[Ocfs2-devel] [PATCH] ocfs2: validate bg_free_bits_count after update

[Sunil Mushran]

Acked-by: Sunil Mushran<sunil.mushran at oracle.com>


On 10/05/2010 03:53 PM, Srinivas Eeda wrote:
> This patch adds a safe check to ensure bg_free_bits_count doesn't exceed
> bg_bits in a group descriptor. This is to avoid on disk corruption that was
> seen recently.
>
> debugfs: group<52803072>
>         Group Chain: 179   Parent Inode: 11  Generation: 2959379682
>         CRC32: 00000000   ECC: 0000
>         ##   Block#            Total    Used     Free     Contig   Size
>         0    52803072          32256    4294965350   34202    18207    4032
>         ......
>
> Signed-off-by: Srinivas Eeda<srinivas.eeda at oracle.com>
> ---
>   fs/ocfs2/suballoc.c |   16 ++++++++++++++++
>   1 files changed, 16 insertions(+), 0 deletions(-)
>
> diff --git a/fs/ocfs2/suballoc.c b/fs/ocfs2/suballoc.c
> index 849c2f0..5fed60d 100644
> --- a/fs/ocfs2/suballoc.c
> +++ b/fs/ocfs2/suballoc.c
> @@ -1380,6 +1380,14 @@ static inline int ocfs2_block_group_set_bits(handle_t *handle,
>   	}
>
>   	le16_add_cpu(&bg->bg_free_bits_count, -num_bits);
> +	if (le16_to_cpu(bg->bg_free_bits_count)>  le16_to_cpu(bg->bg_bits)) {
> +		ocfs2_error(alloc_inode->i_sb, "Group descriptor # %llu has bit"
> +			    " count %u but claims %u are freed. num_bits %d",
> +			    (unsigned long long)le64_to_cpu(bg->bg_blkno),
> +			    le16_to_cpu(bg->bg_bits),
> +			    le16_to_cpu(bg->bg_free_bits_count), num_bits);
> +		return -EROFS;
> +	}
>   	while(num_bits--)
>   		ocfs2_set_bit(bit_off++, bitmap);
>
> @@ -2419,6 +2427,14 @@ static int ocfs2_block_group_clear_bits(handle_t *handle,
>   				(unsigned long *) undo_bg->bg_bitmap);
>   	}
>   	le16_add_cpu(&bg->bg_free_bits_count, num_bits);
> +	if (le16_to_cpu(bg->bg_free_bits_count)>  le16_to_cpu(bg->bg_bits)) {
> +		ocfs2_error(alloc_inode->i_sb, "Group descriptor # %llu has bit"
> +			    " count %u but claims %u are freed. num_bits %d",
> +			    (unsigned long long)le64_to_cpu(bg->bg_blkno),
> +			    le16_to_cpu(bg->bg_bits),
> +			    le16_to_cpu(bg->bg_free_bits_count), num_bits);
> +		return -EROFS;
> +	}
>
>   	if (undo_fn)
>   		jbd_unlock_bh_state(group_bh);
>