Re: [PATCH v2 2/2] ocfs2: validate dl_blkno and dl_fs_generation of dir index leaf blocks

[Heming Zhao]

On Sat, Sep 05, 2026 at 10:21:44PM +0800, Joseph Qi wrote:
> ocfs2_validate_dx_leaf() checks the checksum, the signature and the
> entry list counts, but it never checks dl_blkno or dl_fs_generation.
> The inode, extent block, xattr block, refcount block and dir index root
> validators all check the on-disk block number against bh->b_blocknr and
> the generation against the superblock, and both dir index leaf fields
> are documented as "Must match super block".
> 
> Without the checks, a stale dir index leaf block left on the device from
> a previously formatted filesystem at the same physical block number can
> pass validation as long as its signature, entry counts and checksum
> match.  Its index entries would then be used in the new filesystem
> context.
> 
> Both fields are written unconditionally when a leaf block is formatted
> in ocfs2_dx_dir_format_cluster(), from the live superblock generation
> and the real block number, so a correctly formatted filesystem cannot
> trip the new checks.  The leaf block number read back here comes from
> on-disk dir index root extent records.
> 
> Reject dir index leaf blocks whose dl_blkno or dl_fs_generation does not
> match, like the dir index root validator does.
> 
> Signed-off-by: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx>
> ---
>  fs/ocfs2/dir.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/fs/ocfs2/dir.c b/fs/ocfs2/dir.c
> index 329680b46227..55c4a305a282 100644
> --- a/fs/ocfs2/dir.c
> +++ b/fs/ocfs2/dir.c
> @@ -733,6 +733,18 @@ static int ocfs2_validate_dx_leaf(struct super_block *sb,
>  		return ocfs2_error(sb, "Dir Index Leaf has bad signature %.*s\n",
>  				   7, dx_leaf->dl_signature);
>  
> +	if (le64_to_cpu(dx_leaf->dl_blkno) != bh->b_blocknr)
> +		return ocfs2_error(sb,
> +				   "Dir Index Leaf # %llu has an invalid dl_blkno of %llu\n",
> +				   (unsigned long long)bh->b_blocknr,
> +				   (unsigned long long)le64_to_cpu(dx_leaf->dl_blkno));

The patch looks fine to me.
Reviewed-by: Heming Zhao <heming.zhao@xxxxxxxx>

Only question: Do we add the same check for dl_blkno in ocfs2_validate_dx_root()?

Thanks,
Heming
> +
> +	if (le32_to_cpu(dx_leaf->dl_fs_generation) != OCFS2_SB(sb)->fs_generation)
> +		return ocfs2_error(sb,
> +				   "Dir Index Leaf # %llu has an invalid dl_fs_generation of #%u\n",
> +				   (unsigned long long)bh->b_blocknr,
> +				   le32_to_cpu(dx_leaf->dl_fs_generation));
> +
>  	if (le16_to_cpu(dx_leaf->dl_list.de_count) !=
>  	    ocfs2_dx_entries_per_leaf(sb))
>  		return ocfs2_error(sb,
> -- 
> 2.39.3
>