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Date: Thu, 6 Sep 2018 11:29:41 +0200 From: Ard Biesheuvel <ard.biesheuvel@...aro.org> To: Herbert Xu <herbert@...dor.apana.org.au> Cc: Gilad Ben-Yossef <gilad@...yossef.com>, Kees Cook <keescook@...omium.org>, Eric Biggers <ebiggers@...gle.com>, Antoine Tenart <antoine.tenart@...tlin.com>, Boris Brezillon <boris.brezillon@...tlin.com>, Arnaud Ebalard <arno@...isbad.org>, Corentin Labbe <clabbe.montjoie@...il.com>, Maxime Ripard <maxime.ripard@...tlin.com>, Chen-Yu Tsai <wens@...e.org>, Christian Lamparter <chunkeey@...il.com>, Philippe Ombredanne <pombredanne@...b.com>, Jonathan Cameron <Jonathan.Cameron@...wei.com>, "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" <linux-crypto@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, linux-arm-kernel <linux-arm-kernel@...ts.infradead.org> Subject: Re: [PATCH 2/2] crypto: skcipher: Remove VLA usage for SKCIPHER_REQUEST_ON_STACK On 6 September 2018 at 10:51, Herbert Xu <herbert@...dor.apana.org.au> wrote: > On Thu, Sep 06, 2018 at 10:11:59AM +0200, Ard Biesheuvel wrote: >> >> That way, we will almost certainly oops on a NULL pointer dereference >> right after, but we at least the stack corruption. > > A crash is just as bad as a BUG_ON. > > Is this even a real problem? Do we have any users of this construct > that is using it on async algorithms? > 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.
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