linux-kernel - Re: For review: user

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Message-ID: <CAFLxGvw0HObP6kQM8mmp58wbx3ua5oVm2-N9J-kfAsHvddpcgg@mail.gmail.com>
Date:	Mon, 29 Apr 2013 22:35:13 +0200
From:	richard -rw- weinberger <richard.weinberger@...il.com>
To:	Rob Landley <rob@...dley.net>
Cc:	Michael Kerrisk-manpages <mtk.manpages@...il.com>,
	linux-man <linux-man@...r.kernel.org>,
	Linux Containers <containers@...ts.linux-foundation.org>,
	Serge Hallyn <serge.hallyn@...ntu.com>,
	lkml <linux-kernel@...r.kernel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Vasily Kulikov <segoon@...nwall.com>
Subject: Re: For review: user_namespaces(7) man page

On Mon, Apr 29, 2013 at 9:45 PM, Rob Landley <rob@...dley.net> wrote:
> On 04/29/2013 02:45:45 AM, richard -rw- weinberger wrote:
>>
>> On Thu, Mar 21, 2013 at 4:52 PM, Michael Kerrisk (man-pages)
>> <mtk.manpages@...il.com> wrote:
>> > Hi Serge,
>> >
>> > On Fri, Mar 15, 2013 at 4:38 PM, Serge Hallyn <serge.hallyn@...ntu.com>
>> > wrote:
>> >> Hi,
>> >>
>> >> you mention that after creating a new user namespace you at first have
>> >> all capabilities in the new ns.  You don't explicitly mention (or I
>> >> missed it - I did see the mention of securebits) that if you want to
>> >> keep those capabilities after doing an exec, you need to first have
>> >> something mapped to uid 0 in the userns, and do setuid(0).
>> >
>> > Good point. I'll add something on that.
>> >
>> >> You might not want to list manpages from other projects,
>> >
>> > Actually, not a problem. Many of the pages in my set already do this.
>> >
>> >> but Eric's
>> >> shadow patches introduce some good new manpages as well.  Those aren't
>> >> yet
>> >> accepted upstream, but if/when they are then mention at least of
>> >> subuid(5), subgid(5), and newuidmap(1) and newgidmap(1) might be good.
>> >
>> > I'll add those.
>> >
>> > Cheers,
>> >
>> > Michael
>>
>> Can we please also document which capabilities are useless within an
>> user namespace?
>> E.g. CAP_MKNOD.
>> You get this capability but the kernel always checks it against the
>> initial userns.
>
>
> Is there a device namespace?
>

Not really, but you can limit device access via a cgroup device controller.

--
Thanks,
//richard
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