linux-kernel - Re: [PATCH v2 2/4] crypto: skcipher - Enforce non-ASYNC for on-stack requests

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Message-ID: <20180911055230.iiiq2uu5gczlwjon@gondor.apana.org.au>
Date:   Tue, 11 Sep 2018 13:52:30 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Eric Biggers <ebiggers@...gle.com>,
        Gilad Ben-Yossef <gilad@...yossef.com>,
        Alexander Stein <alexander.stein@...tec-electronic.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 v2 2/4] crypto: skcipher - Enforce non-ASYNC for on-stack
 requests

On Fri, Sep 07, 2018 at 08:56:23AM +0200, Ard Biesheuvel wrote:
>
> OK, so given that all SKCIPHER_REQUEST_ON_STACK occurrences are
> updated in this series anyway, perhaps we should add
> skcipher_[en|de]crypt_onstack() flavors that encapsulate the
> additional check? Only question is how to enforce at compile time that
> those are used instead of the ordinary ones when using a stack
> allocated request. Would you mind using some macro foo here involving
> __builtin_types_compatible_p() ?

Something like a completely new type which in reality is just a
wrapper around skcipher:

	struct crypto_sync_skcipher {
		struct crypto_skcipher base;
	} tfm;

	tfm = crypto_alloc_sync_skcipher(...);

	crypto_sync_skcipher_encrypt(...)
	crypto_sync_skcipher_decrypt(...)

These functions would just be trivial inline functions around their
crypto_skcipher counterparts.

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