From: Kees Cook Subject: [PATCH v8 4/9] crypto: hash: Remove VLA usage Date: Tue, 7 Aug 2018 14:18:38 -0700 Message-ID: <20180807211843.47586-5-keescook@chromium.org> References: <20180807211843.47586-1-keescook@chromium.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Giovanni Cabiddu , Matthew Wilcox , linux-kernel@vger.kernel.org, Kees Cook , Mike Snitzer , Ard Biesheuvel , Rasmus Villemoes , Eric Biggers , Will Deacon , qat-linux@intel.com, Arnd Bergmann , "David S. Miller" , "Gustavo A. R. Silva" , dm-devel@redhat.com, Geert Uytterhoeven , David Woodhouse , Tudor-Dan Ambarus , Andrew Morton , Thomas Gleixner , Alasdair Kergon , linux-crypto@vger.kernel.org To: Herbert Xu Return-path: In-Reply-To: <20180807211843.47586-1-keescook@chromium.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com List-Id: linux-crypto.vger.kernel.org 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), along with a few other cases. Similar limits are turned into macros as well. A review of existing sizes shows that SHA512_DIGEST_SIZE (64) is the largest digest size and that sizeof(struct sha3_state) (360) is the largest descriptor size. The corresponding maximums are reduced. [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com Signed-off-by: Kees Cook --- crypto/ahash.c | 4 ++-- crypto/algif_hash.c | 2 +- crypto/shash.c | 6 +++--- include/crypto/hash.h | 6 +++++- 4 files changed, 11 insertions(+), 7 deletions(-) diff --git a/crypto/ahash.c b/crypto/ahash.c index a64c143165b1..78aaf2158c43 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 > HASH_MAX_DIGESTSIZE || + alg->halg.statesize > HASH_MAX_STATESIZE || alg->halg.statesize == 0) return -EINVAL; diff --git a/crypto/algif_hash.c b/crypto/algif_hash.c index bfcf595fd8f9..d0cde541beb6 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[HASH_MAX_STATESIZE]; struct sock *sk2; struct alg_sock *ask2; struct hash_ctx *ctx2; diff --git a/crypto/shash.c b/crypto/shash.c index 5d732c6bb4b2..86d76b5c626c 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 > HASH_MAX_DIGESTSIZE || + alg->descsize > HASH_MAX_DESCSIZE || + alg->statesize > HASH_MAX_STATESIZE) return -EINVAL; base->cra_type = &crypto_shash_type; diff --git a/include/crypto/hash.h b/include/crypto/hash.h index 76e432cab75d..21587011ab0f 100644 --- a/include/crypto/hash.h +++ b/include/crypto/hash.h @@ -151,9 +151,13 @@ struct shash_desc { void *__ctx[] CRYPTO_MINALIGN_ATTR; }; +#define HASH_MAX_DIGESTSIZE 64 +#define HASH_MAX_DESCSIZE 360 +#define HASH_MAX_STATESIZE 512 + #define SHASH_DESC_ON_STACK(shash, ctx) \ char __##shash##_desc[sizeof(struct shash_desc) + \ - crypto_shash_descsize(ctx)] CRYPTO_MINALIGN_ATTR; \ + HASH_MAX_DESCSIZE] CRYPTO_MINALIGN_ATTR; \ struct shash_desc *shash = (struct shash_desc *)__##shash##_desc /** -- 2.17.1