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ext2: 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>
Cc: <linux-ext4@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Aneesh Kumar K.V 2008-02-06 01:40:08 -08:00 committed by Linus Torvalds
parent 445a1d3e24
commit 01584fa645
1 changed files with 72 additions and 9 deletions
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81
fs/ext2/balloc.c
View File

@ -69,9 +69,53 @@ struct ext2_group_desc * ext2_get_group_desc(struct super_block * sb,
return desc + offset;
}
static int ext2_valid_block_bitmap(struct super_block *sb,
struct ext2_group_desc *desc,
unsigned int block_group,
struct buffer_head *bh)
{
ext2_grpblk_t offset;
ext2_grpblk_t next_zero_bit;
ext2_fsblk_t bitmap_blk;
ext2_fsblk_t group_first_block;
group_first_block = ext2_group_first_block_no(sb, block_group);
/* check whether block bitmap block number is set */
bitmap_blk = le32_to_cpu(desc->bg_block_bitmap);
offset = bitmap_blk - group_first_block;
if (!ext2_test_bit(offset, bh->b_data))
/* bad block bitmap */
goto err_out;
/* check whether the inode bitmap block number is set */
bitmap_blk = le32_to_cpu(desc->bg_inode_bitmap);
offset = bitmap_blk - group_first_block;
if (!ext2_test_bit(offset, bh->b_data))
/* bad block bitmap */
goto err_out;
/* check whether the inode table block number is set */
bitmap_blk = le32_to_cpu(desc->bg_inode_table);
offset = bitmap_blk - group_first_block;
next_zero_bit = ext2_find_next_zero_bit(bh->b_data,
offset + EXT2_SB(sb)->s_itb_per_group,
offset);
if (next_zero_bit >= offset + EXT2_SB(sb)->s_itb_per_group)
/* good bitmap for inode tables */
return 1;
err_out:
ext2_error(sb, __FUNCTION__,
"Invalid block bitmap - "
"block_group = %d, block = %lu",
block_group, bitmap_blk);
return 0;
}
/*
* 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.
*/
@ -80,17 +124,36 @@ read_block_bitmap(struct super_block *sb, unsigned int block_group)
{
struct ext2_group_desc * desc;
struct buffer_head * bh = NULL;
desc = ext2_get_group_desc (sb, block_group, NULL);
ext2_fsblk_t bitmap_blk;
desc = ext2_get_group_desc(sb, block_group, NULL);
if (!desc)
goto error_out;
bh = sb_bread(sb, le32_to_cpu(desc->bg_block_bitmap));
if (!bh)
ext2_error (sb, "read_block_bitmap",
return NULL;
bitmap_blk = le32_to_cpu(desc->bg_block_bitmap);
bh = sb_getblk(sb, bitmap_blk);
if (unlikely(!bh)) {
ext2_error(sb, __FUNCTION__,
"Cannot read block bitmap - "
"block_group = %d, block_bitmap = %u",
block_group, le32_to_cpu(desc->bg_block_bitmap));
error_out:
return NULL;
}
if (likely(bh_uptodate_or_lock(bh)))
return bh;
if (bh_submit_read(bh) < 0) {
brelse(bh);
ext2_error(sb, __FUNCTION__,
"Cannot read block bitmap - "
"block_group = %d, block_bitmap = %u",
block_group, le32_to_cpu(desc->bg_block_bitmap));
return NULL;
}
if (!ext2_valid_block_bitmap(sb, desc, block_group, bh)) {
brelse(bh);
return NULL;
}
return bh;
}