vxlan: fix use-after-free on deletion (part 2)

After commit 15a48cc (vxlan: fix use-after-free on deletion)
vxlan_dellink doesn't need to take out the vxlan_dev from the hlist.
Because, that is done in vxlan_vs_del_dev now.
Having it at both the places results in system crash sometimes with
the following stack trace

general protection fault: 0000 [#1] SMP
...
 vxlan_sock_release+0x6a/0xd0 [vxlan]
Call Trace:
 vxlan_stop+0xee/0x310 [vxlan]
 __dev_close_many+0xa8/0x110
 dev_close_many+0x98/0x140
 rollback_registered_many+0x10d/0x310
 unregister_netdevice_many+0x19/0x60
 default_device_exit_batch+0x164/0x190
 ? abort_exclusive_wait+0xb0/0xb0
 ops_exit_list.isra.4+0x59/0x70
 cleanup_net+0x1f0/0x380
 process_one_work+0x165/0x470
 worker_thread+0x112/0x540
 ? rescuer_thread+0x3f0/0x3f0
 kthread+0xda/0xf0

It crashes here:

static void vxlan_vs_del_dev(struct vxlan_dev *vxlan)
{
	struct vxlan_net *vn = net_generic(vxlan->net, vxlan_net_id);

	spin_lock(&vn->sock_lock);
	hlist_del_init_rcu(&vxlan->hlist); <--- here
	spin_unlock(&vn->sock_lock);
}

Orabug: 29927196

Reviewed-by: Rama Nichanamatlu <[email protected]>
Signed-off-by: Venkat Venkatsubra <[email protected]>
Signed-off-by: Brian Maly <[email protected]>

Author: venkatxvenkatsubra

drivers/net/vxlan.c

@@ -2874,12 +2874,6 @@ static int vxlan_newlink(struct net *src_net, struct net_device *dev,
 static void vxlan_dellink(struct net_device *dev, struct list_head *head)
 {
 	struct vxlan_dev *vxlan = netdev_priv(dev);
-	struct vxlan_net *vn = net_generic(vxlan->net, vxlan_net_id);
-
-	spin_lock(&vn->sock_lock);
-	if (!hlist_unhashed(&vxlan->hlist))
-		hlist_del_rcu(&vxlan->hlist);
-	spin_unlock(&vn->sock_lock);
 
 	gro_cells_destroy(&vxlan->gro_cells);
 	list_del(&vxlan->next);