Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
In-Reply-To: <20180626092041.mxfg4lxcvxfivzc2@gondor.apana.org.au>
References: <20180625211026.15819-1-keescook@chromium.org> <20180625211026.15819-12-keescook@chromium.org>
 <20180626092041.mxfg4lxcvxfivzc2@gondor.apana.org.au>
From:   Kees Cook <keescook@chromium.org>
Date:   Tue, 26 Jun 2018 09:45:09 -0700
Message-ID: <CAGXu5jKYb-0NNvOcN79hzqU7O6vCFhMTBDGBL8Knuoc-YHamPg@mail.gmail.com>
Subject: Re: [PATCH v2 11/11] crypto: skcipher: Remove VLA usage for SKCIPHER_REQUEST_ON_STACK
To:     Herbert Xu <herbert@gondor.apana.org.au>
Cc:     "David S. Miller" <davem@davemloft.net>,
        linux-crypto <linux-crypto@vger.kernel.org>,
        "Gustavo A. R. Silva" <gustavo@embeddedor.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Eric Biggers <ebiggers@google.com>,
        Alasdair Kergon <agk@redhat.com>,
        Giovanni Cabiddu <giovanni.cabiddu@intel.com>,
        Lars Persson <larper@axis.com>,
        Mike Snitzer <snitzer@redhat.com>,
        Rabin Vincent <rabinv@axis.com>,
        Tim Chen <tim.c.chen@linux.intel.com>, qat-linux@intel.com,
        dm-devel@redhat.com, LKML <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Tue, Jun 26, 2018 at 2:20 AM, Herbert Xu <herbert@gondor.apana.org.au> wrote:
> On Mon, Jun 25, 2018 at 02:10:26PM -0700, Kees Cook wrote:
>> In the quest to remove all stack VLA usage from the kernel[1], this
>> caps the skcipher request size similar to other limits and adds a
>> sanity check at registration. In a manual review of the callers of
>> crypto_skcipher_set_reqsize(), the largest was 384:
>>
>> 4     sun4i_cipher_req_ctx
>> 6     safexcel_cipher_req
>> 8     cryptd_skcipher_request_ctx
>> 80    cipher_req_ctx
>> 80    skcipher_request
>> 96    crypto_rfc3686_req_ctx
>> 104   nitrox_kcrypt_request
>> 144   mv_cesa_skcipher_std_req
>> 384   rctx
>>
>> [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com
>>
>> Cc: Herbert Xu <herbert@gondor.apana.org.au>
>> Cc: "David S. Miller" <davem@davemloft.net>
>> Cc: linux-crypto@vger.kernel.org
>> Signed-off-by: Kees Cook <keescook@chromium.org>
>
> This has the same issue as the ahash reqsize patch.

Which are likely to be wrapped together? Should I take this to 512 or
something else?

-Kees

-- 
Kees Cook
Pixel Security