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Re: CLONE_NEWUSER|CLONE_FS root exploit
From: Agostino Sarubbo <ago () gentoo org>
Date: Mon, 18 Mar 2013 16:36:40 +0100

On Wednesday 13 March 2013 18:33:00 Greg KH wrote:
On Thu, Mar 14, 2013 at 09:03:20AM +0800, Eugene Teo wrote:
On 14 Mar, 2013, at 8:59 AM, Eugene Teo <eugeneteo () kernel sg> wrote:
On 13 Mar, 2013, at 11:39 PM, Sebastian Krahmer <krahmer () suse de> wrote:
Hi,

Seems like CLONE_NEWUSER|CLONE_FS might be a forbidden
combination.
During evaluating the new user namespace thingie, it turned out
that its trivially exploitable to get a (real) uid 0,
as demonstrated here:

http://stealth.openwall.net/xSports/clown-newuser.c

The trick is to setup a chroot in your CLONE_NEWUSER,
but also affecting the parent, which is running
in the init_user_ns, but with the chroot shared.
Then its trivial to get a rootshell from that.

Tested on a openSUSE12.1 with a custom build 3.8.2 (x86_64).

I hope I didnt make anything wrong, mixing up the UIDs,
or disabled important checks during kernel build on my test
system. ;)

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?
id=aea8b5d1e5c5482e7cdda849dc16d728f7080289> 
I realised that the link is incorrect. Will post again when I see the
patches.
It is commit e66eded8309ebf679d3d3c1f5820d1f2ca332c71 in Linus's tree,
so replace the sha in the above link with this one instead.

Someone know exactly in which version the bug appears and which series are 
affected?
-- 
Agostino Sarubbo
Gentoo Linux Developer


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