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