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         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 /**
 253  * check_namespace - check extended attribute name-space.
 254  * @nm: extended attribute name
 255  *
 256  * This function makes sure the extended attribute name belongs to one of the
 257  * supported extended attribute name-spaces. Returns name-space index in case
 258  * of success and a negative error code in case of failure.
 259  */
 260 static int check_namespace(const struct qstr *nm)
 261 {
 262         int type;
 263
 264         if (nm->len > UBIFS_MAX_NLEN)
 265                 return -ENAMETOOLONG;
 266
 267         if (!strncmp(nm->name, XATTR_TRUSTED_PREFIX,
 268                      XATTR_TRUSTED_PREFIX_LEN)) {
 269                 if (nm->name[XATTR_TRUSTED_PREFIX_LEN] == '\0')
 270                         return -EINVAL;
 271                 type = TRUSTED_XATTR;
 272         } else if (!strncmp(nm->name, XATTR_USER_PREFIX,
 273                                       XATTR_USER_PREFIX_LEN)) {
 274                 if (nm->name[XATTR_USER_PREFIX_LEN] == '\0')
 275                         return -EINVAL;
 276                 type = USER_XATTR;
 277         } else if (!strncmp(nm->name, XATTR_SECURITY_PREFIX,
 278                                      XATTR_SECURITY_PREFIX_LEN)) {
 279                 if (nm->name[XATTR_SECURITY_PREFIX_LEN] == '\0')
 280                         return -EINVAL;
 281                 type = SECURITY_XATTR;
 282         } else
 283                 return -EOPNOTSUPP;
 284
 285         return type;
 286 }
 287
 288 static struct inode *iget_xattr(struct ubifs_info *c, ino_t inum)
 289 {
 290         struct inode *inode;
 291
 292         inode = ubifs_iget(c->vfs_sb, inum);
 293         if (IS_ERR(inode)) {
 294                 ubifs_err(c, "dead extended attribute entry, error %d",
 295                           (int)PTR_ERR(inode));
 296                 return inode;
 297         }
 298         if (ubifs_inode(inode)->xattr)
 299                 return inode;
 300         ubifs_err(c, "corrupt extended attribute entry");
 301         iput(inode);
 302         return ERR_PTR(-EINVAL);
 303 }
 304
 305 static int setxattr(struct inode *host, const char *name, const void *value,
 306                     size_t size, int flags)
 307 {
 308         struct inode *inode;
 309         struct ubifs_info *c = host->i_sb->s_fs_info;
 310         struct qstr nm = QSTR_INIT(name, strlen(name));
 311         struct ubifs_dent_node *xent;
 312         union ubifs_key key;
 313         int err, type;
 314
 315         ubifs_assert(inode_is_locked(host));
 316
 317         if (size > UBIFS_MAX_INO_DATA)
 318                 return -ERANGE;
 319
 320         type = check_namespace(&nm);
 321         if (type < 0)
 322                 return type;
 323
 324         xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
 325         if (!xent)
 326                 return -ENOMEM;
 327
 328         /*
 329          * The extended attribute entries are stored in LNC, so multiple
 330          * look-ups do not involve reading the flash.
 331          */
 332         xent_key_init(c, &key, host->i_ino, &nm);
 333         err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
 334         if (err) {
 335                 if (err != -ENOENT)
 336                         goto out_free;
 337
 338                 if (flags & XATTR_REPLACE)
 339                         /* We are asked not to create the xattr */
 340                         err = -ENODATA;
 341                 else
 342                         err = create_xattr(c, host, &nm, value, size);
 343                 goto out_free;
 344         }
 345
 346         if (flags & XATTR_CREATE) {
 347                 /* We are asked not to replace the xattr */
 348                 err = -EEXIST;
 349                 goto out_free;
 350         }
 351
 352         inode = iget_xattr(c, le64_to_cpu(xent->inum));
 353         if (IS_ERR(inode)) {
 354                 err = PTR_ERR(inode);
 355                 goto out_free;
 356         }
 357
 358         err = change_xattr(c, host, inode, value, size);
 359         iput(inode);
 360
 361 out_free:
 362         kfree(xent);
 363         return err;
 364 }
 365
 366 int ubifs_setxattr(struct dentry *dentry, const char *name,
 367                    const void *value, size_t size, int flags)
 368 {
 369         dbg_gen("xattr '%s', host ino %lu ('%pd'), size %zd",
 370                 name, d_inode(dentry)->i_ino, dentry, size);
 371
 372         return setxattr(d_inode(dentry), name, value, size, flags);
 373 }
 374
 375 ssize_t ubifs_getxattr(struct dentry *dentry, const char *name, void *buf,
 376                        size_t size)
 377 {
 378         struct inode *inode, *host = d_inode(dentry);
 379         struct ubifs_info *c = host->i_sb->s_fs_info;
 380         struct qstr nm = QSTR_INIT(name, strlen(name));
 381         struct ubifs_inode *ui;
 382         struct ubifs_dent_node *xent;
 383         union ubifs_key key;
 384         int err;
 385
 386         dbg_gen("xattr '%s', ino %lu ('%pd'), buf size %zd", name,
 387                 host->i_ino, dentry, size);
 388
 389         err = check_namespace(&nm);
 390         if (err < 0)
 391                 return err;
 392
 393         xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
 394         if (!xent)
 395                 return -ENOMEM;
 396
 397         xent_key_init(c, &key, host->i_ino, &nm);
 398         err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
 399         if (err) {
 400                 if (err == -ENOENT)
 401                         err = -ENODATA;
 402                 goto out_unlock;
 403         }
 404
 405         inode = iget_xattr(c, le64_to_cpu(xent->inum));
 406         if (IS_ERR(inode)) {
 407                 err = PTR_ERR(inode);
 408                 goto out_unlock;
 409         }
 410
 411         ui = ubifs_inode(inode);
 412         ubifs_assert(inode->i_size == ui->data_len);
 413         ubifs_assert(ubifs_inode(host)->xattr_size > ui->data_len);
 414
 415         mutex_lock(&ui->ui_mutex);
 416         if (buf) {
 417                 /* If @buf is %NULL we are supposed to return the length */
 418                 if (ui->data_len > size) {
 419                         ubifs_err(c, "buffer size %zd, xattr len %d",
 420                                   size, ui->data_len);
 421                         err = -ERANGE;
 422                         goto out_iput;
 423                 }
 424
 425                 memcpy(buf, ui->data, ui->data_len);
 426         }
 427         err = ui->data_len;
 428
 429 out_iput:
 430         mutex_unlock(&ui->ui_mutex);
 431         iput(inode);
 432 out_unlock:
 433         kfree(xent);
 434         return err;
 435 }
 436
 437 ssize_t ubifs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 438 {
 439         union ubifs_key key;
 440         struct inode *host = d_inode(dentry);
 441         struct ubifs_info *c = host->i_sb->s_fs_info;
 442         struct ubifs_inode *host_ui = ubifs_inode(host);
 443         struct ubifs_dent_node *xent, *pxent = NULL;
 444         int err, len, written = 0;
 445         struct qstr nm = { .name = NULL };
 446
 447         dbg_gen("ino %lu ('%pd'), buffer size %zd", host->i_ino,
 448                 dentry, size);
 449
 450         len = host_ui->xattr_names + host_ui->xattr_cnt;
 451         if (!buffer)
 452                 /*
 453                  * We should return the minimum buffer size which will fit a
 454                  * null-terminated list of all the extended attribute names.
 455                  */
 456                 return len;
 457
 458         if (len > size)
 459                 return -ERANGE;
 460
 461         lowest_xent_key(c, &key, host->i_ino);
 462         while (1) {
 463                 int type;
 464
 465                 xent = ubifs_tnc_next_ent(c, &key, &nm);
 466                 if (IS_ERR(xent)) {
 467                         err = PTR_ERR(xent);
 468                         break;
 469                 }
 470
 471                 nm.name = xent->name;
 472                 nm.len = le16_to_cpu(xent->nlen);
 473
 474                 type = check_namespace(&nm);
 475                 if (unlikely(type < 0)) {
 476                         err = type;
 477                         break;
 478                 }
 479
 480                 /* Show trusted namespace only for "power" users */
 481                 if (type != TRUSTED_XATTR || capable(CAP_SYS_ADMIN)) {
 482                         memcpy(buffer + written, nm.name, nm.len + 1);
 483                         written += nm.len + 1;
 484                 }
 485
 486                 kfree(pxent);
 487                 pxent = xent;
 488                 key_read(c, &xent->key, &key);
 489         }
 490
 491         kfree(pxent);
 492         if (err != -ENOENT) {
 493                 ubifs_err(c, "cannot find next direntry, error %d", err);
 494                 return err;
 495         }
 496
 497         ubifs_assert(written <= size);
 498         return written;
 499 }
 500
 501 static int remove_xattr(struct ubifs_info *c, struct inode *host,
 502                         struct inode *inode, const struct qstr *nm)
 503 {
 504         int err;
 505         struct ubifs_inode *host_ui = ubifs_inode(host);
 506         struct ubifs_inode *ui = ubifs_inode(inode);
 507         struct ubifs_budget_req req = { .dirtied_ino = 2, .mod_dent = 1,
 508                                 .dirtied_ino_d = ALIGN(host_ui->data_len, 8) };
 509
 510         ubifs_assert(ui->data_len == inode->i_size);
 511
 512         err = ubifs_budget_space(c, &req);
 513         if (err)
 514                 return err;
 515
 516         mutex_lock(&host_ui->ui_mutex);
 517         host->i_ctime = ubifs_current_time(host);
 518         host_ui->xattr_cnt -= 1;
 519         host_ui->xattr_size -= CALC_DENT_SIZE(nm->len);
 520         host_ui->xattr_size -= CALC_XATTR_BYTES(ui->data_len);
 521         host_ui->xattr_names -= nm->len;
 522
 523         err = ubifs_jnl_delete_xattr(c, host, inode, nm);
 524         if (err)
 525                 goto out_cancel;
 526         mutex_unlock(&host_ui->ui_mutex);
 527
 528         ubifs_release_budget(c, &req);
 529         return 0;
 530
 531 out_cancel:
 532         host_ui->xattr_cnt += 1;
 533         host_ui->xattr_size += CALC_DENT_SIZE(nm->len);
 534         host_ui->xattr_size += CALC_XATTR_BYTES(ui->data_len);
 535         mutex_unlock(&host_ui->ui_mutex);
 536         ubifs_release_budget(c, &req);
 537         make_bad_inode(inode);
 538         return err;
 539 }
 540
 541 int ubifs_removexattr(struct dentry *dentry, const char *name)
 542 {
 543         struct inode *inode, *host = d_inode(dentry);
 544         struct ubifs_info *c = host->i_sb->s_fs_info;
 545         struct qstr nm = QSTR_INIT(name, strlen(name));
 546         struct ubifs_dent_node *xent;
 547         union ubifs_key key;
 548         int err;
 549
 550         dbg_gen("xattr '%s', ino %lu ('%pd')", name,
 551                 host->i_ino, dentry);
 552         ubifs_assert(inode_is_locked(host));
 553
 554         err = check_namespace(&nm);
 555         if (err < 0)
 556                 return err;
 557
 558         xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
 559         if (!xent)
 560                 return -ENOMEM;
 561
 562         xent_key_init(c, &key, host->i_ino, &nm);
 563         err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
 564         if (err) {
 565                 if (err == -ENOENT)
 566                         err = -ENODATA;
 567                 goto out_free;
 568         }
 569
 570         inode = iget_xattr(c, le64_to_cpu(xent->inum));
 571         if (IS_ERR(inode)) {
 572                 err = PTR_ERR(inode);
 573                 goto out_free;
 574         }
 575
 576         ubifs_assert(inode->i_nlink == 1);
 577         clear_nlink(inode);
 578         err = remove_xattr(c, host, inode, &nm);
 579         if (err)
 580                 set_nlink(inode, 1);
 581
 582         /* If @i_nlink is 0, 'iput()' will delete the inode */
 583         iput(inode);
 584
 585 out_free:
 586         kfree(xent);
 587         return err;
 588 }
 589
 590 static int init_xattrs(struct inode *inode, const struct xattr *xattr_array,
 591                       void *fs_info)
 592 {
 593         const struct xattr *xattr;
 594         char *name;
 595         int err = 0;
 596
 597         for (xattr = xattr_array; xattr->name != NULL; xattr++) {
 598                 name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
 599                                strlen(xattr->name) + 1, GFP_NOFS);
 600                 if (!name) {
 601                         err = -ENOMEM;
 602                         break;
 603                 }
 604                 strcpy(name, XATTR_SECURITY_PREFIX);
 605                 strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
 606                 err = setxattr(inode, name, xattr->value, xattr->value_len, 0);
 607                 kfree(name);
 608                 if (err < 0)
 609                         break;
 610         }
 611
 612         return err;
 613 }
 614
 615 int ubifs_init_security(struct inode *dentry, struct inode *inode,
 616                         const struct qstr *qstr)
 617 {
 618         int err;
 619
 620         err = security_inode_init_security(inode, dentry, qstr,
 621                                            &init_xattrs, 0);
 622         if (err) {
 623                 struct ubifs_info *c = dentry->i_sb->s_fs_info;
 624                 ubifs_err(c, "cannot initialize security for inode %lu, error %d",
 625                           inode->i_ino, err);
 626         }
 627         return err;
 628 }