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

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Date:   Tue, 30 Jun 2020 13:01:16 -0400 (EDT)
From:   Mikulas Patocka <mpatocka@...hat.com>
To:     Eric Biggers <ebiggers@...nel.org>
cc:     Mike Snitzer <msnitzer@...hat.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Zaibo Xu <xuzaibo@...wei.com>, linux-kernel@...r.kernel.org,
        Wei Xu <xuwei5@...ilicon.com>, dm-devel@...hat.com,
        George Cherian <gcherian@...vell.com>,
        linux-crypto@...r.kernel.org,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        "David S. Miller" <davem@...emloft.net>,
        Milan Broz <mbroz@...hat.com>
Subject: Re: [dm-devel] [PATCH 1/3 v4] crypto: introduce the flag
 CRYPTO_ALG_ALLOCATES_MEMORY



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