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/slab.h>
  60 #include <linux/mbcache.h>
  61 #include <linux/quotaops.h>
  62 #include <linux/rwsem.h>
  63 #include <linux/security.h>
  64 #include "ext2.h"
  65 #include "xattr.h"
  66 #include "acl.h"
  67
  68 #define HDR(bh) ((struct ext2_xattr_header *)((bh)->b_data))
  69 #define ENTRY(ptr) ((struct ext2_xattr_entry *)(ptr))
  70 #define FIRST_ENTRY(bh) ENTRY(HDR(bh)+1)
  71 #define IS_LAST_ENTRY(entry) (*(__u32 *)(entry) == 0)
  72
  73 #ifdef EXT2_XATTR_DEBUG
  74 # define ea_idebug(inode, f...) do { \
  75                 printk(KERN_DEBUG "inode %s:%ld: ", \
  76                         inode->i_sb->s_id, inode->i_ino); \
  77                 printk(f); \
  78                 printk("\n"); \
  79         } while (0)
  80 # define ea_bdebug(bh, f...) do { \
  81                 printk(KERN_DEBUG "block %pg:%lu: ", \
  82                         bh->b_bdev, (unsigned long) bh->b_blocknr); \
  83                 printk(f); \
  84                 printk("\n"); \
  85         } while (0)
  86 #else
  87 # define ea_idebug(f...)
  88 # define ea_bdebug(f...)
  89 #endif
  90
  91 static int ext2_xattr_set2(struct inode *, struct buffer_head *,
  92                            struct ext2_xattr_header *);
  93
  94 static int ext2_xattr_cache_insert(struct mb_cache *, struct buffer_head *);
  95 static struct buffer_head *ext2_xattr_cache_find(struct inode *,
  96                                                  struct ext2_xattr_header *);
  97 static void ext2_xattr_rehash(struct ext2_xattr_header *,
  98                               struct ext2_xattr_entry *);
  99
 100 static const struct xattr_handler *ext2_xattr_handler_map[] = {
 101         [EXT2_XATTR_INDEX_USER]              = &ext2_xattr_user_handler,
 102 #ifdef CONFIG_EXT2_FS_POSIX_ACL
 103         [EXT2_XATTR_INDEX_POSIX_ACL_ACCESS]  = &posix_acl_access_xattr_handler,
 104         [EXT2_XATTR_INDEX_POSIX_ACL_DEFAULT] = &posix_acl_default_xattr_handler,
 105 #endif
 106         [EXT2_XATTR_INDEX_TRUSTED]           = &ext2_xattr_trusted_handler,
 107 #ifdef CONFIG_EXT2_FS_SECURITY
 108         [EXT2_XATTR_INDEX_SECURITY]          = &ext2_xattr_security_handler,
 109 #endif
 110 };
 111
 112 const struct xattr_handler *ext2_xattr_handlers[] = {
 113         &ext2_xattr_user_handler,
 114         &ext2_xattr_trusted_handler,
 115 #ifdef CONFIG_EXT2_FS_POSIX_ACL
 116         &posix_acl_access_xattr_handler,
 117         &posix_acl_default_xattr_handler,
 118 #endif
 119 #ifdef CONFIG_EXT2_FS_SECURITY
 120         &ext2_xattr_security_handler,
 121 #endif
 122         NULL
 123 };
 124
 125 #define EA_BLOCK_CACHE(inode)   (EXT2_SB(inode->i_sb)->s_ea_block_cache)
 126
 127 static inline const struct xattr_handler *
 128 ext2_xattr_handler(int name_index)
 129 {
 130         const struct xattr_handler *handler = NULL;
 131
 132         if (name_index > 0 && name_index < ARRAY_SIZE(ext2_xattr_handler_map))
 133                 handler = ext2_xattr_handler_map[name_index];
 134         return handler;
 135 }
 136
 137 static bool
 138 ext2_xattr_header_valid(struct ext2_xattr_header *header)
 139 {
 140         if (header->h_magic != cpu_to_le32(EXT2_XATTR_MAGIC) ||
 141             header->h_blocks != cpu_to_le32(1))
 142                 return false;
 143
 144         return true;
 145 }
 146
 147 static bool
 148 ext2_xattr_entry_valid(struct ext2_xattr_entry *entry,
 149                        char *end, size_t end_offs)
 150 {
 151         struct ext2_xattr_entry *next;
 152         size_t size;
 153
 154         next = EXT2_XATTR_NEXT(entry);
 155         if ((char *)next >= end)
 156                 return false;
 157
 158         if (entry->e_value_block != 0)
 159                 return false;
 160
 161         size = le32_to_cpu(entry->e_value_size);
 162         if (size > end_offs ||
 163             le16_to_cpu(entry->e_value_offs) + size > end_offs)
 164                 return false;
 165
 166         return true;
 167 }
 168
 169 static int
 170 ext2_xattr_cmp_entry(int name_index, size_t name_len, const char *name,
 171                      struct ext2_xattr_entry *entry)
 172 {
 173         int cmp;
 174
 175         cmp = name_index - entry->e_name_index;
 176         if (!cmp)
 177                 cmp = name_len - entry->e_name_len;
 178         if (!cmp)
 179                 cmp = memcmp(name, entry->e_name, name_len);
 180
 181         return cmp;
 182 }
 183
 184 /*
 185  * ext2_xattr_get()
 186  *
 187  * Copy an extended attribute into the buffer
 188  * provided, or compute the buffer size required.
 189  * Buffer is NULL to compute the size of the buffer required.
 190  *
 191  * Returns a negative error number on failure, or the number of bytes
 192  * used / required on success.
 193  */
 194 int
 195 ext2_xattr_get(struct inode *inode, int name_index, const char *name,
 196                void *buffer, size_t buffer_size)
 197 {
 198         struct buffer_head *bh = NULL;
 199         struct ext2_xattr_entry *entry;
 200         size_t name_len, size;
 201         char *end;
 202         int error, not_found;
 203         struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
 204
 205         ea_idebug(inode, "name=%d.%s, buffer=%p, buffer_size=%ld",
 206                   name_index, name, buffer, (long)buffer_size);
 207
 208         if (name == NULL)
 209                 return -EINVAL;
 210         name_len = strlen(name);
 211         if (name_len > 255)
 212                 return -ERANGE;
 213
 214         down_read(&EXT2_I(inode)->xattr_sem);
 215         error = -ENODATA;
 216         if (!EXT2_I(inode)->i_file_acl)
 217                 goto cleanup;
 218         ea_idebug(inode, "reading block %d", EXT2_I(inode)->i_file_acl);
 219         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 220         error = -EIO;
 221         if (!bh)
 222                 goto cleanup;
 223         ea_bdebug(bh, "b_count=%d, refcount=%d",
 224                 atomic_read(&(bh->b_count)), le32_to_cpu(HDR(bh)->h_refcount));
 225         end = bh->b_data + bh->b_size;
 226         if (!ext2_xattr_header_valid(HDR(bh))) {
 227 bad_block:
 228                 ext2_error(inode->i_sb, "ext2_xattr_get",
 229                         "inode %ld: bad block %d", inode->i_ino,
 230                         EXT2_I(inode)->i_file_acl);
 231                 error = -EIO;
 232                 goto cleanup;
 233         }
 234
 235         /* find named attribute */
 236         entry = FIRST_ENTRY(bh);
 237         while (!IS_LAST_ENTRY(entry)) {
 238                 if (!ext2_xattr_entry_valid(entry, end,
 239                     inode->i_sb->s_blocksize))
 240                         goto bad_block;
 241
 242                 not_found = ext2_xattr_cmp_entry(name_index, name_len, name,
 243                                                  entry);
 244                 if (!not_found)
 245                         goto found;
 246                 if (not_found < 0)
 247                         break;
 248
 249                 entry = EXT2_XATTR_NEXT(entry);
 250         }
 251         if (ext2_xattr_cache_insert(ea_block_cache, bh))
 252                 ea_idebug(inode, "cache insert failed");
 253         error = -ENODATA;
 254         goto cleanup;
 255 found:
 256         size = le32_to_cpu(entry->e_value_size);
 257         if (ext2_xattr_cache_insert(ea_block_cache, bh))
 258                 ea_idebug(inode, "cache insert failed");
 259         if (buffer) {
 260                 error = -ERANGE;
 261                 if (size > buffer_size)
 262                         goto cleanup;
 263                 /* return value of attribute */
 264                 memcpy(buffer, bh->b_data + le16_to_cpu(entry->e_value_offs),
 265                         size);
 266         }
 267         error = size;
 268
 269 cleanup:
 270         brelse(bh);
 271         up_read(&EXT2_I(inode)->xattr_sem);
 272
 273         return error;
 274 }
 275
 276 /*
 277  * ext2_xattr_list()
 278  *
 279  * Copy a list of attribute names into the buffer
 280  * provided, or compute the buffer size required.
 281  * Buffer is NULL to compute the size of the buffer required.
 282  *
 283  * Returns a negative error number on failure, or the number of bytes
 284  * used / required on success.
 285  */
 286 static int
 287 ext2_xattr_list(struct dentry *dentry, char *buffer, size_t buffer_size)
 288 {
 289         struct inode *inode = d_inode(dentry);
 290         struct buffer_head *bh = NULL;
 291         struct ext2_xattr_entry *entry;
 292         char *end;
 293         size_t rest = buffer_size;
 294         int error;
 295         struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
 296
 297         ea_idebug(inode, "buffer=%p, buffer_size=%ld",
 298                   buffer, (long)buffer_size);
 299
 300         down_read(&EXT2_I(inode)->xattr_sem);
 301         error = 0;
 302         if (!EXT2_I(inode)->i_file_acl)
 303                 goto cleanup;
 304         ea_idebug(inode, "reading block %d", EXT2_I(inode)->i_file_acl);
 305         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 306         error = -EIO;
 307         if (!bh)
 308                 goto cleanup;
 309         ea_bdebug(bh, "b_count=%d, refcount=%d",
 310                 atomic_read(&(bh->b_count)), le32_to_cpu(HDR(bh)->h_refcount));
 311         end = bh->b_data + bh->b_size;
 312         if (!ext2_xattr_header_valid(HDR(bh))) {
 313 bad_block:
 314                 ext2_error(inode->i_sb, "ext2_xattr_list",
 315                         "inode %ld: bad block %d", inode->i_ino,
 316                         EXT2_I(inode)->i_file_acl);
 317                 error = -EIO;
 318                 goto cleanup;
 319         }
 320
 321         /* check the on-disk data structure */
 322         entry = FIRST_ENTRY(bh);
 323         while (!IS_LAST_ENTRY(entry)) {
 324                 if (!ext2_xattr_entry_valid(entry, end,
 325                     inode->i_sb->s_blocksize))
 326                         goto bad_block;
 327                 entry = EXT2_XATTR_NEXT(entry);
 328         }
 329         if (ext2_xattr_cache_insert(ea_block_cache, bh))
 330                 ea_idebug(inode, "cache insert failed");
 331
 332         /* list the attribute names */
 333         for (entry = FIRST_ENTRY(bh); !IS_LAST_ENTRY(entry);
 334              entry = EXT2_XATTR_NEXT(entry)) {
 335                 const struct xattr_handler *handler =
 336                         ext2_xattr_handler(entry->e_name_index);
 337
 338                 if (handler && (!handler->list || handler->list(dentry))) {
 339                         const char *prefix = handler->prefix ?: handler->name;
 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         down_write(&EXT2_I(inode)->xattr_sem);
 440         if (EXT2_I(inode)->i_file_acl) {
 441                 /* The inode already has an extended attribute block. */
 442                 bh = sb_bread(sb, EXT2_I(inode)->i_file_acl);
 443                 error = -EIO;
 444                 if (!bh)
 445                         goto cleanup;
 446                 ea_bdebug(bh, "b_count=%d, refcount=%d",
 447                         atomic_read(&(bh->b_count)),
 448                         le32_to_cpu(HDR(bh)->h_refcount));
 449                 header = HDR(bh);
 450                 end = bh->b_data + bh->b_size;
 451                 if (!ext2_xattr_header_valid(header)) {
 452 bad_block:
 453                         ext2_error(sb, "ext2_xattr_set",
 454                                 "inode %ld: bad block %d", inode->i_ino,
 455                                    EXT2_I(inode)->i_file_acl);
 456                         error = -EIO;
 457                         goto cleanup;
 458                 }
 459                 /*
 460                  * Find the named attribute. If not found, 'here' will point
 461                  * to entry where the new attribute should be inserted to
 462                  * maintain sorting.
 463                  */
 464                 last = FIRST_ENTRY(bh);
 465                 while (!IS_LAST_ENTRY(last)) {
 466                         if (!ext2_xattr_entry_valid(last, end, sb->s_blocksize))
 467                                 goto bad_block;
 468                         if (last->e_value_size) {
 469                                 size_t offs = le16_to_cpu(last->e_value_offs);
 470                                 if (offs < min_offs)
 471                                         min_offs = offs;
 472                         }
 473                         if (not_found > 0) {
 474                                 not_found = ext2_xattr_cmp_entry(name_index,
 475                                                                  name_len,
 476                                                                  name, last);
 477                                 if (not_found <= 0)
 478                                         here = last;
 479                         }
 480                         last = EXT2_XATTR_NEXT(last);
 481                 }
 482                 if (not_found > 0)
 483                         here = last;
 484
 485                 /* Check whether we have enough space left. */
 486                 free = min_offs - ((char*)last - (char*)header) - sizeof(__u32);
 487         } else {
 488                 /* We will use a new extended attribute block. */
 489                 free = sb->s_blocksize -
 490                         sizeof(struct ext2_xattr_header) - sizeof(__u32);
 491         }
 492
 493         if (not_found) {
 494                 /* Request to remove a nonexistent attribute? */
 495                 error = -ENODATA;
 496                 if (flags & XATTR_REPLACE)
 497                         goto cleanup;
 498                 error = 0;
 499                 if (value == NULL)
 500                         goto cleanup;
 501         } else {
 502                 /* Request to create an existing attribute? */
 503                 error = -EEXIST;
 504                 if (flags & XATTR_CREATE)
 505                         goto cleanup;
 506                 free += EXT2_XATTR_SIZE(le32_to_cpu(here->e_value_size));
 507                 free += EXT2_XATTR_LEN(name_len);
 508         }
 509         error = -ENOSPC;
 510         if (free < EXT2_XATTR_LEN(name_len) + EXT2_XATTR_SIZE(value_len))
 511                 goto cleanup;
 512
 513         /* Here we know that we can set the new attribute. */
 514
 515         if (header) {
 516                 /* assert(header == HDR(bh)); */
 517                 lock_buffer(bh);
 518                 if (header->h_refcount == cpu_to_le32(1)) {
 519                         __u32 hash = le32_to_cpu(header->h_hash);
 520
 521                         ea_bdebug(bh, "modifying in-place");
 522                         /*
 523                          * This must happen under buffer lock for
 524                          * ext2_xattr_set2() to reliably detect modified block
 525                          */
 526                         mb_cache_entry_delete(EA_BLOCK_CACHE(inode), hash,
 527                                               bh->b_blocknr);
 528
 529                         /* keep the buffer locked while modifying it. */
 530                 } else {
 531                         int offset;
 532
 533                         unlock_buffer(bh);
 534                         ea_bdebug(bh, "cloning");
 535                         header = kmemdup(HDR(bh), bh->b_size, GFP_KERNEL);
 536                         error = -ENOMEM;
 537                         if (header == NULL)
 538                                 goto cleanup;
 539                         header->h_refcount = cpu_to_le32(1);
 540
 541                         offset = (char *)here - bh->b_data;
 542                         here = ENTRY((char *)header + offset);
 543                         offset = (char *)last - bh->b_data;
 544                         last = ENTRY((char *)header + offset);
 545                 }
 546         } else {
 547                 /* Allocate a buffer where we construct the new block. */
 548                 header = kzalloc(sb->s_blocksize, GFP_KERNEL);
 549                 error = -ENOMEM;
 550                 if (header == NULL)
 551                         goto cleanup;
 552                 end = (char *)header + sb->s_blocksize;
 553                 header->h_magic = cpu_to_le32(EXT2_XATTR_MAGIC);
 554                 header->h_blocks = header->h_refcount = cpu_to_le32(1);
 555                 last = here = ENTRY(header+1);
 556         }
 557
 558         /* Iff we are modifying the block in-place, bh is locked here. */
 559
 560         if (not_found) {
 561                 /* Insert the new name. */
 562                 size_t size = EXT2_XATTR_LEN(name_len);
 563                 size_t rest = (char *)last - (char *)here;
 564                 memmove((char *)here + size, here, rest);
 565                 memset(here, 0, size);
 566                 here->e_name_index = name_index;
 567                 here->e_name_len = name_len;
 568                 memcpy(here->e_name, name, name_len);
 569         } else {
 570                 if (here->e_value_size) {
 571                         char *first_val = (char *)header + min_offs;
 572                         size_t offs = le16_to_cpu(here->e_value_offs);
 573                         char *val = (char *)header + offs;
 574                         size_t size = EXT2_XATTR_SIZE(
 575                                 le32_to_cpu(here->e_value_size));
 576
 577                         if (size == EXT2_XATTR_SIZE(value_len)) {
 578                                 /* The old and the new value have the same
 579                                    size. Just replace. */
 580                                 here->e_value_size = cpu_to_le32(value_len);
 581                                 memset(val + size - EXT2_XATTR_PAD, 0,
 582                                        EXT2_XATTR_PAD); /* Clear pad bytes. */
 583                                 memcpy(val, value, value_len);
 584                                 goto skip_replace;
 585                         }
 586
 587                         /* Remove the old value. */
 588                         memmove(first_val + size, first_val, val - first_val);
 589                         memset(first_val, 0, size);
 590                         here->e_value_offs = 0;
 591                         min_offs += size;
 592
 593                         /* Adjust all value offsets. */
 594                         last = ENTRY(header+1);
 595                         while (!IS_LAST_ENTRY(last)) {
 596                                 size_t o = le16_to_cpu(last->e_value_offs);
 597                                 if (o < offs)
 598                                         last->e_value_offs =
 599                                                 cpu_to_le16(o + size);
 600                                 last = EXT2_XATTR_NEXT(last);
 601                         }
 602                 }
 603                 if (value == NULL) {
 604                         /* Remove the old name. */
 605                         size_t size = EXT2_XATTR_LEN(name_len);
 606                         last = ENTRY((char *)last - size);
 607                         memmove(here, (char*)here + size,
 608                                 (char*)last - (char*)here);
 609                         memset(last, 0, size);
 610                 }
 611         }
 612
 613         if (value != NULL) {
 614                 /* Insert the new value. */
 615                 here->e_value_size = cpu_to_le32(value_len);
 616                 if (value_len) {
 617                         size_t size = EXT2_XATTR_SIZE(value_len);
 618                         char *val = (char *)header + min_offs - size;
 619                         here->e_value_offs =
 620                                 cpu_to_le16((char *)val - (char *)header);
 621                         memset(val + size - EXT2_XATTR_PAD, 0,
 622                                EXT2_XATTR_PAD); /* Clear the pad bytes. */
 623                         memcpy(val, value, value_len);
 624                 }
 625         }
 626
 627 skip_replace:
 628         if (IS_LAST_ENTRY(ENTRY(header+1))) {
 629                 /* This block is now empty. */
 630                 if (bh && header == HDR(bh))
 631                         unlock_buffer(bh);  /* we were modifying in-place. */
 632                 error = ext2_xattr_set2(inode, bh, NULL);
 633         } else {
 634                 ext2_xattr_rehash(header, here);
 635                 if (bh && header == HDR(bh))
 636                         unlock_buffer(bh);  /* we were modifying in-place. */
 637                 error = ext2_xattr_set2(inode, bh, header);
 638         }
 639
 640 cleanup:
 641         if (!(bh && header == HDR(bh)))
 642                 kfree(header);
 643         brelse(bh);
 644         up_write(&EXT2_I(inode)->xattr_sem);
 645
 646         return error;
 647 }
 648
 649 /*
 650  * Second half of ext2_xattr_set(): Update the file system.
 651  */
 652 static int
 653 ext2_xattr_set2(struct inode *inode, struct buffer_head *old_bh,
 654                 struct ext2_xattr_header *header)
 655 {
 656         struct super_block *sb = inode->i_sb;
 657         struct buffer_head *new_bh = NULL;
 658         int error;
 659         struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
 660
 661         if (header) {
 662                 new_bh = ext2_xattr_cache_find(inode, header);
 663                 if (new_bh) {
 664                         /* We found an identical block in the cache. */
 665                         if (new_bh == old_bh) {
 666                                 ea_bdebug(new_bh, "keeping this block");
 667                         } else {
 668                                 /* The old block is released after updating
 669                                    the inode.  */
 670                                 ea_bdebug(new_bh, "reusing block");
 671
 672                                 error = dquot_alloc_block(inode, 1);
 673                                 if (error) {
 674                                         unlock_buffer(new_bh);
 675                                         goto cleanup;
 676                                 }
 677                                 le32_add_cpu(&HDR(new_bh)->h_refcount, 1);
 678                                 ea_bdebug(new_bh, "refcount now=%d",
 679                                         le32_to_cpu(HDR(new_bh)->h_refcount));
 680                         }
 681                         unlock_buffer(new_bh);
 682                 } else if (old_bh && header == HDR(old_bh)) {
 683                         /* Keep this block. No need to lock the block as we
 684                            don't need to change the reference count. */
 685                         new_bh = old_bh;
 686                         get_bh(new_bh);
 687                         ext2_xattr_cache_insert(ea_block_cache, new_bh);
 688                 } else {
 689                         /* We need to allocate a new block */
 690                         ext2_fsblk_t goal = ext2_group_first_block_no(sb,
 691                                                 EXT2_I(inode)->i_block_group);
 692                         int block = ext2_new_block(inode, goal, &error);
 693                         if (error)
 694                                 goto cleanup;
 695                         ea_idebug(inode, "creating block %d", block);
 696
 697                         new_bh = sb_getblk(sb, block);
 698                         if (unlikely(!new_bh)) {
 699                                 ext2_free_blocks(inode, block, 1);
 700                                 mark_inode_dirty(inode);
 701                                 error = -ENOMEM;
 702                                 goto cleanup;
 703                         }
 704                         lock_buffer(new_bh);
 705                         memcpy(new_bh->b_data, header, new_bh->b_size);
 706                         set_buffer_uptodate(new_bh);
 707                         unlock_buffer(new_bh);
 708                         ext2_xattr_cache_insert(ea_block_cache, new_bh);
 709
 710                         ext2_xattr_update_super_block(sb);
 711                 }
 712                 mark_buffer_dirty(new_bh);
 713                 if (IS_SYNC(inode)) {
 714                         sync_dirty_buffer(new_bh);
 715                         error = -EIO;
 716                         if (buffer_req(new_bh) && !buffer_uptodate(new_bh))
 717                                 goto cleanup;
 718                 }
 719         }
 720
 721         /* Update the inode. */
 722         EXT2_I(inode)->i_file_acl = new_bh ? new_bh->b_blocknr : 0;
 723         inode->i_ctime = current_time(inode);
 724         if (IS_SYNC(inode)) {
 725                 error = sync_inode_metadata(inode, 1);
 726                 /* In case sync failed due to ENOSPC the inode was actually
 727                  * written (only some dirty data were not) so we just proceed
 728                  * as if nothing happened and cleanup the unused block */
 729                 if (error && error != -ENOSPC) {
 730                         if (new_bh && new_bh != old_bh) {
 731                                 dquot_free_block_nodirty(inode, 1);
 732                                 mark_inode_dirty(inode);
 733                         }
 734                         goto cleanup;
 735                 }
 736         } else
 737                 mark_inode_dirty(inode);
 738
 739         error = 0;
 740         if (old_bh && old_bh != new_bh) {
 741                 /*
 742                  * If there was an old block and we are no longer using it,
 743                  * release the old block.
 744                  */
 745                 lock_buffer(old_bh);
 746                 if (HDR(old_bh)->h_refcount == cpu_to_le32(1)) {
 747                         __u32 hash = le32_to_cpu(HDR(old_bh)->h_hash);
 748
 749                         /*
 750                          * This must happen under buffer lock for
 751                          * ext2_xattr_set2() to reliably detect freed block
 752                          */
 753                         mb_cache_entry_delete(ea_block_cache, hash,
 754                                               old_bh->b_blocknr);
 755                         /* Free the old block. */
 756                         ea_bdebug(old_bh, "freeing");
 757                         ext2_free_blocks(inode, old_bh->b_blocknr, 1);
 758                         mark_inode_dirty(inode);
 759                         /* We let our caller release old_bh, so we
 760                          * need to duplicate the buffer before. */
 761                         get_bh(old_bh);
 762                         bforget(old_bh);
 763                 } else {
 764                         /* Decrement the refcount only. */
 765                         le32_add_cpu(&HDR(old_bh)->h_refcount, -1);
 766                         dquot_free_block_nodirty(inode, 1);
 767                         mark_inode_dirty(inode);
 768                         mark_buffer_dirty(old_bh);
 769                         ea_bdebug(old_bh, "refcount now=%d",
 770                                 le32_to_cpu(HDR(old_bh)->h_refcount));
 771                 }
 772                 unlock_buffer(old_bh);
 773         }
 774
 775 cleanup:
 776         brelse(new_bh);
 777
 778         return error;
 779 }
 780
 781 /*
 782  * ext2_xattr_delete_inode()
 783  *
 784  * Free extended attribute resources associated with this inode. This
 785  * is called immediately before an inode is freed.
 786  */
 787 void
 788 ext2_xattr_delete_inode(struct inode *inode)
 789 {
 790         struct buffer_head *bh = NULL;
 791         struct ext2_sb_info *sbi = EXT2_SB(inode->i_sb);
 792
 793         down_write(&EXT2_I(inode)->xattr_sem);
 794         if (!EXT2_I(inode)->i_file_acl)
 795                 goto cleanup;
 796
 797         if (!ext2_data_block_valid(sbi, EXT2_I(inode)->i_file_acl, 1)) {
 798                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 799                         "inode %ld: xattr block %d is out of data blocks range",
 800                         inode->i_ino, EXT2_I(inode)->i_file_acl);
 801                 goto cleanup;
 802         }
 803
 804         bh = sb_bread(inode->i_sb, EXT2_I(inode)->i_file_acl);
 805         if (!bh) {
 806                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 807                         "inode %ld: block %d read error", inode->i_ino,
 808                         EXT2_I(inode)->i_file_acl);
 809                 goto cleanup;
 810         }
 811         ea_bdebug(bh, "b_count=%d", atomic_read(&(bh->b_count)));
 812         if (!ext2_xattr_header_valid(HDR(bh))) {
 813                 ext2_error(inode->i_sb, "ext2_xattr_delete_inode",
 814                         "inode %ld: bad block %d", inode->i_ino,
 815                         EXT2_I(inode)->i_file_acl);
 816                 goto cleanup;
 817         }
 818         lock_buffer(bh);
 819         if (HDR(bh)->h_refcount == cpu_to_le32(1)) {
 820                 __u32 hash = le32_to_cpu(HDR(bh)->h_hash);
 821
 822                 /*
 823                  * This must happen under buffer lock for ext2_xattr_set2() to
 824                  * reliably detect freed block
 825                  */
 826                 mb_cache_entry_delete(EA_BLOCK_CACHE(inode), hash,
 827                                       bh->b_blocknr);
 828                 ext2_free_blocks(inode, EXT2_I(inode)->i_file_acl, 1);
 829                 get_bh(bh);
 830                 bforget(bh);
 831                 unlock_buffer(bh);
 832         } else {
 833                 le32_add_cpu(&HDR(bh)->h_refcount, -1);
 834                 ea_bdebug(bh, "refcount now=%d",
 835                         le32_to_cpu(HDR(bh)->h_refcount));
 836                 unlock_buffer(bh);
 837                 mark_buffer_dirty(bh);
 838                 if (IS_SYNC(inode))
 839                         sync_dirty_buffer(bh);
 840                 dquot_free_block_nodirty(inode, 1);
 841         }
 842         EXT2_I(inode)->i_file_acl = 0;
 843
 844 cleanup:
 845         brelse(bh);
 846         up_write(&EXT2_I(inode)->xattr_sem);
 847 }
 848
 849 /*
 850  * ext2_xattr_cache_insert()
 851  *
 852  * Create a new entry in the extended attribute cache, and insert
 853  * it unless such an entry is already in the cache.
 854  *
 855  * Returns 0, or a negative error number on failure.
 856  */
 857 static int
 858 ext2_xattr_cache_insert(struct mb_cache *cache, struct buffer_head *bh)
 859 {
 860         __u32 hash = le32_to_cpu(HDR(bh)->h_hash);
 861         int error;
 862
 863         error = mb_cache_entry_create(cache, GFP_NOFS, hash, bh->b_blocknr,
 864                                       true);
 865         if (error) {
 866                 if (error == -EBUSY) {
 867                         ea_bdebug(bh, "already in cache (%d cache entries)",
 868                                 atomic_read(&ext2_xattr_cache->c_entry_count));
 869                         error = 0;
 870                 }
 871         } else
 872                 ea_bdebug(bh, "inserting [%x]", (int)hash);
 873         return error;
 874 }
 875
 876 /*
 877  * ext2_xattr_cmp()
 878  *
 879  * Compare two extended attribute blocks for equality.
 880  *
 881  * Returns 0 if the blocks are equal, 1 if they differ, and
 882  * a negative error number on errors.
 883  */
 884 static int
 885 ext2_xattr_cmp(struct ext2_xattr_header *header1,
 886                struct ext2_xattr_header *header2)
 887 {
 888         struct ext2_xattr_entry *entry1, *entry2;
 889
 890         entry1 = ENTRY(header1+1);
 891         entry2 = ENTRY(header2+1);
 892         while (!IS_LAST_ENTRY(entry1)) {
 893                 if (IS_LAST_ENTRY(entry2))
 894                         return 1;
 895                 if (entry1->e_hash != entry2->e_hash ||
 896                     entry1->e_name_index != entry2->e_name_index ||
 897                     entry1->e_name_len != entry2->e_name_len ||
 898                     entry1->e_value_size != entry2->e_value_size ||
 899                     memcmp(entry1->e_name, entry2->e_name, entry1->e_name_len))
 900                         return 1;
 901                 if (entry1->e_value_block != 0 || entry2->e_value_block != 0)
 902                         return -EIO;
 903                 if (memcmp((char *)header1 + le16_to_cpu(entry1->e_value_offs),
 904                            (char *)header2 + le16_to_cpu(entry2->e_value_offs),
 905                            le32_to_cpu(entry1->e_value_size)))
 906                         return 1;
 907
 908                 entry1 = EXT2_XATTR_NEXT(entry1);
 909                 entry2 = EXT2_XATTR_NEXT(entry2);
 910         }
 911         if (!IS_LAST_ENTRY(entry2))
 912                 return 1;
 913         return 0;
 914 }
 915
 916 /*
 917  * ext2_xattr_cache_find()
 918  *
 919  * Find an identical extended attribute block.
 920  *
 921  * Returns a locked buffer head to the block found, or NULL if such
 922  * a block was not found or an error occurred.
 923  */
 924 static struct buffer_head *
 925 ext2_xattr_cache_find(struct inode *inode, struct ext2_xattr_header *header)
 926 {
 927         __u32 hash = le32_to_cpu(header->h_hash);
 928         struct mb_cache_entry *ce;
 929         struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
 930
 931         if (!header->h_hash)
 932                 return NULL;  /* never share */
 933         ea_idebug(inode, "looking for cached blocks [%x]", (int)hash);
 934 again:
 935         ce = mb_cache_entry_find_first(ea_block_cache, hash);
 936         while (ce) {
 937                 struct buffer_head *bh;
 938
 939                 bh = sb_bread(inode->i_sb, ce->e_value);
 940                 if (!bh) {
 941                         ext2_error(inode->i_sb, "ext2_xattr_cache_find",
 942                                 "inode %ld: block %ld read error",
 943                                 inode->i_ino, (unsigned long) ce->e_value);
 944                 } else {
 945                         lock_buffer(bh);
 946                         /*
 947                          * We have to be careful about races with freeing or
 948                          * rehashing of xattr block. Once we hold buffer lock
 949                          * xattr block's state is stable so we can check
 950                          * whether the block got freed / rehashed or not.
 951                          * Since we unhash mbcache entry under buffer lock when
 952                          * freeing / rehashing xattr block, checking whether
 953                          * entry is still hashed is reliable.
 954                          */
 955                         if (hlist_bl_unhashed(&ce->e_hash_list)) {
 956                                 mb_cache_entry_put(ea_block_cache, ce);
 957                                 unlock_buffer(bh);
 958                                 brelse(bh);
 959                                 goto again;
 960                         } else if (le32_to_cpu(HDR(bh)->h_refcount) >
 961                                    EXT2_XATTR_REFCOUNT_MAX) {
 962                                 ea_idebug(inode, "block %ld refcount %d>%d",
 963                                           (unsigned long) ce->e_value,
 964                                           le32_to_cpu(HDR(bh)->h_refcount),
 965                                           EXT2_XATTR_REFCOUNT_MAX);
 966                         } else if (!ext2_xattr_cmp(header, HDR(bh))) {
 967                                 ea_bdebug(bh, "b_count=%d",
 968                                           atomic_read(&(bh->b_count)));
 969                                 mb_cache_entry_touch(ea_block_cache, ce);
 970                                 mb_cache_entry_put(ea_block_cache, ce);
 971                                 return bh;
 972                         }
 973                         unlock_buffer(bh);
 974                         brelse(bh);
 975                 }
 976                 ce = mb_cache_entry_find_next(ea_block_cache, ce);
 977         }
 978         return NULL;
 979 }
 980
 981 #define NAME_HASH_SHIFT 5
 982 #define VALUE_HASH_SHIFT 16
 983
 984 /*
 985  * ext2_xattr_hash_entry()
 986  *
 987  * Compute the hash of an extended attribute.
 988  */
 989 static inline void ext2_xattr_hash_entry(struct ext2_xattr_header *header,
 990                                          struct ext2_xattr_entry *entry)
 991 {
 992         __u32 hash = 0;
 993         char *name = entry->e_name;
 994         int n;
 995
 996         for (n=0; n < entry->e_name_len; n++) {
 997                 hash = (hash << NAME_HASH_SHIFT) ^
 998                        (hash >> (8*sizeof(hash) - NAME_HASH_SHIFT)) ^
 999                        *name++;
1000         }
1001
1002         if (entry->e_value_block == 0 && entry->e_value_size != 0) {
1003                 __le32 *value = (__le32 *)((char *)header +
1004                         le16_to_cpu(entry->e_value_offs));
1005                 for (n = (le32_to_cpu(entry->e_value_size) +
1006                      EXT2_XATTR_ROUND) >> EXT2_XATTR_PAD_BITS; n; n--) {
1007                         hash = (hash << VALUE_HASH_SHIFT) ^
1008                                (hash >> (8*sizeof(hash) - VALUE_HASH_SHIFT)) ^
1009                                le32_to_cpu(*value++);
1010                 }
1011         }
1012         entry->e_hash = cpu_to_le32(hash);
1013 }
1014
1015 #undef NAME_HASH_SHIFT
1016 #undef VALUE_HASH_SHIFT
1017
1018 #define BLOCK_HASH_SHIFT 16
1019
1020 /*
1021  * ext2_xattr_rehash()
1022  *
1023  * Re-compute the extended attribute hash value after an entry has changed.
1024  */
1025 static void ext2_xattr_rehash(struct ext2_xattr_header *header,
1026                               struct ext2_xattr_entry *entry)
1027 {
1028         struct ext2_xattr_entry *here;
1029         __u32 hash = 0;
1030
1031         ext2_xattr_hash_entry(header, entry);
1032         here = ENTRY(header+1);
1033         while (!IS_LAST_ENTRY(here)) {
1034                 if (!here->e_hash) {
1035                         /* Block is not shared if an entry's hash value == 0 */
1036                         hash = 0;
1037                         break;
1038                 }
1039                 hash = (hash << BLOCK_HASH_SHIFT) ^
1040                        (hash >> (8*sizeof(hash) - BLOCK_HASH_SHIFT)) ^
1041                        le32_to_cpu(here->e_hash);
1042                 here = EXT2_XATTR_NEXT(here);
1043         }
1044         header->h_hash = cpu_to_le32(hash);
1045 }
1046
1047 #undef BLOCK_HASH_SHIFT
1048
1049 #define HASH_BUCKET_BITS 10
1050
1051 struct mb_cache *ext2_xattr_create_cache(void)
1052 {
1053         return mb_cache_create(HASH_BUCKET_BITS);
1054 }
1055
1056 void ext2_xattr_destroy_cache(struct mb_cache *cache)
1057 {
1058         if (cache)
1059                 mb_cache_destroy(cache);
1060 }