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 = kmalloc(size, GFP_NOFS);
 142         if (!ui->data) {
 143                 err = -ENOMEM;
 144                 goto out_free;
 145         }
 146         memcpy(ui->data, value, size);
 147         inode->i_size = ui->ui_size = size;
 148         ui->data_len = size;
 149
 150         mutex_lock(&host_ui->ui_mutex);
 151         host->i_ctime = ubifs_current_time(host);
 152         host_ui->xattr_cnt += 1;
 153         host_ui->xattr_size += CALC_DENT_SIZE(nm->len);
 154         host_ui->xattr_size += CALC_XATTR_BYTES(size);
 155         host_ui->xattr_names += nm->len;
 156
 157         err = ubifs_jnl_update(c, host, nm, inode, 0, 1);
 158         if (err)
 159                 goto out_cancel;
 160         mutex_unlock(&host_ui->ui_mutex);
 161
 162         ubifs_release_budget(c, &req);
 163         insert_inode_hash(inode);
 164         iput(inode);
 165         return 0;
 166
 167 out_cancel:
 168         host_ui->xattr_cnt -= 1;
 169         host_ui->xattr_size -= CALC_DENT_SIZE(nm->len);
 170         host_ui->xattr_size -= CALC_XATTR_BYTES(size);
 171         mutex_unlock(&host_ui->ui_mutex);
 172 out_free:
 173         make_bad_inode(inode);
 174         iput(inode);
 175 out_budg:
 176         ubifs_release_budget(c, &req);
 177         return err;
 178 }
 179
 180 /**
 181  * change_xattr - change an extended attribute.
 182  * @c: UBIFS file-system description object
 183  * @host: host inode
 184  * @inode: extended attribute inode
 185  * @value: extended attribute value
 186  * @size: size of extended attribute value
 187  *
 188  * This helper function changes the value of extended attribute @inode with new
 189  * data from @value. Returns zero in case of success and a negative error code
 190  * in case of failure.
 191  */
 192 static int change_xattr(struct ubifs_info *c, struct inode *host,
 193                         struct inode *inode, const void *value, int size)
 194 {
 195         int err;
 196         struct ubifs_inode *host_ui = ubifs_inode(host);
 197         struct ubifs_inode *ui = ubifs_inode(inode);
 198         struct ubifs_budget_req req = { .dirtied_ino = 2,
 199                 .dirtied_ino_d = ALIGN(size, 8) + ALIGN(host_ui->data_len, 8) };
 200
 201         ubifs_assert(ui->data_len == inode->i_size);
 202         err = ubifs_budget_space(c, &req);
 203         if (err)
 204                 return err;
 205
 206         kfree(ui->data);
 207         ui->data = kmalloc(size, GFP_NOFS);
 208         if (!ui->data) {
 209                 err = -ENOMEM;
 210                 goto out_free;
 211         }
 212         memcpy(ui->data, value, size);
 213         inode->i_size = ui->ui_size = size;
 214         ui->data_len = size;
 215
 216         mutex_lock(&host_ui->ui_mutex);
 217         host->i_ctime = ubifs_current_time(host);
 218         host_ui->xattr_size -= CALC_XATTR_BYTES(ui->data_len);
 219         host_ui->xattr_size += CALC_XATTR_BYTES(size);
 220
 221         /*
 222          * It is important to write the host inode after the xattr inode
 223          * because if the host inode gets synchronized (via 'fsync()'), then
 224          * the extended attribute inode gets synchronized, because it goes
 225          * before the host inode in the write-buffer.
 226          */
 227         err = ubifs_jnl_change_xattr(c, inode, host);
 228         if (err)
 229                 goto out_cancel;
 230         mutex_unlock(&host_ui->ui_mutex);
 231
 232         ubifs_release_budget(c, &req);
 233         return 0;
 234
 235 out_cancel:
 236         host_ui->xattr_size -= CALC_XATTR_BYTES(size);
 237         host_ui->xattr_size += CALC_XATTR_BYTES(ui->data_len);
 238         mutex_unlock(&host_ui->ui_mutex);
 239         make_bad_inode(inode);
 240 out_free:
 241         ubifs_release_budget(c, &req);
 242         return err;
 243 }
 244
 245 /**
 246  * check_namespace - check extended attribute name-space.
 247  * @nm: extended attribute name
 248  *
 249  * This function makes sure the extended attribute name belongs to one of the
 250  * supported extended attribute name-spaces. Returns name-space index in case
 251  * of success and a negative error code in case of failure.
 252  */
 253 static int check_namespace(const struct qstr *nm)
 254 {
 255         int type;
 256
 257         if (nm->len > UBIFS_MAX_NLEN)
 258                 return -ENAMETOOLONG;
 259
 260         if (!strncmp(nm->name, XATTR_TRUSTED_PREFIX,
 261                      XATTR_TRUSTED_PREFIX_LEN)) {
 262                 if (nm->name[sizeof(XATTR_TRUSTED_PREFIX) - 1] == '\0')
 263                         return -EINVAL;
 264                 type = TRUSTED_XATTR;
 265         } else if (!strncmp(nm->name, XATTR_USER_PREFIX,
 266                                       XATTR_USER_PREFIX_LEN)) {
 267                 if (nm->name[XATTR_USER_PREFIX_LEN] == '\0')
 268                         return -EINVAL;
 269                 type = USER_XATTR;
 270         } else if (!strncmp(nm->name, XATTR_SECURITY_PREFIX,
 271                                      XATTR_SECURITY_PREFIX_LEN)) {
 272                 if (nm->name[sizeof(XATTR_SECURITY_PREFIX) - 1] == '\0')
 273                         return -EINVAL;
 274                 type = SECURITY_XATTR;
 275         } else
 276                 return -EOPNOTSUPP;
 277
 278         return type;
 279 }
 280
 281 static struct inode *iget_xattr(struct ubifs_info *c, ino_t inum)
 282 {
 283         struct inode *inode;
 284
 285         inode = ubifs_iget(c->vfs_sb, inum);
 286         if (IS_ERR(inode)) {
 287                 ubifs_err("dead extended attribute entry, error %d",
 288                           (int)PTR_ERR(inode));
 289                 return inode;
 290         }
 291         if (ubifs_inode(inode)->xattr)
 292                 return inode;
 293         ubifs_err("corrupt extended attribute entry");
 294         iput(inode);
 295         return ERR_PTR(-EINVAL);
 296 }
 297
 298 int ubifs_setxattr(struct dentry *dentry, const char *name,
 299                    const void *value, size_t size, int flags)
 300 {
 301         struct inode *inode, *host = dentry->d_inode;
 302         struct ubifs_info *c = host->i_sb->s_fs_info;
 303         struct qstr nm = { .name = name, .len = strlen(name) };
 304         struct ubifs_dent_node *xent;
 305         union ubifs_key key;
 306         int err, type;
 307
 308         dbg_gen("xattr '%s', host ino %lu ('%.*s'), size %zd", name,
 309                 host->i_ino, dentry->d_name.len, dentry->d_name.name, size);
 310         ubifs_assert(mutex_is_locked(&host->i_mutex));
 311
 312         if (size > UBIFS_MAX_INO_DATA)
 313                 return -ERANGE;
 314
 315         type = check_namespace(&nm);
 316         if (type < 0)
 317                 return type;
 318
 319         xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
 320         if (!xent)
 321                 return -ENOMEM;
 322
 323         /*
 324          * The extended attribute entries are stored in LNC, so multiple
 325          * look-ups do not involve reading the flash.
 326          */
 327         xent_key_init(c, &key, host->i_ino, &nm);
 328         err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
 329         if (err) {
 330                 if (err != -ENOENT)
 331                         goto out_free;
 332
 333                 if (flags & XATTR_REPLACE)
 334                         /* We are asked not to create the xattr */
 335                         err = -ENODATA;
 336                 else
 337                         err = create_xattr(c, host, &nm, value, size);
 338                 goto out_free;
 339         }
 340
 341         if (flags & XATTR_CREATE) {
 342                 /* We are asked not to replace the xattr */
 343                 err = -EEXIST;
 344                 goto out_free;
 345         }
 346
 347         inode = iget_xattr(c, le64_to_cpu(xent->inum));
 348         if (IS_ERR(inode)) {
 349                 err = PTR_ERR(inode);
 350                 goto out_free;
 351         }
 352
 353         err = change_xattr(c, host, inode, value, size);
 354         iput(inode);
 355
 356 out_free:
 357         kfree(xent);
 358         return err;
 359 }
 360
 361 ssize_t ubifs_getxattr(struct dentry *dentry, const char *name, void *buf,
 362                        size_t size)
 363 {
 364         struct inode *inode, *host = dentry->d_inode;
 365         struct ubifs_info *c = host->i_sb->s_fs_info;
 366         struct qstr nm = { .name = name, .len = strlen(name) };
 367         struct ubifs_inode *ui;
 368         struct ubifs_dent_node *xent;
 369         union ubifs_key key;
 370         int err;
 371
 372         dbg_gen("xattr '%s', ino %lu ('%.*s'), buf size %zd", name,
 373                 host->i_ino, dentry->d_name.len, dentry->d_name.name, size);
 374
 375         err = check_namespace(&nm);
 376         if (err < 0)
 377                 return err;
 378
 379         xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
 380         if (!xent)
 381                 return -ENOMEM;
 382
 383         xent_key_init(c, &key, host->i_ino, &nm);
 384         err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
 385         if (err) {
 386                 if (err == -ENOENT)
 387                         err = -ENODATA;
 388                 goto out_unlock;
 389         }
 390
 391         inode = iget_xattr(c, le64_to_cpu(xent->inum));
 392         if (IS_ERR(inode)) {
 393                 err = PTR_ERR(inode);
 394                 goto out_unlock;
 395         }
 396
 397         ui = ubifs_inode(inode);
 398         ubifs_assert(inode->i_size == ui->data_len);
 399         ubifs_assert(ubifs_inode(host)->xattr_size > ui->data_len);
 400
 401         if (buf) {
 402                 /* If @buf is %NULL we are supposed to return the length */
 403                 if (ui->data_len > size) {
 404                         dbg_err("buffer size %zd, xattr len %d",
 405                                 size, ui->data_len);
 406                         err = -ERANGE;
 407                         goto out_iput;
 408                 }
 409
 410                 memcpy(buf, ui->data, ui->data_len);
 411         }
 412         err = ui->data_len;
 413
 414 out_iput:
 415         iput(inode);
 416 out_unlock:
 417         kfree(xent);
 418         return err;
 419 }
 420
 421 ssize_t ubifs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 422 {
 423         union ubifs_key key;
 424         struct inode *host = dentry->d_inode;
 425         struct ubifs_info *c = host->i_sb->s_fs_info;
 426         struct ubifs_inode *host_ui = ubifs_inode(host);
 427         struct ubifs_dent_node *xent, *pxent = NULL;
 428         int err, len, written = 0;
 429         struct qstr nm = { .name = NULL };
 430
 431         dbg_gen("ino %lu ('%.*s'), buffer size %zd", host->i_ino,
 432                 dentry->d_name.len, dentry->d_name.name, size);
 433
 434         len = host_ui->xattr_names + host_ui->xattr_cnt;
 435         if (!buffer)
 436                 /*
 437                  * We should return the minimum buffer size which will fit a
 438                  * null-terminated list of all the extended attribute names.
 439                  */
 440                 return len;
 441
 442         if (len > size)
 443                 return -ERANGE;
 444
 445         lowest_xent_key(c, &key, host->i_ino);
 446         while (1) {
 447                 int type;
 448
 449                 xent = ubifs_tnc_next_ent(c, &key, &nm);
 450                 if (IS_ERR(xent)) {
 451                         err = PTR_ERR(xent);
 452                         break;
 453                 }
 454
 455                 nm.name = xent->name;
 456                 nm.len = le16_to_cpu(xent->nlen);
 457
 458                 type = check_namespace(&nm);
 459                 if (unlikely(type < 0)) {
 460                         err = type;
 461                         break;
 462                 }
 463
 464                 /* Show trusted namespace only for "power" users */
 465                 if (type != TRUSTED_XATTR || capable(CAP_SYS_ADMIN)) {
 466                         memcpy(buffer + written, nm.name, nm.len + 1);
 467                         written += nm.len + 1;
 468                 }
 469
 470                 kfree(pxent);
 471                 pxent = xent;
 472                 key_read(c, &xent->key, &key);
 473         }
 474
 475         kfree(pxent);
 476         if (err != -ENOENT) {
 477                 ubifs_err("cannot find next direntry, error %d", err);
 478                 return err;
 479         }
 480
 481         ubifs_assert(written <= size);
 482         return written;
 483 }
 484
 485 static int remove_xattr(struct ubifs_info *c, struct inode *host,
 486                         struct inode *inode, const struct qstr *nm)
 487 {
 488         int err;
 489         struct ubifs_inode *host_ui = ubifs_inode(host);
 490         struct ubifs_inode *ui = ubifs_inode(inode);
 491         struct ubifs_budget_req req = { .dirtied_ino = 2, .mod_dent = 1,
 492                                 .dirtied_ino_d = ALIGN(host_ui->data_len, 8) };
 493
 494         ubifs_assert(ui->data_len == inode->i_size);
 495
 496         err = ubifs_budget_space(c, &req);
 497         if (err)
 498                 return err;
 499
 500         mutex_lock(&host_ui->ui_mutex);
 501         host->i_ctime = ubifs_current_time(host);
 502         host_ui->xattr_cnt -= 1;
 503         host_ui->xattr_size -= CALC_DENT_SIZE(nm->len);
 504         host_ui->xattr_size -= CALC_XATTR_BYTES(ui->data_len);
 505         host_ui->xattr_names -= nm->len;
 506
 507         err = ubifs_jnl_delete_xattr(c, host, inode, nm);
 508         if (err)
 509                 goto out_cancel;
 510         mutex_unlock(&host_ui->ui_mutex);
 511
 512         ubifs_release_budget(c, &req);
 513         return 0;
 514
 515 out_cancel:
 516         host_ui->xattr_cnt += 1;
 517         host_ui->xattr_size += CALC_DENT_SIZE(nm->len);
 518         host_ui->xattr_size += CALC_XATTR_BYTES(ui->data_len);
 519         mutex_unlock(&host_ui->ui_mutex);
 520         ubifs_release_budget(c, &req);
 521         make_bad_inode(inode);
 522         return err;
 523 }
 524
 525 int ubifs_removexattr(struct dentry *dentry, const char *name)
 526 {
 527         struct inode *inode, *host = dentry->d_inode;
 528         struct ubifs_info *c = host->i_sb->s_fs_info;
 529         struct qstr nm = { .name = name, .len = strlen(name) };
 530         struct ubifs_dent_node *xent;
 531         union ubifs_key key;
 532         int err;
 533
 534         dbg_gen("xattr '%s', ino %lu ('%.*s')", name,
 535                 host->i_ino, dentry->d_name.len, dentry->d_name.name);
 536         ubifs_assert(mutex_is_locked(&host->i_mutex));
 537
 538         err = check_namespace(&nm);
 539         if (err < 0)
 540                 return err;
 541
 542         xent = kmalloc(UBIFS_MAX_XENT_NODE_SZ, GFP_NOFS);
 543         if (!xent)
 544                 return -ENOMEM;
 545
 546         xent_key_init(c, &key, host->i_ino, &nm);
 547         err = ubifs_tnc_lookup_nm(c, &key, xent, &nm);
 548         if (err) {
 549                 if (err == -ENOENT)
 550                         err = -ENODATA;
 551                 goto out_free;
 552         }
 553
 554         inode = iget_xattr(c, le64_to_cpu(xent->inum));
 555         if (IS_ERR(inode)) {
 556                 err = PTR_ERR(inode);
 557                 goto out_free;
 558         }
 559
 560         ubifs_assert(inode->i_nlink == 1);
 561         clear_nlink(inode);
 562         err = remove_xattr(c, host, inode, &nm);
 563         if (err)
 564                 set_nlink(inode, 1);
 565
 566         /* If @i_nlink is 0, 'iput()' will delete the inode */
 567         iput(inode);
 568
 569 out_free:
 570         kfree(xent);
 571         return err;
 572 }