Re: CLONE_NEWUSER|CLONE_FS root exploit

[Eugene Teo <eugeneteo () kernel sg>]

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

Eugene