Re: [PATCH v2 11/11] crypto: skcipher: Remove VLA usage for SKCIPHER_REQUEST_ON_STACK

Kees Cook
2018-06-26T16:45:18Z

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