Re: [v2.6.34-stable 71/77] crypto: ghash - Avoid null pointer dereference if no key is set

Nick Bowler
2013-01-09T02:56:35Z

On 2013-01-08 18:35 -0500, Paul Gortmaker wrote:
> From: Nick Bowler <nbowler@elliptictech.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.

I haven't been following 2.6.34-longterm development, but unless
you've also backported the AF_ALG userspace interface from 2.6.38,
this sequence can only be triggered by kernel code. So while this
patch shouldn't break anything, it isn't really necessary.

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