Re: [PATCH] crypto: skcipher - Add skcipher_ialg_simple helper

[Eric Biggers <ebiggers@kernel.org>]

On Fri, Dec 06, 2019 at 01:57:04PM +0800, Herbert Xu wrote:
> This patch introduces the skcipher_ialg_simple helper which fetches
> the crypto_alg structure from a simple skcpiher instance's spawn.
> 
> This allows us to remove the third argument from the function
> skcipher_alloc_instance_simple.
> 
> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
> 
> diff --git a/crypto/cbc.c b/crypto/cbc.c
> index dd96bcf4d4b6..b9c718fe9d7d 100644
> --- a/crypto/cbc.c
> +++ b/crypto/cbc.c
> @@ -54,10 +54,12 @@ static int crypto_cbc_create(struct crypto_template *tmpl, struct rtattr **tb)
>  	struct crypto_alg *alg;
>  	int err;
>  
> -	inst = skcipher_alloc_instance_simple(tmpl, tb, &alg);
> +	inst = skcipher_alloc_instance_simple(tmpl, tb);
>  	if (IS_ERR(inst))
>  		return PTR_ERR(inst);
>  
> +	alg = skcipher_ialg_simple(inst);
> +
>  	err = -EINVAL;
>  	if (!is_power_of_2(alg->cra_blocksize))
>  		goto out_free_inst;

This doesn't seem like an improvement, because skcipher_alloc_instance_simple()
takes a reference to 'alg' which the caller must drop.  It's better to make this
explicit by having 'alg' be one of the return values.

- Eric