Re: [bug] crypto/vmx/p8_ghash memory corruption in 4.8-rc7

From: Marcelo Cerri
Date: Tue Sep 27 2016 - 08:04:33 EST


On Tue, Sep 27, 2016 at 05:01:03AM -0400, Jan Stancek wrote:
> So, if we extended p8_ghash_desc_ctx to accommodate fallback_desc's ctx
> and then provided statesize/import/export, would that be acceptable?
> struct p8_ghash_desc_ctx {
> ...
> struct shash_desc fallback_desc;
> + char fallback_ctx[sizeof(struct ghash_desc_ctx)];

I think so. That's the solution mentioned by Herbert. The only drawback
is that we will need to fix "ghash-generic" as the fallback
implementation in order to know beforehand its descsize.

However I would keep the p8_ghash_desc_ctx the way it is and I would
sum sizeof(struct ghash_desc_ctx) to the algorithm descsize instead.

Let me put a quick patch together to test this.

> Also, does that mean that padlock_sha has similar problem?
> It does not seem to reserve any space for fallback __ctx and it calls
> init()/update()/export() with padlock_sha_desc's fallback:
> struct padlock_sha_desc {
> struct shash_desc fallback;
> };
> static struct shash_alg sha1_alg = {
> .descsize = sizeof(struct padlock_sha_desc),

Yeah. It still seems to me that padlock-sha has the same problem. Maybe
we are missing something...


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