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