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Date:   Thu, 6 Sep 2018 21:11:49 +0800
From:   Herbert Xu <herbert@gondor.apana.org.au>
To:     Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc:     Gilad Ben-Yossef <gilad@benyossef.com>,
        Kees Cook <keescook@chromium.org>,
        Eric Biggers <ebiggers@google.com>,
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        Arnaud Ebalard <arno@natisbad.org>,
        Corentin Labbe <clabbe.montjoie@gmail.com>,
        Maxime Ripard <maxime.ripard@bootlin.com>,
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        <linux-crypto@vger.kernel.org>,
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        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 2/2] crypto: skcipher: Remove VLA usage for
 SKCIPHER_REQUEST_ON_STACK
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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.

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