fs/ubifs/xattr.c

   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         int old_size;
 204         struct ubifs_budget_req req = { .dirtied_ino = 2,
 205                 .dirtied_ino_d = ALIGN(size, 8) + ALIGN(host_ui->data_len, 8) };
 206
 207         ubifs_assert(ui->data_len == inode->i_size);
 208         err = ubifs_budget_space(c, &req);
 209         if (err)
 210                 return err;
 211
 212         buf = kmemdup(value, size, GFP_NOFS);
 213         if (!buf) {
 214                 err = -ENOMEM;
 215                 goto out_free;
 216         }
 217         mutex_lock(&ui->ui_mutex);
 218         kfree(ui->data);
 219         ui->data = buf;
 220         inode->i_size = ui->ui_size = size;
 221         old_size = ui->data_len;
 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(old_size);
 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(old_size);
 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 static struct inode *iget_xattr(struct ubifs_info *c, ino_t inum)
 255 {
 256         struct inode *inode;
 257
 258         inode = ubifs_iget(c->vfs_sb, inum);
 259         if (IS_ERR(inode)) {
 260                 ubifs_err(c, "dead extended attribute entry, error %d",
 261                           (int)PTR_ERR(inode));
 262                 return inode;
 263         }
 264         if (ubifs_inode(inode)->xattr)
 265                 return inode;
 266         ubifs_err(c, "corrupt extended attribute entry");
 267         iput(inode);
 268         return ERR_PTR(-EINVAL);
 269 }
 270
 271 static int __ubifs_setxattr(struct inode *host, const char *name,
 272                             const void *value, size_t size, int flags)
 273 {
 274         struct inode *inode;
 275         struct ubifs_info *c = host->i_sb->s_fs_info;
 276         struct qstr nm = QSTR_INIT(name, strlen(name));
 277         struct ubifs_dent_node *xent;
 278         union ubifs_key key;
 279         int err;
 280
 281         ubifs_assert(inode_is_locked(host));
 282
 283         if (size > UBIFS_MAX_INO_DATA)
 284                 return -ERANGE;
 285
 286         if (nm.len > UBIFS_MAX_NLEN)
 287                 return -ENAMETOOLONG;
 288
 289         xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
 290         if (!xent)
 291                 return -ENOMEM;
 292
 293         /*
 294          * The extended attribute entries are stored in LNC, so multiple
 295          * look-ups do not involve reading the flash.
 296          */
 297         xent_key_init(c, &key, host->i_ino, &nm);
 298         err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
 299         if (err) {
 300                 if (err != -ENOENT)
 301                         goto out_free;
 302
 303                 if (flags & XATTR_REPLACE)
 304                         /* We are asked not to create the xattr */
 305                         err = -ENODATA;
 306                 else
 307                         err = create_xattr(c, host, &nm, value, size);
 308                 goto out_free;
 309         }
 310
 311         if (flags & XATTR_CREATE) {
 312                 /* We are asked not to replace the xattr */
 313                 err = -EEXIST;
 314                 goto out_free;
 315         }
 316
 317         inode = iget_xattr(c, le64_to_cpu(xent->inum));
 318         if (IS_ERR(inode)) {
 319                 err = PTR_ERR(inode);
 320                 goto out_free;
 321         }
 322
 323         err = change_xattr(c, host, inode, value, size);
 324         iput(inode);
 325
 326 out_free:
 327         kfree(xent);
 328         return err;
 329 }
 330
 331 static ssize_t __ubifs_getxattr(struct inode *host, const char *name,
 332                                 void *buf, size_t size)
 333 {
 334         struct inode *inode;
 335         struct ubifs_info *c = host->i_sb->s_fs_info;
 336         struct qstr nm = QSTR_INIT(name, strlen(name));
 337         struct ubifs_inode *ui;
 338         struct ubifs_dent_node *xent;
 339         union ubifs_key key;
 340         int err;
 341
 342         if (nm.len > UBIFS_MAX_NLEN)
 343                 return -ENAMETOOLONG;
 344
 345         xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
 346         if (!xent)
 347                 return -ENOMEM;
 348
 349         xent_key_init(c, &key, host->i_ino, &nm);
 350         err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
 351         if (err) {
 352                 if (err == -ENOENT)
 353                         err = -ENODATA;
 354                 goto out_unlock;
 355         }
 356
 357         inode = iget_xattr(c, le64_to_cpu(xent->inum));
 358         if (IS_ERR(inode)) {
 359                 err = PTR_ERR(inode);
 360                 goto out_unlock;
 361         }
 362
 363         ui = ubifs_inode(inode);
 364         ubifs_assert(inode->i_size == ui->data_len);
 365         ubifs_assert(ubifs_inode(host)->xattr_size > ui->data_len);
 366
 367         mutex_lock(&ui->ui_mutex);
 368         if (buf) {
 369                 /* If @buf is %NULL we are supposed to return the length */
 370                 if (ui->data_len > size) {
 371                         ubifs_err(c, "buffer size %zd, xattr len %d",
 372                                   size, ui->data_len);
 373                         err = -ERANGE;
 374                         goto out_iput;
 375                 }
 376
 377                 memcpy(buf, ui->data, ui->data_len);
 378         }
 379         err = ui->data_len;
 380
 381 out_iput:
 382         mutex_unlock(&ui->ui_mutex);
 383         iput(inode);
 384 out_unlock:
 385         kfree(xent);
 386         return err;
 387 }
 388
 389 ssize_t ubifs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 390 {
 391         union ubifs_key key;
 392         struct inode *host = d_inode(dentry);
 393         struct ubifs_info *c = host->i_sb->s_fs_info;
 394         struct ubifs_inode *host_ui = ubifs_inode(host);
 395         struct ubifs_dent_node *xent, *pxent = NULL;
 396         int err, len, written = 0;
 397         struct qstr nm = { .name = NULL };
 398
 399         dbg_gen("ino %lu ('%pd'), buffer size %zd", host->i_ino,
 400                 dentry, size);
 401
 402         len = host_ui->xattr_names + host_ui->xattr_cnt;
 403         if (!buffer)
 404                 /*
 405                  * We should return the minimum buffer size which will fit a
 406                  * null-terminated list of all the extended attribute names.
 407                  */
 408                 return len;
 409
 410         if (len > size)
 411                 return -ERANGE;
 412
 413         lowest_xent_key(c, &key, host->i_ino);
 414         while (1) {
 415                 xent = ubifs_tnc_next_ent(c, &key, &nm);
 416                 if (IS_ERR(xent)) {
 417                         err = PTR_ERR(xent);
 418                         break;
 419                 }
 420
 421                 nm.name = xent->name;
 422                 nm.len = le16_to_cpu(xent->nlen);
 423
 424                 /* Show trusted namespace only for "power" users */
 425                 if (strncmp(xent->name, XATTR_TRUSTED_PREFIX,
 426                             XATTR_TRUSTED_PREFIX_LEN) ||
 427                     capable(CAP_SYS_ADMIN)) {
 428                         memcpy(buffer + written, nm.name, nm.len + 1);
 429                         written += nm.len + 1;
 430                 }
 431
 432                 kfree(pxent);
 433                 pxent = xent;
 434                 key_read(c, &xent->key, &key);
 435         }
 436
 437         kfree(pxent);
 438         if (err != -ENOENT) {
 439                 ubifs_err(c, "cannot find next direntry, error %d", err);
 440                 return err;
 441         }
 442
 443         ubifs_assert(written <= size);
 444         return written;
 445 }
 446
 447 static int remove_xattr(struct ubifs_info *c, struct inode *host,
 448                         struct inode *inode, const struct qstr *nm)
 449 {
 450         int err;
 451         struct ubifs_inode *host_ui = ubifs_inode(host);
 452         struct ubifs_inode *ui = ubifs_inode(inode);
 453         struct ubifs_budget_req req = { .dirtied_ino = 2, .mod_dent = 1,
 454                                 .dirtied_ino_d = ALIGN(host_ui->data_len, 8) };
 455
 456         ubifs_assert(ui->data_len == inode->i_size);
 457
 458         err = ubifs_budget_space(c, &req);
 459         if (err)
 460                 return err;
 461
 462         mutex_lock(&host_ui->ui_mutex);
 463         host->i_ctime = ubifs_current_time(host);
 464         host_ui->xattr_cnt -= 1;
 465         host_ui->xattr_size -= CALC_DENT_SIZE(nm->len);
 466         host_ui->xattr_size -= CALC_XATTR_BYTES(ui->data_len);
 467         host_ui->xattr_names -= nm->len;
 468
 469         err = ubifs_jnl_delete_xattr(c, host, inode, nm);
 470         if (err)
 471                 goto out_cancel;
 472         mutex_unlock(&host_ui->ui_mutex);
 473
 474         ubifs_release_budget(c, &req);
 475         return 0;
 476
 477 out_cancel:
 478         host_ui->xattr_cnt += 1;
 479         host_ui->xattr_size += CALC_DENT_SIZE(nm->len);
 480         host_ui->xattr_size += CALC_XATTR_BYTES(ui->data_len);
 481         mutex_unlock(&host_ui->ui_mutex);
 482         ubifs_release_budget(c, &req);
 483         make_bad_inode(inode);
 484         return err;
 485 }
 486
 487 static int __ubifs_removexattr(struct inode *host, const char *name)
 488 {
 489         struct inode *inode;
 490         struct ubifs_info *c = host->i_sb->s_fs_info;
 491         struct qstr nm = QSTR_INIT(name, strlen(name));
 492         struct ubifs_dent_node *xent;
 493         union ubifs_key key;
 494         int err;
 495
 496         ubifs_assert(inode_is_locked(host));
 497
 498         if (nm.len > UBIFS_MAX_NLEN)
 499                 return -ENAMETOOLONG;
 500
 501         xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
 502         if (!xent)
 503                 return -ENOMEM;
 504
 505         xent_key_init(c, &key, host->i_ino, &nm);
 506         err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
 507         if (err) {
 508                 if (err == -ENOENT)
 509                         err = -ENODATA;
 510                 goto out_free;
 511         }
 512
 513         inode = iget_xattr(c, le64_to_cpu(xent->inum));
 514         if (IS_ERR(inode)) {
 515                 err = PTR_ERR(inode);
 516                 goto out_free;
 517         }
 518
 519         ubifs_assert(inode->i_nlink == 1);
 520         clear_nlink(inode);
 521         err = remove_xattr(c, host, inode, &nm);
 522         if (err)
 523                 set_nlink(inode, 1);
 524
 525         /* If @i_nlink is 0, 'iput()' will delete the inode */
 526         iput(inode);
 527
 528 out_free:
 529         kfree(xent);
 530         return err;
 531 }
 532
 533 static int init_xattrs(struct inode *inode, const struct xattr *xattr_array,
 534                       void *fs_info)
 535 {
 536         const struct xattr *xattr;
 537         char *name;
 538         int err = 0;
 539
 540         for (xattr = xattr_array; xattr->name != NULL; xattr++) {
 541                 name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
 542                                strlen(xattr->name) + 1, GFP_NOFS);
 543                 if (!name) {
 544                         err = -ENOMEM;
 545                         break;
 546                 }
 547                 strcpy(name, XATTR_SECURITY_PREFIX);
 548                 strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
 549                 err = __ubifs_setxattr(inode, name, xattr->value, xattr->value_len, 0);
 550                 kfree(name);
 551                 if (err < 0)
 552                         break;
 553         }
 554
 555         return err;
 556 }
 557
 558 int ubifs_init_security(struct inode *dentry, struct inode *inode,
 559                         const struct qstr *qstr)
 560 {
 561         int err;
 562
 563         err = security_inode_init_security(inode, dentry, qstr,
 564                                            &init_xattrs, 0);
 565         if (err) {
 566                 struct ubifs_info *c = dentry->i_sb->s_fs_info;
 567                 ubifs_err(c, "cannot initialize security for inode %lu, error %d",
 568                           inode->i_ino, err);
 569         }
 570         return err;
 571 }
 572
 573 static int ubifs_xattr_get(const struct xattr_handler *handler,
 574                            struct dentry *dentry, struct inode *inode,
 575                            const char *name, void *buffer, size_t size)
 576 {
 577         dbg_gen("xattr '%s', ino %lu ('%pd'), buf size %zd", name,
 578                 inode->i_ino, dentry, size);
 579
 580         name = xattr_full_name(handler, name);
 581         return __ubifs_getxattr(inode, name, buffer, size);
 582 }
 583
 584 static int ubifs_xattr_set(const struct xattr_handler *handler,
 585                            struct dentry *dentry, struct inode *inode,
 586                            const char *name, const void *value,
 587                            size_t size, int flags)
 588 {
 589         dbg_gen("xattr '%s', host ino %lu ('%pd'), size %zd",
 590                 name, inode->i_ino, dentry, size);
 591
 592         name = xattr_full_name(handler, name);
 593
 594         if (value)
 595                 return __ubifs_setxattr(inode, name, value, size, flags);
 596         else
 597                 return __ubifs_removexattr(inode, name);
 598 }
 599
 600 static const struct xattr_handler ubifs_user_xattr_handler = {
 601         .prefix = XATTR_USER_PREFIX,
 602         .get = ubifs_xattr_get,
 603         .set = ubifs_xattr_set,
 604 };
 605
 606 static const struct xattr_handler ubifs_trusted_xattr_handler = {
 607         .prefix = XATTR_TRUSTED_PREFIX,
 608         .get = ubifs_xattr_get,
 609         .set = ubifs_xattr_set,
 610 };
 611
 612 static const struct xattr_handler ubifs_security_xattr_handler = {
 613         .prefix = XATTR_SECURITY_PREFIX,
 614         .get = ubifs_xattr_get,
 615         .set = ubifs_xattr_set,
 616 };
 617
 618 const struct xattr_handler *ubifs_xattr_handlers[] = {
 619         &ubifs_user_xattr_handler,
 620         &ubifs_trusted_xattr_handler,
 621         &ubifs_security_xattr_handler,
 622         NULL
 623 };