On Thu, Sep 6, 2018 at 7:49 AM, Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote: > On 6 September 2018 at 15:11, Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> wrote: >> On Thu, Sep 06, 2018 at 11:29:41AM +0200, Ard Biesheuvel wrote: >>> >>> Perhaps not, but it is not enforced atm. >>> >>> In any case, limiting the reqsize is going to break things, so that >>> needs to occur based on the sync/async nature of the algo. That also >>> means we'll corrupt the stack if we ever end up using >>> SKCIPHER_REQUEST_ON_STACK() with an async algo whose reqsize is >>> greater than the sync reqsize limit, so I do think some additional >>> sanity check is appropriate. >> >> I'd prefer compile-time based checks. Perhaps we can introduce >> a wrapper around crypto_skcipher, say crypto_skcipher_sync which >> could then be used by SKCIPHER_REQUEST_ON_STACK to ensure that >> only sync algorithms can use this construct. >> > > That would require lots of changes in the callers, including ones that > already take care to use sync algos only. > > How about we do something like the below instead? Oh, I like this, thanks! -Kees -- Kees Cook Pixel Security
