linux-kernel - Re: [v2.6.34-stable 004/213] crypto: ghash - Avoid null pointer dereference if no key is set

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Message-ID: <20140205203027.GA23845@elliptictech.com>
Date:	Wed, 5 Feb 2014 15:30:27 -0500
From:	Nick Bowler <nbowler@...iptictech.com>
To:	Paul Gortmaker <paul.gortmaker@...driver.com>
CC:	<stable@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Herbert Xu <herbert@...dor.apana.org.au>
Subject: Re: [v2.6.34-stable 004/213] crypto: ghash - Avoid null pointer
 dereference if no key is set

On 2014-02-05 14:59 -0500, Paul Gortmaker wrote:
> From: Nick Bowler <nbowler@...iptictech.com>
> 
>                    -------------------
>     This is a commit scheduled for the next v2.6.34 longterm release.
>     http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git
>     If you see a problem with using this for longterm, please comment.
>                    -------------------
> 
> commit 7ed47b7d142ec99ad6880bbbec51e9f12b3af74c upstream.
> 
> The ghash_update function passes a pointer to gf128mul_4k_lle which will
> be NULL if ghash_setkey is not called or if the most recent call to
> ghash_setkey failed to allocate memory.  This causes an oops.  Fix this
> up by returning an error code in the null case.
> 
> This is trivially triggered from unprivileged userspace through the
> AF_ALG interface by simply writing to the socket without setting a key.

After all this time, I see this patch still manages to find its way,
occasionally, into the patch queue for older -stable. :)

It should be harmless to apply, but this patch doesn't actually fix
any real problem on kernels previous to 2.6.38 because the AF_ALG
userspace interface does not exist in these kernels.

Cheers,
-- 
Nick Bowler, Elliptic Technologies (http://www.elliptictech.com/)
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