netdev - Re: [systemd-devel] [PATCH] netns: unix: only allow to find out unix socket in same net namespace

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Date:	Mon, 26 Aug 2013 03:53:01 +0000
From:	James Bottomley <jbottomley@...allels.com>
To:	Gao feng <gaofeng@...fujitsu.com>
CC:	Kay Sievers <kay@...y.org>,
	"systemd-devel@...ts.freedesktop.org" 
	<systemd-devel@...ts.freedesktop.org>,
	"libvir-list@...hat.com" <libvir-list@...hat.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Linux Containers <containers@...ts.linux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"lxc-devel@...ts.sourceforge.net" <lxc-devel@...ts.sourceforge.net>,
	"davem@...emloft.net" <davem@...emloft.net>
Subject: Re: [systemd-devel] [PATCH] netns: unix: only allow to find out
 unix socket in same net namespace

On Mon, 2013-08-26 at 11:35 +0800, Gao feng wrote:
> On 08/26/2013 11:19 AM, James Bottomley wrote:
> > Yes, we are discussing this problem in this whole thread.

I wasn't really watching that bit, since the problem looks solved to me.
I was just reacting against the unfortunate notion that a container
should run init.

>  If so, OpenVZ
> > has never suffered from that problem and I thought it was fixed
> > upstream.  I've not tested lxc tools, but the latest vzctl from the
> > openvz website will bring up a container on the vanilla 3.9 kernel
> > (provided you have USER_NS compiled in) can also be used to reboot the
> > container, so I see no reason it wouldn't work for lxc as well.
> > 
> 
> I'm using libvirt lxc not lxc-tools.
> Not all of users enable user namespace, I trust these container
> management
> tools can have right/proper setting which inhibit this reboot-problem
> occur.
> but I don't think this reboot-problem won't happen in any
> configuration.

It sounds like you're setting up your containers wrongly.  If a
container can reboot the system it means that host root capabilities
have leaked into the container, which is a big security no-no.  The
upstream way of avoiding this is USER_NS (because root in the container
is now not root in the host).  The OpenVZ kernel uses a different
mechanism to solve the problem, but we think USER_NS is the better way
to go on this.

James

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