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

[Eric Biggers]

On Wed, Jun 20, 2018 at 12:04:03PM -0700, 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@xxxxxxxxxxxxxx
> 
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
>  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];
>  

Why not MAX_CIPHER_BLOCKSIZE?

- Eric