Re: [PATCH 06/11] crypto: cbc: Remove VLA usage

Christophe Leroy
2018-06-20T20:16:46Z

On 06/20/2018 07:04 PM, Kees Cook wrote:
> In the quest to remove all stack VLA usage from the kernel[1], this
> uses the upper bounds on blocksize.
>
> [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com
>
> Signed-off-by: Kees Cook <keescook@chromium.org>

crypto/cbc.c: In function ‘crypto_cbc_decrypt’:
crypto/cbc.c:79:1: warning: the frame size of 2144 bytes is larger than
1024 bytes [-Wframe-larger-than=]

Christophe

> ---
> include/crypto/cbc.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/crypto/cbc.h b/include/crypto/cbc.h
> index f5b8bfc22e6d..260096bcf99b 100644
> --- a/include/crypto/cbc.h
> +++ b/include/crypto/cbc.h
> @@ -113,7 +113,7 @@ static inline int crypto_cbc_decrypt_inplace(
> unsigned int bsize = crypto_skcipher_blocksize(tfm);
> unsigned int nbytes = walk->nbytes;
> u8 *src = walk->src.virt.addr;
> - u8 last_iv[bsize];
> + u8 last_iv[CRYPTO_ALG_MAX_BLOCKSIZE];
>
> /* Start of the last block. */
> src += nbytes - (nbytes & (bsize - 1)) - bsize;
>