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