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 ED4A6C43612 for ; Mon, 31 Dec 2018 10:12:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BAC4D2177E for ; Mon, 31 Dec 2018 10:12:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1546251125; bh=K6+Ag34XZcqq22UwxSAgbyXxYDLXtLye8bgwAHMYi94=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=TBGzF1GG3n7traseR55xDYEJ7CdOld5nfnXAiPVU52nkmCW8Q8WevzUiHP0hAXmT0 Rez4eCM2aD5UydcvnJKoxki9XeDTfpNWO53cJsgK1wybcuCMMbzxkTAWe13ZMoLsst rKNgR2jDpaa0actcGIVe5EG++lz9bEx8P/p2uU40= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727204AbeLaKME (ORCPT ); Mon, 31 Dec 2018 05:12:04 -0500 Received: from mx2.suse.de ([195.135.220.15]:46100 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727078AbeLaKMD (ORCPT ); Mon, 31 Dec 2018 05:12:03 -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 AD834ADF4; Mon, 31 Dec 2018 10:12:00 +0000 (UTC) Date: Mon, 31 Dec 2018 11:11:58 +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: <20181231101158.GC22445@dhcp22.suse.cz> References: <20181229015524.222741-1-shakeelb@google.com> <20181229073325.GZ16738@dhcp22.suse.cz> <20181229095215.nbcijqacw5b6aho7@breakpoint.cc> <20181229100615.GB16738@dhcp22.suse.cz> <20181230074513.GA22445@dhcp22.suse.cz> <20181230080028.GB22445@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 Sun 30-12-18 19:59:53, Shakeel Butt wrote: > On Sun, Dec 30, 2018 at 12:00 AM Michal Hocko wrote: > > > > On Sun 30-12-18 08:45:13, Michal Hocko wrote: > > > 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. > > > > Forgot to mention. Since b8c8a338f75e ("Revert "vmalloc: back off when > > the current task is killed"") there is no way to bail out from the > > vmalloc allocation loop so if the request is really large then the memcg > > oom will not help. Is that a problem here? > > > > Yes, I think it will be an issue here. > > > Maybe it is time to revisit fatal_signal_pending check. > > Yes, we will need something to handle the memcg OOM. I will think more > on that front or if you have any ideas, please do propose. I can see three options here: - do not force charge on memcg oom or introduce a limited charge overflow (reserves basically). - revert the revert and reintroduce the fatal_signal_pending check into vmalloc - be more specific and check tsk_is_oom_victim in vmalloc and fail -- Michal Hocko SUSE Labs