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 63 /* 64 * Limit the number of extended attributes per inode so that the total size 65 * (@xattr_size) is guaranteeded to fit in an 'unsigned int'. 66 */ 67 #define MAX_XATTRS_PER_INODE 65535 68 69 /* 70 * Extended attribute type constants. 71 * 72 * USER_XATTR: user extended attribute ("user.*") 73 * TRUSTED_XATTR: trusted extended attribute ("trusted.*) 74 * SECURITY_XATTR: security extended attribute ("security.*") 75 */ 76 enum { 77 USER_XATTR, 78 TRUSTED_XATTR, 79 SECURITY_XATTR, 80 }; 81 82 static const struct inode_operations empty_iops; 83 static const struct file_operations empty_fops; 84 85 /** 86 * create_xattr - create an extended attribute. 87 * @c: UBIFS file-system description object 88 * @host: host inode 89 * @nm: extended attribute name 90 * @value: extended attribute value 91 * @size: size of extended attribute value 92 * 93 * This is a helper function which creates an extended attribute of name @nm 94 * and value @value for inode @host. The host inode is also updated on flash 95 * because the ctime and extended attribute accounting data changes. This 96 * function returns zero in case of success and a negative error code in case 97 * of failure. 98 */ 99 static int create_xattr(struct ubifs_info *c, struct inode *host, 100 const struct qstr *nm, const void *value, int size) 101 { 102 int err, names_len; 103 struct inode *inode; 104 struct ubifs_inode *ui, *host_ui = ubifs_inode(host); 105 struct ubifs_budget_req req = { .new_ino = 1, .new_dent = 1, 106 .new_ino_d = ALIGN(size, 8), .dirtied_ino = 1, 107 .dirtied_ino_d = ALIGN(host_ui->data_len, 8) }; 108 109 if (host_ui->xattr_cnt >= MAX_XATTRS_PER_INODE) { 110 ubifs_err(c, "inode %lu already has too many xattrs (%d), cannot create more", 111 host->i_ino, host_ui->xattr_cnt); 112 return -ENOSPC; 113 } 114 /* 115 * Linux limits the maximum size of the extended attribute names list 116 * to %XATTR_LIST_MAX. This means we should not allow creating more 117 * extended attributes if the name list becomes larger. This limitation 118 * is artificial for UBIFS, though. 119 */ 120 names_len = host_ui->xattr_names + host_ui->xattr_cnt + nm->len + 1; 121 if (names_len > XATTR_LIST_MAX) { 122 ubifs_err(c, "cannot add one more xattr name to inode %lu, total names length would become %d, max. is %d", 123 host->i_ino, names_len, XATTR_LIST_MAX); 124 return -ENOSPC; 125 } 126 127 err = ubifs_budget_space(c, &req); 128 if (err) 129 return err; 130 131 inode = ubifs_new_inode(c, host, S_IFREG | S_IRWXUGO); 132 if (IS_ERR(inode)) { 133 err = PTR_ERR(inode); 134 goto out_budg; 135 } 136 137 /* Re-define all operations to be "nothing" */ 138 inode->i_mapping->a_ops = &empty_aops; 139 inode->i_op = &empty_iops; 140 inode->i_fop = &empty_fops; 141 142 inode->i_flags |= S_SYNC | S_NOATIME | S_NOCMTIME | S_NOQUOTA; 143 ui = ubifs_inode(inode); 144 ui->xattr = 1; 145 ui->flags |= UBIFS_XATTR_FL; 146 ui->data = kmemdup(value, size, GFP_NOFS); 147 if (!ui->data) { 148 err = -ENOMEM; 149 goto out_free; 150 } 151 inode->i_size = ui->ui_size = size; 152 ui->data_len = size; 153 154 mutex_lock(&host_ui->ui_mutex); 155 host->i_ctime = ubifs_current_time(host); 156 host_ui->xattr_cnt += 1; 157 host_ui->xattr_size += CALC_DENT_SIZE(nm->len); 158 host_ui->xattr_size += CALC_XATTR_BYTES(size); 159 host_ui->xattr_names += nm->len; 160 161 err = ubifs_jnl_update(c, host, nm, inode, 0, 1); 162 if (err) 163 goto out_cancel; 164 mutex_unlock(&host_ui->ui_mutex); 165 166 ubifs_release_budget(c, &req); 167 insert_inode_hash(inode); 168 iput(inode); 169 return 0; 170 171 out_cancel: 172 host_ui->xattr_cnt -= 1; 173 host_ui->xattr_size -= CALC_DENT_SIZE(nm->len); 174 host_ui->xattr_size -= CALC_XATTR_BYTES(size); 175 host_ui->xattr_names -= nm->len; 176 mutex_unlock(&host_ui->ui_mutex); 177 out_free: 178 make_bad_inode(inode); 179 iput(inode); 180 out_budg: 181 ubifs_release_budget(c, &req); 182 return err; 183 } 184 185 /** 186 * change_xattr - change an extended attribute. 187 * @c: UBIFS file-system description object 188 * @host: host inode 189 * @inode: extended attribute inode 190 * @value: extended attribute value 191 * @size: size of extended attribute value 192 * 193 * This helper function changes the value of extended attribute @inode with new 194 * data from @value. Returns zero in case of success and a negative error code 195 * in case of failure. 196 */ 197 static int change_xattr(struct ubifs_info *c, struct inode *host, 198 struct inode *inode, const void *value, int size) 199 { 200 int err; 201 struct ubifs_inode *host_ui = ubifs_inode(host); 202 struct ubifs_inode *ui = ubifs_inode(inode); 203 void *buf = NULL; 204 int old_size; 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 old_size = ui->data_len; 223 ui->data_len = size; 224 mutex_unlock(&ui->ui_mutex); 225 226 mutex_lock(&host_ui->ui_mutex); 227 host->i_ctime = ubifs_current_time(host); 228 host_ui->xattr_size -= CALC_XATTR_BYTES(old_size); 229 host_ui->xattr_size += CALC_XATTR_BYTES(size); 230 231 /* 232 * It is important to write the host inode after the xattr inode 233 * because if the host inode gets synchronized (via 'fsync()'), then 234 * the extended attribute inode gets synchronized, because it goes 235 * before the host inode in the write-buffer. 236 */ 237 err = ubifs_jnl_change_xattr(c, inode, host); 238 if (err) 239 goto out_cancel; 240 mutex_unlock(&host_ui->ui_mutex); 241 242 ubifs_release_budget(c, &req); 243 return 0; 244 245 out_cancel: 246 host_ui->xattr_size -= CALC_XATTR_BYTES(size); 247 host_ui->xattr_size += CALC_XATTR_BYTES(old_size); 248 mutex_unlock(&host_ui->ui_mutex); 249 make_bad_inode(inode); 250 out_free: 251 ubifs_release_budget(c, &req); 252 return err; 253 } 254 255 static struct inode *iget_xattr(struct ubifs_info *c, ino_t inum) 256 { 257 struct inode *inode; 258 259 inode = ubifs_iget(c->vfs_sb, inum); 260 if (IS_ERR(inode)) { 261 ubifs_err(c, "dead extended attribute entry, error %d", 262 (int)PTR_ERR(inode)); 263 return inode; 264 } 265 if (ubifs_inode(inode)->xattr) 266 return inode; 267 ubifs_err(c, "corrupt extended attribute entry"); 268 iput(inode); 269 return ERR_PTR(-EINVAL); 270 } 271 272 static int __ubifs_setxattr(struct inode *host, const char *name, 273 const void *value, size_t size, int flags) 274 { 275 struct inode *inode; 276 struct ubifs_info *c = host->i_sb->s_fs_info; 277 struct qstr nm = QSTR_INIT(name, strlen(name)); 278 struct ubifs_dent_node *xent; 279 union ubifs_key key; 280 int err; 281 282 ubifs_assert(inode_is_locked(host)); 283 284 if (size > UBIFS_MAX_INO_DATA) 285 return -ERANGE; 286 287 if (nm.len > UBIFS_MAX_NLEN) 288 return -ENAMETOOLONG; 289 290 xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS); 291 if (!xent) 292 return -ENOMEM; 293 294 /* 295 * The extended attribute entries are stored in LNC, so multiple 296 * look-ups do not involve reading the flash. 297 */ 298 xent_key_init(c, &key, host->i_ino, &nm); 299 err = ubifs_tnc_lookup_nm(c, &key, xent, &nm); 300 if (err) { 301 if (err != -ENOENT) 302 goto out_free; 303 304 if (flags & XATTR_REPLACE) 305 /* We are asked not to create the xattr */ 306 err = -ENODATA; 307 else 308 err = create_xattr(c, host, &nm, value, size); 309 goto out_free; 310 } 311 312 if (flags & XATTR_CREATE) { 313 /* We are asked not to replace the xattr */ 314 err = -EEXIST; 315 goto out_free; 316 } 317 318 inode = iget_xattr(c, le64_to_cpu(xent->inum)); 319 if (IS_ERR(inode)) { 320 err = PTR_ERR(inode); 321 goto out_free; 322 } 323 324 err = change_xattr(c, host, inode, value, size); 325 iput(inode); 326 327 out_free: 328 kfree(xent); 329 return err; 330 } 331 332 static ssize_t __ubifs_getxattr(struct inode *host, const char *name, 333 void *buf, size_t size) 334 { 335 struct inode *inode; 336 struct ubifs_info *c = host->i_sb->s_fs_info; 337 struct qstr nm = QSTR_INIT(name, strlen(name)); 338 struct ubifs_inode *ui; 339 struct ubifs_dent_node *xent; 340 union ubifs_key key; 341 int err; 342 343 if (nm.len > UBIFS_MAX_NLEN) 344 return -ENAMETOOLONG; 345 346 xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS); 347 if (!xent) 348 return -ENOMEM; 349 350 xent_key_init(c, &key, host->i_ino, &nm); 351 err = ubifs_tnc_lookup_nm(c, &key, xent, &nm); 352 if (err) { 353 if (err == -ENOENT) 354 err = -ENODATA; 355 goto out_unlock; 356 } 357 358 inode = iget_xattr(c, le64_to_cpu(xent->inum)); 359 if (IS_ERR(inode)) { 360 err = PTR_ERR(inode); 361 goto out_unlock; 362 } 363 364 ui = ubifs_inode(inode); 365 ubifs_assert(inode->i_size == ui->data_len); 366 ubifs_assert(ubifs_inode(host)->xattr_size > ui->data_len); 367 368 mutex_lock(&ui->ui_mutex); 369 if (buf) { 370 /* If @buf is %NULL we are supposed to return the length */ 371 if (ui->data_len > size) { 372 ubifs_err(c, "buffer size %zd, xattr len %d", 373 size, ui->data_len); 374 err = -ERANGE; 375 goto out_iput; 376 } 377 378 memcpy(buf, ui->data, ui->data_len); 379 } 380 err = ui->data_len; 381 382 out_iput: 383 mutex_unlock(&ui->ui_mutex); 384 iput(inode); 385 out_unlock: 386 kfree(xent); 387 return err; 388 } 389 390 ssize_t ubifs_listxattr(struct dentry *dentry, char *buffer, size_t size) 391 { 392 union ubifs_key key; 393 struct inode *host = d_inode(dentry); 394 struct ubifs_info *c = host->i_sb->s_fs_info; 395 struct ubifs_inode *host_ui = ubifs_inode(host); 396 struct ubifs_dent_node *xent, *pxent = NULL; 397 int err, len, written = 0; 398 struct qstr nm = { .name = NULL }; 399 400 dbg_gen("ino %lu ('%pd'), buffer size %zd", host->i_ino, 401 dentry, size); 402 403 len = host_ui->xattr_names + host_ui->xattr_cnt; 404 if (!buffer) 405 /* 406 * We should return the minimum buffer size which will fit a 407 * null-terminated list of all the extended attribute names. 408 */ 409 return len; 410 411 if (len > size) 412 return -ERANGE; 413 414 lowest_xent_key(c, &key, host->i_ino); 415 while (1) { 416 xent = ubifs_tnc_next_ent(c, &key, &nm); 417 if (IS_ERR(xent)) { 418 err = PTR_ERR(xent); 419 break; 420 } 421 422 nm.name = xent->name; 423 nm.len = le16_to_cpu(xent->nlen); 424 425 /* Show trusted namespace only for "power" users */ 426 if (strncmp(xent->name, XATTR_TRUSTED_PREFIX, 427 XATTR_TRUSTED_PREFIX_LEN) || 428 capable(CAP_SYS_ADMIN)) { 429 memcpy(buffer + written, nm.name, nm.len + 1); 430 written += nm.len + 1; 431 } 432 433 kfree(pxent); 434 pxent = xent; 435 key_read(c, &xent->key, &key); 436 } 437 438 kfree(pxent); 439 if (err != -ENOENT) { 440 ubifs_err(c, "cannot find next direntry, error %d", err); 441 return err; 442 } 443 444 ubifs_assert(written <= size); 445 return written; 446 } 447 448 static int remove_xattr(struct ubifs_info *c, struct inode *host, 449 struct inode *inode, const struct qstr *nm) 450 { 451 int err; 452 struct ubifs_inode *host_ui = ubifs_inode(host); 453 struct ubifs_inode *ui = ubifs_inode(inode); 454 struct ubifs_budget_req req = { .dirtied_ino = 2, .mod_dent = 1, 455 .dirtied_ino_d = ALIGN(host_ui->data_len, 8) }; 456 457 ubifs_assert(ui->data_len == inode->i_size); 458 459 err = ubifs_budget_space(c, &req); 460 if (err) 461 return err; 462 463 mutex_lock(&host_ui->ui_mutex); 464 host->i_ctime = ubifs_current_time(host); 465 host_ui->xattr_cnt -= 1; 466 host_ui->xattr_size -= CALC_DENT_SIZE(nm->len); 467 host_ui->xattr_size -= CALC_XATTR_BYTES(ui->data_len); 468 host_ui->xattr_names -= nm->len; 469 470 err = ubifs_jnl_delete_xattr(c, host, inode, nm); 471 if (err) 472 goto out_cancel; 473 mutex_unlock(&host_ui->ui_mutex); 474 475 ubifs_release_budget(c, &req); 476 return 0; 477 478 out_cancel: 479 host_ui->xattr_cnt += 1; 480 host_ui->xattr_size += CALC_DENT_SIZE(nm->len); 481 host_ui->xattr_size += CALC_XATTR_BYTES(ui->data_len); 482 host_ui->xattr_names += nm->len; 483 mutex_unlock(&host_ui->ui_mutex); 484 ubifs_release_budget(c, &req); 485 make_bad_inode(inode); 486 return err; 487 } 488 489 static int __ubifs_removexattr(struct inode *host, const char *name) 490 { 491 struct inode *inode; 492 struct ubifs_info *c = host->i_sb->s_fs_info; 493 struct qstr nm = QSTR_INIT(name, strlen(name)); 494 struct ubifs_dent_node *xent; 495 union ubifs_key key; 496 int err; 497 498 ubifs_assert(inode_is_locked(host)); 499 500 if (nm.len > UBIFS_MAX_NLEN) 501 return -ENAMETOOLONG; 502 503 xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS); 504 if (!xent) 505 return -ENOMEM; 506 507 xent_key_init(c, &key, host->i_ino, &nm); 508 err = ubifs_tnc_lookup_nm(c, &key, xent, &nm); 509 if (err) { 510 if (err == -ENOENT) 511 err = -ENODATA; 512 goto out_free; 513 } 514 515 inode = iget_xattr(c, le64_to_cpu(xent->inum)); 516 if (IS_ERR(inode)) { 517 err = PTR_ERR(inode); 518 goto out_free; 519 } 520 521 ubifs_assert(inode->i_nlink == 1); 522 clear_nlink(inode); 523 err = remove_xattr(c, host, inode, &nm); 524 if (err) 525 set_nlink(inode, 1); 526 527 /* If @i_nlink is 0, 'iput()' will delete the inode */ 528 iput(inode); 529 530 out_free: 531 kfree(xent); 532 return err; 533 } 534 535 static int init_xattrs(struct inode *inode, const struct xattr *xattr_array, 536 void *fs_info) 537 { 538 const struct xattr *xattr; 539 char *name; 540 int err = 0; 541 542 for (xattr = xattr_array; xattr->name != NULL; xattr++) { 543 name = kmalloc(XATTR_SECURITY_PREFIX_LEN + 544 strlen(xattr->name) + 1, GFP_NOFS); 545 if (!name) { 546 err = -ENOMEM; 547 break; 548 } 549 strcpy(name, XATTR_SECURITY_PREFIX); 550 strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name); 551 err = __ubifs_setxattr(inode, name, xattr->value, xattr->value_len, 0); 552 kfree(name); 553 if (err < 0) 554 break; 555 } 556 557 return err; 558 } 559 560 int ubifs_init_security(struct inode *dentry, struct inode *inode, 561 const struct qstr *qstr) 562 { 563 int err; 564 565 err = security_inode_init_security(inode, dentry, qstr, 566 &init_xattrs, 0); 567 if (err) { 568 struct ubifs_info *c = dentry->i_sb->s_fs_info; 569 ubifs_err(c, "cannot initialize security for inode %lu, error %d", 570 inode->i_ino, err); 571 } 572 return err; 573 } 574 575 static int ubifs_xattr_get(const struct xattr_handler *handler, 576 struct dentry *dentry, struct inode *inode, 577 const char *name, void *buffer, size_t size) 578 { 579 dbg_gen("xattr '%s', ino %lu ('%pd'), buf size %zd", name, 580 inode->i_ino, dentry, size); 581 582 name = xattr_full_name(handler, name); 583 return __ubifs_getxattr(inode, name, buffer, size); 584 } 585 586 static int ubifs_xattr_set(const struct xattr_handler *handler, 587 struct dentry *dentry, struct inode *inode, 588 const char *name, const void *value, 589 size_t size, int flags) 590 { 591 dbg_gen("xattr '%s', host ino %lu ('%pd'), size %zd", 592 name, inode->i_ino, dentry, size); 593 594 name = xattr_full_name(handler, name); 595 596 if (value) 597 return __ubifs_setxattr(inode, name, value, size, flags); 598 else 599 return __ubifs_removexattr(inode, name); 600 } 601 602 static const struct xattr_handler ubifs_user_xattr_handler = { 603 .prefix = XATTR_USER_PREFIX, 604 .get = ubifs_xattr_get, 605 .set = ubifs_xattr_set, 606 }; 607 608 static const struct xattr_handler ubifs_trusted_xattr_handler = { 609 .prefix = XATTR_TRUSTED_PREFIX, 610 .get = ubifs_xattr_get, 611 .set = ubifs_xattr_set, 612 }; 613 614 static const struct xattr_handler ubifs_security_xattr_handler = { 615 .prefix = XATTR_SECURITY_PREFIX, 616 .get = ubifs_xattr_get, 617 .set = ubifs_xattr_set, 618 }; 619 620 const struct xattr_handler *ubifs_xattr_handlers[] = { 621 &ubifs_user_xattr_handler, 622 &ubifs_trusted_xattr_handler, 623 &ubifs_security_xattr_handler, 624 NULL 625 }; 626