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

Mikulas Patocka
2020-06-30T17:01:31Z

On Tue, 30 Jun 2020, Eric Biggers wrote:

> 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'.

I added "*mask |= crypto_alg_inherited_mask(algt->type, algt->mask);"
there.

> > --- 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.

OK

> > 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);

What's wrong with this?

> 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;
>

I added "mask" there - but there is still a "mask" argument that is
unused - is it a bug to have two "mask" variables?

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

I am not an expert in crypto code.

> 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

Mikulas