Re: [PATCH] xfs: check hash ordering in xfs_da3_node_verify

["Darrick J. Wong" <djwong@kernel.org>]

On Wed, Apr 15, 2026 at 08:12:24AM +0100, Yuto Ohnuki wrote:
> The DA node verifier checks header fields such as level and count, but
> it does not verify that the btree hash values are in non-decreasing
> order.
> 
> DA node blocks are traversed by searching the btree array for the first
> hash value that exceeds the lookup hash, which requires the hash values
> to be ordered correctly.
> 
> Add a hash order check to xfs_da3_node_verify, similar to the existing
> validation in xfs_dir3_leaf_check_int, so that misordered node
> blocks are detected as metadata corruption.
> 
> Signed-off-by: Yuto Ohnuki <ytohnuki@amazon.com>
> ---
>  fs/xfs/libxfs/xfs_da_btree.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_da_btree.c b/fs/xfs/libxfs/xfs_da_btree.c
> index ad801b7bd2dd..ef49df22899e 100644
> --- a/fs/xfs/libxfs/xfs_da_btree.c
> +++ b/fs/xfs/libxfs/xfs_da_btree.c
> @@ -225,6 +225,7 @@ xfs_da3_node_verify(
>  	struct xfs_da_intnode	*hdr = bp->b_addr;
>  	struct xfs_da3_icnode_hdr ichdr;
>  	xfs_failaddr_t		fa;
> +	int			i;
>  
>  	xfs_da3_node_hdr_from_disk(mp, &ichdr, hdr);
>  
> @@ -247,7 +248,12 @@ xfs_da3_node_verify(
>  	    ichdr.count > mp->m_attr_geo->node_ents)
>  		return __this_address;
>  
> -	/* XXX: hash order check? */
> +	/* Check hash value order. */
> +	for (i = 0; i + 1 < ichdr.count; i++) {

I guess that works, though I'd have iterated from i to ichdr.count and
done the test on the previous element (like scrub/dir.c does).

> +		if (be32_to_cpu(ichdr.btree[i].hashval) >
> +				be32_to_cpu(ichdr.btree[i + 1].hashval))

I think this might be one of the few places where doing kernel style
indentation of the if test flows better:

	for (i = 1; i < ichdr.count; i++) {
		if (be32_to_cpu(ichdr.btree[i - 1].hashval) >
		    be32_to_cpu(ichdr.btree[i].hashval))

The logic is solid though.

--D

> +			return __this_address;
> +	}
>  
>  	return NULL;
>  }
> -- 
> 2.50.1
> 
> 
> 
> 
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