Re: [PATCH 03/11] crypto: ahash: Remove VLA usage

Christophe Leroy
2018-06-20T20:13:07Z

On 06/20/2018 07:04 PM, Kees Cook wrote:
> In the quest to remove all stack VLA usage from the kernel[1], this
> introduces max size macros for ahash, as already done for shash, and
> adjust the crypto user to max state size.
>
> [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com
>
> Signed-off-by: Kees Cook <keescook@chromium.org>

I get:

crypto/algif_hash.c: In function ‘hash_accept’:
crypto/algif_hash.c:276:1: warning: the frame size of 2048 bytes is
larger than 1024 bytes [-Wframe-larger-than=]

Christophe

> ---
> crypto/ahash.c | 4 ++--
> crypto/algif_hash.c | 2 +-
> include/crypto/hash.h | 3 +++
> 3 files changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/crypto/ahash.c b/crypto/ahash.c
> index a64c143165b1..6435bdbe42fd 100644
> --- a/crypto/ahash.c
> +++ b/crypto/ahash.c
> @@ -550,8 +550,8 @@ static int ahash_prepare_alg(struct ahash_alg *alg)
> {
> struct crypto_alg *base = &alg->halg.base;
>
> - if (alg->halg.digestsize > PAGE_SIZE / 8 ||
> - alg->halg.statesize > PAGE_SIZE / 8 ||
> + if (alg->halg.digestsize > AHASH_MAX_DIGESTSIZE ||
> + alg->halg.statesize > AHASH_MAX_STATESIZE ||
> alg->halg.statesize == 0)
> return -EINVAL;
>
> diff --git a/crypto/algif_hash.c b/crypto/algif_hash.c
> index bfcf595fd8f9..8974ee8ebead 100644
> --- a/crypto/algif_hash.c
> +++ b/crypto/algif_hash.c
> @@ -239,7 +239,7 @@ static int hash_accept(struct socket *sock, struct socket *newsock, int flags,
> struct alg_sock *ask = alg_sk(sk);
> struct hash_ctx *ctx = ask->private;
> struct ahash_request *req = &ctx->req;
> - char state[crypto_ahash_statesize(crypto_ahash_reqtfm(req)) ? : 1];
> + char state[AHASH_MAX_STATESIZE];
> struct sock *sk2;
> struct alg_sock *ask2;
> struct hash_ctx *ctx2;
> diff --git a/include/crypto/hash.h b/include/crypto/hash.h
> index 308aad8bf523..b9df568dc98e 100644
> --- a/include/crypto/hash.h
> +++ b/include/crypto/hash.h
> @@ -64,6 +64,9 @@ struct ahash_request {
> void *__ctx[] CRYPTO_MINALIGN_ATTR;
> };
>
> +#define AHASH_MAX_DIGESTSIZE (PAGE_SIZE / 8)
> +#define AHASH_MAX_STATESIZE (PAGE_SIZE / 8)
> +
> #define AHASH_REQUEST_ON_STACK(name, ahash) \
> char __##name##_desc[sizeof(struct ahash_request) + \
> crypto_ahash_reqsize(ahash)] CRYPTO_MINALIGN_ATTR; \
>