On Fri, Oct 09, 2015 at 06:34:28PM +0800, Herbert Xu wrote: > On Fri, Oct 09, 2015 at 11:29:44AM +0100, Russell King wrote: > > If the algorithm passed a zero statesize, do not pass a valid pointer > > into the export/import functions. Passing a valid pointer covers up > > bugs in driver code which then go on to smash the kernel stack. > > Instead, pass NULL, which will cause any attempt to write to the > > pointer to fail. > > > > Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx> > > The state size should never be zero for a hash algorithm. Having > a zero state means that the hash output must always be identical. > Such an algorithm would be quite useless. > > So how about adding a check upon hash registration to verify that > the state size is greater than zero? The place to do it would be > shash_prepare_alg and ahash_prepare_alg. Do you mean something like this? As statesize is an unsigned int, testing for zero should be sufficient. diff --git a/crypto/ahash.c b/crypto/ahash.c index 8acb886032ae..9c1dc8d6106a 100644 --- a/crypto/ahash.c +++ b/crypto/ahash.c @@ -544,7 +544,8 @@ 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) + alg->halg.statesize > PAGE_SIZE / 8 || + alg->halg.statesize == 0) return -EINVAL; base->cra_type = &crypto_ahash_type; diff --git a/crypto/shash.c b/crypto/shash.c index ecb1e3d39bf0..ab3384b38542 100644 --- a/crypto/shash.c +++ b/crypto/shash.c @@ -585,7 +585,8 @@ static int shash_prepare_alg(struct shash_alg *alg) if (alg->digestsize > PAGE_SIZE / 8 || alg->descsize > PAGE_SIZE / 8 || - alg->statesize > PAGE_SIZE / 8) + alg->statesize > PAGE_SIZE / 8 || + alg->statesize == 0) return -EINVAL; base->cra_type = &crypto_shash_type; -- FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net. -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
