linux-kernel - Re: plan9 semantics on Linux

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Message-ID: <20180213222751.p3fyg7whg6jqlzz5@gordon>
Date:   Wed, 14 Feb 2018 09:27:51 +1100
From:   Aleksa Sarai <asarai@...e.de>
To:     Enrico Weigelt <lkml@...ux.net>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Linux Containers <containers@...ts.linux-foundation.org>
Subject: Re: plan9 semantics on Linux - mount namespaces

On 2018-02-13, Enrico Weigelt <lkml@...ux.net> wrote:
> On 13.02.2018 22:12, Enrico Weigelt wrote:
> > I'm currently trying to implement plan9 semantics on Linux and
> > yet sorting out how to do the mount namespace handling.
> > 
> > On plan9, any unprivileged process can create its own namespace
> > and mount/bind at will, while on Linux this requires CAP_SYS_ADMIN.
> > 
> > What is the reason for not allowing arbitrary users to create their
> > own private mount namespace ? What could go wrong here ?

You can do this by creating a new user namespace (CLONE_NEWUSER), which
then gives you the required permissions to create other namespaces
(CLONE_NEWNS). This is how "rootless containers" or unprivileged
containers operate.

-- 
Aleksa Sarai
Senior Software Engineer (Containers)
SUSE Linux GmbH
<https://www.cyphar.com/>

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