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Commit | Line | Data |
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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 | 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 | ||
139 | out: | |
140 | mutex_unlock(&inode->i_mutex); | |
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 | mutex_lock(&inode->i_mutex); | |
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 | mutex_unlock(&inode->i_mutex); | |
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 | } |