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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 274D1C433DF for ; Tue, 13 Oct 2020 10:15:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C2F0F20708 for ; Tue, 13 Oct 2020 10:15:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727894AbgJMKPI (ORCPT ); Tue, 13 Oct 2020 06:15:08 -0400 Received: from correo.us.es ([193.147.175.20]:52016 "EHLO mail.us.es" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726935AbgJMKPI (ORCPT ); Tue, 13 Oct 2020 06:15:08 -0400 Received: from antivirus1-rhel7.int (unknown [192.168.2.11]) by mail.us.es (Postfix) with ESMTP id 28DEF1C4381 for ; Tue, 13 Oct 2020 12:15:06 +0200 (CEST) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id 03430DA872 for ; Tue, 13 Oct 2020 12:15:06 +0200 (CEST) Received: by antivirus1-rhel7.int (Postfix, from userid 99) id EAEE8DA791; Tue, 13 Oct 2020 12:15:05 +0200 (CEST) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id D67D8DA793; Tue, 13 Oct 2020 12:15:02 +0200 (CEST) Received: from 192.168.1.97 (192.168.1.97) by antivirus1-rhel7.int (F-Secure/fsigk_smtp/550/antivirus1-rhel7.int); Tue, 13 Oct 2020 12:14:55 +0200 (CEST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/antivirus1-rhel7.int) Received: from us.es (unknown [90.77.255.23]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: 1984lsi) by entrada.int (Postfix) with ESMTPSA id AB9A942EF532; Tue, 13 Oct 2020 12:15:02 +0200 (CEST) Date: Tue, 13 Oct 2020 12:15:02 +0200 X-SMTPAUTHUS: auth mail.us.es From: Pablo Neira Ayuso To: Phil Sutter , netfilter-devel@vger.kernel.org, Florian Westphal Subject: Re: [iptables PATCH 3/3] nft: Fix for concurrent noflush restore calls Message-ID: <20201013101502.GA29142@salvia> References: <20201005144858.11578-1-phil@nwl.cc> <20201005144858.11578-4-phil@nwl.cc> <20201012125450.GA26934@salvia> <20201013100803.GW13016@orbyte.nwl.cc> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20201013100803.GW13016@orbyte.nwl.cc> User-Agent: Mutt/1.10.1 (2018-07-13) X-Virus-Scanned: ClamAV using ClamSMTP Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org On Tue, Oct 13, 2020 at 12:08:03PM +0200, Phil Sutter wrote: [...] > On Mon, Oct 12, 2020 at 02:54:50PM +0200, Pablo Neira Ayuso wrote: > [...] > > Patch LGTM, thanks Phil. > > > > What I don't clearly see yet is what scenario is triggering the bug in > > the existing code, if you don't mind to explain. > > See the test case attached to the patch: An other iptables-restore > process may add references (i.e., jumps) to a chain the own > iptables-restore process wants to delete. This should not be a problem > because these references are added to a chain that is being flushed by > the own process as well. But if that chain doesn't exist while the own > process fetches kernel's ruleset, this flush job is not created. Let me rephrase this: 1) process A fetches the ruleset, finds no chain C (no flush job then) 2) process B adds new chain C, flush job is present 3) process B adds the ruleset 4) process A appends rules to the existing chain C (because there is no flush job) Is this the scenario? If so, I wonder why the generation ID is not helping to refresh and retry.