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

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Date:	Fri, 30 May 2008 18:59:26 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Stephen Hemminger <shemminger@...tta.com>
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

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
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