Re: [PATCH net-next V2] tuntap: fix possible deadlock when fail to register netdev
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From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2017-12-08 04:43:47
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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 <redacted>
Cc: Eric Dumazet <redacted>
Cc: Willem de Bruijn <willemb@google.com>
Signed-off-by: Jason Wang <redacted>Acked-by: Michael S. Tsirkin <mst@redhat.com>
quoted hunk ↗ jump to hunk
--- 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