linux-kernel - Re: request_module vs. modprobe blacklist (and security subsystem implications)

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Message-ID: <m14opss03d.fsf@fess.ebiederm.org>
Date:	Wed, 21 Oct 2009 18:12:38 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Eric Paris <eparis@...hat.com>
Cc:	linux-kernel@...r.kernel.org, arjan@...radead.org,
	randy.dunlap@...cle.com, rusty@...tcorp.com.au,
	andi@...stfloor.org, dhowells@...hat.com, akpm@...ux-foundation.org
Subject: Re: request_module vs. modprobe blacklist (and security subsystem implications)

Eric Paris <eparis@...hat.com> writes:

> I recently added a new LSM hook into __request_module(),
> security_kernel_module_request().  This new hook checks if a process
> should have permission to trigger the loading of a kernel module.  The
> attack vector imagined was that some module (IPX for example) has a
> vulnerability.  An attack program (which doesn't have permission to load
> the IPX module directly) might be able to get the networking stack to
> try to autoload the module.  Once loaded the attack program could then
> use the larger surface area to exploit the kernel.
>
> We have found that many users disable the IPv6 module by setting their
> modprobe config to look like:
>
> blacklist ipv6
> install ipv6 /bin/true

They need to be using /proc/sys/net/ipv6/conf/*/disable_ipv6 instead.
As the above scenario keeps the bonding driver from loading.

Eric
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