1 /*
2 * This file is part of UBIFS.
3 *
4 * Copyright (C) 2006-2008 Nokia Corporation.
5 *
6 * This program is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 as published by
8 * the Free Software Foundation.
9 *
10 * This program is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
13 * more details.
14 *
15 * You should have received a copy of the GNU General Public License along with
16 * this program; if not, write to the Free Software Foundation, Inc., 51
17 * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
18 *
19 * Authors: Artem Bityutskiy (Битюцкий Артём)
20 * Adrian Hunter
21 */
22
23 /*
24 * This file implements UBIFS extended attributes support.
25 *
26 * Extended attributes are implemented as regular inodes with attached data,
27 * which limits extended attribute size to UBIFS block size (4KiB). Names of
28 * extended attributes are described by extended attribute entries (xentries),
29 * which are almost identical to directory entries, but have different key type.
30 *
31 * In other words, the situation with extended attributes is very similar to
32 * directories. Indeed, any inode (but of course not xattr inodes) may have a
33 * number of associated xentries, just like directory inodes have associated
34 * directory entries. Extended attribute entries store the name of the extended
35 * attribute, the host inode number, and the extended attribute inode number.
36 * Similarly, direntries store the name, the parent and the target inode
37 * numbers. Thus, most of the common UBIFS mechanisms may be re-used for
38 * extended attributes.
39 *
40 * The number of extended attributes is not limited, but there is Linux
41 * limitation on the maximum possible size of the list of all extended
42 * attributes associated with an inode (%XATTR_LIST_MAX), so UBIFS makes sure
43 * the sum of all extended attribute names of the inode does not exceed that
44 * limit.
45 *
46 * Extended attributes are synchronous, which means they are written to the
47 * flash media synchronously and there is no write-back for extended attribute
48 * inodes. The extended attribute values are not stored in compressed form on
49 * the media.
50 *
51 * Since extended attributes are represented by regular inodes, they are cached
52 * in the VFS inode cache. The xentries are cached in the LNC cache (see
53 * tnc.c).
54 *
55 * ACL support is not implemented.
56 */
57
58 #include "ubifs.h"
59 #include <linux/fs.h>
60 #include <linux/slab.h>
61 #include <linux/xattr.h>
62 #include <linux/posix_acl_xattr.h>
63
64 /*
65 * Limit the number of extended attributes per inode so that the total size
66 * (@xattr_size) is guaranteeded to fit in an 'unsigned int'.
67 */
68 #define MAX_XATTRS_PER_INODE 65535
69
70 /*
71 * Extended attribute type constants.
72 *
73 * USER_XATTR: user extended attribute ("user.*")
74 * TRUSTED_XATTR: trusted extended attribute ("trusted.*)
75 * SECURITY_XATTR: security extended attribute ("security.*")
76 */
77 enum {
78 USER_XATTR,
79 TRUSTED_XATTR,
80 SECURITY_XATTR,
81 };
82
83 static const struct inode_operations empty_iops;
84 static const struct file_operations empty_fops;
85
86 /**
87 * create_xattr - create an extended attribute.
88 * @c: UBIFS file-system description object
89 * @host: host inode
90 * @nm: extended attribute name
91 * @value: extended attribute value
92 * @size: size of extended attribute value
93 *
94 * This is a helper function which creates an extended attribute of name @nm
95 * and value @value for inode @host. The host inode is also updated on flash
96 * because the ctime and extended attribute accounting data changes. This
97 * function returns zero in case of success and a negative error code in case
98 * of failure.
99 */
create_xattr(struct ubifs_info * c,struct inode * host,const struct qstr * nm,const void * value,int size)100 static int create_xattr(struct ubifs_info *c, struct inode *host,
101 const struct qstr *nm, const void *value, int size)
102 {
103 int err, names_len;
104 struct inode *inode;
105 struct ubifs_inode *ui, *host_ui = ubifs_inode(host);
106 struct ubifs_budget_req req = { .new_ino = 1, .new_dent = 1,
107 .new_ino_d = ALIGN(size, 8), .dirtied_ino = 1,
108 .dirtied_ino_d = ALIGN(host_ui->data_len, 8) };
109
110 if (host_ui->xattr_cnt >= MAX_XATTRS_PER_INODE) {
111 ubifs_err(c, "inode %lu already has too many xattrs (%d), cannot create more",
112 host->i_ino, host_ui->xattr_cnt);
113 return -ENOSPC;
114 }
115 /*
116 * Linux limits the maximum size of the extended attribute names list
117 * to %XATTR_LIST_MAX. This means we should not allow creating more
118 * extended attributes if the name list becomes larger. This limitation
119 * is artificial for UBIFS, though.
120 */
121 names_len = host_ui->xattr_names + host_ui->xattr_cnt + nm->len + 1;
122 if (names_len > XATTR_LIST_MAX) {
123 ubifs_err(c, "cannot add one more xattr name to inode %lu, total names length would become %d, max. is %d",
124 host->i_ino, names_len, XATTR_LIST_MAX);
125 return -ENOSPC;
126 }
127
128 err = ubifs_budget_space(c, &req);
129 if (err)
130 return err;
131
132 inode = ubifs_new_inode(c, host, S_IFREG | S_IRWXUGO);
133 if (IS_ERR(inode)) {
134 err = PTR_ERR(inode);
135 goto out_budg;
136 }
137
138 /* Re-define all operations to be "nothing" */
139 inode->i_mapping->a_ops = &empty_aops;
140 inode->i_op = &empty_iops;
141 inode->i_fop = &empty_fops;
142
143 inode->i_flags |= S_SYNC | S_NOATIME | S_NOCMTIME | S_NOQUOTA;
144 ui = ubifs_inode(inode);
145 ui->xattr = 1;
146 ui->flags |= UBIFS_XATTR_FL;
147 ui->data = kmemdup(value, size, GFP_NOFS);
148 if (!ui->data) {
149 err = -ENOMEM;
150 goto out_free;
151 }
152 inode->i_size = ui->ui_size = size;
153 ui->data_len = size;
154
155 mutex_lock(&host_ui->ui_mutex);
156 host->i_ctime = ubifs_current_time(host);
157 host_ui->xattr_cnt += 1;
158 host_ui->xattr_size += CALC_DENT_SIZE(nm->len);
159 host_ui->xattr_size += CALC_XATTR_BYTES(size);
160 host_ui->xattr_names += nm->len;
161
162 err = ubifs_jnl_update(c, host, nm, inode, 0, 1);
163 if (err)
164 goto out_cancel;
165 mutex_unlock(&host_ui->ui_mutex);
166
167 ubifs_release_budget(c, &req);
168 insert_inode_hash(inode);
169 iput(inode);
170 return 0;
171
172 out_cancel:
173 host_ui->xattr_cnt -= 1;
174 host_ui->xattr_size -= CALC_DENT_SIZE(nm->len);
175 host_ui->xattr_size -= CALC_XATTR_BYTES(size);
176 host_ui->xattr_names -= nm->len;
177 mutex_unlock(&host_ui->ui_mutex);
178 out_free:
179 make_bad_inode(inode);
180 iput(inode);
181 out_budg:
182 ubifs_release_budget(c, &req);
183 return err;
184 }
185
186 /**
187 * change_xattr - change an extended attribute.
188 * @c: UBIFS file-system description object
189 * @host: host inode
190 * @inode: extended attribute inode
191 * @value: extended attribute value
192 * @size: size of extended attribute value
193 *
194 * This helper function changes the value of extended attribute @inode with new
195 * data from @value. Returns zero in case of success and a negative error code
196 * in case of failure.
197 */
change_xattr(struct ubifs_info * c,struct inode * host,struct inode * inode,const void * value,int size)198 static int change_xattr(struct ubifs_info *c, struct inode *host,
199 struct inode *inode, const void *value, int size)
200 {
201 int err;
202 struct ubifs_inode *host_ui = ubifs_inode(host);
203 struct ubifs_inode *ui = ubifs_inode(inode);
204 void *buf = NULL;
205 struct ubifs_budget_req req = { .dirtied_ino = 2,
206 .dirtied_ino_d = ALIGN(size, 8) + ALIGN(host_ui->data_len, 8) };
207
208 ubifs_assert(ui->data_len == inode->i_size);
209 err = ubifs_budget_space(c, &req);
210 if (err)
211 return err;
212
213 buf = kmemdup(value, size, GFP_NOFS);
214 if (!buf) {
215 err = -ENOMEM;
216 goto out_free;
217 }
218 mutex_lock(&ui->ui_mutex);
219 kfree(ui->data);
220 ui->data = buf;
221 inode->i_size = ui->ui_size = size;
222 ui->data_len = size;
223 mutex_unlock(&ui->ui_mutex);
224
225 mutex_lock(&host_ui->ui_mutex);
226 host->i_ctime = ubifs_current_time(host);
227 host_ui->xattr_size -= CALC_XATTR_BYTES(ui->data_len);
228 host_ui->xattr_size += CALC_XATTR_BYTES(size);
229
230 /*
231 * It is important to write the host inode after the xattr inode
232 * because if the host inode gets synchronized (via 'fsync()'), then
233 * the extended attribute inode gets synchronized, because it goes
234 * before the host inode in the write-buffer.
235 */
236 err = ubifs_jnl_change_xattr(c, inode, host);
237 if (err)
238 goto out_cancel;
239 mutex_unlock(&host_ui->ui_mutex);
240
241 ubifs_release_budget(c, &req);
242 return 0;
243
244 out_cancel:
245 host_ui->xattr_size -= CALC_XATTR_BYTES(size);
246 host_ui->xattr_size += CALC_XATTR_BYTES(ui->data_len);
247 mutex_unlock(&host_ui->ui_mutex);
248 make_bad_inode(inode);
249 out_free:
250 ubifs_release_budget(c, &req);
251 return err;
252 }
253
254 /**
255 * check_namespace - check extended attribute name-space.
256 * @nm: extended attribute name
257 *
258 * This function makes sure the extended attribute name belongs to one of the
259 * supported extended attribute name-spaces. Returns name-space index in case
260 * of success and a negative error code in case of failure.
261 */
check_namespace(const struct qstr * nm)262 static int check_namespace(const struct qstr *nm)
263 {
264 int type;
265
266 if (nm->len > UBIFS_MAX_NLEN)
267 return -ENAMETOOLONG;
268
269 if (!strncmp(nm->name, XATTR_TRUSTED_PREFIX,
270 XATTR_TRUSTED_PREFIX_LEN)) {
271 if (nm->name[sizeof(XATTR_TRUSTED_PREFIX) - 1] == '\0')
272 return -EINVAL;
273 type = TRUSTED_XATTR;
274 } else if (!strncmp(nm->name, XATTR_USER_PREFIX,
275 XATTR_USER_PREFIX_LEN)) {
276 if (nm->name[XATTR_USER_PREFIX_LEN] == '\0')
277 return -EINVAL;
278 type = USER_XATTR;
279 } else if (!strncmp(nm->name, XATTR_SECURITY_PREFIX,
280 XATTR_SECURITY_PREFIX_LEN)) {
281 if (nm->name[sizeof(XATTR_SECURITY_PREFIX) - 1] == '\0')
282 return -EINVAL;
283 type = SECURITY_XATTR;
284 } else
285 return -EOPNOTSUPP;
286
287 return type;
288 }
289
iget_xattr(struct ubifs_info * c,ino_t inum)290 static struct inode *iget_xattr(struct ubifs_info *c, ino_t inum)
291 {
292 struct inode *inode;
293
294 inode = ubifs_iget(c->vfs_sb, inum);
295 if (IS_ERR(inode)) {
296 ubifs_err(c, "dead extended attribute entry, error %d",
297 (int)PTR_ERR(inode));
298 return inode;
299 }
300 if (ubifs_inode(inode)->xattr)
301 return inode;
302 ubifs_err(c, "corrupt extended attribute entry");
303 iput(inode);
304 return ERR_PTR(-EINVAL);
305 }
306
setxattr(struct inode * host,const char * name,const void * value,size_t size,int flags)307 static int setxattr(struct inode *host, const char *name, const void *value,
308 size_t size, int flags)
309 {
310 struct inode *inode;
311 struct ubifs_info *c = host->i_sb->s_fs_info;
312 struct qstr nm = QSTR_INIT(name, strlen(name));
313 struct ubifs_dent_node *xent;
314 union ubifs_key key;
315 int err, type;
316
317 ubifs_assert(mutex_is_locked(&host->i_mutex));
318
319 if (size > UBIFS_MAX_INO_DATA)
320 return -ERANGE;
321
322 type = check_namespace(&nm);
323 if (type < 0)
324 return type;
325
326 xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
327 if (!xent)
328 return -ENOMEM;
329
330 /*
331 * The extended attribute entries are stored in LNC, so multiple
332 * look-ups do not involve reading the flash.
333 */
334 xent_key_init(c, &key, host->i_ino, &nm);
335 err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
336 if (err) {
337 if (err != -ENOENT)
338 goto out_free;
339
340 if (flags & XATTR_REPLACE)
341 /* We are asked not to create the xattr */
342 err = -ENODATA;
343 else
344 err = create_xattr(c, host, &nm, value, size);
345 goto out_free;
346 }
347
348 if (flags & XATTR_CREATE) {
349 /* We are asked not to replace the xattr */
350 err = -EEXIST;
351 goto out_free;
352 }
353
354 inode = iget_xattr(c, le64_to_cpu(xent->inum));
355 if (IS_ERR(inode)) {
356 err = PTR_ERR(inode);
357 goto out_free;
358 }
359
360 err = change_xattr(c, host, inode, value, size);
361 iput(inode);
362
363 out_free:
364 kfree(xent);
365 return err;
366 }
367
ubifs_setxattr(struct dentry * dentry,const char * name,const void * value,size_t size,int flags)368 int ubifs_setxattr(struct dentry *dentry, const char *name,
369 const void *value, size_t size, int flags)
370 {
371 dbg_gen("xattr '%s', host ino %lu ('%pd'), size %zd",
372 name, d_inode(dentry)->i_ino, dentry, size);
373
374 return setxattr(d_inode(dentry), name, value, size, flags);
375 }
376
ubifs_getxattr(struct dentry * dentry,const char * name,void * buf,size_t size)377 ssize_t ubifs_getxattr(struct dentry *dentry, const char *name, void *buf,
378 size_t size)
379 {
380 struct inode *inode, *host = d_inode(dentry);
381 struct ubifs_info *c = host->i_sb->s_fs_info;
382 struct qstr nm = QSTR_INIT(name, strlen(name));
383 struct ubifs_inode *ui;
384 struct ubifs_dent_node *xent;
385 union ubifs_key key;
386 int err;
387
388 dbg_gen("xattr '%s', ino %lu ('%pd'), buf size %zd", name,
389 host->i_ino, dentry, size);
390
391 err = check_namespace(&nm);
392 if (err < 0)
393 return err;
394
395 xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
396 if (!xent)
397 return -ENOMEM;
398
399 xent_key_init(c, &key, host->i_ino, &nm);
400 err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
401 if (err) {
402 if (err == -ENOENT)
403 err = -ENODATA;
404 goto out_unlock;
405 }
406
407 inode = iget_xattr(c, le64_to_cpu(xent->inum));
408 if (IS_ERR(inode)) {
409 err = PTR_ERR(inode);
410 goto out_unlock;
411 }
412
413 ui = ubifs_inode(inode);
414 ubifs_assert(inode->i_size == ui->data_len);
415 ubifs_assert(ubifs_inode(host)->xattr_size > ui->data_len);
416
417 mutex_lock(&ui->ui_mutex);
418 if (buf) {
419 /* If @buf is %NULL we are supposed to return the length */
420 if (ui->data_len > size) {
421 ubifs_err(c, "buffer size %zd, xattr len %d",
422 size, ui->data_len);
423 err = -ERANGE;
424 goto out_iput;
425 }
426
427 memcpy(buf, ui->data, ui->data_len);
428 }
429 err = ui->data_len;
430
431 out_iput:
432 mutex_unlock(&ui->ui_mutex);
433 iput(inode);
434 out_unlock:
435 kfree(xent);
436 return err;
437 }
438
ubifs_listxattr(struct dentry * dentry,char * buffer,size_t size)439 ssize_t ubifs_listxattr(struct dentry *dentry, char *buffer, size_t size)
440 {
441 union ubifs_key key;
442 struct inode *host = d_inode(dentry);
443 struct ubifs_info *c = host->i_sb->s_fs_info;
444 struct ubifs_inode *host_ui = ubifs_inode(host);
445 struct ubifs_dent_node *xent, *pxent = NULL;
446 int err, len, written = 0;
447 struct qstr nm = { .name = NULL };
448
449 dbg_gen("ino %lu ('%pd'), buffer size %zd", host->i_ino,
450 dentry, size);
451
452 len = host_ui->xattr_names + host_ui->xattr_cnt;
453 if (!buffer)
454 /*
455 * We should return the minimum buffer size which will fit a
456 * null-terminated list of all the extended attribute names.
457 */
458 return len;
459
460 if (len > size)
461 return -ERANGE;
462
463 lowest_xent_key(c, &key, host->i_ino);
464 while (1) {
465 int type;
466
467 xent = ubifs_tnc_next_ent(c, &key, &nm);
468 if (IS_ERR(xent)) {
469 err = PTR_ERR(xent);
470 break;
471 }
472
473 nm.name = xent->name;
474 nm.len = le16_to_cpu(xent->nlen);
475
476 type = check_namespace(&nm);
477 if (unlikely(type < 0)) {
478 err = type;
479 break;
480 }
481
482 /* Show trusted namespace only for "power" users */
483 if (type != TRUSTED_XATTR || capable(CAP_SYS_ADMIN)) {
484 memcpy(buffer + written, nm.name, nm.len + 1);
485 written += nm.len + 1;
486 }
487
488 kfree(pxent);
489 pxent = xent;
490 key_read(c, &xent->key, &key);
491 }
492
493 kfree(pxent);
494 if (err != -ENOENT) {
495 ubifs_err(c, "cannot find next direntry, error %d", err);
496 return err;
497 }
498
499 ubifs_assert(written <= size);
500 return written;
501 }
502
remove_xattr(struct ubifs_info * c,struct inode * host,struct inode * inode,const struct qstr * nm)503 static int remove_xattr(struct ubifs_info *c, struct inode *host,
504 struct inode *inode, const struct qstr *nm)
505 {
506 int err;
507 struct ubifs_inode *host_ui = ubifs_inode(host);
508 struct ubifs_inode *ui = ubifs_inode(inode);
509 struct ubifs_budget_req req = { .dirtied_ino = 2, .mod_dent = 1,
510 .dirtied_ino_d = ALIGN(host_ui->data_len, 8) };
511
512 ubifs_assert(ui->data_len == inode->i_size);
513
514 err = ubifs_budget_space(c, &req);
515 if (err)
516 return err;
517
518 mutex_lock(&host_ui->ui_mutex);
519 host->i_ctime = ubifs_current_time(host);
520 host_ui->xattr_cnt -= 1;
521 host_ui->xattr_size -= CALC_DENT_SIZE(nm->len);
522 host_ui->xattr_size -= CALC_XATTR_BYTES(ui->data_len);
523 host_ui->xattr_names -= nm->len;
524
525 err = ubifs_jnl_delete_xattr(c, host, inode, nm);
526 if (err)
527 goto out_cancel;
528 mutex_unlock(&host_ui->ui_mutex);
529
530 ubifs_release_budget(c, &req);
531 return 0;
532
533 out_cancel:
534 host_ui->xattr_cnt += 1;
535 host_ui->xattr_size += CALC_DENT_SIZE(nm->len);
536 host_ui->xattr_size += CALC_XATTR_BYTES(ui->data_len);
537 host_ui->xattr_names += nm->len;
538 mutex_unlock(&host_ui->ui_mutex);
539 ubifs_release_budget(c, &req);
540 make_bad_inode(inode);
541 return err;
542 }
543
ubifs_removexattr(struct dentry * dentry,const char * name)544 int ubifs_removexattr(struct dentry *dentry, const char *name)
545 {
546 struct inode *inode, *host = d_inode(dentry);
547 struct ubifs_info *c = host->i_sb->s_fs_info;
548 struct qstr nm = QSTR_INIT(name, strlen(name));
549 struct ubifs_dent_node *xent;
550 union ubifs_key key;
551 int err;
552
553 dbg_gen("xattr '%s', ino %lu ('%pd')", name,
554 host->i_ino, dentry);
555 ubifs_assert(mutex_is_locked(&host->i_mutex));
556
557 err = check_namespace(&nm);
558 if (err < 0)
559 return err;
560
561 xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
562 if (!xent)
563 return -ENOMEM;
564
565 xent_key_init(c, &key, host->i_ino, &nm);
566 err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
567 if (err) {
568 if (err == -ENOENT)
569 err = -ENODATA;
570 goto out_free;
571 }
572
573 inode = iget_xattr(c, le64_to_cpu(xent->inum));
574 if (IS_ERR(inode)) {
575 err = PTR_ERR(inode);
576 goto out_free;
577 }
578
579 ubifs_assert(inode->i_nlink == 1);
580 clear_nlink(inode);
581 err = remove_xattr(c, host, inode, &nm);
582 if (err)
583 set_nlink(inode, 1);
584
585 /* If @i_nlink is 0, 'iput()' will delete the inode */
586 iput(inode);
587
588 out_free:
589 kfree(xent);
590 return err;
591 }
592
init_xattrs(struct inode * inode,const struct xattr * xattr_array,void * fs_info)593 static int init_xattrs(struct inode *inode, const struct xattr *xattr_array,
594 void *fs_info)
595 {
596 const struct xattr *xattr;
597 char *name;
598 int err = 0;
599
600 for (xattr = xattr_array; xattr->name != NULL; xattr++) {
601 name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
602 strlen(xattr->name) + 1, GFP_NOFS);
603 if (!name) {
604 err = -ENOMEM;
605 break;
606 }
607 strcpy(name, XATTR_SECURITY_PREFIX);
608 strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
609 err = setxattr(inode, name, xattr->value, xattr->value_len, 0);
610 kfree(name);
611 if (err < 0)
612 break;
613 }
614
615 return err;
616 }
617
ubifs_init_security(struct inode * dentry,struct inode * inode,const struct qstr * qstr)618 int ubifs_init_security(struct inode *dentry, struct inode *inode,
619 const struct qstr *qstr)
620 {
621 int err;
622
623 err = security_inode_init_security(inode, dentry, qstr,
624 &init_xattrs, 0);
625 if (err) {
626 struct ubifs_info *c = dentry->i_sb->s_fs_info;
627 ubifs_err(c, "cannot initialize security for inode %lu, error %d",
628 inode->i_ino, err);
629 }
630 return err;
631 }
632