Re: Linux 3.4+: arbitrary write with CONFIG_X86_X32 (CVE-2014-0038)

[mancha <mancha1 () hush com>]

On Sun, 02 Feb 2014 08:14:44 +0400, Solar Designer wrote:

> On Fri, Jan 31, 2014 at 04:11:16AM +0400, Solar Designer wrote:
> > <grsecurity> I would not be surprised to see an exploit for this within the next few days
>
> Just off Twitter:
>
> <noptrix> recvmmsg.c - linux 3.4+ local root (CONFIG_X86_X32=y) expl0it - http://pastebin.com/DH3Lbg54
>
> SHA-256(recvmmsg.c.txt) = 4603acf96e845cecd2c5877a68fa5b5c591ba00c52859ded2a31a9daf48a457d
>
> for the version I just downloaded (but did not review, although it looks
> sane at first glance).  The exploit includes offsets for 3 Ubuntu kernels.
>
> Alexander

The exploit by Rebel works as advertised. I've confirmed on a non-Ubuntu box 
after making some changes.

Attached find a kernel module I've authored that protects from the attack.

I'm sharing it for folks currently on vulnerable systems still waiting on
patches from their upstream.

 # make
 # insmod nox32recvmmsg.ko

note: rmmod'ing restores original (vulnerable) state.

--mancha