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 mutex_unlock(&host_ui->ui_mutex); 176 out_free: 177 make_bad_inode(inode); 178 iput(inode); 179 out_budg: 180 ubifs_release_budget(c, &req); 181 return err; 182 } 183 184 /** 185 * change_xattr - change an extended attribute. 186 * @c: UBIFS file-system description object 187 * @host: host inode 188 * @inode: extended attribute inode 189 * @value: extended attribute value 190 * @size: size of extended attribute value 191 * 192 * This helper function changes the value of extended attribute @inode with new 193 * data from @value. Returns zero in case of success and a negative error code 194 * in case of failure. 195 */ 196 static int change_xattr(struct ubifs_info *c, struct inode *host, 197 struct inode *inode, const void *value, int size) 198 { 199 int err; 200 struct ubifs_inode *host_ui = ubifs_inode(host); 201 struct ubifs_inode *ui = ubifs_inode(inode); 202 void *buf = NULL; 203 struct ubifs_budget_req req = { .dirtied_ino = 2, 204 .dirtied_ino_d = ALIGN(size, 8) + ALIGN(host_ui->data_len, 8) }; 205 206 ubifs_assert(ui->data_len == inode->i_size); 207 err = ubifs_budget_space(c, &req); 208 if (err) 209 return err; 210 211 buf = kmemdup(value, size, GFP_NOFS); 212 if (!buf) { 213 err = -ENOMEM; 214 goto out_free; 215 } 216 mutex_lock(&ui->ui_mutex); 217 kfree(ui->data); 218 ui->data = buf; 219 inode->i_size = ui->ui_size = size; 220 ui->data_len = size; 221 mutex_unlock(&ui->ui_mutex); 222 223 mutex_lock(&host_ui->ui_mutex); 224 host->i_ctime = ubifs_current_time(host); 225 host_ui->xattr_size -= CALC_XATTR_BYTES(ui->data_len); 226 host_ui->xattr_size += CALC_XATTR_BYTES(size); 227 228 /* 229 * It is important to write the host inode after the xattr inode 230 * because if the host inode gets synchronized (via 'fsync()'), then 231 * the extended attribute inode gets synchronized, because it goes 232 * before the host inode in the write-buffer. 233 */ 234 err = ubifs_jnl_change_xattr(c, inode, host); 235 if (err) 236 goto out_cancel; 237 mutex_unlock(&host_ui->ui_mutex); 238 239 ubifs_release_budget(c, &req); 240 return 0; 241 242 out_cancel: 243 host_ui->xattr_size -= CALC_XATTR_BYTES(size); 244 host_ui->xattr_size += CALC_XATTR_BYTES(ui->data_len); 245 mutex_unlock(&host_ui->ui_mutex); 246 make_bad_inode(inode); 247 out_free: 248 ubifs_release_budget(c, &req); 249 return err; 250 } 251 252 static struct inode *iget_xattr(struct ubifs_info *c, ino_t inum) 253 { 254 struct inode *inode; 255 256 inode = ubifs_iget(c->vfs_sb, inum); 257 if (IS_ERR(inode)) { 258 ubifs_err(c, "dead extended attribute entry, error %d", 259 (int)PTR_ERR(inode)); 260 return inode; 261 } 262 if (ubifs_inode(inode)->xattr) 263 return inode; 264 ubifs_err(c, "corrupt extended attribute entry"); 265 iput(inode); 266 return ERR_PTR(-EINVAL); 267 } 268 269 static int __ubifs_setxattr(struct inode *host, const char *name, 270 const void *value, size_t size, int flags) 271 { 272 struct inode *inode; 273 struct ubifs_info *c = host->i_sb->s_fs_info; 274 struct qstr nm = QSTR_INIT(name, strlen(name)); 275 struct ubifs_dent_node *xent; 276 union ubifs_key key; 277 int err; 278 279 ubifs_assert(inode_is_locked(host)); 280 281 if (size > UBIFS_MAX_INO_DATA) 282 return -ERANGE; 283 284 if (nm.len > UBIFS_MAX_NLEN) 285 return -ENAMETOOLONG; 286 287 xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS); 288 if (!xent) 289 return -ENOMEM; 290 291 /* 292 * The extended attribute entries are stored in LNC, so multiple 293 * look-ups do not involve reading the flash. 294 */ 295 xent_key_init(c, &key, host->i_ino, &nm); 296 err = ubifs_tnc_lookup_nm(c, &key, xent, &nm); 297 if (err) { 298 if (err != -ENOENT) 299 goto out_free; 300 301 if (flags & XATTR_REPLACE) 302 /* We are asked not to create the xattr */ 303 err = -ENODATA; 304 else 305 err = create_xattr(c, host, &nm, value, size); 306 goto out_free; 307 } 308 309 if (flags & XATTR_CREATE) { 310 /* We are asked not to replace the xattr */ 311 err = -EEXIST; 312 goto out_free; 313 } 314 315 inode = iget_xattr(c, le64_to_cpu(xent->inum)); 316 if (IS_ERR(inode)) { 317 err = PTR_ERR(inode); 318 goto out_free; 319 } 320 321 err = change_xattr(c, host, inode, value, size); 322 iput(inode); 323 324 out_free: 325 kfree(xent); 326 return err; 327 } 328 329 static ssize_t __ubifs_getxattr(struct inode *host, const char *name, 330 void *buf, size_t size) 331 { 332 struct inode *inode; 333 struct ubifs_info *c = host->i_sb->s_fs_info; 334 struct qstr nm = QSTR_INIT(name, strlen(name)); 335 struct ubifs_inode *ui; 336 struct ubifs_dent_node *xent; 337 union ubifs_key key; 338 int err; 339 340 if (nm.len > UBIFS_MAX_NLEN) 341 return -ENAMETOOLONG; 342 343 xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS); 344 if (!xent) 345 return -ENOMEM; 346 347 xent_key_init(c, &key, host->i_ino, &nm); 348 err = ubifs_tnc_lookup_nm(c, &key, xent, &nm); 349 if (err) { 350 if (err == -ENOENT) 351 err = -ENODATA; 352 goto out_unlock; 353 } 354 355 inode = iget_xattr(c, le64_to_cpu(xent->inum)); 356 if (IS_ERR(inode)) { 357 err = PTR_ERR(inode); 358 goto out_unlock; 359 } 360 361 ui = ubifs_inode(inode); 362 ubifs_assert(inode->i_size == ui->data_len); 363 ubifs_assert(ubifs_inode(host)->xattr_size > ui->data_len); 364 365 mutex_lock(&ui->ui_mutex); 366 if (buf) { 367 /* If @buf is %NULL we are supposed to return the length */ 368 if (ui->data_len > size) { 369 ubifs_err(c, "buffer size %zd, xattr len %d", 370 size, ui->data_len); 371 err = -ERANGE; 372 goto out_iput; 373 } 374 375 memcpy(buf, ui->data, ui->data_len); 376 } 377 err = ui->data_len; 378 379 out_iput: 380 mutex_unlock(&ui->ui_mutex); 381 iput(inode); 382 out_unlock: 383 kfree(xent); 384 return err; 385 } 386 387 ssize_t ubifs_listxattr(struct dentry *dentry, char *buffer, size_t size) 388 { 389 union ubifs_key key; 390 struct inode *host = d_inode(dentry); 391 struct ubifs_info *c = host->i_sb->s_fs_info; 392 struct ubifs_inode *host_ui = ubifs_inode(host); 393 struct ubifs_dent_node *xent, *pxent = NULL; 394 int err, len, written = 0; 395 struct qstr nm = { .name = NULL }; 396 397 dbg_gen("ino %lu ('%pd'), buffer size %zd", host->i_ino, 398 dentry, size); 399 400 len = host_ui->xattr_names + host_ui->xattr_cnt; 401 if (!buffer) 402 /* 403 * We should return the minimum buffer size which will fit a 404 * null-terminated list of all the extended attribute names. 405 */ 406 return len; 407 408 if (len > size) 409 return -ERANGE; 410 411 lowest_xent_key(c, &key, host->i_ino); 412 while (1) { 413 xent = ubifs_tnc_next_ent(c, &key, &nm); 414 if (IS_ERR(xent)) { 415 err = PTR_ERR(xent); 416 break; 417 } 418 419 nm.name = xent->name; 420 nm.len = le16_to_cpu(xent->nlen); 421 422 /* Show trusted namespace only for "power" users */ 423 if (strncmp(xent->name, XATTR_TRUSTED_PREFIX, 424 XATTR_TRUSTED_PREFIX_LEN) || 425 capable(CAP_SYS_ADMIN)) { 426 memcpy(buffer + written, nm.name, nm.len + 1); 427 written += nm.len + 1; 428 } 429 430 kfree(pxent); 431 pxent = xent; 432 key_read(c, &xent->key, &key); 433 } 434 435 kfree(pxent); 436 if (err != -ENOENT) { 437 ubifs_err(c, "cannot find next direntry, error %d", err); 438 return err; 439 } 440 441 ubifs_assert(written <= size); 442 return written; 443 } 444 445 static int remove_xattr(struct ubifs_info *c, struct inode *host, 446 struct inode *inode, const struct qstr *nm) 447 { 448 int err; 449 struct ubifs_inode *host_ui = ubifs_inode(host); 450 struct ubifs_inode *ui = ubifs_inode(inode); 451 struct ubifs_budget_req req = { .dirtied_ino = 2, .mod_dent = 1, 452 .dirtied_ino_d = ALIGN(host_ui->data_len, 8) }; 453 454 ubifs_assert(ui->data_len == inode->i_size); 455 456 err = ubifs_budget_space(c, &req); 457 if (err) 458 return err; 459 460 mutex_lock(&host_ui->ui_mutex); 461 host->i_ctime = ubifs_current_time(host); 462 host_ui->xattr_cnt -= 1; 463 host_ui->xattr_size -= CALC_DENT_SIZE(nm->len); 464 host_ui->xattr_size -= CALC_XATTR_BYTES(ui->data_len); 465 host_ui->xattr_names -= nm->len; 466 467 err = ubifs_jnl_delete_xattr(c, host, inode, nm); 468 if (err) 469 goto out_cancel; 470 mutex_unlock(&host_ui->ui_mutex); 471 472 ubifs_release_budget(c, &req); 473 return 0; 474 475 out_cancel: 476 host_ui->xattr_cnt += 1; 477 host_ui->xattr_size += CALC_DENT_SIZE(nm->len); 478 host_ui->xattr_size += CALC_XATTR_BYTES(ui->data_len); 479 mutex_unlock(&host_ui->ui_mutex); 480 ubifs_release_budget(c, &req); 481 make_bad_inode(inode); 482 return err; 483 } 484 485 static int __ubifs_removexattr(struct inode *host, const char *name) 486 { 487 struct inode *inode; 488 struct ubifs_info *c = host->i_sb->s_fs_info; 489 struct qstr nm = QSTR_INIT(name, strlen(name)); 490 struct ubifs_dent_node *xent; 491 union ubifs_key key; 492 int err; 493 494 ubifs_assert(inode_is_locked(host)); 495 496 if (nm.len > UBIFS_MAX_NLEN) 497 return -ENAMETOOLONG; 498 499 xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS); 500 if (!xent) 501 return -ENOMEM; 502 503 xent_key_init(c, &key, host->i_ino, &nm); 504 err = ubifs_tnc_lookup_nm(c, &key, xent, &nm); 505 if (err) { 506 if (err == -ENOENT) 507 err = -ENODATA; 508 goto out_free; 509 } 510 511 inode = iget_xattr(c, le64_to_cpu(xent->inum)); 512 if (IS_ERR(inode)) { 513 err = PTR_ERR(inode); 514 goto out_free; 515 } 516 517 ubifs_assert(inode->i_nlink == 1); 518 clear_nlink(inode); 519 err = remove_xattr(c, host, inode, &nm); 520 if (err) 521 set_nlink(inode, 1); 522 523 /* If @i_nlink is 0, 'iput()' will delete the inode */ 524 iput(inode); 525 526 out_free: 527 kfree(xent); 528 return err; 529 } 530 531 static int init_xattrs(struct inode *inode, const struct xattr *xattr_array, 532 void *fs_info) 533 { 534 const struct xattr *xattr; 535 char *name; 536 int err = 0; 537 538 for (xattr = xattr_array; xattr->name != NULL; xattr++) { 539 name = kmalloc(XATTR_SECURITY_PREFIX_LEN + 540 strlen(xattr->name) + 1, GFP_NOFS); 541 if (!name) { 542 err = -ENOMEM; 543 break; 544 } 545 strcpy(name, XATTR_SECURITY_PREFIX); 546 strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name); 547 err = __ubifs_setxattr(inode, name, xattr->value, xattr->value_len, 0); 548 kfree(name); 549 if (err < 0) 550 break; 551 } 552 553 return err; 554 } 555 556 int ubifs_init_security(struct inode *dentry, struct inode *inode, 557 const struct qstr *qstr) 558 { 559 int err; 560 561 err = security_inode_init_security(inode, dentry, qstr, 562 &init_xattrs, 0); 563 if (err) { 564 struct ubifs_info *c = dentry->i_sb->s_fs_info; 565 ubifs_err(c, "cannot initialize security for inode %lu, error %d", 566 inode->i_ino, err); 567 } 568 return err; 569 } 570 571 static int ubifs_xattr_get(const struct xattr_handler *handler, 572 struct dentry *dentry, struct inode *inode, 573 const char *name, void *buffer, size_t size) 574 { 575 dbg_gen("xattr '%s', ino %lu ('%pd'), buf size %zd", name, 576 inode->i_ino, dentry, size); 577 578 return __ubifs_getxattr(inode, name, buffer, size); 579 } 580 581 static int ubifs_xattr_set(const struct xattr_handler *handler, 582 struct dentry *dentry, struct inode *inode, 583 const char *name, const void *value, 584 size_t size, int flags) 585 { 586 dbg_gen("xattr '%s', host ino %lu ('%pd'), size %zd", 587 name, inode->i_ino, dentry, size); 588 589 if (value) 590 return __ubifs_setxattr(inode, name, value, size, flags); 591 else 592 return __ubifs_removexattr(inode, name); 593 } 594 595 const struct xattr_handler ubifs_user_xattr_handler = { 596 .prefix = XATTR_USER_PREFIX, 597 .get = ubifs_xattr_get, 598 .set = ubifs_xattr_set, 599 }; 600 601 const struct xattr_handler ubifs_trusted_xattr_handler = { 602 .prefix = XATTR_TRUSTED_PREFIX, 603 .get = ubifs_xattr_get, 604 .set = ubifs_xattr_set, 605 }; 606 607 const struct xattr_handler ubifs_security_xattr_handler = { 608 .prefix = XATTR_SECURITY_PREFIX, 609 .get = ubifs_xattr_get, 610 .set = ubifs_xattr_set, 611 }; 612 613 const struct xattr_handler *ubifs_xattr_handlers[] = { 614 &ubifs_user_xattr_handler, 615 &ubifs_trusted_xattr_handler, 616 &ubifs_security_xattr_handler, 617 NULL 618 }; 619