linux-kernel - Re: For review: user

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Message-ID: <CAFLxGvzXkGcR=Wyx8YZKKRACEnNLMA0xQoDfruq7CT1D-FNLnA@mail.gmail.com>
Date:	Mon, 29 Apr 2013 09:45:45 +0200
From:	richard -rw- weinberger <richard.weinberger@...il.com>
To:	Michael Kerrisk-manpages <mtk.manpages@...il.com>
Cc:	Serge Hallyn <serge.hallyn@...ntu.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-man <linux-man@...r.kernel.org>,
	Linux Containers <containers@...ts.linux-foundation.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Vasily Kulikov <segoon@...nwall.com>
Subject: Re: For review: user_namespaces(7) man page

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.

Thanks,
//richard
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