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

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Message-ID: <20200630163552.GA837@sol.localdomain>
Date:   Tue, 30 Jun 2020 09:35:52 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     Mikulas Patocka <mpatocka@...hat.com>
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, 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