netdev - [Patch net] bonding: fix a potential double-unregister

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Date:   Fri, 14 Aug 2020 20:05:58 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     netdev@...r.kernel.org
Cc:     Cong Wang <xiyou.wangcong@...il.com>,
        syzbot+af23e7f3e0a7e10c8b67@...kaller.appspotmail.com,
        Eric Dumazet <eric.dumazet@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>,
        Jay Vosburgh <j.vosburgh@...il.com>
Subject: [Patch net] bonding: fix a potential double-unregister

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@...kaller.appspotmail.com
Cc: Eric Dumazet <eric.dumazet@...il.com>
Cc: Andy Gospodarek <andy@...yhouse.net>
Cc: Jay Vosburgh <j.vosburgh@...il.com>
Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>
---
 drivers/net/bonding/bond_main.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 5ad43aaf76e5..995fcb4eed92 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -2205,7 +2205,8 @@ static int bond_release_and_destroy(struct net_device *bond_dev,
 	int ret;
 
 	ret = __bond_release_one(bond_dev, slave_dev, false, true);
-	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\n");
 		bond_remove_proc_entry(bond);
-- 
2.28.0