[PATCH 1/2] MODSIGN: check hash of kernel module in blacklist

[David Howells]

Lee, Chun-Yi <joeyli.kernel at gmail.com> wrote:

> +		desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
> +		digest_size = crypto_shash_digestsize(tfm);
> +		digest = kzalloc(digest_size + desc_size, GFP_KERNEL);
> +		if (!digest) {
> +			pr_err("digest memory buffer allocate fail\n");
> +			ret = -ENOMEM;
> +			goto error_digest;
> +		}
> +		desc = (void *)digest + digest_size;
> +		desc->tfm = tfm;
> +		desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
> +		ret = crypto_shash_init(desc);
> +		if (ret < 0)
> +			goto error_shash;
> +
> +		ret = crypto_shash_finup(desc, mod, modlen, digest);
> +		if (ret < 0)
> +			goto error_shash;

Can you use the digest generated by mod_make_digest() to avoid computing the
hash twice?

David