netdev - [PATCH 0/2] Fix /proc/net in presence of net namespaces

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Date:	Thu, 28 Feb 2008 18:46:11 +0300
From:	Pavel Emelyanov <xemul@...nvz.org>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	David Miller <davem@...emloft.net>
CC:	Alexey Dobriyan <adobriyan@...nvz.org>,
	Linux Netdev List <netdev@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: [PATCH 0/2] Fix /proc/net in presence of net namespaces

Current /proc/net is done with so called "shadows", but current
implementation is broken and has little chances to get fixed.

The problem is that dentries subtree of /proc/net directory has
fancy revalidation rules to make processes living in different
net namespaces see different entries in /proc/net subtree, but
currently, tasks see in the /proc/net subdir the contents of any
other namespace, depending on who opened the file first.

The proposed fix is to turn /proc/net into a symlink, which behaves
similar to /proc/self link - it points to .netns/<id> directory 
where the <id> is the id of net namespace, current task lives in.

# ls -l /proc/net
lrwxrwxrwx  1 root root 8 Feb 28 18:38 /proc/net -> .netns/0

The /proc/.netns dir contains subtrees for all the namespaces in 
the system:

# ls -l /proc/.netns/
total 0
dr-xr-xr-x  5 root root 0 Feb 28 18:39 0
dr-xr-xr-x  3 root root 0 Feb 28 18:39 1

To provide some security each /proc/.netns/<id> directory allows
access to tasks that live in the owning namespace only (with the
exception, that init_net tasks can see everything).

Signed-off-by: Pavel Emelyanov <xemul@...nvz.org>
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