[PATCH 4.9 01/78] bonding: fix a potential double-unregister

[Greg Kroah-Hartman]

From: Cong Wang <xiyou.wangcong@xxxxxxxxx>

[ Upstream commit 832707021666411d04795c564a4adea5d6b94f17 ]

When we tear down a network namespace, we unregister all
the netdevices within it. So we may queue a slave device
and a bonding device together in the same unregister queue.

If the only slave device is non-ethernet, it would
automatically unregister the bonding device as well. Thus,
we may end up unregistering the bonding device twice.

Workaround this special case by checking reg_state.

Fixes: 9b5e383c11b0 ("net: Introduce unregister_netdevice_many()")
Reported-by: syzbot+af23e7f3e0a7e10c8b67@xxxxxxxxxxxxxxxxxxxxxxxxx
Cc: Eric Dumazet <eric.dumazet@xxxxxxxxx>
Cc: Andy Gospodarek <andy@xxxxxxxxxxxxx>
Cc: Jay Vosburgh <j.vosburgh@xxxxxxxxx>
Signed-off-by: Cong Wang <xiyou.wangcong@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/net/bonding/bond_main.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -1985,7 +1985,8 @@ static int  bond_release_and_destroy(str
 	int ret;
 
 	ret = bond_release(bond_dev, slave_dev);
-	if (ret == 0 && !bond_has_slaves(bond)) {
+	if (ret == 0 && !bond_has_slaves(bond) &&
+	    bond_dev->reg_state != NETREG_UNREGISTERING) {
 		bond_dev->priv_flags |= IFF_DISABLE_NETPOLL;
 		netdev_info(bond_dev, "Destroying bond %s\n",
 			    bond_dev->name);