On Tue, Jul 17, 2018 at 9:39 AM, Eric Biggers <ebiggers3@xxxxxxxxx> wrote: > On Mon, Jul 16, 2018 at 09:21:44PM -0700, 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@xxxxxxxxxxxxxx >> >> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> >> --- >> 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 ae14cc0e0cdb..4fcd0e2368cd 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 512 >> +#define AHASH_MAX_STATESIZE 512 >> + > > Why is AHASH_MAX_DIGESTSIZE (512) so much larger than SHASH_MAX_DIGESTSIZE (64)? > I would have expected them to be the same. This was a direct replacement of the PAGE_SIZE / 8 original limit. This this didn't trip any frame size warnings, it seemed like we didn't need to do the more narrow limitations done elsewhere. I am, of course, happy to do a manual review and find a lower alternative if that's desired. -Kees -- Kees Cook Pixel Security
