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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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>
Linus Torvalds1da177e2005-04-16 15:20:36 -070012#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>
Robert Love0eeca282005-07-12 17:06:03 -040018#include <linux/fsnotify.h>
Amy Griffis73241cc2005-11-03 16:00:25 +000019#include <linux/audit.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070020#include <asm/uaccess.h>
21
Christoph Hellwig5be196e2006-01-09 20:51:55 -080022
akpm@osdl.orge0ad7b02006-01-09 20:51:56 -080023/*
24 * Check permissions for extended attribute access. This is a bit complicated
25 * because different namespaces have very different rules.
26 */
27static int
28xattr_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 /*
Andreas Gruenbacherf1f2d872006-11-02 22:07:29 -080050 * The trusted.* namespace can only be accessed by a privileged user.
akpm@osdl.orge0ad7b02006-01-09 20:51:56 -080051 */
52 if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN))
53 return (capable(CAP_SYS_ADMIN) ? 0 : -EPERM);
54
Andreas Gruenbacherf1f2d872006-11-02 22:07:29 -080055 /* 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 */
akpm@osdl.orge0ad7b02006-01-09 20:51:56 -080059 if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
Andreas Gruenbacherf1f2d872006-11-02 22:07:29 -080060 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) && (current->fsuid != inode->i_uid) &&
64 !capable(CAP_FOWNER))
akpm@osdl.orge0ad7b02006-01-09 20:51:56 -080065 return -EPERM;
66 }
67
68 return permission(inode, mask, NULL);
69}
70
Christoph Hellwig5be196e2006-01-09 20:51:55 -080071int
72vfs_setxattr(struct dentry *dentry, char *name, void *value,
73 size_t size, int flags)
74{
75 struct inode *inode = dentry->d_inode;
76 int error;
77
akpm@osdl.orge0ad7b02006-01-09 20:51:56 -080078 error = xattr_permission(inode, name, MAY_WRITE);
79 if (error)
80 return error;
81
Christoph Hellwig5be196e2006-01-09 20:51:55 -080082 mutex_lock(&inode->i_mutex);
83 error = security_inode_setxattr(dentry, name, value, size, flags);
84 if (error)
85 goto out;
86 error = -EOPNOTSUPP;
87 if (inode->i_op->setxattr) {
88 error = inode->i_op->setxattr(dentry, name, value, size, flags);
89 if (!error) {
90 fsnotify_xattr(dentry);
91 security_inode_post_setxattr(dentry, name, value,
92 size, flags);
93 }
94 } else if (!strncmp(name, XATTR_SECURITY_PREFIX,
akpm@osdl.orge0ad7b02006-01-09 20:51:56 -080095 XATTR_SECURITY_PREFIX_LEN)) {
96 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
Christoph Hellwig5be196e2006-01-09 20:51:55 -080097 error = security_inode_setsecurity(inode, suffix, value,
98 size, flags);
99 if (!error)
100 fsnotify_xattr(dentry);
101 }
102out:
103 mutex_unlock(&inode->i_mutex);
104 return error;
105}
106EXPORT_SYMBOL_GPL(vfs_setxattr);
107
108ssize_t
109vfs_getxattr(struct dentry *dentry, char *name, void *value, size_t size)
110{
111 struct inode *inode = dentry->d_inode;
112 int error;
113
akpm@osdl.orge0ad7b02006-01-09 20:51:56 -0800114 error = xattr_permission(inode, name, MAY_READ);
115 if (error)
116 return error;
117
Christoph Hellwig5be196e2006-01-09 20:51:55 -0800118 error = security_inode_getxattr(dentry, name);
119 if (error)
120 return error;
121
122 if (inode->i_op->getxattr)
123 error = inode->i_op->getxattr(dentry, name, value, size);
124 else
125 error = -EOPNOTSUPP;
126
127 if (!strncmp(name, XATTR_SECURITY_PREFIX,
akpm@osdl.orge0ad7b02006-01-09 20:51:56 -0800128 XATTR_SECURITY_PREFIX_LEN)) {
129 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
Christoph Hellwig5be196e2006-01-09 20:51:55 -0800130 int ret = security_inode_getsecurity(inode, suffix, value,
131 size, error);
132 /*
133 * Only overwrite the return value if a security module
134 * is actually active.
135 */
136 if (ret != -EOPNOTSUPP)
137 error = ret;
138 }
139
140 return error;
141}
142EXPORT_SYMBOL_GPL(vfs_getxattr);
143
Bill Nottingham659564c2006-10-09 16:10:48 -0400144ssize_t
145vfs_listxattr(struct dentry *d, char *list, size_t size)
146{
147 ssize_t error;
148
149 error = security_inode_listxattr(d);
150 if (error)
151 return error;
152 error = -EOPNOTSUPP;
153 if (d->d_inode->i_op && d->d_inode->i_op->listxattr) {
154 error = d->d_inode->i_op->listxattr(d, list, size);
155 } else {
156 error = security_inode_listsecurity(d->d_inode, list, size);
157 if (size && error > size)
158 error = -ERANGE;
159 }
160 return error;
161}
162EXPORT_SYMBOL_GPL(vfs_listxattr);
163
Christoph Hellwig5be196e2006-01-09 20:51:55 -0800164int
165vfs_removexattr(struct dentry *dentry, char *name)
166{
167 struct inode *inode = dentry->d_inode;
168 int error;
169
170 if (!inode->i_op->removexattr)
171 return -EOPNOTSUPP;
172
akpm@osdl.orge0ad7b02006-01-09 20:51:56 -0800173 error = xattr_permission(inode, name, MAY_WRITE);
174 if (error)
175 return error;
176
Christoph Hellwig5be196e2006-01-09 20:51:55 -0800177 error = security_inode_removexattr(dentry, name);
178 if (error)
179 return error;
180
181 mutex_lock(&inode->i_mutex);
182 error = inode->i_op->removexattr(dentry, name);
183 mutex_unlock(&inode->i_mutex);
184
185 if (!error)
186 fsnotify_xattr(dentry);
187 return error;
188}
189EXPORT_SYMBOL_GPL(vfs_removexattr);
190
191
Linus Torvalds1da177e2005-04-16 15:20:36 -0700192/*
193 * Extended attribute SET operations
194 */
195static long
196setxattr(struct dentry *d, char __user *name, void __user *value,
197 size_t size, int flags)
198{
199 int error;
200 void *kvalue = NULL;
201 char kname[XATTR_NAME_MAX + 1];
202
203 if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
204 return -EINVAL;
205
206 error = strncpy_from_user(kname, name, sizeof(kname));
207 if (error == 0 || error == sizeof(kname))
208 error = -ERANGE;
209 if (error < 0)
210 return error;
211
212 if (size) {
213 if (size > XATTR_SIZE_MAX)
214 return -E2BIG;
215 kvalue = kmalloc(size, GFP_KERNEL);
216 if (!kvalue)
217 return -ENOMEM;
218 if (copy_from_user(kvalue, value, size)) {
219 kfree(kvalue);
220 return -EFAULT;
221 }
222 }
223
Christoph Hellwig5be196e2006-01-09 20:51:55 -0800224 error = vfs_setxattr(d, kname, kvalue, size, flags);
Jesper Juhlf99d49a2005-11-07 01:01:34 -0800225 kfree(kvalue);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700226 return error;
227}
228
229asmlinkage long
230sys_setxattr(char __user *path, char __user *name, void __user *value,
231 size_t size, int flags)
232{
233 struct nameidata nd;
234 int error;
235
236 error = user_path_walk(path, &nd);
237 if (error)
238 return error;
239 error = setxattr(nd.dentry, name, value, size, flags);
240 path_release(&nd);
241 return error;
242}
243
244asmlinkage long
245sys_lsetxattr(char __user *path, char __user *name, void __user *value,
246 size_t size, int flags)
247{
248 struct nameidata nd;
249 int error;
250
251 error = user_path_walk_link(path, &nd);
252 if (error)
253 return error;
254 error = setxattr(nd.dentry, name, value, size, flags);
255 path_release(&nd);
256 return error;
257}
258
259asmlinkage long
260sys_fsetxattr(int fd, char __user *name, void __user *value,
261 size_t size, int flags)
262{
263 struct file *f;
Amy Griffis73241cc2005-11-03 16:00:25 +0000264 struct dentry *dentry;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700265 int error = -EBADF;
266
267 f = fget(fd);
268 if (!f)
269 return error;
Josef "Jeff" Sipek0f7fc9e2006-12-08 02:36:35 -0800270 dentry = f->f_path.dentry;
Amy Griffis9c937dc2006-06-08 23:19:31 -0400271 audit_inode(NULL, dentry->d_inode);
Amy Griffis73241cc2005-11-03 16:00:25 +0000272 error = setxattr(dentry, name, value, size, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700273 fput(f);
274 return error;
275}
276
277/*
278 * Extended attribute GET operations
279 */
280static ssize_t
281getxattr(struct dentry *d, char __user *name, void __user *value, size_t size)
282{
283 ssize_t error;
284 void *kvalue = NULL;
285 char kname[XATTR_NAME_MAX + 1];
286
287 error = strncpy_from_user(kname, name, sizeof(kname));
288 if (error == 0 || error == sizeof(kname))
289 error = -ERANGE;
290 if (error < 0)
291 return error;
292
293 if (size) {
294 if (size > XATTR_SIZE_MAX)
295 size = XATTR_SIZE_MAX;
James Morrisd381d8a2005-10-30 14:59:22 -0800296 kvalue = kzalloc(size, GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700297 if (!kvalue)
298 return -ENOMEM;
299 }
300
Christoph Hellwig5be196e2006-01-09 20:51:55 -0800301 error = vfs_getxattr(d, kname, kvalue, size);
Stephen Smalleyf549d6c2005-09-03 15:55:18 -0700302 if (error > 0) {
303 if (size && copy_to_user(value, kvalue, error))
304 error = -EFAULT;
305 } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
306 /* The file system tried to returned a value bigger
307 than XATTR_SIZE_MAX bytes. Not possible. */
308 error = -E2BIG;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700309 }
Jesper Juhlf99d49a2005-11-07 01:01:34 -0800310 kfree(kvalue);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700311 return error;
312}
313
314asmlinkage ssize_t
315sys_getxattr(char __user *path, char __user *name, void __user *value,
316 size_t size)
317{
318 struct nameidata nd;
319 ssize_t error;
320
321 error = user_path_walk(path, &nd);
322 if (error)
323 return error;
324 error = getxattr(nd.dentry, name, value, size);
325 path_release(&nd);
326 return error;
327}
328
329asmlinkage ssize_t
330sys_lgetxattr(char __user *path, char __user *name, void __user *value,
331 size_t size)
332{
333 struct nameidata nd;
334 ssize_t error;
335
336 error = user_path_walk_link(path, &nd);
337 if (error)
338 return error;
339 error = getxattr(nd.dentry, name, value, size);
340 path_release(&nd);
341 return error;
342}
343
344asmlinkage ssize_t
345sys_fgetxattr(int fd, char __user *name, void __user *value, size_t size)
346{
347 struct file *f;
348 ssize_t error = -EBADF;
349
350 f = fget(fd);
351 if (!f)
352 return error;
Josef "Jeff" Sipek0f7fc9e2006-12-08 02:36:35 -0800353 error = getxattr(f->f_path.dentry, name, value, size);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700354 fput(f);
355 return error;
356}
357
358/*
359 * Extended attribute LIST operations
360 */
361static ssize_t
362listxattr(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
Bill Nottingham659564c2006-10-09 16:10:48 -0400375 error = vfs_listxattr(d, klist, size);
Stephen Smalleyf549d6c2005-09-03 15:55:18 -0700376 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;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700383 }
Jesper Juhlf99d49a2005-11-07 01:01:34 -0800384 kfree(klist);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700385 return error;
386}
387
388asmlinkage ssize_t
389sys_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
402asmlinkage ssize_t
403sys_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
416asmlinkage ssize_t
417sys_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;
Josef "Jeff" Sipek0f7fc9e2006-12-08 02:36:35 -0800425 error = listxattr(f->f_path.dentry, list, size);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700426 fput(f);
427 return error;
428}
429
430/*
431 * Extended attribute REMOVE operations
432 */
433static long
434removexattr(struct dentry *d, char __user *name)
435{
436 int error;
437 char kname[XATTR_NAME_MAX + 1];
438
439 error = strncpy_from_user(kname, name, sizeof(kname));
440 if (error == 0 || error == sizeof(kname))
441 error = -ERANGE;
442 if (error < 0)
443 return error;
444
Christoph Hellwig5be196e2006-01-09 20:51:55 -0800445 return vfs_removexattr(d, kname);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700446}
447
448asmlinkage long
449sys_removexattr(char __user *path, char __user *name)
450{
451 struct nameidata nd;
452 int error;
453
454 error = user_path_walk(path, &nd);
455 if (error)
456 return error;
457 error = removexattr(nd.dentry, name);
458 path_release(&nd);
459 return error;
460}
461
462asmlinkage long
463sys_lremovexattr(char __user *path, char __user *name)
464{
465 struct nameidata nd;
466 int error;
467
468 error = user_path_walk_link(path, &nd);
469 if (error)
470 return error;
471 error = removexattr(nd.dentry, name);
472 path_release(&nd);
473 return error;
474}
475
476asmlinkage long
477sys_fremovexattr(int fd, char __user *name)
478{
479 struct file *f;
Amy Griffis73241cc2005-11-03 16:00:25 +0000480 struct dentry *dentry;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700481 int error = -EBADF;
482
483 f = fget(fd);
484 if (!f)
485 return error;
Josef "Jeff" Sipek0f7fc9e2006-12-08 02:36:35 -0800486 dentry = f->f_path.dentry;
Amy Griffis9c937dc2006-06-08 23:19:31 -0400487 audit_inode(NULL, dentry->d_inode);
Amy Griffis73241cc2005-11-03 16:00:25 +0000488 error = removexattr(dentry, name);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700489 fput(f);
490 return error;
491}
492
493
494static const char *
495strcmp_prefix(const char *a, const char *a_prefix)
496{
497 while (*a_prefix && *a == *a_prefix) {
498 a++;
499 a_prefix++;
500 }
501 return *a_prefix ? NULL : a;
502}
503
504/*
505 * In order to implement different sets of xattr operations for each xattr
506 * prefix with the generic xattr API, a filesystem should create a
507 * null-terminated array of struct xattr_handler (one for each prefix) and
508 * hang a pointer to it off of the s_xattr field of the superblock.
509 *
510 * The generic_fooxattr() functions will use this list to dispatch xattr
511 * operations to the correct xattr_handler.
512 */
513#define for_each_xattr_handler(handlers, handler) \
514 for ((handler) = *(handlers)++; \
515 (handler) != NULL; \
516 (handler) = *(handlers)++)
517
518/*
519 * Find the xattr_handler with the matching prefix.
520 */
521static struct xattr_handler *
522xattr_resolve_name(struct xattr_handler **handlers, const char **name)
523{
524 struct xattr_handler *handler;
525
526 if (!*name)
527 return NULL;
528
529 for_each_xattr_handler(handlers, handler) {
530 const char *n = strcmp_prefix(*name, handler->prefix);
531 if (n) {
532 *name = n;
533 break;
534 }
535 }
536 return handler;
537}
538
539/*
540 * Find the handler for the prefix and dispatch its get() operation.
541 */
542ssize_t
543generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size)
544{
545 struct xattr_handler *handler;
546 struct inode *inode = dentry->d_inode;
547
548 handler = xattr_resolve_name(inode->i_sb->s_xattr, &name);
549 if (!handler)
550 return -EOPNOTSUPP;
551 return handler->get(inode, name, buffer, size);
552}
553
554/*
555 * Combine the results of the list() operation from every xattr_handler in the
556 * list.
557 */
558ssize_t
559generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
560{
561 struct inode *inode = dentry->d_inode;
562 struct xattr_handler *handler, **handlers = inode->i_sb->s_xattr;
563 unsigned int size = 0;
564
565 if (!buffer) {
566 for_each_xattr_handler(handlers, handler)
567 size += handler->list(inode, NULL, 0, NULL, 0);
568 } else {
569 char *buf = buffer;
570
571 for_each_xattr_handler(handlers, handler) {
572 size = handler->list(inode, buf, buffer_size, NULL, 0);
573 if (size > buffer_size)
574 return -ERANGE;
575 buf += size;
576 buffer_size -= size;
577 }
578 size = buf - buffer;
579 }
580 return size;
581}
582
583/*
584 * Find the handler for the prefix and dispatch its set() operation.
585 */
586int
587generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags)
588{
589 struct xattr_handler *handler;
590 struct inode *inode = dentry->d_inode;
591
592 if (size == 0)
593 value = ""; /* empty EA, do not remove */
594 handler = xattr_resolve_name(inode->i_sb->s_xattr, &name);
595 if (!handler)
596 return -EOPNOTSUPP;
597 return handler->set(inode, name, value, size, flags);
598}
599
600/*
601 * Find the handler for the prefix and dispatch its set() operation to remove
602 * any associated extended attribute.
603 */
604int
605generic_removexattr(struct dentry *dentry, const char *name)
606{
607 struct xattr_handler *handler;
608 struct inode *inode = dentry->d_inode;
609
610 handler = xattr_resolve_name(inode->i_sb->s_xattr, &name);
611 if (!handler)
612 return -EOPNOTSUPP;
613 return handler->set(inode, name, NULL, 0, XATTR_REPLACE);
614}
615
616EXPORT_SYMBOL(generic_getxattr);
617EXPORT_SYMBOL(generic_listxattr);
618EXPORT_SYMBOL(generic_setxattr);
619EXPORT_SYMBOL(generic_removexattr);