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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 /*
28 * Check permissions for extended attribute access. This is a bit complicated
29 * because different namespaces have very different rules.
30 */
31 static int
32 xattr_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 */
92 int __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
121 int
122 vfs_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
139 out:
140 inode_unlock(inode);
141 return error;
142 }
143 EXPORT_SYMBOL_GPL(vfs_setxattr);
144
145 ssize_t
146 xattr_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);
165 out:
166 security_release_secctx(buffer, len);
167 out_noalloc:
168 return len;
169 }
170 EXPORT_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 */
180 ssize_t
181 vfs_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 ssize_t
212 vfs_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 }
237 nolsm:
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 }
245 EXPORT_SYMBOL_GPL(vfs_getxattr);
246
247 ssize_t
248 vfs_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 }
265 EXPORT_SYMBOL_GPL(vfs_listxattr);
266
267 int
268 vfs_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
292 out:
293 inode_unlock(inode);
294 return error;
295 }
296 EXPORT_SYMBOL_GPL(vfs_removexattr);
297
298
299 /*
300 * Extended attribute SET operations
301 */
302 static long
303 setxattr(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);
338 out:
339 kvfree(kvalue);
340
341 return error;
342 }
343
344 static 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;
350 retry:
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
367 SYSCALL_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
374 SYSCALL_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
381 SYSCALL_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 */
402 static ssize_t
403 getxattr(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
445 static 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;
451 retry:
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
464 SYSCALL_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
470 SYSCALL_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
476 SYSCALL_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 */
493 static ssize_t
494 listxattr(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
525 static 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;
530 retry:
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
543 SYSCALL_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
549 SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
550 size_t, size)
551 {
552 return path_listxattr(pathname, list, size, 0);
553 }
554
555 SYSCALL_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 */
571 static long
572 removexattr(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
586 static int path_removexattr(const char __user *pathname,
587 const char __user *name, unsigned int lookup_flags)
588 {
589 struct path path;
590 int error;
591 retry:
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
608 SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
609 const char __user *, name)
610 {
611 return path_removexattr(pathname, name, LOOKUP_FOLLOW);
612 }
613
614 SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
615 const char __user *, name)
616 {
617 return path_removexattr(pathname, name, 0);
618 }
619
620 SYSCALL_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
638 static const char *
639 strcmp_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 */
665 static const struct xattr_handler *
666 xattr_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 */
693 ssize_t
694 generic_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 */
708 ssize_t
709 generic_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 */
744 int
745 generic_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 */
761 int
762 generic_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
772 EXPORT_SYMBOL(generic_getxattr);
773 EXPORT_SYMBOL(generic_listxattr);
774 EXPORT_SYMBOL(generic_setxattr);
775 EXPORT_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 */
792 const 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 }
799 EXPORT_SYMBOL(xattr_full_name);
800
801 /*
802 * Allocate new xattr and copy in the value; but leave the name to callers.
803 */
804 struct 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 */
826 int 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 */
864 int 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 }
905 out:
906 spin_unlock(&xattrs->lock);
907 if (xattr) {
908 kfree(xattr->name);
909 kfree(xattr);
910 }
911 return err;
912
913 }
914
915 static bool xattr_is_trusted(const char *name)
916 {
917 return !strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN);
918 }
919
920 static 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 */
937 ssize_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;
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 return err;
969 }
970 spin_unlock(&xattrs->lock);
971
972 return size - remaining_size;
973 }
974
975 /*
976 * Adds an extended attribute to the list
977 */
978 void 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 }