linux-kernel - Re: [PATCH] crypto: af_alg - add async support to algif

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Date:	Thu, 28 Jan 2016 18:09:55 +0100
From:	Stephan Mueller <smueller@...onox.de>
To:	Tadeusz Struk <tadeusz.struk@...el.com>
Cc:	herbert@...dor.apana.org.au, linux-crypto@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] crypto: af_alg - add async support to algif_aead

Am Donnerstag, 28. Januar 2016, 08:00:25 schrieb Tadeusz Struk:

Hi Tadeusz,

>Hi Stephan,
>
>On 01/27/2016 10:26 PM, Stephan Mueller wrote:
>>> +	for (i = 0; i < areq->tsgls; i++)
>>> 
>>> > +		put_page(sg_page(sg + i));
>> 
>> Shouldn't here be the same logic as in put_sgl? I.e.
>> 
>>         for (i = 0; i < sgl->cur; i++) {
>>         
>>                 if (!sg_page(sg + i))
>>                 
>>                         continue;
>>                 
>>                 put_page(sg_page(sg + i));
>>                 sg_assign_page(sg + i, NULL);
>>         
>>         }
>
>Thanks for reviewing.
>I don't think it is possible that there ever will be any gaps in the tsgl.
>In fact if there is such a possibility then it is a serious problem, because
>it would mean that we are sending NULL ptrs to the ciphers (see line 640):
>
>	sg_mark_end(sgl->sg + sgl->cur - 1);
>	aead_request_set_crypt(&ctx->aead_req, sgl->sg, ctx-
>first_rsgl.sgl.sg,
>			       used, ctx->iv);
>
>I don't see any implementation checking for null in sgls. Most of them just
>do:
>
>	for_each_sg(sgl, sg, nents, i)
>		sg_virt(sg)...
>
>So it would Oops there. I think this check in put_sgl is redundant.
>Thanks,

algif_skcipher does a similar check in skcipher_pull_sgl:

...
                        if (!sg_page(sg + i))
                                continue;
...
                        if (put)
                                put_page(sg_page(sg + i));
                        sg_assign_page(sg + i, NULL);
...


Ciao
Stephan