Subject: Re: [mac80211] BUG_ON with current -git (4.8.0-11417-g24532f7)

From: Johannes Berg <[email-masked]>
Date: Fri, 14 Oct 2016 11:10:48 +0200

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.

> 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.

johannes