In the quest to remove all stack VLA usage from the kernel[1], this exposes the existing upper bound on crypto block sizes for VLA removal, and introduces a new check for alignmask (current maximum in the kernel is 63 from manual inspection of all cra_alignmask settings). [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@xxxxxxxxxxxxxx Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> --- crypto/algapi.c | 5 ++++- include/linux/crypto.h | 4 ++++ 2 files changed, 8 insertions(+), 1 deletion(-) diff --git a/crypto/algapi.c b/crypto/algapi.c index c0755cf4f53f..760a412b059c 100644 --- a/crypto/algapi.c +++ b/crypto/algapi.c @@ -57,7 +57,10 @@ 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) + if (alg->cra_blocksize > CRYPTO_ALG_MAX_BLOCKSIZE) + return -EINVAL; + + if (alg->cra_alignmask > CRYPTO_ALG_MAX_ALIGNMASK) return -EINVAL; if (!alg->cra_type && (alg->cra_flags & CRYPTO_ALG_TYPE_MASK) == diff --git a/include/linux/crypto.h b/include/linux/crypto.h index 6eb06101089f..e76ffcbd5aa6 100644 --- a/include/linux/crypto.h +++ b/include/linux/crypto.h @@ -134,6 +134,10 @@ */ #define CRYPTO_MAX_ALG_NAME 128 +/* Maximum values for registered algorithms. */ +#define CRYPTO_ALG_MAX_BLOCKSIZE (PAGE_SIZE / 8) +#define CRYPTO_ALG_MAX_ALIGNMASK 63 + /* * The macro CRYPTO_MINALIGN_ATTR (along with the void * type in the actual * declaration) is used to ensure that the crypto_tfm context structure is -- 2.17.1
