From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754641AbeBUOyH (ORCPT ); Wed, 21 Feb 2018 09:54:07 -0500 Received: from mail-eopbgr00127.outbound.protection.outlook.com ([40.107.0.127]:39168 "EHLO EUR02-AM5-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753161AbeBUOyE (ORCPT ); Wed, 21 Feb 2018 09:54:04 -0500 Authentication-Results: spf=none (sender IP is ) smtp.mailfrom=tommi.t.rantala@nokia.com; Subject: Re: net: hang in unregister_netdevice: waiting for lo to become free To: Neil Horman , Dmitry Vyukov Cc: Xin Long , David Ahern , Daniel Borkmann , Cong Wang , David Miller , Eric Dumazet , Willem de Bruijn , Jakub Kicinski , Rasmus Villemoes , netdev , LKML , Alexey Kuznetsov , Hideaki YOSHIFUJI , syzkaller , Dan Streetman , "Eric W. Biederman" , Alexey Kodanev , Marcelo Ricardo Leitner , linux-sctp@vger.kernel.org References: <7fd7e3b3-77b1-0936-b169-d08b946bedc7@iogearbox.net> <991243e2-e7c2-f2b2-72b9-d37b0d569b3b@gmail.com> <5973966e-fcd9-7ee5-a9c4-b79d22c1b9dd@nokia.com> <20180220162622.GA32068@hmswarspite.think-freely.org> From: Tommi Rantala Message-ID: <7d98027d-e810-a079-49c5-0bf8beef390e@nokia.com> Date: Wed, 21 Feb 2018 16:53:54 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180220162622.GA32068@hmswarspite.think-freely.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [131.228.32.176] X-ClientProxiedBy: AM5PR0701CA0015.eurprd07.prod.outlook.com (2603:10a6:203:51::25) To DB5PR07MB1319.eurprd07.prod.outlook.com (2a01:111:e400:599b::13) X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-HT: Tenant X-MS-Office365-Filtering-Correlation-Id: 73cb5af3-2928-4a37-4acc-08d5793af0ed X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(48565401081)(4534165)(4627221)(201703031133081)(201702281549075)(5600026)(4604075)(2017052603307)(7193020);SRVR:DB5PR07MB1319; 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I am still seeing this on the >>>> latest upstream tree. >>>> >>> >>> These two commits are in v4.16-rc1: >>> >>> commit 4a31a6b19f9ddf498c81f5c9b089742b7472a6f8 >>> Author: Tommi Rantala >>> Date: Mon Feb 5 21:48:14 2018 +0200 >>> >>> sctp: fix dst refcnt leak in sctp_v4_get_dst >>> ... >>> Fixes: 410f03831 ("sctp: add routing output fallback") >>> Fixes: 0ca50d12f ("sctp: fix src address selection if using secondary >>> addresses") >>> >>> >>> commit 957d761cf91cdbb175ad7d8f5472336a4d54dbf2 >>> Author: Alexey Kodanev >>> Date: Mon Feb 5 15:10:35 2018 +0300 >>> >>> sctp: fix dst refcnt leak in sctp_v6_get_dst() >>> ... >>> Fixes: dbc2b5e9a09e ("sctp: fix src address selection if using secondary >>> addresses for ipv6") >>> >>> >>> I guess we missed something if it's still reproducible. >>> >>> I can check it later this week, unless someone else beat me to it. >> >> Hi Tommi, >> >> Hmmm, I can't claim that it's exactly the same bug. Perhaps it's >> another one then. But I am still seeing these: >> >> [ 58.799130] unregister_netdevice: waiting for lo to become free. >> Usage count = 4 >> [ 60.847138] unregister_netdevice: waiting for lo to become free. >> Usage count = 4 >> [ 62.895093] unregister_netdevice: waiting for lo to become free. >> Usage count = 4 >> [ 64.943103] unregister_netdevice: waiting for lo to become free. >> Usage count = 4 >> >> on upstream tree pulled ~12 hours ago. >> > Can you write a systemtap script to probe dev_hold, and dev_put, printing out a > backtrace if the device name matches "lo". That should tell us definitively if > the problem is in the same location or not Hi Dmitry, I tested with the reproducer and the kernel .config file that you sent in the first email in this thread: With 4.16-rc2 unable to reproduce. With 4.15-rc9 bug reproducible, and I get "unregister_netdevice: waiting for lo to become free. Usage count = 3" With 4.15-rc9 and Alexey's "sctp: fix dst refcnt leak in sctp_v6_get_dst()" cherry-picked on top, unable to reproduce. Is syzkaller doing something else now to trigger the bug...? Can you still trigger the bug with the same reproducer? Tommi