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

[Kees Cook]

On Tue, Jun 26, 2018 at 2:20 AM, Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxx
>>
>> Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
>> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
>> Cc: linux-crypto@xxxxxxxxxxxxxxx
>> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
>
> 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