From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Hutchings Subject: Re: module loading with CAP_NET_ADMIN Date: Thu, 24 Feb 2011 16:34:25 +0000 Message-ID: <1298565265.2613.16.camel@bwh-desktop> References: <20110224151238.GA16916@albatros> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Kees Cook , Eugene Teo , Dan Rosenberg , "David S. Miller" To: Vasiliy Kulikov Return-path: Received: from exchange.solarflare.com ([216.237.3.220]:20197 "EHLO exchange.solarflare.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754932Ab1BXQe2 (ORCPT ); Thu, 24 Feb 2011 11:34:28 -0500 In-Reply-To: <20110224151238.GA16916@albatros> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, 2011-02-24 at 18:12 +0300, Vasiliy Kulikov wrote: > 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@albatros:~# grep Cap /proc/$$/status > CapInh: 0000000000000000 > CapPrm: fffffffc00001000 > CapEff: fffffffc00001000 > CapBnd: fffffffc00001000 > root@albatros:~# lsmod | grep xfs > root@albatros:~# ifconfig xfs > xfs: error fetching interface information: Device not found > root@albatros:~# lsmod | grep xfs > xfs 767011 0 > exportfs 4226 2 xfs,nfsd Eek! > 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. AFAIK these interface-name aliases are usually defined by distribution configuration files rather than within the modules themselves. And that behaviour is pretty much obsolete now that we have hotplug and udev. > 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. The only modules I can see that declare aliases like this are: net/ipv4/ip_gre.c:MODULE_ALIAS("gre0"); net/ipv4/ipip.c:MODULE_ALIAS("tunl0"); net/ipv6/sit.c:MODULE_ALIAS("sit0"); 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.