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 <linux/xattr.h>
  59 #include <linux/posix_acl_xattr.h>
  60 #include "ubifs.h"
  61
  62 /*
  63  * Limit the number of extended attributes per inode so that the total size
  64  * (xattr_size) is guaranteeded to fit in an 'unsigned int'.
  65  */
  66 #define MAX_XATTRS_PER_INODE 65535
  67
  68 /*
  69  * Extended attribute type constants.
  70  *
  71  * USER_XATTR: user extended attribute ("user.*")
  72  * TRUSTED_XATTR: trusted extended attribute ("trusted.*)
  73  * SECURITY_XATTR: security extended attribute ("security.*")
  74  */
  75 enum {
  76         USER_XATTR,
  77         TRUSTED_XATTR,
  78         SECURITY_XATTR,
  79 };
  80
  81 static struct inode_operations none_inode_operations;
  82 static struct address_space_operations none_address_operations;
  83 static struct file_operations none_file_operations;
  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;
 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 = size, .dirtied_ino = 1,
 107                                         .dirtied_ino_d = host_ui->data_len};
 108
 109         if (host_ui->xattr_cnt >= MAX_XATTRS_PER_INODE)
 110                 return -ENOSPC;
 111         /*
 112          * Linux limits the maximum size of the extended attribute names list
 113          * to %XATTR_LIST_MAX. This means we should not allow creating more*
 114          * extended attributes if the name list becomes larger. This limitation
 115          * is artificial for UBIFS, though.
 116          */
 117         if (host_ui->xattr_names + host_ui->xattr_cnt +
 118                                         nm->len + 1 > XATTR_LIST_MAX)
 119                 return -ENOSPC;
 120
 121         err = ubifs_budget_space(c, &req);
 122         if (err)
 123                 return err;
 124
 125         inode = ubifs_new_inode(c, host, S_IFREG | S_IRWXUGO);
 126         if (IS_ERR(inode)) {
 127                 err = PTR_ERR(inode);
 128                 goto out_budg;
 129         }
 130
 131         mutex_lock(&host_ui->ui_mutex);
 132         /* Re-define all operations to be "nothing" */
 133         inode->i_mapping->a_ops = &none_address_operations;
 134         inode->i_op = &none_inode_operations;
 135         inode->i_fop = &none_file_operations;
 136
 137         inode->i_flags |= S_SYNC | S_NOATIME | S_NOCMTIME | S_NOQUOTA;
 138         ui = ubifs_inode(inode);
 139         ui->xattr = 1;
 140         ui->flags |= UBIFS_XATTR_FL;
 141         ui->data = kmalloc(size, GFP_NOFS);
 142         if (!ui->data) {
 143                 err = -ENOMEM;
 144                 goto out_unlock;
 145         }
 146
 147         memcpy(ui->data, value, size);
 148         host->i_ctime = ubifs_current_time(host);
 149         host_ui->xattr_cnt += 1;
 150         host_ui->xattr_size += CALC_DENT_SIZE(nm->len);
 151         host_ui->xattr_size += CALC_XATTR_BYTES(size);
 152         host_ui->xattr_names += nm->len;
 153
 154         /*
 155          * We do not use i_size_write() because nobody can race with us as we
 156          * are holding host @host->i_mutex - every xattr operation for this
 157          * inode is serialized by it.
 158          */
 159         inode->i_size = ui->ui_size = size;
 160         ui->data_len = size;
 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 out_unlock:
 176         mutex_unlock(&host_ui->ui_mutex);
 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         struct ubifs_budget_req req = { .dirtied_ino = 2,
 203                                 .dirtied_ino_d = size + host_ui->data_len };
 204
 205         ubifs_assert(ui->data_len == inode->i_size);
 206         err = ubifs_budget_space(c, &req);
 207         if (err)
 208                 return err;
 209
 210         mutex_lock(&host_ui->ui_mutex);
 211         host->i_ctime = ubifs_current_time(host);
 212         host_ui->xattr_size -= CALC_XATTR_BYTES(ui->data_len);
 213         host_ui->xattr_size += CALC_XATTR_BYTES(size);
 214
 215         kfree(ui->data);
 216         ui->data = kmalloc(size, GFP_NOFS);
 217         if (!ui->data) {
 218                 err = -ENOMEM;
 219                 goto out_unlock;
 220         }
 221
 222         memcpy(ui->data, value, size);
 223         inode->i_size = ui->ui_size = size;
 224         ui->data_len = size;
 225
 226         /*
 227          * It is important to write the host inode after the xattr inode
 228          * because if the host inode gets synchronized (via 'fsync()'), then
 229          * the extended attribute inode gets synchronized, because it goes
 230          * before the host inode in the write-buffer.
 231          */
 232         err = ubifs_jnl_change_xattr(c, inode, host);
 233         if (err)
 234                 goto out_cancel;
 235         mutex_unlock(&host_ui->ui_mutex);
 236
 237         ubifs_release_budget(c, &req);
 238         return 0;
 239
 240 out_cancel:
 241         host_ui->xattr_size -= CALC_XATTR_BYTES(size);
 242         host_ui->xattr_size += CALC_XATTR_BYTES(ui->data_len);
 243         make_bad_inode(inode);
 244 out_unlock:
 245         mutex_unlock(&host_ui->ui_mutex);
 246         ubifs_release_budget(c, &req);
 247         return err;
 248 }
 249
 250 /**
 251  * check_namespace - check extended attribute name-space.
 252  * @nm: extended attribute name
 253  *
 254  * This function makes sure the extended attribute name belongs to one of the
 255  * supported extended attribute name-spaces. Returns name-space index in case
 256  * of success and a negative error code in case of failure.
 257  */
 258 static int check_namespace(const struct qstr *nm)
 259 {
 260         int type;
 261
 262         if (nm->len > UBIFS_MAX_NLEN)
 263                 return -ENAMETOOLONG;
 264
 265         if (!strncmp(nm->name, XATTR_TRUSTED_PREFIX,
 266                      XATTR_TRUSTED_PREFIX_LEN)) {
 267                 if (nm->name[sizeof(XATTR_TRUSTED_PREFIX) - 1] == '\0')
 268                         return -EINVAL;
 269                 type = TRUSTED_XATTR;
 270         } else if (!strncmp(nm->name, XATTR_USER_PREFIX,
 271                                       XATTR_USER_PREFIX_LEN)) {
 272                 if (nm->name[XATTR_USER_PREFIX_LEN] == '\0')
 273                         return -EINVAL;
 274                 type = USER_XATTR;
 275         } else if (!strncmp(nm->name, XATTR_SECURITY_PREFIX,
 276                                      XATTR_SECURITY_PREFIX_LEN)) {
 277                 if (nm->name[sizeof(XATTR_SECURITY_PREFIX) - 1] == '\0')
 278                         return -EINVAL;
 279                 type = SECURITY_XATTR;
 280         } else
 281                 return -EOPNOTSUPP;
 282
 283         return type;
 284 }
 285
 286 static struct inode *iget_xattr(struct ubifs_info *c, ino_t inum)
 287 {
 288         struct inode *inode;
 289
 290         inode = ubifs_iget(c->vfs_sb, inum);
 291         if (IS_ERR(inode)) {
 292                 ubifs_err("dead extended attribute entry, error %d",
 293                           (int)PTR_ERR(inode));
 294                 return inode;
 295         }
 296         if (ubifs_inode(inode)->xattr)
 297                 return inode;
 298         ubifs_err("corrupt extended attribute entry");
 299         iput(inode);
 300         return ERR_PTR(-EINVAL);
 301 }
 302
 303 int ubifs_setxattr(struct dentry *dentry, const char *name,
 304                    const void *value, size_t size, int flags)
 305 {
 306         struct inode *inode, *host = dentry->d_inode;
 307         struct ubifs_info *c = host->i_sb->s_fs_info;
 308         struct qstr nm = { .name = name, .len = strlen(name) };
 309         struct ubifs_dent_node *xent;
 310         union ubifs_key key;
 311         int err, type;
 312
 313         dbg_gen("xattr '%s', host ino %lu ('%.*s'), size %zd", name,
 314                 host->i_ino, dentry->d_name.len, dentry->d_name.name, size);
 315
 316         if (size > UBIFS_MAX_INO_DATA)
 317                 return -ERANGE;
 318
 319         type = check_namespace(&nm);
 320         if (type < 0)
 321                 return type;
 322
 323         xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
 324         if (!xent)
 325                 return -ENOMEM;
 326
 327         /*
 328          * The extended attribute entries are stored in LNC, so multiple
 329          * look-ups do not involve reading the flash.
 330          */
 331         xent_key_init(c, &key, host->i_ino, &nm);
 332         err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
 333         if (err) {
 334                 if (err != -ENOENT)
 335                         goto out_free;
 336
 337                 if (flags & XATTR_REPLACE)
 338                         /* We are asked not to create the xattr */
 339                         err = -ENODATA;
 340                 else
 341                         err = create_xattr(c, host, &nm, value, size);
 342                 goto out_free;
 343         }
 344
 345         if (flags & XATTR_CREATE) {
 346                 /* We are asked not to replace the xattr */
 347                 err = -EEXIST;
 348                 goto out_free;
 349         }
 350
 351         inode = iget_xattr(c, le64_to_cpu(xent->inum));
 352         if (IS_ERR(inode)) {
 353                 err = PTR_ERR(inode);
 354                 goto out_free;
 355         }
 356
 357         err = change_xattr(c, host, inode, value, size);
 358         iput(inode);
 359
 360 out_free:
 361         kfree(xent);
 362         return err;
 363 }
 364
 365 ssize_t ubifs_getxattr(struct dentry *dentry, const char *name, void *buf,
 366                        size_t size)
 367 {
 368         struct inode *inode, *host = dentry->d_inode;
 369         struct ubifs_info *c = host->i_sb->s_fs_info;
 370         struct qstr nm = { .name = name, .len = strlen(name) };
 371         struct ubifs_inode *ui;
 372         struct ubifs_dent_node *xent;
 373         union ubifs_key key;
 374         int err;
 375
 376         dbg_gen("xattr '%s', ino %lu ('%.*s'), buf size %zd", name,
 377                 host->i_ino, dentry->d_name.len, dentry->d_name.name, size);
 378
 379         err = check_namespace(&nm);
 380         if (err < 0)
 381                 return err;
 382
 383         xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
 384         if (!xent)
 385                 return -ENOMEM;
 386
 387         mutex_lock(&host->i_mutex);
 388         xent_key_init(c, &key, host->i_ino, &nm);
 389         err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
 390         if (err) {
 391                 if (err == -ENOENT)
 392                         err = -ENODATA;
 393                 goto out_unlock;
 394         }
 395
 396         inode = iget_xattr(c, le64_to_cpu(xent->inum));
 397         if (IS_ERR(inode)) {
 398                 err = PTR_ERR(inode);
 399                 goto out_unlock;
 400         }
 401
 402         ui = ubifs_inode(inode);
 403         ubifs_assert(inode->i_size == ui->data_len);
 404         ubifs_assert(ubifs_inode(host)->xattr_size > ui->data_len);
 405
 406         if (buf) {
 407                 /* If @buf is %NULL we are supposed to return the length */
 408                 if (ui->data_len > size) {
 409                         dbg_err("buffer size %zd, xattr len %d",
 410                                 size, ui->data_len);
 411                         err = -ERANGE;
 412                         goto out_iput;
 413                 }
 414
 415                 memcpy(buf, ui->data, ui->data_len);
 416         }
 417         err = ui->data_len;
 418
 419 out_iput:
 420         iput(inode);
 421 out_unlock:
 422         mutex_unlock(&host->i_mutex);
 423         kfree(xent);
 424         return err;
 425 }
 426
 427 ssize_t ubifs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 428 {
 429         union ubifs_key key;
 430         struct inode *host = dentry->d_inode;
 431         struct ubifs_info *c = host->i_sb->s_fs_info;
 432         struct ubifs_inode *host_ui = ubifs_inode(host);
 433         struct ubifs_dent_node *xent, *pxent = NULL;
 434         int err, len, written = 0;
 435         struct qstr nm = { .name = NULL };
 436
 437         dbg_gen("ino %lu ('%.*s'), buffer size %zd", host->i_ino,
 438                 dentry->d_name.len, dentry->d_name.name, size);
 439
 440         len = host_ui->xattr_names + host_ui->xattr_cnt;
 441         if (!buffer)
 442                 /*
 443                  * We should return the minimum buffer size which will fit a
 444                  * null-terminated list of all the extended attribute names.
 445                  */
 446                 return len;
 447
 448         if (len > size)
 449                 return -ERANGE;
 450
 451         lowest_xent_key(c, &key, host->i_ino);
 452
 453         mutex_lock(&host->i_mutex);
 454         while (1) {
 455                 int type;
 456
 457                 xent = ubifs_tnc_next_ent(c, &key, &nm);
 458                 if (unlikely(IS_ERR(xent))) {
 459                         err = PTR_ERR(xent);
 460                         break;
 461                 }
 462
 463                 nm.name = xent->name;
 464                 nm.len = le16_to_cpu(xent->nlen);
 465
 466                 type = check_namespace(&nm);
 467                 if (unlikely(type < 0)) {
 468                         err = type;
 469                         break;
 470                 }
 471
 472                 /* Show trusted namespace only for "power" users */
 473                 if (type != TRUSTED_XATTR || capable(CAP_SYS_ADMIN)) {
 474                         memcpy(buffer + written, nm.name, nm.len + 1);
 475                         written += nm.len + 1;
 476                 }
 477
 478                 kfree(pxent);
 479                 pxent = xent;
 480                 key_read(c, &xent->key, &key);
 481         }
 482         mutex_unlock(&host->i_mutex);
 483
 484         kfree(pxent);
 485         if (err != -ENOENT) {
 486                 ubifs_err("cannot find next direntry, error %d", err);
 487                 return err;
 488         }
 489
 490         ubifs_assert(written <= size);
 491         return written;
 492 }
 493
 494 static int remove_xattr(struct ubifs_info *c, struct inode *host,
 495                         struct inode *inode, const struct qstr *nm)
 496 {
 497         int err;
 498         struct ubifs_inode *host_ui = ubifs_inode(host);
 499         struct ubifs_inode *ui = ubifs_inode(inode);
 500         struct ubifs_budget_req req = { .dirtied_ino = 1, .mod_dent = 1,
 501                                         .dirtied_ino_d = host_ui->data_len };
 502
 503         ubifs_assert(ui->data_len == inode->i_size);
 504
 505         err = ubifs_budget_space(c, &req);
 506         if (err)
 507                 return err;
 508
 509         mutex_lock(&host_ui->ui_mutex);
 510         host->i_ctime = ubifs_current_time(host);
 511         host_ui->xattr_cnt -= 1;
 512         host_ui->xattr_size -= CALC_DENT_SIZE(nm->len);
 513         host_ui->xattr_size -= CALC_XATTR_BYTES(ui->data_len);
 514         host_ui->xattr_names -= nm->len;
 515
 516         err = ubifs_jnl_delete_xattr(c, host, inode, nm);
 517         if (err)
 518                 goto out_cancel;
 519         mutex_unlock(&host_ui->ui_mutex);
 520
 521         ubifs_release_budget(c, &req);
 522         return 0;
 523
 524 out_cancel:
 525         host_ui->xattr_cnt += 1;
 526         host_ui->xattr_size += CALC_DENT_SIZE(nm->len);
 527         host_ui->xattr_size += CALC_XATTR_BYTES(ui->data_len);
 528         mutex_unlock(&host_ui->ui_mutex);
 529         ubifs_release_budget(c, &req);
 530         make_bad_inode(inode);
 531         return err;
 532 }
 533
 534 int ubifs_removexattr(struct dentry *dentry, const char *name)
 535 {
 536         struct inode *inode, *host = dentry->d_inode;
 537         struct ubifs_info *c = host->i_sb->s_fs_info;
 538         struct qstr nm = { .name = name, .len = strlen(name) };
 539         struct ubifs_dent_node *xent;
 540         union ubifs_key key;
 541         int err;
 542
 543         dbg_gen("xattr '%s', ino %lu ('%.*s')", name,
 544                 host->i_ino, dentry->d_name.len, dentry->d_name.name);
 545         ubifs_assert(mutex_is_locked(&host->i_mutex));
 546
 547         err = check_namespace(&nm);
 548         if (err < 0)
 549                 return err;
 550
 551         xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
 552         if (!xent)
 553                 return -ENOMEM;
 554
 555         xent_key_init(c, &key, host->i_ino, &nm);
 556         err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
 557         if (err) {
 558                 if (err == -ENOENT)
 559                         err = -ENODATA;
 560                 goto out_free;
 561         }
 562
 563         inode = iget_xattr(c, le64_to_cpu(xent->inum));
 564         if (IS_ERR(inode)) {
 565                 err = PTR_ERR(inode);
 566                 goto out_free;
 567         }
 568
 569         ubifs_assert(inode->i_nlink == 1);
 570         inode->i_nlink = 0;
 571         err = remove_xattr(c, host, inode, &nm);
 572         if (err)
 573                 inode->i_nlink = 1;
 574
 575         /* If @i_nlink is 0, 'iput()' will delete the inode */
 576         iput(inode);
 577
 578 out_free:
 579         kfree(xent);
 580         return err;
 581 }