linux-kernel - Re: [PATCH V6 5/7] crypto: AES CBC multi-buffer glue code

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Date:   Tue, 18 Jul 2017 17:52:34 -0700
From:   Tim Chen <tim.c.chen@...ux.intel.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>,
        Megha Dey <megha.dey@...ux.intel.com>
Cc:     davem@...emloft.net, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org, megha.dey@...el.com
Subject: Re: [PATCH V6 5/7] crypto: AES CBC multi-buffer glue code

On 07/17/2017 10:41 PM, Herbert Xu wrote:
> On Tue, Jun 27, 2017 at 05:26:13PM -0700, Megha Dey wrote:
>>
>> +static void completion_callback(struct mcryptd_skcipher_request_ctx *rctx,
>> +			    struct mcryptd_alg_cstate *cstate,
>> +			    int err)
>> +{
>> +	struct skcipher_request *req = cast_mcryptd_ctx_to_req(rctx);
>> +
>> +       /* remove from work list and invoke completion callback */
>> +	spin_lock(&cstate->work_lock);
>> +	list_del(&rctx->waiter);
>> +	spin_unlock(&cstate->work_lock);
>> +
>> +	if (irqs_disabled())
>> +		rctx->complete(&req->base, err);
>> +	else {
>> +		local_bh_disable();
>> +		rctx->complete(&req->base, err);
>> +		local_bh_enable();
>> +	}
>> +}
> 
> The fact that you need to do this check means that this design is
> wrong.  You should always know what context you are in.
> 

I think you are right.  The irqs_disabled check is not necessary
as we only call this function in the context of the mcryptd thread.
When I wrote the original mb algorithms I was probably unsure
and put this check in as a precaution in other mb algorithms and
Megha did the same.

>> +/*
>> + * CRYPTO_ALG_ASYNC flag is passed to indicate we have an ablk
>> + * scatter-gather walk.
>> + */
>> +static struct skcipher_alg aes_cbc_mb_alg = {
>> +	.base = {
>> +		.cra_name		= "cbc(aes)",
>> +		.cra_driver_name	= "cbc-aes-aesni-mb",
>> +		.cra_priority		= 500,
>> +		.cra_flags		= CRYPTO_ALG_INTERNAL,
>> +		.cra_blocksize		= AES_BLOCK_SIZE,
>> +		.cra_ctxsize		= CRYPTO_AES_CTX_SIZE,
>> +		.cra_module		= THIS_MODULE,
>> +	},
>> +	.min_keysize	= AES_MIN_KEY_SIZE,
>> +	.max_keysize	= AES_MAX_KEY_SIZE,
>> +	.ivsize		= AES_BLOCK_SIZE,
>> +	.setkey		= aes_set_key,
>> +	.encrypt	= mb_aes_cbc_encrypt,
>> +	.decrypt	= mb_aes_cbc_decrypt
>> +};
> 
> So this claims to be a sync algorithm.  Is this really the case?
> 
> Cheers,
>