Re: [Bugme-new] [Bug 11266] New: unable to handle kernel paging request in ext2_free_blocks

Aneesh Kumar K.V
2008-08-18T16:51:46Z

On Mon, Aug 18, 2008 at 04:58:41PM +0200, Jan Kara wrote:
>
> From 06953717138efe3ad535e78343beb7204ac0d274 Mon Sep 17 00:00:00 2001
> From: Jan Kara <jack@suse.cz>
> Date: Mon, 18 Aug 2008 16:45:11 +0200
> Subject: [PATCH] ext2: Check for corrupted group descriptor before using data in it
>
> We have to check whether a group descriptor isn't corrupted in
> read_block_bitmap(). Otherwise ext2_valid_block_bitmap() will try
> to access bits outside of bitmap and Oops happens.
>
> CC: Vegard Nossum <vegard.nossum@gmail.com>
> CC: Sami Liedes <sliedes@cc.hut.fi>
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
> fs/ext2/balloc.c | 29 +++++++++++++++++++++++++++++
> 1 files changed, 29 insertions(+), 0 deletions(-)
>
> diff --git a/fs/ext2/balloc.c b/fs/ext2/balloc.c
> index 10bb02c..9104712 100644
> --- a/fs/ext2/balloc.c
> +++ b/fs/ext2/balloc.c
> @@ -113,6 +113,17 @@ err_out:
> return 0;
> }
>
> +static int ext2_block_in_group(struct super_block *sb,
> + unsigned int block_group, ext2_fsblk_t block)
> +{
> + if (block < ext2_group_first_block_no(sb, block_group))
> + return 0;
> + if (block >= ext2_group_first_block_no(sb, block_group) +
> + EXT2_BLOCKS_PER_GROUP(sb))
> + return 0;
> + return 1;
> +}
> +
> /*
> * Read the bitmap for a given block_group,and validate the
> * bits for block/inode/inode tables are set in the bitmaps
> @@ -129,6 +140,24 @@ read_block_bitmap(struct super_block *sb, unsigned int block_group)
> desc = ext2_get_group_desc(sb, block_group, NULL);
> if (!desc)
> return NULL;
> + if (!ext2_block_in_group(sb, block_group,
> + le32_to_cpu(desc->bg_block_bitmap)) ||
> + !ext2_block_in_group(sb, block_group,
> + le32_to_cpu(desc->bg_inode_bitmap)) ||
> + !ext2_block_in_group(sb, block_group,
> + le32_to_cpu(desc->bg_inode_table)) ||
> + !ext2_block_in_group(sb, block_group,
> + le32_to_cpu(desc->bg_inode_table) +
> + EXT2_SB(sb)->s_itb_per_group - 1)) {
> + ext2_error(sb, __func__, "Corrupted group descriptor - "
> + "block_group = %u, block_bitmap = %u, "
> + "inode_bitmap = %u, inode_table = %u",
> + block_group,
> + le32_to_cpu(desc->bg_block_bitmap),
> + le32_to_cpu(desc->bg_inode_bitmap),
> + le32_to_cpu(desc->bg_inode_table));
> + return NULL;
> + }
> bitmap_blk = le32_to_cpu(desc->bg_block_bitmap);
> bh = sb_getblk(sb, bitmap_blk);
> if (unlikely(!bh)) {

Do we need to do this validation every time we do a read_block_bitmap ?
I guess we need to move the validation where we read the desc blocks
from the disk.

-aneesh