linux-kernel - Re: CLONE_NEWUSER|CLONE

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Date:	Wed, 13 Mar 2013 11:35:15 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Kees Cook <keescook@...omium.org>
Cc:	Sebastian Krahmer <krahmer@...e.de>, linux-kernel@...r.kernel.org,
	Oleg Nesterov <oleg@...hat.com>,
	Linux Containers <containers@...ts.linux-foundation.org>
Subject: Re: CLONE_NEWUSER|CLONE_FS root exploit

Kees Cook <keescook@...omium.org> writes:

> Hi,
>
> It seem like we should block (at least) this combination. On 3.9, this
> exploit works once uidmapping is added.
>
> http://www.openwall.com/lists/oss-security/2013/03/13/10

Yes.  That is a bad combination.  It let's chroot confuse privileged
processes.

Now to figure out if this is easier to squash by adding a user_namespace
to fs_struct or by just forbidding this combination.

Eric
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