netdev - Re: [PATCH] don't allow CAP_NET_ADMIN to load non-netdev kernel modules

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Date:	Fri, 25 Feb 2011 19:30:16 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	David Miller <davem@...emloft.net>
Cc:	segoon@...nwall.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, kuznet@....inr.ac.ru,
	pekkas@...core.fi, jmorris@...ei.org, yoshfuji@...ux-ipv6.org,
	kaber@...sh.net, eric.dumazet@...il.com, therbert@...gle.com,
	xiaosuo@...il.com, jesse@...ira.com, kees.cook@...onical.com,
	eugene@...hat.com, dan.j.rosenberg@...il.com,
	akpm@...ux-foundation.org
Subject: Re: [PATCH] don't allow CAP_NET_ADMIN to load non-netdev kernel
 modules

On Fri, 2011-02-25 at 11:16 -0800, David Miller wrote:
> From: Ben Hutchings <bhutchings@...arflare.com>
> Date: Fri, 25 Feb 2011 19:07:59 +0000
> 
> > You realise that module loading doesn't actually run in the context of
> > request_module(), right?
> 
> Why is that a barrier?  We could simply pass a capability mask into
> request_module if necessary.
> 
> It's an implementation detail, and not a deterrant to my suggested
> scheme.

It's not an implementation detail.  modprobe currently runs with full
capabilities; your proposal requires its capabilities to be limited to
those of the capabilities of the process that triggered the
request_module() (plus, presumably, CAP_SYS_MODULE).

Now modprobe doesn't have CAP_DAC_OVERRIDE and can't read modprobe
configuration files that belong to users other than root.

It doesn't have CAP_SYS_MKNOD so it can't run hooks that call mknod.

etc.

Ben.

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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