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

From: Ard Biesheuvel
Date: Fri Oct 14 2016 - 05:22:05 EST

On 14 October 2016 at 10:10, Johannes Berg <johannes@xxxxxxxxxxxxxxxx> 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.