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=-2.3 required=3.0 tests=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 0940AC4BA18 for ; Wed, 26 Feb 2020 18:11:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DD41F24650 for ; Wed, 26 Feb 2020 18:11:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726907AbgBZSLM (ORCPT ); Wed, 26 Feb 2020 13:11:12 -0500 Received: from correo.us.es ([193.147.175.20]:34416 "EHLO mail.us.es" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726880AbgBZSLL (ORCPT ); Wed, 26 Feb 2020 13:11:11 -0500 Received: from antivirus1-rhel7.int (unknown [192.168.2.11]) by mail.us.es (Postfix) with ESMTP id 9D9E3EB911 for ; Wed, 26 Feb 2020 19:11:01 +0100 (CET) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id 8ECD5DA736 for ; Wed, 26 Feb 2020 19:11:01 +0100 (CET) Received: by antivirus1-rhel7.int (Postfix, from userid 99) id 83ADCDA840; Wed, 26 Feb 2020 19:11:01 +0100 (CET) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id 8BD7ADA736; Wed, 26 Feb 2020 19:10:59 +0100 (CET) Received: from 192.168.1.97 (192.168.1.97) by antivirus1-rhel7.int (F-Secure/fsigk_smtp/550/antivirus1-rhel7.int); Wed, 26 Feb 2020 19:10:59 +0100 (CET) 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 6E0EC42EF42B; Wed, 26 Feb 2020 19:10:59 +0100 (CET) Date: Wed, 26 Feb 2020 19:11:06 +0100 X-SMTPAUTHUS: auth mail.us.es From: Pablo Neira Ayuso To: Cong Wang Cc: Linux Kernel Network Developers , Florian Westphal , NetFilter , syzbot Subject: Re: [Patch nf] netfilter: xt_hashlimit: unregister proc file before releasing mutex Message-ID: <20200226181106.ekb2mpmtgbxrpepz@salvia> References: <20200213065352.6310-1-xiyou.wangcong@gmail.com> <20200218213524.5yuccwnl2eie6p6x@salvia> <20200218220507.cqlhd4kj4ukyjhuu@salvia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170113 (1.7.2) X-Virus-Scanned: ClamAV using ClamSMTP Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, Feb 19, 2020 at 07:32:13PM -0800, Cong Wang wrote: > On Tue, Feb 18, 2020 at 2:05 PM Pablo Neira Ayuso wrote: > > > > On Tue, Feb 18, 2020 at 01:40:26PM -0800, Cong Wang wrote: > > > On Tue, Feb 18, 2020 at 1:35 PM Pablo Neira Ayuso wrote: > > > > > > > > On Wed, Feb 12, 2020 at 10:53:52PM -0800, Cong Wang wrote: > > > > > Before releasing the global mutex, we only unlink the hashtable > > > > > from the hash list, its proc file is still not unregistered at > > > > > this point. So syzbot could trigger a race condition where a > > > > > parallel htable_create() could register the same file immediately > > > > > after the mutex is released. > > > > > > > > > > Move htable_remove_proc_entry() back to mutex protection to > > > > > fix this. And, fold htable_destroy() into htable_put() to make > > > > > the code slightly easier to understand. > > > > > > > > Probably revert previous one? > > > > > > The hung task could appear again if we move the cleanup > > > back under mutex. > > > > How could the hung task appear again by reverting > > c4a3922d2d20c710f827? Please elaborate. > > Because the cfg.max could be as large as 8*HASHLIMIT_MAX_SIZE: > > 311 if (hinfo->cfg.max == 0) > 312 hinfo->cfg.max = 8 * hinfo->cfg.size; > 313 else if (hinfo->cfg.max < hinfo->cfg.size) > 314 hinfo->cfg.max = hinfo->cfg.size; > > Not sure whether we can finish cleaning up 8*HASHLIMIT_MAX_SIZE > entries within the time a hung task tolerates. This largely depends on > how much contention the spinlock has, at least I don't want to bet > on it. Please, resend. Thanks.