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Commit | Line | Data |
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1 | /* | |
2 | File: fs/xattr.c | |
3 | ||
4 | Extended attribute handling. | |
5 | ||
6 | Copyright (C) 2001 by Andreas Gruenbacher <a.gruenbacher@computer.org> | |
7 | Copyright (C) 2001 SGI - Silicon Graphics, Inc <linux-xfs@oss.sgi.com> | |
8 | Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com> | |
9 | */ | |
10 | #include <linux/fs.h> | |
11 | #include <linux/slab.h> | |
12 | #include <linux/file.h> | |
13 | #include <linux/xattr.h> | |
14 | #include <linux/namei.h> | |
15 | #include <linux/security.h> | |
16 | #include <linux/syscalls.h> | |
17 | #include <linux/module.h> | |
18 | #include <linux/fsnotify.h> | |
19 | #include <linux/audit.h> | |
20 | #include <asm/uaccess.h> | |
21 | ||
22 | ||
23 | /* | |
24 | * Check permissions for extended attribute access. This is a bit complicated | |
25 | * because different namespaces have very different rules. | |
26 | */ | |
27 | static int | |
28 | xattr_permission(struct inode *inode, const char *name, int mask) | |
29 | { | |
30 | /* | |
31 | * We can never set or remove an extended attribute on a read-only | |
32 | * filesystem or on an immutable / append-only inode. | |
33 | */ | |
34 | if (mask & MAY_WRITE) { | |
35 | if (IS_RDONLY(inode)) | |
36 | return -EROFS; | |
37 | if (IS_IMMUTABLE(inode) || IS_APPEND(inode)) | |
38 | return -EPERM; | |
39 | } | |
40 | ||
41 | /* | |
42 | * No restriction for security.* and system.* from the VFS. Decision | |
43 | * on these is left to the underlying filesystem / security module. | |
44 | */ | |
45 | if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) || | |
46 | !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN)) | |
47 | return 0; | |
48 | ||
49 | /* | |
50 | * The trusted.* namespace can only be accessed by a privileged user. | |
51 | */ | |
52 | if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) | |
53 | return (capable(CAP_SYS_ADMIN) ? 0 : -EPERM); | |
54 | ||
55 | /* In user.* namespace, only regular files and directories can have | |
56 | * extended attributes. For sticky directories, only the owner and | |
57 | * privileged user can write attributes. | |
58 | */ | |
59 | if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) { | |
60 | if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode)) | |
61 | return -EPERM; | |
62 | if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) && | |
63 | (mask & MAY_WRITE) && !is_owner_or_cap(inode)) | |
64 | return -EPERM; | |
65 | } | |
66 | ||
67 | return permission(inode, mask, NULL); | |
68 | } | |
69 | ||
70 | int | |
71 | vfs_setxattr(struct dentry *dentry, char *name, void *value, | |
72 | size_t size, int flags) | |
73 | { | |
74 | struct inode *inode = dentry->d_inode; | |
75 | int error; | |
76 | ||
77 | error = xattr_permission(inode, name, MAY_WRITE); | |
78 | if (error) | |
79 | return error; | |
80 | ||
81 | mutex_lock(&inode->i_mutex); | |
82 | error = security_inode_setxattr(dentry, name, value, size, flags); | |
83 | if (error) | |
84 | goto out; | |
85 | error = -EOPNOTSUPP; | |
86 | if (inode->i_op->setxattr) { | |
87 | error = inode->i_op->setxattr(dentry, name, value, size, flags); | |
88 | if (!error) { | |
89 | fsnotify_xattr(dentry); | |
90 | security_inode_post_setxattr(dentry, name, value, | |
91 | size, flags); | |
92 | } | |
93 | } else if (!strncmp(name, XATTR_SECURITY_PREFIX, | |
94 | XATTR_SECURITY_PREFIX_LEN)) { | |
95 | const char *suffix = name + XATTR_SECURITY_PREFIX_LEN; | |
96 | error = security_inode_setsecurity(inode, suffix, value, | |
97 | size, flags); | |
98 | if (!error) | |
99 | fsnotify_xattr(dentry); | |
100 | } | |
101 | out: | |
102 | mutex_unlock(&inode->i_mutex); | |
103 | return error; | |
104 | } | |
105 | EXPORT_SYMBOL_GPL(vfs_setxattr); | |
106 | ||
107 | ssize_t | |
108 | vfs_getxattr(struct dentry *dentry, char *name, void *value, size_t size) | |
109 | { | |
110 | struct inode *inode = dentry->d_inode; | |
111 | int error; | |
112 | ||
113 | error = xattr_permission(inode, name, MAY_READ); | |
114 | if (error) | |
115 | return error; | |
116 | ||
117 | error = security_inode_getxattr(dentry, name); | |
118 | if (error) | |
119 | return error; | |
120 | ||
121 | if (inode->i_op->getxattr) | |
122 | error = inode->i_op->getxattr(dentry, name, value, size); | |
123 | else | |
124 | error = -EOPNOTSUPP; | |
125 | ||
126 | if (!strncmp(name, XATTR_SECURITY_PREFIX, | |
127 | XATTR_SECURITY_PREFIX_LEN)) { | |
128 | const char *suffix = name + XATTR_SECURITY_PREFIX_LEN; | |
129 | int ret = security_inode_getsecurity(inode, suffix, value, | |
130 | size, error); | |
131 | /* | |
132 | * Only overwrite the return value if a security module | |
133 | * is actually active. | |
134 | */ | |
135 | if (ret != -EOPNOTSUPP) | |
136 | error = ret; | |
137 | } | |
138 | ||
139 | return error; | |
140 | } | |
141 | EXPORT_SYMBOL_GPL(vfs_getxattr); | |
142 | ||
143 | ssize_t | |
144 | vfs_listxattr(struct dentry *d, char *list, size_t size) | |
145 | { | |
146 | ssize_t error; | |
147 | ||
148 | error = security_inode_listxattr(d); | |
149 | if (error) | |
150 | return error; | |
151 | error = -EOPNOTSUPP; | |
152 | if (d->d_inode->i_op && d->d_inode->i_op->listxattr) { | |
153 | error = d->d_inode->i_op->listxattr(d, list, size); | |
154 | } else { | |
155 | error = security_inode_listsecurity(d->d_inode, list, size); | |
156 | if (size && error > size) | |
157 | error = -ERANGE; | |
158 | } | |
159 | return error; | |
160 | } | |
161 | EXPORT_SYMBOL_GPL(vfs_listxattr); | |
162 | ||
163 | int | |
164 | vfs_removexattr(struct dentry *dentry, char *name) | |
165 | { | |
166 | struct inode *inode = dentry->d_inode; | |
167 | int error; | |
168 | ||
169 | if (!inode->i_op->removexattr) | |
170 | return -EOPNOTSUPP; | |
171 | ||
172 | error = xattr_permission(inode, name, MAY_WRITE); | |
173 | if (error) | |
174 | return error; | |
175 | ||
176 | error = security_inode_removexattr(dentry, name); | |
177 | if (error) | |
178 | return error; | |
179 | ||
180 | mutex_lock(&inode->i_mutex); | |
181 | error = inode->i_op->removexattr(dentry, name); | |
182 | mutex_unlock(&inode->i_mutex); | |
183 | ||
184 | if (!error) | |
185 | fsnotify_xattr(dentry); | |
186 | return error; | |
187 | } | |
188 | EXPORT_SYMBOL_GPL(vfs_removexattr); | |
189 | ||
190 | ||
191 | /* | |
192 | * Extended attribute SET operations | |
193 | */ | |
194 | static long | |
195 | setxattr(struct dentry *d, char __user *name, void __user *value, | |
196 | size_t size, int flags) | |
197 | { | |
198 | int error; | |
199 | void *kvalue = NULL; | |
200 | char kname[XATTR_NAME_MAX + 1]; | |
201 | ||
202 | if (flags & ~(XATTR_CREATE|XATTR_REPLACE)) | |
203 | return -EINVAL; | |
204 | ||
205 | error = strncpy_from_user(kname, name, sizeof(kname)); | |
206 | if (error == 0 || error == sizeof(kname)) | |
207 | error = -ERANGE; | |
208 | if (error < 0) | |
209 | return error; | |
210 | ||
211 | if (size) { | |
212 | if (size > XATTR_SIZE_MAX) | |
213 | return -E2BIG; | |
214 | kvalue = kmalloc(size, GFP_KERNEL); | |
215 | if (!kvalue) | |
216 | return -ENOMEM; | |
217 | if (copy_from_user(kvalue, value, size)) { | |
218 | kfree(kvalue); | |
219 | return -EFAULT; | |
220 | } | |
221 | } | |
222 | ||
223 | error = vfs_setxattr(d, kname, kvalue, size, flags); | |
224 | kfree(kvalue); | |
225 | return error; | |
226 | } | |
227 | ||
228 | asmlinkage long | |
229 | sys_setxattr(char __user *path, char __user *name, void __user *value, | |
230 | size_t size, int flags) | |
231 | { | |
232 | struct nameidata nd; | |
233 | int error; | |
234 | ||
235 | error = user_path_walk(path, &nd); | |
236 | if (error) | |
237 | return error; | |
238 | error = setxattr(nd.dentry, name, value, size, flags); | |
239 | path_release(&nd); | |
240 | return error; | |
241 | } | |
242 | ||
243 | asmlinkage long | |
244 | sys_lsetxattr(char __user *path, char __user *name, void __user *value, | |
245 | size_t size, int flags) | |
246 | { | |
247 | struct nameidata nd; | |
248 | int error; | |
249 | ||
250 | error = user_path_walk_link(path, &nd); | |
251 | if (error) | |
252 | return error; | |
253 | error = setxattr(nd.dentry, name, value, size, flags); | |
254 | path_release(&nd); | |
255 | return error; | |
256 | } | |
257 | ||
258 | asmlinkage long | |
259 | sys_fsetxattr(int fd, char __user *name, void __user *value, | |
260 | size_t size, int flags) | |
261 | { | |
262 | struct file *f; | |
263 | struct dentry *dentry; | |
264 | int error = -EBADF; | |
265 | ||
266 | f = fget(fd); | |
267 | if (!f) | |
268 | return error; | |
269 | dentry = f->f_path.dentry; | |
270 | audit_inode(NULL, dentry->d_inode); | |
271 | error = setxattr(dentry, name, value, size, flags); | |
272 | fput(f); | |
273 | return error; | |
274 | } | |
275 | ||
276 | /* | |
277 | * Extended attribute GET operations | |
278 | */ | |
279 | static ssize_t | |
280 | getxattr(struct dentry *d, char __user *name, void __user *value, size_t size) | |
281 | { | |
282 | ssize_t error; | |
283 | void *kvalue = NULL; | |
284 | char kname[XATTR_NAME_MAX + 1]; | |
285 | ||
286 | error = strncpy_from_user(kname, name, sizeof(kname)); | |
287 | if (error == 0 || error == sizeof(kname)) | |
288 | error = -ERANGE; | |
289 | if (error < 0) | |
290 | return error; | |
291 | ||
292 | if (size) { | |
293 | if (size > XATTR_SIZE_MAX) | |
294 | size = XATTR_SIZE_MAX; | |
295 | kvalue = kzalloc(size, GFP_KERNEL); | |
296 | if (!kvalue) | |
297 | return -ENOMEM; | |
298 | } | |
299 | ||
300 | error = vfs_getxattr(d, kname, kvalue, size); | |
301 | if (error > 0) { | |
302 | if (size && copy_to_user(value, kvalue, error)) | |
303 | error = -EFAULT; | |
304 | } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) { | |
305 | /* The file system tried to returned a value bigger | |
306 | than XATTR_SIZE_MAX bytes. Not possible. */ | |
307 | error = -E2BIG; | |
308 | } | |
309 | kfree(kvalue); | |
310 | return error; | |
311 | } | |
312 | ||
313 | asmlinkage ssize_t | |
314 | sys_getxattr(char __user *path, char __user *name, void __user *value, | |
315 | size_t size) | |
316 | { | |
317 | struct nameidata nd; | |
318 | ssize_t error; | |
319 | ||
320 | error = user_path_walk(path, &nd); | |
321 | if (error) | |
322 | return error; | |
323 | error = getxattr(nd.dentry, name, value, size); | |
324 | path_release(&nd); | |
325 | return error; | |
326 | } | |
327 | ||
328 | asmlinkage ssize_t | |
329 | sys_lgetxattr(char __user *path, char __user *name, void __user *value, | |
330 | size_t size) | |
331 | { | |
332 | struct nameidata nd; | |
333 | ssize_t error; | |
334 | ||
335 | error = user_path_walk_link(path, &nd); | |
336 | if (error) | |
337 | return error; | |
338 | error = getxattr(nd.dentry, name, value, size); | |
339 | path_release(&nd); | |
340 | return error; | |
341 | } | |
342 | ||
343 | asmlinkage ssize_t | |
344 | sys_fgetxattr(int fd, char __user *name, void __user *value, size_t size) | |
345 | { | |
346 | struct file *f; | |
347 | ssize_t error = -EBADF; | |
348 | ||
349 | f = fget(fd); | |
350 | if (!f) | |
351 | return error; | |
352 | audit_inode(NULL, f->f_path.dentry->d_inode); | |
353 | error = getxattr(f->f_path.dentry, name, value, size); | |
354 | fput(f); | |
355 | return error; | |
356 | } | |
357 | ||
358 | /* | |
359 | * Extended attribute LIST operations | |
360 | */ | |
361 | static ssize_t | |
362 | listxattr(struct dentry *d, char __user *list, size_t size) | |
363 | { | |
364 | ssize_t error; | |
365 | char *klist = NULL; | |
366 | ||
367 | if (size) { | |
368 | if (size > XATTR_LIST_MAX) | |
369 | size = XATTR_LIST_MAX; | |
370 | klist = kmalloc(size, GFP_KERNEL); | |
371 | if (!klist) | |
372 | return -ENOMEM; | |
373 | } | |
374 | ||
375 | error = vfs_listxattr(d, klist, size); | |
376 | if (error > 0) { | |
377 | if (size && copy_to_user(list, klist, error)) | |
378 | error = -EFAULT; | |
379 | } else if (error == -ERANGE && size >= XATTR_LIST_MAX) { | |
380 | /* The file system tried to returned a list bigger | |
381 | than XATTR_LIST_MAX bytes. Not possible. */ | |
382 | error = -E2BIG; | |
383 | } | |
384 | kfree(klist); | |
385 | return error; | |
386 | } | |
387 | ||
388 | asmlinkage ssize_t | |
389 | sys_listxattr(char __user *path, char __user *list, size_t size) | |
390 | { | |
391 | struct nameidata nd; | |
392 | ssize_t error; | |
393 | ||
394 | error = user_path_walk(path, &nd); | |
395 | if (error) | |
396 | return error; | |
397 | error = listxattr(nd.dentry, list, size); | |
398 | path_release(&nd); | |
399 | return error; | |
400 | } | |
401 | ||
402 | asmlinkage ssize_t | |
403 | sys_llistxattr(char __user *path, char __user *list, size_t size) | |
404 | { | |
405 | struct nameidata nd; | |
406 | ssize_t error; | |
407 | ||
408 | error = user_path_walk_link(path, &nd); | |
409 | if (error) | |
410 | return error; | |
411 | error = listxattr(nd.dentry, list, size); | |
412 | path_release(&nd); | |
413 | return error; | |
414 | } | |
415 | ||
416 | asmlinkage ssize_t | |
417 | sys_flistxattr(int fd, char __user *list, size_t size) | |
418 | { | |
419 | struct file *f; | |
420 | ssize_t error = -EBADF; | |
421 | ||
422 | f = fget(fd); | |
423 | if (!f) | |
424 | return error; | |
425 | audit_inode(NULL, f->f_path.dentry->d_inode); | |
426 | error = listxattr(f->f_path.dentry, list, size); | |
427 | fput(f); | |
428 | return error; | |
429 | } | |
430 | ||
431 | /* | |
432 | * Extended attribute REMOVE operations | |
433 | */ | |
434 | static long | |
435 | removexattr(struct dentry *d, char __user *name) | |
436 | { | |
437 | int error; | |
438 | char kname[XATTR_NAME_MAX + 1]; | |
439 | ||
440 | error = strncpy_from_user(kname, name, sizeof(kname)); | |
441 | if (error == 0 || error == sizeof(kname)) | |
442 | error = -ERANGE; | |
443 | if (error < 0) | |
444 | return error; | |
445 | ||
446 | return vfs_removexattr(d, kname); | |
447 | } | |
448 | ||
449 | asmlinkage long | |
450 | sys_removexattr(char __user *path, char __user *name) | |
451 | { | |
452 | struct nameidata nd; | |
453 | int error; | |
454 | ||
455 | error = user_path_walk(path, &nd); | |
456 | if (error) | |
457 | return error; | |
458 | error = removexattr(nd.dentry, name); | |
459 | path_release(&nd); | |
460 | return error; | |
461 | } | |
462 | ||
463 | asmlinkage long | |
464 | sys_lremovexattr(char __user *path, char __user *name) | |
465 | { | |
466 | struct nameidata nd; | |
467 | int error; | |
468 | ||
469 | error = user_path_walk_link(path, &nd); | |
470 | if (error) | |
471 | return error; | |
472 | error = removexattr(nd.dentry, name); | |
473 | path_release(&nd); | |
474 | return error; | |
475 | } | |
476 | ||
477 | asmlinkage long | |
478 | sys_fremovexattr(int fd, char __user *name) | |
479 | { | |
480 | struct file *f; | |
481 | struct dentry *dentry; | |
482 | int error = -EBADF; | |
483 | ||
484 | f = fget(fd); | |
485 | if (!f) | |
486 | return error; | |
487 | dentry = f->f_path.dentry; | |
488 | audit_inode(NULL, dentry->d_inode); | |
489 | error = removexattr(dentry, name); | |
490 | fput(f); | |
491 | return error; | |
492 | } | |
493 | ||
494 | ||
495 | static const char * | |
496 | strcmp_prefix(const char *a, const char *a_prefix) | |
497 | { | |
498 | while (*a_prefix && *a == *a_prefix) { | |
499 | a++; | |
500 | a_prefix++; | |
501 | } | |
502 | return *a_prefix ? NULL : a; | |
503 | } | |
504 | ||
505 | /* | |
506 | * In order to implement different sets of xattr operations for each xattr | |
507 | * prefix with the generic xattr API, a filesystem should create a | |
508 | * null-terminated array of struct xattr_handler (one for each prefix) and | |
509 | * hang a pointer to it off of the s_xattr field of the superblock. | |
510 | * | |
511 | * The generic_fooxattr() functions will use this list to dispatch xattr | |
512 | * operations to the correct xattr_handler. | |
513 | */ | |
514 | #define for_each_xattr_handler(handlers, handler) \ | |
515 | for ((handler) = *(handlers)++; \ | |
516 | (handler) != NULL; \ | |
517 | (handler) = *(handlers)++) | |
518 | ||
519 | /* | |
520 | * Find the xattr_handler with the matching prefix. | |
521 | */ | |
522 | static struct xattr_handler * | |
523 | xattr_resolve_name(struct xattr_handler **handlers, const char **name) | |
524 | { | |
525 | struct xattr_handler *handler; | |
526 | ||
527 | if (!*name) | |
528 | return NULL; | |
529 | ||
530 | for_each_xattr_handler(handlers, handler) { | |
531 | const char *n = strcmp_prefix(*name, handler->prefix); | |
532 | if (n) { | |
533 | *name = n; | |
534 | break; | |
535 | } | |
536 | } | |
537 | return handler; | |
538 | } | |
539 | ||
540 | /* | |
541 | * Find the handler for the prefix and dispatch its get() operation. | |
542 | */ | |
543 | ssize_t | |
544 | generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size) | |
545 | { | |
546 | struct xattr_handler *handler; | |
547 | struct inode *inode = dentry->d_inode; | |
548 | ||
549 | handler = xattr_resolve_name(inode->i_sb->s_xattr, &name); | |
550 | if (!handler) | |
551 | return -EOPNOTSUPP; | |
552 | return handler->get(inode, name, buffer, size); | |
553 | } | |
554 | ||
555 | /* | |
556 | * Combine the results of the list() operation from every xattr_handler in the | |
557 | * list. | |
558 | */ | |
559 | ssize_t | |
560 | generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size) | |
561 | { | |
562 | struct inode *inode = dentry->d_inode; | |
563 | struct xattr_handler *handler, **handlers = inode->i_sb->s_xattr; | |
564 | unsigned int size = 0; | |
565 | ||
566 | if (!buffer) { | |
567 | for_each_xattr_handler(handlers, handler) | |
568 | size += handler->list(inode, NULL, 0, NULL, 0); | |
569 | } else { | |
570 | char *buf = buffer; | |
571 | ||
572 | for_each_xattr_handler(handlers, handler) { | |
573 | size = handler->list(inode, buf, buffer_size, NULL, 0); | |
574 | if (size > buffer_size) | |
575 | return -ERANGE; | |
576 | buf += size; | |
577 | buffer_size -= size; | |
578 | } | |
579 | size = buf - buffer; | |
580 | } | |
581 | return size; | |
582 | } | |
583 | ||
584 | /* | |
585 | * Find the handler for the prefix and dispatch its set() operation. | |
586 | */ | |
587 | int | |
588 | generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags) | |
589 | { | |
590 | struct xattr_handler *handler; | |
591 | struct inode *inode = dentry->d_inode; | |
592 | ||
593 | if (size == 0) | |
594 | value = ""; /* empty EA, do not remove */ | |
595 | handler = xattr_resolve_name(inode->i_sb->s_xattr, &name); | |
596 | if (!handler) | |
597 | return -EOPNOTSUPP; | |
598 | return handler->set(inode, name, value, size, flags); | |
599 | } | |
600 | ||
601 | /* | |
602 | * Find the handler for the prefix and dispatch its set() operation to remove | |
603 | * any associated extended attribute. | |
604 | */ | |
605 | int | |
606 | generic_removexattr(struct dentry *dentry, const char *name) | |
607 | { | |
608 | struct xattr_handler *handler; | |
609 | struct inode *inode = dentry->d_inode; | |
610 | ||
611 | handler = xattr_resolve_name(inode->i_sb->s_xattr, &name); | |
612 | if (!handler) | |
613 | return -EOPNOTSUPP; | |
614 | return handler->set(inode, name, NULL, 0, XATTR_REPLACE); | |
615 | } | |
616 | ||
617 | EXPORT_SYMBOL(generic_getxattr); | |
618 | EXPORT_SYMBOL(generic_listxattr); | |
619 | EXPORT_SYMBOL(generic_setxattr); | |
620 | EXPORT_SYMBOL(generic_removexattr); |