From 124da8f6118bce3d9aeb5c6f5395ed131141aad5 Mon Sep 17 00:00:00 2001 From: Jason Wang Date: Fri, 8 Dec 2017 12:02:30 +0800 Subject: [PATCH] tuntap: fix possible deadlock when fail to register netdev 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 Reviewed-by: Eric Dumazet Signed-off-by: David S. Miller --- 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 c2ad8f3858d1..e367d6310353 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -2048,8 +2048,11 @@ 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); @@ -2065,9 +2068,7 @@ 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) -- 2.30.2