linux-kernel - plan9 semantics on Linux

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Date:   Tue, 13 Feb 2018 22:12:25 +0000
From:   Enrico Weigelt <lkml@...ux.net>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: plan9 semantics on Linux - mount namespaces

Hi folks,

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 ?

IMHO, we could allow mount/bind under the following conditions:

* the process is in a private mount namespace
* no suid-flag is honored (either force all mounts to nosuid or
   completely mask it out)
* only certain whitelisted filesystems allowed (eg. 9P and FUSE)

Maybe that all could be enabled by a new capability.

any suggestions ?

--mtx

-- 
Enrico Weigelt, metux IT consult
Free software and Linux embedded engineering
info@...ux.net -- +49-151-27565287