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Date: Fri, 8 Dec 2017 06:43:44 +0200 From: "Michael S. Tsirkin" <mst@...hat.com> To: Jason Wang <jasowang@...hat.com> Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, Eric Dumazet <eric.dumazet@...il.com>, Willem de Bruijn <willemb@...gle.com> Subject: Re: [PATCH net-next V2] tuntap: fix possible deadlock when fail to register netdev 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 <eric.dumazet@...il.com> > Cc: Eric Dumazet <eric.dumazet@...il.com> > Cc: Willem de Bruijn <willemb@...gle.com> > Signed-off-by: Jason Wang <jasowang@...hat.com> Acked-by: Michael S. Tsirkin <mst@...hat.com> > --- > 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
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