Re: [PATCH] xfs: Verify DA node btree hash order

[Darrick J. Wong]

On Sat, Apr 12, 2025 at 08:03:57PM +0000, Charalampos Mitrodimas wrote:
> The xfs_da3_node_verify() function checks the integrity of directory
> and attribute B-tree node blocks. However, it was missing a check to
> ensure that the hash values of the btree entries within the node are
> strictly increasing, as required by the B-tree structure.
> 
> Add a loop to iterate through the btree entries and verify that each
> entry's hash value is greater than the previous one. If an
> out-of-order hash value is detected, return failure to indicate
> corruption.
> 
> This addresses the "XXX: hash order check?" comment and improves
> corruption detection for DA node blocks.
> 
> Signed-off-by: Charalampos Mitrodimas <charmitro@xxxxxxxxxx>
> ---
>  fs/xfs/libxfs/xfs_da_btree.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_da_btree.c b/fs/xfs/libxfs/xfs_da_btree.c
> index 17d9e6154f1978ce5a5cb82176eea4d6b9cd768d..6c748911e54619c3ceae9b81f55cf61da6735f01 100644
> --- a/fs/xfs/libxfs/xfs_da_btree.c
> +++ b/fs/xfs/libxfs/xfs_da_btree.c
> @@ -247,7 +247,16 @@ xfs_da3_node_verify(
>  	    ichdr.count > mp->m_attr_geo->node_ents)
>  		return __this_address;
>  
> -	/* XXX: hash order check? */
> +	/* Check hash order */
> +	uint32_t prev_hash = be32_to_cpu(ichdr.btree[0].hashval);
> +
> +	for (int i = 1; i < ichdr.count; i++) {
> +		uint32_t curr_hash = be32_to_cpu(ichdr.btree[i].hashval);
> +
> +		if (curr_hash <= prev_hash)

Does XFS support a directory with two names that hash to the same value?

--D

> +			return __this_address;
> +		prev_hash = curr_hash;
> +	}
>  
>  	return NULL;
>  }
> 
> ---
> base-commit: ecd5d67ad602c2c12e8709762717112ef0958767
> change-id: 20250412-xfs-hash-check-be7397881a2c
> 
> Best regards,
> -- 
> Charalampos Mitrodimas <charmitro@xxxxxxxxxx>
> 
>