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 #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  */
 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         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         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         ui->data_len = size;
 222         mutex_unlock(&ui->ui_mutex);
 223
 224         mutex_lock(&host_ui->ui_mutex);
 225         host->i_ctime = ubifs_current_time(host);
 226         host_ui->xattr_size -= CALC_XATTR_BYTES(ui->data_len);
 227         host_ui->xattr_size += CALC_XATTR_BYTES(size);
 228
 229         /*
 230          * It is important to write the host inode after the xattr inode
 231          * because if the host inode gets synchronized (via 'fsync()'), then
 232          * the extended attribute inode gets synchronized, because it goes
 233          * before the host inode in the write-buffer.
 234          */
 235         err = ubifs_jnl_change_xattr(c, inode, host);
 236         if (err)
 237                 goto out_cancel;
 238         mutex_unlock(&host_ui->ui_mutex);
 239
 240         ubifs_release_budget(c, &req);
 241         return 0;
 242
 243 out_cancel:
 244         host_ui->xattr_size -= CALC_XATTR_BYTES(size);
 245         host_ui->xattr_size += CALC_XATTR_BYTES(ui->data_len);
 246         mutex_unlock(&host_ui->ui_mutex);
 247         make_bad_inode(inode);
 248 out_free:
 249         ubifs_release_budget(c, &req);
 250         return err;
 251 }
 252
 253 /**
 254  * check_namespace - check extended attribute name-space.
 255  * @nm: extended attribute name
 256  *
 257  * This function makes sure the extended attribute name belongs to one of the
 258  * supported extended attribute name-spaces. Returns name-space index in case
 259  * of success and a negative error code in case of failure.
 260  */
 261 static int check_namespace(const struct qstr *nm)
 262 {
 263         int type;
 264
 265         if (nm->len > UBIFS_MAX_NLEN)
 266                 return -ENAMETOOLONG;
 267
 268         if (!strncmp(nm->name, XATTR_TRUSTED_PREFIX,
 269                      XATTR_TRUSTED_PREFIX_LEN)) {
 270                 if (nm->name[sizeof(XATTR_TRUSTED_PREFIX) - 1] == '\0')
 271                         return -EINVAL;
 272                 type = TRUSTED_XATTR;
 273         } else if (!strncmp(nm->name, XATTR_USER_PREFIX,
 274                                       XATTR_USER_PREFIX_LEN)) {
 275                 if (nm->name[XATTR_USER_PREFIX_LEN] == '\0')
 276                         return -EINVAL;
 277                 type = USER_XATTR;
 278         } else if (!strncmp(nm->name, XATTR_SECURITY_PREFIX,
 279                                      XATTR_SECURITY_PREFIX_LEN)) {
 280                 if (nm->name[sizeof(XATTR_SECURITY_PREFIX) - 1] == '\0')
 281                         return -EINVAL;
 282                 type = SECURITY_XATTR;
 283         } else
 284                 return -EOPNOTSUPP;
 285
 286         return type;
 287 }
 288
 289 static struct inode *iget_xattr(struct ubifs_info *c, ino_t inum)
 290 {
 291         struct inode *inode;
 292
 293         inode = ubifs_iget(c->vfs_sb, inum);
 294         if (IS_ERR(inode)) {
 295                 ubifs_err(c, "dead extended attribute entry, error %d",
 296                           (int)PTR_ERR(inode));
 297                 return inode;
 298         }
 299         if (ubifs_inode(inode)->xattr)
 300                 return inode;
 301         ubifs_err(c, "corrupt extended attribute entry");
 302         iput(inode);
 303         return ERR_PTR(-EINVAL);
 304 }
 305
 306 static int setxattr(struct inode *host, const char *name, const void *value,
 307                     size_t size, int flags)
 308 {
 309         struct inode *inode;
 310         struct ubifs_info *c = host->i_sb->s_fs_info;
 311         struct qstr nm = QSTR_INIT(name, strlen(name));
 312         struct ubifs_dent_node *xent;
 313         union ubifs_key key;
 314         int err, type;
 315
 316         ubifs_assert(mutex_is_locked(&host->i_mutex));
 317
 318         if (size > UBIFS_MAX_INO_DATA)
 319                 return -ERANGE;
 320
 321         type = check_namespace(&nm);
 322         if (type < 0)
 323                 return type;
 324
 325         xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
 326         if (!xent)
 327                 return -ENOMEM;
 328
 329         /*
 330          * The extended attribute entries are stored in LNC, so multiple
 331          * look-ups do not involve reading the flash.
 332          */
 333         xent_key_init(c, &key, host->i_ino, &nm);
 334         err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
 335         if (err) {
 336                 if (err != -ENOENT)
 337                         goto out_free;
 338
 339                 if (flags & XATTR_REPLACE)
 340                         /* We are asked not to create the xattr */
 341                         err = -ENODATA;
 342                 else
 343                         err = create_xattr(c, host, &nm, value, size);
 344                 goto out_free;
 345         }
 346
 347         if (flags & XATTR_CREATE) {
 348                 /* We are asked not to replace the xattr */
 349                 err = -EEXIST;
 350                 goto out_free;
 351         }
 352
 353         inode = iget_xattr(c, le64_to_cpu(xent->inum));
 354         if (IS_ERR(inode)) {
 355                 err = PTR_ERR(inode);
 356                 goto out_free;
 357         }
 358
 359         err = change_xattr(c, host, inode, value, size);
 360         iput(inode);
 361
 362 out_free:
 363         kfree(xent);
 364         return err;
 365 }
 366
 367 int ubifs_setxattr(struct dentry *dentry, const char *name,
 368                    const void *value, size_t size, int flags)
 369 {
 370         dbg_gen("xattr '%s', host ino %lu ('%pd'), size %zd",
 371                 name, d_inode(dentry)->i_ino, dentry, size);
 372
 373         return setxattr(d_inode(dentry), name, value, size, flags);
 374 }
 375
 376 ssize_t ubifs_getxattr(struct dentry *dentry, const char *name, void *buf,
 377                        size_t size)
 378 {
 379         struct inode *inode, *host = d_inode(dentry);
 380         struct ubifs_info *c = host->i_sb->s_fs_info;
 381         struct qstr nm = QSTR_INIT(name, strlen(name));
 382         struct ubifs_inode *ui;
 383         struct ubifs_dent_node *xent;
 384         union ubifs_key key;
 385         int err;
 386
 387         dbg_gen("xattr '%s', ino %lu ('%pd'), buf size %zd", name,
 388                 host->i_ino, dentry, size);
 389
 390         err = check_namespace(&nm);
 391         if (err < 0)
 392                 return err;
 393
 394         xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
 395         if (!xent)
 396                 return -ENOMEM;
 397
 398         xent_key_init(c, &key, host->i_ino, &nm);
 399         err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
 400         if (err) {
 401                 if (err == -ENOENT)
 402                         err = -ENODATA;
 403                 goto out_unlock;
 404         }
 405
 406         inode = iget_xattr(c, le64_to_cpu(xent->inum));
 407         if (IS_ERR(inode)) {
 408                 err = PTR_ERR(inode);
 409                 goto out_unlock;
 410         }
 411
 412         ui = ubifs_inode(inode);
 413         ubifs_assert(inode->i_size == ui->data_len);
 414         ubifs_assert(ubifs_inode(host)->xattr_size > ui->data_len);
 415
 416         mutex_lock(&ui->ui_mutex);
 417         if (buf) {
 418                 /* If @buf is %NULL we are supposed to return the length */
 419                 if (ui->data_len > size) {
 420                         ubifs_err(c, "buffer size %zd, xattr len %d",
 421                                   size, ui->data_len);
 422                         err = -ERANGE;
 423                         goto out_iput;
 424                 }
 425
 426                 memcpy(buf, ui->data, ui->data_len);
 427         }
 428         err = ui->data_len;
 429
 430 out_iput:
 431         mutex_unlock(&ui->ui_mutex);
 432         iput(inode);
 433 out_unlock:
 434         kfree(xent);
 435         return err;
 436 }
 437
 438 ssize_t ubifs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 439 {
 440         union ubifs_key key;
 441         struct inode *host = d_inode(dentry);
 442         struct ubifs_info *c = host->i_sb->s_fs_info;
 443         struct ubifs_inode *host_ui = ubifs_inode(host);
 444         struct ubifs_dent_node *xent, *pxent = NULL;
 445         int err, len, written = 0;
 446         struct qstr nm = { .name = NULL };
 447
 448         dbg_gen("ino %lu ('%pd'), buffer size %zd", host->i_ino,
 449                 dentry, size);
 450
 451         len = host_ui->xattr_names + host_ui->xattr_cnt;
 452         if (!buffer)
 453                 /*
 454                  * We should return the minimum buffer size which will fit a
 455                  * null-terminated list of all the extended attribute names.
 456                  */
 457                 return len;
 458
 459         if (len > size)
 460                 return -ERANGE;
 461
 462         lowest_xent_key(c, &key, host->i_ino);
 463         while (1) {
 464                 int type;
 465
 466                 xent = ubifs_tnc_next_ent(c, &key, &nm);
 467                 if (IS_ERR(xent)) {
 468                         err = PTR_ERR(xent);
 469                         break;
 470                 }
 471
 472                 nm.name = xent->name;
 473                 nm.len = le16_to_cpu(xent->nlen);
 474
 475                 type = check_namespace(&nm);
 476                 if (unlikely(type < 0)) {
 477                         err = type;
 478                         break;
 479                 }
 480
 481                 /* Show trusted namespace only for "power" users */
 482                 if (type != TRUSTED_XATTR || capable(CAP_SYS_ADMIN)) {
 483                         memcpy(buffer + written, nm.name, nm.len + 1);
 484                         written += nm.len + 1;
 485                 }
 486
 487                 kfree(pxent);
 488                 pxent = xent;
 489                 key_read(c, &xent->key, &key);
 490         }
 491
 492         kfree(pxent);
 493         if (err != -ENOENT) {
 494                 ubifs_err(c, "cannot find next direntry, error %d", err);
 495                 return err;
 496         }
 497
 498         ubifs_assert(written <= size);
 499         return written;
 500 }
 501
 502 static int remove_xattr(struct ubifs_info *c, struct inode *host,
 503                         struct inode *inode, const struct qstr *nm)
 504 {
 505         int err;
 506         struct ubifs_inode *host_ui = ubifs_inode(host);
 507         struct ubifs_inode *ui = ubifs_inode(inode);
 508         struct ubifs_budget_req req = { .dirtied_ino = 2, .mod_dent = 1,
 509                                 .dirtied_ino_d = ALIGN(host_ui->data_len, 8) };
 510
 511         ubifs_assert(ui->data_len == inode->i_size);
 512
 513         err = ubifs_budget_space(c, &req);
 514         if (err)
 515                 return err;
 516
 517         mutex_lock(&host_ui->ui_mutex);
 518         host->i_ctime = ubifs_current_time(host);
 519         host_ui->xattr_cnt -= 1;
 520         host_ui->xattr_size -= CALC_DENT_SIZE(nm->len);
 521         host_ui->xattr_size -= CALC_XATTR_BYTES(ui->data_len);
 522         host_ui->xattr_names -= nm->len;
 523
 524         err = ubifs_jnl_delete_xattr(c, host, inode, nm);
 525         if (err)
 526                 goto out_cancel;
 527         mutex_unlock(&host_ui->ui_mutex);
 528
 529         ubifs_release_budget(c, &req);
 530         return 0;
 531
 532 out_cancel:
 533         host_ui->xattr_cnt += 1;
 534         host_ui->xattr_size += CALC_DENT_SIZE(nm->len);
 535         host_ui->xattr_size += CALC_XATTR_BYTES(ui->data_len);
 536         mutex_unlock(&host_ui->ui_mutex);
 537         ubifs_release_budget(c, &req);
 538         make_bad_inode(inode);
 539         return err;
 540 }
 541
 542 int ubifs_removexattr(struct dentry *dentry, const char *name)
 543 {
 544         struct inode *inode, *host = d_inode(dentry);
 545         struct ubifs_info *c = host->i_sb->s_fs_info;
 546         struct qstr nm = QSTR_INIT(name, strlen(name));
 547         struct ubifs_dent_node *xent;
 548         union ubifs_key key;
 549         int err;
 550
 551         dbg_gen("xattr '%s', ino %lu ('%pd')", name,
 552                 host->i_ino, dentry);
 553         ubifs_assert(mutex_is_locked(&host->i_mutex));
 554
 555         err = check_namespace(&nm);
 556         if (err < 0)
 557                 return err;
 558
 559         xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
 560         if (!xent)
 561                 return -ENOMEM;
 562
 563         xent_key_init(c, &key, host->i_ino, &nm);
 564         err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
 565         if (err) {
 566                 if (err == -ENOENT)
 567                         err = -ENODATA;
 568                 goto out_free;
 569         }
 570
 571         inode = iget_xattr(c, le64_to_cpu(xent->inum));
 572         if (IS_ERR(inode)) {
 573                 err = PTR_ERR(inode);
 574                 goto out_free;
 575         }
 576
 577         ubifs_assert(inode->i_nlink == 1);
 578         clear_nlink(inode);
 579         err = remove_xattr(c, host, inode, &nm);
 580         if (err)
 581                 set_nlink(inode, 1);
 582
 583         /* If @i_nlink is 0, 'iput()' will delete the inode */
 584         iput(inode);
 585
 586 out_free:
 587         kfree(xent);
 588         return err;
 589 }
 590
 591 static int init_xattrs(struct inode *inode, const struct xattr *xattr_array,
 592                       void *fs_info)
 593 {
 594         const struct xattr *xattr;
 595         char *name;
 596         int err = 0;
 597
 598         for (xattr = xattr_array; xattr->name != NULL; xattr++) {
 599                 name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
 600                                strlen(xattr->name) + 1, GFP_NOFS);
 601                 if (!name) {
 602                         err = -ENOMEM;
 603                         break;
 604                 }
 605                 strcpy(name, XATTR_SECURITY_PREFIX);
 606                 strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
 607                 err = setxattr(inode, name, xattr->value, xattr->value_len, 0);
 608                 kfree(name);
 609                 if (err < 0)
 610                         break;
 611         }
 612
 613         return err;
 614 }
 615
 616 int ubifs_init_security(struct inode *dentry, struct inode *inode,
 617                         const struct qstr *qstr)
 618 {
 619         int err;
 620
 621         err = security_inode_init_security(inode, dentry, qstr,
 622                                            &init_xattrs, 0);
 623         if (err) {
 624                 struct ubifs_info *c = dentry->i_sb->s_fs_info;
 625                 ubifs_err(c, "cannot initialize security for inode %lu, error %d",
 626                           inode->i_ino, err);
 627         }
 628         return err;
 629 }