Revert "vlan: Fix VLAN 0 memory leak"

This reverts commit 718cb09.

The commit triggers multiple syzbot issues, probably due to possibility of
manually creating VLAN 0 on netdevice which will cause the code to delete
it since it can't distinguish such VLAN from implicit VLAN 0 automatically
created for devices with NETIF_F_HW_VLAN_CTAG_FILTER feature.

Reported-by: syzbot+662f783a5cdf3add2719@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/00000000000090196d0602a6167d@google.com/
Reported-by: syzbot+4b4f06495414e92701d5@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/00000000000096ae870602a61602@google.com/
Reported-by: syzbot+d810d3cd45ed1848c3f7@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/0000000000009f0f9c0602a616ce@google.com/
Fixes: 718cb09 ("vlan: Fix VLAN 0 memory leak")
Signed-off-by: Vlad Buslov <vladbu@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/8021q/vlan.c

@@ -384,7 +384,8 @@ static int vlan_device_event(struct notifier_block *unused, unsigned long event,
 			dev->name);
 		vlan_vid_add(dev, htons(ETH_P_8021Q), 0);
 	}
-	if (event == NETDEV_DOWN)
+	if (event == NETDEV_DOWN &&
+	    (dev->features & NETIF_F_HW_VLAN_CTAG_FILTER))
 		vlan_vid_del(dev, htons(ETH_P_8021Q), 0);
 
 	vlan_info = rtnl_dereference(dev->vlan_info);