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