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/xattr.h>
  60 #include <linux/posix_acl_xattr.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 const struct inode_operations none_inode_operations;
  82 static const struct address_space_operations none_address_operations;
  83 static const 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 = 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                 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         /* Re-define all operations to be "nothing" */
 132         inode->i_mapping->a_ops = &none_address_operations;
 133         inode->i_op = &none_inode_operations;
 134         inode->i_fop = &none_file_operations;
 135
 136         inode->i_flags |= S_SYNC | S_NOATIME | S_NOCMTIME | S_NOQUOTA;
 137         ui = ubifs_inode(inode);
 138         ui->xattr = 1;
 139         ui->flags |= UBIFS_XATTR_FL;
 140         ui->data = kmalloc(size, GFP_NOFS);
 141         if (!ui->data) {
 142                 err = -ENOMEM;
 143                 goto out_free;
 144         }
 145         memcpy(ui->data, value, size);
 146         inode->i_size = ui->ui_size = size;
 147         ui->data_len = size;
 148
 149         mutex_lock(&host_ui->ui_mutex);
 150         host->i_ctime = ubifs_current_time(host);
 151         host_ui->xattr_cnt += 1;
 152         host_ui->xattr_size += CALC_DENT_SIZE(nm->len);
 153         host_ui->xattr_size += CALC_XATTR_BYTES(size);
 154         host_ui->xattr_names += nm->len;
 155
 156         err = ubifs_jnl_update(c, host, nm, inode, 0, 1);
 157         if (err)
 158                 goto out_cancel;
 159         mutex_unlock(&host_ui->ui_mutex);
 160
 161         ubifs_release_budget(c, &req);
 162         insert_inode_hash(inode);
 163         iput(inode);
 164         return 0;
 165
 166 out_cancel:
 167         host_ui->xattr_cnt -= 1;
 168         host_ui->xattr_size -= CALC_DENT_SIZE(nm->len);
 169         host_ui->xattr_size -= CALC_XATTR_BYTES(size);
 170         mutex_unlock(&host_ui->ui_mutex);
 171 out_free:
 172         make_bad_inode(inode);
 173         iput(inode);
 174 out_budg:
 175         ubifs_release_budget(c, &req);
 176         return err;
 177 }
 178
 179 /**
 180  * change_xattr - change an extended attribute.
 181  * @c: UBIFS file-system description object
 182  * @host: host inode
 183  * @inode: extended attribute inode
 184  * @value: extended attribute value
 185  * @size: size of extended attribute value
 186  *
 187  * This helper function changes the value of extended attribute @inode with new
 188  * data from @value. Returns zero in case of success and a negative error code
 189  * in case of failure.
 190  */
 191 static int change_xattr(struct ubifs_info *c, struct inode *host,
 192                         struct inode *inode, const void *value, int size)
 193 {
 194         int err;
 195         struct ubifs_inode *host_ui = ubifs_inode(host);
 196         struct ubifs_inode *ui = ubifs_inode(inode);
 197         struct ubifs_budget_req req = { .dirtied_ino = 2,
 198                 .dirtied_ino_d = ALIGN(size, 8) + ALIGN(host_ui->data_len, 8) };
 199
 200         ubifs_assert(ui->data_len == inode->i_size);
 201         err = ubifs_budget_space(c, &req);
 202         if (err)
 203                 return err;
 204
 205         kfree(ui->data);
 206         ui->data = kmalloc(size, GFP_NOFS);
 207         if (!ui->data) {
 208                 err = -ENOMEM;
 209                 goto out_free;
 210         }
 211         memcpy(ui->data, value, size);
 212         inode->i_size = ui->ui_size = size;
 213         ui->data_len = size;
 214
 215         mutex_lock(&host_ui->ui_mutex);
 216         host->i_ctime = ubifs_current_time(host);
 217         host_ui->xattr_size -= CALC_XATTR_BYTES(ui->data_len);
 218         host_ui->xattr_size += CALC_XATTR_BYTES(size);
 219
 220         /*
 221          * It is important to write the host inode after the xattr inode
 222          * because if the host inode gets synchronized (via 'fsync()'), then
 223          * the extended attribute inode gets synchronized, because it goes
 224          * before the host inode in the write-buffer.
 225          */
 226         err = ubifs_jnl_change_xattr(c, inode, host);
 227         if (err)
 228                 goto out_cancel;
 229         mutex_unlock(&host_ui->ui_mutex);
 230
 231         ubifs_release_budget(c, &req);
 232         return 0;
 233
 234 out_cancel:
 235         host_ui->xattr_size -= CALC_XATTR_BYTES(size);
 236         host_ui->xattr_size += CALC_XATTR_BYTES(ui->data_len);
 237         mutex_unlock(&host_ui->ui_mutex);
 238         make_bad_inode(inode);
 239 out_free:
 240         ubifs_release_budget(c, &req);
 241         return err;
 242 }
 243
 244 /**
 245  * check_namespace - check extended attribute name-space.
 246  * @nm: extended attribute name
 247  *
 248  * This function makes sure the extended attribute name belongs to one of the
 249  * supported extended attribute name-spaces. Returns name-space index in case
 250  * of success and a negative error code in case of failure.
 251  */
 252 static int check_namespace(const struct qstr *nm)
 253 {
 254         int type;
 255
 256         if (nm->len > UBIFS_MAX_NLEN)
 257                 return -ENAMETOOLONG;
 258
 259         if (!strncmp(nm->name, XATTR_TRUSTED_PREFIX,
 260                      XATTR_TRUSTED_PREFIX_LEN)) {
 261                 if (nm->name[sizeof(XATTR_TRUSTED_PREFIX) - 1] == '\0')
 262                         return -EINVAL;
 263                 type = TRUSTED_XATTR;
 264         } else if (!strncmp(nm->name, XATTR_USER_PREFIX,
 265                                       XATTR_USER_PREFIX_LEN)) {
 266                 if (nm->name[XATTR_USER_PREFIX_LEN] == '\0')
 267                         return -EINVAL;
 268                 type = USER_XATTR;
 269         } else if (!strncmp(nm->name, XATTR_SECURITY_PREFIX,
 270                                      XATTR_SECURITY_PREFIX_LEN)) {
 271                 if (nm->name[sizeof(XATTR_SECURITY_PREFIX) - 1] == '\0')
 272                         return -EINVAL;
 273                 type = SECURITY_XATTR;
 274         } else
 275                 return -EOPNOTSUPP;
 276
 277         return type;
 278 }
 279
 280 static struct inode *iget_xattr(struct ubifs_info *c, ino_t inum)
 281 {
 282         struct inode *inode;
 283
 284         inode = ubifs_iget(c->vfs_sb, inum);
 285         if (IS_ERR(inode)) {
 286                 ubifs_err("dead extended attribute entry, error %d",
 287                           (int)PTR_ERR(inode));
 288                 return inode;
 289         }
 290         if (ubifs_inode(inode)->xattr)
 291                 return inode;
 292         ubifs_err("corrupt extended attribute entry");
 293         iput(inode);
 294         return ERR_PTR(-EINVAL);
 295 }
 296
 297 int ubifs_setxattr(struct dentry *dentry, const char *name,
 298                    const void *value, size_t size, int flags)
 299 {
 300         struct inode *inode, *host = dentry->d_inode;
 301         struct ubifs_info *c = host->i_sb->s_fs_info;
 302         struct qstr nm = { .name = name, .len = strlen(name) };
 303         struct ubifs_dent_node *xent;
 304         union ubifs_key key;
 305         int err, type;
 306
 307         dbg_gen("xattr '%s', host ino %lu ('%.*s'), size %zd", name,
 308                 host->i_ino, dentry->d_name.len, dentry->d_name.name, size);
 309         ubifs_assert(mutex_is_locked(&host->i_mutex));
 310
 311         if (size > UBIFS_MAX_INO_DATA)
 312                 return -ERANGE;
 313
 314         type = check_namespace(&nm);
 315         if (type < 0)
 316                 return type;
 317
 318         xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
 319         if (!xent)
 320                 return -ENOMEM;
 321
 322         /*
 323          * The extended attribute entries are stored in LNC, so multiple
 324          * look-ups do not involve reading the flash.
 325          */
 326         xent_key_init(c, &key, host->i_ino, &nm);
 327         err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
 328         if (err) {
 329                 if (err != -ENOENT)
 330                         goto out_free;
 331
 332                 if (flags & XATTR_REPLACE)
 333                         /* We are asked not to create the xattr */
 334                         err = -ENODATA;
 335                 else
 336                         err = create_xattr(c, host, &nm, value, size);
 337                 goto out_free;
 338         }
 339
 340         if (flags & XATTR_CREATE) {
 341                 /* We are asked not to replace the xattr */
 342                 err = -EEXIST;
 343                 goto out_free;
 344         }
 345
 346         inode = iget_xattr(c, le64_to_cpu(xent->inum));
 347         if (IS_ERR(inode)) {
 348                 err = PTR_ERR(inode);
 349                 goto out_free;
 350         }
 351
 352         err = change_xattr(c, host, inode, value, size);
 353         iput(inode);
 354
 355 out_free:
 356         kfree(xent);
 357         return err;
 358 }
 359
 360 ssize_t ubifs_getxattr(struct dentry *dentry, const char *name, void *buf,
 361                        size_t size)
 362 {
 363         struct inode *inode, *host = dentry->d_inode;
 364         struct ubifs_info *c = host->i_sb->s_fs_info;
 365         struct qstr nm = { .name = name, .len = strlen(name) };
 366         struct ubifs_inode *ui;
 367         struct ubifs_dent_node *xent;
 368         union ubifs_key key;
 369         int err;
 370
 371         dbg_gen("xattr '%s', ino %lu ('%.*s'), buf size %zd", name,
 372                 host->i_ino, dentry->d_name.len, dentry->d_name.name, size);
 373
 374         err = check_namespace(&nm);
 375         if (err < 0)
 376                 return err;
 377
 378         xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
 379         if (!xent)
 380                 return -ENOMEM;
 381
 382         xent_key_init(c, &key, host->i_ino, &nm);
 383         err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
 384         if (err) {
 385                 if (err == -ENOENT)
 386                         err = -ENODATA;
 387                 goto out_unlock;
 388         }
 389
 390         inode = iget_xattr(c, le64_to_cpu(xent->inum));
 391         if (IS_ERR(inode)) {
 392                 err = PTR_ERR(inode);
 393                 goto out_unlock;
 394         }
 395
 396         ui = ubifs_inode(inode);
 397         ubifs_assert(inode->i_size == ui->data_len);
 398         ubifs_assert(ubifs_inode(host)->xattr_size > ui->data_len);
 399
 400         if (buf) {
 401                 /* If @buf is %NULL we are supposed to return the length */
 402                 if (ui->data_len > size) {
 403                         dbg_err("buffer size %zd, xattr len %d",
 404                                 size, ui->data_len);
 405                         err = -ERANGE;
 406                         goto out_iput;
 407                 }
 408
 409                 memcpy(buf, ui->data, ui->data_len);
 410         }
 411         err = ui->data_len;
 412
 413 out_iput:
 414         iput(inode);
 415 out_unlock:
 416         kfree(xent);
 417         return err;
 418 }
 419
 420 ssize_t ubifs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 421 {
 422         union ubifs_key key;
 423         struct inode *host = dentry->d_inode;
 424         struct ubifs_info *c = host->i_sb->s_fs_info;
 425         struct ubifs_inode *host_ui = ubifs_inode(host);
 426         struct ubifs_dent_node *xent, *pxent = NULL;
 427         int err, len, written = 0;
 428         struct qstr nm = { .name = NULL };
 429
 430         dbg_gen("ino %lu ('%.*s'), buffer size %zd", host->i_ino,
 431                 dentry->d_name.len, dentry->d_name.name, size);
 432
 433         len = host_ui->xattr_names + host_ui->xattr_cnt;
 434         if (!buffer)
 435                 /*
 436                  * We should return the minimum buffer size which will fit a
 437                  * null-terminated list of all the extended attribute names.
 438                  */
 439                 return len;
 440
 441         if (len > size)
 442                 return -ERANGE;
 443
 444         lowest_xent_key(c, &key, host->i_ino);
 445         while (1) {
 446                 int type;
 447
 448                 xent = ubifs_tnc_next_ent(c, &key, &nm);
 449                 if (IS_ERR(xent)) {
 450                         err = PTR_ERR(xent);
 451                         break;
 452                 }
 453
 454                 nm.name = xent->name;
 455                 nm.len = le16_to_cpu(xent->nlen);
 456
 457                 type = check_namespace(&nm);
 458                 if (unlikely(type < 0)) {
 459                         err = type;
 460                         break;
 461                 }
 462
 463                 /* Show trusted namespace only for "power" users */
 464                 if (type != TRUSTED_XATTR || capable(CAP_SYS_ADMIN)) {
 465                         memcpy(buffer + written, nm.name, nm.len + 1);
 466                         written += nm.len + 1;
 467                 }
 468
 469                 kfree(pxent);
 470                 pxent = xent;
 471                 key_read(c, &xent->key, &key);
 472         }
 473
 474         kfree(pxent);
 475         if (err != -ENOENT) {
 476                 ubifs_err("cannot find next direntry, error %d", err);
 477                 return err;
 478         }
 479
 480         ubifs_assert(written <= size);
 481         return written;
 482 }
 483
 484 static int remove_xattr(struct ubifs_info *c, struct inode *host,
 485                         struct inode *inode, const struct qstr *nm)
 486 {
 487         int err;
 488         struct ubifs_inode *host_ui = ubifs_inode(host);
 489         struct ubifs_inode *ui = ubifs_inode(inode);
 490         struct ubifs_budget_req req = { .dirtied_ino = 2, .mod_dent = 1,
 491                                 .dirtied_ino_d = ALIGN(host_ui->data_len, 8) };
 492
 493         ubifs_assert(ui->data_len == inode->i_size);
 494
 495         err = ubifs_budget_space(c, &req);
 496         if (err)
 497                 return err;
 498
 499         mutex_lock(&host_ui->ui_mutex);
 500         host->i_ctime = ubifs_current_time(host);
 501         host_ui->xattr_cnt -= 1;
 502         host_ui->xattr_size -= CALC_DENT_SIZE(nm->len);
 503         host_ui->xattr_size -= CALC_XATTR_BYTES(ui->data_len);
 504         host_ui->xattr_names -= nm->len;
 505
 506         err = ubifs_jnl_delete_xattr(c, host, inode, nm);
 507         if (err)
 508                 goto out_cancel;
 509         mutex_unlock(&host_ui->ui_mutex);
 510
 511         ubifs_release_budget(c, &req);
 512         return 0;
 513
 514 out_cancel:
 515         host_ui->xattr_cnt += 1;
 516         host_ui->xattr_size += CALC_DENT_SIZE(nm->len);
 517         host_ui->xattr_size += CALC_XATTR_BYTES(ui->data_len);
 518         mutex_unlock(&host_ui->ui_mutex);
 519         ubifs_release_budget(c, &req);
 520         make_bad_inode(inode);
 521         return err;
 522 }
 523
 524 int ubifs_removexattr(struct dentry *dentry, const char *name)
 525 {
 526         struct inode *inode, *host = dentry->d_inode;
 527         struct ubifs_info *c = host->i_sb->s_fs_info;
 528         struct qstr nm = { .name = name, .len = strlen(name) };
 529         struct ubifs_dent_node *xent;
 530         union ubifs_key key;
 531         int err;
 532
 533         dbg_gen("xattr '%s', ino %lu ('%.*s')", name,
 534                 host->i_ino, dentry->d_name.len, dentry->d_name.name);
 535         ubifs_assert(mutex_is_locked(&host->i_mutex));
 536
 537         err = check_namespace(&nm);
 538         if (err < 0)
 539                 return err;
 540
 541         xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
 542         if (!xent)
 543                 return -ENOMEM;
 544
 545         xent_key_init(c, &key, host->i_ino, &nm);
 546         err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
 547         if (err) {
 548                 if (err == -ENOENT)
 549                         err = -ENODATA;
 550                 goto out_free;
 551         }
 552
 553         inode = iget_xattr(c, le64_to_cpu(xent->inum));
 554         if (IS_ERR(inode)) {
 555                 err = PTR_ERR(inode);
 556                 goto out_free;
 557         }
 558
 559         ubifs_assert(inode->i_nlink == 1);
 560         inode->i_nlink = 0;
 561         err = remove_xattr(c, host, inode, &nm);
 562         if (err)
 563                 inode->i_nlink = 1;
 564
 565         /* If @i_nlink is 0, 'iput()' will delete the inode */
 566         iput(inode);
 567
 568 out_free:
 569         kfree(xent);
 570         return err;
 571 }