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#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#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 mutex_lock(&inode->i_mutex);
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 mutex_unlock(&inode->i_mutex);
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
211/* Compare an extended attribute value with the given value */
212int vfs_xattr_cmp(struct dentry *dentry, const char *xattr_name,
213 const char *value, size_t size, gfp_t flags)
214{
215 char *xattr_value = NULL;
216 int rc;
217
218 rc = vfs_getxattr_alloc(dentry, xattr_name, &xattr_value, 0, flags);
219 if (rc < 0)
220 return rc;
221
222 if ((rc != size) || (memcmp(xattr_value, value, rc) != 0))
223 rc = -EINVAL;
224 else
225 rc = 0;
226 kfree(xattr_value);
227 return rc;
228}
229
230ssize_t
231vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
232{
233 struct inode *inode = dentry->d_inode;
234 int error;
235
236 error = xattr_permission(inode, name, MAY_READ);
237 if (error)
238 return error;
239
240 error = security_inode_getxattr(dentry, name);
241 if (error)
242 return error;
243
244 if (!strncmp(name, XATTR_SECURITY_PREFIX,
245 XATTR_SECURITY_PREFIX_LEN)) {
246 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
247 int ret = xattr_getsecurity(inode, suffix, value, size);
248 /*
249 * Only overwrite the return value if a security module
250 * is actually active.
251 */
252 if (ret == -EOPNOTSUPP)
253 goto nolsm;
254 return ret;
255 }
256nolsm:
257 if (inode->i_op->getxattr)
258 error = inode->i_op->getxattr(dentry, name, value, size);
259 else
260 error = -EOPNOTSUPP;
261
262 return error;
263}
264EXPORT_SYMBOL_GPL(vfs_getxattr);
265
266ssize_t
267vfs_listxattr(struct dentry *d, char *list, size_t size)
268{
269 ssize_t error;
270
271 error = security_inode_listxattr(d);
272 if (error)
273 return error;
274 error = -EOPNOTSUPP;
275 if (d->d_inode->i_op->listxattr) {
276 error = d->d_inode->i_op->listxattr(d, list, size);
277 } else {
278 error = security_inode_listsecurity(d->d_inode, list, size);
279 if (size && error > size)
280 error = -ERANGE;
281 }
282 return error;
283}
284EXPORT_SYMBOL_GPL(vfs_listxattr);
285
286int
287vfs_removexattr(struct dentry *dentry, const char *name)
288{
289 struct inode *inode = dentry->d_inode;
290 int error;
291
292 if (!inode->i_op->removexattr)
293 return -EOPNOTSUPP;
294
295 error = xattr_permission(inode, name, MAY_WRITE);
296 if (error)
297 return error;
298
299 mutex_lock(&inode->i_mutex);
300 error = security_inode_removexattr(dentry, name);
301 if (error) {
302 mutex_unlock(&inode->i_mutex);
303 return error;
304 }
305
306 error = inode->i_op->removexattr(dentry, name);
307 mutex_unlock(&inode->i_mutex);
308
309 if (!error) {
310 fsnotify_xattr(dentry);
311 evm_inode_post_removexattr(dentry, name);
312 }
313 return error;
314}
315EXPORT_SYMBOL_GPL(vfs_removexattr);
316
317
318/*
319 * Extended attribute SET operations
320 */
321static long
322setxattr(struct dentry *d, const char __user *name, const void __user *value,
323 size_t size, int flags)
324{
325 int error;
326 void *kvalue = NULL;
327 void *vvalue = NULL; /* If non-NULL, we used vmalloc() */
328 char kname[XATTR_NAME_MAX + 1];
329
330 if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
331 return -EINVAL;
332
333 error = strncpy_from_user(kname, name, sizeof(kname));
334 if (error == 0 || error == sizeof(kname))
335 error = -ERANGE;
336 if (error < 0)
337 return error;
338
339 if (size) {
340 if (size > XATTR_SIZE_MAX)
341 return -E2BIG;
342 kvalue = kmalloc(size, GFP_KERNEL | __GFP_NOWARN);
343 if (!kvalue) {
344 vvalue = vmalloc(size);
345 if (!vvalue)
346 return -ENOMEM;
347 kvalue = vvalue;
348 }
349 if (copy_from_user(kvalue, value, size)) {
350 error = -EFAULT;
351 goto out;
352 }
353 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
354 (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
355 posix_acl_fix_xattr_from_user(kvalue, size);
356 }
357
358 error = vfs_setxattr(d, kname, kvalue, size, flags);
359out:
360 if (vvalue)
361 vfree(vvalue);
362 else
363 kfree(kvalue);
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 struct path path;
372 int error;
373 unsigned int lookup_flags = LOOKUP_FOLLOW;
374retry:
375 error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
376 if (error)
377 return error;
378 error = mnt_want_write(path.mnt);
379 if (!error) {
380 error = setxattr(path.dentry, name, value, size, flags);
381 mnt_drop_write(path.mnt);
382 }
383 path_put(&path);
384 if (retry_estale(error, lookup_flags)) {
385 lookup_flags |= LOOKUP_REVAL;
386 goto retry;
387 }
388 return error;
389}
390
391SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
392 const char __user *, name, const void __user *, value,
393 size_t, size, int, flags)
394{
395 struct path path;
396 int error;
397 unsigned int lookup_flags = 0;
398retry:
399 error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
400 if (error)
401 return error;
402 error = mnt_want_write(path.mnt);
403 if (!error) {
404 error = setxattr(path.dentry, name, value, size, flags);
405 mnt_drop_write(path.mnt);
406 }
407 path_put(&path);
408 if (retry_estale(error, lookup_flags)) {
409 lookup_flags |= LOOKUP_REVAL;
410 goto retry;
411 }
412 return error;
413}
414
415SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
416 const void __user *,value, size_t, size, int, flags)
417{
418 struct fd f = fdget(fd);
419 struct dentry *dentry;
420 int error = -EBADF;
421
422 if (!f.file)
423 return error;
424 dentry = f.file->f_path.dentry;
425 audit_inode(NULL, dentry, 0);
426 error = mnt_want_write_file(f.file);
427 if (!error) {
428 error = setxattr(dentry, name, value, size, flags);
429 mnt_drop_write_file(f.file);
430 }
431 fdput(f);
432 return error;
433}
434
435/*
436 * Extended attribute GET operations
437 */
438static ssize_t
439getxattr(struct dentry *d, const char __user *name, void __user *value,
440 size_t size)
441{
442 ssize_t error;
443 void *kvalue = NULL;
444 void *vvalue = NULL;
445 char kname[XATTR_NAME_MAX + 1];
446
447 error = strncpy_from_user(kname, name, sizeof(kname));
448 if (error == 0 || error == sizeof(kname))
449 error = -ERANGE;
450 if (error < 0)
451 return error;
452
453 if (size) {
454 if (size > XATTR_SIZE_MAX)
455 size = XATTR_SIZE_MAX;
456 kvalue = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
457 if (!kvalue) {
458 vvalue = vmalloc(size);
459 if (!vvalue)
460 return -ENOMEM;
461 kvalue = vvalue;
462 }
463 }
464
465 error = vfs_getxattr(d, kname, kvalue, size);
466 if (error > 0) {
467 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
468 (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
469 posix_acl_fix_xattr_to_user(kvalue, size);
470 if (size && copy_to_user(value, kvalue, error))
471 error = -EFAULT;
472 } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
473 /* The file system tried to returned a value bigger
474 than XATTR_SIZE_MAX bytes. Not possible. */
475 error = -E2BIG;
476 }
477 if (vvalue)
478 vfree(vvalue);
479 else
480 kfree(kvalue);
481 return error;
482}
483
484SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
485 const char __user *, name, void __user *, value, size_t, size)
486{
487 struct path path;
488 ssize_t error;
489 unsigned int lookup_flags = LOOKUP_FOLLOW;
490retry:
491 error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
492 if (error)
493 return error;
494 error = getxattr(path.dentry, name, value, size);
495 path_put(&path);
496 if (retry_estale(error, lookup_flags)) {
497 lookup_flags |= LOOKUP_REVAL;
498 goto retry;
499 }
500 return error;
501}
502
503SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
504 const char __user *, name, void __user *, value, size_t, size)
505{
506 struct path path;
507 ssize_t error;
508 unsigned int lookup_flags = 0;
509retry:
510 error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
511 if (error)
512 return error;
513 error = getxattr(path.dentry, name, value, size);
514 path_put(&path);
515 if (retry_estale(error, lookup_flags)) {
516 lookup_flags |= LOOKUP_REVAL;
517 goto retry;
518 }
519 return error;
520}
521
522SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
523 void __user *, value, size_t, size)
524{
525 struct fd f = fdget(fd);
526 ssize_t error = -EBADF;
527
528 if (!f.file)
529 return error;
530 audit_inode(NULL, f.file->f_path.dentry, 0);
531 error = getxattr(f.file->f_path.dentry, name, value, size);
532 fdput(f);
533 return error;
534}
535
536/*
537 * Extended attribute LIST operations
538 */
539static ssize_t
540listxattr(struct dentry *d, char __user *list, size_t size)
541{
542 ssize_t error;
543 char *klist = NULL;
544 char *vlist = NULL; /* If non-NULL, we used vmalloc() */
545
546 if (size) {
547 if (size > XATTR_LIST_MAX)
548 size = XATTR_LIST_MAX;
549 klist = kmalloc(size, __GFP_NOWARN | GFP_KERNEL);
550 if (!klist) {
551 vlist = vmalloc(size);
552 if (!vlist)
553 return -ENOMEM;
554 klist = vlist;
555 }
556 }
557
558 error = vfs_listxattr(d, klist, size);
559 if (error > 0) {
560 if (size && copy_to_user(list, klist, error))
561 error = -EFAULT;
562 } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
563 /* The file system tried to returned a list bigger
564 than XATTR_LIST_MAX bytes. Not possible. */
565 error = -E2BIG;
566 }
567 if (vlist)
568 vfree(vlist);
569 else
570 kfree(klist);
571 return error;
572}
573
574SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
575 size_t, size)
576{
577 struct path path;
578 ssize_t error;
579 unsigned int lookup_flags = LOOKUP_FOLLOW;
580retry:
581 error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
582 if (error)
583 return error;
584 error = listxattr(path.dentry, list, size);
585 path_put(&path);
586 if (retry_estale(error, lookup_flags)) {
587 lookup_flags |= LOOKUP_REVAL;
588 goto retry;
589 }
590 return error;
591}
592
593SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
594 size_t, size)
595{
596 struct path path;
597 ssize_t error;
598 unsigned int lookup_flags = 0;
599retry:
600 error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
601 if (error)
602 return error;
603 error = listxattr(path.dentry, list, size);
604 path_put(&path);
605 if (retry_estale(error, lookup_flags)) {
606 lookup_flags |= LOOKUP_REVAL;
607 goto retry;
608 }
609 return error;
610}
611
612SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
613{
614 struct fd f = fdget(fd);
615 ssize_t error = -EBADF;
616
617 if (!f.file)
618 return error;
619 audit_inode(NULL, f.file->f_path.dentry, 0);
620 error = listxattr(f.file->f_path.dentry, list, size);
621 fdput(f);
622 return error;
623}
624
625/*
626 * Extended attribute REMOVE operations
627 */
628static long
629removexattr(struct dentry *d, const char __user *name)
630{
631 int error;
632 char kname[XATTR_NAME_MAX + 1];
633
634 error = strncpy_from_user(kname, name, sizeof(kname));
635 if (error == 0 || error == sizeof(kname))
636 error = -ERANGE;
637 if (error < 0)
638 return error;
639
640 return vfs_removexattr(d, kname);
641}
642
643SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
644 const char __user *, name)
645{
646 struct path path;
647 int error;
648 unsigned int lookup_flags = LOOKUP_FOLLOW;
649retry:
650 error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
651 if (error)
652 return error;
653 error = mnt_want_write(path.mnt);
654 if (!error) {
655 error = removexattr(path.dentry, name);
656 mnt_drop_write(path.mnt);
657 }
658 path_put(&path);
659 if (retry_estale(error, lookup_flags)) {
660 lookup_flags |= LOOKUP_REVAL;
661 goto retry;
662 }
663 return error;
664}
665
666SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
667 const char __user *, name)
668{
669 struct path path;
670 int error;
671 unsigned int lookup_flags = 0;
672retry:
673 error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
674 if (error)
675 return error;
676 error = mnt_want_write(path.mnt);
677 if (!error) {
678 error = removexattr(path.dentry, name);
679 mnt_drop_write(path.mnt);
680 }
681 path_put(&path);
682 if (retry_estale(error, lookup_flags)) {
683 lookup_flags |= LOOKUP_REVAL;
684 goto retry;
685 }
686 return error;
687}
688
689SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
690{
691 struct fd f = fdget(fd);
692 struct dentry *dentry;
693 int error = -EBADF;
694
695 if (!f.file)
696 return error;
697 dentry = f.file->f_path.dentry;
698 audit_inode(NULL, dentry, 0);
699 error = mnt_want_write_file(f.file);
700 if (!error) {
701 error = removexattr(dentry, name);
702 mnt_drop_write_file(f.file);
703 }
704 fdput(f);
705 return error;
706}
707
708
709static const char *
710strcmp_prefix(const char *a, const char *a_prefix)
711{
712 while (*a_prefix && *a == *a_prefix) {
713 a++;
714 a_prefix++;
715 }
716 return *a_prefix ? NULL : a;
717}
718
719/*
720 * In order to implement different sets of xattr operations for each xattr
721 * prefix with the generic xattr API, a filesystem should create a
722 * null-terminated array of struct xattr_handler (one for each prefix) and
723 * hang a pointer to it off of the s_xattr field of the superblock.
724 *
725 * The generic_fooxattr() functions will use this list to dispatch xattr
726 * operations to the correct xattr_handler.
727 */
728#define for_each_xattr_handler(handlers, handler) \
729 for ((handler) = *(handlers)++; \
730 (handler) != NULL; \
731 (handler) = *(handlers)++)
732
733/*
734 * Find the xattr_handler with the matching prefix.
735 */
736static const struct xattr_handler *
737xattr_resolve_name(const struct xattr_handler **handlers, const char **name)
738{
739 const struct xattr_handler *handler;
740
741 if (!*name)
742 return NULL;
743
744 for_each_xattr_handler(handlers, handler) {
745 const char *n = strcmp_prefix(*name, handler->prefix);
746 if (n) {
747 *name = n;
748 break;
749 }
750 }
751 return handler;
752}
753
754/*
755 * Find the handler for the prefix and dispatch its get() operation.
756 */
757ssize_t
758generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size)
759{
760 const struct xattr_handler *handler;
761
762 handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
763 if (!handler)
764 return -EOPNOTSUPP;
765 return handler->get(dentry, name, buffer, size, handler->flags);
766}
767
768/*
769 * Combine the results of the list() operation from every xattr_handler in the
770 * list.
771 */
772ssize_t
773generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
774{
775 const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
776 unsigned int size = 0;
777
778 if (!buffer) {
779 for_each_xattr_handler(handlers, handler) {
780 size += handler->list(dentry, NULL, 0, NULL, 0,
781 handler->flags);
782 }
783 } else {
784 char *buf = buffer;
785
786 for_each_xattr_handler(handlers, handler) {
787 size = handler->list(dentry, buf, buffer_size,
788 NULL, 0, handler->flags);
789 if (size > buffer_size)
790 return -ERANGE;
791 buf += size;
792 buffer_size -= size;
793 }
794 size = buf - buffer;
795 }
796 return size;
797}
798
799/*
800 * Find the handler for the prefix and dispatch its set() operation.
801 */
802int
803generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags)
804{
805 const struct xattr_handler *handler;
806
807 if (size == 0)
808 value = ""; /* empty EA, do not remove */
809 handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
810 if (!handler)
811 return -EOPNOTSUPP;
812 return handler->set(dentry, name, value, size, flags, handler->flags);
813}
814
815/*
816 * Find the handler for the prefix and dispatch its set() operation to remove
817 * any associated extended attribute.
818 */
819int
820generic_removexattr(struct dentry *dentry, const char *name)
821{
822 const struct xattr_handler *handler;
823
824 handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
825 if (!handler)
826 return -EOPNOTSUPP;
827 return handler->set(dentry, name, NULL, 0,
828 XATTR_REPLACE, handler->flags);
829}
830
831EXPORT_SYMBOL(generic_getxattr);
832EXPORT_SYMBOL(generic_listxattr);
833EXPORT_SYMBOL(generic_setxattr);
834EXPORT_SYMBOL(generic_removexattr);
835
836/*
837 * Allocate new xattr and copy in the value; but leave the name to callers.
838 */
839struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
840{
841 struct simple_xattr *new_xattr;
842 size_t len;
843
844 /* wrap around? */
845 len = sizeof(*new_xattr) + size;
846 if (len <= sizeof(*new_xattr))
847 return NULL;
848
849 new_xattr = kmalloc(len, GFP_KERNEL);
850 if (!new_xattr)
851 return NULL;
852
853 new_xattr->size = size;
854 memcpy(new_xattr->value, value, size);
855 return new_xattr;
856}
857
858/*
859 * xattr GET operation for in-memory/pseudo filesystems
860 */
861int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
862 void *buffer, size_t size)
863{
864 struct simple_xattr *xattr;
865 int ret = -ENODATA;
866
867 spin_lock(&xattrs->lock);
868 list_for_each_entry(xattr, &xattrs->head, list) {
869 if (strcmp(name, xattr->name))
870 continue;
871
872 ret = xattr->size;
873 if (buffer) {
874 if (size < xattr->size)
875 ret = -ERANGE;
876 else
877 memcpy(buffer, xattr->value, xattr->size);
878 }
879 break;
880 }
881 spin_unlock(&xattrs->lock);
882 return ret;
883}
884
885static int __simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
886 const void *value, size_t size, int flags)
887{
888 struct simple_xattr *xattr;
889 struct simple_xattr *new_xattr = NULL;
890 int err = 0;
891
892 /* value == NULL means remove */
893 if (value) {
894 new_xattr = simple_xattr_alloc(value, size);
895 if (!new_xattr)
896 return -ENOMEM;
897
898 new_xattr->name = kstrdup(name, GFP_KERNEL);
899 if (!new_xattr->name) {
900 kfree(new_xattr);
901 return -ENOMEM;
902 }
903 }
904
905 spin_lock(&xattrs->lock);
906 list_for_each_entry(xattr, &xattrs->head, list) {
907 if (!strcmp(name, xattr->name)) {
908 if (flags & XATTR_CREATE) {
909 xattr = new_xattr;
910 err = -EEXIST;
911 } else if (new_xattr) {
912 list_replace(&xattr->list, &new_xattr->list);
913 } else {
914 list_del(&xattr->list);
915 }
916 goto out;
917 }
918 }
919 if (flags & XATTR_REPLACE) {
920 xattr = new_xattr;
921 err = -ENODATA;
922 } else {
923 list_add(&new_xattr->list, &xattrs->head);
924 xattr = NULL;
925 }
926out:
927 spin_unlock(&xattrs->lock);
928 if (xattr) {
929 kfree(xattr->name);
930 kfree(xattr);
931 }
932 return err;
933
934}
935
936/**
937 * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
938 * @xattrs: target simple_xattr list
939 * @name: name of the new extended attribute
940 * @value: value of the new xattr. If %NULL, will remove the attribute
941 * @size: size of the new xattr
942 * @flags: %XATTR_{CREATE|REPLACE}
943 *
944 * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
945 * with -EEXIST. If %XATTR_REPLACE is set, the xattr should exist;
946 * otherwise, fails with -ENODATA.
947 *
948 * Returns 0 on success, -errno on failure.
949 */
950int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
951 const void *value, size_t size, int flags)
952{
953 if (size == 0)
954 value = ""; /* empty EA, do not remove */
955 return __simple_xattr_set(xattrs, name, value, size, flags);
956}
957
958/*
959 * xattr REMOVE operation for in-memory/pseudo filesystems
960 */
961int simple_xattr_remove(struct simple_xattrs *xattrs, const char *name)
962{
963 return __simple_xattr_set(xattrs, name, NULL, 0, XATTR_REPLACE);
964}
965
966static bool xattr_is_trusted(const char *name)
967{
968 return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
969}
970
971/*
972 * xattr LIST operation for in-memory/pseudo filesystems
973 */
974ssize_t simple_xattr_list(struct simple_xattrs *xattrs, char *buffer,
975 size_t size)
976{
977 bool trusted = capable(CAP_SYS_ADMIN);
978 struct simple_xattr *xattr;
979 size_t used = 0;
980
981 spin_lock(&xattrs->lock);
982 list_for_each_entry(xattr, &xattrs->head, list) {
983 size_t len;
984
985 /* skip "trusted." attributes for unprivileged callers */
986 if (!trusted && xattr_is_trusted(xattr->name))
987 continue;
988
989 len = strlen(xattr->name) + 1;
990 used += len;
991 if (buffer) {
992 if (size < used) {
993 used = -ERANGE;
994 break;
995 }
996 memcpy(buffer, xattr->name, len);
997 buffer += len;
998 }
999 }
1000 spin_unlock(&xattrs->lock);
1001
1002 return used;
1003}
1004
1005/*
1006 * Adds an extended attribute to the list
1007 */
1008void simple_xattr_list_add(struct simple_xattrs *xattrs,
1009 struct simple_xattr *new_xattr)
1010{
1011 spin_lock(&xattrs->lock);
1012 list_add(&new_xattr->list, &xattrs->head);
1013 spin_unlock(&xattrs->lock);
1014}