From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B4A2BC3A59D for ; Thu, 22 Aug 2019 03:54:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 923752173E for ; Thu, 22 Aug 2019 03:54:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730459AbfHVDyz (ORCPT ); Wed, 21 Aug 2019 23:54:55 -0400 Received: from shards.monkeyblade.net ([23.128.96.9]:37896 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728788AbfHVDyz (ORCPT ); Wed, 21 Aug 2019 23:54:55 -0400 Received: from localhost (unknown [IPv6:2601:601:9f80:35cd::d71]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) (Authenticated sender: davem-davemloft) by shards.monkeyblade.net (Postfix) with ESMTPSA id 89ED61522471F; Wed, 21 Aug 2019 20:54:54 -0700 (PDT) Date: Wed, 21 Aug 2019 20:54:54 -0700 (PDT) Message-Id: <20190821.205454.2103510420957943248.davem@davemloft.net> To: paul@paul-moore.com Cc: netdev@vger.kernel.org, linux-security-module@vger.kernel.org, selinux@vger.kernel.org Subject: Re: New skb extension for use by LSMs (skb "security blob")? From: David Miller In-Reply-To: References: <20190821.155013.1723892743521935274.davem@davemloft.net> X-Mailer: Mew version 6.8 on Emacs 26.1 Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Wed, 21 Aug 2019 20:54:54 -0700 (PDT) Sender: selinux-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: selinux@vger.kernel.org From: Paul Moore Date: Wed, 21 Aug 2019 23:27:03 -0400 > On Wed, Aug 21, 2019 at 6:50 PM David Miller wrote: >> From: Paul Moore >> Date: Wed, 21 Aug 2019 18:00:09 -0400 >> >> > I was just made aware of the skb extension work, and it looks very >> > appealing from a LSM perspective. As some of you probably remember, >> > we (the LSM folks) have wanted a proper security blob in the skb for >> > quite some time, but netdev has been resistant to this idea thus far. >> > >> > If I were to propose a patchset to add a SKB_EXT_SECURITY skb >> > extension (a single extension ID to be shared among the different >> > LSMs), would that be something that netdev would consider merging, or >> > is there still a philosophical objection to things like this? >> >> Unlike it's main intended user (MPTCP), it sounds like LSM's would use >> this in a way such that it would be enabled on most systems all the >> time. >> >> That really defeats the whole purpose of making it dynamic. :-/ > > I would be okay with only adding a skb extension when we needed it, > which I'm currently thinking would only be when we had labeled > networking actually configured at runtime and not just built into the > kernel. In SELinux we do something similar today when it comes to our > per-packet access controls; if labeled networking is not configured we > bail out of the LSM hooks early to improve performance (we would just > be comparing unlabeled_t to unlabeled_t anyway). I think the other > LSMs would be okay with this usage as well. > > While a number of distros due enable some form of LSM and the labeled > networking bits at build time, vary few (if any?) provide a default > configuration so I would expect no additional overhead in the common > case. > > Would that be acceptable? I honestly don't know, I kinda feared that once the SKB extension went in people would start dumping things there and that's exactly what's happening. I just so happened to be reviewing: https://patchwork.ozlabs.org/patch/1150091/ while you were writing this email. It's rediculous, the vultures are out.