Re: [PATCH v4 11/14] treewide: Prepare to remove VLA usage for AHASH_REQUEST_ON_STACK

[Herbert Xu]

On Thu, Jul 12, 2018 at 08:33:24PM -0700, Kees Cook wrote:
> On Thu, Jul 12, 2018 at 5:40 PM, Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> wrote:
> > On Thu, Jul 12, 2018 at 06:02:26PM +0200, Arnd Bergmann wrote:
> >>
> >> Looking through some of the drivers, I found this interesting one:
> >
> > As I said before these patches are fundamentally broken.  Users
> > of AHASH_REQUEST_ON_STACK can only use sync algorithm providers
> > and therefore drivers are irrelevant.
> 
> I don't understand what this means. Can you give an example of what
> you want to see happen that will accomplish the VLA removals?

Any algorithm that is async must be ignored when you're calculating
the maximum on-stack size of the request.  For example, sha512-mb
is marked as async and therefore must not be used in conjunction
with AHASH_REQUEST_ON_STACK.

Cheers,
-- 
Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Home Page: http://gondor.apana.org.au/~herbert/
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