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=-5.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 5871CC43387 for ; Sun, 30 Dec 2018 07:45:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1FDDD20866 for ; Sun, 30 Dec 2018 07:45:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1546155922; bh=+ZO2Mv/zKKv8Wxbl9LfAofNAR27leOmCzId2ay0EiMc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=ugVIEPBNT6be9b0iL4t8qd8a2gH/PYoX/wdSUD+gaKli222KFiWAohEIWjgl+GvIR HqBqv/msgEQWxbyJvb89SHX/Q0QxxckJVyH2Ikc2tVq8nta9i2DEwuGkTKqITY33Mm KtGFjXQbvRKSVqBJitgYJL0cQUVZWKoke9KB4iYg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726071AbeL3HpV (ORCPT ); Sun, 30 Dec 2018 02:45:21 -0500 Received: from mx2.suse.de ([195.135.220.15]:35100 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726002AbeL3HpU (ORCPT ); Sun, 30 Dec 2018 02:45:20 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 71746ADC1; Sun, 30 Dec 2018 07:45:18 +0000 (UTC) Date: Sun, 30 Dec 2018 08:45:13 +0100 From: Michal Hocko To: Shakeel Butt Cc: Florian Westphal , Pablo Neira Ayuso , Jozsef Kadlecsik , Roopa Prabhu , Nikolay Aleksandrov , Andrew Morton , Linux MM , netfilter-devel@vger.kernel.org, coreteam@netfilter.org, bridge@lists.linux-foundation.org, LKML , syzbot+7713f3aa67be76b1552c@syzkaller.appspotmail.com Subject: Re: [PATCH] netfilter: account ebt_table_info to kmemcg Message-ID: <20181230074513.GA22445@dhcp22.suse.cz> References: <20181229015524.222741-1-shakeelb@google.com> <20181229073325.GZ16738@dhcp22.suse.cz> <20181229095215.nbcijqacw5b6aho7@breakpoint.cc> <20181229100615.GB16738@dhcp22.suse.cz> 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) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat 29-12-18 11:34:29, Shakeel Butt wrote: > On Sat, Dec 29, 2018 at 2:06 AM Michal Hocko wrote: > > > > On Sat 29-12-18 10:52:15, Florian Westphal wrote: > > > Michal Hocko wrote: > > > > On Fri 28-12-18 17:55:24, Shakeel Butt wrote: > > > > > The [ip,ip6,arp]_tables use x_tables_info internally and the underlying > > > > > memory is already accounted to kmemcg. Do the same for ebtables. The > > > > > syzbot, by using setsockopt(EBT_SO_SET_ENTRIES), was able to OOM the > > > > > whole system from a restricted memcg, a potential DoS. > > > > > > > > What is the lifetime of these objects? Are they bound to any process? > > > > > > No, they are not. > > > They are free'd only when userspace requests it or the netns is > > > destroyed. > > > > Then this is problematic, because the oom killer is not able to > > guarantee the hard limit and so the excessive memory consumption cannot > > be really contained. As a result the memcg will be basically useless > > until somebody tears down the charged objects by other means. The memcg > > oom killer will surely kill all the existing tasks in the cgroup and > > this could somehow reduce the problem. Maybe this is sufficient for > > some usecases but that should be properly analyzed and described in the > > changelog. > > > > Can you explain why you think the memcg hard limit will not be > enforced? From what I understand, the memcg oom-killer will kill the > allocating processes as you have mentioned. We do force charging for > very limited conditions but here the memcg oom-killer will take care > of I was talking about the force charge part. Depending on a specific allocation and its life time this can gradually get us over hard limit without any bound theoretically. > Anyways, the kernel is already charging the memory for > [ip,ip6,arp]_tables and this patch adds the charging for ebtables. > Without this patch, as Kirill has described and shown by syzbot, a low > priority memcg can force system OOM. I am not opposing the patch per-se. I would just like the changelog to be more descriptive about the life time and consequences. -- Michal Hocko SUSE Labs