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From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Date: Fri, 14 Oct 2016 10:21:49 +0100
Message-ID: <CAKv+Gu-Y6wuMGuRgrHRGCvAM9qZjvufs=7VWL8hAUKFSF=tZWg@mail.gmail.com> (sfid-20161014_112217_498274_DE399B0A)
Subject: Re: [mac80211] BUG_ON with current -git (4.8.0-11417-g24532f7)
To: Johannes Berg <johannes@sipsolutions.net>
Cc: Andy Lutomirski <luto@amacapital.net>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        "linux-next@vger.kernel.org" <linux-next@vger.kernel.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
        Network Development <netdev@vger.kernel.org>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        "David S. Miller" <davem@davemloft.net>,
        Linux Wireless List <linux-wireless@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Jouni Malinen <j@w1.fi>
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Sender: linux-wireless-owner@vger.kernel.org

On 14 October 2016 at 10:10, Johannes Berg <johannes@sipsolutions.net> wrote:
> On Fri, 2016-10-14 at 10:05 +0100, Ard Biesheuvel wrote:
>>
>> Indeed. And the decrypt path does the same for auth_tag[].
>
> Hadn't gotten that far, due to the BUG_ON() in CONFIG_DEBUG_SG in the
> encrypt path :)
>
>> But that still means there are two separate problems here, one which
>> affects the WPA code, and one that only affects the generic CCM
>> chaining mode (but not the accelerated arm64 implementation)
>
> Yes. The generic CCM chaining still doesn't typically have a request on
> the stack though. In fact, ESP (net/ipv4/esp4.c) for example will do
> temporary allocations with kmalloc for every frame, it seems.
>

It is annotated with a TODO, though :-)

38320c70d282b (Herbert Xu               2008-01-28 19:35:05 -0800  41)
 * TODO: Use spare space in skb for this where possible.

>> Unsurprisingly, I would strongly prefer those to be fixed properly
>> rather than backing out my patch, but I'm happy to help out whichever
>> solution we reach consensus on.
>
> Yeah, obviously, it would be good to use the accelerated versions after
> all.
>
>> I will check whether this removes the issue when not using
>> crypto/ccm.ko
>
> Ok. I think we can probably live with having those 48 bytes in per-CPU
> buffers, but I suppose we don't really want to have ~500.
>

Agreed.