Re: [dm-devel] [PATCH 1/3 v4] crypto: introduce the flag CRYPTO_ALG_ALLOCATES_MEMORY

Eric Biggers
2020-06-30T16:36:06Z

On Tue, Jun 30, 2020 at 09:56:22AM -0400, Mikulas Patocka wrote:
> Index: linux-2.6/crypto/cryptd.c
> ===================================================================
> --- linux-2.6.orig/crypto/cryptd.c 2020-06-29 16:03:07.346417000 +0200
> +++ linux-2.6/crypto/cryptd.c 2020-06-30 15:49:04.206417000 +0200
> @@ -202,6 +202,7 @@ static inline void cryptd_check_internal
>
> *type |= algt->type & CRYPTO_ALG_INTERNAL;
> *mask |= algt->mask & CRYPTO_ALG_INTERNAL;
> + *mask |= algt->mask & CRYPTO_ALG_INHERITED_FLAGS;
> }

This needs to use the correct logic (crypto_alg_inherited_mask) to decide which
inherited flags to set in 'mask'.

> --- linux-2.6.orig/crypto/adiantum.c 2020-06-29 16:03:07.346417000 +0200
> +++ linux-2.6/crypto/adiantum.c 2020-06-29 16:03:07.346417000 +0200
> @@ -507,7 +507,7 @@ static int adiantum_create(struct crypto
> if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
> return -EINVAL;
>
> - mask = crypto_requires_sync(algt->type, algt->mask);
> + mask = crypto_alg_inherited_mask(algt->type, algt->mask);
>
> inst = kzalloc(sizeof(*inst) + sizeof(*ictx), GFP_KERNEL);
> if (!inst)

This is still missing setting the flags correctly on the template instance being
constructed. The flags need to be inherited from all "inner" algorithms:

inst->alg.base.cra_flags = (streamcipher_alg->base.cra_flags |
blockcipher_alg->cra_flags |
hash_alg->base.cra_flags) &
CRYPTO_ALG_INHERITED_FLAGS;

If we don't do that, the template instance may allocate memory but not have
CRYPTO_ALG_ALLOCATES_MEMORY set.

> Index: linux-2.6/crypto/pcrypt.c
> ===================================================================
> --- linux-2.6.orig/crypto/pcrypt.c 2020-06-29 16:03:07.346417000 +0200
> +++ linux-2.6/crypto/pcrypt.c 2020-06-30 15:47:32.776417000 +0200
> @@ -263,7 +263,9 @@ static int pcrypt_create_aead(struct cry
> if (err)
> goto err_free_inst;
>
> - inst->alg.base.cra_flags = CRYPTO_ALG_ASYNC;
> + inst->alg.base.cra_flags =
> + CRYPTO_ALG_ASYNC |
> + (alg->base.cra_flags & CRYPTO_ALG_INHERITED_FLAGS);
>
> inst->alg.ivsize = crypto_aead_alg_ivsize(alg);
> inst->alg.maxauthsize = crypto_aead_alg_maxauthsize(alg);

And this is still missing setting the mask:

diff --git a/crypto/pcrypt.c b/crypto/pcrypt.c
index 7240e8bbdebb..643f7f1cc91c 100644
--- a/crypto/pcrypt.c
+++ b/crypto/pcrypt.c
@@ -232,12 +232,15 @@ static int pcrypt_create_aead(struct crypto_template *tmpl, struct rtattr **tb,
struct crypto_attr_type *algt;
struct aead_instance *inst;
struct aead_alg *alg;
+ u32 mask;
int err;

algt = crypto_get_attr_type(tb);
if (IS_ERR(algt))
return PTR_ERR(algt);

+ mask = crypto_alg_inherited_mask(algt->type, algt->mask);
+
inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL);
if (!inst)
return -ENOMEM;
@@ -254,7 +257,7 @@ static int pcrypt_create_aead(struct crypto_template *tmpl, struct rtattr **tb,
goto err_free_inst;

err = crypto_grab_aead(&ctx->spawn, aead_crypto_instance(inst),
- crypto_attr_alg_name(tb[1]), 0, 0);
+ crypto_attr_alg_name(tb[1]), 0, mask);
if (err)
goto err_free_inst;

Can you please think logically about what you're trying to accomplish?

In particular, if someone requests an algorithm that doesn't allocate memory
(which is indicated by type=0, mask=CRYPTO_ALG_ALLOCATES_MEMORY), that request
needs to be honored.

- Eric