From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: [PATCH net-next] tuntap: fix possible deadlock when fail to register netdev Date: Fri, 8 Dec 2017 10:54:15 +0800 Message-ID: <1512701655-18751-1-git-send-email-jasowang@redhat.com> Cc: mst@redhat.com, Jason Wang , Eric Dumazet , Willem de Bruijn To: netdev@vger.kernel.org, linux-kernel@vger.kernel.org Return-path: Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.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..f7ccd79 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(&tun->lock); + old = rcu_dereference_protected(tun->steering_prog, + lock_is_held(&tun->lock)); rcu_assign_pointer(tun->steering_prog, new); + spin_unlock(&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