xattr.c 14 KB

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