linux-kernel - Re: Linux 3.6-rc5

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Date:	Sun, 9 Sep 2012 23:09:28 +0200
From:	Mathias Krause <minipli@...glemail.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	Mathias Krause <minipli@...glemail.com>,
	Romain Francoise <romain@...bokech.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux Crypto Mailing List <linux-crypto@...r.kernel.org>
Subject: Re: Linux 3.6-rc5

On Sun, Sep 09, 2012 at 02:00:00PM -0700, Herbert Xu wrote:
> On Sun, Sep 09, 2012 at 10:09:10PM +0200, Mathias Krause wrote:
> >
> > It happens with the C variants of SHA1 and AES, too. You can easily
> > trigger the bug with Steffen's crconf[1]:
> > 
> > $ crconf add alg "authenc(hmac(sha1-generic),cbc(aes-generic))" type 3
> > 
> > So the problem is likely not related to sha1-ssse3.ko or aesni-intel.ko.
> 
> Thanks! I think this patch should fix the problem.  Can someone
> please confirm this?
> 
> crypto: authenc - Fix crash with zero-length assoc data
> 
> The authenc code doesn't deal with zero-length associated data
> correctly and ends up constructing a zero-length sg entry which
> causes a crash when it's fed into the crypto system.
> 
> This patch fixes this by avoiding the code-path that triggers
> the SG construction if we have no associated data.
> 
> This isn't the most optimal fix as it means that we'll end up
> using the fallback code-path even when we could still execute
> the digest function.  However, this isn't a big deal as nobody
> but the test path would supply zero-length associated data.
> 
> Reported-by: Romain Francoise <romain@...bokech.com>
> Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>

Looks good to me.

> 
> diff --git a/crypto/authenc.c b/crypto/authenc.c
> index 5ef7ba6..d0583a4 100644
> --- a/crypto/authenc.c
> +++ b/crypto/authenc.c
> @@ -336,7 +336,7 @@ static int crypto_authenc_genicv(struct aead_request *req, u8 *iv,
>  		cryptlen += ivsize;
>  	}
>  
> -	if (sg_is_last(assoc)) {
> +	if (req->assoclen && sg_is_last(assoc)) {
>  		authenc_ahash_fn = crypto_authenc_ahash;
>  		sg_init_table(asg, 2);
>  		sg_set_page(asg, sg_page(assoc), assoc->length, assoc->offset);
> @@ -490,7 +490,7 @@ static int crypto_authenc_iverify(struct aead_request *req, u8 *iv,
>  		cryptlen += ivsize;
>  	}
>  
> -	if (sg_is_last(assoc)) {
> +	if (req->assoclen && sg_is_last(assoc)) {
>  		authenc_ahash_fn = crypto_authenc_ahash;
>  		sg_init_table(asg, 2);
>  		sg_set_page(asg, sg_page(assoc), assoc->length, assoc->offset);
> 

Tested-by: Mathias Krause <minipli@...glemail.com>

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