From: Christophe Leroy Subject: Re: [PATCH 01/11] crypto: shash: Remove VLA usage Date: Wed, 20 Jun 2018 19:30:50 +0000 Message-ID: <638faf05-946a-1345-dda4-f75fee5b07d9@c-s.fr> References: <20180620190408.45104-1-keescook@chromium.org> <20180620190408.45104-2-keescook@chromium.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Cc: "Gustavo A. R. Silva" , Alasdair Kergon , Arnd Bergmann , Eric Biggers , Giovanni Cabiddu , Lars Persson , Mike Snitzer , Rabin Vincent , Tim Chen , "David S. Miller" , linux-crypto@vger.kernel.org, qat-linux@intel.com, dm-devel@redhat.com, linux-kernel@vger.kernel.org To: Kees Cook , Herbert Xu Return-path: In-Reply-To: <20180620190408.45104-2-keescook@chromium.org> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-crypto.vger.kernel.org On 06/20/2018 07:03 PM, Kees Cook wrote: > In the quest to remove all stack VLA usage from the kernel[1], this > removes the VLAs in SHASH_DESC_ON_STACK (via crypto_shash_descsize()) > by using the maximum allowable size (which is now more clearly captured > in a macro). Similar limits are turned into macros as well. > > [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com > > Signed-off-by: Kees Cook Got the following warnings: crypto/testmgr.c: In function ‘alg_test_crc32c.part.4’: crypto/testmgr.c:1896:1: warning: the frame size of 2088 bytes is larger than 1024 bytes [-Wframe-larger-than=] crypto/hmac.c: In function ‘hmac_setkey’: crypto/hmac.c:88:1: warning: the frame size of 2088 bytes is larger than 1024 bytes [-Wframe-larger-than=] Christophe > --- > crypto/shash.c | 6 +++--- > include/crypto/hash.h | 6 +++++- > 2 files changed, 8 insertions(+), 4 deletions(-) > > diff --git a/crypto/shash.c b/crypto/shash.c > index 5d732c6bb4b2..ab6902c6dae7 100644 > --- a/crypto/shash.c > +++ b/crypto/shash.c > @@ -458,9 +458,9 @@ static int shash_prepare_alg(struct shash_alg *alg) > { > struct crypto_alg *base = &alg->base; > > - if (alg->digestsize > PAGE_SIZE / 8 || > - alg->descsize > PAGE_SIZE / 8 || > - alg->statesize > PAGE_SIZE / 8) > + if (alg->digestsize > SHASH_MAX_DIGESTSIZE || > + alg->descsize > SHASH_MAX_DESCSIZE || > + alg->statesize > SHASH_MAX_STATESIZE) > return -EINVAL; > > base->cra_type = &crypto_shash_type; > diff --git a/include/crypto/hash.h b/include/crypto/hash.h > index 76e432cab75d..308aad8bf523 100644 > --- a/include/crypto/hash.h > +++ b/include/crypto/hash.h > @@ -151,9 +151,13 @@ struct shash_desc { > void *__ctx[] CRYPTO_MINALIGN_ATTR; > }; > > +#define SHASH_MAX_DIGESTSIZE (PAGE_SIZE / 8) > +#define SHASH_MAX_DESCSIZE (PAGE_SIZE / 8) > +#define SHASH_MAX_STATESIZE (PAGE_SIZE / 8) > + > #define SHASH_DESC_ON_STACK(shash, ctx) \ > char __##shash##_desc[sizeof(struct shash_desc) + \ > - crypto_shash_descsize(ctx)] CRYPTO_MINALIGN_ATTR; \ > + SHASH_MAX_DESCSIZE] CRYPTO_MINALIGN_ATTR; \ > struct shash_desc *shash = (struct shash_desc *)__##shash##_desc > > /** >