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ext4: add block bitmap validation 

When a new block bitmap is read from disk in read_block_bitmap()
there are a few bits that should ALWAYS be set.  In particular,
the blocks given corresponding to block bitmap, inode bitmap and inode tables.
Validate the block bitmap against these blocks.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
This commit is contained in:
Aneesh Kumar K.V 2008-01-28 23:58:27 -05:00 committed by Theodore Ts'o
parent 389d1b083c
commit abcb2947c9
1 changed files with 83 additions and 20 deletions
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103
fs/ext4/balloc.c
View File

@ -189,13 +189,65 @@ struct ext4_group_desc * ext4_get_group_desc(struct super_block * sb,
return desc;
}
static int ext4_valid_block_bitmap(struct super_block *sb,
struct ext4_group_desc *desc,
unsigned int block_group,
struct buffer_head *bh)
{
ext4_grpblk_t offset;
ext4_grpblk_t next_zero_bit;
ext4_fsblk_t bitmap_blk;
ext4_fsblk_t group_first_block;
if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG)) {
/* with FLEX_BG, the inode/block bitmaps and itable
* blocks may not be in the group at all
* so the bitmap validation will be skipped for those groups
* or it has to also read the block group where the bitmaps
* are located to verify they are set.
*/
return 1;
}
group_first_block = ext4_group_first_block_no(sb, block_group);
/* check whether block bitmap block number is set */
bitmap_blk = ext4_block_bitmap(sb, desc);
offset = bitmap_blk - group_first_block;
if (!ext4_test_bit(offset, bh->b_data))
/* bad block bitmap */
goto err_out;
/* check whether the inode bitmap block number is set */
bitmap_blk = ext4_inode_bitmap(sb, desc);
offset = bitmap_blk - group_first_block;
if (!ext4_test_bit(offset, bh->b_data))
/* bad block bitmap */
goto err_out;
/* check whether the inode table block number is set */
bitmap_blk = ext4_inode_table(sb, desc);
offset = bitmap_blk - group_first_block;
next_zero_bit = ext4_find_next_zero_bit(bh->b_data,
offset + EXT4_SB(sb)->s_itb_per_group,
offset);
if (next_zero_bit >= offset + EXT4_SB(sb)->s_itb_per_group)
/* good bitmap for inode tables */
return 1;
err_out:
ext4_error(sb, __FUNCTION__,
"Invalid block bitmap - "
"block_group = %d, block = %llu",
block_group, bitmap_blk);
return 0;
}
/**
* read_block_bitmap()
* @sb: super block
* @block_group: given block group
*
* Read the bitmap for a given block_group, reading into the specified
* slot in the superblock's bitmap cache.
* Read the bitmap for a given block_group,and validate the
* bits for block/inode/inode tables are set in the bitmaps
*
* Return buffer_head on success or NULL in case of failure.
*/
@ -210,25 +262,36 @@ read_block_bitmap(struct super_block *sb, ext4_group_t block_group)
if (!desc)
return NULL;
bitmap_blk = ext4_block_bitmap(sb, desc);
if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
bh = sb_getblk(sb, bitmap_blk);
if (!buffer_uptodate(bh)) {
lock_buffer(bh);
if (!buffer_uptodate(bh)) {
ext4_init_block_bitmap(sb, bh, block_group,
desc);
set_buffer_uptodate(bh);
}
unlock_buffer(bh);
}
} else {
bh = sb_bread(sb, bitmap_blk);
}
if (!bh)
ext4_error (sb, __FUNCTION__,
bh = sb_getblk(sb, bitmap_blk);
if (unlikely(!bh)) {
ext4_error(sb, __FUNCTION__,
"Cannot read block bitmap - "
"block_group = %lu, block_bitmap = %llu",
block_group, bitmap_blk);
"block_group = %d, block_bitmap = %llu",
(int)block_group, (unsigned long long)bitmap_blk);
return NULL;
}
if (bh_uptodate_or_lock(bh))
return bh;
if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
ext4_init_block_bitmap(sb, bh, block_group, desc);
set_buffer_uptodate(bh);
unlock_buffer(bh);
return bh;
}
if (bh_submit_read(bh) < 0) {
put_bh(bh);
ext4_error(sb, __FUNCTION__,
"Cannot read block bitmap - "
"block_group = %d, block_bitmap = %llu",
(int)block_group, (unsigned long long)bitmap_blk);
return NULL;
}
if (!ext4_valid_block_bitmap(sb, desc, block_group, bh)) {
put_bh(bh);
return NULL;
}
return bh;
}
/*