fs/ext2/xattr.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * linux/fs/ext2/xattr.c
   4  *
   5  * Copyright (C) 2001-2003 Andreas Gruenbacher <[email protected]>
   6  *
   7  * Fix by Harrison Xing <[email protected]>.
   8  * Extended attributes for symlinks and special files added per
   9  *  suggestion of Luka Renko <[email protected]>.
  10  * xattr consolidation Copyright (c) 2004 James Morris <[email protected]>,
  11  *  Red Hat Inc.
  12  *
  13  */
  14
  15 /*
  16  * Extended attributes are stored on disk blocks allocated outside of
  17  * any inode. The i_file_acl field is then made to point to this allocated
  18  * block. If all extended attributes of an inode are identical, these
  19  * inodes may share the same extended attribute block. Such situations
  20  * are automatically detected by keeping a cache of recent attribute block
  21  * numbers and hashes over the block's contents in memory.
  22  *
  23  *
  24  * Extended attribute block layout:
  25  *
  26  *   +------------------+
  27  *   | header           |
  28  *   | entry 1          | |
  29  *   | entry 2          | | growing downwards
  30  *   | entry 3          | v
  31  *   | four null bytes  |
  32  *   | . . .            |
  33  *   | value 1          | ^
  34  *   | value 3          | | growing upwards
  35  *   | value 2          | |
  36  *   +------------------+
  37  *
  38  * The block header is followed by multiple entry descriptors. These entry
  39  * descriptors are variable in size, and aligned to EXT2_XATTR_PAD
  40  * byte boundaries. The entry descriptors are sorted by attribute name,
  41  * so that two extended attribute blocks can be compared efficiently.
  42  *
  43  * Attribute values are aligned to the end of the block, stored in
  44  * no specific order. They are also padded to EXT2_XATTR_PAD byte
  45  * boundaries. No additional gaps are left between them.
  46  *
  47  * Locking strategy
  48  * ----------------
  49  * EXT2_I(inode)->i_file_acl is protected by EXT2_I(inode)->xattr_sem.
  50  * EA blocks are only changed if they are exclusive to an inode, so
  51  * holding xattr_sem also means that nothing but the EA block's reference
  52  * count will change. Multiple writers to an EA block are synchronized
  53  * by the bh lock. No more than a single bh lock is held at any time
  54  * to avoid deadlocks.
  55  */
  56
  57 #include <linux/buffer_head.h>
  58 #include <linux/init.h>
  59 #include <linux/printk.h>
  60 #include <linux/slab.h>
  61 #include <linux/mbcache.h>
  62 #include <linux/quotaops.h>
  63 #include <linux/rwsem.h>
  64 #include <linux/security.h>
  65 #include "ext2.h"
  66 #include "xattr.h"
  67 #include "acl.h"
  68
  69 #define HDR(bh) ((struct ext2_xattr_header *)((bh)->b_data))
  70 #define ENTRY(ptr) ((struct ext2_xattr_entry *)(ptr))
  71 #define FIRST_ENTRY(bh) ENTRY(HDR(bh)+1)
  72 #define IS_LAST_ENTRY(entry) (*(__u32 *)(entry) == 0)
  73
  74 #ifdef EXT2_XATTR_DEBUG
  75 # define ea_idebug(inode, f...) do { \
  76                 printk(KERN_DEBUG "inode %s:%ld: ", \
  77                         inode->i_sb->s_id, inode->i_ino); \
  78                 printk(f); \
  79                 printk("\n"); \
  80         } while (0)
  81 # define ea_bdebug(bh, f...) do { \
  82                 printk(KERN_DEBUG "block %pg:%lu: ", \
  83                         bh->b_bdev, (unsigned long) bh->b_blocknr); \
  84                 printk(f); \
  85                 printk("\n"); \
  86         } while (0)
  87 #else
  88 # define ea_idebug(inode, f...) no_printk(f)
  89 # define ea_bdebug(bh, f...)    no_printk(f)
  90 #endif
  91
  92 static int ext2_xattr_set2(struct inode *, struct buffer_head *,
  93                            struct ext2_xattr_header *);
  94
  95 static int ext2_xattr_cache_insert(struct mb_cache *, struct buffer_head *);
  96 static struct buffer_head *ext2_xattr_cache_find(struct inode *,
  97                                                  struct ext2_xattr_header *);
  98 static void ext2_xattr_rehash(struct ext2_xattr_header *,
  99                               struct ext2_xattr_entry *);
 100
 101 static const struct xattr_handler *ext2_xattr_handler_map[] = {
 102         [EXT2_XATTR_INDEX_USER]              = &ext2_xattr_user_handler,
 103 #ifdef CONFIG_EXT2_FS_POSIX_ACL
 104         [EXT2_XATTR_INDEX_POSIX_ACL_ACCESS]  = &posix_acl_access_xattr_handler,
 105         [EXT2_XATTR_INDEX_POSIX_ACL_DEFAULT] = &posix_acl_default_xattr_handler,
 106 #endif
 107         [EXT2_XATTR_INDEX_TRUSTED]           = &ext2_xattr_trusted_handler,
 108 #ifdef CONFIG_EXT2_FS_SECURITY
 109         [EXT2_XATTR_INDEX_SECURITY]          = &ext2_xattr_security_handler,
 110 #endif
 111 };
 112
 113 const struct xattr_handler *ext2_xattr_handlers[] = {
 114         &ext2_xattr_user_handler,
 115         &ext2_xattr_trusted_handler,
 116 #ifdef CONFIG_EXT2_FS_POSIX_ACL
 117         &posix_acl_access_xattr_handler,
 118         &posix_acl_default_xattr_handler,
 119 #endif
 120 #ifdef CONFIG_EXT2_FS_SECURITY
 121         &ext2_xattr_security_handler,
 122 #endif
 123         NULL
 124 };
 125
 126 #define EA_BLOCK_CACHE(inode)   (EXT2_SB(inode->i_sb)->s_ea_block_cache)
 127
 128 static inline const struct xattr_handler *
 129 ext2_xattr_handler(int name_index)
 130 {
 131         const struct xattr_handler *handler = NULL;
 132
 133         if (name_index > 0 && name_index < ARRAY_SIZE(ext2_xattr_handler_map))
 134                 handler = ext2_xattr_handler_map[name_index];
 135         return handler;
 136 }
 137
 138 static bool
 139 ext2_xattr_header_valid(struct ext2_xattr_header *header)
 140 {
 141         if (header->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 142             header->h_blocks != cpu_to_le32(1))
 143                 return false;
 144
 145         return true;
 146 }
 147
 148 static bool
 149 ext2_xattr_entry_valid(struct ext2_xattr_entry *entry,
 150                        char *end, size_t end_offs)
 151 {
 152         struct ext2_xattr_entry *next;
 153         size_t size;
 154
 155         next = EXT2_XATTR_NEXT(entry);
 156         if ((char *)next >= end)
 157                 return false;
 158
 159         if (entry->e_value_block != 0)
 160                 return false;
 161
 162         size = le32_to_cpu(entry->e_value_size);
 163         if (size > end_offs ||
 164             le16_to_cpu(entry->e_value_offs) + size > end_offs)
 165                 return false;
 166
 167         return true;
 168 }
 169
 170 static int
 171 ext2_xattr_cmp_entry(int name_index, size_t name_len, const char *name,
 172                      struct ext2_xattr_entry *entry)
 173 {
 174         int cmp;
 175
 176         cmp = name_index - entry->e_name_index;
 177         if (!cmp)
 178                 cmp = name_len - entry->e_name_len;
 179         if (!cmp)
 180                 cmp = memcmp(name, entry->e_name, name_len);
 181
 182         return cmp;
 183 }
 184
 185 /*
 186  * ext2_xattr_get()
 187  *
 188  * Copy an extended attribute into the buffer
 189  * provided, or compute the buffer size required.
 190  * Buffer is NULL to compute the size of the buffer required.
 191  *
 192  * Returns a negative error number on failure, or the number of bytes
 193  * used / required on success.
 194  */
 195 int
 196 ext2_xattr_get(struct inode *inode, int name_index, const char *name,
 197                void *buffer, size_t buffer_size)
 198 {
 199         struct buffer_head *bh = NULL;
 200         struct ext2_xattr_entry *entry;
 201         size_t name_len, size;
 202         char *end;
 203         int error, not_found;
 204         struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
 205
 206         ea_idebug(inode, "name=%d.%s, buffer=%p, buffer_size=%ld",
 207                   name_index, name, buffer, (long)buffer_size);
 208
 209         if (name == NULL)
 210                 return -EINVAL;
 211         name_len = strlen(name);
 212         if (name_len > 255)
 213                 return -ERANGE;
 214
 215         down_read(&EXT2_I(inode)->xattr_sem);
 216         error = -ENODATA;
 217         if (!EXT2_I(inode)->i_file_acl)
 218                 goto cleanup;
 219         ea_idebug(inode, "reading block %d", EXT2_I(inode)->i_file_acl);
 220         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 221         error = -EIO;
 222         if (!bh)
 223                 goto cleanup;
 224         ea_bdebug(bh, "b_count=%d, refcount=%d",
 225                 atomic_read(&(bh->b_count)), le32_to_cpu(HDR(bh)->h_refcount));
 226         end = bh->b_data + bh->b_size;
 227         if (!ext2_xattr_header_valid(HDR(bh))) {
 228 bad_block:
 229                 ext2_error(inode->i_sb, "ext2_xattr_get",
 230                         "inode %ld: bad block %d", inode->i_ino,
 231                         EXT2_I(inode)->i_file_acl);
 232                 error = -EIO;
 233                 goto cleanup;
 234         }
 235
 236         /* find named attribute */
 237         entry = FIRST_ENTRY(bh);
 238         while (!IS_LAST_ENTRY(entry)) {
 239                 if (!ext2_xattr_entry_valid(entry, end,
 240                     inode->i_sb->s_blocksize))
 241                         goto bad_block;
 242
 243                 not_found = ext2_xattr_cmp_entry(name_index, name_len, name,
 244                                                  entry);
 245                 if (!not_found)
 246                         goto found;
 247                 if (not_found < 0)
 248                         break;
 249
 250                 entry = EXT2_XATTR_NEXT(entry);
 251         }
 252         if (ext2_xattr_cache_insert(ea_block_cache, bh))
 253                 ea_idebug(inode, "cache insert failed");
 254         error = -ENODATA;
 255         goto cleanup;
 256 found:
 257         size = le32_to_cpu(entry->e_value_size);
 258         if (ext2_xattr_cache_insert(ea_block_cache, bh))
 259                 ea_idebug(inode, "cache insert failed");
 260         if (buffer) {
 261                 error = -ERANGE;
 262                 if (size > buffer_size)
 263                         goto cleanup;
 264                 /* return value of attribute */
 265                 memcpy(buffer, bh->b_data + le16_to_cpu(entry->e_value_offs),
 266                         size);
 267         }
 268         error = size;
 269
 270 cleanup:
 271         brelse(bh);
 272         up_read(&EXT2_I(inode)->xattr_sem);
 273
 274         return error;
 275 }
 276
 277 /*
 278  * ext2_xattr_list()
 279  *
 280  * Copy a list of attribute names into the buffer
 281  * provided, or compute the buffer size required.
 282  * Buffer is NULL to compute the size of the buffer required.
 283  *
 284  * Returns a negative error number on failure, or the number of bytes
 285  * used / required on success.
 286  */
 287 static int
 288 ext2_xattr_list(struct dentry *dentry, char *buffer, size_t buffer_size)
 289 {
 290         struct inode *inode = d_inode(dentry);
 291         struct buffer_head *bh = NULL;
 292         struct ext2_xattr_entry *entry;
 293         char *end;
 294         size_t rest = buffer_size;
 295         int error;
 296         struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
 297
 298         ea_idebug(inode, "buffer=%p, buffer_size=%ld",
 299                   buffer, (long)buffer_size);
 300
 301         down_read(&EXT2_I(inode)->xattr_sem);
 302         error = 0;
 303         if (!EXT2_I(inode)->i_file_acl)
 304                 goto cleanup;
 305         ea_idebug(inode, "reading block %d", EXT2_I(inode)->i_file_acl);
 306         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 307         error = -EIO;
 308         if (!bh)
 309                 goto cleanup;
 310         ea_bdebug(bh, "b_count=%d, refcount=%d",
 311                 atomic_read(&(bh->b_count)), le32_to_cpu(HDR(bh)->h_refcount));
 312         end = bh->b_data + bh->b_size;
 313         if (!ext2_xattr_header_valid(HDR(bh))) {
 314 bad_block:
 315                 ext2_error(inode->i_sb, "ext2_xattr_list",
 316                         "inode %ld: bad block %d", inode->i_ino,
 317                         EXT2_I(inode)->i_file_acl);
 318                 error = -EIO;
 319                 goto cleanup;
 320         }
 321
 322         /* check the on-disk data structure */
 323         entry = FIRST_ENTRY(bh);
 324         while (!IS_LAST_ENTRY(entry)) {
 325                 if (!ext2_xattr_entry_valid(entry, end,
 326                     inode->i_sb->s_blocksize))
 327                         goto bad_block;
 328                 entry = EXT2_XATTR_NEXT(entry);
 329         }
 330         if (ext2_xattr_cache_insert(ea_block_cache, bh))
 331                 ea_idebug(inode, "cache insert failed");
 332
 333         /* list the attribute names */
 334         for (entry = FIRST_ENTRY(bh); !IS_LAST_ENTRY(entry);
 335              entry = EXT2_XATTR_NEXT(entry)) {
 336                 const struct xattr_handler *handler =
 337                         ext2_xattr_handler(entry->e_name_index);
 338
 339                 if (handler && (!handler->list || handler->list(dentry))) {
 340                         const char *prefix = handler->prefix ?: handler->name;
 341                         size_t prefix_len = strlen(prefix);
 342                         size_t size = prefix_len + entry->e_name_len + 1;
 343
 344                         if (buffer) {
 345                                 if (size > rest) {
 346                                         error = -ERANGE;
 347                                         goto cleanup;
 348                                 }
 349                                 memcpy(buffer, prefix, prefix_len);
 350                                 buffer += prefix_len;
 351                                 memcpy(buffer, entry->e_name, entry->e_name_len);
 352                                 buffer += entry->e_name_len;
 353                                 *buffer++ = 0;
 354                         }
 355                         rest -= size;
 356                 }
 357         }
 358         error = buffer_size - rest;  /* total size */
 359
 360 cleanup:
 361         brelse(bh);
 362         up_read(&EXT2_I(inode)->xattr_sem);
 363
 364         return error;
 365 }
 366
 367 /*
 368  * Inode operation listxattr()
 369  *
 370  * d_inode(dentry)->i_mutex: don't care
 371  */
 372 ssize_t
 373 ext2_listxattr(struct dentry *dentry, char *buffer, size_t size)
 374 {
 375         return ext2_xattr_list(dentry, buffer, size);
 376 }
 377
 378 /*
 379  * If the EXT2_FEATURE_COMPAT_EXT_ATTR feature of this file system is
 380  * not set, set it.
 381  */
 382 static void ext2_xattr_update_super_block(struct super_block *sb)
 383 {
 384         if (EXT2_HAS_COMPAT_FEATURE(sb, EXT2_FEATURE_COMPAT_EXT_ATTR))
 385                 return;
 386
 387         spin_lock(&EXT2_SB(sb)->s_lock);
 388         ext2_update_dynamic_rev(sb);
 389         EXT2_SET_COMPAT_FEATURE(sb, EXT2_FEATURE_COMPAT_EXT_ATTR);
 390         spin_unlock(&EXT2_SB(sb)->s_lock);
 391         mark_buffer_dirty(EXT2_SB(sb)->s_sbh);
 392 }
 393
 394 /*
 395  * ext2_xattr_set()
 396  *
 397  * Create, replace or remove an extended attribute for this inode.  Value
 398  * is NULL to remove an existing extended attribute, and non-NULL to
 399  * either replace an existing extended attribute, or create a new extended
 400  * attribute. The flags XATTR_REPLACE and XATTR_CREATE
 401  * specify that an extended attribute must exist and must not exist
 402  * previous to the call, respectively.
 403  *
 404  * Returns 0, or a negative error number on failure.
 405  */
 406 int
 407 ext2_xattr_set(struct inode *inode, int name_index, const char *name,
 408                const void *value, size_t value_len, int flags)
 409 {
 410         struct super_block *sb = inode->i_sb;
 411         struct buffer_head *bh = NULL;
 412         struct ext2_xattr_header *header = NULL;
 413         struct ext2_xattr_entry *here = NULL, *last = NULL;
 414         size_t name_len, free, min_offs = sb->s_blocksize;
 415         int not_found = 1, error;
 416         char *end;
 417
 418         /*
 419          * header -- Points either into bh, or to a temporarily
 420          *           allocated buffer.
 421          * here -- The named entry found, or the place for inserting, within
 422          *         the block pointed to by header.
 423          * last -- Points right after the last named entry within the block
 424          *         pointed to by header.
 425          * min_offs -- The offset of the first value (values are aligned
 426          *             towards the end of the block).
 427          * end -- Points right after the block pointed to by header.
 428          */
 429
 430         ea_idebug(inode, "name=%d.%s, value=%p, value_len=%ld",
 431                   name_index, name, value, (long)value_len);
 432
 433         if (value == NULL)
 434                 value_len = 0;
 435         if (name == NULL)
 436                 return -EINVAL;
 437         name_len = strlen(name);
 438         if (name_len > 255 || value_len > sb->s_blocksize)
 439                 return -ERANGE;
 440         down_write(&EXT2_I(inode)->xattr_sem);
 441         if (EXT2_I(inode)->i_file_acl) {
 442                 /* The inode already has an extended attribute block. */
 443                 bh = sb_bread(sb, EXT2_I(inode)->i_file_acl);
 444                 error = -EIO;
 445                 if (!bh)
 446                         goto cleanup;
 447                 ea_bdebug(bh, "b_count=%d, refcount=%d",
 448                         atomic_read(&(bh->b_count)),
 449                         le32_to_cpu(HDR(bh)->h_refcount));
 450                 header = HDR(bh);
 451                 end = bh->b_data + bh->b_size;
 452                 if (!ext2_xattr_header_valid(header)) {
 453 bad_block:
 454                         ext2_error(sb, "ext2_xattr_set",
 455                                 "inode %ld: bad block %d", inode->i_ino,
 456                                    EXT2_I(inode)->i_file_acl);
 457                         error = -EIO;
 458                         goto cleanup;
 459                 }
 460                 /*
 461                  * Find the named attribute. If not found, 'here' will point
 462                  * to entry where the new attribute should be inserted to
 463                  * maintain sorting.
 464                  */
 465                 last = FIRST_ENTRY(bh);
 466                 while (!IS_LAST_ENTRY(last)) {
 467                         if (!ext2_xattr_entry_valid(last, end, sb->s_blocksize))
 468                                 goto bad_block;
 469                         if (last->e_value_size) {
 470                                 size_t offs = le16_to_cpu(last->e_value_offs);
 471                                 if (offs < min_offs)
 472                                         min_offs = offs;
 473                         }
 474                         if (not_found > 0) {
 475                                 not_found = ext2_xattr_cmp_entry(name_index,
 476                                                                  name_len,
 477                                                                  name, last);
 478                                 if (not_found <= 0)
 479                                         here = last;
 480                         }
 481                         last = EXT2_XATTR_NEXT(last);
 482                 }
 483                 if (not_found > 0)
 484                         here = last;
 485
 486                 /* Check whether we have enough space left. */
 487                 free = min_offs - ((char*)last - (char*)header) - sizeof(__u32);
 488         } else {
 489                 /* We will use a new extended attribute block. */
 490                 free = sb->s_blocksize -
 491                         sizeof(struct ext2_xattr_header) - sizeof(__u32);
 492         }
 493
 494         if (not_found) {
 495                 /* Request to remove a nonexistent attribute? */
 496                 error = -ENODATA;
 497                 if (flags & XATTR_REPLACE)
 498                         goto cleanup;
 499                 error = 0;
 500                 if (value == NULL)
 501                         goto cleanup;
 502         } else {
 503                 /* Request to create an existing attribute? */
 504                 error = -EEXIST;
 505                 if (flags & XATTR_CREATE)
 506                         goto cleanup;
 507                 free += EXT2_XATTR_SIZE(le32_to_cpu(here->e_value_size));
 508                 free += EXT2_XATTR_LEN(name_len);
 509         }
 510         error = -ENOSPC;
 511         if (free < EXT2_XATTR_LEN(name_len) + EXT2_XATTR_SIZE(value_len))
 512                 goto cleanup;
 513
 514         /* Here we know that we can set the new attribute. */
 515
 516         if (header) {
 517                 /* assert(header == HDR(bh)); */
 518                 lock_buffer(bh);
 519                 if (header->h_refcount == cpu_to_le32(1)) {
 520                         __u32 hash = le32_to_cpu(header->h_hash);
 521
 522                         ea_bdebug(bh, "modifying in-place");
 523                         /*
 524                          * This must happen under buffer lock for
 525                          * ext2_xattr_set2() to reliably detect modified block
 526                          */
 527                         mb_cache_entry_delete(EA_BLOCK_CACHE(inode), hash,
 528                                               bh->b_blocknr);
 529
 530                         /* keep the buffer locked while modifying it. */
 531                 } else {
 532                         int offset;
 533
 534                         unlock_buffer(bh);
 535                         ea_bdebug(bh, "cloning");
 536                         header = kmemdup(HDR(bh), bh->b_size, GFP_KERNEL);
 537                         error = -ENOMEM;
 538                         if (header == NULL)
 539                                 goto cleanup;
 540                         header->h_refcount = cpu_to_le32(1);
 541
 542                         offset = (char *)here - bh->b_data;
 543                         here = ENTRY((char *)header + offset);
 544                         offset = (char *)last - bh->b_data;
 545                         last = ENTRY((char *)header + offset);
 546                 }
 547         } else {
 548                 /* Allocate a buffer where we construct the new block. */
 549                 header = kzalloc(sb->s_blocksize, GFP_KERNEL);
 550                 error = -ENOMEM;
 551                 if (header == NULL)
 552                         goto cleanup;
 553                 end = (char *)header + sb->s_blocksize;
 554                 header->h_magic = cpu_to_le32(EXT2_XATTR_MAGIC);
 555                 header->h_blocks = header->h_refcount = cpu_to_le32(1);
 556                 last = here = ENTRY(header+1);
 557         }
 558
 559         /* Iff we are modifying the block in-place, bh is locked here. */
 560
 561         if (not_found) {
 562                 /* Insert the new name. */
 563                 size_t size = EXT2_XATTR_LEN(name_len);
 564                 size_t rest = (char *)last - (char *)here;
 565                 memmove((char *)here + size, here, rest);
 566                 memset(here, 0, size);
 567                 here->e_name_index = name_index;
 568                 here->e_name_len = name_len;
 569                 memcpy(here->e_name, name, name_len);
 570         } else {
 571                 if (here->e_value_size) {
 572                         char *first_val = (char *)header + min_offs;
 573                         size_t offs = le16_to_cpu(here->e_value_offs);
 574                         char *val = (char *)header + offs;
 575                         size_t size = EXT2_XATTR_SIZE(
 576                                 le32_to_cpu(here->e_value_size));
 577
 578                         if (size == EXT2_XATTR_SIZE(value_len)) {
 579                                 /* The old and the new value have the same
 580                                    size. Just replace. */
 581                                 here->e_value_size = cpu_to_le32(value_len);
 582                                 memset(val + size - EXT2_XATTR_PAD, 0,
 583                                        EXT2_XATTR_PAD); /* Clear pad bytes. */
 584                                 memcpy(val, value, value_len);
 585                                 goto skip_replace;
 586                         }
 587
 588                         /* Remove the old value. */
 589                         memmove(first_val + size, first_val, val - first_val);
 590                         memset(first_val, 0, size);
 591                         here->e_value_offs = 0;
 592                         min_offs += size;
 593
 594                         /* Adjust all value offsets. */
 595                         last = ENTRY(header+1);
 596                         while (!IS_LAST_ENTRY(last)) {
 597                                 size_t o = le16_to_cpu(last->e_value_offs);
 598                                 if (o < offs)
 599                                         last->e_value_offs =
 600                                                 cpu_to_le16(o + size);
 601                                 last = EXT2_XATTR_NEXT(last);
 602                         }
 603                 }
 604                 if (value == NULL) {
 605                         /* Remove the old name. */
 606                         size_t size = EXT2_XATTR_LEN(name_len);
 607                         last = ENTRY((char *)last - size);
 608                         memmove(here, (char*)here + size,
 609                                 (char*)last - (char*)here);
 610                         memset(last, 0, size);
 611                 }
 612         }
 613
 614         if (value != NULL) {
 615                 /* Insert the new value. */
 616                 here->e_value_size = cpu_to_le32(value_len);
 617                 if (value_len) {
 618                         size_t size = EXT2_XATTR_SIZE(value_len);
 619                         char *val = (char *)header + min_offs - size;
 620                         here->e_value_offs =
 621                                 cpu_to_le16((char *)val - (char *)header);
 622                         memset(val + size - EXT2_XATTR_PAD, 0,
 623                                EXT2_XATTR_PAD); /* Clear the pad bytes. */
 624                         memcpy(val, value, value_len);
 625                 }
 626         }
 627
 628 skip_replace:
 629         if (IS_LAST_ENTRY(ENTRY(header+1))) {
 630                 /* This block is now empty. */
 631                 if (bh && header == HDR(bh))
 632                         unlock_buffer(bh);  /* we were modifying in-place. */
 633                 error = ext2_xattr_set2(inode, bh, NULL);
 634         } else {
 635                 ext2_xattr_rehash(header, here);
 636                 if (bh && header == HDR(bh))
 637                         unlock_buffer(bh);  /* we were modifying in-place. */
 638                 error = ext2_xattr_set2(inode, bh, header);
 639         }
 640
 641 cleanup:
 642         if (!(bh && header == HDR(bh)))
 643                 kfree(header);
 644         brelse(bh);
 645         up_write(&EXT2_I(inode)->xattr_sem);
 646
 647         return error;
 648 }
 649
 650 /*
 651  * Second half of ext2_xattr_set(): Update the file system.
 652  */
 653 static int
 654 ext2_xattr_set2(struct inode *inode, struct buffer_head *old_bh,
 655                 struct ext2_xattr_header *header)
 656 {
 657         struct super_block *sb = inode->i_sb;
 658         struct buffer_head *new_bh = NULL;
 659         int error;
 660         struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
 661
 662         if (header) {
 663                 new_bh = ext2_xattr_cache_find(inode, header);
 664                 if (new_bh) {
 665                         /* We found an identical block in the cache. */
 666                         if (new_bh == old_bh) {
 667                                 ea_bdebug(new_bh, "keeping this block");
 668                         } else {
 669                                 /* The old block is released after updating
 670                                    the inode.  */
 671                                 ea_bdebug(new_bh, "reusing block");
 672
 673                                 error = dquot_alloc_block(inode, 1);
 674                                 if (error) {
 675                                         unlock_buffer(new_bh);
 676                                         goto cleanup;
 677                                 }
 678                                 le32_add_cpu(&HDR(new_bh)->h_refcount, 1);
 679                                 ea_bdebug(new_bh, "refcount now=%d",
 680                                         le32_to_cpu(HDR(new_bh)->h_refcount));
 681                         }
 682                         unlock_buffer(new_bh);
 683                 } else if (old_bh && header == HDR(old_bh)) {
 684                         /* Keep this block. No need to lock the block as we
 685                            don't need to change the reference count. */
 686                         new_bh = old_bh;
 687                         get_bh(new_bh);
 688                         ext2_xattr_cache_insert(ea_block_cache, new_bh);
 689                 } else {
 690                         /* We need to allocate a new block */
 691                         ext2_fsblk_t goal = ext2_group_first_block_no(sb,
 692                                                 EXT2_I(inode)->i_block_group);
 693                         int block = ext2_new_block(inode, goal, &error);
 694                         if (error)
 695                                 goto cleanup;
 696                         ea_idebug(inode, "creating block %d", block);
 697
 698                         new_bh = sb_getblk(sb, block);
 699                         if (unlikely(!new_bh)) {
 700                                 ext2_free_blocks(inode, block, 1);
 701                                 mark_inode_dirty(inode);
 702                                 error = -ENOMEM;
 703                                 goto cleanup;
 704                         }
 705                         lock_buffer(new_bh);
 706                         memcpy(new_bh->b_data, header, new_bh->b_size);
 707                         set_buffer_uptodate(new_bh);
 708                         unlock_buffer(new_bh);
 709                         ext2_xattr_cache_insert(ea_block_cache, new_bh);
 710
 711                         ext2_xattr_update_super_block(sb);
 712                 }
 713                 mark_buffer_dirty(new_bh);
 714                 if (IS_SYNC(inode)) {
 715                         sync_dirty_buffer(new_bh);
 716                         error = -EIO;
 717                         if (buffer_req(new_bh) && !buffer_uptodate(new_bh))
 718                                 goto cleanup;
 719                 }
 720         }
 721
 722         /* Update the inode. */
 723         EXT2_I(inode)->i_file_acl = new_bh ? new_bh->b_blocknr : 0;
 724         inode->i_ctime = current_time(inode);
 725         if (IS_SYNC(inode)) {
 726                 error = sync_inode_metadata(inode, 1);
 727                 /* In case sync failed due to ENOSPC the inode was actually
 728                  * written (only some dirty data were not) so we just proceed
 729                  * as if nothing happened and cleanup the unused block */
 730                 if (error && error != -ENOSPC) {
 731                         if (new_bh && new_bh != old_bh) {
 732                                 dquot_free_block_nodirty(inode, 1);
 733                                 mark_inode_dirty(inode);
 734                         }
 735                         goto cleanup;
 736                 }
 737         } else
 738                 mark_inode_dirty(inode);
 739
 740         error = 0;
 741         if (old_bh && old_bh != new_bh) {
 742                 /*
 743                  * If there was an old block and we are no longer using it,
 744                  * release the old block.
 745                  */
 746                 lock_buffer(old_bh);
 747                 if (HDR(old_bh)->h_refcount == cpu_to_le32(1)) {
 748                         __u32 hash = le32_to_cpu(HDR(old_bh)->h_hash);
 749
 750                         /*
 751                          * This must happen under buffer lock for
 752                          * ext2_xattr_set2() to reliably detect freed block
 753                          */
 754                         mb_cache_entry_delete(ea_block_cache, hash,
 755                                               old_bh->b_blocknr);
 756                         /* Free the old block. */
 757                         ea_bdebug(old_bh, "freeing");
 758                         ext2_free_blocks(inode, old_bh->b_blocknr, 1);
 759                         mark_inode_dirty(inode);
 760                         /* We let our caller release old_bh, so we
 761                          * need to duplicate the buffer before. */
 762                         get_bh(old_bh);
 763                         bforget(old_bh);
 764                 } else {
 765                         /* Decrement the refcount only. */
 766                         le32_add_cpu(&HDR(old_bh)->h_refcount, -1);
 767                         dquot_free_block_nodirty(inode, 1);
 768                         mark_inode_dirty(inode);
 769                         mark_buffer_dirty(old_bh);
 770                         ea_bdebug(old_bh, "refcount now=%d",
 771                                 le32_to_cpu(HDR(old_bh)->h_refcount));
 772                 }
 773                 unlock_buffer(old_bh);
 774         }
 775
 776 cleanup:
 777         brelse(new_bh);
 778
 779         return error;
 780 }
 781
 782 /*
 783  * ext2_xattr_delete_inode()
 784  *
 785  * Free extended attribute resources associated with this inode. This
 786  * is called immediately before an inode is freed.
 787  */
 788 void
 789 ext2_xattr_delete_inode(struct inode *inode)
 790 {
 791         struct buffer_head *bh = NULL;
 792         struct ext2_sb_info *sbi = EXT2_SB(inode->i_sb);
 793
 794         /*
 795          * We are the only ones holding inode reference. The xattr_sem should
 796          * better be unlocked! We could as well just not acquire xattr_sem at
 797          * all but this makes the code more futureproof. OTOH we need trylock
 798          * here to avoid false-positive warning from lockdep about reclaim
 799          * circular dependency.
 800          */
 801         if (WARN_ON_ONCE(!down_write_trylock(&EXT2_I(inode)->xattr_sem)))
 802                 return;
 803         if (!EXT2_I(inode)->i_file_acl)
 804                 goto cleanup;
 805
 806         if (!ext2_data_block_valid(sbi, EXT2_I(inode)->i_file_acl, 1)) {
 807                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 808                         "inode %ld: xattr block %d is out of data blocks range",
 809                         inode->i_ino, EXT2_I(inode)->i_file_acl);
 810                 goto cleanup;
 811         }
 812
 813         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 814         if (!bh) {
 815                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 816                         "inode %ld: block %d read error", inode->i_ino,
 817                         EXT2_I(inode)->i_file_acl);
 818                 goto cleanup;
 819         }
 820         ea_bdebug(bh, "b_count=%d", atomic_read(&(bh->b_count)));
 821         if (!ext2_xattr_header_valid(HDR(bh))) {
 822                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 823                         "inode %ld: bad block %d", inode->i_ino,
 824                         EXT2_I(inode)->i_file_acl);
 825                 goto cleanup;
 826         }
 827         lock_buffer(bh);
 828         if (HDR(bh)->h_refcount == cpu_to_le32(1)) {
 829                 __u32 hash = le32_to_cpu(HDR(bh)->h_hash);
 830
 831                 /*
 832                  * This must happen under buffer lock for ext2_xattr_set2() to
 833                  * reliably detect freed block
 834                  */
 835                 mb_cache_entry_delete(EA_BLOCK_CACHE(inode), hash,
 836                                       bh->b_blocknr);
 837                 ext2_free_blocks(inode, EXT2_I(inode)->i_file_acl, 1);
 838                 get_bh(bh);
 839                 bforget(bh);
 840                 unlock_buffer(bh);
 841         } else {
 842                 le32_add_cpu(&HDR(bh)->h_refcount, -1);
 843                 ea_bdebug(bh, "refcount now=%d",
 844                         le32_to_cpu(HDR(bh)->h_refcount));
 845                 unlock_buffer(bh);
 846                 mark_buffer_dirty(bh);
 847                 if (IS_SYNC(inode))
 848                         sync_dirty_buffer(bh);
 849                 dquot_free_block_nodirty(inode, 1);
 850         }
 851         EXT2_I(inode)->i_file_acl = 0;
 852
 853 cleanup:
 854         brelse(bh);
 855         up_write(&EXT2_I(inode)->xattr_sem);
 856 }
 857
 858 /*
 859  * ext2_xattr_cache_insert()
 860  *
 861  * Create a new entry in the extended attribute cache, and insert
 862  * it unless such an entry is already in the cache.
 863  *
 864  * Returns 0, or a negative error number on failure.
 865  */
 866 static int
 867 ext2_xattr_cache_insert(struct mb_cache *cache, struct buffer_head *bh)
 868 {
 869         __u32 hash = le32_to_cpu(HDR(bh)->h_hash);
 870         int error;
 871
 872         error = mb_cache_entry_create(cache, GFP_NOFS, hash, bh->b_blocknr,
 873                                       true);
 874         if (error) {
 875                 if (error == -EBUSY) {
 876                         ea_bdebug(bh, "already in cache");
 877                         error = 0;
 878                 }
 879         } else
 880                 ea_bdebug(bh, "inserting [%x]", (int)hash);
 881         return error;
 882 }
 883
 884 /*
 885  * ext2_xattr_cmp()
 886  *
 887  * Compare two extended attribute blocks for equality.
 888  *
 889  * Returns 0 if the blocks are equal, 1 if they differ, and
 890  * a negative error number on errors.
 891  */
 892 static int
 893 ext2_xattr_cmp(struct ext2_xattr_header *header1,
 894                struct ext2_xattr_header *header2)
 895 {
 896         struct ext2_xattr_entry *entry1, *entry2;
 897
 898         entry1 = ENTRY(header1+1);
 899         entry2 = ENTRY(header2+1);
 900         while (!IS_LAST_ENTRY(entry1)) {
 901                 if (IS_LAST_ENTRY(entry2))
 902                         return 1;
 903                 if (entry1->e_hash != entry2->e_hash ||
 904                     entry1->e_name_index != entry2->e_name_index ||
 905                     entry1->e_name_len != entry2->e_name_len ||
 906                     entry1->e_value_size != entry2->e_value_size ||
 907                     memcmp(entry1->e_name, entry2->e_name, entry1->e_name_len))
 908                         return 1;
 909                 if (entry1->e_value_block != 0 || entry2->e_value_block != 0)
 910                         return -EIO;
 911                 if (memcmp((char *)header1 + le16_to_cpu(entry1->e_value_offs),
 912                            (char *)header2 + le16_to_cpu(entry2->e_value_offs),
 913                            le32_to_cpu(entry1->e_value_size)))
 914                         return 1;
 915
 916                 entry1 = EXT2_XATTR_NEXT(entry1);
 917                 entry2 = EXT2_XATTR_NEXT(entry2);
 918         }
 919         if (!IS_LAST_ENTRY(entry2))
 920                 return 1;
 921         return 0;
 922 }
 923
 924 /*
 925  * ext2_xattr_cache_find()
 926  *
 927  * Find an identical extended attribute block.
 928  *
 929  * Returns a locked buffer head to the block found, or NULL if such
 930  * a block was not found or an error occurred.
 931  */
 932 static struct buffer_head *
 933 ext2_xattr_cache_find(struct inode *inode, struct ext2_xattr_header *header)
 934 {
 935         __u32 hash = le32_to_cpu(header->h_hash);
 936         struct mb_cache_entry *ce;
 937         struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
 938
 939         if (!header->h_hash)
 940                 return NULL;  /* never share */
 941         ea_idebug(inode, "looking for cached blocks [%x]", (int)hash);
 942 again:
 943         ce = mb_cache_entry_find_first(ea_block_cache, hash);
 944         while (ce) {
 945                 struct buffer_head *bh;
 946
 947                 bh = sb_bread(inode->i_sb, ce->e_value);
 948                 if (!bh) {
 949                         ext2_error(inode->i_sb, "ext2_xattr_cache_find",
 950                                 "inode %ld: block %ld read error",
 951                                 inode->i_ino, (unsigned long) ce->e_value);
 952                 } else {
 953                         lock_buffer(bh);
 954                         /*
 955                          * We have to be careful about races with freeing or
 956                          * rehashing of xattr block. Once we hold buffer lock
 957                          * xattr block's state is stable so we can check
 958                          * whether the block got freed / rehashed or not.
 959                          * Since we unhash mbcache entry under buffer lock when
 960                          * freeing / rehashing xattr block, checking whether
 961                          * entry is still hashed is reliable.
 962                          */
 963                         if (hlist_bl_unhashed(&ce->e_hash_list)) {
 964                                 mb_cache_entry_put(ea_block_cache, ce);
 965                                 unlock_buffer(bh);
 966                                 brelse(bh);
 967                                 goto again;
 968                         } else if (le32_to_cpu(HDR(bh)->h_refcount) >
 969                                    EXT2_XATTR_REFCOUNT_MAX) {
 970                                 ea_idebug(inode, "block %ld refcount %d>%d",
 971                                           (unsigned long) ce->e_value,
 972                                           le32_to_cpu(HDR(bh)->h_refcount),
 973                                           EXT2_XATTR_REFCOUNT_MAX);
 974                         } else if (!ext2_xattr_cmp(header, HDR(bh))) {
 975                                 ea_bdebug(bh, "b_count=%d",
 976                                           atomic_read(&(bh->b_count)));
 977                                 mb_cache_entry_touch(ea_block_cache, ce);
 978                                 mb_cache_entry_put(ea_block_cache, ce);
 979                                 return bh;
 980                         }
 981                         unlock_buffer(bh);
 982                         brelse(bh);
 983                 }
 984                 ce = mb_cache_entry_find_next(ea_block_cache, ce);
 985         }
 986         return NULL;
 987 }
 988
 989 #define NAME_HASH_SHIFT 5
 990 #define VALUE_HASH_SHIFT 16
 991
 992 /*
 993  * ext2_xattr_hash_entry()
 994  *
 995  * Compute the hash of an extended attribute.
 996  */
 997 static inline void ext2_xattr_hash_entry(struct ext2_xattr_header *header,
 998                                          struct ext2_xattr_entry *entry)
 999 {
1000         __u32 hash = 0;
1001         char *name = entry->e_name;
1002         int n;
1003
1004         for (n=0; n < entry->e_name_len; n++) {
1005                 hash = (hash << NAME_HASH_SHIFT) ^
1006                        (hash >> (8*sizeof(hash) - NAME_HASH_SHIFT)) ^
1007                        *name++;
1008         }
1009
1010         if (entry->e_value_block == 0 && entry->e_value_size != 0) {
1011                 __le32 *value = (__le32 *)((char *)header +
1012                         le16_to_cpu(entry->e_value_offs));
1013                 for (n = (le32_to_cpu(entry->e_value_size) +
1014                      EXT2_XATTR_ROUND) >> EXT2_XATTR_PAD_BITS; n; n--) {
1015                         hash = (hash << VALUE_HASH_SHIFT) ^
1016                                (hash >> (8*sizeof(hash) - VALUE_HASH_SHIFT)) ^
1017                                le32_to_cpu(*value++);
1018                 }
1019         }
1020         entry->e_hash = cpu_to_le32(hash);
1021 }
1022
1023 #undef NAME_HASH_SHIFT
1024 #undef VALUE_HASH_SHIFT
1025
1026 #define BLOCK_HASH_SHIFT 16
1027
1028 /*
1029  * ext2_xattr_rehash()
1030  *
1031  * Re-compute the extended attribute hash value after an entry has changed.
1032  */
1033 static void ext2_xattr_rehash(struct ext2_xattr_header *header,
1034                               struct ext2_xattr_entry *entry)
1035 {
1036         struct ext2_xattr_entry *here;
1037         __u32 hash = 0;
1038
1039         ext2_xattr_hash_entry(header, entry);
1040         here = ENTRY(header+1);
1041         while (!IS_LAST_ENTRY(here)) {
1042                 if (!here->e_hash) {
1043                         /* Block is not shared if an entry's hash value == 0 */
1044                         hash = 0;
1045                         break;
1046                 }
1047                 hash = (hash << BLOCK_HASH_SHIFT) ^
1048                        (hash >> (8*sizeof(hash) - BLOCK_HASH_SHIFT)) ^
1049                        le32_to_cpu(here->e_hash);
1050                 here = EXT2_XATTR_NEXT(here);
1051         }
1052         header->h_hash = cpu_to_le32(hash);
1053 }
1054
1055 #undef BLOCK_HASH_SHIFT
1056
1057 #define HASH_BUCKET_BITS 10
1058
1059 struct mb_cache *ext2_xattr_create_cache(void)
1060 {
1061         return mb_cache_create(HASH_BUCKET_BITS);
1062 }
1063
1064 void ext2_xattr_destroy_cache(struct mb_cache *cache)
1065 {
1066         if (cache)
1067                 mb_cache_destroy(cache);
1068 }