From: Kees Cook Subject: [PATCH v8 6/9] crypto alg: Introduce generic max blocksize and alignmask Date: Tue, 7 Aug 2018 14:18:40 -0700 Message-ID: <20180807211843.47586-7-keescook@chromium.org> References: <20180807211843.47586-1-keescook@chromium.org> Cc: Kees Cook , Eric Biggers , Ard Biesheuvel , Giovanni Cabiddu , Alasdair Kergon , Mike Snitzer , Tudor-Dan Ambarus , Andrew Morton , Thomas Gleixner , Geert Uytterhoeven , Arnd Bergmann , Will Deacon , Rasmus Villemoes , David Woodhouse , Matthew Wilcox , "David S. Miller" , "Gustavo A. R. Silva" , linux-crypto@vger.kernel.org, dm-devel@redhat.com, qat-linux@intel.com, l To: Herbert Xu Return-path: In-Reply-To: <20180807211843.47586-1-keescook@chromium.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-crypto.vger.kernel.org In the quest to remove all stack VLA usage from the kernel[1], this exposes a new general upper bound on crypto blocksize and alignmask (higher than for the existing cipher limits) for VLA removal, and introduces new checks. At present, the highest cra_alignmask in the kernel is 63. The highest cra_blocksize is 144 (SHA3_224_BLOCK_SIZE, 18 8-byte words). For the new blocksize limit, I went with 160 (20 8-byte words). [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com Signed-off-by: Kees Cook --- crypto/algapi.c | 7 ++++++- include/crypto/algapi.h | 4 +++- 2 files changed, 9 insertions(+), 2 deletions(-) diff --git a/crypto/algapi.c b/crypto/algapi.c index c0755cf4f53f..496fc51bf215 100644 --- a/crypto/algapi.c +++ b/crypto/algapi.c @@ -57,9 +57,14 @@ static int crypto_check_alg(struct crypto_alg *alg) if (alg->cra_alignmask & (alg->cra_alignmask + 1)) return -EINVAL; - if (alg->cra_blocksize > PAGE_SIZE / 8) + /* General maximums for all algs. */ + if (alg->cra_alignmask > MAX_ALGAPI_ALIGNMASK) return -EINVAL; + if (alg->cra_blocksize > MAX_ALGAPI_BLOCKSIZE) + return -EINVAL; + + /* Lower maximums for specific alg types. */ if (!alg->cra_type && (alg->cra_flags & CRYPTO_ALG_TYPE_MASK) == CRYPTO_ALG_TYPE_CIPHER) { if (alg->cra_alignmask > MAX_CIPHER_ALIGNMASK) diff --git a/include/crypto/algapi.h b/include/crypto/algapi.h index bd5e8ccf1687..21371ac8f355 100644 --- a/include/crypto/algapi.h +++ b/include/crypto/algapi.h @@ -20,8 +20,10 @@ /* * Maximum values for blocksize and alignmask, used to allocate * static buffers that are big enough for any combination of - * ciphers and architectures. + * algs and architectures. Ciphers have a lower maximum size. */ +#define MAX_ALGAPI_BLOCKSIZE 160 +#define MAX_ALGAPI_ALIGNMASK 63 #define MAX_CIPHER_BLOCKSIZE 16 #define MAX_CIPHER_ALIGNMASK 15 -- 2.17.1