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From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Gilad Ben-Yossef <gilad@benyossef.com>,
	Kees Cook <keescook@chromium.org>,
	Eric Biggers <ebiggers@google.com>,
	Antoine Tenart <antoine.tenart@bootlin.com>,
	Boris Brezillon <boris.brezillon@bootlin.com>,
	Arnaud Ebalard <arno@natisbad.org>,
	Corentin Labbe <clabbe.montjoie@gmail.com>,
	Maxime Ripard <maxime.ripard@bootlin.com>,
	Chen-Yu Tsai <wens@csie.org>,
	Christian Lamparter <chunkeey@gmail.com>,
	Philippe Ombredanne <pombredanne@nexb.com>,
	Jonathan Cameron <Jonathan.Cameron@huawei.com>,
	"open list:HARDWARE RANDOM NUMBER GENERATOR CORE"
	<linux-crypto@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 2/2] crypto: skcipher: Remove VLA usage for SKCIPHER_REQUEST_ON_STACK
Date: Thu, 6 Sep 2018 11:29:41 +0200	[thread overview]
Message-ID: <CAKv+Gu_0ehX9sLCtUYR00D4iQw+ytwmsLKmG6dgq9EnLjidKFw@mail.gmail.com> (raw)
In-Reply-To: <20180906085100.xcqqftgqg4sizkec@gondor.apana.org.au>

On 6 September 2018 at 10:51, Herbert Xu <herbert@gondor.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.

WARNING: multiple messages have this Message-ID (diff)
From: ard.biesheuvel@linaro.org (Ard Biesheuvel)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 2/2] crypto: skcipher: Remove VLA usage for SKCIPHER_REQUEST_ON_STACK
Date: Thu, 6 Sep 2018 11:29:41 +0200	[thread overview]
Message-ID: <CAKv+Gu_0ehX9sLCtUYR00D4iQw+ytwmsLKmG6dgq9EnLjidKFw@mail.gmail.com> (raw)
In-Reply-To: <20180906085100.xcqqftgqg4sizkec@gondor.apana.org.au>

On 6 September 2018 at 10:51, Herbert Xu <herbert@gondor.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.

  reply	other threads:[~2018-09-06  9:29 UTC|newest]

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-04 18:16 [PATCH 0/2] crypto: Remove VLA usage from skcipher Kees Cook
2018-09-04 18:16 ` Kees Cook
2018-09-04 18:16 ` [PATCH 1/2] crypto: skcipher: Allow crypto_skcipher_set_reqsize() to fail Kees Cook
2018-09-04 18:16   ` Kees Cook
2018-09-04 18:16 ` [PATCH 2/2] crypto: skcipher: Remove VLA usage for SKCIPHER_REQUEST_ON_STACK Kees Cook
2018-09-04 18:16   ` Kees Cook
2018-09-05  6:05   ` Alexander Stein
2018-09-05  6:05     ` Alexander Stein
2018-09-05  6:05     ` Alexander Stein
2018-09-05  9:18   ` Ard Biesheuvel
2018-09-05  9:18     ` Ard Biesheuvel
2018-09-05  9:18     ` Ard Biesheuvel
2018-09-05 21:05     ` Kees Cook
2018-09-05 21:05       ` Kees Cook
2018-09-05 21:05       ` Kees Cook
2018-09-05 22:49       ` Ard Biesheuvel
2018-09-05 22:49         ` Ard Biesheuvel
2018-09-05 22:49         ` Ard Biesheuvel
2018-09-06  0:43         ` Kees Cook
2018-09-06  0:43           ` Kees Cook
2018-09-06  0:43           ` Kees Cook
2018-09-06 20:22           ` Kees Cook
2018-09-06 20:22             ` Kees Cook
2018-09-06 20:22             ` Kees Cook
2018-09-06 22:23             ` Kees Cook
2018-09-06 22:23               ` Kees Cook
2018-09-06 22:23               ` Kees Cook
2018-09-06  4:53         ` Gilad Ben-Yossef
2018-09-06  4:53           ` Gilad Ben-Yossef
2018-09-06  4:53           ` Gilad Ben-Yossef
2018-09-06  7:21           ` Ard Biesheuvel
2018-09-06  7:21             ` Ard Biesheuvel
2018-09-06  7:21             ` Ard Biesheuvel
2018-09-06  8:11             ` Ard Biesheuvel
2018-09-06  8:11               ` Ard Biesheuvel
2018-09-06  8:11               ` Ard Biesheuvel
2018-09-06  8:51               ` Herbert Xu
2018-09-06  8:51                 ` Herbert Xu
2018-09-06  8:51                 ` Herbert Xu
2018-09-06  9:29                 ` Ard Biesheuvel [this message]
2018-09-06  9:29                   ` Ard Biesheuvel
2018-09-06  9:29                   ` Ard Biesheuvel
2018-09-06 13:11                   ` Herbert Xu
2018-09-06 13:11                     ` Herbert Xu
2018-09-06 13:11                     ` Herbert Xu
2018-09-06 14:49                     ` Ard Biesheuvel
2018-09-06 14:49                       ` Ard Biesheuvel
2018-09-06 14:49                       ` Ard Biesheuvel
2018-09-06 19:18                       ` Kees Cook
2018-09-06 19:18                         ` Kees Cook
2018-09-06 19:18                         ` Kees Cook
2018-09-06  8:25             ` Gilad Ben-Yossef
2018-09-06  8:25               ` Gilad Ben-Yossef
2018-09-06  8:25               ` Gilad Ben-Yossef

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