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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 | static char *getname_flags(const char __user *filename, int flags, int *empty) | |
121 | { | |
122 | char *result = __getname(), *err; | |
123 | int len; | |
124 | ||
125 | if (unlikely(!result)) | |
126 | return ERR_PTR(-ENOMEM); | |
127 | ||
128 | len = strncpy_from_user(result, filename, PATH_MAX); | |
129 | err = ERR_PTR(len); | |
130 | if (unlikely(len < 0)) | |
131 | goto error; | |
132 | ||
133 | /* The empty path is special. */ | |
134 | if (unlikely(!len)) { | |
135 | if (empty) | |
136 | *empty = 1; | |
137 | err = ERR_PTR(-ENOENT); | |
138 | if (!(flags & LOOKUP_EMPTY)) | |
139 | goto error; | |
140 | } | |
141 | ||
142 | err = ERR_PTR(-ENAMETOOLONG); | |
143 | if (likely(len < PATH_MAX)) { | |
144 | audit_getname(result); | |
145 | return result; | |
146 | } | |
147 | ||
148 | error: | |
149 | __putname(result); | |
150 | return err; | |
151 | } | |
152 | ||
153 | char *getname(const char __user * filename) | |
154 | { | |
155 | return getname_flags(filename, 0, NULL); | |
156 | } | |
157 | ||
158 | #ifdef CONFIG_AUDITSYSCALL | |
159 | void putname(const char *name) | |
160 | { | |
161 | if (unlikely(!audit_dummy_context())) | |
162 | audit_putname(name); | |
163 | else | |
164 | __putname(name); | |
165 | } | |
166 | EXPORT_SYMBOL(putname); | |
167 | #endif | |
168 | ||
169 | static int check_acl(struct inode *inode, int mask) | |
170 | { | |
171 | #ifdef CONFIG_FS_POSIX_ACL | |
172 | struct posix_acl *acl; | |
173 | ||
174 | if (mask & MAY_NOT_BLOCK) { | |
175 | acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS); | |
176 | if (!acl) | |
177 | return -EAGAIN; | |
178 | /* no ->get_acl() calls in RCU mode... */ | |
179 | if (acl == ACL_NOT_CACHED) | |
180 | return -ECHILD; | |
181 | return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK); | |
182 | } | |
183 | ||
184 | acl = get_cached_acl(inode, ACL_TYPE_ACCESS); | |
185 | ||
186 | /* | |
187 | * A filesystem can force a ACL callback by just never filling the | |
188 | * ACL cache. But normally you'd fill the cache either at inode | |
189 | * instantiation time, or on the first ->get_acl call. | |
190 | * | |
191 | * If the filesystem doesn't have a get_acl() function at all, we'll | |
192 | * just create the negative cache entry. | |
193 | */ | |
194 | if (acl == ACL_NOT_CACHED) { | |
195 | if (inode->i_op->get_acl) { | |
196 | acl = inode->i_op->get_acl(inode, ACL_TYPE_ACCESS); | |
197 | if (IS_ERR(acl)) | |
198 | return PTR_ERR(acl); | |
199 | } else { | |
200 | set_cached_acl(inode, ACL_TYPE_ACCESS, NULL); | |
201 | return -EAGAIN; | |
202 | } | |
203 | } | |
204 | ||
205 | if (acl) { | |
206 | int error = posix_acl_permission(inode, acl, mask); | |
207 | posix_acl_release(acl); | |
208 | return error; | |
209 | } | |
210 | #endif | |
211 | ||
212 | return -EAGAIN; | |
213 | } | |
214 | ||
215 | /* | |
216 | * This does the basic permission checking | |
217 | */ | |
218 | static int acl_permission_check(struct inode *inode, int mask) | |
219 | { | |
220 | unsigned int mode = inode->i_mode; | |
221 | ||
222 | if (likely(uid_eq(current_fsuid(), inode->i_uid))) | |
223 | mode >>= 6; | |
224 | else { | |
225 | if (IS_POSIXACL(inode) && (mode & S_IRWXG)) { | |
226 | int error = check_acl(inode, mask); | |
227 | if (error != -EAGAIN) | |
228 | return error; | |
229 | } | |
230 | ||
231 | if (in_group_p(inode->i_gid)) | |
232 | mode >>= 3; | |
233 | } | |
234 | ||
235 | /* | |
236 | * If the DACs are ok we don't need any capability check. | |
237 | */ | |
238 | if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0) | |
239 | return 0; | |
240 | return -EACCES; | |
241 | } | |
242 | ||
243 | /** | |
244 | * generic_permission - check for access rights on a Posix-like filesystem | |
245 | * @inode: inode to check access rights for | |
246 | * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...) | |
247 | * | |
248 | * Used to check for read/write/execute permissions on a file. | |
249 | * We use "fsuid" for this, letting us set arbitrary permissions | |
250 | * for filesystem access without changing the "normal" uids which | |
251 | * are used for other things. | |
252 | * | |
253 | * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk | |
254 | * request cannot be satisfied (eg. requires blocking or too much complexity). | |
255 | * It would then be called again in ref-walk mode. | |
256 | */ | |
257 | int generic_permission(struct inode *inode, int mask) | |
258 | { | |
259 | int ret; | |
260 | ||
261 | /* | |
262 | * Do the basic permission checks. | |
263 | */ | |
264 | ret = acl_permission_check(inode, mask); | |
265 | if (ret != -EACCES) | |
266 | return ret; | |
267 | ||
268 | if (S_ISDIR(inode->i_mode)) { | |
269 | /* DACs are overridable for directories */ | |
270 | if (inode_capable(inode, CAP_DAC_OVERRIDE)) | |
271 | return 0; | |
272 | if (!(mask & MAY_WRITE)) | |
273 | if (inode_capable(inode, CAP_DAC_READ_SEARCH)) | |
274 | return 0; | |
275 | return -EACCES; | |
276 | } | |
277 | /* | |
278 | * Read/write DACs are always overridable. | |
279 | * Executable DACs are overridable when there is | |
280 | * at least one exec bit set. | |
281 | */ | |
282 | if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO)) | |
283 | if (inode_capable(inode, CAP_DAC_OVERRIDE)) | |
284 | return 0; | |
285 | ||
286 | /* | |
287 | * Searching includes executable on directories, else just read. | |
288 | */ | |
289 | mask &= MAY_READ | MAY_WRITE | MAY_EXEC; | |
290 | if (mask == MAY_READ) | |
291 | if (inode_capable(inode, CAP_DAC_READ_SEARCH)) | |
292 | return 0; | |
293 | ||
294 | return -EACCES; | |
295 | } | |
296 | ||
297 | /* | |
298 | * We _really_ want to just do "generic_permission()" without | |
299 | * even looking at the inode->i_op values. So we keep a cache | |
300 | * flag in inode->i_opflags, that says "this has not special | |
301 | * permission function, use the fast case". | |
302 | */ | |
303 | static inline int do_inode_permission(struct inode *inode, int mask) | |
304 | { | |
305 | if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) { | |
306 | if (likely(inode->i_op->permission)) | |
307 | return inode->i_op->permission(inode, mask); | |
308 | ||
309 | /* This gets set once for the inode lifetime */ | |
310 | spin_lock(&inode->i_lock); | |
311 | inode->i_opflags |= IOP_FASTPERM; | |
312 | spin_unlock(&inode->i_lock); | |
313 | } | |
314 | return generic_permission(inode, mask); | |
315 | } | |
316 | ||
317 | /** | |
318 | * inode_permission - check for access rights to a given inode | |
319 | * @inode: inode to check permission on | |
320 | * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...) | |
321 | * | |
322 | * Used to check for read/write/execute permissions on an inode. | |
323 | * We use "fsuid" for this, letting us set arbitrary permissions | |
324 | * for filesystem access without changing the "normal" uids which | |
325 | * are used for other things. | |
326 | * | |
327 | * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask. | |
328 | */ | |
329 | int inode_permission(struct inode *inode, int mask) | |
330 | { | |
331 | int retval; | |
332 | ||
333 | if (unlikely(mask & MAY_WRITE)) { | |
334 | umode_t mode = inode->i_mode; | |
335 | ||
336 | /* | |
337 | * Nobody gets write access to a read-only fs. | |
338 | */ | |
339 | if (IS_RDONLY(inode) && | |
340 | (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) | |
341 | return -EROFS; | |
342 | ||
343 | /* | |
344 | * Nobody gets write access to an immutable file. | |
345 | */ | |
346 | if (IS_IMMUTABLE(inode)) | |
347 | return -EACCES; | |
348 | } | |
349 | ||
350 | retval = do_inode_permission(inode, mask); | |
351 | if (retval) | |
352 | return retval; | |
353 | ||
354 | retval = devcgroup_inode_permission(inode, mask); | |
355 | if (retval) | |
356 | return retval; | |
357 | ||
358 | return security_inode_permission(inode, mask); | |
359 | } | |
360 | ||
361 | /** | |
362 | * path_get - get a reference to a path | |
363 | * @path: path to get the reference to | |
364 | * | |
365 | * Given a path increment the reference count to the dentry and the vfsmount. | |
366 | */ | |
367 | void path_get(struct path *path) | |
368 | { | |
369 | mntget(path->mnt); | |
370 | dget(path->dentry); | |
371 | } | |
372 | EXPORT_SYMBOL(path_get); | |
373 | ||
374 | /** | |
375 | * path_put - put a reference to a path | |
376 | * @path: path to put the reference to | |
377 | * | |
378 | * Given a path decrement the reference count to the dentry and the vfsmount. | |
379 | */ | |
380 | void path_put(struct path *path) | |
381 | { | |
382 | dput(path->dentry); | |
383 | mntput(path->mnt); | |
384 | } | |
385 | EXPORT_SYMBOL(path_put); | |
386 | ||
387 | /* | |
388 | * Path walking has 2 modes, rcu-walk and ref-walk (see | |
389 | * Documentation/filesystems/path-lookup.txt). In situations when we can't | |
390 | * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab | |
391 | * normal reference counts on dentries and vfsmounts to transition to rcu-walk | |
392 | * mode. Refcounts are grabbed at the last known good point before rcu-walk | |
393 | * got stuck, so ref-walk may continue from there. If this is not successful | |
394 | * (eg. a seqcount has changed), then failure is returned and it's up to caller | |
395 | * to restart the path walk from the beginning in ref-walk mode. | |
396 | */ | |
397 | ||
398 | /** | |
399 | * unlazy_walk - try to switch to ref-walk mode. | |
400 | * @nd: nameidata pathwalk data | |
401 | * @dentry: child of nd->path.dentry or NULL | |
402 | * Returns: 0 on success, -ECHILD on failure | |
403 | * | |
404 | * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry | |
405 | * for ref-walk mode. @dentry must be a path found by a do_lookup call on | |
406 | * @nd or NULL. Must be called from rcu-walk context. | |
407 | */ | |
408 | static int unlazy_walk(struct nameidata *nd, struct dentry *dentry) | |
409 | { | |
410 | struct fs_struct *fs = current->fs; | |
411 | struct dentry *parent = nd->path.dentry; | |
412 | int want_root = 0; | |
413 | ||
414 | BUG_ON(!(nd->flags & LOOKUP_RCU)); | |
415 | if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) { | |
416 | want_root = 1; | |
417 | spin_lock(&fs->lock); | |
418 | if (nd->root.mnt != fs->root.mnt || | |
419 | nd->root.dentry != fs->root.dentry) | |
420 | goto err_root; | |
421 | } | |
422 | spin_lock(&parent->d_lock); | |
423 | if (!dentry) { | |
424 | if (!__d_rcu_to_refcount(parent, nd->seq)) | |
425 | goto err_parent; | |
426 | BUG_ON(nd->inode != parent->d_inode); | |
427 | } else { | |
428 | if (dentry->d_parent != parent) | |
429 | goto err_parent; | |
430 | spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); | |
431 | if (!__d_rcu_to_refcount(dentry, nd->seq)) | |
432 | goto err_child; | |
433 | /* | |
434 | * If the sequence check on the child dentry passed, then | |
435 | * the child has not been removed from its parent. This | |
436 | * means the parent dentry must be valid and able to take | |
437 | * a reference at this point. | |
438 | */ | |
439 | BUG_ON(!IS_ROOT(dentry) && dentry->d_parent != parent); | |
440 | BUG_ON(!parent->d_count); | |
441 | parent->d_count++; | |
442 | spin_unlock(&dentry->d_lock); | |
443 | } | |
444 | spin_unlock(&parent->d_lock); | |
445 | if (want_root) { | |
446 | path_get(&nd->root); | |
447 | spin_unlock(&fs->lock); | |
448 | } | |
449 | mntget(nd->path.mnt); | |
450 | ||
451 | rcu_read_unlock(); | |
452 | br_read_unlock(&vfsmount_lock); | |
453 | nd->flags &= ~LOOKUP_RCU; | |
454 | return 0; | |
455 | ||
456 | err_child: | |
457 | spin_unlock(&dentry->d_lock); | |
458 | err_parent: | |
459 | spin_unlock(&parent->d_lock); | |
460 | err_root: | |
461 | if (want_root) | |
462 | spin_unlock(&fs->lock); | |
463 | return -ECHILD; | |
464 | } | |
465 | ||
466 | static inline int d_revalidate(struct dentry *dentry, struct nameidata *nd) | |
467 | { | |
468 | return dentry->d_op->d_revalidate(dentry, nd); | |
469 | } | |
470 | ||
471 | /** | |
472 | * complete_walk - successful completion of path walk | |
473 | * @nd: pointer nameidata | |
474 | * | |
475 | * If we had been in RCU mode, drop out of it and legitimize nd->path. | |
476 | * Revalidate the final result, unless we'd already done that during | |
477 | * the path walk or the filesystem doesn't ask for it. Return 0 on | |
478 | * success, -error on failure. In case of failure caller does not | |
479 | * need to drop nd->path. | |
480 | */ | |
481 | static int complete_walk(struct nameidata *nd) | |
482 | { | |
483 | struct dentry *dentry = nd->path.dentry; | |
484 | int status; | |
485 | ||
486 | if (nd->flags & LOOKUP_RCU) { | |
487 | nd->flags &= ~LOOKUP_RCU; | |
488 | if (!(nd->flags & LOOKUP_ROOT)) | |
489 | nd->root.mnt = NULL; | |
490 | spin_lock(&dentry->d_lock); | |
491 | if (unlikely(!__d_rcu_to_refcount(dentry, nd->seq))) { | |
492 | spin_unlock(&dentry->d_lock); | |
493 | rcu_read_unlock(); | |
494 | br_read_unlock(&vfsmount_lock); | |
495 | return -ECHILD; | |
496 | } | |
497 | BUG_ON(nd->inode != dentry->d_inode); | |
498 | spin_unlock(&dentry->d_lock); | |
499 | mntget(nd->path.mnt); | |
500 | rcu_read_unlock(); | |
501 | br_read_unlock(&vfsmount_lock); | |
502 | } | |
503 | ||
504 | if (likely(!(nd->flags & LOOKUP_JUMPED))) | |
505 | return 0; | |
506 | ||
507 | if (likely(!(dentry->d_flags & DCACHE_OP_REVALIDATE))) | |
508 | return 0; | |
509 | ||
510 | if (likely(!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT))) | |
511 | return 0; | |
512 | ||
513 | /* Note: we do not d_invalidate() */ | |
514 | status = d_revalidate(dentry, nd); | |
515 | if (status > 0) | |
516 | return 0; | |
517 | ||
518 | if (!status) | |
519 | status = -ESTALE; | |
520 | ||
521 | path_put(&nd->path); | |
522 | return status; | |
523 | } | |
524 | ||
525 | static __always_inline void set_root(struct nameidata *nd) | |
526 | { | |
527 | if (!nd->root.mnt) | |
528 | get_fs_root(current->fs, &nd->root); | |
529 | } | |
530 | ||
531 | static int link_path_walk(const char *, struct nameidata *); | |
532 | ||
533 | static __always_inline void set_root_rcu(struct nameidata *nd) | |
534 | { | |
535 | if (!nd->root.mnt) { | |
536 | struct fs_struct *fs = current->fs; | |
537 | unsigned seq; | |
538 | ||
539 | do { | |
540 | seq = read_seqcount_begin(&fs->seq); | |
541 | nd->root = fs->root; | |
542 | nd->seq = __read_seqcount_begin(&nd->root.dentry->d_seq); | |
543 | } while (read_seqcount_retry(&fs->seq, seq)); | |
544 | } | |
545 | } | |
546 | ||
547 | static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link) | |
548 | { | |
549 | int ret; | |
550 | ||
551 | if (IS_ERR(link)) | |
552 | goto fail; | |
553 | ||
554 | if (*link == '/') { | |
555 | set_root(nd); | |
556 | path_put(&nd->path); | |
557 | nd->path = nd->root; | |
558 | path_get(&nd->root); | |
559 | nd->flags |= LOOKUP_JUMPED; | |
560 | } | |
561 | nd->inode = nd->path.dentry->d_inode; | |
562 | ||
563 | ret = link_path_walk(link, nd); | |
564 | return ret; | |
565 | fail: | |
566 | path_put(&nd->path); | |
567 | return PTR_ERR(link); | |
568 | } | |
569 | ||
570 | static void path_put_conditional(struct path *path, struct nameidata *nd) | |
571 | { | |
572 | dput(path->dentry); | |
573 | if (path->mnt != nd->path.mnt) | |
574 | mntput(path->mnt); | |
575 | } | |
576 | ||
577 | static inline void path_to_nameidata(const struct path *path, | |
578 | struct nameidata *nd) | |
579 | { | |
580 | if (!(nd->flags & LOOKUP_RCU)) { | |
581 | dput(nd->path.dentry); | |
582 | if (nd->path.mnt != path->mnt) | |
583 | mntput(nd->path.mnt); | |
584 | } | |
585 | nd->path.mnt = path->mnt; | |
586 | nd->path.dentry = path->dentry; | |
587 | } | |
588 | ||
589 | static inline void put_link(struct nameidata *nd, struct path *link, void *cookie) | |
590 | { | |
591 | struct inode *inode = link->dentry->d_inode; | |
592 | if (inode->i_op->put_link) | |
593 | inode->i_op->put_link(link->dentry, nd, cookie); | |
594 | path_put(link); | |
595 | } | |
596 | ||
597 | static __always_inline int | |
598 | follow_link(struct path *link, struct nameidata *nd, void **p) | |
599 | { | |
600 | struct dentry *dentry = link->dentry; | |
601 | int error; | |
602 | char *s; | |
603 | ||
604 | BUG_ON(nd->flags & LOOKUP_RCU); | |
605 | ||
606 | if (link->mnt == nd->path.mnt) | |
607 | mntget(link->mnt); | |
608 | ||
609 | error = -ELOOP; | |
610 | if (unlikely(current->total_link_count >= 40)) | |
611 | goto out_put_nd_path; | |
612 | ||
613 | cond_resched(); | |
614 | current->total_link_count++; | |
615 | ||
616 | touch_atime(link); | |
617 | nd_set_link(nd, NULL); | |
618 | ||
619 | error = security_inode_follow_link(link->dentry, nd); | |
620 | if (error) | |
621 | goto out_put_nd_path; | |
622 | ||
623 | nd->last_type = LAST_BIND; | |
624 | *p = dentry->d_inode->i_op->follow_link(dentry, nd); | |
625 | error = PTR_ERR(*p); | |
626 | if (IS_ERR(*p)) | |
627 | goto out_put_link; | |
628 | ||
629 | error = 0; | |
630 | s = nd_get_link(nd); | |
631 | if (s) { | |
632 | error = __vfs_follow_link(nd, s); | |
633 | } else if (nd->last_type == LAST_BIND) { | |
634 | nd->flags |= LOOKUP_JUMPED; | |
635 | nd->inode = nd->path.dentry->d_inode; | |
636 | if (nd->inode->i_op->follow_link) { | |
637 | /* stepped on a _really_ weird one */ | |
638 | path_put(&nd->path); | |
639 | error = -ELOOP; | |
640 | } | |
641 | } | |
642 | if (unlikely(error)) | |
643 | put_link(nd, link, *p); | |
644 | ||
645 | return error; | |
646 | ||
647 | out_put_nd_path: | |
648 | path_put(&nd->path); | |
649 | out_put_link: | |
650 | path_put(link); | |
651 | return error; | |
652 | } | |
653 | ||
654 | static int follow_up_rcu(struct path *path) | |
655 | { | |
656 | struct mount *mnt = real_mount(path->mnt); | |
657 | struct mount *parent; | |
658 | struct dentry *mountpoint; | |
659 | ||
660 | parent = mnt->mnt_parent; | |
661 | if (&parent->mnt == path->mnt) | |
662 | return 0; | |
663 | mountpoint = mnt->mnt_mountpoint; | |
664 | path->dentry = mountpoint; | |
665 | path->mnt = &parent->mnt; | |
666 | return 1; | |
667 | } | |
668 | ||
669 | int follow_up(struct path *path) | |
670 | { | |
671 | struct mount *mnt = real_mount(path->mnt); | |
672 | struct mount *parent; | |
673 | struct dentry *mountpoint; | |
674 | ||
675 | br_read_lock(&vfsmount_lock); | |
676 | parent = mnt->mnt_parent; | |
677 | if (&parent->mnt == path->mnt) { | |
678 | br_read_unlock(&vfsmount_lock); | |
679 | return 0; | |
680 | } | |
681 | mntget(&parent->mnt); | |
682 | mountpoint = dget(mnt->mnt_mountpoint); | |
683 | br_read_unlock(&vfsmount_lock); | |
684 | dput(path->dentry); | |
685 | path->dentry = mountpoint; | |
686 | mntput(path->mnt); | |
687 | path->mnt = &parent->mnt; | |
688 | return 1; | |
689 | } | |
690 | ||
691 | /* | |
692 | * Perform an automount | |
693 | * - return -EISDIR to tell follow_managed() to stop and return the path we | |
694 | * were called with. | |
695 | */ | |
696 | static int follow_automount(struct path *path, unsigned flags, | |
697 | bool *need_mntput) | |
698 | { | |
699 | struct vfsmount *mnt; | |
700 | int err; | |
701 | ||
702 | if (!path->dentry->d_op || !path->dentry->d_op->d_automount) | |
703 | return -EREMOTE; | |
704 | ||
705 | /* We don't want to mount if someone's just doing a stat - | |
706 | * unless they're stat'ing a directory and appended a '/' to | |
707 | * the name. | |
708 | * | |
709 | * We do, however, want to mount if someone wants to open or | |
710 | * create a file of any type under the mountpoint, wants to | |
711 | * traverse through the mountpoint or wants to open the | |
712 | * mounted directory. Also, autofs may mark negative dentries | |
713 | * as being automount points. These will need the attentions | |
714 | * of the daemon to instantiate them before they can be used. | |
715 | */ | |
716 | if (!(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY | | |
717 | LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) && | |
718 | path->dentry->d_inode) | |
719 | return -EISDIR; | |
720 | ||
721 | current->total_link_count++; | |
722 | if (current->total_link_count >= 40) | |
723 | return -ELOOP; | |
724 | ||
725 | mnt = path->dentry->d_op->d_automount(path); | |
726 | if (IS_ERR(mnt)) { | |
727 | /* | |
728 | * The filesystem is allowed to return -EISDIR here to indicate | |
729 | * it doesn't want to automount. For instance, autofs would do | |
730 | * this so that its userspace daemon can mount on this dentry. | |
731 | * | |
732 | * However, we can only permit this if it's a terminal point in | |
733 | * the path being looked up; if it wasn't then the remainder of | |
734 | * the path is inaccessible and we should say so. | |
735 | */ | |
736 | if (PTR_ERR(mnt) == -EISDIR && (flags & LOOKUP_PARENT)) | |
737 | return -EREMOTE; | |
738 | return PTR_ERR(mnt); | |
739 | } | |
740 | ||
741 | if (!mnt) /* mount collision */ | |
742 | return 0; | |
743 | ||
744 | if (!*need_mntput) { | |
745 | /* lock_mount() may release path->mnt on error */ | |
746 | mntget(path->mnt); | |
747 | *need_mntput = true; | |
748 | } | |
749 | err = finish_automount(mnt, path); | |
750 | ||
751 | switch (err) { | |
752 | case -EBUSY: | |
753 | /* Someone else made a mount here whilst we were busy */ | |
754 | return 0; | |
755 | case 0: | |
756 | path_put(path); | |
757 | path->mnt = mnt; | |
758 | path->dentry = dget(mnt->mnt_root); | |
759 | return 0; | |
760 | default: | |
761 | return err; | |
762 | } | |
763 | ||
764 | } | |
765 | ||
766 | /* | |
767 | * Handle a dentry that is managed in some way. | |
768 | * - Flagged for transit management (autofs) | |
769 | * - Flagged as mountpoint | |
770 | * - Flagged as automount point | |
771 | * | |
772 | * This may only be called in refwalk mode. | |
773 | * | |
774 | * Serialization is taken care of in namespace.c | |
775 | */ | |
776 | static int follow_managed(struct path *path, unsigned flags) | |
777 | { | |
778 | struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */ | |
779 | unsigned managed; | |
780 | bool need_mntput = false; | |
781 | int ret = 0; | |
782 | ||
783 | /* Given that we're not holding a lock here, we retain the value in a | |
784 | * local variable for each dentry as we look at it so that we don't see | |
785 | * the components of that value change under us */ | |
786 | while (managed = ACCESS_ONCE(path->dentry->d_flags), | |
787 | managed &= DCACHE_MANAGED_DENTRY, | |
788 | unlikely(managed != 0)) { | |
789 | /* Allow the filesystem to manage the transit without i_mutex | |
790 | * being held. */ | |
791 | if (managed & DCACHE_MANAGE_TRANSIT) { | |
792 | BUG_ON(!path->dentry->d_op); | |
793 | BUG_ON(!path->dentry->d_op->d_manage); | |
794 | ret = path->dentry->d_op->d_manage(path->dentry, false); | |
795 | if (ret < 0) | |
796 | break; | |
797 | } | |
798 | ||
799 | /* Transit to a mounted filesystem. */ | |
800 | if (managed & DCACHE_MOUNTED) { | |
801 | struct vfsmount *mounted = lookup_mnt(path); | |
802 | if (mounted) { | |
803 | dput(path->dentry); | |
804 | if (need_mntput) | |
805 | mntput(path->mnt); | |
806 | path->mnt = mounted; | |
807 | path->dentry = dget(mounted->mnt_root); | |
808 | need_mntput = true; | |
809 | continue; | |
810 | } | |
811 | ||
812 | /* Something is mounted on this dentry in another | |
813 | * namespace and/or whatever was mounted there in this | |
814 | * namespace got unmounted before we managed to get the | |
815 | * vfsmount_lock */ | |
816 | } | |
817 | ||
818 | /* Handle an automount point */ | |
819 | if (managed & DCACHE_NEED_AUTOMOUNT) { | |
820 | ret = follow_automount(path, flags, &need_mntput); | |
821 | if (ret < 0) | |
822 | break; | |
823 | continue; | |
824 | } | |
825 | ||
826 | /* We didn't change the current path point */ | |
827 | break; | |
828 | } | |
829 | ||
830 | if (need_mntput && path->mnt == mnt) | |
831 | mntput(path->mnt); | |
832 | if (ret == -EISDIR) | |
833 | ret = 0; | |
834 | return ret < 0 ? ret : need_mntput; | |
835 | } | |
836 | ||
837 | int follow_down_one(struct path *path) | |
838 | { | |
839 | struct vfsmount *mounted; | |
840 | ||
841 | mounted = lookup_mnt(path); | |
842 | if (mounted) { | |
843 | dput(path->dentry); | |
844 | mntput(path->mnt); | |
845 | path->mnt = mounted; | |
846 | path->dentry = dget(mounted->mnt_root); | |
847 | return 1; | |
848 | } | |
849 | return 0; | |
850 | } | |
851 | ||
852 | static inline bool managed_dentry_might_block(struct dentry *dentry) | |
853 | { | |
854 | return (dentry->d_flags & DCACHE_MANAGE_TRANSIT && | |
855 | dentry->d_op->d_manage(dentry, true) < 0); | |
856 | } | |
857 | ||
858 | /* | |
859 | * Try to skip to top of mountpoint pile in rcuwalk mode. Fail if | |
860 | * we meet a managed dentry that would need blocking. | |
861 | */ | |
862 | static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, | |
863 | struct inode **inode) | |
864 | { | |
865 | for (;;) { | |
866 | struct mount *mounted; | |
867 | /* | |
868 | * Don't forget we might have a non-mountpoint managed dentry | |
869 | * that wants to block transit. | |
870 | */ | |
871 | if (unlikely(managed_dentry_might_block(path->dentry))) | |
872 | return false; | |
873 | ||
874 | if (!d_mountpoint(path->dentry)) | |
875 | break; | |
876 | ||
877 | mounted = __lookup_mnt(path->mnt, path->dentry, 1); | |
878 | if (!mounted) | |
879 | break; | |
880 | path->mnt = &mounted->mnt; | |
881 | path->dentry = mounted->mnt.mnt_root; | |
882 | nd->flags |= LOOKUP_JUMPED; | |
883 | nd->seq = read_seqcount_begin(&path->dentry->d_seq); | |
884 | /* | |
885 | * Update the inode too. We don't need to re-check the | |
886 | * dentry sequence number here after this d_inode read, | |
887 | * because a mount-point is always pinned. | |
888 | */ | |
889 | *inode = path->dentry->d_inode; | |
890 | } | |
891 | return true; | |
892 | } | |
893 | ||
894 | static void follow_mount_rcu(struct nameidata *nd) | |
895 | { | |
896 | while (d_mountpoint(nd->path.dentry)) { | |
897 | struct mount *mounted; | |
898 | mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry, 1); | |
899 | if (!mounted) | |
900 | break; | |
901 | nd->path.mnt = &mounted->mnt; | |
902 | nd->path.dentry = mounted->mnt.mnt_root; | |
903 | nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); | |
904 | } | |
905 | } | |
906 | ||
907 | static int follow_dotdot_rcu(struct nameidata *nd) | |
908 | { | |
909 | set_root_rcu(nd); | |
910 | ||
911 | while (1) { | |
912 | if (nd->path.dentry == nd->root.dentry && | |
913 | nd->path.mnt == nd->root.mnt) { | |
914 | break; | |
915 | } | |
916 | if (nd->path.dentry != nd->path.mnt->mnt_root) { | |
917 | struct dentry *old = nd->path.dentry; | |
918 | struct dentry *parent = old->d_parent; | |
919 | unsigned seq; | |
920 | ||
921 | seq = read_seqcount_begin(&parent->d_seq); | |
922 | if (read_seqcount_retry(&old->d_seq, nd->seq)) | |
923 | goto failed; | |
924 | nd->path.dentry = parent; | |
925 | nd->seq = seq; | |
926 | break; | |
927 | } | |
928 | if (!follow_up_rcu(&nd->path)) | |
929 | break; | |
930 | nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq); | |
931 | } | |
932 | follow_mount_rcu(nd); | |
933 | nd->inode = nd->path.dentry->d_inode; | |
934 | return 0; | |
935 | ||
936 | failed: | |
937 | nd->flags &= ~LOOKUP_RCU; | |
938 | if (!(nd->flags & LOOKUP_ROOT)) | |
939 | nd->root.mnt = NULL; | |
940 | rcu_read_unlock(); | |
941 | br_read_unlock(&vfsmount_lock); | |
942 | return -ECHILD; | |
943 | } | |
944 | ||
945 | /* | |
946 | * Follow down to the covering mount currently visible to userspace. At each | |
947 | * point, the filesystem owning that dentry may be queried as to whether the | |
948 | * caller is permitted to proceed or not. | |
949 | */ | |
950 | int follow_down(struct path *path) | |
951 | { | |
952 | unsigned managed; | |
953 | int ret; | |
954 | ||
955 | while (managed = ACCESS_ONCE(path->dentry->d_flags), | |
956 | unlikely(managed & DCACHE_MANAGED_DENTRY)) { | |
957 | /* Allow the filesystem to manage the transit without i_mutex | |
958 | * being held. | |
959 | * | |
960 | * We indicate to the filesystem if someone is trying to mount | |
961 | * something here. This gives autofs the chance to deny anyone | |
962 | * other than its daemon the right to mount on its | |
963 | * superstructure. | |
964 | * | |
965 | * The filesystem may sleep at this point. | |
966 | */ | |
967 | if (managed & DCACHE_MANAGE_TRANSIT) { | |
968 | BUG_ON(!path->dentry->d_op); | |
969 | BUG_ON(!path->dentry->d_op->d_manage); | |
970 | ret = path->dentry->d_op->d_manage( | |
971 | path->dentry, false); | |
972 | if (ret < 0) | |
973 | return ret == -EISDIR ? 0 : ret; | |
974 | } | |
975 | ||
976 | /* Transit to a mounted filesystem. */ | |
977 | if (managed & DCACHE_MOUNTED) { | |
978 | struct vfsmount *mounted = lookup_mnt(path); | |
979 | if (!mounted) | |
980 | break; | |
981 | dput(path->dentry); | |
982 | mntput(path->mnt); | |
983 | path->mnt = mounted; | |
984 | path->dentry = dget(mounted->mnt_root); | |
985 | continue; | |
986 | } | |
987 | ||
988 | /* Don't handle automount points here */ | |
989 | break; | |
990 | } | |
991 | return 0; | |
992 | } | |
993 | ||
994 | /* | |
995 | * Skip to top of mountpoint pile in refwalk mode for follow_dotdot() | |
996 | */ | |
997 | static void follow_mount(struct path *path) | |
998 | { | |
999 | while (d_mountpoint(path->dentry)) { | |
1000 | struct vfsmount *mounted = lookup_mnt(path); | |
1001 | if (!mounted) | |
1002 | break; | |
1003 | dput(path->dentry); | |
1004 | mntput(path->mnt); | |
1005 | path->mnt = mounted; | |
1006 | path->dentry = dget(mounted->mnt_root); | |
1007 | } | |
1008 | } | |
1009 | ||
1010 | static void follow_dotdot(struct nameidata *nd) | |
1011 | { | |
1012 | set_root(nd); | |
1013 | ||
1014 | while(1) { | |
1015 | struct dentry *old = nd->path.dentry; | |
1016 | ||
1017 | if (nd->path.dentry == nd->root.dentry && | |
1018 | nd->path.mnt == nd->root.mnt) { | |
1019 | break; | |
1020 | } | |
1021 | if (nd->path.dentry != nd->path.mnt->mnt_root) { | |
1022 | /* rare case of legitimate dget_parent()... */ | |
1023 | nd->path.dentry = dget_parent(nd->path.dentry); | |
1024 | dput(old); | |
1025 | break; | |
1026 | } | |
1027 | if (!follow_up(&nd->path)) | |
1028 | break; | |
1029 | } | |
1030 | follow_mount(&nd->path); | |
1031 | nd->inode = nd->path.dentry->d_inode; | |
1032 | } | |
1033 | ||
1034 | /* | |
1035 | * This looks up the name in dcache, possibly revalidates the old dentry and | |
1036 | * allocates a new one if not found or not valid. In the need_lookup argument | |
1037 | * returns whether i_op->lookup is necessary. | |
1038 | * | |
1039 | * dir->d_inode->i_mutex must be held | |
1040 | */ | |
1041 | static struct dentry *lookup_dcache(struct qstr *name, struct dentry *dir, | |
1042 | struct nameidata *nd, bool *need_lookup) | |
1043 | { | |
1044 | struct dentry *dentry; | |
1045 | int error; | |
1046 | ||
1047 | *need_lookup = false; | |
1048 | dentry = d_lookup(dir, name); | |
1049 | if (dentry) { | |
1050 | if (d_need_lookup(dentry)) { | |
1051 | *need_lookup = true; | |
1052 | } else if (dentry->d_flags & DCACHE_OP_REVALIDATE) { | |
1053 | error = d_revalidate(dentry, nd); | |
1054 | if (unlikely(error <= 0)) { | |
1055 | if (error < 0) { | |
1056 | dput(dentry); | |
1057 | return ERR_PTR(error); | |
1058 | } else if (!d_invalidate(dentry)) { | |
1059 | dput(dentry); | |
1060 | dentry = NULL; | |
1061 | } | |
1062 | } | |
1063 | } | |
1064 | } | |
1065 | ||
1066 | if (!dentry) { | |
1067 | dentry = d_alloc(dir, name); | |
1068 | if (unlikely(!dentry)) | |
1069 | return ERR_PTR(-ENOMEM); | |
1070 | ||
1071 | *need_lookup = true; | |
1072 | } | |
1073 | return dentry; | |
1074 | } | |
1075 | ||
1076 | /* | |
1077 | * Call i_op->lookup on the dentry. The dentry must be negative but may be | |
1078 | * hashed if it was pouplated with DCACHE_NEED_LOOKUP. | |
1079 | * | |
1080 | * dir->d_inode->i_mutex must be held | |
1081 | */ | |
1082 | static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry, | |
1083 | struct nameidata *nd) | |
1084 | { | |
1085 | struct dentry *old; | |
1086 | ||
1087 | /* Don't create child dentry for a dead directory. */ | |
1088 | if (unlikely(IS_DEADDIR(dir))) { | |
1089 | dput(dentry); | |
1090 | return ERR_PTR(-ENOENT); | |
1091 | } | |
1092 | ||
1093 | old = dir->i_op->lookup(dir, dentry, nd); | |
1094 | if (unlikely(old)) { | |
1095 | dput(dentry); | |
1096 | dentry = old; | |
1097 | } | |
1098 | return dentry; | |
1099 | } | |
1100 | ||
1101 | static struct dentry *__lookup_hash(struct qstr *name, | |
1102 | struct dentry *base, struct nameidata *nd) | |
1103 | { | |
1104 | bool need_lookup; | |
1105 | struct dentry *dentry; | |
1106 | ||
1107 | dentry = lookup_dcache(name, base, nd, &need_lookup); | |
1108 | if (!need_lookup) | |
1109 | return dentry; | |
1110 | ||
1111 | return lookup_real(base->d_inode, dentry, nd); | |
1112 | } | |
1113 | ||
1114 | /* | |
1115 | * It's more convoluted than I'd like it to be, but... it's still fairly | |
1116 | * small and for now I'd prefer to have fast path as straight as possible. | |
1117 | * It _is_ time-critical. | |
1118 | */ | |
1119 | static int lookup_fast(struct nameidata *nd, struct qstr *name, | |
1120 | struct path *path, struct inode **inode) | |
1121 | { | |
1122 | struct vfsmount *mnt = nd->path.mnt; | |
1123 | struct dentry *dentry, *parent = nd->path.dentry; | |
1124 | int need_reval = 1; | |
1125 | int status = 1; | |
1126 | int err; | |
1127 | ||
1128 | /* | |
1129 | * Rename seqlock is not required here because in the off chance | |
1130 | * of a false negative due to a concurrent rename, we're going to | |
1131 | * do the non-racy lookup, below. | |
1132 | */ | |
1133 | if (nd->flags & LOOKUP_RCU) { | |
1134 | unsigned seq; | |
1135 | dentry = __d_lookup_rcu(parent, name, &seq, nd->inode); | |
1136 | if (!dentry) | |
1137 | goto unlazy; | |
1138 | ||
1139 | /* | |
1140 | * This sequence count validates that the inode matches | |
1141 | * the dentry name information from lookup. | |
1142 | */ | |
1143 | *inode = dentry->d_inode; | |
1144 | if (read_seqcount_retry(&dentry->d_seq, seq)) | |
1145 | return -ECHILD; | |
1146 | ||
1147 | /* | |
1148 | * This sequence count validates that the parent had no | |
1149 | * changes while we did the lookup of the dentry above. | |
1150 | * | |
1151 | * The memory barrier in read_seqcount_begin of child is | |
1152 | * enough, we can use __read_seqcount_retry here. | |
1153 | */ | |
1154 | if (__read_seqcount_retry(&parent->d_seq, nd->seq)) | |
1155 | return -ECHILD; | |
1156 | nd->seq = seq; | |
1157 | ||
1158 | if (unlikely(d_need_lookup(dentry))) | |
1159 | goto unlazy; | |
1160 | if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) { | |
1161 | status = d_revalidate(dentry, nd); | |
1162 | if (unlikely(status <= 0)) { | |
1163 | if (status != -ECHILD) | |
1164 | need_reval = 0; | |
1165 | goto unlazy; | |
1166 | } | |
1167 | } | |
1168 | path->mnt = mnt; | |
1169 | path->dentry = dentry; | |
1170 | if (unlikely(!__follow_mount_rcu(nd, path, inode))) | |
1171 | goto unlazy; | |
1172 | if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT)) | |
1173 | goto unlazy; | |
1174 | return 0; | |
1175 | unlazy: | |
1176 | if (unlazy_walk(nd, dentry)) | |
1177 | return -ECHILD; | |
1178 | } else { | |
1179 | dentry = __d_lookup(parent, name); | |
1180 | } | |
1181 | ||
1182 | if (unlikely(!dentry)) | |
1183 | goto need_lookup; | |
1184 | ||
1185 | if (unlikely(d_need_lookup(dentry))) { | |
1186 | dput(dentry); | |
1187 | goto need_lookup; | |
1188 | } | |
1189 | ||
1190 | if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE) && need_reval) | |
1191 | status = d_revalidate(dentry, nd); | |
1192 | if (unlikely(status <= 0)) { | |
1193 | if (status < 0) { | |
1194 | dput(dentry); | |
1195 | return status; | |
1196 | } | |
1197 | if (!d_invalidate(dentry)) { | |
1198 | dput(dentry); | |
1199 | goto need_lookup; | |
1200 | } | |
1201 | } | |
1202 | ||
1203 | path->mnt = mnt; | |
1204 | path->dentry = dentry; | |
1205 | err = follow_managed(path, nd->flags); | |
1206 | if (unlikely(err < 0)) { | |
1207 | path_put_conditional(path, nd); | |
1208 | return err; | |
1209 | } | |
1210 | if (err) | |
1211 | nd->flags |= LOOKUP_JUMPED; | |
1212 | *inode = path->dentry->d_inode; | |
1213 | return 0; | |
1214 | ||
1215 | need_lookup: | |
1216 | return 1; | |
1217 | } | |
1218 | ||
1219 | /* Fast lookup failed, do it the slow way */ | |
1220 | static int lookup_slow(struct nameidata *nd, struct qstr *name, | |
1221 | struct path *path) | |
1222 | { | |
1223 | struct dentry *dentry, *parent; | |
1224 | int err; | |
1225 | ||
1226 | parent = nd->path.dentry; | |
1227 | BUG_ON(nd->inode != parent->d_inode); | |
1228 | ||
1229 | mutex_lock(&parent->d_inode->i_mutex); | |
1230 | dentry = __lookup_hash(name, parent, nd); | |
1231 | mutex_unlock(&parent->d_inode->i_mutex); | |
1232 | if (IS_ERR(dentry)) | |
1233 | return PTR_ERR(dentry); | |
1234 | path->mnt = nd->path.mnt; | |
1235 | path->dentry = dentry; | |
1236 | err = follow_managed(path, nd->flags); | |
1237 | if (unlikely(err < 0)) { | |
1238 | path_put_conditional(path, nd); | |
1239 | return err; | |
1240 | } | |
1241 | if (err) | |
1242 | nd->flags |= LOOKUP_JUMPED; | |
1243 | return 0; | |
1244 | } | |
1245 | ||
1246 | static inline int may_lookup(struct nameidata *nd) | |
1247 | { | |
1248 | if (nd->flags & LOOKUP_RCU) { | |
1249 | int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK); | |
1250 | if (err != -ECHILD) | |
1251 | return err; | |
1252 | if (unlazy_walk(nd, NULL)) | |
1253 | return -ECHILD; | |
1254 | } | |
1255 | return inode_permission(nd->inode, MAY_EXEC); | |
1256 | } | |
1257 | ||
1258 | static inline int handle_dots(struct nameidata *nd, int type) | |
1259 | { | |
1260 | if (type == LAST_DOTDOT) { | |
1261 | if (nd->flags & LOOKUP_RCU) { | |
1262 | if (follow_dotdot_rcu(nd)) | |
1263 | return -ECHILD; | |
1264 | } else | |
1265 | follow_dotdot(nd); | |
1266 | } | |
1267 | return 0; | |
1268 | } | |
1269 | ||
1270 | static void terminate_walk(struct nameidata *nd) | |
1271 | { | |
1272 | if (!(nd->flags & LOOKUP_RCU)) { | |
1273 | path_put(&nd->path); | |
1274 | } else { | |
1275 | nd->flags &= ~LOOKUP_RCU; | |
1276 | if (!(nd->flags & LOOKUP_ROOT)) | |
1277 | nd->root.mnt = NULL; | |
1278 | rcu_read_unlock(); | |
1279 | br_read_unlock(&vfsmount_lock); | |
1280 | } | |
1281 | } | |
1282 | ||
1283 | /* | |
1284 | * Do we need to follow links? We _really_ want to be able | |
1285 | * to do this check without having to look at inode->i_op, | |
1286 | * so we keep a cache of "no, this doesn't need follow_link" | |
1287 | * for the common case. | |
1288 | */ | |
1289 | static inline int should_follow_link(struct inode *inode, int follow) | |
1290 | { | |
1291 | if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) { | |
1292 | if (likely(inode->i_op->follow_link)) | |
1293 | return follow; | |
1294 | ||
1295 | /* This gets set once for the inode lifetime */ | |
1296 | spin_lock(&inode->i_lock); | |
1297 | inode->i_opflags |= IOP_NOFOLLOW; | |
1298 | spin_unlock(&inode->i_lock); | |
1299 | } | |
1300 | return 0; | |
1301 | } | |
1302 | ||
1303 | static inline int walk_component(struct nameidata *nd, struct path *path, | |
1304 | struct qstr *name, int type, int follow) | |
1305 | { | |
1306 | struct inode *inode; | |
1307 | int err; | |
1308 | /* | |
1309 | * "." and ".." are special - ".." especially so because it has | |
1310 | * to be able to know about the current root directory and | |
1311 | * parent relationships. | |
1312 | */ | |
1313 | if (unlikely(type != LAST_NORM)) | |
1314 | return handle_dots(nd, type); | |
1315 | err = lookup_fast(nd, name, path, &inode); | |
1316 | if (unlikely(err)) { | |
1317 | if (err < 0) | |
1318 | goto out_err; | |
1319 | ||
1320 | err = lookup_slow(nd, name, path); | |
1321 | if (err < 0) | |
1322 | goto out_err; | |
1323 | ||
1324 | inode = path->dentry->d_inode; | |
1325 | } | |
1326 | err = -ENOENT; | |
1327 | if (!inode) | |
1328 | goto out_path_put; | |
1329 | ||
1330 | if (should_follow_link(inode, follow)) { | |
1331 | if (nd->flags & LOOKUP_RCU) { | |
1332 | if (unlikely(unlazy_walk(nd, path->dentry))) { | |
1333 | err = -ECHILD; | |
1334 | goto out_err; | |
1335 | } | |
1336 | } | |
1337 | BUG_ON(inode != path->dentry->d_inode); | |
1338 | return 1; | |
1339 | } | |
1340 | path_to_nameidata(path, nd); | |
1341 | nd->inode = inode; | |
1342 | return 0; | |
1343 | ||
1344 | out_path_put: | |
1345 | path_to_nameidata(path, nd); | |
1346 | out_err: | |
1347 | terminate_walk(nd); | |
1348 | return err; | |
1349 | } | |
1350 | ||
1351 | /* | |
1352 | * This limits recursive symlink follows to 8, while | |
1353 | * limiting consecutive symlinks to 40. | |
1354 | * | |
1355 | * Without that kind of total limit, nasty chains of consecutive | |
1356 | * symlinks can cause almost arbitrarily long lookups. | |
1357 | */ | |
1358 | static inline int nested_symlink(struct path *path, struct nameidata *nd) | |
1359 | { | |
1360 | int res; | |
1361 | ||
1362 | if (unlikely(current->link_count >= MAX_NESTED_LINKS)) { | |
1363 | path_put_conditional(path, nd); | |
1364 | path_put(&nd->path); | |
1365 | return -ELOOP; | |
1366 | } | |
1367 | BUG_ON(nd->depth >= MAX_NESTED_LINKS); | |
1368 | ||
1369 | nd->depth++; | |
1370 | current->link_count++; | |
1371 | ||
1372 | do { | |
1373 | struct path link = *path; | |
1374 | void *cookie; | |
1375 | ||
1376 | res = follow_link(&link, nd, &cookie); | |
1377 | if (res) | |
1378 | break; | |
1379 | res = walk_component(nd, path, &nd->last, | |
1380 | nd->last_type, LOOKUP_FOLLOW); | |
1381 | put_link(nd, &link, cookie); | |
1382 | } while (res > 0); | |
1383 | ||
1384 | current->link_count--; | |
1385 | nd->depth--; | |
1386 | return res; | |
1387 | } | |
1388 | ||
1389 | /* | |
1390 | * We really don't want to look at inode->i_op->lookup | |
1391 | * when we don't have to. So we keep a cache bit in | |
1392 | * the inode ->i_opflags field that says "yes, we can | |
1393 | * do lookup on this inode". | |
1394 | */ | |
1395 | static inline int can_lookup(struct inode *inode) | |
1396 | { | |
1397 | if (likely(inode->i_opflags & IOP_LOOKUP)) | |
1398 | return 1; | |
1399 | if (likely(!inode->i_op->lookup)) | |
1400 | return 0; | |
1401 | ||
1402 | /* We do this once for the lifetime of the inode */ | |
1403 | spin_lock(&inode->i_lock); | |
1404 | inode->i_opflags |= IOP_LOOKUP; | |
1405 | spin_unlock(&inode->i_lock); | |
1406 | return 1; | |
1407 | } | |
1408 | ||
1409 | /* | |
1410 | * We can do the critical dentry name comparison and hashing | |
1411 | * operations one word at a time, but we are limited to: | |
1412 | * | |
1413 | * - Architectures with fast unaligned word accesses. We could | |
1414 | * do a "get_unaligned()" if this helps and is sufficiently | |
1415 | * fast. | |
1416 | * | |
1417 | * - Little-endian machines (so that we can generate the mask | |
1418 | * of low bytes efficiently). Again, we *could* do a byte | |
1419 | * swapping load on big-endian architectures if that is not | |
1420 | * expensive enough to make the optimization worthless. | |
1421 | * | |
1422 | * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we | |
1423 | * do not trap on the (extremely unlikely) case of a page | |
1424 | * crossing operation. | |
1425 | * | |
1426 | * - Furthermore, we need an efficient 64-bit compile for the | |
1427 | * 64-bit case in order to generate the "number of bytes in | |
1428 | * the final mask". Again, that could be replaced with a | |
1429 | * efficient population count instruction or similar. | |
1430 | */ | |
1431 | #ifdef CONFIG_DCACHE_WORD_ACCESS | |
1432 | ||
1433 | #include <asm/word-at-a-time.h> | |
1434 | ||
1435 | #ifdef CONFIG_64BIT | |
1436 | ||
1437 | static inline unsigned int fold_hash(unsigned long hash) | |
1438 | { | |
1439 | hash += hash >> (8*sizeof(int)); | |
1440 | return hash; | |
1441 | } | |
1442 | ||
1443 | #else /* 32-bit case */ | |
1444 | ||
1445 | #define fold_hash(x) (x) | |
1446 | ||
1447 | #endif | |
1448 | ||
1449 | unsigned int full_name_hash(const unsigned char *name, unsigned int len) | |
1450 | { | |
1451 | unsigned long a, mask; | |
1452 | unsigned long hash = 0; | |
1453 | ||
1454 | for (;;) { | |
1455 | a = load_unaligned_zeropad(name); | |
1456 | if (len < sizeof(unsigned long)) | |
1457 | break; | |
1458 | hash += a; | |
1459 | hash *= 9; | |
1460 | name += sizeof(unsigned long); | |
1461 | len -= sizeof(unsigned long); | |
1462 | if (!len) | |
1463 | goto done; | |
1464 | } | |
1465 | mask = ~(~0ul << len*8); | |
1466 | hash += mask & a; | |
1467 | done: | |
1468 | return fold_hash(hash); | |
1469 | } | |
1470 | EXPORT_SYMBOL(full_name_hash); | |
1471 | ||
1472 | /* | |
1473 | * Calculate the length and hash of the path component, and | |
1474 | * return the length of the component; | |
1475 | */ | |
1476 | static inline unsigned long hash_name(const char *name, unsigned int *hashp) | |
1477 | { | |
1478 | unsigned long a, b, adata, bdata, mask, hash, len; | |
1479 | const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS; | |
1480 | ||
1481 | hash = a = 0; | |
1482 | len = -sizeof(unsigned long); | |
1483 | do { | |
1484 | hash = (hash + a) * 9; | |
1485 | len += sizeof(unsigned long); | |
1486 | a = load_unaligned_zeropad(name+len); | |
1487 | b = a ^ REPEAT_BYTE('/'); | |
1488 | } while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants))); | |
1489 | ||
1490 | adata = prep_zero_mask(a, adata, &constants); | |
1491 | bdata = prep_zero_mask(b, bdata, &constants); | |
1492 | ||
1493 | mask = create_zero_mask(adata | bdata); | |
1494 | ||
1495 | hash += a & zero_bytemask(mask); | |
1496 | *hashp = fold_hash(hash); | |
1497 | ||
1498 | return len + find_zero(mask); | |
1499 | } | |
1500 | ||
1501 | #else | |
1502 | ||
1503 | unsigned int full_name_hash(const unsigned char *name, unsigned int len) | |
1504 | { | |
1505 | unsigned long hash = init_name_hash(); | |
1506 | while (len--) | |
1507 | hash = partial_name_hash(*name++, hash); | |
1508 | return end_name_hash(hash); | |
1509 | } | |
1510 | EXPORT_SYMBOL(full_name_hash); | |
1511 | ||
1512 | /* | |
1513 | * We know there's a real path component here of at least | |
1514 | * one character. | |
1515 | */ | |
1516 | static inline unsigned long hash_name(const char *name, unsigned int *hashp) | |
1517 | { | |
1518 | unsigned long hash = init_name_hash(); | |
1519 | unsigned long len = 0, c; | |
1520 | ||
1521 | c = (unsigned char)*name; | |
1522 | do { | |
1523 | len++; | |
1524 | hash = partial_name_hash(c, hash); | |
1525 | c = (unsigned char)name[len]; | |
1526 | } while (c && c != '/'); | |
1527 | *hashp = end_name_hash(hash); | |
1528 | return len; | |
1529 | } | |
1530 | ||
1531 | #endif | |
1532 | ||
1533 | /* | |
1534 | * Name resolution. | |
1535 | * This is the basic name resolution function, turning a pathname into | |
1536 | * the final dentry. We expect 'base' to be positive and a directory. | |
1537 | * | |
1538 | * Returns 0 and nd will have valid dentry and mnt on success. | |
1539 | * Returns error and drops reference to input namei data on failure. | |
1540 | */ | |
1541 | static int link_path_walk(const char *name, struct nameidata *nd) | |
1542 | { | |
1543 | struct path next; | |
1544 | int err; | |
1545 | ||
1546 | while (*name=='/') | |
1547 | name++; | |
1548 | if (!*name) | |
1549 | return 0; | |
1550 | ||
1551 | /* At this point we know we have a real path component. */ | |
1552 | for(;;) { | |
1553 | struct qstr this; | |
1554 | long len; | |
1555 | int type; | |
1556 | ||
1557 | err = may_lookup(nd); | |
1558 | if (err) | |
1559 | break; | |
1560 | ||
1561 | len = hash_name(name, &this.hash); | |
1562 | this.name = name; | |
1563 | this.len = len; | |
1564 | ||
1565 | type = LAST_NORM; | |
1566 | if (name[0] == '.') switch (len) { | |
1567 | case 2: | |
1568 | if (name[1] == '.') { | |
1569 | type = LAST_DOTDOT; | |
1570 | nd->flags |= LOOKUP_JUMPED; | |
1571 | } | |
1572 | break; | |
1573 | case 1: | |
1574 | type = LAST_DOT; | |
1575 | } | |
1576 | if (likely(type == LAST_NORM)) { | |
1577 | struct dentry *parent = nd->path.dentry; | |
1578 | nd->flags &= ~LOOKUP_JUMPED; | |
1579 | if (unlikely(parent->d_flags & DCACHE_OP_HASH)) { | |
1580 | err = parent->d_op->d_hash(parent, nd->inode, | |
1581 | &this); | |
1582 | if (err < 0) | |
1583 | break; | |
1584 | } | |
1585 | } | |
1586 | ||
1587 | if (!name[len]) | |
1588 | goto last_component; | |
1589 | /* | |
1590 | * If it wasn't NUL, we know it was '/'. Skip that | |
1591 | * slash, and continue until no more slashes. | |
1592 | */ | |
1593 | do { | |
1594 | len++; | |
1595 | } while (unlikely(name[len] == '/')); | |
1596 | if (!name[len]) | |
1597 | goto last_component; | |
1598 | name += len; | |
1599 | ||
1600 | err = walk_component(nd, &next, &this, type, LOOKUP_FOLLOW); | |
1601 | if (err < 0) | |
1602 | return err; | |
1603 | ||
1604 | if (err) { | |
1605 | err = nested_symlink(&next, nd); | |
1606 | if (err) | |
1607 | return err; | |
1608 | } | |
1609 | if (can_lookup(nd->inode)) | |
1610 | continue; | |
1611 | err = -ENOTDIR; | |
1612 | break; | |
1613 | /* here ends the main loop */ | |
1614 | ||
1615 | last_component: | |
1616 | nd->last = this; | |
1617 | nd->last_type = type; | |
1618 | return 0; | |
1619 | } | |
1620 | terminate_walk(nd); | |
1621 | return err; | |
1622 | } | |
1623 | ||
1624 | static int path_init(int dfd, const char *name, unsigned int flags, | |
1625 | struct nameidata *nd, struct file **fp) | |
1626 | { | |
1627 | int retval = 0; | |
1628 | int fput_needed; | |
1629 | struct file *file; | |
1630 | ||
1631 | nd->last_type = LAST_ROOT; /* if there are only slashes... */ | |
1632 | nd->flags = flags | LOOKUP_JUMPED; | |
1633 | nd->depth = 0; | |
1634 | if (flags & LOOKUP_ROOT) { | |
1635 | struct inode *inode = nd->root.dentry->d_inode; | |
1636 | if (*name) { | |
1637 | if (!inode->i_op->lookup) | |
1638 | return -ENOTDIR; | |
1639 | retval = inode_permission(inode, MAY_EXEC); | |
1640 | if (retval) | |
1641 | return retval; | |
1642 | } | |
1643 | nd->path = nd->root; | |
1644 | nd->inode = inode; | |
1645 | if (flags & LOOKUP_RCU) { | |
1646 | br_read_lock(&vfsmount_lock); | |
1647 | rcu_read_lock(); | |
1648 | nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); | |
1649 | } else { | |
1650 | path_get(&nd->path); | |
1651 | } | |
1652 | return 0; | |
1653 | } | |
1654 | ||
1655 | nd->root.mnt = NULL; | |
1656 | ||
1657 | if (*name=='/') { | |
1658 | if (flags & LOOKUP_RCU) { | |
1659 | br_read_lock(&vfsmount_lock); | |
1660 | rcu_read_lock(); | |
1661 | set_root_rcu(nd); | |
1662 | } else { | |
1663 | set_root(nd); | |
1664 | path_get(&nd->root); | |
1665 | } | |
1666 | nd->path = nd->root; | |
1667 | } else if (dfd == AT_FDCWD) { | |
1668 | if (flags & LOOKUP_RCU) { | |
1669 | struct fs_struct *fs = current->fs; | |
1670 | unsigned seq; | |
1671 | ||
1672 | br_read_lock(&vfsmount_lock); | |
1673 | rcu_read_lock(); | |
1674 | ||
1675 | do { | |
1676 | seq = read_seqcount_begin(&fs->seq); | |
1677 | nd->path = fs->pwd; | |
1678 | nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); | |
1679 | } while (read_seqcount_retry(&fs->seq, seq)); | |
1680 | } else { | |
1681 | get_fs_pwd(current->fs, &nd->path); | |
1682 | } | |
1683 | } else { | |
1684 | struct dentry *dentry; | |
1685 | ||
1686 | file = fget_raw_light(dfd, &fput_needed); | |
1687 | retval = -EBADF; | |
1688 | if (!file) | |
1689 | goto out_fail; | |
1690 | ||
1691 | dentry = file->f_path.dentry; | |
1692 | ||
1693 | if (*name) { | |
1694 | retval = -ENOTDIR; | |
1695 | if (!S_ISDIR(dentry->d_inode->i_mode)) | |
1696 | goto fput_fail; | |
1697 | ||
1698 | retval = inode_permission(dentry->d_inode, MAY_EXEC); | |
1699 | if (retval) | |
1700 | goto fput_fail; | |
1701 | } | |
1702 | ||
1703 | nd->path = file->f_path; | |
1704 | if (flags & LOOKUP_RCU) { | |
1705 | if (fput_needed) | |
1706 | *fp = file; | |
1707 | nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq); | |
1708 | br_read_lock(&vfsmount_lock); | |
1709 | rcu_read_lock(); | |
1710 | } else { | |
1711 | path_get(&file->f_path); | |
1712 | fput_light(file, fput_needed); | |
1713 | } | |
1714 | } | |
1715 | ||
1716 | nd->inode = nd->path.dentry->d_inode; | |
1717 | return 0; | |
1718 | ||
1719 | fput_fail: | |
1720 | fput_light(file, fput_needed); | |
1721 | out_fail: | |
1722 | return retval; | |
1723 | } | |
1724 | ||
1725 | static inline int lookup_last(struct nameidata *nd, struct path *path) | |
1726 | { | |
1727 | if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len]) | |
1728 | nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; | |
1729 | ||
1730 | nd->flags &= ~LOOKUP_PARENT; | |
1731 | return walk_component(nd, path, &nd->last, nd->last_type, | |
1732 | nd->flags & LOOKUP_FOLLOW); | |
1733 | } | |
1734 | ||
1735 | /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */ | |
1736 | static int path_lookupat(int dfd, const char *name, | |
1737 | unsigned int flags, struct nameidata *nd) | |
1738 | { | |
1739 | struct file *base = NULL; | |
1740 | struct path path; | |
1741 | int err; | |
1742 | ||
1743 | /* | |
1744 | * Path walking is largely split up into 2 different synchronisation | |
1745 | * schemes, rcu-walk and ref-walk (explained in | |
1746 | * Documentation/filesystems/path-lookup.txt). These share much of the | |
1747 | * path walk code, but some things particularly setup, cleanup, and | |
1748 | * following mounts are sufficiently divergent that functions are | |
1749 | * duplicated. Typically there is a function foo(), and its RCU | |
1750 | * analogue, foo_rcu(). | |
1751 | * | |
1752 | * -ECHILD is the error number of choice (just to avoid clashes) that | |
1753 | * is returned if some aspect of an rcu-walk fails. Such an error must | |
1754 | * be handled by restarting a traditional ref-walk (which will always | |
1755 | * be able to complete). | |
1756 | */ | |
1757 | err = path_init(dfd, name, flags | LOOKUP_PARENT, nd, &base); | |
1758 | ||
1759 | if (unlikely(err)) | |
1760 | return err; | |
1761 | ||
1762 | current->total_link_count = 0; | |
1763 | err = link_path_walk(name, nd); | |
1764 | ||
1765 | if (!err && !(flags & LOOKUP_PARENT)) { | |
1766 | err = lookup_last(nd, &path); | |
1767 | while (err > 0) { | |
1768 | void *cookie; | |
1769 | struct path link = path; | |
1770 | nd->flags |= LOOKUP_PARENT; | |
1771 | err = follow_link(&link, nd, &cookie); | |
1772 | if (err) | |
1773 | break; | |
1774 | err = lookup_last(nd, &path); | |
1775 | put_link(nd, &link, cookie); | |
1776 | } | |
1777 | } | |
1778 | ||
1779 | if (!err) | |
1780 | err = complete_walk(nd); | |
1781 | ||
1782 | if (!err && nd->flags & LOOKUP_DIRECTORY) { | |
1783 | if (!nd->inode->i_op->lookup) { | |
1784 | path_put(&nd->path); | |
1785 | err = -ENOTDIR; | |
1786 | } | |
1787 | } | |
1788 | ||
1789 | if (base) | |
1790 | fput(base); | |
1791 | ||
1792 | if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) { | |
1793 | path_put(&nd->root); | |
1794 | nd->root.mnt = NULL; | |
1795 | } | |
1796 | return err; | |
1797 | } | |
1798 | ||
1799 | static int do_path_lookup(int dfd, const char *name, | |
1800 | unsigned int flags, struct nameidata *nd) | |
1801 | { | |
1802 | int retval = path_lookupat(dfd, name, flags | LOOKUP_RCU, nd); | |
1803 | if (unlikely(retval == -ECHILD)) | |
1804 | retval = path_lookupat(dfd, name, flags, nd); | |
1805 | if (unlikely(retval == -ESTALE)) | |
1806 | retval = path_lookupat(dfd, name, flags | LOOKUP_REVAL, nd); | |
1807 | ||
1808 | if (likely(!retval)) { | |
1809 | if (unlikely(!audit_dummy_context())) { | |
1810 | if (nd->path.dentry && nd->inode) | |
1811 | audit_inode(name, nd->path.dentry); | |
1812 | } | |
1813 | } | |
1814 | return retval; | |
1815 | } | |
1816 | ||
1817 | int kern_path_parent(const char *name, struct nameidata *nd) | |
1818 | { | |
1819 | return do_path_lookup(AT_FDCWD, name, LOOKUP_PARENT, nd); | |
1820 | } | |
1821 | ||
1822 | int kern_path(const char *name, unsigned int flags, struct path *path) | |
1823 | { | |
1824 | struct nameidata nd; | |
1825 | int res = do_path_lookup(AT_FDCWD, name, flags, &nd); | |
1826 | if (!res) | |
1827 | *path = nd.path; | |
1828 | return res; | |
1829 | } | |
1830 | ||
1831 | /** | |
1832 | * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair | |
1833 | * @dentry: pointer to dentry of the base directory | |
1834 | * @mnt: pointer to vfs mount of the base directory | |
1835 | * @name: pointer to file name | |
1836 | * @flags: lookup flags | |
1837 | * @path: pointer to struct path to fill | |
1838 | */ | |
1839 | int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt, | |
1840 | const char *name, unsigned int flags, | |
1841 | struct path *path) | |
1842 | { | |
1843 | struct nameidata nd; | |
1844 | int err; | |
1845 | nd.root.dentry = dentry; | |
1846 | nd.root.mnt = mnt; | |
1847 | BUG_ON(flags & LOOKUP_PARENT); | |
1848 | /* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */ | |
1849 | err = do_path_lookup(AT_FDCWD, name, flags | LOOKUP_ROOT, &nd); | |
1850 | if (!err) | |
1851 | *path = nd.path; | |
1852 | return err; | |
1853 | } | |
1854 | ||
1855 | /* | |
1856 | * Restricted form of lookup. Doesn't follow links, single-component only, | |
1857 | * needs parent already locked. Doesn't follow mounts. | |
1858 | * SMP-safe. | |
1859 | */ | |
1860 | static struct dentry *lookup_hash(struct nameidata *nd) | |
1861 | { | |
1862 | return __lookup_hash(&nd->last, nd->path.dentry, nd); | |
1863 | } | |
1864 | ||
1865 | /** | |
1866 | * lookup_one_len - filesystem helper to lookup single pathname component | |
1867 | * @name: pathname component to lookup | |
1868 | * @base: base directory to lookup from | |
1869 | * @len: maximum length @len should be interpreted to | |
1870 | * | |
1871 | * Note that this routine is purely a helper for filesystem usage and should | |
1872 | * not be called by generic code. Also note that by using this function the | |
1873 | * nameidata argument is passed to the filesystem methods and a filesystem | |
1874 | * using this helper needs to be prepared for that. | |
1875 | */ | |
1876 | struct dentry *lookup_one_len(const char *name, struct dentry *base, int len) | |
1877 | { | |
1878 | struct qstr this; | |
1879 | unsigned int c; | |
1880 | int err; | |
1881 | ||
1882 | WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex)); | |
1883 | ||
1884 | this.name = name; | |
1885 | this.len = len; | |
1886 | this.hash = full_name_hash(name, len); | |
1887 | if (!len) | |
1888 | return ERR_PTR(-EACCES); | |
1889 | ||
1890 | while (len--) { | |
1891 | c = *(const unsigned char *)name++; | |
1892 | if (c == '/' || c == '\0') | |
1893 | return ERR_PTR(-EACCES); | |
1894 | } | |
1895 | /* | |
1896 | * See if the low-level filesystem might want | |
1897 | * to use its own hash.. | |
1898 | */ | |
1899 | if (base->d_flags & DCACHE_OP_HASH) { | |
1900 | int err = base->d_op->d_hash(base, base->d_inode, &this); | |
1901 | if (err < 0) | |
1902 | return ERR_PTR(err); | |
1903 | } | |
1904 | ||
1905 | err = inode_permission(base->d_inode, MAY_EXEC); | |
1906 | if (err) | |
1907 | return ERR_PTR(err); | |
1908 | ||
1909 | return __lookup_hash(&this, base, NULL); | |
1910 | } | |
1911 | ||
1912 | int user_path_at_empty(int dfd, const char __user *name, unsigned flags, | |
1913 | struct path *path, int *empty) | |
1914 | { | |
1915 | struct nameidata nd; | |
1916 | char *tmp = getname_flags(name, flags, empty); | |
1917 | int err = PTR_ERR(tmp); | |
1918 | if (!IS_ERR(tmp)) { | |
1919 | ||
1920 | BUG_ON(flags & LOOKUP_PARENT); | |
1921 | ||
1922 | err = do_path_lookup(dfd, tmp, flags, &nd); | |
1923 | putname(tmp); | |
1924 | if (!err) | |
1925 | *path = nd.path; | |
1926 | } | |
1927 | return err; | |
1928 | } | |
1929 | ||
1930 | int user_path_at(int dfd, const char __user *name, unsigned flags, | |
1931 | struct path *path) | |
1932 | { | |
1933 | return user_path_at_empty(dfd, name, flags, path, NULL); | |
1934 | } | |
1935 | ||
1936 | static int user_path_parent(int dfd, const char __user *path, | |
1937 | struct nameidata *nd, char **name) | |
1938 | { | |
1939 | char *s = getname(path); | |
1940 | int error; | |
1941 | ||
1942 | if (IS_ERR(s)) | |
1943 | return PTR_ERR(s); | |
1944 | ||
1945 | error = do_path_lookup(dfd, s, LOOKUP_PARENT, nd); | |
1946 | if (error) | |
1947 | putname(s); | |
1948 | else | |
1949 | *name = s; | |
1950 | ||
1951 | return error; | |
1952 | } | |
1953 | ||
1954 | /* | |
1955 | * It's inline, so penalty for filesystems that don't use sticky bit is | |
1956 | * minimal. | |
1957 | */ | |
1958 | static inline int check_sticky(struct inode *dir, struct inode *inode) | |
1959 | { | |
1960 | kuid_t fsuid = current_fsuid(); | |
1961 | ||
1962 | if (!(dir->i_mode & S_ISVTX)) | |
1963 | return 0; | |
1964 | if (uid_eq(inode->i_uid, fsuid)) | |
1965 | return 0; | |
1966 | if (uid_eq(dir->i_uid, fsuid)) | |
1967 | return 0; | |
1968 | return !inode_capable(inode, CAP_FOWNER); | |
1969 | } | |
1970 | ||
1971 | /* | |
1972 | * Check whether we can remove a link victim from directory dir, check | |
1973 | * whether the type of victim is right. | |
1974 | * 1. We can't do it if dir is read-only (done in permission()) | |
1975 | * 2. We should have write and exec permissions on dir | |
1976 | * 3. We can't remove anything from append-only dir | |
1977 | * 4. We can't do anything with immutable dir (done in permission()) | |
1978 | * 5. If the sticky bit on dir is set we should either | |
1979 | * a. be owner of dir, or | |
1980 | * b. be owner of victim, or | |
1981 | * c. have CAP_FOWNER capability | |
1982 | * 6. If the victim is append-only or immutable we can't do antyhing with | |
1983 | * links pointing to it. | |
1984 | * 7. If we were asked to remove a directory and victim isn't one - ENOTDIR. | |
1985 | * 8. If we were asked to remove a non-directory and victim isn't one - EISDIR. | |
1986 | * 9. We can't remove a root or mountpoint. | |
1987 | * 10. We don't allow removal of NFS sillyrenamed files; it's handled by | |
1988 | * nfs_async_unlink(). | |
1989 | */ | |
1990 | static int may_delete(struct inode *dir,struct dentry *victim,int isdir) | |
1991 | { | |
1992 | int error; | |
1993 | ||
1994 | if (!victim->d_inode) | |
1995 | return -ENOENT; | |
1996 | ||
1997 | BUG_ON(victim->d_parent->d_inode != dir); | |
1998 | audit_inode_child(victim, dir); | |
1999 | ||
2000 | error = inode_permission(dir, MAY_WRITE | MAY_EXEC); | |
2001 | if (error) | |
2002 | return error; | |
2003 | if (IS_APPEND(dir)) | |
2004 | return -EPERM; | |
2005 | if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)|| | |
2006 | IS_IMMUTABLE(victim->d_inode) || IS_SWAPFILE(victim->d_inode)) | |
2007 | return -EPERM; | |
2008 | if (isdir) { | |
2009 | if (!S_ISDIR(victim->d_inode->i_mode)) | |
2010 | return -ENOTDIR; | |
2011 | if (IS_ROOT(victim)) | |
2012 | return -EBUSY; | |
2013 | } else if (S_ISDIR(victim->d_inode->i_mode)) | |
2014 | return -EISDIR; | |
2015 | if (IS_DEADDIR(dir)) | |
2016 | return -ENOENT; | |
2017 | if (victim->d_flags & DCACHE_NFSFS_RENAMED) | |
2018 | return -EBUSY; | |
2019 | return 0; | |
2020 | } | |
2021 | ||
2022 | /* Check whether we can create an object with dentry child in directory | |
2023 | * dir. | |
2024 | * 1. We can't do it if child already exists (open has special treatment for | |
2025 | * this case, but since we are inlined it's OK) | |
2026 | * 2. We can't do it if dir is read-only (done in permission()) | |
2027 | * 3. We should have write and exec permissions on dir | |
2028 | * 4. We can't do it if dir is immutable (done in permission()) | |
2029 | */ | |
2030 | static inline int may_create(struct inode *dir, struct dentry *child) | |
2031 | { | |
2032 | if (child->d_inode) | |
2033 | return -EEXIST; | |
2034 | if (IS_DEADDIR(dir)) | |
2035 | return -ENOENT; | |
2036 | return inode_permission(dir, MAY_WRITE | MAY_EXEC); | |
2037 | } | |
2038 | ||
2039 | /* | |
2040 | * p1 and p2 should be directories on the same fs. | |
2041 | */ | |
2042 | struct dentry *lock_rename(struct dentry *p1, struct dentry *p2) | |
2043 | { | |
2044 | struct dentry *p; | |
2045 | ||
2046 | if (p1 == p2) { | |
2047 | mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT); | |
2048 | return NULL; | |
2049 | } | |
2050 | ||
2051 | mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex); | |
2052 | ||
2053 | p = d_ancestor(p2, p1); | |
2054 | if (p) { | |
2055 | mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT); | |
2056 | mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD); | |
2057 | return p; | |
2058 | } | |
2059 | ||
2060 | p = d_ancestor(p1, p2); | |
2061 | if (p) { | |
2062 | mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT); | |
2063 | mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD); | |
2064 | return p; | |
2065 | } | |
2066 | ||
2067 | mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT); | |
2068 | mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD); | |
2069 | return NULL; | |
2070 | } | |
2071 | ||
2072 | void unlock_rename(struct dentry *p1, struct dentry *p2) | |
2073 | { | |
2074 | mutex_unlock(&p1->d_inode->i_mutex); | |
2075 | if (p1 != p2) { | |
2076 | mutex_unlock(&p2->d_inode->i_mutex); | |
2077 | mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex); | |
2078 | } | |
2079 | } | |
2080 | ||
2081 | int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, | |
2082 | struct nameidata *nd) | |
2083 | { | |
2084 | int error = may_create(dir, dentry); | |
2085 | ||
2086 | if (error) | |
2087 | return error; | |
2088 | ||
2089 | if (!dir->i_op->create) | |
2090 | return -EACCES; /* shouldn't it be ENOSYS? */ | |
2091 | mode &= S_IALLUGO; | |
2092 | mode |= S_IFREG; | |
2093 | error = security_inode_create(dir, dentry, mode); | |
2094 | if (error) | |
2095 | return error; | |
2096 | error = dir->i_op->create(dir, dentry, mode, nd); | |
2097 | if (!error) | |
2098 | fsnotify_create(dir, dentry); | |
2099 | return error; | |
2100 | } | |
2101 | ||
2102 | static int may_open(struct path *path, int acc_mode, int flag) | |
2103 | { | |
2104 | struct dentry *dentry = path->dentry; | |
2105 | struct inode *inode = dentry->d_inode; | |
2106 | int error; | |
2107 | ||
2108 | /* O_PATH? */ | |
2109 | if (!acc_mode) | |
2110 | return 0; | |
2111 | ||
2112 | if (!inode) | |
2113 | return -ENOENT; | |
2114 | ||
2115 | switch (inode->i_mode & S_IFMT) { | |
2116 | case S_IFLNK: | |
2117 | return -ELOOP; | |
2118 | case S_IFDIR: | |
2119 | if (acc_mode & MAY_WRITE) | |
2120 | return -EISDIR; | |
2121 | break; | |
2122 | case S_IFBLK: | |
2123 | case S_IFCHR: | |
2124 | if (path->mnt->mnt_flags & MNT_NODEV) | |
2125 | return -EACCES; | |
2126 | /*FALLTHRU*/ | |
2127 | case S_IFIFO: | |
2128 | case S_IFSOCK: | |
2129 | flag &= ~O_TRUNC; | |
2130 | break; | |
2131 | } | |
2132 | ||
2133 | error = inode_permission(inode, acc_mode); | |
2134 | if (error) | |
2135 | return error; | |
2136 | ||
2137 | /* | |
2138 | * An append-only file must be opened in append mode for writing. | |
2139 | */ | |
2140 | if (IS_APPEND(inode)) { | |
2141 | if ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND)) | |
2142 | return -EPERM; | |
2143 | if (flag & O_TRUNC) | |
2144 | return -EPERM; | |
2145 | } | |
2146 | ||
2147 | /* O_NOATIME can only be set by the owner or superuser */ | |
2148 | if (flag & O_NOATIME && !inode_owner_or_capable(inode)) | |
2149 | return -EPERM; | |
2150 | ||
2151 | return 0; | |
2152 | } | |
2153 | ||
2154 | static int handle_truncate(struct file *filp) | |
2155 | { | |
2156 | struct path *path = &filp->f_path; | |
2157 | struct inode *inode = path->dentry->d_inode; | |
2158 | int error = get_write_access(inode); | |
2159 | if (error) | |
2160 | return error; | |
2161 | /* | |
2162 | * Refuse to truncate files with mandatory locks held on them. | |
2163 | */ | |
2164 | error = locks_verify_locked(inode); | |
2165 | if (!error) | |
2166 | error = security_path_truncate(path); | |
2167 | if (!error) { | |
2168 | error = do_truncate(path->dentry, 0, | |
2169 | ATTR_MTIME|ATTR_CTIME|ATTR_OPEN, | |
2170 | filp); | |
2171 | } | |
2172 | put_write_access(inode); | |
2173 | return error; | |
2174 | } | |
2175 | ||
2176 | static inline int open_to_namei_flags(int flag) | |
2177 | { | |
2178 | if ((flag & O_ACCMODE) == 3) | |
2179 | flag--; | |
2180 | return flag; | |
2181 | } | |
2182 | ||
2183 | static int may_o_create(struct path *dir, struct dentry *dentry, umode_t mode) | |
2184 | { | |
2185 | int error = security_path_mknod(dir, dentry, mode, 0); | |
2186 | if (error) | |
2187 | return error; | |
2188 | ||
2189 | error = inode_permission(dir->dentry->d_inode, MAY_WRITE | MAY_EXEC); | |
2190 | if (error) | |
2191 | return error; | |
2192 | ||
2193 | return security_inode_create(dir->dentry->d_inode, dentry, mode); | |
2194 | } | |
2195 | ||
2196 | static struct file *atomic_open(struct nameidata *nd, struct dentry *dentry, | |
2197 | struct path *path, struct opendata *od, | |
2198 | const struct open_flags *op, | |
2199 | bool *want_write, bool need_lookup, | |
2200 | int *opened) | |
2201 | { | |
2202 | struct inode *dir = nd->path.dentry->d_inode; | |
2203 | unsigned open_flag = open_to_namei_flags(op->open_flag); | |
2204 | umode_t mode; | |
2205 | int error; | |
2206 | int acc_mode; | |
2207 | struct file *filp; | |
2208 | int create_error = 0; | |
2209 | struct dentry *const DENTRY_NOT_SET = (void *) -1UL; | |
2210 | ||
2211 | BUG_ON(dentry->d_inode); | |
2212 | ||
2213 | /* Don't create child dentry for a dead directory. */ | |
2214 | if (unlikely(IS_DEADDIR(dir))) { | |
2215 | filp = ERR_PTR(-ENOENT); | |
2216 | goto out; | |
2217 | } | |
2218 | ||
2219 | mode = op->mode & S_IALLUGO; | |
2220 | if ((open_flag & O_CREAT) && !IS_POSIXACL(dir)) | |
2221 | mode &= ~current_umask(); | |
2222 | ||
2223 | if (open_flag & O_EXCL) { | |
2224 | open_flag &= ~O_TRUNC; | |
2225 | *opened |= FILE_CREATED; | |
2226 | } | |
2227 | ||
2228 | /* | |
2229 | * Checking write permission is tricky, bacuse we don't know if we are | |
2230 | * going to actually need it: O_CREAT opens should work as long as the | |
2231 | * file exists. But checking existence breaks atomicity. The trick is | |
2232 | * to check access and if not granted clear O_CREAT from the flags. | |
2233 | * | |
2234 | * Another problem is returing the "right" error value (e.g. for an | |
2235 | * O_EXCL open we want to return EEXIST not EROFS). | |
2236 | */ | |
2237 | if ((open_flag & (O_CREAT | O_TRUNC)) || | |
2238 | (open_flag & O_ACCMODE) != O_RDONLY) { | |
2239 | error = mnt_want_write(nd->path.mnt); | |
2240 | if (!error) { | |
2241 | *want_write = true; | |
2242 | } else if (!(open_flag & O_CREAT)) { | |
2243 | /* | |
2244 | * No O_CREATE -> atomicity not a requirement -> fall | |
2245 | * back to lookup + open | |
2246 | */ | |
2247 | goto no_open; | |
2248 | } else if (open_flag & (O_EXCL | O_TRUNC)) { | |
2249 | /* Fall back and fail with the right error */ | |
2250 | create_error = error; | |
2251 | goto no_open; | |
2252 | } else { | |
2253 | /* No side effects, safe to clear O_CREAT */ | |
2254 | create_error = error; | |
2255 | open_flag &= ~O_CREAT; | |
2256 | } | |
2257 | } | |
2258 | ||
2259 | if (open_flag & O_CREAT) { | |
2260 | error = may_o_create(&nd->path, dentry, op->mode); | |
2261 | if (error) { | |
2262 | create_error = error; | |
2263 | if (open_flag & O_EXCL) | |
2264 | goto no_open; | |
2265 | open_flag &= ~O_CREAT; | |
2266 | } | |
2267 | } | |
2268 | ||
2269 | if (nd->flags & LOOKUP_DIRECTORY) | |
2270 | open_flag |= O_DIRECTORY; | |
2271 | ||
2272 | od->dentry = DENTRY_NOT_SET; | |
2273 | od->mnt = nd->path.mnt; | |
2274 | filp = dir->i_op->atomic_open(dir, dentry, od, open_flag, mode, | |
2275 | opened); | |
2276 | if (IS_ERR(filp)) { | |
2277 | if (WARN_ON(od->dentry != DENTRY_NOT_SET)) | |
2278 | dput(od->dentry); | |
2279 | ||
2280 | if (create_error && PTR_ERR(filp) == -ENOENT) | |
2281 | filp = ERR_PTR(create_error); | |
2282 | goto out; | |
2283 | } | |
2284 | ||
2285 | acc_mode = op->acc_mode; | |
2286 | if (*opened & FILE_CREATED) { | |
2287 | fsnotify_create(dir, dentry); | |
2288 | acc_mode = MAY_OPEN; | |
2289 | } | |
2290 | ||
2291 | if (!filp) { | |
2292 | if (WARN_ON(od->dentry == DENTRY_NOT_SET)) { | |
2293 | filp = ERR_PTR(-EIO); | |
2294 | goto out; | |
2295 | } | |
2296 | if (od->dentry) { | |
2297 | dput(dentry); | |
2298 | dentry = od->dentry; | |
2299 | } | |
2300 | goto looked_up; | |
2301 | } | |
2302 | ||
2303 | /* | |
2304 | * We didn't have the inode before the open, so check open permission | |
2305 | * here. | |
2306 | */ | |
2307 | error = may_open(&filp->f_path, acc_mode, open_flag); | |
2308 | if (error) { | |
2309 | fput(filp); | |
2310 | filp = ERR_PTR(error); | |
2311 | } | |
2312 | ||
2313 | out: | |
2314 | dput(dentry); | |
2315 | return filp; | |
2316 | ||
2317 | no_open: | |
2318 | if (need_lookup) { | |
2319 | dentry = lookup_real(dir, dentry, nd); | |
2320 | if (IS_ERR(dentry)) | |
2321 | return ERR_CAST(dentry); | |
2322 | ||
2323 | if (create_error) { | |
2324 | int open_flag = op->open_flag; | |
2325 | ||
2326 | filp = ERR_PTR(create_error); | |
2327 | if ((open_flag & O_EXCL)) { | |
2328 | if (!dentry->d_inode) | |
2329 | goto out; | |
2330 | } else if (!dentry->d_inode) { | |
2331 | goto out; | |
2332 | } else if ((open_flag & O_TRUNC) && | |
2333 | S_ISREG(dentry->d_inode->i_mode)) { | |
2334 | goto out; | |
2335 | } | |
2336 | /* will fail later, go on to get the right error */ | |
2337 | } | |
2338 | } | |
2339 | looked_up: | |
2340 | path->dentry = dentry; | |
2341 | path->mnt = nd->path.mnt; | |
2342 | return NULL; | |
2343 | } | |
2344 | ||
2345 | /* | |
2346 | * Lookup, maybe create and open the last component | |
2347 | * | |
2348 | * Must be called with i_mutex held on parent. | |
2349 | * | |
2350 | * Returns open file or NULL on success, error otherwise. NULL means no open | |
2351 | * was performed, only lookup. | |
2352 | */ | |
2353 | static struct file *lookup_open(struct nameidata *nd, struct path *path, | |
2354 | struct opendata *od, | |
2355 | const struct open_flags *op, | |
2356 | bool *want_write, int *opened) | |
2357 | { | |
2358 | struct dentry *dir = nd->path.dentry; | |
2359 | struct inode *dir_inode = dir->d_inode; | |
2360 | struct dentry *dentry; | |
2361 | int error; | |
2362 | bool need_lookup; | |
2363 | ||
2364 | *opened &= ~FILE_CREATED; | |
2365 | dentry = lookup_dcache(&nd->last, dir, nd, &need_lookup); | |
2366 | if (IS_ERR(dentry)) | |
2367 | return ERR_CAST(dentry); | |
2368 | ||
2369 | /* Cached positive dentry: will open in f_op->open */ | |
2370 | if (!need_lookup && dentry->d_inode) | |
2371 | goto out_no_open; | |
2372 | ||
2373 | if ((nd->flags & LOOKUP_OPEN) && dir_inode->i_op->atomic_open) { | |
2374 | return atomic_open(nd, dentry, path, od, op, want_write, | |
2375 | need_lookup, opened); | |
2376 | } | |
2377 | ||
2378 | if (need_lookup) { | |
2379 | BUG_ON(dentry->d_inode); | |
2380 | ||
2381 | dentry = lookup_real(dir_inode, dentry, nd); | |
2382 | if (IS_ERR(dentry)) | |
2383 | return ERR_CAST(dentry); | |
2384 | } | |
2385 | ||
2386 | /* Negative dentry, just create the file */ | |
2387 | if (!dentry->d_inode && (op->open_flag & O_CREAT)) { | |
2388 | umode_t mode = op->mode; | |
2389 | if (!IS_POSIXACL(dir->d_inode)) | |
2390 | mode &= ~current_umask(); | |
2391 | /* | |
2392 | * This write is needed to ensure that a | |
2393 | * rw->ro transition does not occur between | |
2394 | * the time when the file is created and when | |
2395 | * a permanent write count is taken through | |
2396 | * the 'struct file' in finish_open(). | |
2397 | */ | |
2398 | error = mnt_want_write(nd->path.mnt); | |
2399 | if (error) | |
2400 | goto out_dput; | |
2401 | *want_write = true; | |
2402 | *opened |= FILE_CREATED; | |
2403 | error = security_path_mknod(&nd->path, dentry, mode, 0); | |
2404 | if (error) | |
2405 | goto out_dput; | |
2406 | error = vfs_create(dir->d_inode, dentry, mode, nd); | |
2407 | if (error) | |
2408 | goto out_dput; | |
2409 | } | |
2410 | out_no_open: | |
2411 | path->dentry = dentry; | |
2412 | path->mnt = nd->path.mnt; | |
2413 | return NULL; | |
2414 | ||
2415 | out_dput: | |
2416 | dput(dentry); | |
2417 | return ERR_PTR(error); | |
2418 | } | |
2419 | ||
2420 | /* | |
2421 | * Handle the last step of open() | |
2422 | */ | |
2423 | static struct file *do_last(struct nameidata *nd, struct path *path, | |
2424 | struct opendata *od, const struct open_flags *op, | |
2425 | int *opened, const char *pathname) | |
2426 | { | |
2427 | struct dentry *dir = nd->path.dentry; | |
2428 | int open_flag = op->open_flag; | |
2429 | bool will_truncate = (open_flag & O_TRUNC) != 0; | |
2430 | bool want_write = false; | |
2431 | int acc_mode = op->acc_mode; | |
2432 | struct file *filp; | |
2433 | struct inode *inode; | |
2434 | bool symlink_ok = false; | |
2435 | struct path save_parent = { .dentry = NULL, .mnt = NULL }; | |
2436 | bool retried = false; | |
2437 | int error; | |
2438 | ||
2439 | nd->flags &= ~LOOKUP_PARENT; | |
2440 | nd->flags |= op->intent; | |
2441 | ||
2442 | switch (nd->last_type) { | |
2443 | case LAST_DOTDOT: | |
2444 | case LAST_DOT: | |
2445 | error = handle_dots(nd, nd->last_type); | |
2446 | if (error) | |
2447 | return ERR_PTR(error); | |
2448 | /* fallthrough */ | |
2449 | case LAST_ROOT: | |
2450 | error = complete_walk(nd); | |
2451 | if (error) | |
2452 | return ERR_PTR(error); | |
2453 | audit_inode(pathname, nd->path.dentry); | |
2454 | if (open_flag & O_CREAT) { | |
2455 | error = -EISDIR; | |
2456 | goto exit; | |
2457 | } | |
2458 | goto finish_open; | |
2459 | case LAST_BIND: | |
2460 | error = complete_walk(nd); | |
2461 | if (error) | |
2462 | return ERR_PTR(error); | |
2463 | audit_inode(pathname, dir); | |
2464 | goto finish_open; | |
2465 | } | |
2466 | ||
2467 | if (!(open_flag & O_CREAT)) { | |
2468 | if (nd->last.name[nd->last.len]) | |
2469 | nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; | |
2470 | if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW)) | |
2471 | symlink_ok = true; | |
2472 | /* we _can_ be in RCU mode here */ | |
2473 | error = lookup_fast(nd, &nd->last, path, &inode); | |
2474 | if (likely(!error)) | |
2475 | goto finish_lookup; | |
2476 | ||
2477 | if (error < 0) | |
2478 | goto exit; | |
2479 | ||
2480 | BUG_ON(nd->inode != dir->d_inode); | |
2481 | } else { | |
2482 | /* create side of things */ | |
2483 | /* | |
2484 | * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED | |
2485 | * has been cleared when we got to the last component we are | |
2486 | * about to look up | |
2487 | */ | |
2488 | error = complete_walk(nd); | |
2489 | if (error) | |
2490 | return ERR_PTR(error); | |
2491 | ||
2492 | audit_inode(pathname, dir); | |
2493 | error = -EISDIR; | |
2494 | /* trailing slashes? */ | |
2495 | if (nd->last.name[nd->last.len]) | |
2496 | goto exit; | |
2497 | } | |
2498 | ||
2499 | retry_lookup: | |
2500 | mutex_lock(&dir->d_inode->i_mutex); | |
2501 | filp = lookup_open(nd, path, od, op, &want_write, opened); | |
2502 | mutex_unlock(&dir->d_inode->i_mutex); | |
2503 | ||
2504 | if (filp) { | |
2505 | if (IS_ERR(filp)) | |
2506 | goto out; | |
2507 | ||
2508 | if ((*opened & FILE_CREATED) || | |
2509 | !S_ISREG(filp->f_path.dentry->d_inode->i_mode)) | |
2510 | will_truncate = false; | |
2511 | ||
2512 | audit_inode(pathname, filp->f_path.dentry); | |
2513 | goto opened; | |
2514 | } | |
2515 | ||
2516 | if (*opened & FILE_CREATED) { | |
2517 | /* Don't check for write permission, don't truncate */ | |
2518 | open_flag &= ~O_TRUNC; | |
2519 | will_truncate = false; | |
2520 | acc_mode = MAY_OPEN; | |
2521 | path_to_nameidata(path, nd); | |
2522 | goto finish_open_created; | |
2523 | } | |
2524 | ||
2525 | /* | |
2526 | * It already exists. | |
2527 | */ | |
2528 | audit_inode(pathname, path->dentry); | |
2529 | ||
2530 | /* | |
2531 | * If atomic_open() acquired write access it is dropped now due to | |
2532 | * possible mount and symlink following (this might be optimized away if | |
2533 | * necessary...) | |
2534 | */ | |
2535 | if (want_write) { | |
2536 | mnt_drop_write(nd->path.mnt); | |
2537 | want_write = false; | |
2538 | } | |
2539 | ||
2540 | error = -EEXIST; | |
2541 | if (open_flag & O_EXCL) | |
2542 | goto exit_dput; | |
2543 | ||
2544 | error = follow_managed(path, nd->flags); | |
2545 | if (error < 0) | |
2546 | goto exit_dput; | |
2547 | ||
2548 | if (error) | |
2549 | nd->flags |= LOOKUP_JUMPED; | |
2550 | ||
2551 | BUG_ON(nd->flags & LOOKUP_RCU); | |
2552 | inode = path->dentry->d_inode; | |
2553 | finish_lookup: | |
2554 | /* we _can_ be in RCU mode here */ | |
2555 | error = -ENOENT; | |
2556 | if (!inode) { | |
2557 | path_to_nameidata(path, nd); | |
2558 | goto exit; | |
2559 | } | |
2560 | ||
2561 | if (should_follow_link(inode, !symlink_ok)) { | |
2562 | if (nd->flags & LOOKUP_RCU) { | |
2563 | if (unlikely(unlazy_walk(nd, path->dentry))) { | |
2564 | error = -ECHILD; | |
2565 | goto exit; | |
2566 | } | |
2567 | } | |
2568 | BUG_ON(inode != path->dentry->d_inode); | |
2569 | return NULL; | |
2570 | } | |
2571 | ||
2572 | if ((nd->flags & LOOKUP_RCU) || nd->path.mnt != path->mnt) { | |
2573 | path_to_nameidata(path, nd); | |
2574 | } else { | |
2575 | save_parent.dentry = nd->path.dentry; | |
2576 | save_parent.mnt = mntget(path->mnt); | |
2577 | nd->path.dentry = path->dentry; | |
2578 | ||
2579 | } | |
2580 | nd->inode = inode; | |
2581 | /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */ | |
2582 | error = complete_walk(nd); | |
2583 | if (error) { | |
2584 | path_put(&save_parent); | |
2585 | return ERR_PTR(error); | |
2586 | } | |
2587 | error = -EISDIR; | |
2588 | if ((open_flag & O_CREAT) && S_ISDIR(nd->inode->i_mode)) | |
2589 | goto exit; | |
2590 | error = -ENOTDIR; | |
2591 | if ((nd->flags & LOOKUP_DIRECTORY) && !nd->inode->i_op->lookup) | |
2592 | goto exit; | |
2593 | audit_inode(pathname, nd->path.dentry); | |
2594 | finish_open: | |
2595 | if (!S_ISREG(nd->inode->i_mode)) | |
2596 | will_truncate = false; | |
2597 | ||
2598 | if (will_truncate) { | |
2599 | error = mnt_want_write(nd->path.mnt); | |
2600 | if (error) | |
2601 | goto exit; | |
2602 | want_write = true; | |
2603 | } | |
2604 | finish_open_created: | |
2605 | error = may_open(&nd->path, acc_mode, open_flag); | |
2606 | if (error) | |
2607 | goto exit; | |
2608 | od->mnt = nd->path.mnt; | |
2609 | filp = finish_open(od, nd->path.dentry, NULL, opened); | |
2610 | if (IS_ERR(filp)) { | |
2611 | if (filp == ERR_PTR(-EOPENSTALE)) | |
2612 | goto stale_open; | |
2613 | goto out; | |
2614 | } | |
2615 | opened: | |
2616 | error = open_check_o_direct(filp); | |
2617 | if (error) | |
2618 | goto exit_fput; | |
2619 | error = ima_file_check(filp, op->acc_mode); | |
2620 | if (error) | |
2621 | goto exit_fput; | |
2622 | ||
2623 | if (will_truncate) { | |
2624 | error = handle_truncate(filp); | |
2625 | if (error) | |
2626 | goto exit_fput; | |
2627 | } | |
2628 | out: | |
2629 | if (want_write) | |
2630 | mnt_drop_write(nd->path.mnt); | |
2631 | path_put(&save_parent); | |
2632 | terminate_walk(nd); | |
2633 | return filp; | |
2634 | ||
2635 | exit_dput: | |
2636 | path_put_conditional(path, nd); | |
2637 | exit: | |
2638 | filp = ERR_PTR(error); | |
2639 | goto out; | |
2640 | exit_fput: | |
2641 | fput(filp); | |
2642 | goto exit; | |
2643 | ||
2644 | stale_open: | |
2645 | /* If no saved parent or already retried then can't retry */ | |
2646 | if (!save_parent.dentry || retried) | |
2647 | goto out; | |
2648 | ||
2649 | BUG_ON(save_parent.dentry != dir); | |
2650 | path_put(&nd->path); | |
2651 | nd->path = save_parent; | |
2652 | nd->inode = dir->d_inode; | |
2653 | save_parent.mnt = NULL; | |
2654 | save_parent.dentry = NULL; | |
2655 | if (want_write) { | |
2656 | mnt_drop_write(nd->path.mnt); | |
2657 | want_write = false; | |
2658 | } | |
2659 | retried = true; | |
2660 | goto retry_lookup; | |
2661 | } | |
2662 | ||
2663 | static struct file *path_openat(int dfd, const char *pathname, | |
2664 | struct nameidata *nd, const struct open_flags *op, int flags) | |
2665 | { | |
2666 | struct file *base = NULL; | |
2667 | struct opendata od; | |
2668 | struct file *res; | |
2669 | struct path path; | |
2670 | int opened = 0; | |
2671 | int error; | |
2672 | ||
2673 | od.filp = get_empty_filp(); | |
2674 | if (!od.filp) | |
2675 | return ERR_PTR(-ENFILE); | |
2676 | ||
2677 | od.filp->f_flags = op->open_flag; | |
2678 | ||
2679 | error = path_init(dfd, pathname, flags | LOOKUP_PARENT, nd, &base); | |
2680 | if (unlikely(error)) | |
2681 | goto out_filp; | |
2682 | ||
2683 | current->total_link_count = 0; | |
2684 | error = link_path_walk(pathname, nd); | |
2685 | if (unlikely(error)) | |
2686 | goto out_filp; | |
2687 | ||
2688 | res = do_last(nd, &path, &od, op, &opened, pathname); | |
2689 | while (unlikely(!res)) { /* trailing symlink */ | |
2690 | struct path link = path; | |
2691 | void *cookie; | |
2692 | if (!(nd->flags & LOOKUP_FOLLOW)) { | |
2693 | path_put_conditional(&path, nd); | |
2694 | path_put(&nd->path); | |
2695 | res = ERR_PTR(-ELOOP); | |
2696 | break; | |
2697 | } | |
2698 | nd->flags |= LOOKUP_PARENT; | |
2699 | nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL); | |
2700 | error = follow_link(&link, nd, &cookie); | |
2701 | if (unlikely(error)) | |
2702 | goto out_filp; | |
2703 | res = do_last(nd, &path, &od, op, &opened, pathname); | |
2704 | put_link(nd, &link, cookie); | |
2705 | } | |
2706 | out: | |
2707 | if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) | |
2708 | path_put(&nd->root); | |
2709 | if (base) | |
2710 | fput(base); | |
2711 | if (!(opened & FILE_OPENED)) | |
2712 | put_filp(od.filp); | |
2713 | if (res == ERR_PTR(-EOPENSTALE)) { | |
2714 | if (flags & LOOKUP_RCU) | |
2715 | res = ERR_PTR(-ECHILD); | |
2716 | else | |
2717 | res = ERR_PTR(-ESTALE); | |
2718 | } | |
2719 | return res; | |
2720 | ||
2721 | out_filp: | |
2722 | res = ERR_PTR(error); | |
2723 | goto out; | |
2724 | } | |
2725 | ||
2726 | struct file *do_filp_open(int dfd, const char *pathname, | |
2727 | const struct open_flags *op, int flags) | |
2728 | { | |
2729 | struct nameidata nd; | |
2730 | struct file *filp; | |
2731 | ||
2732 | filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_RCU); | |
2733 | if (unlikely(filp == ERR_PTR(-ECHILD))) | |
2734 | filp = path_openat(dfd, pathname, &nd, op, flags); | |
2735 | if (unlikely(filp == ERR_PTR(-ESTALE))) | |
2736 | filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_REVAL); | |
2737 | return filp; | |
2738 | } | |
2739 | ||
2740 | struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt, | |
2741 | const char *name, const struct open_flags *op, int flags) | |
2742 | { | |
2743 | struct nameidata nd; | |
2744 | struct file *file; | |
2745 | ||
2746 | nd.root.mnt = mnt; | |
2747 | nd.root.dentry = dentry; | |
2748 | ||
2749 | flags |= LOOKUP_ROOT; | |
2750 | ||
2751 | if (dentry->d_inode->i_op->follow_link && op->intent & LOOKUP_OPEN) | |
2752 | return ERR_PTR(-ELOOP); | |
2753 | ||
2754 | file = path_openat(-1, name, &nd, op, flags | LOOKUP_RCU); | |
2755 | if (unlikely(file == ERR_PTR(-ECHILD))) | |
2756 | file = path_openat(-1, name, &nd, op, flags); | |
2757 | if (unlikely(file == ERR_PTR(-ESTALE))) | |
2758 | file = path_openat(-1, name, &nd, op, flags | LOOKUP_REVAL); | |
2759 | return file; | |
2760 | } | |
2761 | ||
2762 | struct dentry *kern_path_create(int dfd, const char *pathname, struct path *path, int is_dir) | |
2763 | { | |
2764 | struct dentry *dentry = ERR_PTR(-EEXIST); | |
2765 | struct nameidata nd; | |
2766 | int error = do_path_lookup(dfd, pathname, LOOKUP_PARENT, &nd); | |
2767 | if (error) | |
2768 | return ERR_PTR(error); | |
2769 | ||
2770 | /* | |
2771 | * Yucky last component or no last component at all? | |
2772 | * (foo/., foo/.., /////) | |
2773 | */ | |
2774 | if (nd.last_type != LAST_NORM) | |
2775 | goto out; | |
2776 | nd.flags &= ~LOOKUP_PARENT; | |
2777 | nd.flags |= LOOKUP_CREATE | LOOKUP_EXCL; | |
2778 | ||
2779 | /* | |
2780 | * Do the final lookup. | |
2781 | */ | |
2782 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); | |
2783 | dentry = lookup_hash(&nd); | |
2784 | if (IS_ERR(dentry)) | |
2785 | goto fail; | |
2786 | ||
2787 | if (dentry->d_inode) | |
2788 | goto eexist; | |
2789 | /* | |
2790 | * Special case - lookup gave negative, but... we had foo/bar/ | |
2791 | * From the vfs_mknod() POV we just have a negative dentry - | |
2792 | * all is fine. Let's be bastards - you had / on the end, you've | |
2793 | * been asking for (non-existent) directory. -ENOENT for you. | |
2794 | */ | |
2795 | if (unlikely(!is_dir && nd.last.name[nd.last.len])) { | |
2796 | dput(dentry); | |
2797 | dentry = ERR_PTR(-ENOENT); | |
2798 | goto fail; | |
2799 | } | |
2800 | *path = nd.path; | |
2801 | return dentry; | |
2802 | eexist: | |
2803 | dput(dentry); | |
2804 | dentry = ERR_PTR(-EEXIST); | |
2805 | fail: | |
2806 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); | |
2807 | out: | |
2808 | path_put(&nd.path); | |
2809 | return dentry; | |
2810 | } | |
2811 | EXPORT_SYMBOL(kern_path_create); | |
2812 | ||
2813 | struct dentry *user_path_create(int dfd, const char __user *pathname, struct path *path, int is_dir) | |
2814 | { | |
2815 | char *tmp = getname(pathname); | |
2816 | struct dentry *res; | |
2817 | if (IS_ERR(tmp)) | |
2818 | return ERR_CAST(tmp); | |
2819 | res = kern_path_create(dfd, tmp, path, is_dir); | |
2820 | putname(tmp); | |
2821 | return res; | |
2822 | } | |
2823 | EXPORT_SYMBOL(user_path_create); | |
2824 | ||
2825 | int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev) | |
2826 | { | |
2827 | int error = may_create(dir, dentry); | |
2828 | ||
2829 | if (error) | |
2830 | return error; | |
2831 | ||
2832 | if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD)) | |
2833 | return -EPERM; | |
2834 | ||
2835 | if (!dir->i_op->mknod) | |
2836 | return -EPERM; | |
2837 | ||
2838 | error = devcgroup_inode_mknod(mode, dev); | |
2839 | if (error) | |
2840 | return error; | |
2841 | ||
2842 | error = security_inode_mknod(dir, dentry, mode, dev); | |
2843 | if (error) | |
2844 | return error; | |
2845 | ||
2846 | error = dir->i_op->mknod(dir, dentry, mode, dev); | |
2847 | if (!error) | |
2848 | fsnotify_create(dir, dentry); | |
2849 | return error; | |
2850 | } | |
2851 | ||
2852 | static int may_mknod(umode_t mode) | |
2853 | { | |
2854 | switch (mode & S_IFMT) { | |
2855 | case S_IFREG: | |
2856 | case S_IFCHR: | |
2857 | case S_IFBLK: | |
2858 | case S_IFIFO: | |
2859 | case S_IFSOCK: | |
2860 | case 0: /* zero mode translates to S_IFREG */ | |
2861 | return 0; | |
2862 | case S_IFDIR: | |
2863 | return -EPERM; | |
2864 | default: | |
2865 | return -EINVAL; | |
2866 | } | |
2867 | } | |
2868 | ||
2869 | SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode, | |
2870 | unsigned, dev) | |
2871 | { | |
2872 | struct dentry *dentry; | |
2873 | struct path path; | |
2874 | int error; | |
2875 | ||
2876 | if (S_ISDIR(mode)) | |
2877 | return -EPERM; | |
2878 | ||
2879 | dentry = user_path_create(dfd, filename, &path, 0); | |
2880 | if (IS_ERR(dentry)) | |
2881 | return PTR_ERR(dentry); | |
2882 | ||
2883 | if (!IS_POSIXACL(path.dentry->d_inode)) | |
2884 | mode &= ~current_umask(); | |
2885 | error = may_mknod(mode); | |
2886 | if (error) | |
2887 | goto out_dput; | |
2888 | error = mnt_want_write(path.mnt); | |
2889 | if (error) | |
2890 | goto out_dput; | |
2891 | error = security_path_mknod(&path, dentry, mode, dev); | |
2892 | if (error) | |
2893 | goto out_drop_write; | |
2894 | switch (mode & S_IFMT) { | |
2895 | case 0: case S_IFREG: | |
2896 | error = vfs_create(path.dentry->d_inode,dentry,mode,NULL); | |
2897 | break; | |
2898 | case S_IFCHR: case S_IFBLK: | |
2899 | error = vfs_mknod(path.dentry->d_inode,dentry,mode, | |
2900 | new_decode_dev(dev)); | |
2901 | break; | |
2902 | case S_IFIFO: case S_IFSOCK: | |
2903 | error = vfs_mknod(path.dentry->d_inode,dentry,mode,0); | |
2904 | break; | |
2905 | } | |
2906 | out_drop_write: | |
2907 | mnt_drop_write(path.mnt); | |
2908 | out_dput: | |
2909 | dput(dentry); | |
2910 | mutex_unlock(&path.dentry->d_inode->i_mutex); | |
2911 | path_put(&path); | |
2912 | ||
2913 | return error; | |
2914 | } | |
2915 | ||
2916 | SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev) | |
2917 | { | |
2918 | return sys_mknodat(AT_FDCWD, filename, mode, dev); | |
2919 | } | |
2920 | ||
2921 | int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode) | |
2922 | { | |
2923 | int error = may_create(dir, dentry); | |
2924 | unsigned max_links = dir->i_sb->s_max_links; | |
2925 | ||
2926 | if (error) | |
2927 | return error; | |
2928 | ||
2929 | if (!dir->i_op->mkdir) | |
2930 | return -EPERM; | |
2931 | ||
2932 | mode &= (S_IRWXUGO|S_ISVTX); | |
2933 | error = security_inode_mkdir(dir, dentry, mode); | |
2934 | if (error) | |
2935 | return error; | |
2936 | ||
2937 | if (max_links && dir->i_nlink >= max_links) | |
2938 | return -EMLINK; | |
2939 | ||
2940 | error = dir->i_op->mkdir(dir, dentry, mode); | |
2941 | if (!error) | |
2942 | fsnotify_mkdir(dir, dentry); | |
2943 | return error; | |
2944 | } | |
2945 | ||
2946 | SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode) | |
2947 | { | |
2948 | struct dentry *dentry; | |
2949 | struct path path; | |
2950 | int error; | |
2951 | ||
2952 | dentry = user_path_create(dfd, pathname, &path, 1); | |
2953 | if (IS_ERR(dentry)) | |
2954 | return PTR_ERR(dentry); | |
2955 | ||
2956 | if (!IS_POSIXACL(path.dentry->d_inode)) | |
2957 | mode &= ~current_umask(); | |
2958 | error = mnt_want_write(path.mnt); | |
2959 | if (error) | |
2960 | goto out_dput; | |
2961 | error = security_path_mkdir(&path, dentry, mode); | |
2962 | if (error) | |
2963 | goto out_drop_write; | |
2964 | error = vfs_mkdir(path.dentry->d_inode, dentry, mode); | |
2965 | out_drop_write: | |
2966 | mnt_drop_write(path.mnt); | |
2967 | out_dput: | |
2968 | dput(dentry); | |
2969 | mutex_unlock(&path.dentry->d_inode->i_mutex); | |
2970 | path_put(&path); | |
2971 | return error; | |
2972 | } | |
2973 | ||
2974 | SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode) | |
2975 | { | |
2976 | return sys_mkdirat(AT_FDCWD, pathname, mode); | |
2977 | } | |
2978 | ||
2979 | /* | |
2980 | * The dentry_unhash() helper will try to drop the dentry early: we | |
2981 | * should have a usage count of 1 if we're the only user of this | |
2982 | * dentry, and if that is true (possibly after pruning the dcache), | |
2983 | * then we drop the dentry now. | |
2984 | * | |
2985 | * A low-level filesystem can, if it choses, legally | |
2986 | * do a | |
2987 | * | |
2988 | * if (!d_unhashed(dentry)) | |
2989 | * return -EBUSY; | |
2990 | * | |
2991 | * if it cannot handle the case of removing a directory | |
2992 | * that is still in use by something else.. | |
2993 | */ | |
2994 | void dentry_unhash(struct dentry *dentry) | |
2995 | { | |
2996 | shrink_dcache_parent(dentry); | |
2997 | spin_lock(&dentry->d_lock); | |
2998 | if (dentry->d_count == 1) | |
2999 | __d_drop(dentry); | |
3000 | spin_unlock(&dentry->d_lock); | |
3001 | } | |
3002 | ||
3003 | int vfs_rmdir(struct inode *dir, struct dentry *dentry) | |
3004 | { | |
3005 | int error = may_delete(dir, dentry, 1); | |
3006 | ||
3007 | if (error) | |
3008 | return error; | |
3009 | ||
3010 | if (!dir->i_op->rmdir) | |
3011 | return -EPERM; | |
3012 | ||
3013 | dget(dentry); | |
3014 | mutex_lock(&dentry->d_inode->i_mutex); | |
3015 | ||
3016 | error = -EBUSY; | |
3017 | if (d_mountpoint(dentry)) | |
3018 | goto out; | |
3019 | ||
3020 | error = security_inode_rmdir(dir, dentry); | |
3021 | if (error) | |
3022 | goto out; | |
3023 | ||
3024 | shrink_dcache_parent(dentry); | |
3025 | error = dir->i_op->rmdir(dir, dentry); | |
3026 | if (error) | |
3027 | goto out; | |
3028 | ||
3029 | dentry->d_inode->i_flags |= S_DEAD; | |
3030 | dont_mount(dentry); | |
3031 | ||
3032 | out: | |
3033 | mutex_unlock(&dentry->d_inode->i_mutex); | |
3034 | dput(dentry); | |
3035 | if (!error) | |
3036 | d_delete(dentry); | |
3037 | return error; | |
3038 | } | |
3039 | ||
3040 | static long do_rmdir(int dfd, const char __user *pathname) | |
3041 | { | |
3042 | int error = 0; | |
3043 | char * name; | |
3044 | struct dentry *dentry; | |
3045 | struct nameidata nd; | |
3046 | ||
3047 | error = user_path_parent(dfd, pathname, &nd, &name); | |
3048 | if (error) | |
3049 | return error; | |
3050 | ||
3051 | switch(nd.last_type) { | |
3052 | case LAST_DOTDOT: | |
3053 | error = -ENOTEMPTY; | |
3054 | goto exit1; | |
3055 | case LAST_DOT: | |
3056 | error = -EINVAL; | |
3057 | goto exit1; | |
3058 | case LAST_ROOT: | |
3059 | error = -EBUSY; | |
3060 | goto exit1; | |
3061 | } | |
3062 | ||
3063 | nd.flags &= ~LOOKUP_PARENT; | |
3064 | ||
3065 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); | |
3066 | dentry = lookup_hash(&nd); | |
3067 | error = PTR_ERR(dentry); | |
3068 | if (IS_ERR(dentry)) | |
3069 | goto exit2; | |
3070 | if (!dentry->d_inode) { | |
3071 | error = -ENOENT; | |
3072 | goto exit3; | |
3073 | } | |
3074 | error = mnt_want_write(nd.path.mnt); | |
3075 | if (error) | |
3076 | goto exit3; | |
3077 | error = security_path_rmdir(&nd.path, dentry); | |
3078 | if (error) | |
3079 | goto exit4; | |
3080 | error = vfs_rmdir(nd.path.dentry->d_inode, dentry); | |
3081 | exit4: | |
3082 | mnt_drop_write(nd.path.mnt); | |
3083 | exit3: | |
3084 | dput(dentry); | |
3085 | exit2: | |
3086 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); | |
3087 | exit1: | |
3088 | path_put(&nd.path); | |
3089 | putname(name); | |
3090 | return error; | |
3091 | } | |
3092 | ||
3093 | SYSCALL_DEFINE1(rmdir, const char __user *, pathname) | |
3094 | { | |
3095 | return do_rmdir(AT_FDCWD, pathname); | |
3096 | } | |
3097 | ||
3098 | int vfs_unlink(struct inode *dir, struct dentry *dentry) | |
3099 | { | |
3100 | int error = may_delete(dir, dentry, 0); | |
3101 | ||
3102 | if (error) | |
3103 | return error; | |
3104 | ||
3105 | if (!dir->i_op->unlink) | |
3106 | return -EPERM; | |
3107 | ||
3108 | mutex_lock(&dentry->d_inode->i_mutex); | |
3109 | if (d_mountpoint(dentry)) | |
3110 | error = -EBUSY; | |
3111 | else { | |
3112 | error = security_inode_unlink(dir, dentry); | |
3113 | if (!error) { | |
3114 | error = dir->i_op->unlink(dir, dentry); | |
3115 | if (!error) | |
3116 | dont_mount(dentry); | |
3117 | } | |
3118 | } | |
3119 | mutex_unlock(&dentry->d_inode->i_mutex); | |
3120 | ||
3121 | /* We don't d_delete() NFS sillyrenamed files--they still exist. */ | |
3122 | if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) { | |
3123 | fsnotify_link_count(dentry->d_inode); | |
3124 | d_delete(dentry); | |
3125 | } | |
3126 | ||
3127 | return error; | |
3128 | } | |
3129 | ||
3130 | /* | |
3131 | * Make sure that the actual truncation of the file will occur outside its | |
3132 | * directory's i_mutex. Truncate can take a long time if there is a lot of | |
3133 | * writeout happening, and we don't want to prevent access to the directory | |
3134 | * while waiting on the I/O. | |
3135 | */ | |
3136 | static long do_unlinkat(int dfd, const char __user *pathname) | |
3137 | { | |
3138 | int error; | |
3139 | char *name; | |
3140 | struct dentry *dentry; | |
3141 | struct nameidata nd; | |
3142 | struct inode *inode = NULL; | |
3143 | ||
3144 | error = user_path_parent(dfd, pathname, &nd, &name); | |
3145 | if (error) | |
3146 | return error; | |
3147 | ||
3148 | error = -EISDIR; | |
3149 | if (nd.last_type != LAST_NORM) | |
3150 | goto exit1; | |
3151 | ||
3152 | nd.flags &= ~LOOKUP_PARENT; | |
3153 | ||
3154 | mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT); | |
3155 | dentry = lookup_hash(&nd); | |
3156 | error = PTR_ERR(dentry); | |
3157 | if (!IS_ERR(dentry)) { | |
3158 | /* Why not before? Because we want correct error value */ | |
3159 | if (nd.last.name[nd.last.len]) | |
3160 | goto slashes; | |
3161 | inode = dentry->d_inode; | |
3162 | if (!inode) | |
3163 | goto slashes; | |
3164 | ihold(inode); | |
3165 | error = mnt_want_write(nd.path.mnt); | |
3166 | if (error) | |
3167 | goto exit2; | |
3168 | error = security_path_unlink(&nd.path, dentry); | |
3169 | if (error) | |
3170 | goto exit3; | |
3171 | error = vfs_unlink(nd.path.dentry->d_inode, dentry); | |
3172 | exit3: | |
3173 | mnt_drop_write(nd.path.mnt); | |
3174 | exit2: | |
3175 | dput(dentry); | |
3176 | } | |
3177 | mutex_unlock(&nd.path.dentry->d_inode->i_mutex); | |
3178 | if (inode) | |
3179 | iput(inode); /* truncate the inode here */ | |
3180 | exit1: | |
3181 | path_put(&nd.path); | |
3182 | putname(name); | |
3183 | return error; | |
3184 | ||
3185 | slashes: | |
3186 | error = !dentry->d_inode ? -ENOENT : | |
3187 | S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR; | |
3188 | goto exit2; | |
3189 | } | |
3190 | ||
3191 | SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag) | |
3192 | { | |
3193 | if ((flag & ~AT_REMOVEDIR) != 0) | |
3194 | return -EINVAL; | |
3195 | ||
3196 | if (flag & AT_REMOVEDIR) | |
3197 | return do_rmdir(dfd, pathname); | |
3198 | ||
3199 | return do_unlinkat(dfd, pathname); | |
3200 | } | |
3201 | ||
3202 | SYSCALL_DEFINE1(unlink, const char __user *, pathname) | |
3203 | { | |
3204 | return do_unlinkat(AT_FDCWD, pathname); | |
3205 | } | |
3206 | ||
3207 | int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname) | |
3208 | { | |
3209 | int error = may_create(dir, dentry); | |
3210 | ||
3211 | if (error) | |
3212 | return error; | |
3213 | ||
3214 | if (!dir->i_op->symlink) | |
3215 | return -EPERM; | |
3216 | ||
3217 | error = security_inode_symlink(dir, dentry, oldname); | |
3218 | if (error) | |
3219 | return error; | |
3220 | ||
3221 | error = dir->i_op->symlink(dir, dentry, oldname); | |
3222 | if (!error) | |
3223 | fsnotify_create(dir, dentry); | |
3224 | return error; | |
3225 | } | |
3226 | ||
3227 | SYSCALL_DEFINE3(symlinkat, const char __user *, oldname, | |
3228 | int, newdfd, const char __user *, newname) | |
3229 | { | |
3230 | int error; | |
3231 | char *from; | |
3232 | struct dentry *dentry; | |
3233 | struct path path; | |
3234 | ||
3235 | from = getname(oldname); | |
3236 | if (IS_ERR(from)) | |
3237 | return PTR_ERR(from); | |
3238 | ||
3239 | dentry = user_path_create(newdfd, newname, &path, 0); | |
3240 | error = PTR_ERR(dentry); | |
3241 | if (IS_ERR(dentry)) | |
3242 | goto out_putname; | |
3243 | ||
3244 | error = mnt_want_write(path.mnt); | |
3245 | if (error) | |
3246 | goto out_dput; | |
3247 | error = security_path_symlink(&path, dentry, from); | |
3248 | if (error) | |
3249 | goto out_drop_write; | |
3250 | error = vfs_symlink(path.dentry->d_inode, dentry, from); | |
3251 | out_drop_write: | |
3252 | mnt_drop_write(path.mnt); | |
3253 | out_dput: | |
3254 | dput(dentry); | |
3255 | mutex_unlock(&path.dentry->d_inode->i_mutex); | |
3256 | path_put(&path); | |
3257 | out_putname: | |
3258 | putname(from); | |
3259 | return error; | |
3260 | } | |
3261 | ||
3262 | SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname) | |
3263 | { | |
3264 | return sys_symlinkat(oldname, AT_FDCWD, newname); | |
3265 | } | |
3266 | ||
3267 | int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry) | |
3268 | { | |
3269 | struct inode *inode = old_dentry->d_inode; | |
3270 | unsigned max_links = dir->i_sb->s_max_links; | |
3271 | int error; | |
3272 | ||
3273 | if (!inode) | |
3274 | return -ENOENT; | |
3275 | ||
3276 | error = may_create(dir, new_dentry); | |
3277 | if (error) | |
3278 | return error; | |
3279 | ||
3280 | if (dir->i_sb != inode->i_sb) | |
3281 | return -EXDEV; | |
3282 | ||
3283 | /* | |
3284 | * A link to an append-only or immutable file cannot be created. | |
3285 | */ | |
3286 | if (IS_APPEND(inode) || IS_IMMUTABLE(inode)) | |
3287 | return -EPERM; | |
3288 | if (!dir->i_op->link) | |
3289 | return -EPERM; | |
3290 | if (S_ISDIR(inode->i_mode)) | |
3291 | return -EPERM; | |
3292 | ||
3293 | error = security_inode_link(old_dentry, dir, new_dentry); | |
3294 | if (error) | |
3295 | return error; | |
3296 | ||
3297 | mutex_lock(&inode->i_mutex); | |
3298 | /* Make sure we don't allow creating hardlink to an unlinked file */ | |
3299 | if (inode->i_nlink == 0) | |
3300 | error = -ENOENT; | |
3301 | else if (max_links && inode->i_nlink >= max_links) | |
3302 | error = -EMLINK; | |
3303 | else | |
3304 | error = dir->i_op->link(old_dentry, dir, new_dentry); | |
3305 | mutex_unlock(&inode->i_mutex); | |
3306 | if (!error) | |
3307 | fsnotify_link(dir, inode, new_dentry); | |
3308 | return error; | |
3309 | } | |
3310 | ||
3311 | /* | |
3312 | * Hardlinks are often used in delicate situations. We avoid | |
3313 | * security-related surprises by not following symlinks on the | |
3314 | * newname. --KAB | |
3315 | * | |
3316 | * We don't follow them on the oldname either to be compatible | |
3317 | * with linux 2.0, and to avoid hard-linking to directories | |
3318 | * and other special files. --ADM | |
3319 | */ | |
3320 | SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname, | |
3321 | int, newdfd, const char __user *, newname, int, flags) | |
3322 | { | |
3323 | struct dentry *new_dentry; | |
3324 | struct path old_path, new_path; | |
3325 | int how = 0; | |
3326 | int error; | |
3327 | ||
3328 | if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0) | |
3329 | return -EINVAL; | |
3330 | /* | |
3331 | * To use null names we require CAP_DAC_READ_SEARCH | |
3332 | * This ensures that not everyone will be able to create | |
3333 | * handlink using the passed filedescriptor. | |
3334 | */ | |
3335 | if (flags & AT_EMPTY_PATH) { | |
3336 | if (!capable(CAP_DAC_READ_SEARCH)) | |
3337 | return -ENOENT; | |
3338 | how = LOOKUP_EMPTY; | |
3339 | } | |
3340 | ||
3341 | if (flags & AT_SYMLINK_FOLLOW) | |
3342 | how |= LOOKUP_FOLLOW; | |
3343 | ||
3344 | error = user_path_at(olddfd, oldname, how, &old_path); | |
3345 | if (error) | |
3346 | return error; | |
3347 | ||
3348 | new_dentry = user_path_create(newdfd, newname, &new_path, 0); | |
3349 | error = PTR_ERR(new_dentry); | |
3350 | if (IS_ERR(new_dentry)) | |
3351 | goto out; | |
3352 | ||
3353 | error = -EXDEV; | |
3354 | if (old_path.mnt != new_path.mnt) | |
3355 | goto out_dput; | |
3356 | error = mnt_want_write(new_path.mnt); | |
3357 | if (error) | |
3358 | goto out_dput; | |
3359 | error = security_path_link(old_path.dentry, &new_path, new_dentry); | |
3360 | if (error) | |
3361 | goto out_drop_write; | |
3362 | error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry); | |
3363 | out_drop_write: | |
3364 | mnt_drop_write(new_path.mnt); | |
3365 | out_dput: | |
3366 | dput(new_dentry); | |
3367 | mutex_unlock(&new_path.dentry->d_inode->i_mutex); | |
3368 | path_put(&new_path); | |
3369 | out: | |
3370 | path_put(&old_path); | |
3371 | ||
3372 | return error; | |
3373 | } | |
3374 | ||
3375 | SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname) | |
3376 | { | |
3377 | return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0); | |
3378 | } | |
3379 | ||
3380 | /* | |
3381 | * The worst of all namespace operations - renaming directory. "Perverted" | |
3382 | * doesn't even start to describe it. Somebody in UCB had a heck of a trip... | |
3383 | * Problems: | |
3384 | * a) we can get into loop creation. Check is done in is_subdir(). | |
3385 | * b) race potential - two innocent renames can create a loop together. | |
3386 | * That's where 4.4 screws up. Current fix: serialization on | |
3387 | * sb->s_vfs_rename_mutex. We might be more accurate, but that's another | |
3388 | * story. | |
3389 | * c) we have to lock _three_ objects - parents and victim (if it exists). | |
3390 | * And that - after we got ->i_mutex on parents (until then we don't know | |
3391 | * whether the target exists). Solution: try to be smart with locking | |
3392 | * order for inodes. We rely on the fact that tree topology may change | |
3393 | * only under ->s_vfs_rename_mutex _and_ that parent of the object we | |
3394 | * move will be locked. Thus we can rank directories by the tree | |
3395 | * (ancestors first) and rank all non-directories after them. | |
3396 | * That works since everybody except rename does "lock parent, lookup, | |
3397 | * lock child" and rename is under ->s_vfs_rename_mutex. | |
3398 | * HOWEVER, it relies on the assumption that any object with ->lookup() | |
3399 | * has no more than 1 dentry. If "hybrid" objects will ever appear, | |
3400 | * we'd better make sure that there's no link(2) for them. | |
3401 | * d) conversion from fhandle to dentry may come in the wrong moment - when | |
3402 | * we are removing the target. Solution: we will have to grab ->i_mutex | |
3403 | * in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on | |
3404 | * ->i_mutex on parents, which works but leads to some truly excessive | |
3405 | * locking]. | |
3406 | */ | |
3407 | static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry, | |
3408 | struct inode *new_dir, struct dentry *new_dentry) | |
3409 | { | |
3410 | int error = 0; | |
3411 | struct inode *target = new_dentry->d_inode; | |
3412 | unsigned max_links = new_dir->i_sb->s_max_links; | |
3413 | ||
3414 | /* | |
3415 | * If we are going to change the parent - check write permissions, | |
3416 | * we'll need to flip '..'. | |
3417 | */ | |
3418 | if (new_dir != old_dir) { | |
3419 | error = inode_permission(old_dentry->d_inode, MAY_WRITE); | |
3420 | if (error) | |
3421 | return error; | |
3422 | } | |
3423 | ||
3424 | error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry); | |
3425 | if (error) | |
3426 | return error; | |
3427 | ||
3428 | dget(new_dentry); | |
3429 | if (target) | |
3430 | mutex_lock(&target->i_mutex); | |
3431 | ||
3432 | error = -EBUSY; | |
3433 | if (d_mountpoint(old_dentry) || d_mountpoint(new_dentry)) | |
3434 | goto out; | |
3435 | ||
3436 | error = -EMLINK; | |
3437 | if (max_links && !target && new_dir != old_dir && | |
3438 | new_dir->i_nlink >= max_links) | |
3439 | goto out; | |
3440 | ||
3441 | if (target) | |
3442 | shrink_dcache_parent(new_dentry); | |
3443 | error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry); | |
3444 | if (error) | |
3445 | goto out; | |
3446 | ||
3447 | if (target) { | |
3448 | target->i_flags |= S_DEAD; | |
3449 | dont_mount(new_dentry); | |
3450 | } | |
3451 | out: | |
3452 | if (target) | |
3453 | mutex_unlock(&target->i_mutex); | |
3454 | dput(new_dentry); | |
3455 | if (!error) | |
3456 | if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) | |
3457 | d_move(old_dentry,new_dentry); | |
3458 | return error; | |
3459 | } | |
3460 | ||
3461 | static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry, | |
3462 | struct inode *new_dir, struct dentry *new_dentry) | |
3463 | { | |
3464 | struct inode *target = new_dentry->d_inode; | |
3465 | int error; | |
3466 | ||
3467 | error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry); | |
3468 | if (error) | |
3469 | return error; | |
3470 | ||
3471 | dget(new_dentry); | |
3472 | if (target) | |
3473 | mutex_lock(&target->i_mutex); | |
3474 | ||
3475 | error = -EBUSY; | |
3476 | if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry)) | |
3477 | goto out; | |
3478 | ||
3479 | error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry); | |
3480 | if (error) | |
3481 | goto out; | |
3482 | ||
3483 | if (target) | |
3484 | dont_mount(new_dentry); | |
3485 | if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) | |
3486 | d_move(old_dentry, new_dentry); | |
3487 | out: | |
3488 | if (target) | |
3489 | mutex_unlock(&target->i_mutex); | |
3490 | dput(new_dentry); | |
3491 | return error; | |
3492 | } | |
3493 | ||
3494 | int vfs_rename(struct inode *old_dir, struct dentry *old_dentry, | |
3495 | struct inode *new_dir, struct dentry *new_dentry) | |
3496 | { | |
3497 | int error; | |
3498 | int is_dir = S_ISDIR(old_dentry->d_inode->i_mode); | |
3499 | const unsigned char *old_name; | |
3500 | ||
3501 | if (old_dentry->d_inode == new_dentry->d_inode) | |
3502 | return 0; | |
3503 | ||
3504 | error = may_delete(old_dir, old_dentry, is_dir); | |
3505 | if (error) | |
3506 | return error; | |
3507 | ||
3508 | if (!new_dentry->d_inode) | |
3509 | error = may_create(new_dir, new_dentry); | |
3510 | else | |
3511 | error = may_delete(new_dir, new_dentry, is_dir); | |
3512 | if (error) | |
3513 | return error; | |
3514 | ||
3515 | if (!old_dir->i_op->rename) | |
3516 | return -EPERM; | |
3517 | ||
3518 | old_name = fsnotify_oldname_init(old_dentry->d_name.name); | |
3519 | ||
3520 | if (is_dir) | |
3521 | error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry); | |
3522 | else | |
3523 | error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry); | |
3524 | if (!error) | |
3525 | fsnotify_move(old_dir, new_dir, old_name, is_dir, | |
3526 | new_dentry->d_inode, old_dentry); | |
3527 | fsnotify_oldname_free(old_name); | |
3528 | ||
3529 | return error; | |
3530 | } | |
3531 | ||
3532 | SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname, | |
3533 | int, newdfd, const char __user *, newname) | |
3534 | { | |
3535 | struct dentry *old_dir, *new_dir; | |
3536 | struct dentry *old_dentry, *new_dentry; | |
3537 | struct dentry *trap; | |
3538 | struct nameidata oldnd, newnd; | |
3539 | char *from; | |
3540 | char *to; | |
3541 | int error; | |
3542 | ||
3543 | error = user_path_parent(olddfd, oldname, &oldnd, &from); | |
3544 | if (error) | |
3545 | goto exit; | |
3546 | ||
3547 | error = user_path_parent(newdfd, newname, &newnd, &to); | |
3548 | if (error) | |
3549 | goto exit1; | |
3550 | ||
3551 | error = -EXDEV; | |
3552 | if (oldnd.path.mnt != newnd.path.mnt) | |
3553 | goto exit2; | |
3554 | ||
3555 | old_dir = oldnd.path.dentry; | |
3556 | error = -EBUSY; | |
3557 | if (oldnd.last_type != LAST_NORM) | |
3558 | goto exit2; | |
3559 | ||
3560 | new_dir = newnd.path.dentry; | |
3561 | if (newnd.last_type != LAST_NORM) | |
3562 | goto exit2; | |
3563 | ||
3564 | oldnd.flags &= ~LOOKUP_PARENT; | |
3565 | newnd.flags &= ~LOOKUP_PARENT; | |
3566 | newnd.flags |= LOOKUP_RENAME_TARGET; | |
3567 | ||
3568 | trap = lock_rename(new_dir, old_dir); | |
3569 | ||
3570 | old_dentry = lookup_hash(&oldnd); | |
3571 | error = PTR_ERR(old_dentry); | |
3572 | if (IS_ERR(old_dentry)) | |
3573 | goto exit3; | |
3574 | /* source must exist */ | |
3575 | error = -ENOENT; | |
3576 | if (!old_dentry->d_inode) | |
3577 | goto exit4; | |
3578 | /* unless the source is a directory trailing slashes give -ENOTDIR */ | |
3579 | if (!S_ISDIR(old_dentry->d_inode->i_mode)) { | |
3580 | error = -ENOTDIR; | |
3581 | if (oldnd.last.name[oldnd.last.len]) | |
3582 | goto exit4; | |
3583 | if (newnd.last.name[newnd.last.len]) | |
3584 | goto exit4; | |
3585 | } | |
3586 | /* source should not be ancestor of target */ | |
3587 | error = -EINVAL; | |
3588 | if (old_dentry == trap) | |
3589 | goto exit4; | |
3590 | new_dentry = lookup_hash(&newnd); | |
3591 | error = PTR_ERR(new_dentry); | |
3592 | if (IS_ERR(new_dentry)) | |
3593 | goto exit4; | |
3594 | /* target should not be an ancestor of source */ | |
3595 | error = -ENOTEMPTY; | |
3596 | if (new_dentry == trap) | |
3597 | goto exit5; | |
3598 | ||
3599 | error = mnt_want_write(oldnd.path.mnt); | |
3600 | if (error) | |
3601 | goto exit5; | |
3602 | error = security_path_rename(&oldnd.path, old_dentry, | |
3603 | &newnd.path, new_dentry); | |
3604 | if (error) | |
3605 | goto exit6; | |
3606 | error = vfs_rename(old_dir->d_inode, old_dentry, | |
3607 | new_dir->d_inode, new_dentry); | |
3608 | exit6: | |
3609 | mnt_drop_write(oldnd.path.mnt); | |
3610 | exit5: | |
3611 | dput(new_dentry); | |
3612 | exit4: | |
3613 | dput(old_dentry); | |
3614 | exit3: | |
3615 | unlock_rename(new_dir, old_dir); | |
3616 | exit2: | |
3617 | path_put(&newnd.path); | |
3618 | putname(to); | |
3619 | exit1: | |
3620 | path_put(&oldnd.path); | |
3621 | putname(from); | |
3622 | exit: | |
3623 | return error; | |
3624 | } | |
3625 | ||
3626 | SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname) | |
3627 | { | |
3628 | return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname); | |
3629 | } | |
3630 | ||
3631 | int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link) | |
3632 | { | |
3633 | int len; | |
3634 | ||
3635 | len = PTR_ERR(link); | |
3636 | if (IS_ERR(link)) | |
3637 | goto out; | |
3638 | ||
3639 | len = strlen(link); | |
3640 | if (len > (unsigned) buflen) | |
3641 | len = buflen; | |
3642 | if (copy_to_user(buffer, link, len)) | |
3643 | len = -EFAULT; | |
3644 | out: | |
3645 | return len; | |
3646 | } | |
3647 | ||
3648 | /* | |
3649 | * A helper for ->readlink(). This should be used *ONLY* for symlinks that | |
3650 | * have ->follow_link() touching nd only in nd_set_link(). Using (or not | |
3651 | * using) it for any given inode is up to filesystem. | |
3652 | */ | |
3653 | int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen) | |
3654 | { | |
3655 | struct nameidata nd; | |
3656 | void *cookie; | |
3657 | int res; | |
3658 | ||
3659 | nd.depth = 0; | |
3660 | cookie = dentry->d_inode->i_op->follow_link(dentry, &nd); | |
3661 | if (IS_ERR(cookie)) | |
3662 | return PTR_ERR(cookie); | |
3663 | ||
3664 | res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd)); | |
3665 | if (dentry->d_inode->i_op->put_link) | |
3666 | dentry->d_inode->i_op->put_link(dentry, &nd, cookie); | |
3667 | return res; | |
3668 | } | |
3669 | ||
3670 | int vfs_follow_link(struct nameidata *nd, const char *link) | |
3671 | { | |
3672 | return __vfs_follow_link(nd, link); | |
3673 | } | |
3674 | ||
3675 | /* get the link contents into pagecache */ | |
3676 | static char *page_getlink(struct dentry * dentry, struct page **ppage) | |
3677 | { | |
3678 | char *kaddr; | |
3679 | struct page *page; | |
3680 | struct address_space *mapping = dentry->d_inode->i_mapping; | |
3681 | page = read_mapping_page(mapping, 0, NULL); | |
3682 | if (IS_ERR(page)) | |
3683 | return (char*)page; | |
3684 | *ppage = page; | |
3685 | kaddr = kmap(page); | |
3686 | nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1); | |
3687 | return kaddr; | |
3688 | } | |
3689 | ||
3690 | int page_readlink(struct dentry *dentry, char __user *buffer, int buflen) | |
3691 | { | |
3692 | struct page *page = NULL; | |
3693 | char *s = page_getlink(dentry, &page); | |
3694 | int res = vfs_readlink(dentry,buffer,buflen,s); | |
3695 | if (page) { | |
3696 | kunmap(page); | |
3697 | page_cache_release(page); | |
3698 | } | |
3699 | return res; | |
3700 | } | |
3701 | ||
3702 | void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd) | |
3703 | { | |
3704 | struct page *page = NULL; | |
3705 | nd_set_link(nd, page_getlink(dentry, &page)); | |
3706 | return page; | |
3707 | } | |
3708 | ||
3709 | void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie) | |
3710 | { | |
3711 | struct page *page = cookie; | |
3712 | ||
3713 | if (page) { | |
3714 | kunmap(page); | |
3715 | page_cache_release(page); | |
3716 | } | |
3717 | } | |
3718 | ||
3719 | /* | |
3720 | * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS | |
3721 | */ | |
3722 | int __page_symlink(struct inode *inode, const char *symname, int len, int nofs) | |
3723 | { | |
3724 | struct address_space *mapping = inode->i_mapping; | |
3725 | struct page *page; | |
3726 | void *fsdata; | |
3727 | int err; | |
3728 | char *kaddr; | |
3729 | unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE; | |
3730 | if (nofs) | |
3731 | flags |= AOP_FLAG_NOFS; | |
3732 | ||
3733 | retry: | |
3734 | err = pagecache_write_begin(NULL, mapping, 0, len-1, | |
3735 | flags, &page, &fsdata); | |
3736 | if (err) | |
3737 | goto fail; | |
3738 | ||
3739 | kaddr = kmap_atomic(page); | |
3740 | memcpy(kaddr, symname, len-1); | |
3741 | kunmap_atomic(kaddr); | |
3742 | ||
3743 | err = pagecache_write_end(NULL, mapping, 0, len-1, len-1, | |
3744 | page, fsdata); | |
3745 | if (err < 0) | |
3746 | goto fail; | |
3747 | if (err < len-1) | |
3748 | goto retry; | |
3749 | ||
3750 | mark_inode_dirty(inode); | |
3751 | return 0; | |
3752 | fail: | |
3753 | return err; | |
3754 | } | |
3755 | ||
3756 | int page_symlink(struct inode *inode, const char *symname, int len) | |
3757 | { | |
3758 | return __page_symlink(inode, symname, len, | |
3759 | !(mapping_gfp_mask(inode->i_mapping) & __GFP_FS)); | |
3760 | } | |
3761 | ||
3762 | const struct inode_operations page_symlink_inode_operations = { | |
3763 | .readlink = generic_readlink, | |
3764 | .follow_link = page_follow_link_light, | |
3765 | .put_link = page_put_link, | |
3766 | }; | |
3767 | ||
3768 | EXPORT_SYMBOL(user_path_at); | |
3769 | EXPORT_SYMBOL(follow_down_one); | |
3770 | EXPORT_SYMBOL(follow_down); | |
3771 | EXPORT_SYMBOL(follow_up); | |
3772 | EXPORT_SYMBOL(get_write_access); /* binfmt_aout */ | |
3773 | EXPORT_SYMBOL(getname); | |
3774 | EXPORT_SYMBOL(lock_rename); | |
3775 | EXPORT_SYMBOL(lookup_one_len); | |
3776 | EXPORT_SYMBOL(page_follow_link_light); | |
3777 | EXPORT_SYMBOL(page_put_link); | |
3778 | EXPORT_SYMBOL(page_readlink); | |
3779 | EXPORT_SYMBOL(__page_symlink); | |
3780 | EXPORT_SYMBOL(page_symlink); | |
3781 | EXPORT_SYMBOL(page_symlink_inode_operations); | |
3782 | EXPORT_SYMBOL(kern_path); | |
3783 | EXPORT_SYMBOL(vfs_path_lookup); | |
3784 | EXPORT_SYMBOL(inode_permission); | |
3785 | EXPORT_SYMBOL(unlock_rename); | |
3786 | EXPORT_SYMBOL(vfs_create); | |
3787 | EXPORT_SYMBOL(vfs_follow_link); | |
3788 | EXPORT_SYMBOL(vfs_link); | |
3789 | EXPORT_SYMBOL(vfs_mkdir); | |
3790 | EXPORT_SYMBOL(vfs_mknod); | |
3791 | EXPORT_SYMBOL(generic_permission); | |
3792 | EXPORT_SYMBOL(vfs_readlink); | |
3793 | EXPORT_SYMBOL(vfs_rename); | |
3794 | EXPORT_SYMBOL(vfs_rmdir); | |
3795 | EXPORT_SYMBOL(vfs_symlink); | |
3796 | EXPORT_SYMBOL(vfs_unlink); | |
3797 | EXPORT_SYMBOL(dentry_unhash); | |
3798 | EXPORT_SYMBOL(generic_readlink); |