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         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 };