Subject: Re: [PATCH] don't allow CAP_NET_ADMIN to load non-netdev kernel
 modules
From: Ben Hutchings <bhutchings@solarflare.com>
To: David Miller <davem@davemloft.net>
Cc: segoon@openwall.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        kuznet@ms2.inr.ac.ru, pekkas@netcore.fi, jmorris@namei.org,
        yoshfuji@linux-ipv6.org, kaber@trash.net, eric.dumazet@gmail.com,
        therbert@google.com, xiaosuo@gmail.com, jesse@nicira.com,
        kees.cook@canonical.com, eugene@redhat.com, dan.j.rosenberg@gmail.com,
        akpm@linux-foundation.org
In-Reply-To: <20110225.110529.39178636.davem@davemloft.net>
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	 <20110225190205.GA4541@albatros>
	 <20110225.110529.39178636.davem@davemloft.net>
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Organization: Solarflare Communications
Date: Fri, 25 Feb 2011 19:07:59 +0000
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On Fri, 2011-02-25 at 11:05 -0800, David Miller wrote:
> From: Vasiliy Kulikov <segoon@openwall.com>
> Date: Fri, 25 Feb 2011 22:02:05 +0300
> 
> > On Fri, Feb 25, 2011 at 10:47 -0800, David Miller wrote:
> >> From: Vasiliy Kulikov <segoon@openwall.com>
> >> Date: Fri, 25 Feb 2011 18:14:14 +0300
> >> 
> >> > Since a8f80e8ff94ecba629542d9b4b5f5a8ee3eb565c any process with
> >> > CAP_NET_ADMIN may load any module from /lib/modules/.  This doesn't mean
> >> > that CAP_NET_ADMIN is a superset of CAP_SYS_MODULE as modules are limited
> >> > to /lib/modules/**.  However, CAP_NET_ADMIN capability shouldn't allow
> >> > anybody load any module not related to networking.
> >> 
> >> Why go through this naming change, which does break things, instead of
> >> simply adding a capability mask tag or similar to modules somehow.  You
> >> could stick it into a special elf section or similar.
> >>
> >> Doesn't that make tons more sense than this?
> > 
> > This is not "simply", adding special section for a single workaround
> > seems like an overkill for me - this touches the core (modules'
> > internals), which is not related to the initial CAP_* problem at all.
> > 
> > I'd be happy with not breaking anything, but I don't see any acceptable
> > solution.
> 
> I think it's warranted given that it allows us to avoid breaking things.
> 
> I don't understand there is resistence in response to the first idea
> I've seen proprosed that actually allows to fix the problem and not
> break anything at the same time.
> 
> That seems silly.

You realise that module loading doesn't actually run in the context of
request_module(), right?

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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