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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 29830C77B7C for ; Fri, 5 May 2023 13:47:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232425AbjEENrA (ORCPT ); Fri, 5 May 2023 09:47:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37108 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232725AbjEENq7 (ORCPT ); Fri, 5 May 2023 09:46:59 -0400 Received: from Chamillionaire.breakpoint.cc (Chamillionaire.breakpoint.cc [IPv6:2a0a:51c0:0:237:300::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 263B612F for ; Fri, 5 May 2023 06:46:58 -0700 (PDT) Received: from fw by Chamillionaire.breakpoint.cc with local (Exim 4.92) (envelope-from ) id 1puvlv-0006El-P9; Fri, 05 May 2023 15:46:55 +0200 Date: Fri, 5 May 2023 15:46:55 +0200 From: Florian Westphal To: Phil Sutter , Florian Westphal , netfilter-devel@vger.kernel.org Subject: Re: [PATCH nf-next 0/3] netfilter: nf_tables: reject loads from uninitialized registers Message-ID: <20230505134655.GC6126@breakpoint.cc> References: <20230505111656.32238-1-fw@strlen.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org Phil Sutter wrote: > On Fri, May 05, 2023 at 01:16:53PM +0200, Florian Westphal wrote: > > Keep a per-rule bitmask that tracks registers that have seen a store, > > then reject loads when the accessed registers haven't been flagged. > > > > This changes uabi contract, because we previously allowed this. > > Neither nftables nor iptables-nft create such rules. > > Did you consider keeping this bitmask on a per base-chain level? One had > to perform this for each base chain of a table upon each rule change and > traverse the tree of chains jumped to from there. I guess the huge > overhead disqualifies this, though. Yes, but its very hard task, because in that case we also need to prove that a write *WILL* happen, rather than *might happen*. Consider: rule1: ip protocol tcp iifname "eth0" ... reg1 := ip protocol cmp reg1 reg2 := meta iifname rule2: iifname "eth1" ... cmp reg2 "eth0" rule 2 has to be rejected because reg2 might be unitialized for != tcp. Even if we can handle this some way, we now also need to revalidate the ruleset on deletes, because we'd have to detect when a register write we depend on goes away.