linux-kernel - Re: [PATCH] crypto: ccm - avoid scatterlist for MAC encryption

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Date:   Mon, 17 Oct 2016 08:50:09 +0100
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     Johannes Berg <johannes@...solutions.net>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        "<netdev@...r.kernel.org>" <netdev@...r.kernel.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        "<linux-wireless@...r.kernel.org>" <linux-wireless@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jouni Malinen <j@...fi>
Subject: Re: [PATCH] crypto: ccm - avoid scatterlist for MAC encryption

On 17 October 2016 at 08:47, Johannes Berg <johannes@...solutions.net> wrote:
> On Mon, 2016-10-17 at 08:37 +0100, Ard Biesheuvel wrote:
>>
>> Could we get a statement first whether it is supported to allocate
>> aead_req (and other crypto req structures) on the stack?
>
> Well, we haven't heard from Herbert :)
>
>> If not, then
>> we have our work cut out for us. But if it is, I'd rather we didn't
>> apply the kzalloc/kfree patch, since it is just a workaround for the
>> broken generic CCM driver, for which a fix is already available.
>
> Yeah but I can't apply it. I just fixed up your kzalloc patch to also
> handle GCM and GMAC, and to have error checking. Will send it in a
> minute.
>

I just realised that patch should probably use
aead_request_alloc/aead_request_free [and drop the memset]. That also
fixes the latent bug where the alignment of the req ctx is not take
into account.

>> Also, regarding your __percpu patch: those are located in the vmalloc
>> area as well, at least on arm64, and likely other architectures too.
>
> Crap. Any other bright ideas?
>

kmem_cache_create() and kmem_cache_alloc()