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 #include <linux/posix_acl_xattr.h>
  63
  64 /*
  65  * Limit the number of extended attributes per inode so that the total size
  66  * (@xattr_size) is guaranteeded to fit in an 'unsigned int'.
  67  */
  68 #define MAX_XATTRS_PER_INODE 65535
  69
  70 /*
  71  * Extended attribute type constants.
  72  *
  73  * USER_XATTR: user extended attribute ("user.*")
  74  * TRUSTED_XATTR: trusted extended attribute ("trusted.*)
  75  * SECURITY_XATTR: security extended attribute ("security.*")
  76  */
  77 enum {
  78         USER_XATTR,
  79         TRUSTED_XATTR,
  80         SECURITY_XATTR,
  81 };
  82
  83 static const struct inode_operations empty_iops;
  84 static const struct file_operations empty_fops;
  85
  86 /**
  87  * create_xattr - create an extended attribute.
  88  * @c: UBIFS file-system description object
  89  * @host: host inode
  90  * @nm: extended attribute name
  91  * @value: extended attribute value
  92  * @size: size of extended attribute value
  93  *
  94  * This is a helper function which creates an extended attribute of name @nm
  95  * and value @value for inode @host. The host inode is also updated on flash
  96  * because the ctime and extended attribute accounting data changes. This
  97  * function returns zero in case of success and a negative error code in case
  98  * of failure.
  99  */
 100 static int create_xattr(struct ubifs_info *c, struct inode *host,
 101                         const struct qstr *nm, const void *value, int size)
 102 {
 103         int err;
 104         struct inode *inode;
 105         struct ubifs_inode *ui, *host_ui = ubifs_inode(host);
 106         struct ubifs_budget_req req = { .new_ino = 1, .new_dent = 1,
 107                                 .new_ino_d = ALIGN(size, 8), .dirtied_ino = 1,
 108                                 .dirtied_ino_d = ALIGN(host_ui->data_len, 8) };
 109
 110         if (host_ui->xattr_cnt >= MAX_XATTRS_PER_INODE)
 111                 return -ENOSPC;
 112         /*
 113          * Linux limits the maximum size of the extended attribute names list
 114          * to %XATTR_LIST_MAX. This means we should not allow creating more
 115          * extended attributes if the name list becomes larger. This limitation
 116          * is artificial for UBIFS, though.
 117          */
 118         if (host_ui->xattr_names + host_ui->xattr_cnt +
 119                                         nm->len + 1 > XATTR_LIST_MAX)
 120                 return -ENOSPC;
 121
 122         err = ubifs_budget_space(c, &req);
 123         if (err)
 124                 return err;
 125
 126         inode = ubifs_new_inode(c, host, S_IFREG | S_IRWXUGO);
 127         if (IS_ERR(inode)) {
 128                 err = PTR_ERR(inode);
 129                 goto out_budg;
 130         }
 131
 132         /* Re-define all operations to be "nothing" */
 133         inode->i_mapping->a_ops = &empty_aops;
 134         inode->i_op = &empty_iops;
 135         inode->i_fop = &empty_fops;
 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 = kmemdup(value, size, GFP_NOFS);
 142         if (!ui->data) {
 143                 err = -ENOMEM;
 144                 goto out_free;
 145         }
 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 = kmemdup(value, size, GFP_NOFS);
 207         if (!ui->data) {
 208                 err = -ENOMEM;
 209                 goto out_free;
 210         }
 211         inode->i_size = ui->ui_size = size;
 212         ui->data_len = size;
 213
 214         mutex_lock(&host_ui->ui_mutex);
 215         host->i_ctime = ubifs_current_time(host);
 216         host_ui->xattr_size -= CALC_XATTR_BYTES(ui->data_len);
 217         host_ui->xattr_size += CALC_XATTR_BYTES(size);
 218
 219         /*
 220          * It is important to write the host inode after the xattr inode
 221          * because if the host inode gets synchronized (via 'fsync()'), then
 222          * the extended attribute inode gets synchronized, because it goes
 223          * before the host inode in the write-buffer.
 224          */
 225         err = ubifs_jnl_change_xattr(c, inode, host);
 226         if (err)
 227                 goto out_cancel;
 228         mutex_unlock(&host_ui->ui_mutex);
 229
 230         ubifs_release_budget(c, &req);
 231         return 0;
 232
 233 out_cancel:
 234         host_ui->xattr_size -= CALC_XATTR_BYTES(size);
 235         host_ui->xattr_size += CALC_XATTR_BYTES(ui->data_len);
 236         mutex_unlock(&host_ui->ui_mutex);
 237         make_bad_inode(inode);
 238 out_free:
 239         ubifs_release_budget(c, &req);
 240         return err;
 241 }
 242
 243 /**
 244  * check_namespace - check extended attribute name-space.
 245  * @nm: extended attribute name
 246  *
 247  * This function makes sure the extended attribute name belongs to one of the
 248  * supported extended attribute name-spaces. Returns name-space index in case
 249  * of success and a negative error code in case of failure.
 250  */
 251 static int check_namespace(const struct qstr *nm)
 252 {
 253         int type;
 254
 255         if (nm->len > UBIFS_MAX_NLEN)
 256                 return -ENAMETOOLONG;
 257
 258         if (!strncmp(nm->name, XATTR_TRUSTED_PREFIX,
 259                      XATTR_TRUSTED_PREFIX_LEN)) {
 260                 if (nm->name[sizeof(XATTR_TRUSTED_PREFIX) - 1] == '\0')
 261                         return -EINVAL;
 262                 type = TRUSTED_XATTR;
 263         } else if (!strncmp(nm->name, XATTR_USER_PREFIX,
 264                                       XATTR_USER_PREFIX_LEN)) {
 265                 if (nm->name[XATTR_USER_PREFIX_LEN] == '\0')
 266                         return -EINVAL;
 267                 type = USER_XATTR;
 268         } else if (!strncmp(nm->name, XATTR_SECURITY_PREFIX,
 269                                      XATTR_SECURITY_PREFIX_LEN)) {
 270                 if (nm->name[sizeof(XATTR_SECURITY_PREFIX) - 1] == '\0')
 271                         return -EINVAL;
 272                 type = SECURITY_XATTR;
 273         } else
 274                 return -EOPNOTSUPP;
 275
 276         return type;
 277 }
 278
 279 static struct inode *iget_xattr(struct ubifs_info *c, ino_t inum)
 280 {
 281         struct inode *inode;
 282
 283         inode = ubifs_iget(c->vfs_sb, inum);
 284         if (IS_ERR(inode)) {
 285                 ubifs_err("dead extended attribute entry, error %d",
 286                           (int)PTR_ERR(inode));
 287                 return inode;
 288         }
 289         if (ubifs_inode(inode)->xattr)
 290                 return inode;
 291         ubifs_err("corrupt extended attribute entry");
 292         iput(inode);
 293         return ERR_PTR(-EINVAL);
 294 }
 295
 296 int ubifs_setxattr(struct dentry *dentry, const char *name,
 297                    const void *value, size_t size, int flags)
 298 {
 299         struct inode *inode, *host = dentry->d_inode;
 300         struct ubifs_info *c = host->i_sb->s_fs_info;
 301         struct qstr nm = QSTR_INIT(name, strlen(name));
 302         struct ubifs_dent_node *xent;
 303         union ubifs_key key;
 304         int err, type;
 305
 306         dbg_gen("xattr '%s', host ino %lu ('%.*s'), size %zd", name,
 307                 host->i_ino, dentry->d_name.len, dentry->d_name.name, size);
 308         ubifs_assert(mutex_is_locked(&host->i_mutex));
 309
 310         if (size > UBIFS_MAX_INO_DATA)
 311                 return -ERANGE;
 312
 313         type = check_namespace(&nm);
 314         if (type < 0)
 315                 return type;
 316
 317         xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
 318         if (!xent)
 319                 return -ENOMEM;
 320
 321         /*
 322          * The extended attribute entries are stored in LNC, so multiple
 323          * look-ups do not involve reading the flash.
 324          */
 325         xent_key_init(c, &key, host->i_ino, &nm);
 326         err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
 327         if (err) {
 328                 if (err != -ENOENT)
 329                         goto out_free;
 330
 331                 if (flags & XATTR_REPLACE)
 332                         /* We are asked not to create the xattr */
 333                         err = -ENODATA;
 334                 else
 335                         err = create_xattr(c, host, &nm, value, size);
 336                 goto out_free;
 337         }
 338
 339         if (flags & XATTR_CREATE) {
 340                 /* We are asked not to replace the xattr */
 341                 err = -EEXIST;
 342                 goto out_free;
 343         }
 344
 345         inode = iget_xattr(c, le64_to_cpu(xent->inum));
 346         if (IS_ERR(inode)) {
 347                 err = PTR_ERR(inode);
 348                 goto out_free;
 349         }
 350
 351         err = change_xattr(c, host, inode, value, size);
 352         iput(inode);
 353
 354 out_free:
 355         kfree(xent);
 356         return err;
 357 }
 358
 359 ssize_t ubifs_getxattr(struct dentry *dentry, const char *name, void *buf,
 360                        size_t size)
 361 {
 362         struct inode *inode, *host = dentry->d_inode;
 363         struct ubifs_info *c = host->i_sb->s_fs_info;
 364         struct qstr nm = QSTR_INIT(name, strlen(name));
 365         struct ubifs_inode *ui;
 366         struct ubifs_dent_node *xent;
 367         union ubifs_key key;
 368         int err;
 369
 370         dbg_gen("xattr '%s', ino %lu ('%.*s'), buf size %zd", name,
 371                 host->i_ino, dentry->d_name.len, dentry->d_name.name, size);
 372
 373         err = check_namespace(&nm);
 374         if (err < 0)
 375                 return err;
 376
 377         xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
 378         if (!xent)
 379                 return -ENOMEM;
 380
 381         xent_key_init(c, &key, host->i_ino, &nm);
 382         err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
 383         if (err) {
 384                 if (err == -ENOENT)
 385                         err = -ENODATA;
 386                 goto out_unlock;
 387         }
 388
 389         inode = iget_xattr(c, le64_to_cpu(xent->inum));
 390         if (IS_ERR(inode)) {
 391                 err = PTR_ERR(inode);
 392                 goto out_unlock;
 393         }
 394
 395         ui = ubifs_inode(inode);
 396         ubifs_assert(inode->i_size == ui->data_len);
 397         ubifs_assert(ubifs_inode(host)->xattr_size > ui->data_len);
 398
 399         if (buf) {
 400                 /* If @buf is %NULL we are supposed to return the length */
 401                 if (ui->data_len > size) {
 402                         ubifs_err("buffer size %zd, xattr len %d",
 403                                   size, ui->data_len);
 404                         err = -ERANGE;
 405                         goto out_iput;
 406                 }
 407
 408                 memcpy(buf, ui->data, ui->data_len);
 409         }
 410         err = ui->data_len;
 411
 412 out_iput:
 413         iput(inode);
 414 out_unlock:
 415         kfree(xent);
 416         return err;
 417 }
 418
 419 ssize_t ubifs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 420 {
 421         union ubifs_key key;
 422         struct inode *host = dentry->d_inode;
 423         struct ubifs_info *c = host->i_sb->s_fs_info;
 424         struct ubifs_inode *host_ui = ubifs_inode(host);
 425         struct ubifs_dent_node *xent, *pxent = NULL;
 426         int err, len, written = 0;
 427         struct qstr nm = { .name = NULL };
 428
 429         dbg_gen("ino %lu ('%.*s'), buffer size %zd", host->i_ino,
 430                 dentry->d_name.len, dentry->d_name.name, size);
 431
 432         len = host_ui->xattr_names + host_ui->xattr_cnt;
 433         if (!buffer)
 434                 /*
 435                  * We should return the minimum buffer size which will fit a
 436                  * null-terminated list of all the extended attribute names.
 437                  */
 438                 return len;
 439
 440         if (len > size)
 441                 return -ERANGE;
 442
 443         lowest_xent_key(c, &key, host->i_ino);
 444         while (1) {
 445                 int type;
 446
 447                 xent = ubifs_tnc_next_ent(c, &key, &nm);
 448                 if (IS_ERR(xent)) {
 449                         err = PTR_ERR(xent);
 450                         break;
 451                 }
 452
 453                 nm.name = xent->name;
 454                 nm.len = le16_to_cpu(xent->nlen);
 455
 456                 type = check_namespace(&nm);
 457                 if (unlikely(type < 0)) {
 458                         err = type;
 459                         break;
 460                 }
 461
 462                 /* Show trusted namespace only for "power" users */
 463                 if (type != TRUSTED_XATTR || capable(CAP_SYS_ADMIN)) {
 464                         memcpy(buffer + written, nm.name, nm.len + 1);
 465                         written += nm.len + 1;
 466                 }
 467
 468                 kfree(pxent);
 469                 pxent = xent;
 470                 key_read(c, &xent->key, &key);
 471         }
 472
 473         kfree(pxent);
 474         if (err != -ENOENT) {
 475                 ubifs_err("cannot find next direntry, error %d", err);
 476                 return err;
 477         }
 478
 479         ubifs_assert(written <= size);
 480         return written;
 481 }
 482
 483 static int remove_xattr(struct ubifs_info *c, struct inode *host,
 484                         struct inode *inode, const struct qstr *nm)
 485 {
 486         int err;
 487         struct ubifs_inode *host_ui = ubifs_inode(host);
 488         struct ubifs_inode *ui = ubifs_inode(inode);
 489         struct ubifs_budget_req req = { .dirtied_ino = 2, .mod_dent = 1,
 490                                 .dirtied_ino_d = ALIGN(host_ui->data_len, 8) };
 491
 492         ubifs_assert(ui->data_len == inode->i_size);
 493
 494         err = ubifs_budget_space(c, &req);
 495         if (err)
 496                 return err;
 497
 498         mutex_lock(&host_ui->ui_mutex);
 499         host->i_ctime = ubifs_current_time(host);
 500         host_ui->xattr_cnt -= 1;
 501         host_ui->xattr_size -= CALC_DENT_SIZE(nm->len);
 502         host_ui->xattr_size -= CALC_XATTR_BYTES(ui->data_len);
 503         host_ui->xattr_names -= nm->len;
 504
 505         err = ubifs_jnl_delete_xattr(c, host, inode, nm);
 506         if (err)
 507                 goto out_cancel;
 508         mutex_unlock(&host_ui->ui_mutex);
 509
 510         ubifs_release_budget(c, &req);
 511         return 0;
 512
 513 out_cancel:
 514         host_ui->xattr_cnt += 1;
 515         host_ui->xattr_size += CALC_DENT_SIZE(nm->len);
 516         host_ui->xattr_size += CALC_XATTR_BYTES(ui->data_len);
 517         mutex_unlock(&host_ui->ui_mutex);
 518         ubifs_release_budget(c, &req);
 519         make_bad_inode(inode);
 520         return err;
 521 }
 522
 523 int ubifs_removexattr(struct dentry *dentry, const char *name)
 524 {
 525         struct inode *inode, *host = dentry->d_inode;
 526         struct ubifs_info *c = host->i_sb->s_fs_info;
 527         struct qstr nm = QSTR_INIT(name, strlen(name));
 528         struct ubifs_dent_node *xent;
 529         union ubifs_key key;
 530         int err;
 531
 532         dbg_gen("xattr '%s', ino %lu ('%.*s')", name,
 533                 host->i_ino, dentry->d_name.len, dentry->d_name.name);
 534         ubifs_assert(mutex_is_locked(&host->i_mutex));
 535
 536         err = check_namespace(&nm);
 537         if (err < 0)
 538                 return err;
 539
 540         xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
 541         if (!xent)
 542                 return -ENOMEM;
 543
 544         xent_key_init(c, &key, host->i_ino, &nm);
 545         err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
 546         if (err) {
 547                 if (err == -ENOENT)
 548                         err = -ENODATA;
 549                 goto out_free;
 550         }
 551
 552         inode = iget_xattr(c, le64_to_cpu(xent->inum));
 553         if (IS_ERR(inode)) {
 554                 err = PTR_ERR(inode);
 555                 goto out_free;
 556         }
 557
 558         ubifs_assert(inode->i_nlink == 1);
 559         clear_nlink(inode);
 560         err = remove_xattr(c, host, inode, &nm);
 561         if (err)
 562                 set_nlink(inode, 1);
 563
 564         /* If @i_nlink is 0, 'iput()' will delete the inode */
 565         iput(inode);
 566
 567 out_free:
 568         kfree(xent);
 569         return err;
 570 }