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 <agruen@suse.de>
   6  *
   7  * Fix by Harrison Xing <harrison@mountainviewdata.com>.
   8  * Extended attributes for symlinks and special files added per
   9  *  suggestion of Luka Renko <luka.renko@hermes.si>.
  10  * xattr consolidation Copyright (c) 2004 James Morris <jmorris@redhat.com>,
  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 * const 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]  = &nop_posix_acl_access,
 105         [EXT2_XATTR_INDEX_POSIX_ACL_DEFAULT] = &nop_posix_acl_default,
 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 * const ext2_xattr_handlers[] = {
 114         &ext2_xattr_user_handler,
 115         &ext2_xattr_trusted_handler,
 116 #ifdef CONFIG_EXT2_FS_SECURITY
 117         &ext2_xattr_security_handler,
 118 #endif
 119         NULL
 120 };
 121
 122 #define EA_BLOCK_CACHE(inode)   (EXT2_SB(inode->i_sb)->s_ea_block_cache)
 123
 124 static inline const char *ext2_xattr_prefix(int name_index,
 125                                             struct dentry *dentry)
 126 {
 127         const struct xattr_handler *handler = NULL;
 128
 129         if (name_index > 0 && name_index < ARRAY_SIZE(ext2_xattr_handler_map))
 130                 handler = ext2_xattr_handler_map[name_index];
 131
 132         if (!xattr_handler_can_list(handler, dentry))
 133                 return NULL;
 134
 135         return xattr_prefix(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 char *prefix;
 337
 338                 prefix = ext2_xattr_prefix(entry->e_name_index, dentry);
 339                 if (prefix) {
 340                         size_t prefix_len = strlen(prefix);
 341                         size_t size = prefix_len + entry->e_name_len + 1;
 342
 343                         if (buffer) {
 344                                 if (size > rest) {
 345                                         error = -ERANGE;
 346                                         goto cleanup;
 347                                 }
 348                                 memcpy(buffer, prefix, prefix_len);
 349                                 buffer += prefix_len;
 350                                 memcpy(buffer, entry->e_name, entry->e_name_len);
 351                                 buffer += entry->e_name_len;
 352                                 *buffer++ = 0;
 353                         }
 354                         rest -= size;
 355                 }
 356         }
 357         error = buffer_size - rest;  /* total size */
 358
 359 cleanup:
 360         brelse(bh);
 361         up_read(&EXT2_I(inode)->xattr_sem);
 362
 363         return error;
 364 }
 365
 366 /*
 367  * Inode operation listxattr()
 368  *
 369  * d_inode(dentry)->i_mutex: don't care
 370  */
 371 ssize_t
 372 ext2_listxattr(struct dentry *dentry, char *buffer, size_t size)
 373 {
 374         return ext2_xattr_list(dentry, buffer, size);
 375 }
 376
 377 /*
 378  * If the EXT2_FEATURE_COMPAT_EXT_ATTR feature of this file system is
 379  * not set, set it.
 380  */
 381 static void ext2_xattr_update_super_block(struct super_block *sb)
 382 {
 383         if (EXT2_HAS_COMPAT_FEATURE(sb, EXT2_FEATURE_COMPAT_EXT_ATTR))
 384                 return;
 385
 386         spin_lock(&EXT2_SB(sb)->s_lock);
 387         ext2_update_dynamic_rev(sb);
 388         EXT2_SET_COMPAT_FEATURE(sb, EXT2_FEATURE_COMPAT_EXT_ATTR);
 389         spin_unlock(&EXT2_SB(sb)->s_lock);
 390         mark_buffer_dirty(EXT2_SB(sb)->s_sbh);
 391 }
 392
 393 /*
 394  * ext2_xattr_set()
 395  *
 396  * Create, replace or remove an extended attribute for this inode.  Value
 397  * is NULL to remove an existing extended attribute, and non-NULL to
 398  * either replace an existing extended attribute, or create a new extended
 399  * attribute. The flags XATTR_REPLACE and XATTR_CREATE
 400  * specify that an extended attribute must exist and must not exist
 401  * previous to the call, respectively.
 402  *
 403  * Returns 0, or a negative error number on failure.
 404  */
 405 int
 406 ext2_xattr_set(struct inode *inode, int name_index, const char *name,
 407                const void *value, size_t value_len, int flags)
 408 {
 409         struct super_block *sb = inode->i_sb;
 410         struct buffer_head *bh = NULL;
 411         struct ext2_xattr_header *header = NULL;
 412         struct ext2_xattr_entry *here = NULL, *last = NULL;
 413         size_t name_len, free, min_offs = sb->s_blocksize;
 414         int not_found = 1, error;
 415         char *end;
 416
 417         /*
 418          * header -- Points either into bh, or to a temporarily
 419          *           allocated buffer.
 420          * here -- The named entry found, or the place for inserting, within
 421          *         the block pointed to by header.
 422          * last -- Points right after the last named entry within the block
 423          *         pointed to by header.
 424          * min_offs -- The offset of the first value (values are aligned
 425          *             towards the end of the block).
 426          * end -- Points right after the block pointed to by header.
 427          */
 428
 429         ea_idebug(inode, "name=%d.%s, value=%p, value_len=%ld",
 430                   name_index, name, value, (long)value_len);
 431
 432         if (value == NULL)
 433                 value_len = 0;
 434         if (name == NULL)
 435                 return -EINVAL;
 436         name_len = strlen(name);
 437         if (name_len > 255 || value_len > sb->s_blocksize)
 438                 return -ERANGE;
 439         error = dquot_initialize(inode);
 440         if (error)
 441                 return error;
 442         down_write(&EXT2_I(inode)->xattr_sem);
 443         if (EXT2_I(inode)->i_file_acl) {
 444                 /* The inode already has an extended attribute block. */
 445                 bh = sb_bread(sb, EXT2_I(inode)->i_file_acl);
 446                 error = -EIO;
 447                 if (!bh)
 448                         goto cleanup;
 449                 ea_bdebug(bh, "b_count=%d, refcount=%d",
 450                         atomic_read(&(bh->b_count)),
 451                         le32_to_cpu(HDR(bh)->h_refcount));
 452                 header = HDR(bh);
 453                 end = bh->b_data + bh->b_size;
 454                 if (!ext2_xattr_header_valid(header)) {
 455 bad_block:
 456                         ext2_error(sb, "ext2_xattr_set",
 457                                 "inode %ld: bad block %d", inode->i_ino,
 458                                    EXT2_I(inode)->i_file_acl);
 459                         error = -EIO;
 460                         goto cleanup;
 461                 }
 462                 /*
 463                  * Find the named attribute. If not found, 'here' will point
 464                  * to entry where the new attribute should be inserted to
 465                  * maintain sorting.
 466                  */
 467                 last = FIRST_ENTRY(bh);
 468                 while (!IS_LAST_ENTRY(last)) {
 469                         if (!ext2_xattr_entry_valid(last, end, sb->s_blocksize))
 470                                 goto bad_block;
 471                         if (last->e_value_size) {
 472                                 size_t offs = le16_to_cpu(last->e_value_offs);
 473                                 if (offs < min_offs)
 474                                         min_offs = offs;
 475                         }
 476                         if (not_found > 0) {
 477                                 not_found = ext2_xattr_cmp_entry(name_index,
 478                                                                  name_len,
 479                                                                  name, last);
 480                                 if (not_found <= 0)
 481                                         here = last;
 482                         }
 483                         last = EXT2_XATTR_NEXT(last);
 484                 }
 485                 if (not_found > 0)
 486                         here = last;
 487
 488                 /* Check whether we have enough space left. */
 489                 free = min_offs - ((char*)last - (char*)header) - sizeof(__u32);
 490         } else {
 491                 /* We will use a new extended attribute block. */
 492                 free = sb->s_blocksize -
 493                         sizeof(struct ext2_xattr_header) - sizeof(__u32);
 494         }
 495
 496         if (not_found) {
 497                 /* Request to remove a nonexistent attribute? */
 498                 error = -ENODATA;
 499                 if (flags & XATTR_REPLACE)
 500                         goto cleanup;
 501                 error = 0;
 502                 if (value == NULL)
 503                         goto cleanup;
 504         } else {
 505                 /* Request to create an existing attribute? */
 506                 error = -EEXIST;
 507                 if (flags & XATTR_CREATE)
 508                         goto cleanup;
 509                 free += EXT2_XATTR_SIZE(le32_to_cpu(here->e_value_size));
 510                 free += EXT2_XATTR_LEN(name_len);
 511         }
 512         error = -ENOSPC;
 513         if (free < EXT2_XATTR_LEN(name_len) + EXT2_XATTR_SIZE(value_len))
 514                 goto cleanup;
 515
 516         /* Here we know that we can set the new attribute. */
 517
 518         if (header) {
 519                 int offset;
 520
 521                 lock_buffer(bh);
 522                 if (header->h_refcount == cpu_to_le32(1)) {
 523                         __u32 hash = le32_to_cpu(header->h_hash);
 524                         struct mb_cache_entry *oe;
 525
 526                         oe = mb_cache_entry_delete_or_get(EA_BLOCK_CACHE(inode),
 527                                         hash, bh->b_blocknr);
 528                         if (!oe) {
 529                                 ea_bdebug(bh, "modifying in-place");
 530                                 goto update_block;
 531                         }
 532                         /*
 533                          * Someone is trying to reuse the block, leave it alone
 534                          */
 535                         mb_cache_entry_put(EA_BLOCK_CACHE(inode), oe);
 536                 }
 537                 unlock_buffer(bh);
 538                 ea_bdebug(bh, "cloning");
 539                 header = kmemdup(HDR(bh), bh->b_size, GFP_KERNEL);
 540                 error = -ENOMEM;
 541                 if (header == NULL)
 542                         goto cleanup;
 543                 header->h_refcount = cpu_to_le32(1);
 544
 545                 offset = (char *)here - bh->b_data;
 546                 here = ENTRY((char *)header + offset);
 547                 offset = (char *)last - bh->b_data;
 548                 last = ENTRY((char *)header + offset);
 549         } else {
 550                 /* Allocate a buffer where we construct the new block. */
 551                 header = kzalloc(sb->s_blocksize, GFP_KERNEL);
 552                 error = -ENOMEM;
 553                 if (header == NULL)
 554                         goto cleanup;
 555                 header->h_magic = cpu_to_le32(EXT2_XATTR_MAGIC);
 556                 header->h_blocks = header->h_refcount = cpu_to_le32(1);
 557                 last = here = ENTRY(header+1);
 558         }
 559
 560 update_block:
 561         /* Iff we are modifying the block in-place, bh is locked here. */
 562
 563         if (not_found) {
 564                 /* Insert the new name. */
 565                 size_t size = EXT2_XATTR_LEN(name_len);
 566                 size_t rest = (char *)last - (char *)here;
 567                 memmove((char *)here + size, here, rest);
 568                 memset(here, 0, size);
 569                 here->e_name_index = name_index;
 570                 here->e_name_len = name_len;
 571                 memcpy(here->e_name, name, name_len);
 572         } else {
 573                 if (here->e_value_size) {
 574                         char *first_val = (char *)header + min_offs;
 575                         size_t offs = le16_to_cpu(here->e_value_offs);
 576                         char *val = (char *)header + offs;
 577                         size_t size = EXT2_XATTR_SIZE(
 578                                 le32_to_cpu(here->e_value_size));
 579
 580                         if (size == EXT2_XATTR_SIZE(value_len)) {
 581                                 /* The old and the new value have the same
 582                                    size. Just replace. */
 583                                 here->e_value_size = cpu_to_le32(value_len);
 584                                 memset(val + size - EXT2_XATTR_PAD, 0,
 585                                        EXT2_XATTR_PAD); /* Clear pad bytes. */
 586                                 memcpy(val, value, value_len);
 587                                 goto skip_replace;
 588                         }
 589
 590                         /* Remove the old value. */
 591                         memmove(first_val + size, first_val, val - first_val);
 592                         memset(first_val, 0, size);
 593                         min_offs += size;
 594
 595                         /* Adjust all value offsets. */
 596                         last = ENTRY(header+1);
 597                         while (!IS_LAST_ENTRY(last)) {
 598                                 size_t o = le16_to_cpu(last->e_value_offs);
 599                                 if (o < offs)
 600                                         last->e_value_offs =
 601                                                 cpu_to_le16(o + size);
 602                                 last = EXT2_XATTR_NEXT(last);
 603                         }
 604
 605                         here->e_value_offs = 0;
 606                 }
 607                 if (value == NULL) {
 608                         /* Remove the old name. */
 609                         size_t size = EXT2_XATTR_LEN(name_len);
 610                         last = ENTRY((char *)last - size);
 611                         memmove(here, (char*)here + size,
 612                                 (char*)last - (char*)here);
 613                         memset(last, 0, size);
 614                 }
 615         }
 616
 617         if (value != NULL) {
 618                 /* Insert the new value. */
 619                 here->e_value_size = cpu_to_le32(value_len);
 620                 if (value_len) {
 621                         size_t size = EXT2_XATTR_SIZE(value_len);
 622                         char *val = (char *)header + min_offs - size;
 623                         here->e_value_offs =
 624                                 cpu_to_le16((char *)val - (char *)header);
 625                         memset(val + size - EXT2_XATTR_PAD, 0,
 626                                EXT2_XATTR_PAD); /* Clear the pad bytes. */
 627                         memcpy(val, value, value_len);
 628                 }
 629         }
 630
 631 skip_replace:
 632         if (IS_LAST_ENTRY(ENTRY(header+1))) {
 633                 /* This block is now empty. */
 634                 if (bh && header == HDR(bh))
 635                         unlock_buffer(bh);  /* we were modifying in-place. */
 636                 error = ext2_xattr_set2(inode, bh, NULL);
 637         } else {
 638                 ext2_xattr_rehash(header, here);
 639                 if (bh && header == HDR(bh))
 640                         unlock_buffer(bh);  /* we were modifying in-place. */
 641                 error = ext2_xattr_set2(inode, bh, header);
 642         }
 643
 644 cleanup:
 645         if (!(bh && header == HDR(bh)))
 646                 kfree(header);
 647         brelse(bh);
 648         up_write(&EXT2_I(inode)->xattr_sem);
 649
 650         return error;
 651 }
 652
 653 static void ext2_xattr_release_block(struct inode *inode,
 654                                      struct buffer_head *bh)
 655 {
 656         struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
 657
 658 retry_ref:
 659         lock_buffer(bh);
 660         if (HDR(bh)->h_refcount == cpu_to_le32(1)) {
 661                 __u32 hash = le32_to_cpu(HDR(bh)->h_hash);
 662                 struct mb_cache_entry *oe;
 663
 664                 /*
 665                  * This must happen under buffer lock to properly
 666                  * serialize with ext2_xattr_set() reusing the block.
 667                  */
 668                 oe = mb_cache_entry_delete_or_get(ea_block_cache, hash,
 669                                                   bh->b_blocknr);
 670                 if (oe) {
 671                         /*
 672                          * Someone is trying to reuse the block. Wait
 673                          * and retry.
 674                          */
 675                         unlock_buffer(bh);
 676                         mb_cache_entry_wait_unused(oe);
 677                         mb_cache_entry_put(ea_block_cache, oe);
 678                         goto retry_ref;
 679                 }
 680
 681                 /* Free the old block. */
 682                 ea_bdebug(bh, "freeing");
 683                 ext2_free_blocks(inode, bh->b_blocknr, 1);
 684                 /* We let our caller release bh, so we
 685                  * need to duplicate the buffer before. */
 686                 get_bh(bh);
 687                 bforget(bh);
 688                 unlock_buffer(bh);
 689         } else {
 690                 /* Decrement the refcount only. */
 691                 le32_add_cpu(&HDR(bh)->h_refcount, -1);
 692                 dquot_free_block(inode, 1);
 693                 mark_buffer_dirty(bh);
 694                 unlock_buffer(bh);
 695                 ea_bdebug(bh, "refcount now=%d",
 696                         le32_to_cpu(HDR(bh)->h_refcount));
 697                 if (IS_SYNC(inode))
 698                         sync_dirty_buffer(bh);
 699         }
 700 }
 701
 702 /*
 703  * Second half of ext2_xattr_set(): Update the file system.
 704  */
 705 static int
 706 ext2_xattr_set2(struct inode *inode, struct buffer_head *old_bh,
 707                 struct ext2_xattr_header *header)
 708 {
 709         struct super_block *sb = inode->i_sb;
 710         struct buffer_head *new_bh = NULL;
 711         int error;
 712         struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
 713
 714         if (header) {
 715                 new_bh = ext2_xattr_cache_find(inode, header);
 716                 if (new_bh) {
 717                         /* We found an identical block in the cache. */
 718                         if (new_bh == old_bh) {
 719                                 ea_bdebug(new_bh, "keeping this block");
 720                         } else {
 721                                 /* The old block is released after updating
 722                                    the inode.  */
 723                                 ea_bdebug(new_bh, "reusing block");
 724
 725                                 error = dquot_alloc_block(inode, 1);
 726                                 if (error) {
 727                                         unlock_buffer(new_bh);
 728                                         goto cleanup;
 729                                 }
 730                                 le32_add_cpu(&HDR(new_bh)->h_refcount, 1);
 731                                 ea_bdebug(new_bh, "refcount now=%d",
 732                                         le32_to_cpu(HDR(new_bh)->h_refcount));
 733                         }
 734                         unlock_buffer(new_bh);
 735                 } else if (old_bh && header == HDR(old_bh)) {
 736                         /* Keep this block. No need to lock the block as we
 737                            don't need to change the reference count. */
 738                         new_bh = old_bh;
 739                         get_bh(new_bh);
 740                         ext2_xattr_cache_insert(ea_block_cache, new_bh);
 741                 } else {
 742                         /* We need to allocate a new block */
 743                         ext2_fsblk_t goal = ext2_group_first_block_no(sb,
 744                                                 EXT2_I(inode)->i_block_group);
 745                         unsigned long count = 1;
 746                         ext2_fsblk_t block = ext2_new_blocks(inode, goal,
 747                                                 &count, &error,
 748                                                 EXT2_ALLOC_NORESERVE);
 749                         if (error)
 750                                 goto cleanup;
 751                         ea_idebug(inode, "creating block %lu", block);
 752
 753                         new_bh = sb_getblk(sb, block);
 754                         if (unlikely(!new_bh)) {
 755                                 ext2_free_blocks(inode, block, 1);
 756                                 mark_inode_dirty(inode);
 757                                 error = -ENOMEM;
 758                                 goto cleanup;
 759                         }
 760                         lock_buffer(new_bh);
 761                         memcpy(new_bh->b_data, header, new_bh->b_size);
 762                         set_buffer_uptodate(new_bh);
 763                         unlock_buffer(new_bh);
 764                         ext2_xattr_cache_insert(ea_block_cache, new_bh);
 765
 766                         ext2_xattr_update_super_block(sb);
 767                 }
 768                 mark_buffer_dirty(new_bh);
 769                 if (IS_SYNC(inode)) {
 770                         sync_dirty_buffer(new_bh);
 771                         error = -EIO;
 772                         if (buffer_req(new_bh) && !buffer_uptodate(new_bh))
 773                                 goto cleanup;
 774                 }
 775         }
 776
 777         /* Update the inode. */
 778         EXT2_I(inode)->i_file_acl = new_bh ? new_bh->b_blocknr : 0;
 779         inode_set_ctime_current(inode);
 780         if (IS_SYNC(inode)) {
 781                 error = sync_inode_metadata(inode, 1);
 782                 /* In case sync failed due to ENOSPC the inode was actually
 783                  * written (only some dirty data were not) so we just proceed
 784                  * as if nothing happened and cleanup the unused block */
 785                 if (error && error != -ENOSPC) {
 786                         if (new_bh && new_bh != old_bh) {
 787                                 dquot_free_block_nodirty(inode, 1);
 788                                 mark_inode_dirty(inode);
 789                         }
 790                         goto cleanup;
 791                 }
 792         } else
 793                 mark_inode_dirty(inode);
 794
 795         error = 0;
 796         if (old_bh && old_bh != new_bh) {
 797                 /*
 798                  * If there was an old block and we are no longer using it,
 799                  * release the old block.
 800                  */
 801                 ext2_xattr_release_block(inode, old_bh);
 802         }
 803
 804 cleanup:
 805         brelse(new_bh);
 806
 807         return error;
 808 }
 809
 810 /*
 811  * ext2_xattr_delete_inode()
 812  *
 813  * Free extended attribute resources associated with this inode. This
 814  * is called immediately before an inode is freed.
 815  */
 816 void
 817 ext2_xattr_delete_inode(struct inode *inode)
 818 {
 819         struct buffer_head *bh = NULL;
 820         struct ext2_sb_info *sbi = EXT2_SB(inode->i_sb);
 821
 822         /*
 823          * We are the only ones holding inode reference. The xattr_sem should
 824          * better be unlocked! We could as well just not acquire xattr_sem at
 825          * all but this makes the code more futureproof. OTOH we need trylock
 826          * here to avoid false-positive warning from lockdep about reclaim
 827          * circular dependency.
 828          */
 829         if (WARN_ON_ONCE(!down_write_trylock(&EXT2_I(inode)->xattr_sem)))
 830                 return;
 831         if (!EXT2_I(inode)->i_file_acl)
 832                 goto cleanup;
 833
 834         if (!ext2_data_block_valid(sbi, EXT2_I(inode)->i_file_acl, 1)) {
 835                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 836                         "inode %ld: xattr block %d is out of data blocks range",
 837                         inode->i_ino, EXT2_I(inode)->i_file_acl);
 838                 goto cleanup;
 839         }
 840
 841         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 842         if (!bh) {
 843                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 844                         "inode %ld: block %d read error", inode->i_ino,
 845                         EXT2_I(inode)->i_file_acl);
 846                 goto cleanup;
 847         }
 848         ea_bdebug(bh, "b_count=%d", atomic_read(&(bh->b_count)));
 849         if (!ext2_xattr_header_valid(HDR(bh))) {
 850                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 851                         "inode %ld: bad block %d", inode->i_ino,
 852                         EXT2_I(inode)->i_file_acl);
 853                 goto cleanup;
 854         }
 855         ext2_xattr_release_block(inode, bh);
 856         EXT2_I(inode)->i_file_acl = 0;
 857
 858 cleanup:
 859         brelse(bh);
 860         up_write(&EXT2_I(inode)->xattr_sem);
 861 }
 862
 863 /*
 864  * ext2_xattr_cache_insert()
 865  *
 866  * Create a new entry in the extended attribute cache, and insert
 867  * it unless such an entry is already in the cache.
 868  *
 869  * Returns 0, or a negative error number on failure.
 870  */
 871 static int
 872 ext2_xattr_cache_insert(struct mb_cache *cache, struct buffer_head *bh)
 873 {
 874         __u32 hash = le32_to_cpu(HDR(bh)->h_hash);
 875         int error;
 876
 877         error = mb_cache_entry_create(cache, GFP_KERNEL, hash, bh->b_blocknr,
 878                                       true);
 879         if (error) {
 880                 if (error == -EBUSY) {
 881                         ea_bdebug(bh, "already in cache");
 882                         error = 0;
 883                 }
 884         } else
 885                 ea_bdebug(bh, "inserting [%x]", (int)hash);
 886         return error;
 887 }
 888
 889 /*
 890  * ext2_xattr_cmp()
 891  *
 892  * Compare two extended attribute blocks for equality.
 893  *
 894  * Returns 0 if the blocks are equal, 1 if they differ, and
 895  * a negative error number on errors.
 896  */
 897 static int
 898 ext2_xattr_cmp(struct ext2_xattr_header *header1,
 899                struct ext2_xattr_header *header2)
 900 {
 901         struct ext2_xattr_entry *entry1, *entry2;
 902
 903         entry1 = ENTRY(header1+1);
 904         entry2 = ENTRY(header2+1);
 905         while (!IS_LAST_ENTRY(entry1)) {
 906                 if (IS_LAST_ENTRY(entry2))
 907                         return 1;
 908                 if (entry1->e_hash != entry2->e_hash ||
 909                     entry1->e_name_index != entry2->e_name_index ||
 910                     entry1->e_name_len != entry2->e_name_len ||
 911                     entry1->e_value_size != entry2->e_value_size ||
 912                     memcmp(entry1->e_name, entry2->e_name, entry1->e_name_len))
 913                         return 1;
 914                 if (entry1->e_value_block != 0 || entry2->e_value_block != 0)
 915                         return -EIO;
 916                 if (memcmp((char *)header1 + le16_to_cpu(entry1->e_value_offs),
 917                            (char *)header2 + le16_to_cpu(entry2->e_value_offs),
 918                            le32_to_cpu(entry1->e_value_size)))
 919                         return 1;
 920
 921                 entry1 = EXT2_XATTR_NEXT(entry1);
 922                 entry2 = EXT2_XATTR_NEXT(entry2);
 923         }
 924         if (!IS_LAST_ENTRY(entry2))
 925                 return 1;
 926         return 0;
 927 }
 928
 929 /*
 930  * ext2_xattr_cache_find()
 931  *
 932  * Find an identical extended attribute block.
 933  *
 934  * Returns a locked buffer head to the block found, or NULL if such
 935  * a block was not found or an error occurred.
 936  */
 937 static struct buffer_head *
 938 ext2_xattr_cache_find(struct inode *inode, struct ext2_xattr_header *header)
 939 {
 940         __u32 hash = le32_to_cpu(header->h_hash);
 941         struct mb_cache_entry *ce;
 942         struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
 943
 944         if (!header->h_hash)
 945                 return NULL;  /* never share */
 946         ea_idebug(inode, "looking for cached blocks [%x]", (int)hash);
 947
 948         ce = mb_cache_entry_find_first(ea_block_cache, hash);
 949         while (ce) {
 950                 struct buffer_head *bh;
 951
 952                 bh = sb_bread(inode->i_sb, ce->e_value);
 953                 if (!bh) {
 954                         ext2_error(inode->i_sb, "ext2_xattr_cache_find",
 955                                 "inode %ld: block %ld read error",
 956                                 inode->i_ino, (unsigned long) ce->e_value);
 957                 } else {
 958                         lock_buffer(bh);
 959                         if (le32_to_cpu(HDR(bh)->h_refcount) >
 960                             EXT2_XATTR_REFCOUNT_MAX) {
 961                                 ea_idebug(inode, "block %ld refcount %d>%d",
 962                                           (unsigned long) ce->e_value,
 963                                           le32_to_cpu(HDR(bh)->h_refcount),
 964                                           EXT2_XATTR_REFCOUNT_MAX);
 965                         } else if (!ext2_xattr_cmp(header, HDR(bh))) {
 966                                 ea_bdebug(bh, "b_count=%d",
 967                                           atomic_read(&(bh->b_count)));
 968                                 mb_cache_entry_touch(ea_block_cache, ce);
 969                                 mb_cache_entry_put(ea_block_cache, ce);
 970                                 return bh;
 971                         }
 972                         unlock_buffer(bh);
 973                         brelse(bh);
 974                 }
 975                 ce = mb_cache_entry_find_next(ea_block_cache, ce);
 976         }
 977         return NULL;
 978 }
 979
 980 #define NAME_HASH_SHIFT 5
 981 #define VALUE_HASH_SHIFT 16
 982
 983 /*
 984  * ext2_xattr_hash_entry()
 985  *
 986  * Compute the hash of an extended attribute.
 987  */
 988 static inline void ext2_xattr_hash_entry(struct ext2_xattr_header *header,
 989                                          struct ext2_xattr_entry *entry)
 990 {
 991         __u32 hash = 0;
 992         char *name = entry->e_name;
 993         int n;
 994
 995         for (n=0; n < entry->e_name_len; n++) {
 996                 hash = (hash << NAME_HASH_SHIFT) ^
 997                        (hash >> (8*sizeof(hash) - NAME_HASH_SHIFT)) ^
 998                        *name++;
 999         }
1000
1001         if (entry->e_value_block == 0 && entry->e_value_size != 0) {
1002                 __le32 *value = (__le32 *)((char *)header +
1003                         le16_to_cpu(entry->e_value_offs));
1004                 for (n = (le32_to_cpu(entry->e_value_size) +
1005                      EXT2_XATTR_ROUND) >> EXT2_XATTR_PAD_BITS; n; n--) {
1006                         hash = (hash << VALUE_HASH_SHIFT) ^
1007                                (hash >> (8*sizeof(hash) - VALUE_HASH_SHIFT)) ^
1008                                le32_to_cpu(*value++);
1009                 }
1010         }
1011         entry->e_hash = cpu_to_le32(hash);
1012 }
1013
1014 #undef NAME_HASH_SHIFT
1015 #undef VALUE_HASH_SHIFT
1016
1017 #define BLOCK_HASH_SHIFT 16
1018
1019 /*
1020  * ext2_xattr_rehash()
1021  *
1022  * Re-compute the extended attribute hash value after an entry has changed.
1023  */
1024 static void ext2_xattr_rehash(struct ext2_xattr_header *header,
1025                               struct ext2_xattr_entry *entry)
1026 {
1027         struct ext2_xattr_entry *here;
1028         __u32 hash = 0;
1029
1030         ext2_xattr_hash_entry(header, entry);
1031         here = ENTRY(header+1);
1032         while (!IS_LAST_ENTRY(here)) {
1033                 if (!here->e_hash) {
1034                         /* Block is not shared if an entry's hash value == 0 */
1035                         hash = 0;
1036                         break;
1037                 }
1038                 hash = (hash << BLOCK_HASH_SHIFT) ^
1039                        (hash >> (8*sizeof(hash) - BLOCK_HASH_SHIFT)) ^
1040                        le32_to_cpu(here->e_hash);
1041                 here = EXT2_XATTR_NEXT(here);
1042         }
1043         header->h_hash = cpu_to_le32(hash);
1044 }
1045
1046 #undef BLOCK_HASH_SHIFT
1047
1048 #define HASH_BUCKET_BITS 10
1049
1050 struct mb_cache *ext2_xattr_create_cache(void)
1051 {
1052         return mb_cache_create(HASH_BUCKET_BITS);
1053 }
1054
1055 void ext2_xattr_destroy_cache(struct mb_cache *cache)
1056 {
1057         if (cache)
1058                 mb_cache_destroy(cache);
1059 }