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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/mount.h>
15#include <linux/namei.h>
16#include <linux/security.h>
17#include <linux/evm.h>
18#include <linux/syscalls.h>
19#include <linux/export.h>
20#include <linux/fsnotify.h>
21#include <linux/audit.h>
22#include <linux/vmalloc.h>
23#include <linux/posix_acl_xattr.h>
24
25#include <linux/uaccess.h>
26
27static const char *
28strcmp_prefix(const char *a, const char *a_prefix)
29{
30 while (*a_prefix && *a == *a_prefix) {
31 a++;
32 a_prefix++;
33 }
34 return *a_prefix ? NULL : a;
35}
36
37/*
38 * In order to implement different sets of xattr operations for each xattr
39 * prefix, a filesystem should create a null-terminated array of struct
40 * xattr_handler (one for each prefix) and hang a pointer to it off of the
41 * s_xattr field of the superblock.
42 */
43#define for_each_xattr_handler(handlers, handler) \
44 if (handlers) \
45 for ((handler) = *(handlers)++; \
46 (handler) != NULL; \
47 (handler) = *(handlers)++)
48
49/*
50 * Find the xattr_handler with the matching prefix.
51 */
52static const struct xattr_handler *
53xattr_resolve_name(struct inode *inode, const char **name)
54{
55 const struct xattr_handler **handlers = inode->i_sb->s_xattr;
56 const struct xattr_handler *handler;
57
58 if (!(inode->i_opflags & IOP_XATTR)) {
59 if (unlikely(is_bad_inode(inode)))
60 return ERR_PTR(-EIO);
61 return ERR_PTR(-EOPNOTSUPP);
62 }
63 for_each_xattr_handler(handlers, handler) {
64 const char *n;
65
66 n = strcmp_prefix(*name, xattr_prefix(handler));
67 if (n) {
68 if (!handler->prefix ^ !*n) {
69 if (*n)
70 continue;
71 return ERR_PTR(-EINVAL);
72 }
73 *name = n;
74 return handler;
75 }
76 }
77 return ERR_PTR(-EOPNOTSUPP);
78}
79
80/*
81 * Check permissions for extended attribute access. This is a bit complicated
82 * because different namespaces have very different rules.
83 */
84static int
85xattr_permission(struct inode *inode, const char *name, int mask)
86{
87 /*
88 * We can never set or remove an extended attribute on a read-only
89 * filesystem or on an immutable / append-only inode.
90 */
91 if (mask & MAY_WRITE) {
92 if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
93 return -EPERM;
94 /*
95 * Updating an xattr will likely cause i_uid and i_gid
96 * to be writen back improperly if their true value is
97 * unknown to the vfs.
98 */
99 if (HAS_UNMAPPED_ID(inode))
100 return -EPERM;
101 }
102
103 /*
104 * No restriction for security.* and system.* from the VFS. Decision
105 * on these is left to the underlying filesystem / security module.
106 */
107 if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
108 !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
109 return 0;
110
111 /*
112 * The trusted.* namespace can only be accessed by privileged users.
113 */
114 if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
115 if (!capable(CAP_SYS_ADMIN))
116 return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
117 return 0;
118 }
119
120 /*
121 * In the user.* namespace, only regular files and directories can have
122 * extended attributes. For sticky directories, only the owner and
123 * privileged users can write attributes.
124 */
125 if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
126 if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
127 return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
128 if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&
129 (mask & MAY_WRITE) && !inode_owner_or_capable(inode))
130 return -EPERM;
131 }
132
133 return inode_permission(inode, mask);
134}
135
136int
137__vfs_setxattr(struct dentry *dentry, struct inode *inode, const char *name,
138 const void *value, size_t size, int flags)
139{
140 const struct xattr_handler *handler;
141
142 handler = xattr_resolve_name(inode, &name);
143 if (IS_ERR(handler))
144 return PTR_ERR(handler);
145 if (!handler->set)
146 return -EOPNOTSUPP;
147 if (size == 0)
148 value = ""; /* empty EA, do not remove */
149 return handler->set(handler, dentry, inode, name, value, size, flags);
150}
151EXPORT_SYMBOL(__vfs_setxattr);
152
153/**
154 * __vfs_setxattr_noperm - perform setxattr operation without performing
155 * permission checks.
156 *
157 * @dentry - object to perform setxattr on
158 * @name - xattr name to set
159 * @value - value to set @name to
160 * @size - size of @value
161 * @flags - flags to pass into filesystem operations
162 *
163 * returns the result of the internal setxattr or setsecurity operations.
164 *
165 * This function requires the caller to lock the inode's i_mutex before it
166 * is executed. It also assumes that the caller will make the appropriate
167 * permission checks.
168 */
169int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
170 const void *value, size_t size, int flags)
171{
172 struct inode *inode = dentry->d_inode;
173 int error = -EAGAIN;
174 int issec = !strncmp(name, XATTR_SECURITY_PREFIX,
175 XATTR_SECURITY_PREFIX_LEN);
176
177 if (issec)
178 inode->i_flags &= ~S_NOSEC;
179 if (inode->i_opflags & IOP_XATTR) {
180 error = __vfs_setxattr(dentry, inode, name, value, size, flags);
181 if (!error) {
182 fsnotify_xattr(dentry);
183 security_inode_post_setxattr(dentry, name, value,
184 size, flags);
185 }
186 } else {
187 if (unlikely(is_bad_inode(inode)))
188 return -EIO;
189 }
190 if (error == -EAGAIN) {
191 error = -EOPNOTSUPP;
192
193 if (issec) {
194 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
195
196 error = security_inode_setsecurity(inode, suffix, value,
197 size, flags);
198 if (!error)
199 fsnotify_xattr(dentry);
200 }
201 }
202
203 return error;
204}
205
206
207int
208vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
209 size_t size, int flags)
210{
211 struct inode *inode = dentry->d_inode;
212 int error;
213
214 error = xattr_permission(inode, name, MAY_WRITE);
215 if (error)
216 return error;
217
218 inode_lock(inode);
219 error = security_inode_setxattr(dentry, name, value, size, flags);
220 if (error)
221 goto out;
222
223 error = __vfs_setxattr_noperm(dentry, name, value, size, flags);
224
225out:
226 inode_unlock(inode);
227 return error;
228}
229EXPORT_SYMBOL_GPL(vfs_setxattr);
230
231ssize_t
232xattr_getsecurity(struct inode *inode, const char *name, void *value,
233 size_t size)
234{
235 void *buffer = NULL;
236 ssize_t len;
237
238 if (!value || !size) {
239 len = security_inode_getsecurity(inode, name, &buffer, false);
240 goto out_noalloc;
241 }
242
243 len = security_inode_getsecurity(inode, name, &buffer, true);
244 if (len < 0)
245 return len;
246 if (size < len) {
247 len = -ERANGE;
248 goto out;
249 }
250 memcpy(value, buffer, len);
251out:
252 security_release_secctx(buffer, len);
253out_noalloc:
254 return len;
255}
256EXPORT_SYMBOL_GPL(xattr_getsecurity);
257
258/*
259 * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
260 *
261 * Allocate memory, if not already allocated, or re-allocate correct size,
262 * before retrieving the extended attribute.
263 *
264 * Returns the result of alloc, if failed, or the getxattr operation.
265 */
266ssize_t
267vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value,
268 size_t xattr_size, gfp_t flags)
269{
270 const struct xattr_handler *handler;
271 struct inode *inode = dentry->d_inode;
272 char *value = *xattr_value;
273 int error;
274
275 error = xattr_permission(inode, name, MAY_READ);
276 if (error)
277 return error;
278
279 handler = xattr_resolve_name(inode, &name);
280 if (IS_ERR(handler))
281 return PTR_ERR(handler);
282 if (!handler->get)
283 return -EOPNOTSUPP;
284 error = handler->get(handler, dentry, inode, name, NULL, 0);
285 if (error < 0)
286 return error;
287
288 if (!value || (error > xattr_size)) {
289 value = krealloc(*xattr_value, error + 1, flags);
290 if (!value)
291 return -ENOMEM;
292 memset(value, 0, error + 1);
293 }
294
295 error = handler->get(handler, dentry, inode, name, value, error);
296 *xattr_value = value;
297 return error;
298}
299
300ssize_t
301__vfs_getxattr(struct dentry *dentry, struct inode *inode, const char *name,
302 void *value, size_t size)
303{
304 const struct xattr_handler *handler;
305
306 handler = xattr_resolve_name(inode, &name);
307 if (IS_ERR(handler))
308 return PTR_ERR(handler);
309 if (!handler->get)
310 return -EOPNOTSUPP;
311 return handler->get(handler, dentry, inode, name, value, size);
312}
313EXPORT_SYMBOL(__vfs_getxattr);
314
315ssize_t
316vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
317{
318 struct inode *inode = dentry->d_inode;
319 int error;
320
321 error = xattr_permission(inode, name, MAY_READ);
322 if (error)
323 return error;
324
325 error = security_inode_getxattr(dentry, name);
326 if (error)
327 return error;
328
329 if (!strncmp(name, XATTR_SECURITY_PREFIX,
330 XATTR_SECURITY_PREFIX_LEN)) {
331 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
332 int ret = xattr_getsecurity(inode, suffix, value, size);
333 /*
334 * Only overwrite the return value if a security module
335 * is actually active.
336 */
337 if (ret == -EOPNOTSUPP)
338 goto nolsm;
339 return ret;
340 }
341nolsm:
342 return __vfs_getxattr(dentry, inode, name, value, size);
343}
344EXPORT_SYMBOL_GPL(vfs_getxattr);
345
346ssize_t
347vfs_listxattr(struct dentry *dentry, char *list, size_t size)
348{
349 struct inode *inode = d_inode(dentry);
350 ssize_t error;
351
352 error = security_inode_listxattr(dentry);
353 if (error)
354 return error;
355 if (inode->i_op->listxattr && (inode->i_opflags & IOP_XATTR)) {
356 error = -EOPNOTSUPP;
357 error = inode->i_op->listxattr(dentry, list, size);
358 } else {
359 error = security_inode_listsecurity(inode, list, size);
360 if (size && error > size)
361 error = -ERANGE;
362 }
363 return error;
364}
365EXPORT_SYMBOL_GPL(vfs_listxattr);
366
367int
368__vfs_removexattr(struct dentry *dentry, const char *name)
369{
370 struct inode *inode = d_inode(dentry);
371 const struct xattr_handler *handler;
372
373 handler = xattr_resolve_name(inode, &name);
374 if (IS_ERR(handler))
375 return PTR_ERR(handler);
376 if (!handler->set)
377 return -EOPNOTSUPP;
378 return handler->set(handler, dentry, inode, name, NULL, 0, XATTR_REPLACE);
379}
380EXPORT_SYMBOL(__vfs_removexattr);
381
382int
383vfs_removexattr(struct dentry *dentry, const char *name)
384{
385 struct inode *inode = dentry->d_inode;
386 int error;
387
388 error = xattr_permission(inode, name, MAY_WRITE);
389 if (error)
390 return error;
391
392 inode_lock(inode);
393 error = security_inode_removexattr(dentry, name);
394 if (error)
395 goto out;
396
397 error = __vfs_removexattr(dentry, name);
398
399 if (!error) {
400 fsnotify_xattr(dentry);
401 evm_inode_post_removexattr(dentry, name);
402 }
403
404out:
405 inode_unlock(inode);
406 return error;
407}
408EXPORT_SYMBOL_GPL(vfs_removexattr);
409
410
411/*
412 * Extended attribute SET operations
413 */
414static long
415setxattr(struct dentry *d, const char __user *name, const void __user *value,
416 size_t size, int flags)
417{
418 int error;
419 void *kvalue = NULL;
420 char kname[XATTR_NAME_MAX + 1];
421
422 if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
423 return -EINVAL;
424
425 error = strncpy_from_user(kname, name, sizeof(kname));
426 if (error == 0 || error == sizeof(kname))
427 error = -ERANGE;
428 if (error < 0)
429 return error;
430
431 if (size) {
432 if (size > XATTR_SIZE_MAX)
433 return -E2BIG;
434 kvalue = kmalloc(size, GFP_KERNEL | __GFP_NOWARN);
435 if (!kvalue) {
436 kvalue = vmalloc(size);
437 if (!kvalue)
438 return -ENOMEM;
439 }
440 if (copy_from_user(kvalue, value, size)) {
441 error = -EFAULT;
442 goto out;
443 }
444 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
445 (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
446 posix_acl_fix_xattr_from_user(kvalue, size);
447 }
448
449 error = vfs_setxattr(d, kname, kvalue, size, flags);
450out:
451 kvfree(kvalue);
452
453 return error;
454}
455
456static int path_setxattr(const char __user *pathname,
457 const char __user *name, const void __user *value,
458 size_t size, int flags, unsigned int lookup_flags)
459{
460 struct path path;
461 int error;
462retry:
463 error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
464 if (error)
465 return error;
466 error = mnt_want_write(path.mnt);
467 if (!error) {
468 error = setxattr(path.dentry, name, value, size, flags);
469 mnt_drop_write(path.mnt);
470 }
471 path_put(&path);
472 if (retry_estale(error, lookup_flags)) {
473 lookup_flags |= LOOKUP_REVAL;
474 goto retry;
475 }
476 return error;
477}
478
479SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
480 const char __user *, name, const void __user *, value,
481 size_t, size, int, flags)
482{
483 return path_setxattr(pathname, name, value, size, flags, LOOKUP_FOLLOW);
484}
485
486SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
487 const char __user *, name, const void __user *, value,
488 size_t, size, int, flags)
489{
490 return path_setxattr(pathname, name, value, size, flags, 0);
491}
492
493SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
494 const void __user *,value, size_t, size, int, flags)
495{
496 struct fd f = fdget(fd);
497 int error = -EBADF;
498
499 if (!f.file)
500 return error;
501 audit_file(f.file);
502 error = mnt_want_write_file(f.file);
503 if (!error) {
504 error = setxattr(f.file->f_path.dentry, name, value, size, flags);
505 mnt_drop_write_file(f.file);
506 }
507 fdput(f);
508 return error;
509}
510
511/*
512 * Extended attribute GET operations
513 */
514static ssize_t
515getxattr(struct dentry *d, const char __user *name, void __user *value,
516 size_t size)
517{
518 ssize_t error;
519 void *kvalue = NULL;
520 char kname[XATTR_NAME_MAX + 1];
521
522 error = strncpy_from_user(kname, name, sizeof(kname));
523 if (error == 0 || error == sizeof(kname))
524 error = -ERANGE;
525 if (error < 0)
526 return error;
527
528 if (size) {
529 if (size > XATTR_SIZE_MAX)
530 size = XATTR_SIZE_MAX;
531 kvalue = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
532 if (!kvalue) {
533 kvalue = vmalloc(size);
534 if (!kvalue)
535 return -ENOMEM;
536 }
537 }
538
539 error = vfs_getxattr(d, kname, kvalue, size);
540 if (error > 0) {
541 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
542 (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
543 posix_acl_fix_xattr_to_user(kvalue, size);
544 if (size && copy_to_user(value, kvalue, error))
545 error = -EFAULT;
546 } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
547 /* The file system tried to returned a value bigger
548 than XATTR_SIZE_MAX bytes. Not possible. */
549 error = -E2BIG;
550 }
551
552 kvfree(kvalue);
553
554 return error;
555}
556
557static ssize_t path_getxattr(const char __user *pathname,
558 const char __user *name, void __user *value,
559 size_t size, unsigned int lookup_flags)
560{
561 struct path path;
562 ssize_t error;
563retry:
564 error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
565 if (error)
566 return error;
567 error = getxattr(path.dentry, name, value, size);
568 path_put(&path);
569 if (retry_estale(error, lookup_flags)) {
570 lookup_flags |= LOOKUP_REVAL;
571 goto retry;
572 }
573 return error;
574}
575
576SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
577 const char __user *, name, void __user *, value, size_t, size)
578{
579 return path_getxattr(pathname, name, value, size, LOOKUP_FOLLOW);
580}
581
582SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
583 const char __user *, name, void __user *, value, size_t, size)
584{
585 return path_getxattr(pathname, name, value, size, 0);
586}
587
588SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
589 void __user *, value, size_t, size)
590{
591 struct fd f = fdget(fd);
592 ssize_t error = -EBADF;
593
594 if (!f.file)
595 return error;
596 audit_file(f.file);
597 error = getxattr(f.file->f_path.dentry, name, value, size);
598 fdput(f);
599 return error;
600}
601
602/*
603 * Extended attribute LIST operations
604 */
605static ssize_t
606listxattr(struct dentry *d, char __user *list, size_t size)
607{
608 ssize_t error;
609 char *klist = NULL;
610
611 if (size) {
612 if (size > XATTR_LIST_MAX)
613 size = XATTR_LIST_MAX;
614 klist = kmalloc(size, __GFP_NOWARN | GFP_KERNEL);
615 if (!klist) {
616 klist = vmalloc(size);
617 if (!klist)
618 return -ENOMEM;
619 }
620 }
621
622 error = vfs_listxattr(d, klist, size);
623 if (error > 0) {
624 if (size && copy_to_user(list, klist, error))
625 error = -EFAULT;
626 } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
627 /* The file system tried to returned a list bigger
628 than XATTR_LIST_MAX bytes. Not possible. */
629 error = -E2BIG;
630 }
631
632 kvfree(klist);
633
634 return error;
635}
636
637static ssize_t path_listxattr(const char __user *pathname, char __user *list,
638 size_t size, unsigned int lookup_flags)
639{
640 struct path path;
641 ssize_t error;
642retry:
643 error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
644 if (error)
645 return error;
646 error = listxattr(path.dentry, list, size);
647 path_put(&path);
648 if (retry_estale(error, lookup_flags)) {
649 lookup_flags |= LOOKUP_REVAL;
650 goto retry;
651 }
652 return error;
653}
654
655SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
656 size_t, size)
657{
658 return path_listxattr(pathname, list, size, LOOKUP_FOLLOW);
659}
660
661SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
662 size_t, size)
663{
664 return path_listxattr(pathname, list, size, 0);
665}
666
667SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
668{
669 struct fd f = fdget(fd);
670 ssize_t error = -EBADF;
671
672 if (!f.file)
673 return error;
674 audit_file(f.file);
675 error = listxattr(f.file->f_path.dentry, list, size);
676 fdput(f);
677 return error;
678}
679
680/*
681 * Extended attribute REMOVE operations
682 */
683static long
684removexattr(struct dentry *d, const char __user *name)
685{
686 int error;
687 char kname[XATTR_NAME_MAX + 1];
688
689 error = strncpy_from_user(kname, name, sizeof(kname));
690 if (error == 0 || error == sizeof(kname))
691 error = -ERANGE;
692 if (error < 0)
693 return error;
694
695 return vfs_removexattr(d, kname);
696}
697
698static int path_removexattr(const char __user *pathname,
699 const char __user *name, unsigned int lookup_flags)
700{
701 struct path path;
702 int error;
703retry:
704 error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
705 if (error)
706 return error;
707 error = mnt_want_write(path.mnt);
708 if (!error) {
709 error = removexattr(path.dentry, name);
710 mnt_drop_write(path.mnt);
711 }
712 path_put(&path);
713 if (retry_estale(error, lookup_flags)) {
714 lookup_flags |= LOOKUP_REVAL;
715 goto retry;
716 }
717 return error;
718}
719
720SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
721 const char __user *, name)
722{
723 return path_removexattr(pathname, name, LOOKUP_FOLLOW);
724}
725
726SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
727 const char __user *, name)
728{
729 return path_removexattr(pathname, name, 0);
730}
731
732SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
733{
734 struct fd f = fdget(fd);
735 int error = -EBADF;
736
737 if (!f.file)
738 return error;
739 audit_file(f.file);
740 error = mnt_want_write_file(f.file);
741 if (!error) {
742 error = removexattr(f.file->f_path.dentry, name);
743 mnt_drop_write_file(f.file);
744 }
745 fdput(f);
746 return error;
747}
748
749/*
750 * Combine the results of the list() operation from every xattr_handler in the
751 * list.
752 */
753ssize_t
754generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
755{
756 const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
757 unsigned int size = 0;
758
759 if (!buffer) {
760 for_each_xattr_handler(handlers, handler) {
761 if (!handler->name ||
762 (handler->list && !handler->list(dentry)))
763 continue;
764 size += strlen(handler->name) + 1;
765 }
766 } else {
767 char *buf = buffer;
768 size_t len;
769
770 for_each_xattr_handler(handlers, handler) {
771 if (!handler->name ||
772 (handler->list && !handler->list(dentry)))
773 continue;
774 len = strlen(handler->name);
775 if (len + 1 > buffer_size)
776 return -ERANGE;
777 memcpy(buf, handler->name, len + 1);
778 buf += len + 1;
779 buffer_size -= len + 1;
780 }
781 size = buf - buffer;
782 }
783 return size;
784}
785EXPORT_SYMBOL(generic_listxattr);
786
787/**
788 * xattr_full_name - Compute full attribute name from suffix
789 *
790 * @handler: handler of the xattr_handler operation
791 * @name: name passed to the xattr_handler operation
792 *
793 * The get and set xattr handler operations are called with the remainder of
794 * the attribute name after skipping the handler's prefix: for example, "foo"
795 * is passed to the get operation of a handler with prefix "user." to get
796 * attribute "user.foo". The full name is still "there" in the name though.
797 *
798 * Note: the list xattr handler operation when called from the vfs is passed a
799 * NULL name; some file systems use this operation internally, with varying
800 * semantics.
801 */
802const char *xattr_full_name(const struct xattr_handler *handler,
803 const char *name)
804{
805 size_t prefix_len = strlen(xattr_prefix(handler));
806
807 return name - prefix_len;
808}
809EXPORT_SYMBOL(xattr_full_name);
810
811/*
812 * Allocate new xattr and copy in the value; but leave the name to callers.
813 */
814struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
815{
816 struct simple_xattr *new_xattr;
817 size_t len;
818
819 /* wrap around? */
820 len = sizeof(*new_xattr) + size;
821 if (len < sizeof(*new_xattr))
822 return NULL;
823
824 new_xattr = kmalloc(len, GFP_KERNEL);
825 if (!new_xattr)
826 return NULL;
827
828 new_xattr->size = size;
829 memcpy(new_xattr->value, value, size);
830 return new_xattr;
831}
832
833/*
834 * xattr GET operation for in-memory/pseudo filesystems
835 */
836int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
837 void *buffer, size_t size)
838{
839 struct simple_xattr *xattr;
840 int ret = -ENODATA;
841
842 spin_lock(&xattrs->lock);
843 list_for_each_entry(xattr, &xattrs->head, list) {
844 if (strcmp(name, xattr->name))
845 continue;
846
847 ret = xattr->size;
848 if (buffer) {
849 if (size < xattr->size)
850 ret = -ERANGE;
851 else
852 memcpy(buffer, xattr->value, xattr->size);
853 }
854 break;
855 }
856 spin_unlock(&xattrs->lock);
857 return ret;
858}
859
860/**
861 * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
862 * @xattrs: target simple_xattr list
863 * @name: name of the extended attribute
864 * @value: value of the xattr. If %NULL, will remove the attribute.
865 * @size: size of the new xattr
866 * @flags: %XATTR_{CREATE|REPLACE}
867 *
868 * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
869 * with -EEXIST. If %XATTR_REPLACE is set, the xattr should exist;
870 * otherwise, fails with -ENODATA.
871 *
872 * Returns 0 on success, -errno on failure.
873 */
874int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
875 const void *value, size_t size, int flags)
876{
877 struct simple_xattr *xattr;
878 struct simple_xattr *new_xattr = NULL;
879 int err = 0;
880
881 /* value == NULL means remove */
882 if (value) {
883 new_xattr = simple_xattr_alloc(value, size);
884 if (!new_xattr)
885 return -ENOMEM;
886
887 new_xattr->name = kstrdup(name, GFP_KERNEL);
888 if (!new_xattr->name) {
889 kfree(new_xattr);
890 return -ENOMEM;
891 }
892 }
893
894 spin_lock(&xattrs->lock);
895 list_for_each_entry(xattr, &xattrs->head, list) {
896 if (!strcmp(name, xattr->name)) {
897 if (flags & XATTR_CREATE) {
898 xattr = new_xattr;
899 err = -EEXIST;
900 } else if (new_xattr) {
901 list_replace(&xattr->list, &new_xattr->list);
902 } else {
903 list_del(&xattr->list);
904 }
905 goto out;
906 }
907 }
908 if (flags & XATTR_REPLACE) {
909 xattr = new_xattr;
910 err = -ENODATA;
911 } else {
912 list_add(&new_xattr->list, &xattrs->head);
913 xattr = NULL;
914 }
915out:
916 spin_unlock(&xattrs->lock);
917 if (xattr) {
918 kfree(xattr->name);
919 kfree(xattr);
920 }
921 return err;
922
923}
924
925static bool xattr_is_trusted(const char *name)
926{
927 return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
928}
929
930static int xattr_list_one(char **buffer, ssize_t *remaining_size,
931 const char *name)
932{
933 size_t len = strlen(name) + 1;
934 if (*buffer) {
935 if (*remaining_size < len)
936 return -ERANGE;
937 memcpy(*buffer, name, len);
938 *buffer += len;
939 }
940 *remaining_size -= len;
941 return 0;
942}
943
944/*
945 * xattr LIST operation for in-memory/pseudo filesystems
946 */
947ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,
948 char *buffer, size_t size)
949{
950 bool trusted = capable(CAP_SYS_ADMIN);
951 struct simple_xattr *xattr;
952 ssize_t remaining_size = size;
953 int err = 0;
954
955#ifdef CONFIG_FS_POSIX_ACL
956 if (inode->i_acl) {
957 err = xattr_list_one(&buffer, &remaining_size,
958 XATTR_NAME_POSIX_ACL_ACCESS);
959 if (err)
960 return err;
961 }
962 if (inode->i_default_acl) {
963 err = xattr_list_one(&buffer, &remaining_size,
964 XATTR_NAME_POSIX_ACL_DEFAULT);
965 if (err)
966 return err;
967 }
968#endif
969
970 spin_lock(&xattrs->lock);
971 list_for_each_entry(xattr, &xattrs->head, list) {
972 /* skip "trusted." attributes for unprivileged callers */
973 if (!trusted && xattr_is_trusted(xattr->name))
974 continue;
975
976 err = xattr_list_one(&buffer, &remaining_size, xattr->name);
977 if (err)
978 break;
979 }
980 spin_unlock(&xattrs->lock);
981
982 return err ? err : size - remaining_size;
983}
984
985/*
986 * Adds an extended attribute to the list
987 */
988void simple_xattr_list_add(struct simple_xattrs *xattrs,
989 struct simple_xattr *new_xattr)
990{
991 spin_lock(&xattrs->lock);
992 list_add(&new_xattr->list, &xattrs->head);
993 spin_unlock(&xattrs->lock);
994}
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/mount.h>
15#include <linux/namei.h>
16#include <linux/security.h>
17#include <linux/evm.h>
18#include <linux/syscalls.h>
19#include <linux/export.h>
20#include <linux/fsnotify.h>
21#include <linux/audit.h>
22#include <linux/vmalloc.h>
23
24#include <asm/uaccess.h>
25
26/*
27 * Check permissions for extended attribute access. This is a bit complicated
28 * because different namespaces have very different rules.
29 */
30static int
31xattr_permission(struct inode *inode, const char *name, int mask)
32{
33 /*
34 * We can never set or remove an extended attribute on a read-only
35 * filesystem or on an immutable / append-only inode.
36 */
37 if (mask & MAY_WRITE) {
38 if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
39 return -EPERM;
40 }
41
42 /*
43 * No restriction for security.* and system.* from the VFS. Decision
44 * on these is left to the underlying filesystem / security module.
45 */
46 if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
47 !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
48 return 0;
49
50 /*
51 * The trusted.* namespace can only be accessed by privileged users.
52 */
53 if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
54 if (!capable(CAP_SYS_ADMIN))
55 return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
56 return 0;
57 }
58
59 /*
60 * In the user.* namespace, only regular files and directories can have
61 * extended attributes. For sticky directories, only the owner and
62 * privileged users can write attributes.
63 */
64 if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
65 if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
66 return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
67 if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&
68 (mask & MAY_WRITE) && !inode_owner_or_capable(inode))
69 return -EPERM;
70 }
71
72 return inode_permission(inode, mask);
73}
74
75/**
76 * __vfs_setxattr_noperm - perform setxattr operation without performing
77 * permission checks.
78 *
79 * @dentry - object to perform setxattr on
80 * @name - xattr name to set
81 * @value - value to set @name to
82 * @size - size of @value
83 * @flags - flags to pass into filesystem operations
84 *
85 * returns the result of the internal setxattr or setsecurity operations.
86 *
87 * This function requires the caller to lock the inode's i_mutex before it
88 * is executed. It also assumes that the caller will make the appropriate
89 * permission checks.
90 */
91int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
92 const void *value, size_t size, int flags)
93{
94 struct inode *inode = dentry->d_inode;
95 int error = -EOPNOTSUPP;
96 int issec = !strncmp(name, XATTR_SECURITY_PREFIX,
97 XATTR_SECURITY_PREFIX_LEN);
98
99 if (issec)
100 inode->i_flags &= ~S_NOSEC;
101 if (inode->i_op->setxattr) {
102 error = inode->i_op->setxattr(dentry, name, value, size, flags);
103 if (!error) {
104 fsnotify_xattr(dentry);
105 security_inode_post_setxattr(dentry, name, value,
106 size, flags);
107 }
108 } else if (issec) {
109 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
110 error = security_inode_setsecurity(inode, suffix, value,
111 size, flags);
112 if (!error)
113 fsnotify_xattr(dentry);
114 }
115
116 return error;
117}
118
119
120int
121vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
122 size_t size, int flags)
123{
124 struct inode *inode = dentry->d_inode;
125 int error;
126
127 error = xattr_permission(inode, name, MAY_WRITE);
128 if (error)
129 return error;
130
131 mutex_lock(&inode->i_mutex);
132 error = security_inode_setxattr(dentry, name, value, size, flags);
133 if (error)
134 goto out;
135
136 error = __vfs_setxattr_noperm(dentry, name, value, size, flags);
137
138out:
139 mutex_unlock(&inode->i_mutex);
140 return error;
141}
142EXPORT_SYMBOL_GPL(vfs_setxattr);
143
144ssize_t
145xattr_getsecurity(struct inode *inode, const char *name, void *value,
146 size_t size)
147{
148 void *buffer = NULL;
149 ssize_t len;
150
151 if (!value || !size) {
152 len = security_inode_getsecurity(inode, name, &buffer, false);
153 goto out_noalloc;
154 }
155
156 len = security_inode_getsecurity(inode, name, &buffer, true);
157 if (len < 0)
158 return len;
159 if (size < len) {
160 len = -ERANGE;
161 goto out;
162 }
163 memcpy(value, buffer, len);
164out:
165 security_release_secctx(buffer, len);
166out_noalloc:
167 return len;
168}
169EXPORT_SYMBOL_GPL(xattr_getsecurity);
170
171/*
172 * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
173 *
174 * Allocate memory, if not already allocated, or re-allocate correct size,
175 * before retrieving the extended attribute.
176 *
177 * Returns the result of alloc, if failed, or the getxattr operation.
178 */
179ssize_t
180vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value,
181 size_t xattr_size, gfp_t flags)
182{
183 struct inode *inode = dentry->d_inode;
184 char *value = *xattr_value;
185 int error;
186
187 error = xattr_permission(inode, name, MAY_READ);
188 if (error)
189 return error;
190
191 if (!inode->i_op->getxattr)
192 return -EOPNOTSUPP;
193
194 error = inode->i_op->getxattr(dentry, name, NULL, 0);
195 if (error < 0)
196 return error;
197
198 if (!value || (error > xattr_size)) {
199 value = krealloc(*xattr_value, error + 1, flags);
200 if (!value)
201 return -ENOMEM;
202 memset(value, 0, error + 1);
203 }
204
205 error = inode->i_op->getxattr(dentry, name, value, error);
206 *xattr_value = value;
207 return error;
208}
209
210/* Compare an extended attribute value with the given value */
211int vfs_xattr_cmp(struct dentry *dentry, const char *xattr_name,
212 const char *value, size_t size, gfp_t flags)
213{
214 char *xattr_value = NULL;
215 int rc;
216
217 rc = vfs_getxattr_alloc(dentry, xattr_name, &xattr_value, 0, flags);
218 if (rc < 0)
219 return rc;
220
221 if ((rc != size) || (memcmp(xattr_value, value, rc) != 0))
222 rc = -EINVAL;
223 else
224 rc = 0;
225 kfree(xattr_value);
226 return rc;
227}
228
229ssize_t
230vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
231{
232 struct inode *inode = dentry->d_inode;
233 int error;
234
235 error = xattr_permission(inode, name, MAY_READ);
236 if (error)
237 return error;
238
239 error = security_inode_getxattr(dentry, name);
240 if (error)
241 return error;
242
243 if (!strncmp(name, XATTR_SECURITY_PREFIX,
244 XATTR_SECURITY_PREFIX_LEN)) {
245 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
246 int ret = xattr_getsecurity(inode, suffix, value, size);
247 /*
248 * Only overwrite the return value if a security module
249 * is actually active.
250 */
251 if (ret == -EOPNOTSUPP)
252 goto nolsm;
253 return ret;
254 }
255nolsm:
256 if (inode->i_op->getxattr)
257 error = inode->i_op->getxattr(dentry, name, value, size);
258 else
259 error = -EOPNOTSUPP;
260
261 return error;
262}
263EXPORT_SYMBOL_GPL(vfs_getxattr);
264
265ssize_t
266vfs_listxattr(struct dentry *d, char *list, size_t size)
267{
268 ssize_t error;
269
270 error = security_inode_listxattr(d);
271 if (error)
272 return error;
273 error = -EOPNOTSUPP;
274 if (d->d_inode->i_op->listxattr) {
275 error = d->d_inode->i_op->listxattr(d, list, size);
276 } else {
277 error = security_inode_listsecurity(d->d_inode, list, size);
278 if (size && error > size)
279 error = -ERANGE;
280 }
281 return error;
282}
283EXPORT_SYMBOL_GPL(vfs_listxattr);
284
285int
286vfs_removexattr(struct dentry *dentry, const char *name)
287{
288 struct inode *inode = dentry->d_inode;
289 int error;
290
291 if (!inode->i_op->removexattr)
292 return -EOPNOTSUPP;
293
294 error = xattr_permission(inode, name, MAY_WRITE);
295 if (error)
296 return error;
297
298 error = security_inode_removexattr(dentry, name);
299 if (error)
300 return error;
301
302 mutex_lock(&inode->i_mutex);
303 error = inode->i_op->removexattr(dentry, name);
304 mutex_unlock(&inode->i_mutex);
305
306 if (!error) {
307 fsnotify_xattr(dentry);
308 evm_inode_post_removexattr(dentry, name);
309 }
310 return error;
311}
312EXPORT_SYMBOL_GPL(vfs_removexattr);
313
314
315/*
316 * Extended attribute SET operations
317 */
318static long
319setxattr(struct dentry *d, const char __user *name, const void __user *value,
320 size_t size, int flags)
321{
322 int error;
323 void *kvalue = NULL;
324 void *vvalue = NULL; /* If non-NULL, we used vmalloc() */
325 char kname[XATTR_NAME_MAX + 1];
326
327 if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
328 return -EINVAL;
329
330 error = strncpy_from_user(kname, name, sizeof(kname));
331 if (error == 0 || error == sizeof(kname))
332 error = -ERANGE;
333 if (error < 0)
334 return error;
335
336 if (size) {
337 if (size > XATTR_SIZE_MAX)
338 return -E2BIG;
339 kvalue = kmalloc(size, GFP_KERNEL | __GFP_NOWARN);
340 if (!kvalue) {
341 vvalue = vmalloc(size);
342 if (!vvalue)
343 return -ENOMEM;
344 kvalue = vvalue;
345 }
346 if (copy_from_user(kvalue, value, size)) {
347 error = -EFAULT;
348 goto out;
349 }
350 }
351
352 error = vfs_setxattr(d, kname, kvalue, size, flags);
353out:
354 if (vvalue)
355 vfree(vvalue);
356 else
357 kfree(kvalue);
358 return error;
359}
360
361SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
362 const char __user *, name, const void __user *, value,
363 size_t, size, int, flags)
364{
365 struct path path;
366 int error;
367
368 error = user_path(pathname, &path);
369 if (error)
370 return error;
371 error = mnt_want_write(path.mnt);
372 if (!error) {
373 error = setxattr(path.dentry, name, value, size, flags);
374 mnt_drop_write(path.mnt);
375 }
376 path_put(&path);
377 return error;
378}
379
380SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
381 const char __user *, name, const void __user *, value,
382 size_t, size, int, flags)
383{
384 struct path path;
385 int error;
386
387 error = user_lpath(pathname, &path);
388 if (error)
389 return error;
390 error = mnt_want_write(path.mnt);
391 if (!error) {
392 error = setxattr(path.dentry, name, value, size, flags);
393 mnt_drop_write(path.mnt);
394 }
395 path_put(&path);
396 return error;
397}
398
399SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
400 const void __user *,value, size_t, size, int, flags)
401{
402 int fput_needed;
403 struct file *f;
404 struct dentry *dentry;
405 int error = -EBADF;
406
407 f = fget_light(fd, &fput_needed);
408 if (!f)
409 return error;
410 dentry = f->f_path.dentry;
411 audit_inode(NULL, dentry);
412 error = mnt_want_write_file(f);
413 if (!error) {
414 error = setxattr(dentry, name, value, size, flags);
415 mnt_drop_write_file(f);
416 }
417 fput_light(f, fput_needed);
418 return error;
419}
420
421/*
422 * Extended attribute GET operations
423 */
424static ssize_t
425getxattr(struct dentry *d, const char __user *name, void __user *value,
426 size_t size)
427{
428 ssize_t error;
429 void *kvalue = NULL;
430 char kname[XATTR_NAME_MAX + 1];
431
432 error = strncpy_from_user(kname, name, sizeof(kname));
433 if (error == 0 || error == sizeof(kname))
434 error = -ERANGE;
435 if (error < 0)
436 return error;
437
438 if (size) {
439 if (size > XATTR_SIZE_MAX)
440 size = XATTR_SIZE_MAX;
441 kvalue = kzalloc(size, GFP_KERNEL);
442 if (!kvalue)
443 return -ENOMEM;
444 }
445
446 error = vfs_getxattr(d, kname, kvalue, size);
447 if (error > 0) {
448 if (size && copy_to_user(value, kvalue, error))
449 error = -EFAULT;
450 } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
451 /* The file system tried to returned a value bigger
452 than XATTR_SIZE_MAX bytes. Not possible. */
453 error = -E2BIG;
454 }
455 kfree(kvalue);
456 return error;
457}
458
459SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
460 const char __user *, name, void __user *, value, size_t, size)
461{
462 struct path path;
463 ssize_t error;
464
465 error = user_path(pathname, &path);
466 if (error)
467 return error;
468 error = getxattr(path.dentry, name, value, size);
469 path_put(&path);
470 return error;
471}
472
473SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
474 const char __user *, name, void __user *, value, size_t, size)
475{
476 struct path path;
477 ssize_t error;
478
479 error = user_lpath(pathname, &path);
480 if (error)
481 return error;
482 error = getxattr(path.dentry, name, value, size);
483 path_put(&path);
484 return error;
485}
486
487SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
488 void __user *, value, size_t, size)
489{
490 int fput_needed;
491 struct file *f;
492 ssize_t error = -EBADF;
493
494 f = fget_light(fd, &fput_needed);
495 if (!f)
496 return error;
497 audit_inode(NULL, f->f_path.dentry);
498 error = getxattr(f->f_path.dentry, name, value, size);
499 fput_light(f, fput_needed);
500 return error;
501}
502
503/*
504 * Extended attribute LIST operations
505 */
506static ssize_t
507listxattr(struct dentry *d, char __user *list, size_t size)
508{
509 ssize_t error;
510 char *klist = NULL;
511 char *vlist = NULL; /* If non-NULL, we used vmalloc() */
512
513 if (size) {
514 if (size > XATTR_LIST_MAX)
515 size = XATTR_LIST_MAX;
516 klist = kmalloc(size, __GFP_NOWARN | GFP_KERNEL);
517 if (!klist) {
518 vlist = vmalloc(size);
519 if (!vlist)
520 return -ENOMEM;
521 klist = vlist;
522 }
523 }
524
525 error = vfs_listxattr(d, klist, size);
526 if (error > 0) {
527 if (size && copy_to_user(list, klist, error))
528 error = -EFAULT;
529 } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
530 /* The file system tried to returned a list bigger
531 than XATTR_LIST_MAX bytes. Not possible. */
532 error = -E2BIG;
533 }
534 if (vlist)
535 vfree(vlist);
536 else
537 kfree(klist);
538 return error;
539}
540
541SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
542 size_t, size)
543{
544 struct path path;
545 ssize_t error;
546
547 error = user_path(pathname, &path);
548 if (error)
549 return error;
550 error = listxattr(path.dentry, list, size);
551 path_put(&path);
552 return error;
553}
554
555SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
556 size_t, size)
557{
558 struct path path;
559 ssize_t error;
560
561 error = user_lpath(pathname, &path);
562 if (error)
563 return error;
564 error = listxattr(path.dentry, list, size);
565 path_put(&path);
566 return error;
567}
568
569SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
570{
571 int fput_needed;
572 struct file *f;
573 ssize_t error = -EBADF;
574
575 f = fget_light(fd, &fput_needed);
576 if (!f)
577 return error;
578 audit_inode(NULL, f->f_path.dentry);
579 error = listxattr(f->f_path.dentry, list, size);
580 fput_light(f, fput_needed);
581 return error;
582}
583
584/*
585 * Extended attribute REMOVE operations
586 */
587static long
588removexattr(struct dentry *d, const char __user *name)
589{
590 int error;
591 char kname[XATTR_NAME_MAX + 1];
592
593 error = strncpy_from_user(kname, name, sizeof(kname));
594 if (error == 0 || error == sizeof(kname))
595 error = -ERANGE;
596 if (error < 0)
597 return error;
598
599 return vfs_removexattr(d, kname);
600}
601
602SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
603 const char __user *, name)
604{
605 struct path path;
606 int error;
607
608 error = user_path(pathname, &path);
609 if (error)
610 return error;
611 error = mnt_want_write(path.mnt);
612 if (!error) {
613 error = removexattr(path.dentry, name);
614 mnt_drop_write(path.mnt);
615 }
616 path_put(&path);
617 return error;
618}
619
620SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
621 const char __user *, name)
622{
623 struct path path;
624 int error;
625
626 error = user_lpath(pathname, &path);
627 if (error)
628 return error;
629 error = mnt_want_write(path.mnt);
630 if (!error) {
631 error = removexattr(path.dentry, name);
632 mnt_drop_write(path.mnt);
633 }
634 path_put(&path);
635 return error;
636}
637
638SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
639{
640 int fput_needed;
641 struct file *f;
642 struct dentry *dentry;
643 int error = -EBADF;
644
645 f = fget_light(fd, &fput_needed);
646 if (!f)
647 return error;
648 dentry = f->f_path.dentry;
649 audit_inode(NULL, dentry);
650 error = mnt_want_write_file(f);
651 if (!error) {
652 error = removexattr(dentry, name);
653 mnt_drop_write_file(f);
654 }
655 fput_light(f, fput_needed);
656 return error;
657}
658
659
660static const char *
661strcmp_prefix(const char *a, const char *a_prefix)
662{
663 while (*a_prefix && *a == *a_prefix) {
664 a++;
665 a_prefix++;
666 }
667 return *a_prefix ? NULL : a;
668}
669
670/*
671 * In order to implement different sets of xattr operations for each xattr
672 * prefix with the generic xattr API, a filesystem should create a
673 * null-terminated array of struct xattr_handler (one for each prefix) and
674 * hang a pointer to it off of the s_xattr field of the superblock.
675 *
676 * The generic_fooxattr() functions will use this list to dispatch xattr
677 * operations to the correct xattr_handler.
678 */
679#define for_each_xattr_handler(handlers, handler) \
680 for ((handler) = *(handlers)++; \
681 (handler) != NULL; \
682 (handler) = *(handlers)++)
683
684/*
685 * Find the xattr_handler with the matching prefix.
686 */
687static const struct xattr_handler *
688xattr_resolve_name(const struct xattr_handler **handlers, const char **name)
689{
690 const struct xattr_handler *handler;
691
692 if (!*name)
693 return NULL;
694
695 for_each_xattr_handler(handlers, handler) {
696 const char *n = strcmp_prefix(*name, handler->prefix);
697 if (n) {
698 *name = n;
699 break;
700 }
701 }
702 return handler;
703}
704
705/*
706 * Find the handler for the prefix and dispatch its get() operation.
707 */
708ssize_t
709generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size)
710{
711 const struct xattr_handler *handler;
712
713 handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
714 if (!handler)
715 return -EOPNOTSUPP;
716 return handler->get(dentry, name, buffer, size, handler->flags);
717}
718
719/*
720 * Combine the results of the list() operation from every xattr_handler in the
721 * list.
722 */
723ssize_t
724generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
725{
726 const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
727 unsigned int size = 0;
728
729 if (!buffer) {
730 for_each_xattr_handler(handlers, handler) {
731 size += handler->list(dentry, NULL, 0, NULL, 0,
732 handler->flags);
733 }
734 } else {
735 char *buf = buffer;
736
737 for_each_xattr_handler(handlers, handler) {
738 size = handler->list(dentry, buf, buffer_size,
739 NULL, 0, handler->flags);
740 if (size > buffer_size)
741 return -ERANGE;
742 buf += size;
743 buffer_size -= size;
744 }
745 size = buf - buffer;
746 }
747 return size;
748}
749
750/*
751 * Find the handler for the prefix and dispatch its set() operation.
752 */
753int
754generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags)
755{
756 const struct xattr_handler *handler;
757
758 if (size == 0)
759 value = ""; /* empty EA, do not remove */
760 handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
761 if (!handler)
762 return -EOPNOTSUPP;
763 return handler->set(dentry, name, value, size, flags, handler->flags);
764}
765
766/*
767 * Find the handler for the prefix and dispatch its set() operation to remove
768 * any associated extended attribute.
769 */
770int
771generic_removexattr(struct dentry *dentry, const char *name)
772{
773 const struct xattr_handler *handler;
774
775 handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
776 if (!handler)
777 return -EOPNOTSUPP;
778 return handler->set(dentry, name, NULL, 0,
779 XATTR_REPLACE, handler->flags);
780}
781
782EXPORT_SYMBOL(generic_getxattr);
783EXPORT_SYMBOL(generic_listxattr);
784EXPORT_SYMBOL(generic_setxattr);
785EXPORT_SYMBOL(generic_removexattr);