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1 /*
2 File: fs/xattr.c
3
4 Extended attribute handling.
5
6 Copyright (C) 2001 by Andreas Gruenbacher <a.gruenbacher@computer.org>
7 Copyright (C) 2001 SGI - Silicon Graphics, Inc <linux-xfs@oss.sgi.com>
8 Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
9 */
10 #include <linux/fs.h>
11 #include <linux/slab.h>
12 #include <linux/file.h>
13 #include <linux/xattr.h>
14 #include <linux/mount.h>
15 #include <linux/namei.h>
16 #include <linux/security.h>
17 #include <linux/evm.h>
18 #include <linux/syscalls.h>
19 #include <linux/export.h>
20 #include <linux/fsnotify.h>
21 #include <linux/audit.h>
22 #include <linux/vmalloc.h>
23 #include <linux/posix_acl_xattr.h>
24
25 #include <asm/uaccess.h>
26
27 static const char *
28 strcmp_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 */
52 static const struct xattr_handler *
53 xattr_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 */
84 static int
85 xattr_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
136 int
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 }
151 EXPORT_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 */
169 int __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 = -EOPNOTSUPP;
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 if (issec) {
187 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
188
189 if (unlikely(is_bad_inode(inode)))
190 return -EIO;
191 error = security_inode_setsecurity(inode, suffix, value,
192 size, flags);
193 if (!error)
194 fsnotify_xattr(dentry);
195 }
196
197 return error;
198 }
199
200
201 int
202 vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
203 size_t size, int flags)
204 {
205 struct inode *inode = dentry->d_inode;
206 int error;
207
208 error = xattr_permission(inode, name, MAY_WRITE);
209 if (error)
210 return error;
211
212 inode_lock(inode);
213 error = security_inode_setxattr(dentry, name, value, size, flags);
214 if (error)
215 goto out;
216
217 error = __vfs_setxattr_noperm(dentry, name, value, size, flags);
218
219 out:
220 inode_unlock(inode);
221 return error;
222 }
223 EXPORT_SYMBOL_GPL(vfs_setxattr);
224
225 ssize_t
226 xattr_getsecurity(struct inode *inode, const char *name, void *value,
227 size_t size)
228 {
229 void *buffer = NULL;
230 ssize_t len;
231
232 if (!value || !size) {
233 len = security_inode_getsecurity(inode, name, &buffer, false);
234 goto out_noalloc;
235 }
236
237 len = security_inode_getsecurity(inode, name, &buffer, true);
238 if (len < 0)
239 return len;
240 if (size < len) {
241 len = -ERANGE;
242 goto out;
243 }
244 memcpy(value, buffer, len);
245 out:
246 security_release_secctx(buffer, len);
247 out_noalloc:
248 return len;
249 }
250 EXPORT_SYMBOL_GPL(xattr_getsecurity);
251
252 /*
253 * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
254 *
255 * Allocate memory, if not already allocated, or re-allocate correct size,
256 * before retrieving the extended attribute.
257 *
258 * Returns the result of alloc, if failed, or the getxattr operation.
259 */
260 ssize_t
261 vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value,
262 size_t xattr_size, gfp_t flags)
263 {
264 const struct xattr_handler *handler;
265 struct inode *inode = dentry->d_inode;
266 char *value = *xattr_value;
267 int error;
268
269 error = xattr_permission(inode, name, MAY_READ);
270 if (error)
271 return error;
272
273 handler = xattr_resolve_name(inode, &name);
274 if (IS_ERR(handler))
275 return PTR_ERR(handler);
276 if (!handler->get)
277 return -EOPNOTSUPP;
278 error = handler->get(handler, dentry, inode, name, NULL, 0);
279 if (error < 0)
280 return error;
281
282 if (!value || (error > xattr_size)) {
283 value = krealloc(*xattr_value, error + 1, flags);
284 if (!value)
285 return -ENOMEM;
286 memset(value, 0, error + 1);
287 }
288
289 error = handler->get(handler, dentry, inode, name, value, error);
290 *xattr_value = value;
291 return error;
292 }
293
294 ssize_t
295 __vfs_getxattr(struct dentry *dentry, struct inode *inode, const char *name,
296 void *value, size_t size)
297 {
298 const struct xattr_handler *handler;
299
300 handler = xattr_resolve_name(inode, &name);
301 if (IS_ERR(handler))
302 return PTR_ERR(handler);
303 if (!handler->get)
304 return -EOPNOTSUPP;
305 return handler->get(handler, dentry, inode, name, value, size);
306 }
307 EXPORT_SYMBOL(__vfs_getxattr);
308
309 ssize_t
310 vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
311 {
312 struct inode *inode = dentry->d_inode;
313 int error;
314
315 error = xattr_permission(inode, name, MAY_READ);
316 if (error)
317 return error;
318
319 error = security_inode_getxattr(dentry, name);
320 if (error)
321 return error;
322
323 if (!strncmp(name, XATTR_SECURITY_PREFIX,
324 XATTR_SECURITY_PREFIX_LEN)) {
325 const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
326 int ret = xattr_getsecurity(inode, suffix, value, size);
327 /*
328 * Only overwrite the return value if a security module
329 * is actually active.
330 */
331 if (ret == -EOPNOTSUPP)
332 goto nolsm;
333 return ret;
334 }
335 nolsm:
336 return __vfs_getxattr(dentry, inode, name, value, size);
337 }
338 EXPORT_SYMBOL_GPL(vfs_getxattr);
339
340 ssize_t
341 vfs_listxattr(struct dentry *dentry, char *list, size_t size)
342 {
343 struct inode *inode = d_inode(dentry);
344 ssize_t error;
345
346 error = security_inode_listxattr(dentry);
347 if (error)
348 return error;
349 if (inode->i_op->listxattr && (inode->i_opflags & IOP_XATTR)) {
350 error = -EOPNOTSUPP;
351 error = inode->i_op->listxattr(dentry, list, size);
352 } else {
353 error = security_inode_listsecurity(inode, list, size);
354 if (size && error > size)
355 error = -ERANGE;
356 }
357 return error;
358 }
359 EXPORT_SYMBOL_GPL(vfs_listxattr);
360
361 int
362 __vfs_removexattr(struct dentry *dentry, const char *name)
363 {
364 struct inode *inode = d_inode(dentry);
365 const struct xattr_handler *handler;
366
367 handler = xattr_resolve_name(inode, &name);
368 if (IS_ERR(handler))
369 return PTR_ERR(handler);
370 if (!handler->set)
371 return -EOPNOTSUPP;
372 return handler->set(handler, dentry, inode, name, NULL, 0, XATTR_REPLACE);
373 }
374 EXPORT_SYMBOL(__vfs_removexattr);
375
376 int
377 vfs_removexattr(struct dentry *dentry, const char *name)
378 {
379 struct inode *inode = dentry->d_inode;
380 int error;
381
382 error = xattr_permission(inode, name, MAY_WRITE);
383 if (error)
384 return error;
385
386 inode_lock(inode);
387 error = security_inode_removexattr(dentry, name);
388 if (error)
389 goto out;
390
391 error = __vfs_removexattr(dentry, name);
392
393 if (!error) {
394 fsnotify_xattr(dentry);
395 evm_inode_post_removexattr(dentry, name);
396 }
397
398 out:
399 inode_unlock(inode);
400 return error;
401 }
402 EXPORT_SYMBOL_GPL(vfs_removexattr);
403
404
405 /*
406 * Extended attribute SET operations
407 */
408 static long
409 setxattr(struct dentry *d, const char __user *name, const void __user *value,
410 size_t size, int flags)
411 {
412 int error;
413 void *kvalue = NULL;
414 char kname[XATTR_NAME_MAX + 1];
415
416 if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
417 return -EINVAL;
418
419 error = strncpy_from_user(kname, name, sizeof(kname));
420 if (error == 0 || error == sizeof(kname))
421 error = -ERANGE;
422 if (error < 0)
423 return error;
424
425 if (size) {
426 if (size > XATTR_SIZE_MAX)
427 return -E2BIG;
428 kvalue = kmalloc(size, GFP_KERNEL | __GFP_NOWARN);
429 if (!kvalue) {
430 kvalue = vmalloc(size);
431 if (!kvalue)
432 return -ENOMEM;
433 }
434 if (copy_from_user(kvalue, value, size)) {
435 error = -EFAULT;
436 goto out;
437 }
438 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
439 (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
440 posix_acl_fix_xattr_from_user(kvalue, size);
441 }
442
443 error = vfs_setxattr(d, kname, kvalue, size, flags);
444 out:
445 kvfree(kvalue);
446
447 return error;
448 }
449
450 static int path_setxattr(const char __user *pathname,
451 const char __user *name, const void __user *value,
452 size_t size, int flags, unsigned int lookup_flags)
453 {
454 struct path path;
455 int error;
456 retry:
457 error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
458 if (error)
459 return error;
460 error = mnt_want_write(path.mnt);
461 if (!error) {
462 error = setxattr(path.dentry, name, value, size, flags);
463 mnt_drop_write(path.mnt);
464 }
465 path_put(&path);
466 if (retry_estale(error, lookup_flags)) {
467 lookup_flags |= LOOKUP_REVAL;
468 goto retry;
469 }
470 return error;
471 }
472
473 SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
474 const char __user *, name, const void __user *, value,
475 size_t, size, int, flags)
476 {
477 return path_setxattr(pathname, name, value, size, flags, LOOKUP_FOLLOW);
478 }
479
480 SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
481 const char __user *, name, const void __user *, value,
482 size_t, size, int, flags)
483 {
484 return path_setxattr(pathname, name, value, size, flags, 0);
485 }
486
487 SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
488 const void __user *,value, size_t, size, int, flags)
489 {
490 struct fd f = fdget(fd);
491 int error = -EBADF;
492
493 if (!f.file)
494 return error;
495 audit_file(f.file);
496 error = mnt_want_write_file(f.file);
497 if (!error) {
498 error = setxattr(f.file->f_path.dentry, name, value, size, flags);
499 mnt_drop_write_file(f.file);
500 }
501 fdput(f);
502 return error;
503 }
504
505 /*
506 * Extended attribute GET operations
507 */
508 static ssize_t
509 getxattr(struct dentry *d, const char __user *name, void __user *value,
510 size_t size)
511 {
512 ssize_t error;
513 void *kvalue = NULL;
514 char kname[XATTR_NAME_MAX + 1];
515
516 error = strncpy_from_user(kname, name, sizeof(kname));
517 if (error == 0 || error == sizeof(kname))
518 error = -ERANGE;
519 if (error < 0)
520 return error;
521
522 if (size) {
523 if (size > XATTR_SIZE_MAX)
524 size = XATTR_SIZE_MAX;
525 kvalue = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
526 if (!kvalue) {
527 kvalue = vmalloc(size);
528 if (!kvalue)
529 return -ENOMEM;
530 }
531 }
532
533 error = vfs_getxattr(d, kname, kvalue, size);
534 if (error > 0) {
535 if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
536 (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
537 posix_acl_fix_xattr_to_user(kvalue, size);
538 if (size && copy_to_user(value, kvalue, error))
539 error = -EFAULT;
540 } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
541 /* The file system tried to returned a value bigger
542 than XATTR_SIZE_MAX bytes. Not possible. */
543 error = -E2BIG;
544 }
545
546 kvfree(kvalue);
547
548 return error;
549 }
550
551 static ssize_t path_getxattr(const char __user *pathname,
552 const char __user *name, void __user *value,
553 size_t size, unsigned int lookup_flags)
554 {
555 struct path path;
556 ssize_t error;
557 retry:
558 error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
559 if (error)
560 return error;
561 error = getxattr(path.dentry, name, value, size);
562 path_put(&path);
563 if (retry_estale(error, lookup_flags)) {
564 lookup_flags |= LOOKUP_REVAL;
565 goto retry;
566 }
567 return error;
568 }
569
570 SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
571 const char __user *, name, void __user *, value, size_t, size)
572 {
573 return path_getxattr(pathname, name, value, size, LOOKUP_FOLLOW);
574 }
575
576 SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
577 const char __user *, name, void __user *, value, size_t, size)
578 {
579 return path_getxattr(pathname, name, value, size, 0);
580 }
581
582 SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
583 void __user *, value, size_t, size)
584 {
585 struct fd f = fdget(fd);
586 ssize_t error = -EBADF;
587
588 if (!f.file)
589 return error;
590 audit_file(f.file);
591 error = getxattr(f.file->f_path.dentry, name, value, size);
592 fdput(f);
593 return error;
594 }
595
596 /*
597 * Extended attribute LIST operations
598 */
599 static ssize_t
600 listxattr(struct dentry *d, char __user *list, size_t size)
601 {
602 ssize_t error;
603 char *klist = NULL;
604
605 if (size) {
606 if (size > XATTR_LIST_MAX)
607 size = XATTR_LIST_MAX;
608 klist = kmalloc(size, __GFP_NOWARN | GFP_KERNEL);
609 if (!klist) {
610 klist = vmalloc(size);
611 if (!klist)
612 return -ENOMEM;
613 }
614 }
615
616 error = vfs_listxattr(d, klist, size);
617 if (error > 0) {
618 if (size && copy_to_user(list, klist, error))
619 error = -EFAULT;
620 } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
621 /* The file system tried to returned a list bigger
622 than XATTR_LIST_MAX bytes. Not possible. */
623 error = -E2BIG;
624 }
625
626 kvfree(klist);
627
628 return error;
629 }
630
631 static ssize_t path_listxattr(const char __user *pathname, char __user *list,
632 size_t size, unsigned int lookup_flags)
633 {
634 struct path path;
635 ssize_t error;
636 retry:
637 error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
638 if (error)
639 return error;
640 error = listxattr(path.dentry, list, size);
641 path_put(&path);
642 if (retry_estale(error, lookup_flags)) {
643 lookup_flags |= LOOKUP_REVAL;
644 goto retry;
645 }
646 return error;
647 }
648
649 SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
650 size_t, size)
651 {
652 return path_listxattr(pathname, list, size, LOOKUP_FOLLOW);
653 }
654
655 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
656 size_t, size)
657 {
658 return path_listxattr(pathname, list, size, 0);
659 }
660
661 SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
662 {
663 struct fd f = fdget(fd);
664 ssize_t error = -EBADF;
665
666 if (!f.file)
667 return error;
668 audit_file(f.file);
669 error = listxattr(f.file->f_path.dentry, list, size);
670 fdput(f);
671 return error;
672 }
673
674 /*
675 * Extended attribute REMOVE operations
676 */
677 static long
678 removexattr(struct dentry *d, const char __user *name)
679 {
680 int error;
681 char kname[XATTR_NAME_MAX + 1];
682
683 error = strncpy_from_user(kname, name, sizeof(kname));
684 if (error == 0 || error == sizeof(kname))
685 error = -ERANGE;
686 if (error < 0)
687 return error;
688
689 return vfs_removexattr(d, kname);
690 }
691
692 static int path_removexattr(const char __user *pathname,
693 const char __user *name, unsigned int lookup_flags)
694 {
695 struct path path;
696 int error;
697 retry:
698 error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
699 if (error)
700 return error;
701 error = mnt_want_write(path.mnt);
702 if (!error) {
703 error = removexattr(path.dentry, name);
704 mnt_drop_write(path.mnt);
705 }
706 path_put(&path);
707 if (retry_estale(error, lookup_flags)) {
708 lookup_flags |= LOOKUP_REVAL;
709 goto retry;
710 }
711 return error;
712 }
713
714 SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
715 const char __user *, name)
716 {
717 return path_removexattr(pathname, name, LOOKUP_FOLLOW);
718 }
719
720 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
721 const char __user *, name)
722 {
723 return path_removexattr(pathname, name, 0);
724 }
725
726 SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
727 {
728 struct fd f = fdget(fd);
729 int error = -EBADF;
730
731 if (!f.file)
732 return error;
733 audit_file(f.file);
734 error = mnt_want_write_file(f.file);
735 if (!error) {
736 error = removexattr(f.file->f_path.dentry, name);
737 mnt_drop_write_file(f.file);
738 }
739 fdput(f);
740 return error;
741 }
742
743 /*
744 * Combine the results of the list() operation from every xattr_handler in the
745 * list.
746 */
747 ssize_t
748 generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
749 {
750 const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
751 unsigned int size = 0;
752
753 if (!buffer) {
754 for_each_xattr_handler(handlers, handler) {
755 if (!handler->name ||
756 (handler->list && !handler->list(dentry)))
757 continue;
758 size += strlen(handler->name) + 1;
759 }
760 } else {
761 char *buf = buffer;
762 size_t len;
763
764 for_each_xattr_handler(handlers, handler) {
765 if (!handler->name ||
766 (handler->list && !handler->list(dentry)))
767 continue;
768 len = strlen(handler->name);
769 if (len + 1 > buffer_size)
770 return -ERANGE;
771 memcpy(buf, handler->name, len + 1);
772 buf += len + 1;
773 buffer_size -= len + 1;
774 }
775 size = buf - buffer;
776 }
777 return size;
778 }
779 EXPORT_SYMBOL(generic_listxattr);
780
781 /**
782 * xattr_full_name - Compute full attribute name from suffix
783 *
784 * @handler: handler of the xattr_handler operation
785 * @name: name passed to the xattr_handler operation
786 *
787 * The get and set xattr handler operations are called with the remainder of
788 * the attribute name after skipping the handler's prefix: for example, "foo"
789 * is passed to the get operation of a handler with prefix "user." to get
790 * attribute "user.foo". The full name is still "there" in the name though.
791 *
792 * Note: the list xattr handler operation when called from the vfs is passed a
793 * NULL name; some file systems use this operation internally, with varying
794 * semantics.
795 */
796 const char *xattr_full_name(const struct xattr_handler *handler,
797 const char *name)
798 {
799 size_t prefix_len = strlen(xattr_prefix(handler));
800
801 return name - prefix_len;
802 }
803 EXPORT_SYMBOL(xattr_full_name);
804
805 /*
806 * Allocate new xattr and copy in the value; but leave the name to callers.
807 */
808 struct simple_xattr *simple_xattr_alloc(const void *value, size_t size)
809 {
810 struct simple_xattr *new_xattr;
811 size_t len;
812
813 /* wrap around? */
814 len = sizeof(*new_xattr) + size;
815 if (len < sizeof(*new_xattr))
816 return NULL;
817
818 new_xattr = kmalloc(len, GFP_KERNEL);
819 if (!new_xattr)
820 return NULL;
821
822 new_xattr->size = size;
823 memcpy(new_xattr->value, value, size);
824 return new_xattr;
825 }
826
827 /*
828 * xattr GET operation for in-memory/pseudo filesystems
829 */
830 int simple_xattr_get(struct simple_xattrs *xattrs, const char *name,
831 void *buffer, size_t size)
832 {
833 struct simple_xattr *xattr;
834 int ret = -ENODATA;
835
836 spin_lock(&xattrs->lock);
837 list_for_each_entry(xattr, &xattrs->head, list) {
838 if (strcmp(name, xattr->name))
839 continue;
840
841 ret = xattr->size;
842 if (buffer) {
843 if (size < xattr->size)
844 ret = -ERANGE;
845 else
846 memcpy(buffer, xattr->value, xattr->size);
847 }
848 break;
849 }
850 spin_unlock(&xattrs->lock);
851 return ret;
852 }
853
854 /**
855 * simple_xattr_set - xattr SET operation for in-memory/pseudo filesystems
856 * @xattrs: target simple_xattr list
857 * @name: name of the extended attribute
858 * @value: value of the xattr. If %NULL, will remove the attribute.
859 * @size: size of the new xattr
860 * @flags: %XATTR_{CREATE|REPLACE}
861 *
862 * %XATTR_CREATE is set, the xattr shouldn't exist already; otherwise fails
863 * with -EEXIST. If %XATTR_REPLACE is set, the xattr should exist;
864 * otherwise, fails with -ENODATA.
865 *
866 * Returns 0 on success, -errno on failure.
867 */
868 int simple_xattr_set(struct simple_xattrs *xattrs, const char *name,
869 const void *value, size_t size, int flags)
870 {
871 struct simple_xattr *xattr;
872 struct simple_xattr *new_xattr = NULL;
873 int err = 0;
874
875 /* value == NULL means remove */
876 if (value) {
877 new_xattr = simple_xattr_alloc(value, size);
878 if (!new_xattr)
879 return -ENOMEM;
880
881 new_xattr->name = kstrdup(name, GFP_KERNEL);
882 if (!new_xattr->name) {
883 kfree(new_xattr);
884 return -ENOMEM;
885 }
886 }
887
888 spin_lock(&xattrs->lock);
889 list_for_each_entry(xattr, &xattrs->head, list) {
890 if (!strcmp(name, xattr->name)) {
891 if (flags & XATTR_CREATE) {
892 xattr = new_xattr;
893 err = -EEXIST;
894 } else if (new_xattr) {
895 list_replace(&xattr->list, &new_xattr->list);
896 } else {
897 list_del(&xattr->list);
898 }
899 goto out;
900 }
901 }
902 if (flags & XATTR_REPLACE) {
903 xattr = new_xattr;
904 err = -ENODATA;
905 } else {
906 list_add(&new_xattr->list, &xattrs->head);
907 xattr = NULL;
908 }
909 out:
910 spin_unlock(&xattrs->lock);
911 if (xattr) {
912 kfree(xattr->name);
913 kfree(xattr);
914 }
915 return err;
916
917 }
918
919 static bool xattr_is_trusted(const char *name)
920 {
921 return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
922 }
923
924 static int xattr_list_one(char **buffer, ssize_t *remaining_size,
925 const char *name)
926 {
927 size_t len = strlen(name) + 1;
928 if (*buffer) {
929 if (*remaining_size < len)
930 return -ERANGE;
931 memcpy(*buffer, name, len);
932 *buffer += len;
933 }
934 *remaining_size -= len;
935 return 0;
936 }
937
938 /*
939 * xattr LIST operation for in-memory/pseudo filesystems
940 */
941 ssize_t simple_xattr_list(struct inode *inode, struct simple_xattrs *xattrs,
942 char *buffer, size_t size)
943 {
944 bool trusted = capable(CAP_SYS_ADMIN);
945 struct simple_xattr *xattr;
946 ssize_t remaining_size = size;
947 int err = 0;
948
949 #ifdef CONFIG_FS_POSIX_ACL
950 if (inode->i_acl) {
951 err = xattr_list_one(&buffer, &remaining_size,
952 XATTR_NAME_POSIX_ACL_ACCESS);
953 if (err)
954 return err;
955 }
956 if (inode->i_default_acl) {
957 err = xattr_list_one(&buffer, &remaining_size,
958 XATTR_NAME_POSIX_ACL_DEFAULT);
959 if (err)
960 return err;
961 }
962 #endif
963
964 spin_lock(&xattrs->lock);
965 list_for_each_entry(xattr, &xattrs->head, list) {
966 /* skip "trusted." attributes for unprivileged callers */
967 if (!trusted && xattr_is_trusted(xattr->name))
968 continue;
969
970 err = xattr_list_one(&buffer, &remaining_size, xattr->name);
971 if (err)
972 break;
973 }
974 spin_unlock(&xattrs->lock);
975
976 return err ? err : size - remaining_size;
977 }
978
979 /*
980 * Adds an extended attribute to the list
981 */
982 void simple_xattr_list_add(struct simple_xattrs *xattrs,
983 struct simple_xattr *new_xattr)
984 {
985 spin_lock(&xattrs->lock);
986 list_add(&new_xattr->list, &xattrs->head);
987 spin_unlock(&xattrs->lock);
988 }