linux-kernel - Re: [PATCH] sysctl: allow override of /proc/sys/net with CAP_NET

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Message-ID: <20080530191053.34182eaf@extreme>
Date:	Fri, 30 May 2008 19:10:53 -0700
From:	Stephen Hemminger <shemminger@...tta.com>
To:	ebiederm@...ssion.com (Eric W. Biederman)
Cc:	akpm@...uxfoundation.org, Chris Wright <chrisw@...s-sol.org>,
	stephen.hemminger@...tta.com, adobriyan@...il.com,
	morgan@...nel.org, xemul@...nvz.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: [PATCH] sysctl: allow override of /proc/sys/net with
 CAP_NET_ADMIN

On Fri, 30 May 2008 18:59:26 -0700
ebiederm@...ssion.com (Eric W. Biederman) wrote:

> Stephen Hemminger <shemminger@...tta.com> writes:
> 
> > Extend the permission check for networking sysctl's to allow
> > modification when current process has CAP_NET_ADMIN capability and
> > is not root. This version uses the until now unused permissions hook
> > to override the mode value for /proc/sys/net if accessed by a user
> > with capabilities.
> 
> Looks reasonable but a little incomplete.
> 
> Could you modify register_net_sysctl_table to set this attribute?
> Or alternatively all of the tables registered with register_net_sysctl.
> 
> Otherwise I this will not affect all of the sysctls under
> /proc/sys/net.  Which appears to be your intent.
> 
> > Found while working with Quagga. It is impossible to turn forwarding
> > on/off through the command interface because Quagga uses secure coding
> > practice of dropping privledges during initialization and only raising
> > via capabilities when necessary. Since the dameon has reset real/effective
> > uid after initialization, all attempts to access /proc/sys/net variables
> > will fail. 
> 
> Eric

Unnecessary, it is a property of the root, and there is only one call to register_sysctl_root
in the current code, and that registers the net_sysctl_root structure.
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