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Date: Thu, 14 Mar 2013 00:24:16 -0600
From: Kurt Seifried <kseifried@...hat.com>
To: oss-security@...ts.openwall.com
CC: Sebastian Krahmer <krahmer@...e.de>
Subject: Re: CLONE_NEWUSER|CLONE_FS root exploit

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Hash: SHA1

On 03/13/2013 09:39 AM, Sebastian Krahmer 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. ;)
> 
> regards, Sebastian

Nice find. Please use CVE-2013-1858  for this issue.

- -- 
Kurt Seifried Red Hat Security Response Team (SRT)
PGP: 0x5E267993 A90B F995 7350 148F 66BF 7554 160D 4553 5E26 7993
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