Re: [patch 2/2] Ocfs2/move_extents: NULL dereference moving extents

Jeff Liu
2013-04-04T08:21:15Z

On 04/04/2013 02:39 PM, Dan Carpenter wrote:
> We can't dereference "bg" before it has been assigned.
>
> GCC should have warned about this but "bg" was initialized to NULL.
> I've fixed that as well.
>
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
> Static analysis stuff. Compile tested only.
>
> diff --git a/fs/ocfs2/move_extents.c b/fs/ocfs2/move_extents.c
> index 995d1b4..f81d23c 100644
> --- a/fs/ocfs2/move_extents.c
> +++ b/fs/ocfs2/move_extents.c
> @@ -471,7 +471,7 @@ static int ocfs2_validate_and_adjust_move_goal(struct inode *inode,
> int ret, goal_bit = 0;
>
> struct buffer_head *gd_bh = NULL;
> - struct ocfs2_group_desc *bg = NULL;
> + struct ocfs2_group_desc *bg;
> struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
> int c_to_b = 1 << (osb->s_clustersize_bits -
> inode->i_sb->s_blocksize_bits);
> @@ -482,13 +482,6 @@ static int ocfs2_validate_and_adjust_move_goal(struct inode *inode,
> range->me_goal = ocfs2_block_to_cluster_start(inode->i_sb,
> range->me_goal);
> /*
> - * moving goal is not allowd to start with a group desc blok(#0 blk)
> - * let's compromise to the latter cluster.
> - */
> - if (range->me_goal = le64_to_cpu(bg->bg_blkno))
> - range->me_goal += c_to_b;
> -
> - /*
> * validate goal sits within global_bitmap, and return the victim
> * group desc
> */
> @@ -502,6 +495,13 @@ static int ocfs2_validate_and_adjust_move_goal(struct inode *inode,
> bg = (struct ocfs2_group_desc *)gd_bh->b_data;
>
> /*
> + * moving goal is not allowd to start with a group desc blok(#0 blk)
> + * let's compromise to the latter cluster.
> + */
> + if (range->me_goal = le64_to_cpu(bg->bg_blkno))
> + range->me_goal += c_to_b;
> +
> + /*
> * movement is not gonna cross two groups.
> */
> if ((le16_to_cpu(bg->bg_bits) - goal_bit) * osb->s_clustersize <

Reviewed-by: Jie Liu <jeff.liu@oracle.com>

This is an obvious bug, thanks you!

-Jeff
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