linux-kernel - Re: Thoughts on tightening up user namespace creation

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Message-ID: <20160308224116.GA17693@mail.hallyn.com>
Date:	Tue, 8 Mar 2016 16:41:16 -0600
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Serge Hallyn <serge.hallyn@...ntu.com>,
	Kees Cook <keescook@...omium.org>,
	Colin Walters <walters@...bum.org>,
	Linux Containers <containers@...ts.linux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Seth Forshee <seth.forshee@...onical.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Stephane Graber <stgraber@...ntu.com>
Subject: Re: Thoughts on tightening up user namespace creation

Quoting Andy Lutomirski (luto@...capital.net):
> On Mar 7, 2016 10:06 PM, "Serge E. Hallyn" <serge.hallyn@...ntu.com> wrote:
> >
> > On Mon, Mar 07, 2016 at 09:15:25PM -0800, Andy Lutomirski wrote:
> > >  - Ubuntu requires CAP_SYS_ADMIN
> >
> > No, it does not.  It has temporarily re-added a sysctl which can enable
> > that behavior, but it's not set by default.  The reason for providing it
> > is not a distrust of user namespaces in general, but because we're enabling
> > some bleeding edge patches which haven't been accepted upstream yet.  Once
> > they're accepted upstream I expect that patch to be dropped again, unless
> > it has gone upstream.
> >
> > Debian does afaik still have a version of a patch I'd originally written
> > before user namespaces were upstream which defaulted unprivileged userns
> > cloning to off.  Did you mean Debian here?
> 
> I meant Ubuntu 14.04, which I tested, possibly poorly.

Weird, 14.04 with the default kernel (3.13.0-79-generic #123-Ubuntu)
doesn't have the sysctl at all.

-serge