Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755697AbcCBBkJ (ORCPT ); Tue, 1 Mar 2016 20:40:09 -0500 Received: from mail177-1.suw61.mandrillapp.com ([198.2.177.1]:23733 "EHLO mail177-1.suw61.mandrillapp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755168AbcCAXyO (ORCPT ); Tue, 1 Mar 2016 18:54:14 -0500 From: Greg Kroah-Hartman Subject: [PATCH 4.4 017/342] ipv6: addrconf: Fix recursive spin lock call X-Mailer: git-send-email 2.7.2 To: Cc: Greg Kroah-Hartman , , Eric Dumazet , Erik Kline , Hannes Frederic Sowa , Subash Abhinov Kasiviswanathan , "David S. Miller" Message-Id: <20160301234528.533409488@linuxfoundation.org> In-Reply-To: <20160301234527.990448862@linuxfoundation.org> References: <20160301234527.990448862@linuxfoundation.org> X-Report-Abuse: Please forward a copy of this message, including all headers, to abuse@mandrill.com X-Report-Abuse: You can also report abuse here: http://mandrillapp.com/contact/abuse?id=30481620.e851d437203442edb376605407763c05 X-Mandrill-User: md_30481620 Date: Tue, 01 Mar 2016 23:53:49 +0000 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2736 Lines: 78 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: "subashab@codeaurora.org" [ Upstream commit 16186a82de1fdd868255448274e64ae2616e2640 ] A rcu stall with the following backtrace was seen on a system with forwarding, optimistic_dad and use_optimistic set. To reproduce, set these flags and allow ipv6 autoconf. This occurs because the device write_lock is acquired while already holding the read_lock. Back trace below - INFO: rcu_preempt self-detected stall on CPU { 1} (t=2100 jiffies g=3992 c=3991 q=4471) <6> Task dump for CPU 1: <2> kworker/1:0 R running task 12168 15 2 0x00000002 <2> Workqueue: ipv6_addrconf addrconf_dad_work <6> Call trace: <2> [] el1_irq+0x68/0xdc <2> [] _raw_write_lock_bh+0x20/0x30 <2> [] __ipv6_dev_ac_inc+0x64/0x1b4 <2> [] addrconf_join_anycast+0x9c/0xc4 <2> [] __ipv6_ifa_notify+0x160/0x29c <2> [] ipv6_ifa_notify+0x50/0x70 <2> [] addrconf_dad_work+0x314/0x334 <2> [] process_one_work+0x244/0x3fc <2> [] worker_thread+0x2f8/0x418 <2> [] kthread+0xe0/0xec v2: do addrconf_dad_kick inside read lock and then acquire write lock for ipv6_ifa_notify as suggested by Eric Fixes: 7fd2561e4ebdd ("net: ipv6: Add a sysctl to make optimistic addresses useful candidates") Cc: Eric Dumazet Cc: Erik Kline Cc: Hannes Frederic Sowa Signed-off-by: Subash Abhinov Kasiviswanathan Acked-by: Hannes Frederic Sowa Acked-by: Eric Dumazet Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv6/addrconf.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -3506,6 +3506,7 @@ static void addrconf_dad_begin(struct in { struct inet6_dev *idev = ifp->idev; struct net_device *dev = idev->dev; + bool notify = false; addrconf_join_solict(dev, &ifp->addr); @@ -3551,7 +3552,7 @@ static void addrconf_dad_begin(struct in /* Because optimistic nodes can use this address, * notify listeners. If DAD fails, RTM_DELADDR is sent. */ - ipv6_ifa_notify(RTM_NEWADDR, ifp); + notify = true; } } @@ -3559,6 +3560,8 @@ static void addrconf_dad_begin(struct in out: spin_unlock(&ifp->lock); read_unlock_bh(&idev->lock); + if (notify) + ipv6_ifa_notify(RTM_NEWADDR, ifp); } static void addrconf_dad_start(struct inet6_ifaddr *ifp)