ext4_add_block_bitmap_validation.patch

   1 ext4: add block bitmap validation
   2
   3 From: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
   4
   5 When a new block bitmap is read from disk in read_block_bitmap()
   6 there are a few bits that should ALWAYS be set.  In particular,
   7 the blocks given corresponding to block bitmap, inode bitmap and inode tables.
   8 Validate the block bitmap against these blocks.
   9
  10 Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
  11 ---
  12
  13  fs/ext4/balloc.c |   99 ++++++++++++++++++++++++++++++++++++++++++++----------
  14  1 files changed, 81 insertions(+), 18 deletions(-)
  15
  16
  17 diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
  18 index ff3428e..a9140ea 100644
  19 --- a/fs/ext4/balloc.c
  20 +++ b/fs/ext4/balloc.c
  21 @@ -189,13 +189,65 @@ struct ext4_group_desc * ext4_get_group_desc(struct super_block * sb,
  22         return desc;
  23  }
  24
  25 +static int ext4_valid_block_bitmap(struct super_block *sb,
  26 +                                       struct ext4_group_desc *desc,
  27 +                                       unsigned int block_group,
  28 +                                       struct buffer_head *bh)
  29 +{
  30 +       ext4_grpblk_t offset;
  31 +       ext4_grpblk_t next_zero_bit;
  32 +       ext4_fsblk_t bitmap_blk;
  33 +       ext4_fsblk_t group_first_block;
  34 +
  35 +       if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG)) {
  36 +               /* with FLEX_BG, the inode/block bitmaps and itable
  37 +                * blocks may not be in the group at all
  38 +                * so the bitmap validation will be skipped for those groups
  39 +                * or it has to also read the block group where the bitmaps
  40 +                * are located to verify they are set.
  41 +                */
  42 +               return 1;
  43 +       }
  44 +       group_first_block = ext4_group_first_block_no(sb, block_group);
  45 +
  46 +       /* check whether block bitmap block number is set */
  47 +       bitmap_blk = ext4_block_bitmap(sb, desc);
  48 +       offset = bitmap_blk - group_first_block;
  49 +       if (!ext4_test_bit(offset, bh->b_data))
  50 +               /* bad block bitmap */
  51 +               goto err_out;
  52 +
  53 +       /* check whether the inode bitmap block number is set */
  54 +       bitmap_blk = ext4_inode_bitmap(sb, desc);
  55 +       offset = bitmap_blk - group_first_block;
  56 +       if (!ext4_test_bit(offset, bh->b_data))
  57 +               /* bad block bitmap */
  58 +               goto err_out;
  59 +
  60 +       /* check whether the inode table block number is set */
  61 +       bitmap_blk = ext4_inode_table(sb, desc);
  62 +       offset = bitmap_blk - group_first_block;
  63 +       next_zero_bit = ext4_find_next_zero_bit(bh->b_data,
  64 +                               offset + EXT4_SB(sb)->s_itb_per_group,
  65 +                               offset);
  66 +       if (next_zero_bit >= offset + EXT4_SB(sb)->s_itb_per_group)
  67 +               /* good bitmap for inode tables */
  68 +               return 1;
  69 +
  70 +err_out:
  71 +       ext4_error(sb, __FUNCTION__,
  72 +                       "Invalid block bitmap - "
  73 +                       "block_group = %d, block = %llu",
  74 +                       block_group, bitmap_blk);
  75 +       return 0;
  76 +}
  77  /**
  78   * read_block_bitmap()
  79   * @sb:                        super block
  80   * @block_group:       given block group
  81   *
  82 - * Read the bitmap for a given block_group, reading into the specified
  83 - * slot in the superblock's bitmap cache.
  84 + * Read the bitmap for a given block_group,and validate the
  85 + * bits for block/inode/inode tables are set in the bitmaps
  86   *
  87   * Return buffer_head on success or NULL in case of failure.
  88   */
  89 @@ -210,25 +262,36 @@ read_block_bitmap(struct super_block *sb, ext4_group_t block_group)
  90         if (!desc)
  91                 return NULL;
  92         bitmap_blk = ext4_block_bitmap(sb, desc);
  93 +       bh = sb_getblk(sb, bitmap_blk);
  94 +       if (unlikely(!bh)) {
  95 +               ext4_error(sb, __FUNCTION__,
  96 +                           "Cannot read block bitmap - "
  97 +                           "block_group = %d, block_bitmap = %llu",
  98 +                           (int)block_group, (unsigned long long)bitmap_blk);
  99 +               return NULL;
 100 +       }
 101 +       if (bh_uptodate_or_lock(bh))
 102 +               return bh;
 103 +
 104         if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
 105 -               bh = sb_getblk(sb, bitmap_blk);
 106 -               if (!buffer_uptodate(bh)) {
 107 -                       lock_buffer(bh);
 108 -                       if (!buffer_uptodate(bh)) {
 109 -                               ext4_init_block_bitmap(sb, bh, block_group,
 110 -                                                      desc);
 111 -                               set_buffer_uptodate(bh);
 112 -                       }
 113 -                       unlock_buffer(bh);
 114 -               }
 115 -       } else {
 116 -               bh = sb_bread(sb, bitmap_blk);
 117 +               ext4_init_block_bitmap(sb, bh, block_group, desc);
 118 +               set_buffer_uptodate(bh);
 119 +               unlock_buffer(bh);
 120 +               return bh;
 121         }
 122 -       if (!bh)
 123 -               ext4_error (sb, __FUNCTION__,
 124 +       if (bh_submit_read(bh) < 0) {
 125 +               brelse(bh);
 126 +               ext4_error(sb, __FUNCTION__,
 127                             "Cannot read block bitmap - "
 128 -                           "block_group = %lu, block_bitmap = %llu",
 129 -                           block_group, bitmap_blk);
 130 +                           "block_group = %d, block_bitmap = %llu",
 131 +                           (int)block_group, (unsigned long long)bitmap_blk);
 132 +               return NULL;
 133 +       }
 134 +       if (!ext4_valid_block_bitmap(sb, desc, block_group, bh)) {
 135 +               brelse(bh);
 136 +               return NULL;
 137 +       }
 138 +
 139         return bh;
 140  }
 141  /*