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 43BEFC4BA21 for ; Wed, 26 Feb 2020 19:14:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 219952067C for ; Wed, 26 Feb 2020 19:14:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727258AbgBZTO3 (ORCPT ); Wed, 26 Feb 2020 14:14:29 -0500 Received: from correo.us.es ([193.147.175.20]:33608 "EHLO mail.us.es" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727091AbgBZTO2 (ORCPT ); Wed, 26 Feb 2020 14:14:28 -0500 Received: from antivirus1-rhel7.int (unknown [192.168.2.11]) by mail.us.es (Postfix) with ESMTP id ACCACFFB62 for ; Wed, 26 Feb 2020 20:14:19 +0100 (CET) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id 9EA4BDA3A3 for ; Wed, 26 Feb 2020 20:14:19 +0100 (CET) Received: by antivirus1-rhel7.int (Postfix, from userid 99) id 94477DA38F; Wed, 26 Feb 2020 20:14:19 +0100 (CET) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id BAA81DA72F; Wed, 26 Feb 2020 20:14:17 +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 20:14:17 +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 9A6BD42EF42A; Wed, 26 Feb 2020 20:14:17 +0100 (CET) Date: Wed, 26 Feb 2020 20:14:25 +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: <20200226191425.3h2i3rn4xdanzfde@salvia> References: <20200213065352.6310-1-xiyou.wangcong@gmail.com> <20200218213524.5yuccwnl2eie6p6x@salvia> <20200218220507.cqlhd4kj4ukyjhuu@salvia> <20200226181106.ekb2mpmtgbxrpepz@salvia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200226181106.ekb2mpmtgbxrpepz@salvia> 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 26, 2020 at 07:11:06PM +0100, Pablo Neira Ayuso wrote: > 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. Sorry, I meant, applied, thanks.