From: Andy Lutomirski <luto@amacapital.net>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Kees Cook <keescook@chromium.org>,
containers@lists.linux-foundation.org,
Sebastian Krahmer <krahmer@suse.de>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Oleg Nesterov <oleg@redhat.com>
Subject: Re: CLONE_NEWUSER|CLONE_FS root exploit
Date: Wed, 13 Mar 2013 18:48:23 -0700 [thread overview]
Message-ID: <51412C67.30908@mit.edu> (raw)
In-Reply-To: <87r4jjkv18.fsf@xmission.com>
On 03/13/2013 11:35 AM, Eric W. Biederman wrote:
> Kees Cook <keescook-F7+t8E8rja9g9hUCZPvPmw@public.gmane.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.
It's worth making sure that setns(2) doesn't have similar issues.
Looking through other shared-but-not-a-namespace things, there are:
fs_struct: Buggy as noted.
files_struct: Probably harmless -- SCM_RIGHTS can emulate it
signal_struct: This interacts with the tty code. Is it okay?
sighand_struct: Looks safe. Famous last words.
FWIW, I've been alarmed in the past that struct path (e.g. the root
directory) implies an mnt_namespace (hidden in struct mount), and it's
entirely possible for the root directory's mnt_namespace not to match
nsproxy->mnt_namespace. I'm not sure what the implications are, but
this doesn't seem healthy.
--Andy
next prev parent reply other threads:[~2013-03-14 1:48 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-13 17:57 CLONE_NEWUSER|CLONE_FS root exploit Kees Cook
2013-03-13 18:35 ` Eric W. Biederman
2013-03-14 1:48 ` Andy Lutomirski [this message]
2013-03-14 20:29 ` Eric W. Biederman
2013-03-14 21:32 ` Andy Lutomirski
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