On Wed, Jun 20, 2018 at 12:04:02PM -0700, Kees Cook wrote: > 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 > + How do these differ from MAX_CIPHER_BLOCKSIZE and MAX_CIPHER_ALIGNMASK, and why are they declared in different places? - Eric
