linux-kernel - module loading with CAP_NET

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Message-ID: <20110224151238.GA16916@albatros>
Date:	Thu, 24 Feb 2011 18:12:38 +0300
From:	Vasiliy Kulikov <segoon@...nwall.com>
To:	netdev@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Kees Cook <kees.cook@...onical.com>,
	Eugene Teo <eugene@...hat.com>,
	Dan Rosenberg <dan.j.rosenberg@...il.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: module loading with CAP_NET_ADMIN

Hi netdev folks,

I'd like to discuss the ability to load any modules from /lib/modules/
by a process with CAP_NET_ADMIN.  Since Linux 2.6.32 [1] there is such
possibility:

root@...atros:~# grep Cap /proc/$$/status
CapInh: 0000000000000000
CapPrm: fffffffc00001000
CapEff: fffffffc00001000
CapBnd: fffffffc00001000
root@...atros:~# lsmod | grep xfs
root@...atros:~# ifconfig xfs
xfs: error fetching interface information: Device not found
root@...atros:~# lsmod | grep xfs
xfs                   767011  0 
exportfs                4226  2 xfs,nfsd

Ability of CAP_NET_ADMIN to load the driver to work with a particular
network device is rational;  however, one may load any module not even
related to network this way.  Hopefully, this is not equal to
CAP_SYS_MODULE since the module set is restricted to /lib/modules
(additionally may be disabled with /proc/sys/kernel/modules_disabled),
but the idea of non-netdev module loading is weird.

My proposal is changing request_module("%s", name) to something like
request_module("netdev-%s", name) inside of dev_load() and adding
aliases to related drivers.  This would allow to load only netdev
modules via these ioctls.  I'm not sure what modules should be patches -
at least real physical netdevices have names different from drivers'
names, so they don't need patching.  I suppose the list is not big.

Any comments are welcome.

[1] http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=a8f80e8ff94ecba629542d9b4b5f5a8ee3eb565c

Thanks,

-- 
Vasiliy Kulikov
http://www.openwall.com - bringing security into open computing environments
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