Re: [PATCH v3 3/8] fs-verity: define a function to return the integrity protected file digest

[Eric Biggers <ebiggers@xxxxxxxxxx>]

On Tue, Jan 25, 2022 at 07:06:53PM -0500, Mimi Zohar wrote:
> +	hash_alg = vi->tree_params.hash_alg;
> +	memset(digest, 0, FS_VERITY_MAX_DIGEST_SIZE);
> +
> +	/* convert hash algorithm to hash_algo_name */
> +	i = match_string(hash_algo_name, HASH_ALGO__LAST, hash_alg->name);
> +	if (i < 0)
> +		return -EINVAL;
> +	*alg = i;

The above comment is backwards.  This code is converting a hash algorithm name
to an ID.  The comment is unclear, but it sounds like it's saying the opposite.

> +
> +	memcpy(digest, vi->file_digest, hash_alg->digest_size);

Here there are two "sources of truth" for the digest size.  How about checking
that they are the same:

	if (WARN_ON_ONCE(hash_alg->digest_size != hash_digest_size[*alg]))
		return -EINVAL;

- Eric