 | * namespace got unmounted before we managed to get the |
1038 | * vfsmount_lock */ |
1039 | } |
1040 | |
1041 | /* Handle an automount point */ |
1042 | if (managed & DCACHE_NEED_AUTOMOUNT) { |
1043 | ret = follow_automount(path, flags, &need_mntput); |
1044 | if (ret < 0) |
1045 | break; |
1046 | continue; |
1047 | } |
1048 | |
1049 | /* We didn't change the current path point */ |
1050 | break; |
1051 | } |
1052 | |
1053 | if (need_mntput && path->mnt == mnt) |
1054 | mntput(path->mnt); |
1055 | if (ret == -EISDIR) |
1056 | ret = 0; |
1057 | return ret < 0 ? ret : need_mntput; |
1058 | } |
1059 | |
1060 | int follow_down_one(struct path *path) |
1061 | { |
1062 | struct vfsmount *mounted; |
1063 | |
1064 | mounted = lookup_mnt(path); |
1065 | if (mounted) { |
1066 | dput(path->dentry); |
1067 | mntput(path->mnt); |
1068 | path->mnt = mounted; |
1069 | path->dentry = dget(mounted->mnt_root); |
1070 | return 1; |
1071 | } |
1072 | return 0; |
1073 | } |
1074 | |
1075 | static inline bool managed_dentry_might_block(struct dentry *dentry) |
1076 | { |
1077 | return (dentry->d_flags & DCACHE_MANAGE_TRANSIT && |
1078 | dentry->d_op->d_manage(dentry, true) < 0); |
1079 | } |
1080 | |
1081 | /* |
1082 | * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if |
1083 | * we meet a managed dentry that would need blocking. |
1084 | */ |
1085 | static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, |
1086 | struct inode **inode) |
1087 | { |
1088 | for (;;) { |
1089 | struct mount *mounted; |
1090 | /* |
1091 | * Don't forget we might have a non-mountpoint managed dentry |
1092 | * that wants to block transit. |
1093 | */ |
1094 | if (unlikely(managed_dentry_might_block(path->dentry))) |
1095 | return false; |
1096 | |
1097 | if (!d_mountpoint(path->dentry)) |
1098 | break; |
1099 | |
1100 | mounted = __lookup_mnt(path->mnt, path->dentry, 1); |
1101 | if (!mounted) |
1102 | break; |
1103 | path->mnt = &mounted->mnt; |
1104 | path->dentry = mounted->mnt.mnt_root; |
1105 | nd->flags |= LOOKUP_JUMPED; |
1106 | nd->seq = read_seqcount_begin(&path->dentry->d_seq); |
1107 | /* |
1108 | * Update the inode too. We don't need to re-check the |
1109 | * dentry sequence number here after this d_inode read, |
1110 | * because a mount-point is always pinned. |
1111 | */ |
1112 | *inode = path->dentry->d_inode; |
1113 | } |
1114 | return true; |
1115 | } |
1116 | |
1117 | static void follow_mount_rcu(struct nameidata *nd) |
1118 | { |
1119 | while (d_mountpoint(nd->path.dentry)) { |
1120 | struct mount *mounted; |
1121 | mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry, 1); |
1122 | if (!mounted) |
1123 | break; |
1124 | nd->path.mnt = &mounted->mnt; |
1125 | nd->path.dentry = mounted->mnt.mnt_root; |
1126 | nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); |
1127 | } |
1128 | } |
1129 | |
1130 | static int follow_dotdot_rcu(struct nameidata *nd) |
1131 | { |
1132 | set_root_rcu(nd); |
1133 | |
1134 | while (1) { |
1135 | if (nd->path.dentry == nd->root.dentry && |
1136 | nd->path.mnt == nd->root.mnt) { |
1137 | break; |
1138 | } |
1139 | if (nd->path.dentry != nd->path.mnt->mnt_root) { |
1140 | struct dentry *old = nd->path.dentry; |
1141 | struct dentry *parent = old->d_parent; |
1142 | unsigned seq; |
1143 | |
1144 | seq = read_seqcount_begin(&parent->d_seq); |
1145 | if (read_seqcount_retry(&old->d_seq, nd->seq)) |
1146 | goto failed; |
1147 | nd->path.dentry = parent; |
1148 | nd->seq = seq; |
1149 | break; |
1150 | } |
1151 | if (!follow_up_rcu(&nd->path)) |
1152 | break; |
1153 | nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); |
1154 | } |
1155 | follow_mount_rcu(nd); |
1156 | nd->inode = nd->path.dentry->d_inode; |
1157 | return 0; |
1158 | |
1159 | failed: |
1160 | nd->flags &= ~LOOKUP_RCU; |
1161 | if (!(nd->flags & LOOKUP_ROOT)) |
1162 | nd->root.mnt = NULL; |
1163 | unlock_rcu_walk(); |
1164 | return -ECHILD; |
1165 | } |
1166 | |
1167 | /* |
1168 | * Follow down to the covering mount currently visible to userspace. At each |
1169 | * point, the filesystem owning that dentry may be queried as to whether the |
1170 | * caller is permitted to proceed or not. |
1171 | */ |
1172 | int follow_down(struct path *path) |
1173 | { |
1174 | unsigned managed; |
1175 | int ret; |
1176 | |
1177 | while (managed = ACCESS_ONCE(path->dentry->d_flags), |
1178 | unlikely(managed & DCACHE_MANAGED_DENTRY)) { |
1179 | /* Allow the filesystem to manage the transit without i_mutex |
1180 | * being held. |
1181 | * |
1182 | * We indicate to the filesystem if someone is trying to mount |
1183 | * something here. This gives autofs the chance to deny anyone |
1184 | * other than its daemon the right to mount on its |
1185 | * superstructure. |
1186 | * |
1187 | * The filesystem may sleep at this point. |
1188 | */ |
1189 | if (managed & DCACHE_MANAGE_TRANSIT) { |
1190 | BUG_ON(!path->dentry->d_op); |
1191 | BUG_ON(!path->dentry->d_op->d_manage); |
1192 | ret = path->dentry->d_op->d_manage( |
1193 | path->dentry, false); |
1194 | if (ret < 0) |
1195 | return ret == -EISDIR ? 0 : ret; |
1196 | } |
1197 | |
1198 | /* Transit to a mounted filesystem. */ |
1199 | if (managed & DCACHE_MOUNTED) { |
1200 | struct vfsmount *mounted = lookup_mnt(path); |
1201 | if (!mounted) |
1202 | break; |
1203 | dput(path->dentry); |
1204 | mntput(path->mnt); |
1205 | path->mnt = mounted; |
1206 | path->dentry = dget(mounted->mnt_root); |
1207 | continue; |
1208 | } |
1209 | |
1210 | /* Don't handle automount points here */ |
1211 | break; |
1212 | } |
1213 | return 0; |
1214 | } |
1215 | |
1216 | /* |
1217 | * Skip to top of mountpoint pile in refwalk mode for follow_dotdot() |
1218 | */ |
1219 | static void follow_mount(struct path *path) |
1220 | { |
1221 | while (d_mountpoint(path->dentry)) { |
1222 | struct vfsmount *mounted = lookup_mnt(path); |
1223 | if (!mounted) |
1224 | break; |
1225 | dput(path->dentry); |
1226 | mntput(path->mnt); |
1227 | path->mnt = mounted; |
1228 | path->dentry = dget(mounted->mnt_root); |
1229 | } |
1230 | } |
1231 | |
1232 | static void follow_dotdot(struct nameidata *nd) |
1233 | { |
1234 | set_root(nd); |
1235 | |
1236 | while(1) { |
1237 | struct dentry *old = nd->path.dentry; |
1238 | |
1239 | if (nd->path.dentry == nd->root.dentry && |
1240 | nd->path.mnt == nd->root.mnt) { |
1241 | break; |
1242 | } |
1243 | if (nd->path.dentry != nd->path.mnt->mnt_root) { |
1244 | /* rare case of legitimate dget_parent()... */ |
1245 | nd->path.dentry = dget_parent(nd->path.dentry); |
1246 | dput(old); |
1247 | break; |
1248 | } |
1249 | if (!follow_up(&nd->path)) |
1250 | break; |
1251 | } |
1252 | follow_mount(&nd->path); |
1253 | nd->inode = nd->path.dentry->d_inode; |
1254 | } |
1255 | |
1256 | /* |
1257 | * This looks up the name in dcache, possibly revalidates the old dentry and |
1258 | * allocates a new one if not found or not valid. In the need_lookup argument |
1259 | * returns whether i_op->lookup is necessary. |
1260 | * |
1261 | * dir->d_inode->i_mutex must be held |
1262 | */ |
1263 | static struct dentry *lookup_dcache(struct qstr *name, struct dentry *dir, |
1264 | unsigned int flags, bool *need_lookup) |
1265 | { |
1266 | struct dentry *dentry; |
1267 | int error; |
1268 | |
1269 | *need_lookup = false; |
1270 | dentry = d_lookup(dir, name); |
1271 | if (dentry) { |
1272 | if (dentry->d_flags & DCACHE_OP_REVALIDATE) { |
1273 | error = d_revalidate(dentry, flags); |
1274 | if (unlikely(error <= 0)) { |
1275 | if (error < 0) { |
1276 | dput(dentry); |
1277 | return ERR_PTR(error); |
1278 | } else if (!d_invalidate(dentry)) { |
1279 | dput(dentry); |
1280 | dentry = NULL; |
1281 | } |
1282 | } |
1283 | } |
1284 | } |
1285 | |
1286 | if (!dentry) { |
1287 | dentry = d_alloc(dir, name); |
1288 | if (unlikely(!dentry)) |
1289 | return ERR_PTR(-ENOMEM); |
1290 | |
1291 | *need_lookup = true; |
1292 | } |
1293 | return dentry; |
1294 | } |
1295 | |
1296 | /* |
1297 | * Call i_op->lookup on the dentry. The dentry must be negative but may be |
1298 | * hashed if it was pouplated with DCACHE_NEED_LOOKUP. |
1299 | * |
1300 | * dir->d_inode->i_mutex must be held |
1301 | */ |
1302 | static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry, |
1303 | unsigned int flags) |
1304 | { |
1305 | struct dentry *old; |
1306 | |
1307 | /* Don't create child dentry for a dead directory. */ |
1308 | if (unlikely(IS_DEADDIR(dir))) { |
1309 | dput(dentry); |
1310 | return ERR_PTR(-ENOENT); |
1311 | } |
1312 | |
1313 | old = dir->i_op->lookup(dir, dentry, flags); |
1314 | if (unlikely(old)) { |
1315 | dput(dentry); |
1316 | dentry = old; |
1317 | } |
1318 | return dentry; |
1319 | } |
1320 | |
1321 | static struct dentry *__lookup_hash(struct qstr *name, |
1322 | struct dentry *base, unsigned int flags) |
1323 | { |
1324 | bool need_lookup; |
1325 | struct dentry *dentry; |
1326 | |
1327 | dentry = lookup_dcache(name, base, flags, &need_lookup); |
1328 | if (!need_lookup) |
1329 | return dentry; |
1330 | |
1331 | return lookup_real(base->d_inode, dentry, flags); |
1332 | } |
1333 | |
1334 | /* |
1335 | * It's more convoluted than I'd like it to be, but... it's still fairly |
1336 | * small and for now I'd prefer to have fast path as straight as possible. |
1337 | * It _is_ time-critical. |
1338 | */ |
1339 | static int lookup_fast(struct nameidata *nd, |
1340 | struct path *path, struct inode **inode) |
1341 | { |
1342 | struct vfsmount *mnt = nd->path.mnt; |
1343 | struct dentry *dentry, *parent = nd->path.dentry; |
1344 | int need_reval = 1; |
1345 | int status = 1; |
1346 | int err; |
1347 | |
1348 | /* |
1349 | * Rename seqlock is not required here because in the off chance |
1350 | * of a false negative due to a concurrent rename, we're going to |
1351 | * do the non-racy lookup, below. |
1352 | */ |
1353 | if (nd->flags & LOOKUP_RCU) { |
1354 | unsigned seq; |
1355 | dentry = __d_lookup_rcu(parent, &nd->last, &seq, nd->inode); |
1356 | if (!dentry) |
1357 | goto unlazy; |
1358 | |
1359 | /* |
1360 | * This sequence count validates that the inode matches |
1361 | * the dentry name information from lookup. |
1362 | */ |
1363 | *inode = dentry->d_inode; |
1364 | if (read_seqcount_retry(&dentry->d_seq, seq)) |
1365 | return -ECHILD; |
1366 | |
1367 | /* |
1368 | * This sequence count validates that the parent had no |
1369 | * changes while we did the lookup of the dentry above. |
1370 | * |
1371 | * The memory barrier in read_seqcount_begin of child is |
1372 | * enough, we can use __read_seqcount_retry here. |
1373 | */ |
1374 | if (__read_seqcount_retry(&parent->d_seq, nd->seq)) |
1375 | return -ECHILD; |
1376 | nd->seq = seq; |
1377 | |
1378 | if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) { |
1379 | status = d_revalidate(dentry, nd->flags); |
1380 | if (unlikely(status <= 0)) { |
1381 | if (status != -ECHILD) |
1382 | need_reval = 0; |
1383 | goto unlazy; |
1384 | } |
1385 | } |
1386 | path->mnt = mnt; |
1387 | path->dentry = dentry; |
1388 | if (unlikely(!__follow_mount_rcu(nd, path, inode))) |
1389 | goto unlazy; |
1390 | if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT)) |
1391 | goto unlazy; |
1392 | return 0; |
1393 | unlazy: |
1394 | if (unlazy_walk(nd, dentry)) |
1395 | return -ECHILD; |
1396 | } else { |
1397 | dentry = __d_lookup(parent, &nd->last); |
1398 | } |
1399 | |
1400 | if (unlikely(!dentry)) |
1401 | goto need_lookup; |
1402 | |
1403 | if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE) && need_reval) |
1404 | status = d_revalidate(dentry, nd->flags); |
1405 | if (unlikely(status <= 0)) { |
1406 | if (status < 0) { |
1407 | dput(dentry); |
1408 | return status; |
1409 | } |
1410 | if (!d_invalidate(dentry)) { |
1411 | dput(dentry); |
1412 | goto need_lookup; |
1413 | } |
1414 | } |
1415 | |
1416 | path->mnt = mnt; |
1417 | path->dentry = dentry; |
1418 | err = follow_managed(path, nd->flags); |
1419 | if (unlikely(err < 0)) { |
1420 | path_put_conditional(path, nd); |
1421 | return err; |
1422 | } |
1423 | if (err) |
1424 | nd->flags |= LOOKUP_JUMPED; |
1425 | *inode = path->dentry->d_inode; |
1426 | return 0; |
1427 | |
1428 | need_lookup: |
1429 | return 1; |
1430 | } |
1431 | |
1432 | /* Fast lookup failed, do it the slow way */ |
1433 | static int lookup_slow(struct nameidata *nd, struct path *path) |
1434 | { |
1435 | struct dentry *dentry, *parent; |
1436 | int err; |
1437 | |
1438 | parent = nd->path.dentry; |
1439 | BUG_ON(nd->inode != parent->d_inode); |
1440 | |
1441 | mutex_lock(&parent->d_inode->i_mutex); |
1442 | dentry = __lookup_hash(&nd->last, parent, nd->flags); |
1443 | mutex_unlock(&parent->d_inode->i_mutex); |
1444 | if (IS_ERR(dentry)) |
1445 | return PTR_ERR(dentry); |
1446 | path->mnt = nd->path.mnt; |
1447 | path->dentry = dentry; |
1448 | err = follow_managed(path, nd->flags); |
1449 | if (unlikely(err < 0)) { |
1450 | path_put_conditional(path, nd); |
1451 | return err; |
1452 | } |
1453 | if (err) |
1454 | nd->flags |= LOOKUP_JUMPED; |
1455 | return 0; |
1456 | } |
1457 | |
1458 | static inline int may_lookup(struct nameidata *nd) |
1459 | { |
1460 | if (nd->flags & LOOKUP_RCU) { |
1461 | int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK); |
1462 | if (err != -ECHILD) |
1463 | return err; |
1464 | if (unlazy_walk(nd, NULL)) |
1465 | return -ECHILD; |
1466 | } |
1467 | return inode_permission(nd->inode, MAY_EXEC); |
1468 | } |
1469 | |
1470 | static inline int handle_dots(struct nameidata *nd, int type) |
1471 | { |
1472 | if (type == LAST_DOTDOT) { |
1473 | if (nd->flags & LOOKUP_RCU) { |
1474 | if (follow_dotdot_rcu(nd)) |
1475 | return -ECHILD; |
1476 | } else |
1477 | follow_dotdot(nd); |
1478 | } |
1479 | return 0; |
1480 | } |
1481 | |
1482 | static void terminate_walk(struct nameidata *nd) |
1483 | { |
1484 | if (!(nd->flags & LOOKUP_RCU)) { |
1485 | path_put(&nd->path); |
1486 | } else { |
1487 | nd->flags &= ~LOOKUP_RCU; |
1488 | if (!(nd->flags & LOOKUP_ROOT)) |
1489 | nd->root.mnt = NULL; |
1490 | unlock_rcu_walk(); |
1491 | } |
1492 | } |
1493 | |
1494 | /* |
1495 | * Do we need to follow links? We _really_ want to be able |
1496 | * to do this check without having to look at inode->i_op, |
1497 | * so we keep a cache of "no, this doesn't need follow_link" |
1498 | * for the common case. |
1499 | */ |
1500 | static inline int should_follow_link(struct inode *inode, int follow) |
1501 | { |
1502 | if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) { |
1503 | if (likely(inode->i_op->follow_link)) |
1504 | return follow; |
1505 | |
1506 | /* This gets set once for the inode lifetime */ |
1507 | spin_lock(&inode->i_lock); |
1508 | inode->i_opflags |= IOP_NOFOLLOW; |
1509 | spin_unlock(&inode->i_lock); |
1510 | } |
1511 | return 0; |
1512 | } |
1513 | |
1514 | static inline int walk_component(struct nameidata *nd, struct path *path, |
1515 | int follow) |
1516 | { |
1517 | struct inode *inode; |
1518 | int err; |
1519 | /* |
1520 | * "." and ".." are special - ".." especially so because it has |
1521 | * to be able to know about the current root directory and |
1522 | * parent relationships. |
1523 | */ |
1524 | if (unlikely(nd->last_type != LAST_NORM)) |
1525 | return handle_dots(nd, nd->last_type); |
1526 | err = lookup_fast(nd, path, &inode); |
1527 | if (unlikely(err)) { |
1528 | if (err < 0) |
1529 | goto out_err; |
1530 | |
1531 | err = lookup_slow(nd, path); |
1532 | if (err < 0) |
1533 | goto out_err; |
1534 | |
1535 | inode = path->dentry->d_inode; |
1536 | } |
1537 | err = -ENOENT; |
1538 | if (!inode) |
1539 | goto out_path_put; |
1540 | |
1541 | if (should_follow_link(inode, follow)) { |
1542 | if (nd->flags & LOOKUP_RCU) { |
1543 | if (unlikely(unlazy_walk(nd, path->dentry))) { |
1544 | err = -ECHILD; |
1545 | goto out_err; |
1546 | } |
1547 | } |
1548 | BUG_ON(inode != path->dentry->d_inode); |
1549 | return 1; |
1550 | } |
1551 | path_to_nameidata(path, nd); |
1552 | nd->inode = inode; |
1553 | return 0; |
1554 | |
1555 | out_path_put: |
1556 | path_to_nameidata(path, nd); |
1557 | out_err: |
1558 | terminate_walk(nd); |
1559 | return err; |
1560 | } |
1561 | |
1562 | /* |
1563 | * This limits recursive symlink follows to 8, while |
1564 | * limiting consecutive symlinks to 40. |
1565 | * |
1566 | * Without that kind of total limit, nasty chains of consecutive |
1567 | * symlinks can cause almost arbitrarily long lookups. |
1568 | */ |
1569 | static inline int nested_symlink(struct path *path, struct nameidata *nd) |
1570 | { |
1571 | int res; |
1572 | |
1573 | if (unlikely(current->link_count >= MAX_NESTED_LINKS)) { |
1574 | path_put_conditional(path, nd); |
1575 | path_put(&nd->path); |
1576 | return -ELOOP; |
1577 | } |
1578 | BUG_ON(nd->depth >= MAX_NESTED_LINKS); |
1579 | |
1580 | nd->depth++; |
1581 | current->link_count++; |
1582 | |
1583 | do { |
1584 | struct path link = *path; |
1585 | void *cookie; |
1586 | |
1587 | res = follow_link(&link, nd, &cookie); |
1588 | if (res) |
1589 | break; |
1590 | res = walk_component(nd, path, LOOKUP_FOLLOW); |
1591 | put_link(nd, &link, cookie); |
1592 | } while (res > 0); |
1593 | |
1594 | current->link_count--; |
1595 | nd->depth--; |
1596 | return res; |
1597 | } |
1598 | |
1599 | /* |
1600 | * We really don't want to look at inode->i_op->lookup |
1601 | * when we don't have to. So we keep a cache bit in |
1602 | * the inode ->i_opflags field that says "yes, we can |
1603 | * do lookup on this inode". |
1604 | */ |
1605 | static inline int can_lookup(struct inode *inode) |
1606 | { |
1607 | if (likely(inode->i_opflags & IOP_LOOKUP)) |
1608 | return 1; |
1609 | if (likely(!inode->i_op->lookup)) |
1610 | return 0; |
1611 | |
1612 | /* We do this once for the lifetime of the inode */ |
1613 | spin_lock(&inode->i_lock); |
1614 | inode->i_opflags |= IOP_LOOKUP; |
1615 | spin_unlock(&inode->i_lock); |
1616 | return 1; |
1617 | } |
1618 | |
1619 | /* |
1620 | * We can do the critical dentry name comparison and hashing |
1621 | * operations one word at a time, but we are limited to: |
1622 | * |
1623 | * - Architectures with fast unaligned word accesses. We could |
1624 | * do a "get_unaligned()" if this helps and is sufficiently |
1625 | * fast. |
1626 | * |
1627 | * - Little-endian machines (so that we can generate the mask |
1628 | * of low bytes efficiently). Again, we *could* do a byte |
1629 | * swapping load on big-endian architectures if that is not |
1630 | * expensive enough to make the optimization worthless. |
1631 | * |
1632 | * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we |
1633 | * do not trap on the (extremely unlikely) case of a page |
1634 | * crossing operation. |
1635 | * |
1636 | * - Furthermore, we need an efficient 64-bit compile for the |
1637 | * 64-bit case in order to generate the "number of bytes in |
1638 | * the final mask". Again, that could be replaced with a |
1639 | * efficient population count instruction or similar. |
1640 | */ |
1641 | #ifdef CONFIG_DCACHE_WORD_ACCESS |
1642 | |
1643 | #include <asm/word-at-a-time.h> |
1644 | |
1645 | #ifdef CONFIG_64BIT |
1646 | |
1647 | static inline unsigned int fold_hash(unsigned long hash) |
1648 | { |
1649 | hash += hash >> (8*sizeof(int)); |
1650 | return hash; |
1651 | } |
1652 | |
1653 | #else /* 32-bit case */ |
1654 | |
1655 | #define fold_hash(x) (x) |
1656 | |
1657 | #endif |
1658 | |
1659 | unsigned int full_name_hash(const unsigned char *name, unsigned int len) |
1660 | { |
1661 | unsigned long a, mask; |
1662 | unsigned long hash = 0; |
1663 | |
1664 | for (;;) { |
1665 | a = load_unaligned_zeropad(name); |
1666 | if (len < sizeof(unsigned long)) |
1667 | break; |
1668 | hash += a; |
1669 | hash *= 9; |
1670 | name += sizeof(unsigned long); |
1671 | len -= sizeof(unsigned long); |
1672 | if (!len) |
1673 | goto done; |
1674 | } |
1675 | mask = ~(~0ul << len*8); |
1676 | hash += mask & a; |
1677 | done: |
1678 | return fold_hash(hash); |
1679 | } |
1680 | EXPORT_SYMBOL(full_name_hash); |
1681 | |
1682 | /* |
1683 | * Calculate the length and hash of the path component, and |
1684 | * return the length of the component; |
1685 | */ |
1686 | static inline unsigned long hash_name(const char *name, unsigned int *hashp) |
1687 | { |
1688 | unsigned long a, b, adata, bdata, mask, hash, len; |
1689 | const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS; |
1690 | |
1691 | hash = a = 0; |
1692 | len = -sizeof(unsigned long); |
1693 | do { |
1694 | hash = (hash + a) * 9; |
1695 | len += sizeof(unsigned long); |
1696 | a = load_unaligned_zeropad(name+len); |
1697 | b = a ^ REPEAT_BYTE('/'); |
1698 | } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants))); |
1699 | |
1700 | adata = prep_zero_mask(a, adata, &constants); |
1701 | bdata = prep_zero_mask(b, bdata, &constants); |
1702 | |
1703 | mask = create_zero_mask(adata | bdata); |
1704 | |
1705 | hash += a & zero_bytemask(mask); |
1706 | *hashp = fold_hash(hash); |
1707 | |
1708 | return len + find_zero(mask); |
1709 | } |
1710 | |
1711 | #else |
1712 | |
1713 | unsigned int full_name_hash(const unsigned char *name, unsigned int len) |
1714 | { |
1715 | unsigned long hash = init_name_hash(); |
1716 | while (len--) |
1717 | hash = partial_name_hash(*name++, hash); |
1718 | return end_name_hash(hash); |
1719 | } |
1720 | EXPORT_SYMBOL(full_name_hash); |
1721 | |
1722 | /* |
1723 | * We know there's a real path component here of at least |
1724 | * one character. |
1725 | */ |
1726 | static inline unsigned long hash_name(const char *name, unsigned int *hashp) |
1727 | { |
1728 | unsigned long hash = init_name_hash(); |
1729 | unsigned long len = 0, c; |
1730 | |
1731 | c = (unsigned char)*name; |
1732 | do { |
1733 | len++; |
1734 | hash = partial_name_hash(c, hash); |
1735 | c = (unsigned char)name[len]; |
1736 | } while (c && c != '/'); |
1737 | *hashp = end_name_hash(hash); |
1738 | return len; |
1739 | } |
1740 | |
1741 | #endif |
1742 | |
1743 | /* |
1744 | * Name resolution. |
1745 | * This is the basic name resolution function, turning a pathname into |
1746 | * the final dentry. We expect 'base' to be positive and a directory. |
1747 | * |
1748 | * Returns 0 and nd will have valid dentry and mnt on success. |
1749 | * Returns error and drops reference to input namei data on failure. |
1750 | */ |
1751 | static int link_path_walk(const char *name, struct nameidata *nd) |
1752 | { |
1753 | struct path next; |
1754 | int err; |
1755 | |
1756 | while (*name=='/') |
1757 | name++; |
1758 | if (!*name) |
1759 | return 0; |
1760 | |
1761 | /* At this point we know we have a real path component. */ |
1762 | for(;;) { |
1763 | struct qstr this; |
1764 | long len; |
1765 | int type; |
1766 | |
1767 | err = may_lookup(nd); |
1768 | if (err) |
1769 | break; |
1770 | |
1771 | len = hash_name(name, &this.hash); |
1772 | this.name = name; |
1773 | this.len = len; |
1774 | |
1775 | type = LAST_NORM; |
1776 | if (name[0] == '.') switch (len) { |
1777 | case 2: |
1778 | if (name[1] == '.') { |
1779 | type = LAST_DOTDOT; |
1780 | nd->flags |= LOOKUP_JUMPED; |
1781 | } |
1782 | break; |
1783 | case 1: |
1784 | type = LAST_DOT; |
1785 | } |
1786 | if (likely(type == LAST_NORM)) { |
1787 | struct dentry *parent = nd->path.dentry; |
1788 | nd->flags &= ~LOOKUP_JUMPED; |
1789 | if (unlikely(parent->d_flags & DCACHE_OP_HASH)) { |
1790 | err = parent->d_op->d_hash(parent, nd->inode, |
1791 | &this); |
1792 | if (err < 0) |
1793 | break; |
1794 | } |
1795 | } |
1796 | |
1797 | nd->last = this; |
1798 | nd->last_type = type; |
1799 | |
1800 | if (!name[len]) |
1801 | return 0; |
1802 | /* |
1803 | * If it wasn't NUL, we know it was '/'. Skip that |
1804 | * slash, and continue until no more slashes. |
1805 | */ |
1806 | do { |
1807 | len++; |
1808 | } while (unlikely(name[len] == '/')); |
1809 | if (!name[len]) |
1810 | return 0; |
1811 | |
1812 | name += len; |
1813 | |
1814 | err = walk_component(nd, &next, LOOKUP_FOLLOW); |
1815 | if (err < 0) |
1816 | return err; |
1817 | |
1818 | if (err) { |
1819 | err = nested_symlink(&next, nd); |
1820 | if (err) |
1821 | return err; |
1822 | } |
1823 | if (!can_lookup(nd->inode)) { |
1824 | err = -ENOTDIR; |
1825 | break; |
1826 | } |
1827 | } |
1828 | terminate_walk(nd); |
1829 | return err; |
1830 | } |
1831 | |
1832 | static int path_init(int dfd, const char *name, unsigned int flags, |
1833 | struct nameidata *nd, struct file **fp) |
1834 | { |
1835 | int retval = 0; |
1836 | |
1837 | nd->last_type = LAST_ROOT; /* if there are only slashes... */ |
1838 | nd->flags = flags | LOOKUP_JUMPED; |
1839 | nd->depth = 0; |
1840 | if (flags & LOOKUP_ROOT) { |
1841 | struct inode *inode = nd->root.dentry->d_inode; |
1842 | if (*name) { |
1843 | if (!can_lookup(inode)) |
1844 | return -ENOTDIR; |
1845 | retval = inode_permission(inode, MAY_EXEC); |
1846 | if (retval) |
1847 | return retval; |
1848 | } |
1849 | nd->path = nd->root; |
1850 | nd->inode = inode; |
1851 | if (flags & LOOKUP_RCU) { |
1852 | lock_rcu_walk(); |
1853 | nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); |
1854 | } else { |
1855 | path_get(&nd->path); |
1856 | } |
1857 | return 0; |
1858 | } |
1859 | |
1860 | nd->root.mnt = NULL; |
1861 | |
1862 | if (*name=='/') { |
1863 | if (flags & LOOKUP_RCU) { |
1864 | lock_rcu_walk(); |
1865 | set_root_rcu(nd); |
1866 | } else { |
1867 | set_root(nd); |
1868 | path_get(&nd->root); |
1869 | } |
1870 | nd->path = nd->root; |
1871 | } else if (dfd == AT_FDCWD) { |
1872 | if (flags & LOOKUP_RCU) { |
1873 | struct fs_struct *fs = current->fs; |
1874 | unsigned seq; |
1875 | |
1876 | lock_rcu_walk(); |
1877 | |
1878 | do { |
1879 | seq = read_seqcount_begin(&fs->seq); |
1880 | nd->path = fs->pwd; |
1881 | nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); |
1882 | } while (read_seqcount_retry(&fs->seq, seq)); |
1883 | } else { |
1884 | get_fs_pwd(current->fs, &nd->path); |
1885 | } |
1886 | } else { |
1887 | /* Caller must check execute permissions on the starting path component */ |
1888 | struct fd f = fdget_raw(dfd); |
1889 | struct dentry *dentry; |
1890 | |
1891 | if (!f.file) |
1892 | return -EBADF; |
1893 | |
1894 | dentry = f.file->f_path.dentry; |
1895 | |
1896 | if (*name) { |
1897 | if (!can_lookup(dentry->d_inode)) { |
1898 | fdput(f); |
1899 | return -ENOTDIR; |
1900 | } |
1901 | } |
1902 | |
1903 | nd->path = f.file->f_path; |
1904 | if (flags & LOOKUP_RCU) { |
1905 | if (f.need_put) |
1906 | *fp = f.file; |
1907 | nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); |
1908 | lock_rcu_walk(); |
1909 | } else { |
1910 | path_get(&nd->path); |
1911 | fdput(f); |
1912 | } |
1913 | } |
1914 | |
1915 | nd->inode = nd->path.dentry->d_inode; |
1916 | return 0; |
1917 | } |
1918 | |
1919 | static inline int lookup_last(struct nameidata *nd, struct path *path) |
1920 | { |
1921 | if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len]) |
1922 | nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; |
1923 | |
1924 | nd->flags &= ~LOOKUP_PARENT; |
1925 | return walk_component(nd, path, nd->flags & LOOKUP_FOLLOW); |
1926 | } |
1927 | |
1928 | /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */ |
1929 | static int path_lookupat(int dfd, const char *name, |
1930 | unsigned int flags, struct nameidata *nd) |
1931 | { |
1932 | struct file *base = NULL; |
1933 | struct path path; |
1934 | int err; |
1935 | |
1936 | /* |
1937 | * Path walking is largely split up into 2 different synchronisation |
1938 | * schemes, rcu-walk and ref-walk (explained in |
1939 | * Documentation/filesystems/path-lookup.txt). These share much of the |
1940 | * path walk code, but some things particularly setup, cleanup, and |
1941 | * following mounts are sufficiently divergent that functions are |
1942 | * duplicated. Typically there is a function foo(), and its RCU |
1943 | * analogue, foo_rcu(). |
1944 | * |
1945 | * -ECHILD is the error number of choice (just to avoid clashes) that |
1946 | * is returned if some aspect of an rcu-walk fails. Such an error must |
1947 | * be handled by restarting a traditional ref-walk (which will always |
1948 | * be able to complete). |
1949 | */ |
1950 | err = path_init(dfd, name, flags | LOOKUP_PARENT, nd, &base); |
1951 | |
1952 | if (unlikely(err)) |
1953 | return err; |
1954 | |
1955 | current->total_link_count = 0; |
1956 | err = link_path_walk(name, nd); |
1957 | |
1958 | if (!err && !(flags & LOOKUP_PARENT)) { |
1959 | err = lookup_last(nd, &path); |
1960 | while (err > 0) { |
1961 | void *cookie; |
1962 | struct path link = path; |
1963 | err = may_follow_link(&link, nd); |
1964 | if (unlikely(err)) |
1965 | break; |
1966 | nd->flags |= LOOKUP_PARENT; |
1967 | err = follow_link(&link, nd, &cookie); |
1968 | if (err) |
1969 | break; |
1970 | err = lookup_last(nd, &path); |
1971 | put_link(nd, &link, cookie); |
1972 | } |
1973 | } |
1974 | |
1975 | if (!err) |
1976 | err = complete_walk(nd); |
1977 | |
1978 | if (!err && nd->flags & LOOKUP_DIRECTORY) { |
1979 | if (!nd->inode->i_op->lookup) { |
1980 | path_put(&nd->path); |
1981 | err = -ENOTDIR; |
1982 | } |
1983 | } |
1984 | |
1985 | if (base) |
1986 | fput(base); |
1987 | |
1988 | if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) { |
1989 | path_put(&nd->root); |
1990 | nd->root.mnt = NULL; |
1991 | } |
1992 | return err; |
1993 | } |
1994 | |
1995 | static int filename_lookup(int dfd, struct filename *name, |
1996 | unsigned int flags, struct nameidata *nd) |
1997 | { |
1998 | int retval = path_lookupat(dfd, name->name, flags | LOOKUP_RCU, nd); |
1999 | if (unlikely(retval == -ECHILD)) |
2000 | retval = path_lookupat(dfd, name->name, flags, nd); |
2001 | if (unlikely(retval == -ESTALE)) |
2002 | retval = path_lookupat(dfd, name->name, |
2003 | flags | LOOKUP_REVAL, nd); |
2004 | |
2005 | if (likely(!retval)) |
2006 | audit_inode(name, nd->path.dentry, flags & LOOKUP_PARENT); |
2007 | return retval; |
2008 | } |
2009 | |
2010 | static int do_path_lookup(int dfd, const char *name, |
2011 | unsigned int flags, struct nameidata *nd) |
2012 | { |
2013 | struct filename filename = { .name = name }; |
2014 | |
2015 | return filename_lookup(dfd, &filename, flags, nd); |
2016 | } |
2017 | |
2018 | /* does lookup, returns the object with parent locked */ |
2019 | struct dentry *kern_path_locked(const char *name, struct path *path) |
2020 | { |
2021 | struct nameidata nd; |
2022 | struct dentry *d; |
2023 | int err = do_path_lookup(AT_FDCWD, name, LOOKUP_PARENT, &nd); |
2024 | if (err) |
2025 | return ERR_PTR(err); |
2026 | if (nd.last_type != LAST_NORM) { |
2027 | path_put(&nd.path); |
2028 | return ERR_PTR(-EINVAL); |
2029 | } |
2030 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); |
2031 | d = __lookup_hash(&nd.last, nd.path.dentry, 0); |
2032 | if (IS_ERR(d)) { |
2033 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); |
2034 | path_put(&nd.path); |
2035 | return d; |
2036 | } |
2037 | *path = nd.path; |
2038 | return d; |
2039 | } |
2040 | |
2041 | int kern_path(const char *name, unsigned int flags, struct path *path) |
2042 | { |
2043 | struct nameidata nd; |
2044 | int res = do_path_lookup(AT_FDCWD, name, flags, &nd); |
2045 | if (!res) |
2046 | *path = nd.path; |
2047 | return res; |
2048 | } |
2049 | |
2050 | /** |
2051 | * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair |
2052 | * @dentry: pointer to dentry of the base directory |
2053 | * @mnt: pointer to vfs mount of the base directory |
2054 | * @name: pointer to file name |
2055 | * @flags: lookup flags |
2056 | * @path: pointer to struct path to fill |
2057 | */ |
2058 | int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt, |
2059 | const char *name, unsigned int flags, |
2060 | struct path *path) |
2061 | { |
2062 | struct nameidata nd; |
2063 | int err; |
2064 | nd.root.dentry = dentry; |
2065 | nd.root.mnt = mnt; |
2066 | BUG_ON(flags & LOOKUP_PARENT); |
2067 | /* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */ |
2068 | err = do_path_lookup(AT_FDCWD, name, flags | LOOKUP_ROOT, &nd); |
2069 | if (!err) |
2070 | *path = nd.path; |
2071 | return err; |
2072 | } |
2073 | |
2074 | /* |
2075 | * Restricted form of lookup. Doesn't follow links, single-component only, |
2076 | * needs parent already locked. Doesn't follow mounts. |
2077 | * SMP-safe. |
2078 | */ |
2079 | static struct dentry *lookup_hash(struct nameidata *nd) |
2080 | { |
2081 | return __lookup_hash(&nd->last, nd->path.dentry, nd->flags); |
2082 | } |
2083 | |
2084 | /** |
2085 | * lookup_one_len - filesystem helper to lookup single pathname component |
2086 | * @name: pathname component to lookup |
2087 | * @base: base directory to lookup from |
2088 | * @len: maximum length @len should be interpreted to |
2089 | * |
2090 | * Note that this routine is purely a helper for filesystem usage and should |
2091 | * not be called by generic code. Also note that by using this function the |
2092 | * nameidata argument is passed to the filesystem methods and a filesystem |
2093 | * using this helper needs to be prepared for that. |
2094 | */ |
2095 | struct dentry *lookup_one_len(const char *name, struct dentry *base, int len) |
2096 | { |
2097 | struct qstr this; |
2098 | unsigned int c; |
2099 | int err; |
2100 | |
2101 | WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex)); |
2102 | |
2103 | this.name = name; |
2104 | this.len = len; |
2105 | this.hash = full_name_hash(name, len); |
2106 | if (!len) |
2107 | return ERR_PTR(-EACCES); |
2108 | |
2109 | if (unlikely(name[0] == '.')) { |
2110 | if (len < 2 || (len == 2 && name[1] == '.')) |
2111 | return ERR_PTR(-EACCES); |
2112 | } |
2113 | |
2114 | while (len--) { |
2115 | c = *(const unsigned char *)name++; |
2116 | if (c == '/' || c == '\0') |
2117 | return ERR_PTR(-EACCES); |
2118 | } |
2119 | /* |
2120 | * See if the low-level filesystem might want |
2121 | * to use its own hash.. |
2122 | */ |
2123 | if (base->d_flags & DCACHE_OP_HASH) { |
2124 | int err = base->d_op->d_hash(base, base->d_inode, &this); |
2125 | if (err < 0) |
2126 | return ERR_PTR(err); |
2127 | } |
2128 | |
2129 | err = inode_permission(base->d_inode, MAY_EXEC); |
2130 | if (err) |
2131 | return ERR_PTR(err); |
2132 | |
2133 | return __lookup_hash(&this, base, 0); |
2134 | } |
2135 | |
2136 | int user_path_at_empty(int dfd, const char __user *name, unsigned flags, |
2137 | struct path *path, int *empty) |
2138 | { |
2139 | struct nameidata nd; |
2140 | struct filename *tmp = getname_flags(name, flags, empty); |
2141 | int err = PTR_ERR(tmp); |
2142 | if (!IS_ERR(tmp)) { |
2143 | |
2144 | BUG_ON(flags & LOOKUP_PARENT); |
2145 | |
2146 | err = filename_lookup(dfd, tmp, flags, &nd); |
2147 | putname(tmp); |
2148 | if (!err) |
2149 | *path = nd.path; |
2150 | } |
2151 | return err; |
2152 | } |
2153 | |
2154 | int user_path_at(int dfd, const char __user *name, unsigned flags, |
2155 | struct path *path) |
2156 | { |
2157 | return user_path_at_empty(dfd, name, flags, path, NULL); |
2158 | } |
2159 | |
2160 | /* |
2161 | * NB: most callers don't do anything directly with the reference to the |
2162 | * to struct filename, but the nd->last pointer points into the name string |
2163 | * allocated by getname. So we must hold the reference to it until all |
2164 | * path-walking is complete. |
2165 | */ |
2166 | static struct filename * |
2167 | user_path_parent(int dfd, const char __user *path, struct nameidata *nd, |
2168 | unsigned int flags) |
2169 | { |
2170 | struct filename *s = getname(path); |
2171 | int error; |
2172 | |
2173 | /* only LOOKUP_REVAL is allowed in extra flags */ |
2174 | flags &= LOOKUP_REVAL; |
2175 | |
2176 | if (IS_ERR(s)) |
2177 | return s; |
2178 | |
2179 | error = filename_lookup(dfd, s, flags | LOOKUP_PARENT, nd); |
2180 | if (error) { |
2181 | putname(s); |
2182 | return ERR_PTR(error); |
2183 | } |
2184 | |
2185 | return s; |
2186 | } |
2187 | |
2188 | /* |
2189 | * It's inline, so penalty for filesystems that don't use sticky bit is |
2190 | * minimal. |
2191 | */ |
2192 | static inline int check_sticky(struct inode *dir, struct inode *inode) |
2193 | { |
2194 | kuid_t fsuid = current_fsuid(); |
2195 | |
2196 | if (!(dir->i_mode & S_ISVTX)) |
2197 | return 0; |
2198 | if (uid_eq(inode->i_uid, fsuid)) |
2199 | return 0; |
2200 | if (uid_eq(dir->i_uid, fsuid)) |
2201 | return 0; |
2202 | return !inode_capable(inode, CAP_FOWNER); |
2203 | } |
2204 | |
2205 | /* |
2206 | * Check whether we can remove a link victim from directory dir, check |
2207 | * whether the type of victim is right. |
2208 | * 1. We can't do it if dir is read-only (done in permission()) |
2209 | * 2. We should have write and exec permissions on dir |
2210 | * 3. We can't remove anything from append-only dir |
2211 | * 4. We can't do anything with immutable dir (done in permission()) |
2212 | * 5. If the sticky bit on dir is set we should either |
2213 | * a. be owner of dir, or |
2214 | * b. be owner of victim, or |
2215 | * c. have CAP_FOWNER capability |
2216 | * 6. If the victim is append-only or immutable we can't do antyhing with |
2217 | * links pointing to it. |
2218 | * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR. |
2219 | * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR. |
2220 | * 9. We can't remove a root or mountpoint. |
2221 | * 10. We don't allow removal of NFS sillyrenamed files; it's handled by |
2222 | * nfs_async_unlink(). |
2223 | */ |
2224 | static int may_delete(struct inode *dir,struct dentry *victim,int isdir) |
2225 | { |
2226 | int error; |
2227 | |
2228 | if (!victim->d_inode) |
2229 | return -ENOENT; |
2230 | |
2231 | BUG_ON(victim->d_parent->d_inode != dir); |
2232 | audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE); |
2233 | |
2234 | error = inode_permission(dir, MAY_WRITE | MAY_EXEC); |
2235 | if (error) |
2236 | return error; |
2237 | if (IS_APPEND(dir)) |
2238 | return -EPERM; |
2239 | if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)|| |
2240 | IS_IMMUTABLE(victim->d_inode) || IS_SWAPFILE(victim->d_inode)) |
2241 | return -EPERM; |
2242 | if (isdir) { |
2243 | if (!S_ISDIR(victim->d_inode->i_mode)) |
2244 | return -ENOTDIR; |
2245 | if (IS_ROOT(victim)) |
2246 | return -EBUSY; |
2247 | } else if (S_ISDIR(victim->d_inode->i_mode)) |
2248 | return -EISDIR; |
2249 | if (IS_DEADDIR(dir)) |
2250 | return -ENOENT; |
2251 | if (victim->d_flags & DCACHE_NFSFS_RENAMED) |
2252 | return -EBUSY; |
2253 | return 0; |
2254 | } |
2255 | |
2256 | /* Check whether we can create an object with dentry child in directory |
2257 | * dir. |
2258 | * 1. We can't do it if child already exists (open has special treatment for |
2259 | * this case, but since we are inlined it's OK) |
2260 | * 2. We can't do it if dir is read-only (done in permission()) |
2261 | * 3. We should have write and exec permissions on dir |
2262 | * 4. We can't do it if dir is immutable (done in permission()) |
2263 | */ |
2264 | static inline int may_create(struct inode *dir, struct dentry *child) |
2265 | { |
2266 | if (child->d_inode) |
2267 | return -EEXIST; |
2268 | if (IS_DEADDIR(dir)) |
2269 | return -ENOENT; |
2270 | return inode_permission(dir, MAY_WRITE | MAY_EXEC); |
2271 | } |
2272 | |
2273 | /* |
2274 | * p1 and p2 should be directories on the same fs. |
2275 | */ |
2276 | struct dentry *lock_rename(struct dentry *p1, struct dentry *p2) |
2277 | { |
2278 | struct dentry *p; |
2279 | |
2280 | if (p1 == p2) { |
2281 | mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT); |
2282 | return NULL; |
2283 | } |
2284 | |
2285 | mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex); |
2286 | |
2287 | p = d_ancestor(p2, p1); |
2288 | if (p) { |
2289 | mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT); |
2290 | mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD); |
2291 | return p; |
2292 | } |
2293 | |
2294 | p = d_ancestor(p1, p2); |
2295 | if (p) { |
2296 | mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT); |
2297 | mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD); |
2298 | return p; |
2299 | } |
2300 | |
2301 | mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT); |
2302 | mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD); |
2303 | return NULL; |
2304 | } |
2305 | |
2306 | void unlock_rename(struct dentry *p1, struct dentry *p2) |
2307 | { |
2308 | mutex_unlock(&p1->d_inode->i_mutex); |
2309 | if (p1 != p2) { |
2310 | mutex_unlock(&p2->d_inode->i_mutex); |
2311 | mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex); |
2312 | } |
2313 | } |
2314 | |
2315 | int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, |
2316 | bool want_excl) |
2317 | { |
2318 | int error = may_create(dir, dentry); |
2319 | if (error) |
2320 | return error; |
2321 | |
2322 | if (!dir->i_op->create) |
2323 | return -EACCES; /* shouldn't it be ENOSYS? */ |
2324 | mode &= S_IALLUGO; |
2325 | mode |= S_IFREG; |
2326 | error = security_inode_create(dir, dentry, mode); |
2327 | if (error) |
2328 | return error; |
2329 | error = dir->i_op->create(dir, dentry, mode, want_excl); |
2330 | if (!error) |
2331 | fsnotify_create(dir, dentry); |
2332 | return error; |
2333 | } |
2334 | |
2335 | static int may_open(struct path *path, int acc_mode, int flag) |
2336 | { |
2337 | struct dentry *dentry = path->dentry; |
2338 | struct inode *inode = dentry->d_inode; |
2339 | int error; |
2340 | |
2341 | /* O_PATH? */ |
2342 | if (!acc_mode) |
2343 | return 0; |
2344 | |
2345 | if (!inode) |
2346 | return -ENOENT; |
2347 | |
2348 | switch (inode->i_mode & S_IFMT) { |
2349 | case S_IFLNK: |
2350 | return -ELOOP; |
2351 | case S_IFDIR: |
2352 | if (acc_mode & MAY_WRITE) |
2353 | return -EISDIR; |
2354 | break; |
2355 | case S_IFBLK: |
2356 | case S_IFCHR: |
2357 | if (path->mnt->mnt_flags & MNT_NODEV) |
2358 | return -EACCES; |
2359 | /*FALLTHRU*/ |
2360 | case S_IFIFO: |
2361 | case S_IFSOCK: |
2362 | flag &= ~O_TRUNC; |
2363 | break; |
2364 | } |
2365 | |
2366 | error = inode_permission(inode, acc_mode); |
2367 | if (error) |
2368 | return error; |
2369 | |
2370 | /* |
2371 | * An append-only file must be opened in append mode for writing. |
2372 | */ |
2373 | if (IS_APPEND(inode)) { |
2374 | if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND)) |
2375 | return -EPERM; |
2376 | if (flag & O_TRUNC) |
2377 | return -EPERM; |
2378 | } |
2379 | |
2380 | /* O_NOATIME can only be set by the owner or superuser */ |
2381 | if (flag & O_NOATIME && !inode_owner_or_capable(inode)) |
2382 | return -EPERM; |
2383 | |
2384 | return 0; |
2385 | } |
2386 | |
2387 | static int handle_truncate(struct file *filp) |
2388 | { |
2389 | struct path *path = &filp->f_path; |
2390 | struct inode *inode = path->dentry->d_inode; |
2391 | int error = get_write_access(inode); |
2392 | if (error) |
2393 | return error; |
2394 | /* |
2395 | * Refuse to truncate files with mandatory locks held on them. |
2396 | */ |
2397 | error = locks_verify_locked(inode); |
2398 | if (!error) |
2399 | error = security_path_truncate(path); |
2400 | if (!error) { |
2401 | error = do_truncate(path->dentry, 0, |
2402 | ATTR_MTIME|ATTR_CTIME|ATTR_OPEN, |
2403 | filp); |
2404 | } |
2405 | put_write_access(inode); |
2406 | return error; |
2407 | } |
2408 | |
2409 | static inline int open_to_namei_flags(int flag) |
2410 | { |
2411 | if ((flag & O_ACCMODE) == 3) |
2412 | flag--; |
2413 | return flag; |
2414 | } |
2415 | |
2416 | static int may_o_create(struct path *dir, struct dentry *dentry, umode_t mode) |
2417 | { |
2418 | int error = security_path_mknod(dir, dentry, mode, 0); |
2419 | if (error) |
2420 | return error; |
2421 | |
2422 | error = inode_permission(dir->dentry->d_inode, MAY_WRITE | MAY_EXEC); |
2423 | if (error) |
2424 | return error; |
2425 | |
2426 | return security_inode_create(dir->dentry->d_inode, dentry, mode); |
2427 | } |
2428 | |
2429 | /* |
2430 | * Attempt to atomically look up, create and open a file from a negative |
2431 | * dentry. |
2432 | * |
2433 | * Returns 0 if successful. The file will have been created and attached to |
2434 | * @file by the filesystem calling finish_open(). |
2435 | * |
2436 | * Returns 1 if the file was looked up only or didn't need creating. The |
2437 | * caller will need to perform the open themselves. @path will have been |
2438 | * updated to point to the new dentry. This may be negative. |
2439 | * |
2440 | * Returns an error code otherwise. |
2441 | */ |
2442 | static int atomic_open(struct nameidata *nd, struct dentry *dentry, |
2443 | struct path *path, struct file *file, |
2444 | const struct open_flags *op, |
2445 | bool got_write, bool need_lookup, |
2446 | int *opened) |
2447 | { |
2448 | struct inode *dir = nd->path.dentry->d_inode; |
2449 | unsigned open_flag = open_to_namei_flags(op->open_flag); |
2450 | umode_t mode; |
2451 | int error; |
2452 | int acc_mode; |
2453 | int create_error = 0; |
2454 | struct dentry *const DENTRY_NOT_SET = (void *) -1UL; |
2455 | |
2456 | BUG_ON(dentry->d_inode); |
2457 | |
2458 | /* Don't create child dentry for a dead directory. */ |
2459 | if (unlikely(IS_DEADDIR(dir))) { |
2460 | error = -ENOENT; |
2461 | goto out; |
2462 | } |
2463 | |
2464 | mode = op->mode; |
2465 | if ((open_flag & O_CREAT) && !IS_POSIXACL(dir)) |
2466 | mode &= ~current_umask(); |
2467 | |
2468 | if ((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT)) { |
2469 | open_flag &= ~O_TRUNC; |
2470 | *opened |= FILE_CREATED; |
2471 | } |
2472 | |
2473 | /* |
2474 | * Checking write permission is tricky, bacuse we don't know if we are |
2475 | * going to actually need it: O_CREAT opens should work as long as the |
2476 | * file exists. But checking existence breaks atomicity. The trick is |
2477 | * to check access and if not granted clear O_CREAT from the flags. |
2478 | * |
2479 | * Another problem is returing the "right" error value (e.g. for an |
2480 | * O_EXCL open we want to return EEXIST not EROFS). |
2481 | */ |
2482 | if (((open_flag & (O_CREAT | O_TRUNC)) || |
2483 | (open_flag & O_ACCMODE) != O_RDONLY) && unlikely(!got_write)) { |
2484 | if (!(open_flag & O_CREAT)) { |
2485 | /* |
2486 | * No O_CREATE -> atomicity not a requirement -> fall |
2487 | * back to lookup + open |
2488 | */ |
2489 | goto no_open; |
2490 | } else if (open_flag & (O_EXCL | O_TRUNC)) { |
2491 | /* Fall back and fail with the right error */ |
2492 | create_error = -EROFS; |
2493 | goto no_open; |
2494 | } else { |
2495 | /* No side effects, safe to clear O_CREAT */ |
2496 | create_error = -EROFS; |
2497 | open_flag &= ~O_CREAT; |
2498 | } |
2499 | } |
2500 | |
2501 | if (open_flag & O_CREAT) { |
2502 | error = may_o_create(&nd->path, dentry, mode); |
2503 | if (error) { |
2504 | create_error = error; |
2505 | if (open_flag & O_EXCL) |
2506 | goto no_open; |
2507 | open_flag &= ~O_CREAT; |
2508 | } |
2509 | } |
2510 | |
2511 | if (nd->flags & LOOKUP_DIRECTORY) |
2512 | open_flag |= O_DIRECTORY; |
2513 | |
2514 | file->f_path.dentry = DENTRY_NOT_SET; |
2515 | file->f_path.mnt = nd->path.mnt; |
2516 | error = dir->i_op->atomic_open(dir, dentry, file, open_flag, mode, |
2517 | opened); |
2518 | if (error < 0) { |
2519 | if (create_error && error == -ENOENT) |
2520 | error = create_error; |
2521 | goto out; |
2522 | } |
2523 | |
2524 | acc_mode = op->acc_mode; |
2525 | if (*opened & FILE_CREATED) { |
2526 | fsnotify_create(dir, dentry); |
2527 | acc_mode = MAY_OPEN; |
2528 | } |
2529 | |
2530 | if (error) { /* returned 1, that is */ |
2531 | if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) { |
2532 | error = -EIO; |
2533 | goto out; |
2534 | } |
2535 | if (file->f_path.dentry) { |
2536 | dput(dentry); |
2537 | dentry = file->f_path.dentry; |
2538 | } |
2539 | if (create_error && dentry->d_inode == NULL) { |
2540 | error = create_error; |
2541 | goto out; |
2542 | } |
2543 | goto looked_up; |
2544 | } |
2545 | |
2546 | /* |
2547 | * We didn't have the inode before the open, so check open permission |
2548 | * here. |
2549 | */ |
2550 | error = may_open(&file->f_path, acc_mode, open_flag); |
2551 | if (error) |
2552 | fput(file); |
2553 | |
2554 | out: |
2555 | dput(dentry); |
2556 | return error; |
2557 | |
2558 | no_open: |
2559 | if (need_lookup) { |
2560 | dentry = lookup_real(dir, dentry, nd->flags); |
2561 | if (IS_ERR(dentry)) |
2562 | return PTR_ERR(dentry); |
2563 | |
2564 | if (create_error) { |
2565 | int open_flag = op->open_flag; |
2566 | |
2567 | error = create_error; |
2568 | if ((open_flag & O_EXCL)) { |
2569 | if (!dentry->d_inode) |
2570 | goto out; |
2571 | } else if (!dentry->d_inode) { |
2572 | goto out; |
2573 | } else if ((open_flag & O_TRUNC) && |
2574 | S_ISREG(dentry->d_inode->i_mode)) { |
2575 | goto out; |
2576 | } |
2577 | /* will fail later, go on to get the right error */ |
2578 | } |
2579 | } |
2580 | looked_up: |
2581 | path->dentry = dentry; |
2582 | path->mnt = nd->path.mnt; |
2583 | return 1; |
2584 | } |
2585 | |
2586 | /* |
2587 | * Look up and maybe create and open the last component. |
2588 | * |
2589 | * Must be called with i_mutex held on parent. |
2590 | * |
2591 | * Returns 0 if the file was successfully atomically created (if necessary) and |
2592 | * opened. In this case the file will be returned attached to @file. |
2593 | * |
2594 | * Returns 1 if the file was not completely opened at this time, though lookups |
2595 | * and creations will have been performed and the dentry returned in @path will |
2596 | * be positive upon return if O_CREAT was specified. If O_CREAT wasn't |
2597 | * specified then a negative dentry may be returned. |
2598 | * |
2599 | * An error code is returned otherwise. |
2600 | * |
2601 | * FILE_CREATE will be set in @*opened if the dentry was created and will be |
2602 | * cleared otherwise prior to returning. |
2603 | */ |
2604 | static int lookup_open(struct nameidata *nd, struct path *path, |
2605 | struct file *file, |
2606 | const struct open_flags *op, |
2607 | bool got_write, int *opened) |
2608 | { |
2609 | struct dentry *dir = nd->path.dentry; |
2610 | struct inode *dir_inode = dir->d_inode; |
2611 | struct dentry *dentry; |
2612 | int error; |
2613 | bool need_lookup; |
2614 | |
2615 | *opened &= ~FILE_CREATED; |
2616 | dentry = lookup_dcache(&nd->last, dir, nd->flags, &need_lookup); |
2617 | if (IS_ERR(dentry)) |
2618 | return PTR_ERR(dentry); |
2619 | |
2620 | /* Cached positive dentry: will open in f_op->open */ |
2621 | if (!need_lookup && dentry->d_inode) |
2622 | goto out_no_open; |
2623 | |
2624 | if ((nd->flags & LOOKUP_OPEN) && dir_inode->i_op->atomic_open) { |
2625 | return atomic_open(nd, dentry, path, file, op, got_write, |
2626 | need_lookup, opened); |
2627 | } |
2628 | |
2629 | if (need_lookup) { |
2630 | BUG_ON(dentry->d_inode); |
2631 | |
2632 | dentry = lookup_real(dir_inode, dentry, nd->flags); |
2633 | if (IS_ERR(dentry)) |
2634 | return PTR_ERR(dentry); |
2635 | } |
2636 | |
2637 | /* Negative dentry, just create the file */ |
2638 | if (!dentry->d_inode && (op->open_flag & O_CREAT)) { |
2639 | umode_t mode = op->mode; |
2640 | if (!IS_POSIXACL(dir->d_inode)) |
2641 | mode &= ~current_umask(); |
2642 | /* |
2643 | * This write is needed to ensure that a |
2644 | * rw->ro transition does not occur between |
2645 | * the time when the file is created and when |
2646 | * a permanent write count is taken through |
2647 | * the 'struct file' in finish_open(). |
2648 | */ |
2649 | if (!got_write) { |
2650 | error = -EROFS; |
2651 | goto out_dput; |
2652 | } |
2653 | *opened |= FILE_CREATED; |
2654 | error = security_path_mknod(&nd->path, dentry, mode, 0); |
2655 | if (error) |
2656 | goto out_dput; |
2657 | error = vfs_create(dir->d_inode, dentry, mode, |
2658 | nd->flags & LOOKUP_EXCL); |
2659 | if (error) |
2660 | goto out_dput; |
2661 | } |
2662 | out_no_open: |
2663 | path->dentry = dentry; |
2664 | path->mnt = nd->path.mnt; |
2665 | return 1; |
2666 | |
2667 | out_dput: |
2668 | dput(dentry); |
2669 | return error; |
2670 | } |
2671 | |
2672 | /* |
2673 | * Handle the last step of open() |
2674 | */ |
2675 | static int do_last(struct nameidata *nd, struct path *path, |
2676 | struct file *file, const struct open_flags *op, |
2677 | int *opened, struct filename *name) |
2678 | { |
2679 | struct dentry *dir = nd->path.dentry; |
2680 | int open_flag = op->open_flag; |
2681 | bool will_truncate = (open_flag & O_TRUNC) != 0; |
2682 | bool got_write = false; |
2683 | int acc_mode = op->acc_mode; |
2684 | struct inode *inode; |
2685 | bool symlink_ok = false; |
2686 | struct path save_parent = { .dentry = NULL, .mnt = NULL }; |
2687 | bool retried = false; |
2688 | int error; |
2689 | |
2690 | nd->flags &= ~LOOKUP_PARENT; |
2691 | nd->flags |= op->intent; |
2692 | |
2693 | switch (nd->last_type) { |
2694 | case LAST_DOTDOT: |
2695 | case LAST_DOT: |
2696 | error = handle_dots(nd, nd->last_type); |
2697 | if (error) |
2698 | return error; |
2699 | /* fallthrough */ |
2700 | case LAST_ROOT: |
2701 | error = complete_walk(nd); |
2702 | if (error) |
2703 | return error; |
2704 | audit_inode(name, nd->path.dentry, 0); |
2705 | if (open_flag & O_CREAT) { |
2706 | error = -EISDIR; |
2707 | goto out; |
2708 | } |
2709 | goto finish_open; |
2710 | case LAST_BIND: |
2711 | error = complete_walk(nd); |
2712 | if (error) |
2713 | return error; |
2714 | audit_inode(name, dir, 0); |
2715 | goto finish_open; |
2716 | } |
2717 | |
2718 | if (!(open_flag & O_CREAT)) { |
2719 | if (nd->last.name[nd->last.len]) |
2720 | nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; |
2721 | if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW)) |
2722 | symlink_ok = true; |
2723 | /* we _can_ be in RCU mode here */ |
2724 | error = lookup_fast(nd, path, &inode); |
2725 | if (likely(!error)) |
2726 | goto finish_lookup; |
2727 | |
2728 | if (error < 0) |
2729 | goto out; |
2730 | |
2731 | BUG_ON(nd->inode != dir->d_inode); |
2732 | } else { |
2733 | /* create side of things */ |
2734 | /* |
2735 | * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED |
2736 | * has been cleared when we got to the last component we are |
2737 | * about to look up |
2738 | */ |
2739 | error = complete_walk(nd); |
2740 | if (error) |
2741 | return error; |
2742 | |
2743 | audit_inode(name, dir, 0); |
2744 | error = -EISDIR; |
2745 | /* trailing slashes? */ |
2746 | if (nd->last.name[nd->last.len]) |
2747 | goto out; |
2748 | } |
2749 | |
2750 | retry_lookup: |
2751 | if (op->open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) { |
2752 | error = mnt_want_write(nd->path.mnt); |
2753 | if (!error) |
2754 | got_write = true; |
2755 | /* |
2756 | * do _not_ fail yet - we might not need that or fail with |
2757 | * a different error; let lookup_open() decide; we'll be |
2758 | * dropping this one anyway. |
2759 | */ |
2760 | } |
2761 | mutex_lock(&dir->d_inode->i_mutex); |
2762 | error = lookup_open(nd, path, file, op, got_write, opened); |
2763 | mutex_unlock(&dir->d_inode->i_mutex); |
2764 | |
2765 | if (error <= 0) { |
2766 | if (error) |
2767 | goto out; |
2768 | |
2769 | if ((*opened & FILE_CREATED) || |
2770 | !S_ISREG(file_inode(file)->i_mode)) |
2771 | will_truncate = false; |
2772 | |
2773 | audit_inode(name, file->f_path.dentry, 0); |
2774 | goto opened; |
2775 | } |
2776 | |
2777 | if (*opened & FILE_CREATED) { |
2778 | /* Don't check for write permission, don't truncate */ |
2779 | open_flag &= ~O_TRUNC; |
2780 | will_truncate = false; |
2781 | acc_mode = MAY_OPEN; |
2782 | path_to_nameidata(path, nd); |
2783 | goto finish_open_created; |
2784 | } |
2785 | |
2786 | /* |
2787 | * create/update audit record if it already exists. |
2788 | */ |
2789 | if (path->dentry->d_inode) |
2790 | audit_inode(name, path->dentry, 0); |
2791 | |
2792 | /* |
2793 | * If atomic_open() acquired write access it is dropped now due to |
2794 | * possible mount and symlink following (this might be optimized away if |
2795 | * necessary...) |
2796 | */ |
2797 | if (got_write) { |
2798 | mnt_drop_write(nd->path.mnt); |
2799 | got_write = false; |
2800 | } |
2801 | |
2802 | error = -EEXIST; |
2803 | if ((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT)) |
2804 | goto exit_dput; |
2805 | |
2806 | error = follow_managed(path, nd->flags); |
2807 | if (error < 0) |
2808 | goto exit_dput; |
2809 | |
2810 | if (error) |
2811 | nd->flags |= LOOKUP_JUMPED; |
2812 | |
2813 | BUG_ON(nd->flags & LOOKUP_RCU); |
2814 | inode = path->dentry->d_inode; |
2815 | finish_lookup: |
2816 | /* we _can_ be in RCU mode here */ |
2817 | error = -ENOENT; |
2818 | if (!inode) { |
2819 | path_to_nameidata(path, nd); |
2820 | goto out; |
2821 | } |
2822 | |
2823 | if (should_follow_link(inode, !symlink_ok)) { |
2824 | if (nd->flags & LOOKUP_RCU) { |
2825 | if (unlikely(unlazy_walk(nd, path->dentry))) { |
2826 | error = -ECHILD; |
2827 | goto out; |
2828 | } |
2829 | } |
2830 | BUG_ON(inode != path->dentry->d_inode); |
2831 | return 1; |
2832 | } |
2833 | |
2834 | if ((nd->flags & LOOKUP_RCU) || nd->path.mnt != path->mnt) { |
2835 | path_to_nameidata(path, nd); |
2836 | } else { |
2837 | save_parent.dentry = nd->path.dentry; |
2838 | save_parent.mnt = mntget(path->mnt); |
2839 | nd->path.dentry = path->dentry; |
2840 | |
2841 | } |
2842 | nd->inode = inode; |
2843 | /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */ |
2844 | error = complete_walk(nd); |
2845 | if (error) { |
2846 | path_put(&save_parent); |
2847 | return error; |
2848 | } |
2849 | error = -EISDIR; |
2850 | if ((open_flag & O_CREAT) && S_ISDIR(nd->inode->i_mode)) |
2851 | goto out; |
2852 | error = -ENOTDIR; |
2853 | if ((nd->flags & LOOKUP_DIRECTORY) && !nd->inode->i_op->lookup) |
2854 | goto out; |
2855 | audit_inode(name, nd->path.dentry, 0); |
2856 | finish_open: |
2857 | if (!S_ISREG(nd->inode->i_mode)) |
2858 | will_truncate = false; |
2859 | |
2860 | if (will_truncate) { |
2861 | error = mnt_want_write(nd->path.mnt); |
2862 | if (error) |
2863 | goto out; |
2864 | got_write = true; |
2865 | } |
2866 | finish_open_created: |
2867 | error = may_open(&nd->path, acc_mode, open_flag); |
2868 | if (error) |
2869 | goto out; |
2870 | file->f_path.mnt = nd->path.mnt; |
2871 | error = finish_open(file, nd->path.dentry, NULL, opened); |
2872 | if (error) { |
2873 | if (error == -EOPENSTALE) |
2874 | goto stale_open; |
2875 | goto out; |
2876 | } |
2877 | opened: |
2878 | error = open_check_o_direct(file); |
2879 | if (error) |
2880 | goto exit_fput; |
2881 | error = ima_file_check(file, op->acc_mode); |
2882 | if (error) |
2883 | goto exit_fput; |
2884 | |
2885 | if (will_truncate) { |
2886 | error = handle_truncate(file); |
2887 | if (error) |
2888 | goto exit_fput; |
2889 | } |
2890 | out: |
2891 | if (got_write) |
2892 | mnt_drop_write(nd->path.mnt); |
2893 | path_put(&save_parent); |
2894 | terminate_walk(nd); |
2895 | return error; |
2896 | |
2897 | exit_dput: |
2898 | path_put_conditional(path, nd); |
2899 | goto out; |
2900 | exit_fput: |
2901 | fput(file); |
2902 | goto out; |
2903 | |
2904 | stale_open: |
2905 | /* If no saved parent or already retried then can't retry */ |
2906 | if (!save_parent.dentry || retried) |
2907 | goto out; |
2908 | |
2909 | BUG_ON(save_parent.dentry != dir); |
2910 | path_put(&nd->path); |
2911 | nd->path = save_parent; |
2912 | nd->inode = dir->d_inode; |
2913 | save_parent.mnt = NULL; |
2914 | save_parent.dentry = NULL; |
2915 | if (got_write) { |
2916 | mnt_drop_write(nd->path.mnt); |
2917 | got_write = false; |
2918 | } |
2919 | retried = true; |
2920 | goto retry_lookup; |
2921 | } |
2922 | |
2923 | static struct file *path_openat(int dfd, struct filename *pathname, |
2924 | struct nameidata *nd, const struct open_flags *op, int flags) |
2925 | { |
2926 | struct file *base = NULL; |
2927 | struct file *file; |
2928 | struct path path; |
2929 | int opened = 0; |
2930 | int error; |
2931 | |
2932 | file = get_empty_filp(); |
2933 | if (IS_ERR(file)) |
2934 | return file; |
2935 | |
2936 | file->f_flags = op->open_flag; |
2937 | |
2938 | error = path_init(dfd, pathname->name, flags | LOOKUP_PARENT, nd, &base); |
2939 | if (unlikely(error)) |
2940 | goto out; |
2941 | |
2942 | current->total_link_count = 0; |
2943 | error = link_path_walk(pathname->name, nd); |
2944 | if (unlikely(error)) |
2945 | goto out; |
2946 | |
2947 | error = do_last(nd, &path, file, op, &opened, pathname); |
2948 | while (unlikely(error > 0)) { /* trailing symlink */ |
2949 | struct path link = path; |
2950 | void *cookie; |
2951 | if (!(nd->flags & LOOKUP_FOLLOW)) { |
2952 | path_put_conditional(&path, nd); |
2953 | path_put(&nd->path); |
2954 | error = -ELOOP; |
2955 | break; |
2956 | } |
2957 | error = may_follow_link(&link, nd); |
2958 | if (unlikely(error)) |
2959 | break; |
2960 | nd->flags |= LOOKUP_PARENT; |
2961 | nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL); |
2962 | error = follow_link(&link, nd, &cookie); |
2963 | if (unlikely(error)) |
2964 | break; |
2965 | error = do_last(nd, &path, file, op, &opened, pathname); |
2966 | put_link(nd, &link, cookie); |
2967 | } |
2968 | out: |
2969 | if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) |
2970 | path_put(&nd->root); |
2971 | if (base) |
2972 | fput(base); |
2973 | if (!(opened & FILE_OPENED)) { |
2974 | BUG_ON(!error); |
2975 | put_filp(file); |
2976 | } |
2977 | if (unlikely(error)) { |
2978 | if (error == -EOPENSTALE) { |
2979 | if (flags & LOOKUP_RCU) |
2980 | error = -ECHILD; |
2981 | else |
2982 | error = -ESTALE; |
2983 | } |
2984 | file = ERR_PTR(error); |
2985 | } |
2986 | return file; |
2987 | } |
2988 | |
2989 | struct file *do_filp_open(int dfd, struct filename *pathname, |
2990 | const struct open_flags *op, int flags) |
2991 | { |
2992 | struct nameidata nd; |
2993 | struct file *filp; |
2994 | |
2995 | filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_RCU); |
2996 | if (unlikely(filp == ERR_PTR(-ECHILD))) |
2997 | filp = path_openat(dfd, pathname, &nd, op, flags); |
2998 | if (unlikely(filp == ERR_PTR(-ESTALE))) |
2999 | filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_REVAL); |
3000 | return filp; |
3001 | } |
3002 | |
3003 | struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt, |
3004 | const char *name, const struct open_flags *op, int flags) |
3005 | { |
3006 | struct nameidata nd; |
3007 | struct file *file; |
3008 | struct filename filename = { .name = name }; |
3009 | |
3010 | nd.root.mnt = mnt; |
3011 | nd.root.dentry = dentry; |
3012 | |
3013 | flags |= LOOKUP_ROOT; |
3014 | |
3015 | if (dentry->d_inode->i_op->follow_link && op->intent & LOOKUP_OPEN) |
3016 | return ERR_PTR(-ELOOP); |
3017 | |
3018 | file = path_openat(-1, &filename, &nd, op, flags | LOOKUP_RCU); |
3019 | if (unlikely(file == ERR_PTR(-ECHILD))) |
3020 | file = path_openat(-1, &filename, &nd, op, flags); |
3021 | if (unlikely(file == ERR_PTR(-ESTALE))) |
3022 | file = path_openat(-1, &filename, &nd, op, flags | LOOKUP_REVAL); |
3023 | return file; |
3024 | } |
3025 | |
3026 | struct dentry *kern_path_create(int dfd, const char *pathname, |
3027 | struct path *path, unsigned int lookup_flags) |
3028 | { |
3029 | struct dentry *dentry = ERR_PTR(-EEXIST); |
3030 | struct nameidata nd; |
3031 | int err2; |
3032 | int error; |
3033 | bool is_dir = (lookup_flags & LOOKUP_DIRECTORY); |
3034 | |
3035 | /* |
3036 | * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any |
3037 | * other flags passed in are ignored! |
3038 | */ |
3039 | lookup_flags &= LOOKUP_REVAL; |
3040 | |
3041 | error = do_path_lookup(dfd, pathname, LOOKUP_PARENT|lookup_flags, &nd); |
3042 | if (error) |
3043 | return ERR_PTR(error); |
3044 | |
3045 | /* |
3046 | * Yucky last component or no last component at all? |
3047 | * (foo/., foo/.., /////) |
3048 | */ |
3049 | if (nd.last_type != LAST_NORM) |
3050 | goto out; |
3051 | nd.flags &= ~LOOKUP_PARENT; |
3052 | nd.flags |= LOOKUP_CREATE | LOOKUP_EXCL; |
3053 | |
3054 | /* don't fail immediately if it's r/o, at least try to report other errors */ |
3055 | err2 = mnt_want_write(nd.path.mnt); |
3056 | /* |
3057 | * Do the final lookup. |
3058 | */ |
3059 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); |
3060 | dentry = lookup_hash(&nd); |
3061 | if (IS_ERR(dentry)) |
3062 | goto unlock; |
3063 | |
3064 | error = -EEXIST; |
3065 | if (dentry->d_inode) |
3066 | goto fail; |
3067 | /* |
3068 | * Special case - lookup gave negative, but... we had foo/bar/ |
3069 | * From the vfs_mknod() POV we just have a negative dentry - |
3070 | * all is fine. Let's be bastards - you had / on the end, you've |
3071 | * been asking for (non-existent) directory. -ENOENT for you. |
3072 | */ |
3073 | if (unlikely(!is_dir && nd.last.name[nd.last.len])) { |
3074 | error = -ENOENT; |
3075 | goto fail; |
3076 | } |
3077 | if (unlikely(err2)) { |
3078 | error = err2; |
3079 | goto fail; |
3080 | } |
3081 | *path = nd.path; |
3082 | return dentry; |
3083 | fail: |
3084 | dput(dentry); |
3085 | dentry = ERR_PTR(error); |
3086 | unlock: |
3087 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); |
3088 | if (!err2) |
3089 | mnt_drop_write(nd.path.mnt); |
3090 | out: |
3091 | path_put(&nd.path); |
3092 | return dentry; |
3093 | } |
3094 | EXPORT_SYMBOL(kern_path_create); |
3095 | |
3096 | void done_path_create(struct path *path, struct dentry *dentry) |
3097 | { |
3098 | dput(dentry); |
3099 | mutex_unlock(&path->dentry->d_inode->i_mutex); |
3100 | mnt_drop_write(path->mnt); |
3101 | path_put(path); |
3102 | } |
3103 | EXPORT_SYMBOL(done_path_create); |
3104 | |
3105 | struct dentry *user_path_create(int dfd, const char __user *pathname, |
3106 | struct path *path, unsigned int lookup_flags) |
3107 | { |
3108 | struct filename *tmp = getname(pathname); |
3109 | struct dentry *res; |
3110 | if (IS_ERR(tmp)) |
3111 | return ERR_CAST(tmp); |
3112 | res = kern_path_create(dfd, tmp->name, path, lookup_flags); |
3113 | putname(tmp); |
3114 | return res; |
3115 | } |
3116 | EXPORT_SYMBOL(user_path_create); |
3117 | |
3118 | int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev) |
3119 | { |
3120 | int error = may_create(dir, dentry); |
3121 | |
3122 | if (error) |
3123 | return error; |
3124 | |
3125 | if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD)) |
3126 | return -EPERM; |
3127 | |
3128 | if (!dir->i_op->mknod) |
3129 | return -EPERM; |
3130 | |
3131 | error = devcgroup_inode_mknod(mode, dev); |
3132 | if (error) |
3133 | return error; |
3134 | |
3135 | error = security_inode_mknod(dir, dentry, mode, dev); |
3136 | if (error) |
3137 | return error; |
3138 | |
3139 | error = dir->i_op->mknod(dir, dentry, mode, dev); |
3140 | if (!error) |
3141 | fsnotify_create(dir, dentry); |
3142 | return error; |
3143 | } |
3144 | |
3145 | static int may_mknod(umode_t mode) |
3146 | { |
3147 | switch (mode & S_IFMT) { |
3148 | case S_IFREG: |
3149 | case S_IFCHR: |
3150 | case S_IFBLK: |
3151 | case S_IFIFO: |
3152 | case S_IFSOCK: |
3153 | case 0: /* zero mode translates to S_IFREG */ |
3154 | return 0; |
3155 | case S_IFDIR: |
3156 | return -EPERM; |
3157 | default: |
3158 | return -EINVAL; |
3159 | } |
3160 | } |
3161 | |
3162 | SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode, |
3163 | unsigned, dev) |
3164 | { |
3165 | struct dentry *dentry; |
3166 | struct path path; |
3167 | int error; |
3168 | unsigned int lookup_flags = 0; |
3169 | |
3170 | error = may_mknod(mode); |
3171 | if (error) |
3172 | return error; |
3173 | retry: |
3174 | dentry = user_path_create(dfd, filename, &path, lookup_flags); |
3175 | if (IS_ERR(dentry)) |
3176 | return PTR_ERR(dentry); |
3177 | |
3178 | if (!IS_POSIXACL(path.dentry->d_inode)) |
3179 | mode &= ~current_umask(); |
3180 | error = security_path_mknod(&path, dentry, mode, dev); |
3181 | if (error) |
3182 | goto out; |
3183 | switch (mode & S_IFMT) { |
3184 | case 0: case S_IFREG: |
3185 | error = vfs_create(path.dentry->d_inode,dentry,mode,true); |
3186 | break; |
3187 | case S_IFCHR: case S_IFBLK: |
3188 | error = vfs_mknod(path.dentry->d_inode,dentry,mode, |
3189 | new_decode_dev(dev)); |
3190 | break; |
3191 | case S_IFIFO: case S_IFSOCK: |
3192 | error = vfs_mknod(path.dentry->d_inode,dentry,mode,0); |
3193 | break; |
3194 | } |
3195 | out: |
3196 | done_path_create(&path, dentry); |
3197 | if (retry_estale(error, lookup_flags)) { |
3198 | lookup_flags |= LOOKUP_REVAL; |
3199 | goto retry; |
3200 | } |
3201 | return error; |
3202 | } |
3203 | |
3204 | SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev) |
3205 | { |
3206 | return sys_mknodat(AT_FDCWD, filename, mode, dev); |
3207 | } |
3208 | |
3209 | int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode) |
3210 | { |
3211 | int error = may_create(dir, dentry); |
3212 | unsigned max_links = dir->i_sb->s_max_links; |
3213 | |
3214 | if (error) |
3215 | return error; |
3216 | |
3217 | if (!dir->i_op->mkdir) |
3218 | return -EPERM; |
3219 | |
3220 | mode &= (S_IRWXUGO|S_ISVTX); |
3221 | error = security_inode_mkdir(dir, dentry, mode); |
3222 | if (error) |
3223 | return error; |
3224 | |
3225 | if (max_links && dir->i_nlink >= max_links) |
3226 | return -EMLINK; |
3227 | |
3228 | error = dir->i_op->mkdir(dir, dentry, mode); |
3229 | if (!error) |
3230 | fsnotify_mkdir(dir, dentry); |
3231 | return error; |
3232 | } |
3233 | |
3234 | SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode) |
3235 | { |
3236 | struct dentry *dentry; |
3237 | struct path path; |
3238 | int error; |
3239 | unsigned int lookup_flags = LOOKUP_DIRECTORY; |
3240 | |
3241 | retry: |
3242 | dentry = user_path_create(dfd, pathname, &path, lookup_flags); |
3243 | if (IS_ERR(dentry)) |
3244 | return PTR_ERR(dentry); |
3245 | |
3246 | if (!IS_POSIXACL(path.dentry->d_inode)) |
3247 | mode &= ~current_umask(); |
3248 | error = security_path_mkdir(&path, dentry, mode); |
3249 | if (!error) |
3250 | error = vfs_mkdir(path.dentry->d_inode, dentry, mode); |
3251 | done_path_create(&path, dentry); |
3252 | if (retry_estale(error, lookup_flags)) { |
3253 | lookup_flags |= LOOKUP_REVAL; |
3254 | goto retry; |
3255 | } |
3256 | return error; |
3257 | } |
3258 | |
3259 | SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode) |
3260 | { |
3261 | return sys_mkdirat(AT_FDCWD, pathname, mode); |
3262 | } |
3263 | |
3264 | /* |
3265 | * The dentry_unhash() helper will try to drop the dentry early: we |
3266 | * should have a usage count of 1 if we're the only user of this |
3267 | * dentry, and if that is true (possibly after pruning the dcache), |
3268 | * then we drop the dentry now. |
3269 | * |
3270 | * A low-level filesystem can, if it choses, legally |
3271 | * do a |
3272 | * |
3273 | * if (!d_unhashed(dentry)) |
3274 | * return -EBUSY; |
3275 | * |
3276 | * if it cannot handle the case of removing a directory |
3277 | * that is still in use by something else.. |
3278 | */ |
3279 | void dentry_unhash(struct dentry *dentry) |
3280 | { |
3281 | shrink_dcache_parent(dentry); |
3282 | spin_lock(&dentry->d_lock); |
3283 | if (dentry->d_count == 1) |
3284 | __d_drop(dentry); |
3285 | spin_unlock(&dentry->d_lock); |
3286 | } |
3287 | |
3288 | int vfs_rmdir(struct inode *dir, struct dentry *dentry) |
3289 | { |
3290 | int error = may_delete(dir, dentry, 1); |
3291 | |
3292 | if (error) |
3293 | return error; |
3294 | |
3295 | if (!dir->i_op->rmdir) |
3296 | return -EPERM; |
3297 | |
3298 | dget(dentry); |
3299 | mutex_lock(&dentry->d_inode->i_mutex); |
3300 | |
3301 | error = -EBUSY; |
3302 | if (d_mountpoint(dentry)) |
3303 | goto out; |
3304 | |
3305 | error = security_inode_rmdir(dir, dentry); |
3306 | if (error) |
3307 | goto out; |
3308 | |
3309 | shrink_dcache_parent(dentry); |
3310 | error = dir->i_op->rmdir(dir, dentry); |
3311 | if (error) |
3312 | goto out; |
3313 | |
3314 | dentry->d_inode->i_flags |= S_DEAD; |
3315 | dont_mount(dentry); |
3316 | |
3317 | out: |
3318 | mutex_unlock(&dentry->d_inode->i_mutex); |
3319 | dput(dentry); |
3320 | if (!error) |
3321 | d_delete(dentry); |
3322 | return error; |
3323 | } |
3324 | |
3325 | static long do_rmdir(int dfd, const char __user *pathname) |
3326 | { |
3327 | int error = 0; |
3328 | struct filename *name; |
3329 | struct dentry *dentry; |
3330 | struct nameidata nd; |
3331 | unsigned int lookup_flags = 0; |
3332 | retry: |
3333 | name = user_path_parent(dfd, pathname, &nd, lookup_flags); |
3334 | if (IS_ERR(name)) |
3335 | return PTR_ERR(name); |
3336 | |
3337 | switch(nd.last_type) { |
3338 | case LAST_DOTDOT: |
3339 | error = -ENOTEMPTY; |
3340 | goto exit1; |
3341 | case LAST_DOT: |
3342 | error = -EINVAL; |
3343 | goto exit1; |
3344 | case LAST_ROOT: |
3345 | error = -EBUSY; |
3346 | goto exit1; |
3347 | } |
3348 | |
3349 | nd.flags &= ~LOOKUP_PARENT; |
3350 | error = mnt_want_write(nd.path.mnt); |
3351 | if (error) |
3352 | goto exit1; |
3353 | |
3354 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); |
3355 | dentry = lookup_hash(&nd); |
3356 | error = PTR_ERR(dentry); |
3357 | if (IS_ERR(dentry)) |
3358 | goto exit2; |
3359 | if (!dentry->d_inode) { |
3360 | error = -ENOENT; |
3361 | goto exit3; |
3362 | } |
3363 | error = security_path_rmdir(&nd.path, dentry); |
3364 | if (error) |
3365 | goto exit3; |
3366 | error = vfs_rmdir(nd.path.dentry->d_inode, dentry); |
3367 | exit3: |
3368 | dput(dentry); |
3369 | exit2: |
3370 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); |
3371 | mnt_drop_write(nd.path.mnt); |
3372 | exit1: |
3373 | path_put(&nd.path); |
3374 | putname(name); |
3375 | if (retry_estale(error, lookup_flags)) { |
3376 | lookup_flags |= LOOKUP_REVAL; |
3377 | goto retry; |
3378 | } |
3379 | return error; |
3380 | } |
3381 | |
3382 | SYSCALL_DEFINE1(rmdir, const char __user *, pathname) |
3383 | { |
3384 | return do_rmdir(AT_FDCWD, pathname); |
3385 | } |
3386 | |
3387 | int vfs_unlink(struct inode *dir, struct dentry *dentry) |
3388 | { |
3389 | int error = may_delete(dir, dentry, 0); |
3390 | |
3391 | if (error) |
3392 | return error; |
3393 | |
3394 | if (!dir->i_op->unlink) |
3395 | return -EPERM; |
3396 | |
3397 | mutex_lock(&dentry->d_inode->i_mutex); |
3398 | if (d_mountpoint(dentry)) |
3399 | error = -EBUSY; |
3400 | else { |
3401 | error = security_inode_unlink(dir, dentry); |
3402 | if (!error) { |
3403 | error = dir->i_op->unlink(dir, dentry); |
3404 | if (!error) |
3405 | dont_mount(dentry); |
3406 | } |
3407 | } |
3408 | mutex_unlock(&dentry->d_inode->i_mutex); |
3409 | |
3410 | /* We don't d_delete() NFS sillyrenamed files--they still exist. */ |
3411 | if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) { |
3412 | fsnotify_link_count(dentry->d_inode); |
3413 | d_delete(dentry); |
3414 | } |
3415 | |
3416 | return error; |
3417 | } |
3418 | |
3419 | /* |
3420 | * Make sure that the actual truncation of the file will occur outside its |
3421 | * directory's i_mutex. Truncate can take a long time if there is a lot of |
3422 | * writeout happening, and we don't want to prevent access to the directory |
3423 | * while waiting on the I/O. |
3424 | */ |
3425 | static long do_unlinkat(int dfd, const char __user *pathname) |
3426 | { |
3427 | int error; |
3428 | struct filename *name; |
3429 | struct dentry *dentry; |
3430 | struct nameidata nd; |
3431 | struct inode *inode = NULL; |
3432 | unsigned int lookup_flags = 0; |
3433 | retry: |
3434 | name = user_path_parent(dfd, pathname, &nd, lookup_flags); |
3435 | if (IS_ERR(name)) |
3436 | return PTR_ERR(name); |
3437 | |
3438 | error = -EISDIR; |
3439 | if (nd.last_type != LAST_NORM) |
3440 | goto exit1; |
3441 | |
3442 | nd.flags &= ~LOOKUP_PARENT; |
3443 | error = mnt_want_write(nd.path.mnt); |
3444 | if (error) |
3445 | goto exit1; |
3446 | |
3447 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); |
3448 | dentry = lookup_hash(&nd); |
3449 | error = PTR_ERR(dentry); |
3450 | if (!IS_ERR(dentry)) { |
3451 | /* Why not before? Because we want correct error value */ |
3452 | if (nd.last.name[nd.last.len]) |
3453 | goto slashes; |
3454 | inode = dentry->d_inode; |
3455 | if (!inode) |
3456 | goto slashes; |
3457 | ihold(inode); |
3458 | error = security_path_unlink(&nd.path, dentry); |
3459 | if (error) |
3460 | goto exit2; |
3461 | error = vfs_unlink(nd.path.dentry->d_inode, dentry); |
3462 | exit2: |
3463 | dput(dentry); |
3464 | } |
3465 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); |
3466 | if (inode) |
3467 | iput(inode); /* truncate the inode here */ |
3468 | mnt_drop_write(nd.path.mnt); |
3469 | exit1: |
3470 | path_put(&nd.path); |
3471 | putname(name); |
3472 | if (retry_estale(error, lookup_flags)) { |
3473 | lookup_flags |= LOOKUP_REVAL; |
3474 | inode = NULL; |
3475 | goto retry; |
3476 | } |
3477 | return error; |
3478 | |
3479 | slashes: |
3480 | error = !dentry->d_inode ? -ENOENT : |
3481 | S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR; |
3482 | goto exit2; |
3483 | } |
3484 | |
3485 | SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag) |
3486 | { |
3487 | if ((flag & ~AT_REMOVEDIR) != 0) |
3488 | return -EINVAL; |
3489 | |
3490 | if (flag & AT_REMOVEDIR) |
3491 | return do_rmdir(dfd, pathname); |
3492 | |
3493 | return do_unlinkat(dfd, pathname); |
3494 | } |
3495 | |
3496 | SYSCALL_DEFINE1(unlink, const char __user *, pathname) |
3497 | { |
3498 | return do_unlinkat(AT_FDCWD, pathname); |
3499 | } |
3500 | |
3501 | int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname) |
3502 | { |
3503 | int error = may_create(dir, dentry); |
3504 | |
3505 | if (error) |
3506 | return error; |
3507 | |
3508 | if (!dir->i_op->symlink) |
3509 | return -EPERM; |
3510 | |
3511 | error = security_inode_symlink(dir, dentry, oldname); |
3512 | if (error) |
3513 | return error; |
3514 | |
3515 | error = dir->i_op->symlink(dir, dentry, oldname); |
3516 | if (!error) |
3517 | fsnotify_create(dir, dentry); |
3518 | return error; |
3519 | } |
3520 | |
3521 | SYSCALL_DEFINE3(symlinkat, const char __user *, oldname, |
3522 | int, newdfd, const char __user *, newname) |
3523 | { |
3524 | int error; |
3525 | struct filename *from; |
3526 | struct dentry *dentry; |
3527 | struct path path; |
3528 | unsigned int lookup_flags = 0; |
3529 | |
3530 | from = getname(oldname); |
3531 | if (IS_ERR(from)) |
3532 | return PTR_ERR(from); |
3533 | retry: |
3534 | dentry = user_path_create(newdfd, newname, &path, lookup_flags); |
3535 | error = PTR_ERR(dentry); |
3536 | if (IS_ERR(dentry)) |
3537 | goto out_putname; |
3538 | |
3539 | error = security_path_symlink(&path, dentry, from->name); |
3540 | if (!error) |
3541 | error = vfs_symlink(path.dentry->d_inode, dentry, from->name); |
3542 | done_path_create(&path, dentry); |
3543 | if (retry_estale(error, lookup_flags)) { |
3544 | lookup_flags |= LOOKUP_REVAL; |
3545 | goto retry; |
3546 | } |
3547 | out_putname: |
3548 | putname(from); |
3549 | return error; |
3550 | } |
3551 | |
3552 | SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname) |
3553 | { |
3554 | return sys_symlinkat(oldname, AT_FDCWD, newname); |
3555 | } |
3556 | |
3557 | int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry) |
3558 | { |
3559 | struct inode *inode = old_dentry->d_inode; |
3560 | unsigned max_links = dir->i_sb->s_max_links; |
3561 | int error; |
3562 | |
3563 | if (!inode) |
3564 | return -ENOENT; |
3565 | |
3566 | error = may_create(dir, new_dentry); |
3567 | if (error) |
3568 | return error; |
3569 | |
3570 | if (dir->i_sb != inode->i_sb) |
3571 | return -EXDEV; |
3572 | |
3573 | /* |
3574 | * A link to an append-only or immutable file cannot be created. |
3575 | */ |
3576 | if (IS_APPEND(inode) || IS_IMMUTABLE(inode)) |
3577 | return -EPERM; |
3578 | if (!dir->i_op->link) |
3579 | return -EPERM; |
3580 | if (S_ISDIR(inode->i_mode)) |
3581 | return -EPERM; |
3582 | |
3583 | error = security_inode_link(old_dentry, dir, new_dentry); |
3584 | if (error) |
3585 | return error; |
3586 | |
3587 | mutex_lock(&inode->i_mutex); |
3588 | /* Make sure we don't allow creating hardlink to an unlinked file */ |
3589 | if (inode->i_nlink == 0) |
3590 | error = -ENOENT; |
3591 | else if (max_links && inode->i_nlink >= max_links) |
3592 | error = -EMLINK; |
3593 | else |
3594 | error = dir->i_op->link(old_dentry, dir, new_dentry); |
3595 | mutex_unlock(&inode->i_mutex); |
3596 | if (!error) |
3597 | fsnotify_link(dir, inode, new_dentry); |
3598 | return error; |
3599 | } |
3600 | |
3601 | /* |
3602 | * Hardlinks are often used in delicate situations. We avoid |
3603 | * security-related surprises by not following symlinks on the |
3604 | * newname. --KAB |
3605 | * |
3606 | * We don't follow them on the oldname either to be compatible |
3607 | * with linux 2.0, and to avoid hard-linking to directories |
3608 | * and other special files. --ADM |
3609 | */ |
3610 | SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname, |
3611 | int, newdfd, const char __user *, newname, int, flags) |
3612 | { |
3613 | struct dentry *new_dentry; |
3614 | struct path old_path, new_path; |
3615 | int how = 0; |
3616 | int error; |
3617 | |
3618 | if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0) |
3619 | return -EINVAL; |
3620 | /* |
3621 | * To use null names we require CAP_DAC_READ_SEARCH |
3622 | * This ensures that not everyone will be able to create |
3623 | * handlink using the passed filedescriptor. |
3624 | */ |
3625 | if (flags & AT_EMPTY_PATH) { |
3626 | if (!capable(CAP_DAC_READ_SEARCH)) |
3627 | return -ENOENT; |
3628 | how = LOOKUP_EMPTY; |
3629 | } |
3630 | |
3631 | if (flags & AT_SYMLINK_FOLLOW) |
3632 | how |= LOOKUP_FOLLOW; |
3633 | retry: |
3634 | error = user_path_at(olddfd, oldname, how, &old_path); |
3635 | if (error) |
3636 | return error; |
3637 | |
3638 | new_dentry = user_path_create(newdfd, newname, &new_path, |
3639 | (how & LOOKUP_REVAL)); |
3640 | error = PTR_ERR(new_dentry); |
3641 | if (IS_ERR(new_dentry)) |
3642 | goto out; |
3643 | |
3644 | error = -EXDEV; |
3645 | if (old_path.mnt != new_path.mnt) |
3646 | goto out_dput; |
3647 | error = may_linkat(&old_path); |
3648 | if (unlikely(error)) |
3649 | goto out_dput; |
3650 | error = security_path_link(old_path.dentry, &new_path, new_dentry); |
3651 | if (error) |
3652 | goto out_dput; |
3653 | error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry); |
3654 | out_dput: |
3655 | done_path_create(&new_path, new_dentry); |
3656 | if (retry_estale(error, how)) { |
3657 | how |= LOOKUP_REVAL; |
3658 | goto retry; |
3659 | } |
3660 | out: |
3661 | path_put(&old_path); |
3662 | |
3663 | return error; |
3664 | } |
3665 | |
3666 | SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname) |
3667 | { |
3668 | return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0); |
3669 | } |
3670 | |
3671 | /* |
3672 | * The worst of all namespace operations - renaming directory. "Perverted" |
3673 | * doesn't even start to describe it. Somebody in UCB had a heck of a trip... |
3674 | * Problems: |
3675 | * a) we can get into loop creation. Check is done in is_subdir(). |
3676 | * b) race potential - two innocent renames can create a loop together. |
3677 | * That's where 4.4 screws up. Current fix: serialization on |
3678 | * sb->s_vfs_rename_mutex. We might be more accurate, but that's another |
3679 | * story. |
3680 | * c) we have to lock _three_ objects - parents and victim (if it exists). |
3681 | * And that - after we got ->i_mutex on parents (until then we don't know |
3682 | * whether the target exists). Solution: try to be smart with locking |
3683 | * order for inodes. We rely on the fact that tree topology may change |
3684 | * only under ->s_vfs_rename_mutex _and_ that parent of the object we |
3685 | * move will be locked. Thus we can rank directories by the tree |
3686 | * (ancestors first) and rank all non-directories after them. |
3687 | * That works since everybody except rename does "lock parent, lookup, |
3688 | * lock child" and rename is under ->s_vfs_rename_mutex. |
3689 | * HOWEVER, it relies on the assumption that any object with ->lookup() |
3690 | * has no more than 1 dentry. If "hybrid" objects will ever appear, |
3691 | * we'd better make sure that there's no link(2) for them. |
3692 | * d) conversion from fhandle to dentry may come in the wrong moment - when |
3693 | * we are removing the target. Solution: we will have to grab ->i_mutex |
3694 | * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on |
3695 | * ->i_mutex on parents, which works but leads to some truly excessive |
3696 | * locking]. |
3697 | */ |
3698 | static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry, |
3699 | struct inode *new_dir, struct dentry *new_dentry) |
3700 | { |
3701 | int error = 0; |
3702 | struct inode *target = new_dentry->d_inode; |
3703 | unsigned max_links = new_dir->i_sb->s_max_links; |
3704 | |
3705 | /* |
3706 | * If we are going to change the parent - check write permissions, |
3707 | * we'll need to flip '..'. |
3708 | */ |
3709 | if (new_dir != old_dir) { |
3710 | error = inode_permission(old_dentry->d_inode, MAY_WRITE); |
3711 | if (error) |
3712 | return error; |
3713 | } |
3714 | |
3715 | error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry); |
3716 | if (error) |
3717 | return error; |
3718 | |
3719 | dget(new_dentry); |
3720 | if (target) |
3721 | mutex_lock(&target->i_mutex); |
3722 | |
3723 | error = -EBUSY; |
3724 | if (d_mountpoint(old_dentry) || d_mountpoint(new_dentry)) |
3725 | goto out; |
3726 | |
3727 | error = -EMLINK; |
3728 | if (max_links && !target && new_dir != old_dir && |
3729 | new_dir->i_nlink >= max_links) |
3730 | goto out; |
3731 | |
3732 | if (target) |
3733 | shrink_dcache_parent(new_dentry); |
3734 | error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry); |
3735 | if (error) |
3736 | goto out; |
3737 | |
3738 | if (target) { |
3739 | target->i_flags |= S_DEAD; |
3740 | dont_mount(new_dentry); |
3741 | } |
3742 | out: |
3743 | if (target) |
3744 | mutex_unlock(&target->i_mutex); |
3745 | dput(new_dentry); |
3746 | if (!error) |
3747 | if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) |
3748 | d_move(old_dentry,new_dentry); |
3749 | return error; |
3750 | } |
3751 | |
3752 | static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry, |
3753 | struct inode *new_dir, struct dentry *new_dentry) |
3754 | { |
3755 | struct inode *target = new_dentry->d_inode; |
3756 | int error; |
3757 | |
3758 | error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry); |
3759 | if (error) |
3760 | return error; |
3761 | |
3762 | dget(new_dentry); |
3763 | if (target) |
3764 | mutex_lock(&target->i_mutex); |
3765 | |
3766 | error = -EBUSY; |
3767 | if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry)) |
3768 | goto out; |
3769 | |
3770 | error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry); |
3771 | if (error) |
3772 | goto out; |
3773 | |
3774 | if (target) |
3775 | dont_mount(new_dentry); |
3776 | if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) |
3777 | d_move(old_dentry, new_dentry); |
3778 | out: |
3779 | if (target) |
3780 | mutex_unlock(&target->i_mutex); |
3781 | dput(new_dentry); |
3782 | return error; |
3783 | } |
3784 | |
3785 | int vfs_rename(struct inode *old_dir, struct dentry *old_dentry, |
3786 | struct inode *new_dir, struct dentry *new_dentry) |
3787 | { |
3788 | int error; |
3789 | int is_dir = S_ISDIR(old_dentry->d_inode->i_mode); |
3790 | const unsigned char *old_name; |
3791 | |
3792 | if (old_dentry->d_inode == new_dentry->d_inode) |
3793 | return 0; |
3794 | |
3795 | error = may_delete(old_dir, old_dentry, is_dir); |
3796 | if (error) |
3797 | return error; |
3798 | |
3799 | if (!new_dentry->d_inode) |
3800 | error = may_create(new_dir, new_dentry); |
3801 | else |
3802 | error = may_delete(new_dir, new_dentry, is_dir); |
3803 | if (error) |
3804 | return error; |
3805 | |
3806 | if (!old_dir->i_op->rename) |
3807 | return -EPERM; |
3808 | |
3809 | old_name = fsnotify_oldname_init(old_dentry->d_name.name); |
3810 | |
3811 | if (is_dir) |
3812 | error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry); |
3813 | else |
3814 | error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry); |
3815 | if (!error) |
3816 | fsnotify_move(old_dir, new_dir, old_name, is_dir, |
3817 | new_dentry->d_inode, old_dentry); |
3818 | fsnotify_oldname_free(old_name); |
3819 | |
3820 | return error; |
3821 | } |
3822 | |
3823 | SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname, |
3824 | int, newdfd, const char __user *, newname) |
3825 | { |
3826 | struct dentry *old_dir, *new_dir; |
3827 | struct dentry *old_dentry, *new_dentry; |
3828 | struct dentry *trap; |
3829 | struct nameidata oldnd, newnd; |
3830 | struct filename *from; |
3831 | struct filename *to; |
3832 | unsigned int lookup_flags = 0; |
3833 | bool should_retry = false; |
3834 | int error; |
3835 | retry: |
3836 | from = user_path_parent(olddfd, oldname, &oldnd, lookup_flags); |
3837 | if (IS_ERR(from)) { |
3838 | error = PTR_ERR(from); |
3839 | goto exit; |
3840 | } |
3841 | |
3842 | to = user_path_parent(newdfd, newname, &newnd, lookup_flags); |
3843 | if (IS_ERR(to)) { |
3844 | error = PTR_ERR(to); |
3845 | goto exit1; |
3846 | } |
3847 | |
3848 | error = -EXDEV; |
3849 | if (oldnd.path.mnt != newnd.path.mnt) |
3850 | goto exit2; |
3851 | |
3852 | old_dir = oldnd.path.dentry; |
3853 | error = -EBUSY; |
3854 | if (oldnd.last_type != LAST_NORM) |
3855 | goto exit2; |
3856 | |
3857 | new_dir = newnd.path.dentry; |
3858 | if (newnd.last_type != LAST_NORM) |
3859 | goto exit2; |
3860 | |
3861 | error = mnt_want_write(oldnd.path.mnt); |
3862 | if (error) |
3863 | goto exit2; |
3864 | |
3865 | oldnd.flags &= ~LOOKUP_PARENT; |
3866 | newnd.flags &= ~LOOKUP_PARENT; |
3867 | newnd.flags |= LOOKUP_RENAME_TARGET; |
3868 | |
3869 | trap = lock_rename(new_dir, old_dir); |
3870 | |
3871 | old_dentry = lookup_hash(&oldnd); |
3872 | error = PTR_ERR(old_dentry); |
3873 | if (IS_ERR(old_dentry)) |
3874 | goto exit3; |
3875 | /* source must exist */ |
3876 | error = -ENOENT; |
3877 | if (!old_dentry->d_inode) |
3878 | goto exit4; |
3879 | /* unless the source is a directory trailing slashes give -ENOTDIR */ |
3880 | if (!S_ISDIR(old_dentry->d_inode->i_mode)) { |
3881 | error = -ENOTDIR; |
3882 | if (oldnd.last.name[oldnd.last.len]) |
3883 | goto exit4; |
3884 | if (newnd.last.name[newnd.last.len]) |
3885 | goto exit4; |
3886 | } |
3887 | /* source should not be ancestor of target */ |
3888 | error = -EINVAL; |
3889 | if (old_dentry == trap) |
3890 | goto exit4; |
3891 | new_dentry = lookup_hash(&newnd); |
3892 | error = PTR_ERR(new_dentry); |
3893 | if (IS_ERR(new_dentry)) |
3894 | goto exit4; |
3895 | /* target should not be an ancestor of source */ |
3896 | error = -ENOTEMPTY; |
3897 | if (new_dentry == trap) |
3898 | goto exit5; |
3899 | |
3900 | error = security_path_rename(&oldnd.path, old_dentry, |
3901 | &newnd.path, new_dentry); |
3902 | if (error) |
3903 | goto exit5; |
3904 | error = vfs_rename(old_dir->d_inode, old_dentry, |
3905 | new_dir->d_inode, new_dentry); |
3906 | exit5: |
3907 | dput(new_dentry); |
3908 | exit4: |
3909 | dput(old_dentry); |
3910 | exit3: |
3911 | unlock_rename(new_dir, old_dir); |
3912 | mnt_drop_write(oldnd.path.mnt); |
3913 | exit2: |
3914 | if (retry_estale(error, lookup_flags)) |
3915 | should_retry = true; |
3916 | path_put(&newnd.path); |
3917 | putname(to); |
3918 | exit1: |
3919 | path_put(&oldnd.path); |
3920 | putname(from); |
3921 | if (should_retry) { |
3922 | should_retry = false; |
3923 | lookup_flags |= LOOKUP_REVAL; |
3924 | goto retry; |
3925 | } |
3926 | exit: |
3927 | return error; |
3928 | } |
3929 | |
3930 | SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname) |
3931 | { |
3932 | return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname); |
3933 | } |
3934 | |
3935 | int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link) |
3936 | { |
3937 | int len; |
3938 | |
3939 | len = PTR_ERR(link); |
3940 | if (IS_ERR(link)) |
3941 | goto out; |
3942 | |
3943 | len = strlen(link); |
3944 | if (len > (unsigned) buflen) |
3945 | len = buflen; |
3946 | if (copy_to_user(buffer, link, len)) |
3947 | len = -EFAULT; |
3948 | out: |
3949 | return len; |
3950 | } |
3951 | |
3952 | /* |
3953 | * A helper for ->readlink(). This should be used *ONLY* for symlinks that |
3954 | * have ->follow_link() touching nd only in nd_set_link(). Using (or not |
3955 | * using) it for any given inode is up to filesystem. |
3956 | */ |
3957 | int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen) |
3958 | { |
3959 | struct nameidata nd; |
3960 | void *cookie; |
3961 | int res; |
3962 | |
3963 | nd.depth = 0; |
3964 | cookie = dentry->d_inode->i_op->follow_link(dentry, &nd); |
3965 | if (IS_ERR(cookie)) |
3966 | return PTR_ERR(cookie); |
3967 | |
3968 | res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd)); |
3969 | if (dentry->d_inode->i_op->put_link) |
3970 | dentry->d_inode->i_op->put_link(dentry, &nd, cookie); |
3971 | return res; |
3972 | } |
3973 | |
3974 | int vfs_follow_link(struct nameidata *nd, const char *link) |
3975 | { |
3976 | return __vfs_follow_link(nd, link); |
3977 | } |
3978 | |
3979 | /* get the link contents into pagecache */ |
3980 | static char *page_getlink(struct dentry * dentry, struct page **ppage) |
3981 | { |
3982 | char *kaddr; |
3983 | struct page *page; |
3984 | struct address_space *mapping = dentry->d_inode->i_mapping; |
3985 | page = read_mapping_page(mapping, 0, NULL); |
3986 | if (IS_ERR(page)) |
3987 | return (char*)page; |
3988 | *ppage = page; |
3989 | kaddr = kmap(page); |
3990 | nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1); |
3991 | return kaddr; |
3992 | } |
3993 | |
3994 | int page_readlink(struct dentry *dentry, char __user *buffer, int buflen) |
3995 | { |
3996 | struct page *page = NULL; |
3997 | char *s = page_getlink(dentry, &page); |
3998 | int res = vfs_readlink(dentry,buffer,buflen,s); |
3999 | if (page) { |
4000 | kunmap(page); |
4001 | page_cache_release(page); |
4002 | } |
4003 | return res; |
4004 | } |
4005 | |
4006 | void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd) |
4007 | { |
4008 | struct page *page = NULL; |
4009 | nd_set_link(nd, page_getlink(dentry, &page)); |
4010 | return page; |
4011 | } |
4012 | |
4013 | void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie) |
4014 | { |
4015 | struct page *page = cookie; |
4016 | |
4017 | if (page) { |
4018 | kunmap(page); |
4019 | page_cache_release(page); |
4020 | } |
4021 | } |
4022 | |
4023 | /* |
4024 | * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS |
4025 | */ |
4026 | int __page_symlink(struct inode *inode, const char *symname, int len, int nofs) |
4027 | { |
4028 | struct address_space *mapping = inode->i_mapping; |
4029 | struct page *page; |
4030 | void *fsdata; |
4031 | int err; |
4032 | char *kaddr; |
4033 | unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE; |
4034 | if (nofs) |
4035 | flags |= AOP_FLAG_NOFS; |
4036 | |
4037 | retry: |
4038 | err = pagecache_write_begin(NULL, mapping, 0, len-1, |
4039 | flags, &page, &fsdata); |
4040 | if (err) |
4041 | goto fail; |
4042 | |
4043 | kaddr = kmap_atomic(page); |
4044 | memcpy(kaddr, symname, len-1); |
4045 | kunmap_atomic(kaddr); |
4046 | |
4047 | err = pagecache_write_end(NULL, mapping, 0, len-1, len-1, |
4048 | page, fsdata); |
4049 | if (err < 0) |
4050 | goto fail; |
4051 | if (err < len-1) |
4052 | goto retry; |
4053 | |
4054 | mark_inode_dirty(inode); |
4055 | return 0; |
4056 | fail: |
4057 | return err; |
4058 | } |
4059 | |
4060 | int page_symlink(struct inode *inode, const char *symname, int len) |
4061 | { |
4062 | return __page_symlink(inode, symname, len, |
4063 | !(mapping_gfp_mask(inode->i_mapping) & __GFP_FS)); |
4064 | } |
4065 | |
4066 | const struct inode_operations page_symlink_inode_operations = { |
4067 | .readlink = generic_readlink, |
4068 | .follow_link = page_follow_link_light, |
4069 | .put_link = page_put_link, |
4070 | }; |
4071 | |
4072 | EXPORT_SYMBOL(user_path_at); |
4073 | EXPORT_SYMBOL(follow_down_one); |
4074 | EXPORT_SYMBOL(follow_down); |
4075 | EXPORT_SYMBOL(follow_up); |
4076 | EXPORT_SYMBOL(get_write_access); /* nfsd */ |
4077 | EXPORT_SYMBOL(lock_rename); |
4078 | EXPORT_SYMBOL(lookup_one_len); |
4079 | EXPORT_SYMBOL(page_follow_link_light); |
4080 | EXPORT_SYMBOL(page_put_link); |
4081 | EXPORT_SYMBOL(page_readlink); |
4082 | EXPORT_SYMBOL(__page_symlink); |
4083 | EXPORT_SYMBOL(page_symlink); |
4084 | EXPORT_SYMBOL(page_symlink_inode_operations); |
4085 | EXPORT_SYMBOL(kern_path); |
4086 | EXPORT_SYMBOL(vfs_path_lookup); |
4087 | EXPORT_SYMBOL(inode_permission); |
4088 | EXPORT_SYMBOL(unlock_rename); |
4089 | EXPORT_SYMBOL(vfs_create); |
4090 | EXPORT_SYMBOL(vfs_follow_link); |
4091 | EXPORT_SYMBOL(vfs_link); |
4092 | EXPORT_SYMBOL(vfs_mkdir); |
4093 | EXPORT_SYMBOL(vfs_mknod); |
4094 | EXPORT_SYMBOL(generic_permission); |
4095 | EXPORT_SYMBOL(vfs_readlink); |
4096 | EXPORT_SYMBOL(vfs_rename); |
4097 | EXPORT_SYMBOL(vfs_rmdir); |
4098 | EXPORT_SYMBOL(vfs_symlink); |
4099 | EXPORT_SYMBOL(vfs_unlink); |
4100 | EXPORT_SYMBOL(dentry_unhash); |
4101 | EXPORT_SYMBOL(generic_readlink); |
4102 |
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v2.6.34-rc5
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