From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752658AbdLHECl (ORCPT ); Thu, 7 Dec 2017 23:02:41 -0500 Received: from mx1.redhat.com ([209.132.183.28]:37042 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752183AbdLHECj (ORCPT ); Thu, 7 Dec 2017 23:02:39 -0500 From: Jason Wang To: netdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org, mst@redhat.com, Jason Wang , Eric Dumazet , Willem de Bruijn Subject: [PATCH net-next V2] tuntap: fix possible deadlock when fail to register netdev Date: Fri, 8 Dec 2017 12:02:30 +0800 Message-Id: <1512705750-14799-1-git-send-email-jasowang@redhat.com> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Fri, 08 Dec 2017 04:02:39 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Private destructor could be called when register_netdev() fail with rtnl lock held. This will lead deadlock in tun_free_netdev() who tries to hold rtnl_lock. Fixing this by switching to use spinlock to synchronize. Fixes: 96f84061620c ("tun: add eBPF based queue selection method") Reported-by: Eric Dumazet Cc: Eric Dumazet Cc: Willem de Bruijn Signed-off-by: Jason Wang --- drivers/net/tun.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/net/tun.c b/drivers/net/tun.c index 787cc35..8d85163 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -2050,8 +2050,11 @@ static int __tun_set_steering_ebpf(struct tun_struct *tun, new->prog = prog; } - old = rtnl_dereference(tun->steering_prog); + spin_lock_bh(&tun->lock); + old = rcu_dereference_protected(tun->steering_prog, + lockdep_is_held(&tun->lock)); rcu_assign_pointer(tun->steering_prog, new); + spin_unlock_bh(&tun->lock); if (old) call_rcu(&old->rcu, tun_steering_prog_free); @@ -2067,9 +2070,7 @@ static void tun_free_netdev(struct net_device *dev) free_percpu(tun->pcpu_stats); tun_flow_uninit(tun); security_tun_dev_free_security(tun->security); - rtnl_lock(); __tun_set_steering_ebpf(tun, NULL); - rtnl_unlock(); } static void tun_setup(struct net_device *dev) -- 2.7.4