From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH net-next V2] tuntap: fix possible deadlock when fail to register netdev Date: Fri, 8 Dec 2017 06:43:44 +0200 Message-ID: <20171208064232-mutt-send-email-mst@kernel.org> References: <1512705750-14799-1-git-send-email-jasowang@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Eric Dumazet , Willem de Bruijn To: Jason Wang Return-path: Content-Disposition: inline In-Reply-To: <1512705750-14799-1-git-send-email-jasowang@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Fri, Dec 08, 2017 at 12:02:30PM +0800, Jason Wang wrote: > 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 Acked-by: Michael S. Tsirkin > --- > 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