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 *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         error = dquot_initialize(inode);
 441         if (error)
 442                 return error;
 443         down_write(&EXT2_I(inode)->xattr_sem);
 444         if (EXT2_I(inode)->i_file_acl) {
 445                 /* The inode already has an extended attribute block. */
 446                 bh = sb_bread(sb, EXT2_I(inode)->i_file_acl);
 447                 error = -EIO;
 448                 if (!bh)
 449                         goto cleanup;
 450                 ea_bdebug(bh, "b_count=%d, refcount=%d",
 451                         atomic_read(&(bh->b_count)),
 452                         le32_to_cpu(HDR(bh)->h_refcount));
 453                 header = HDR(bh);
 454                 end = bh->b_data + bh->b_size;
 455                 if (!ext2_xattr_header_valid(header)) {
 456 bad_block:
 457                         ext2_error(sb, "ext2_xattr_set",
 458                                 "inode %ld: bad block %d", inode->i_ino,
 459                                    EXT2_I(inode)->i_file_acl);
 460                         error = -EIO;
 461                         goto cleanup;
 462                 }
 463                 /*
 464                  * Find the named attribute. If not found, 'here' will point
 465                  * to entry where the new attribute should be inserted to
 466                  * maintain sorting.
 467                  */
 468                 last = FIRST_ENTRY(bh);
 469                 while (!IS_LAST_ENTRY(last)) {
 470                         if (!ext2_xattr_entry_valid(last, end, sb->s_blocksize))
 471                                 goto bad_block;
 472                         if (last->e_value_size) {
 473                                 size_t offs = le16_to_cpu(last->e_value_offs);
 474                                 if (offs < min_offs)
 475                                         min_offs = offs;
 476                         }
 477                         if (not_found > 0) {
 478                                 not_found = ext2_xattr_cmp_entry(name_index,
 479                                                                  name_len,
 480                                                                  name, last);
 481                                 if (not_found <= 0)
 482                                         here = last;
 483                         }
 484                         last = EXT2_XATTR_NEXT(last);
 485                 }
 486                 if (not_found > 0)
 487                         here = last;
 488
 489                 /* Check whether we have enough space left. */
 490                 free = min_offs - ((char*)last - (char*)header) - sizeof(__u32);
 491         } else {
 492                 /* We will use a new extended attribute block. */
 493                 free = sb->s_blocksize -
 494                         sizeof(struct ext2_xattr_header) - sizeof(__u32);
 495         }
 496
 497         if (not_found) {
 498                 /* Request to remove a nonexistent attribute? */
 499                 error = -ENODATA;
 500                 if (flags & XATTR_REPLACE)
 501                         goto cleanup;
 502                 error = 0;
 503                 if (value == NULL)
 504                         goto cleanup;
 505         } else {
 506                 /* Request to create an existing attribute? */
 507                 error = -EEXIST;
 508                 if (flags & XATTR_CREATE)
 509                         goto cleanup;
 510                 free += EXT2_XATTR_SIZE(le32_to_cpu(here->e_value_size));
 511                 free += EXT2_XATTR_LEN(name_len);
 512         }
 513         error = -ENOSPC;
 514         if (free < EXT2_XATTR_LEN(name_len) + EXT2_XATTR_SIZE(value_len))
 515                 goto cleanup;
 516
 517         /* Here we know that we can set the new attribute. */
 518
 519         if (header) {
 520                 int offset;
 521
 522                 lock_buffer(bh);
 523                 if (header->h_refcount == cpu_to_le32(1)) {
 524                         __u32 hash = le32_to_cpu(header->h_hash);
 525                         struct mb_cache_entry *oe;
 526
 527                         oe = mb_cache_entry_delete_or_get(EA_BLOCK_CACHE(inode),
 528                                         hash, bh->b_blocknr);
 529                         if (!oe) {
 530                                 ea_bdebug(bh, "modifying in-place");
 531                                 goto update_block;
 532                         }
 533                         /*
 534                          * Someone is trying to reuse the block, leave it alone
 535                          */
 536                         mb_cache_entry_put(EA_BLOCK_CACHE(inode), oe);
 537                 }
 538                 unlock_buffer(bh);
 539                 ea_bdebug(bh, "cloning");
 540                 header = kmemdup(HDR(bh), bh->b_size, GFP_KERNEL);
 541                 error = -ENOMEM;
 542                 if (header == NULL)
 543                         goto cleanup;
 544                 header->h_refcount = cpu_to_le32(1);
 545
 546                 offset = (char *)here - bh->b_data;
 547                 here = ENTRY((char *)header + offset);
 548                 offset = (char *)last - bh->b_data;
 549                 last = ENTRY((char *)header + offset);
 550         } else {
 551                 /* Allocate a buffer where we construct the new block. */
 552                 header = kzalloc(sb->s_blocksize, GFP_KERNEL);
 553                 error = -ENOMEM;
 554                 if (header == NULL)
 555                         goto cleanup;
 556                 end = (char *)header + sb->s_blocksize;
 557                 header->h_magic = cpu_to_le32(EXT2_XATTR_MAGIC);
 558                 header->h_blocks = header->h_refcount = cpu_to_le32(1);
 559                 last = here = ENTRY(header+1);
 560         }
 561
 562 update_block:
 563         /* Iff we are modifying the block in-place, bh is locked here. */
 564
 565         if (not_found) {
 566                 /* Insert the new name. */
 567                 size_t size = EXT2_XATTR_LEN(name_len);
 568                 size_t rest = (char *)last - (char *)here;
 569                 memmove((char *)here + size, here, rest);
 570                 memset(here, 0, size);
 571                 here->e_name_index = name_index;
 572                 here->e_name_len = name_len;
 573                 memcpy(here->e_name, name, name_len);
 574         } else {
 575                 if (here->e_value_size) {
 576                         char *first_val = (char *)header + min_offs;
 577                         size_t offs = le16_to_cpu(here->e_value_offs);
 578                         char *val = (char *)header + offs;
 579                         size_t size = EXT2_XATTR_SIZE(
 580                                 le32_to_cpu(here->e_value_size));
 581
 582                         if (size == EXT2_XATTR_SIZE(value_len)) {
 583                                 /* The old and the new value have the same
 584                                    size. Just replace. */
 585                                 here->e_value_size = cpu_to_le32(value_len);
 586                                 memset(val + size - EXT2_XATTR_PAD, 0,
 587                                        EXT2_XATTR_PAD); /* Clear pad bytes. */
 588                                 memcpy(val, value, value_len);
 589                                 goto skip_replace;
 590                         }
 591
 592                         /* Remove the old value. */
 593                         memmove(first_val + size, first_val, val - first_val);
 594                         memset(first_val, 0, size);
 595                         min_offs += size;
 596
 597                         /* Adjust all value offsets. */
 598                         last = ENTRY(header+1);
 599                         while (!IS_LAST_ENTRY(last)) {
 600                                 size_t o = le16_to_cpu(last->e_value_offs);
 601                                 if (o < offs)
 602                                         last->e_value_offs =
 603                                                 cpu_to_le16(o + size);
 604                                 last = EXT2_XATTR_NEXT(last);
 605                         }
 606
 607                         here->e_value_offs = 0;
 608                 }
 609                 if (value == NULL) {
 610                         /* Remove the old name. */
 611                         size_t size = EXT2_XATTR_LEN(name_len);
 612                         last = ENTRY((char *)last - size);
 613                         memmove(here, (char*)here + size,
 614                                 (char*)last - (char*)here);
 615                         memset(last, 0, size);
 616                 }
 617         }
 618
 619         if (value != NULL) {
 620                 /* Insert the new value. */
 621                 here->e_value_size = cpu_to_le32(value_len);
 622                 if (value_len) {
 623                         size_t size = EXT2_XATTR_SIZE(value_len);
 624                         char *val = (char *)header + min_offs - size;
 625                         here->e_value_offs =
 626                                 cpu_to_le16((char *)val - (char *)header);
 627                         memset(val + size - EXT2_XATTR_PAD, 0,
 628                                EXT2_XATTR_PAD); /* Clear the pad bytes. */
 629                         memcpy(val, value, value_len);
 630                 }
 631         }
 632
 633 skip_replace:
 634         if (IS_LAST_ENTRY(ENTRY(header+1))) {
 635                 /* This block is now empty. */
 636                 if (bh && header == HDR(bh))
 637                         unlock_buffer(bh);  /* we were modifying in-place. */
 638                 error = ext2_xattr_set2(inode, bh, NULL);
 639         } else {
 640                 ext2_xattr_rehash(header, here);
 641                 if (bh && header == HDR(bh))
 642                         unlock_buffer(bh);  /* we were modifying in-place. */
 643                 error = ext2_xattr_set2(inode, bh, header);
 644         }
 645
 646 cleanup:
 647         if (!(bh && header == HDR(bh)))
 648                 kfree(header);
 649         brelse(bh);
 650         up_write(&EXT2_I(inode)->xattr_sem);
 651
 652         return error;
 653 }
 654
 655 static void ext2_xattr_release_block(struct inode *inode,
 656                                      struct buffer_head *bh)
 657 {
 658         struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
 659
 660 retry_ref:
 661         lock_buffer(bh);
 662         if (HDR(bh)->h_refcount == cpu_to_le32(1)) {
 663                 __u32 hash = le32_to_cpu(HDR(bh)->h_hash);
 664                 struct mb_cache_entry *oe;
 665
 666                 /*
 667                  * This must happen under buffer lock to properly
 668                  * serialize with ext2_xattr_set() reusing the block.
 669                  */
 670                 oe = mb_cache_entry_delete_or_get(ea_block_cache, hash,
 671                                                   bh->b_blocknr);
 672                 if (oe) {
 673                         /*
 674                          * Someone is trying to reuse the block. Wait
 675                          * and retry.
 676                          */
 677                         unlock_buffer(bh);
 678                         mb_cache_entry_wait_unused(oe);
 679                         mb_cache_entry_put(ea_block_cache, oe);
 680                         goto retry_ref;
 681                 }
 682
 683                 /* Free the old block. */
 684                 ea_bdebug(bh, "freeing");
 685                 ext2_free_blocks(inode, bh->b_blocknr, 1);
 686                 /* We let our caller release bh, so we
 687                  * need to duplicate the buffer before. */
 688                 get_bh(bh);
 689                 bforget(bh);
 690                 unlock_buffer(bh);
 691         } else {
 692                 /* Decrement the refcount only. */
 693                 le32_add_cpu(&HDR(bh)->h_refcount, -1);
 694                 dquot_free_block(inode, 1);
 695                 mark_buffer_dirty(bh);
 696                 unlock_buffer(bh);
 697                 ea_bdebug(bh, "refcount now=%d",
 698                         le32_to_cpu(HDR(bh)->h_refcount));
 699                 if (IS_SYNC(inode))
 700                         sync_dirty_buffer(bh);
 701         }
 702 }
 703
 704 /*
 705  * Second half of ext2_xattr_set(): Update the file system.
 706  */
 707 static int
 708 ext2_xattr_set2(struct inode *inode, struct buffer_head *old_bh,
 709                 struct ext2_xattr_header *header)
 710 {
 711         struct super_block *sb = inode->i_sb;
 712         struct buffer_head *new_bh = NULL;
 713         int error;
 714         struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
 715
 716         if (header) {
 717                 new_bh = ext2_xattr_cache_find(inode, header);
 718                 if (new_bh) {
 719                         /* We found an identical block in the cache. */
 720                         if (new_bh == old_bh) {
 721                                 ea_bdebug(new_bh, "keeping this block");
 722                         } else {
 723                                 /* The old block is released after updating
 724                                    the inode.  */
 725                                 ea_bdebug(new_bh, "reusing block");
 726
 727                                 error = dquot_alloc_block(inode, 1);
 728                                 if (error) {
 729                                         unlock_buffer(new_bh);
 730                                         goto cleanup;
 731                                 }
 732                                 le32_add_cpu(&HDR(new_bh)->h_refcount, 1);
 733                                 ea_bdebug(new_bh, "refcount now=%d",
 734                                         le32_to_cpu(HDR(new_bh)->h_refcount));
 735                         }
 736                         unlock_buffer(new_bh);
 737                 } else if (old_bh && header == HDR(old_bh)) {
 738                         /* Keep this block. No need to lock the block as we
 739                            don't need to change the reference count. */
 740                         new_bh = old_bh;
 741                         get_bh(new_bh);
 742                         ext2_xattr_cache_insert(ea_block_cache, new_bh);
 743                 } else {
 744                         /* We need to allocate a new block */
 745                         ext2_fsblk_t goal = ext2_group_first_block_no(sb,
 746                                                 EXT2_I(inode)->i_block_group);
 747                         ext2_fsblk_t block = ext2_new_block(inode, goal, &error);
 748                         if (error)
 749                                 goto cleanup;
 750                         ea_idebug(inode, "creating block %lu", block);
 751
 752                         new_bh = sb_getblk(sb, block);
 753                         if (unlikely(!new_bh)) {
 754                                 ext2_free_blocks(inode, block, 1);
 755                                 mark_inode_dirty(inode);
 756                                 error = -ENOMEM;
 757                                 goto cleanup;
 758                         }
 759                         lock_buffer(new_bh);
 760                         memcpy(new_bh->b_data, header, new_bh->b_size);
 761                         set_buffer_uptodate(new_bh);
 762                         unlock_buffer(new_bh);
 763                         ext2_xattr_cache_insert(ea_block_cache, new_bh);
 764
 765                         ext2_xattr_update_super_block(sb);
 766                 }
 767                 mark_buffer_dirty(new_bh);
 768                 if (IS_SYNC(inode)) {
 769                         sync_dirty_buffer(new_bh);
 770                         error = -EIO;
 771                         if (buffer_req(new_bh) && !buffer_uptodate(new_bh))
 772                                 goto cleanup;
 773                 }
 774         }
 775
 776         /* Update the inode. */
 777         EXT2_I(inode)->i_file_acl = new_bh ? new_bh->b_blocknr : 0;
 778         inode->i_ctime = current_time(inode);
 779         if (IS_SYNC(inode)) {
 780                 error = sync_inode_metadata(inode, 1);
 781                 /* In case sync failed due to ENOSPC the inode was actually
 782                  * written (only some dirty data were not) so we just proceed
 783                  * as if nothing happened and cleanup the unused block */
 784                 if (error && error != -ENOSPC) {
 785                         if (new_bh && new_bh != old_bh) {
 786                                 dquot_free_block_nodirty(inode, 1);
 787                                 mark_inode_dirty(inode);
 788                         }
 789                         goto cleanup;
 790                 }
 791         } else
 792                 mark_inode_dirty(inode);
 793
 794         error = 0;
 795         if (old_bh && old_bh != new_bh) {
 796                 /*
 797                  * If there was an old block and we are no longer using it,
 798                  * release the old block.
 799                  */
 800                 ext2_xattr_release_block(inode, old_bh);
 801         }
 802
 803 cleanup:
 804         brelse(new_bh);
 805
 806         return error;
 807 }
 808
 809 /*
 810  * ext2_xattr_delete_inode()
 811  *
 812  * Free extended attribute resources associated with this inode. This
 813  * is called immediately before an inode is freed.
 814  */
 815 void
 816 ext2_xattr_delete_inode(struct inode *inode)
 817 {
 818         struct buffer_head *bh = NULL;
 819         struct ext2_sb_info *sbi = EXT2_SB(inode->i_sb);
 820
 821         /*
 822          * We are the only ones holding inode reference. The xattr_sem should
 823          * better be unlocked! We could as well just not acquire xattr_sem at
 824          * all but this makes the code more futureproof. OTOH we need trylock
 825          * here to avoid false-positive warning from lockdep about reclaim
 826          * circular dependency.
 827          */
 828         if (WARN_ON_ONCE(!down_write_trylock(&EXT2_I(inode)->xattr_sem)))
 829                 return;
 830         if (!EXT2_I(inode)->i_file_acl)
 831                 goto cleanup;
 832
 833         if (!ext2_data_block_valid(sbi, EXT2_I(inode)->i_file_acl, 1)) {
 834                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 835                         "inode %ld: xattr block %d is out of data blocks range",
 836                         inode->i_ino, EXT2_I(inode)->i_file_acl);
 837                 goto cleanup;
 838         }
 839
 840         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 841         if (!bh) {
 842                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 843                         "inode %ld: block %d read error", inode->i_ino,
 844                         EXT2_I(inode)->i_file_acl);
 845                 goto cleanup;
 846         }
 847         ea_bdebug(bh, "b_count=%d", atomic_read(&(bh->b_count)));
 848         if (!ext2_xattr_header_valid(HDR(bh))) {
 849                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 850                         "inode %ld: bad block %d", inode->i_ino,
 851                         EXT2_I(inode)->i_file_acl);
 852                 goto cleanup;
 853         }
 854         ext2_xattr_release_block(inode, bh);
 855         EXT2_I(inode)->i_file_acl = 0;
 856
 857 cleanup:
 858         brelse(bh);
 859         up_write(&EXT2_I(inode)->xattr_sem);
 860 }
 861
 862 /*
 863  * ext2_xattr_cache_insert()
 864  *
 865  * Create a new entry in the extended attribute cache, and insert
 866  * it unless such an entry is already in the cache.
 867  *
 868  * Returns 0, or a negative error number on failure.
 869  */
 870 static int
 871 ext2_xattr_cache_insert(struct mb_cache *cache, struct buffer_head *bh)
 872 {
 873         __u32 hash = le32_to_cpu(HDR(bh)->h_hash);
 874         int error;
 875
 876         error = mb_cache_entry_create(cache, GFP_NOFS, hash, bh->b_blocknr,
 877                                       true);
 878         if (error) {
 879                 if (error == -EBUSY) {
 880                         ea_bdebug(bh, "already in cache");
 881                         error = 0;
 882                 }
 883         } else
 884                 ea_bdebug(bh, "inserting [%x]", (int)hash);
 885         return error;
 886 }
 887
 888 /*
 889  * ext2_xattr_cmp()
 890  *
 891  * Compare two extended attribute blocks for equality.
 892  *
 893  * Returns 0 if the blocks are equal, 1 if they differ, and
 894  * a negative error number on errors.
 895  */
 896 static int
 897 ext2_xattr_cmp(struct ext2_xattr_header *header1,
 898                struct ext2_xattr_header *header2)
 899 {
 900         struct ext2_xattr_entry *entry1, *entry2;
 901
 902         entry1 = ENTRY(header1+1);
 903         entry2 = ENTRY(header2+1);
 904         while (!IS_LAST_ENTRY(entry1)) {
 905                 if (IS_LAST_ENTRY(entry2))
 906                         return 1;
 907                 if (entry1->e_hash != entry2->e_hash ||
 908                     entry1->e_name_index != entry2->e_name_index ||
 909                     entry1->e_name_len != entry2->e_name_len ||
 910                     entry1->e_value_size != entry2->e_value_size ||
 911                     memcmp(entry1->e_name, entry2->e_name, entry1->e_name_len))
 912                         return 1;
 913                 if (entry1->e_value_block != 0 || entry2->e_value_block != 0)
 914                         return -EIO;
 915                 if (memcmp((char *)header1 + le16_to_cpu(entry1->e_value_offs),
 916                            (char *)header2 + le16_to_cpu(entry2->e_value_offs),
 917                            le32_to_cpu(entry1->e_value_size)))
 918                         return 1;
 919
 920                 entry1 = EXT2_XATTR_NEXT(entry1);
 921                 entry2 = EXT2_XATTR_NEXT(entry2);
 922         }
 923         if (!IS_LAST_ENTRY(entry2))
 924                 return 1;
 925         return 0;
 926 }
 927
 928 /*
 929  * ext2_xattr_cache_find()
 930  *
 931  * Find an identical extended attribute block.
 932  *
 933  * Returns a locked buffer head to the block found, or NULL if such
 934  * a block was not found or an error occurred.
 935  */
 936 static struct buffer_head *
 937 ext2_xattr_cache_find(struct inode *inode, struct ext2_xattr_header *header)
 938 {
 939         __u32 hash = le32_to_cpu(header->h_hash);
 940         struct mb_cache_entry *ce;
 941         struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
 942
 943         if (!header->h_hash)
 944                 return NULL;  /* never share */
 945         ea_idebug(inode, "looking for cached blocks [%x]", (int)hash);
 946
 947         ce = mb_cache_entry_find_first(ea_block_cache, hash);
 948         while (ce) {
 949                 struct buffer_head *bh;
 950
 951                 bh = sb_bread(inode->i_sb, ce->e_value);
 952                 if (!bh) {
 953                         ext2_error(inode->i_sb, "ext2_xattr_cache_find",
 954                                 "inode %ld: block %ld read error",
 955                                 inode->i_ino, (unsigned long) ce->e_value);
 956                 } else {
 957                         lock_buffer(bh);
 958                         if (le32_to_cpu(HDR(bh)->h_refcount) >
 959                             EXT2_XATTR_REFCOUNT_MAX) {
 960                                 ea_idebug(inode, "block %ld refcount %d>%d",
 961                                           (unsigned long) ce->e_value,
 962                                           le32_to_cpu(HDR(bh)->h_refcount),
 963                                           EXT2_XATTR_REFCOUNT_MAX);
 964                         } else if (!ext2_xattr_cmp(header, HDR(bh))) {
 965                                 ea_bdebug(bh, "b_count=%d",
 966                                           atomic_read(&(bh->b_count)));
 967                                 mb_cache_entry_touch(ea_block_cache, ce);
 968                                 mb_cache_entry_put(ea_block_cache, ce);
 969                                 return bh;
 970                         }
 971                         unlock_buffer(bh);
 972                         brelse(bh);
 973                 }
 974                 ce = mb_cache_entry_find_next(ea_block_cache, ce);
 975         }
 976         return NULL;
 977 }
 978
 979 #define NAME_HASH_SHIFT 5
 980 #define VALUE_HASH_SHIFT 16
 981
 982 /*
 983  * ext2_xattr_hash_entry()
 984  *
 985  * Compute the hash of an extended attribute.
 986  */
 987 static inline void ext2_xattr_hash_entry(struct ext2_xattr_header *header,
 988                                          struct ext2_xattr_entry *entry)
 989 {
 990         __u32 hash = 0;
 991         char *name = entry->e_name;
 992         int n;
 993
 994         for (n=0; n < entry->e_name_len; n++) {
 995                 hash = (hash << NAME_HASH_SHIFT) ^
 996                        (hash >> (8*sizeof(hash) - NAME_HASH_SHIFT)) ^
 997                        *name++;
 998         }
 999
1000         if (entry->e_value_block == 0 && entry->e_value_size != 0) {
1001                 __le32 *value = (__le32 *)((char *)header +
1002                         le16_to_cpu(entry->e_value_offs));
1003                 for (n = (le32_to_cpu(entry->e_value_size) +
1004                      EXT2_XATTR_ROUND) >> EXT2_XATTR_PAD_BITS; n; n--) {
1005                         hash = (hash << VALUE_HASH_SHIFT) ^
1006                                (hash >> (8*sizeof(hash) - VALUE_HASH_SHIFT)) ^
1007                                le32_to_cpu(*value++);
1008                 }
1009         }
1010         entry->e_hash = cpu_to_le32(hash);
1011 }
1012
1013 #undef NAME_HASH_SHIFT
1014 #undef VALUE_HASH_SHIFT
1015
1016 #define BLOCK_HASH_SHIFT 16
1017
1018 /*
1019  * ext2_xattr_rehash()
1020  *
1021  * Re-compute the extended attribute hash value after an entry has changed.
1022  */
1023 static void ext2_xattr_rehash(struct ext2_xattr_header *header,
1024                               struct ext2_xattr_entry *entry)
1025 {
1026         struct ext2_xattr_entry *here;
1027         __u32 hash = 0;
1028
1029         ext2_xattr_hash_entry(header, entry);
1030         here = ENTRY(header+1);
1031         while (!IS_LAST_ENTRY(here)) {
1032                 if (!here->e_hash) {
1033                         /* Block is not shared if an entry's hash value == 0 */
1034                         hash = 0;
1035                         break;
1036                 }
1037                 hash = (hash << BLOCK_HASH_SHIFT) ^
1038                        (hash >> (8*sizeof(hash) - BLOCK_HASH_SHIFT)) ^
1039                        le32_to_cpu(here->e_hash);
1040                 here = EXT2_XATTR_NEXT(here);
1041         }
1042         header->h_hash = cpu_to_le32(hash);
1043 }
1044
1045 #undef BLOCK_HASH_SHIFT
1046
1047 #define HASH_BUCKET_BITS 10
1048
1049 struct mb_cache *ext2_xattr_create_cache(void)
1050 {
1051         return mb_cache_create(HASH_BUCKET_BITS);
1052 }
1053
1054 void ext2_xattr_destroy_cache(struct mb_cache *cache)
1055 {
1056         if (cache)
1057                 mb_cache_destroy(cache);
1058 }