vxlan: Handle error of rtnl_register_module().

Since introduced, vxlan_vnifilter_init() has been ignoring the
returned value of rtnl_register_module(), which could fail silently.

Handling the error allows users to view a module as an all-or-nothing
thing in terms of the rtnetlink functionality.  This prevents syzkaller
from reporting spurious errors from its tests, where OOM often occurs
and module is automatically loaded.

Let's handle the errors by rtnl_register_many().

Fixes: f9c4bb0 ("vxlan: vni filtering support on collect metadata device")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/vxlan/vxlan_core.c

@@ -4913,9 +4913,13 @@ static int __init vxlan_init_module(void)
 	if (rc)
 		goto out4;
 
-	vxlan_vnifilter_init();
+	rc = vxlan_vnifilter_init();
+	if (rc)
+		goto out5;
 
 	return 0;
+out5:
+	rtnl_link_unregister(&vxlan_link_ops);
 out4:
 	unregister_switchdev_notifier(&vxlan_switchdev_notifier_block);
 out3:

drivers/net/vxlan/vxlan_private.h

@@ -202,7 +202,7 @@ int vxlan_vni_in_use(struct net *src_net, struct vxlan_dev *vxlan,
 int vxlan_vnigroup_init(struct vxlan_dev *vxlan);
 void vxlan_vnigroup_uninit(struct vxlan_dev *vxlan);
 
-void vxlan_vnifilter_init(void);
+int vxlan_vnifilter_init(void);
 void vxlan_vnifilter_uninit(void);
 void vxlan_vnifilter_count(struct vxlan_dev *vxlan, __be32 vni,
 			   struct vxlan_vni_node *vninode,

drivers/net/vxlan/vxlan_vnifilter.c

@@ -992,19 +992,18 @@ static int vxlan_vnifilter_process(struct sk_buff *skb, struct nlmsghdr *nlh,
 	return err;
 }
 
-void vxlan_vnifilter_init(void)
+static const struct rtnl_msg_handler vxlan_vnifilter_rtnl_msg_handlers[] = {
+	{THIS_MODULE, PF_BRIDGE, RTM_GETTUNNEL, NULL, vxlan_vnifilter_dump, 0},
+	{THIS_MODULE, PF_BRIDGE, RTM_NEWTUNNEL, vxlan_vnifilter_process, NULL, 0},
+	{THIS_MODULE, PF_BRIDGE, RTM_DELTUNNEL, vxlan_vnifilter_process, NULL, 0},
+};
+
+int vxlan_vnifilter_init(void)
 {
-	rtnl_register_module(THIS_MODULE, PF_BRIDGE, RTM_GETTUNNEL, NULL,
-			     vxlan_vnifilter_dump, 0);
-	rtnl_register_module(THIS_MODULE, PF_BRIDGE, RTM_NEWTUNNEL,
-			     vxlan_vnifilter_process, NULL, 0);
-	rtnl_register_module(THIS_MODULE, PF_BRIDGE, RTM_DELTUNNEL,
-			     vxlan_vnifilter_process, NULL, 0);
+	return rtnl_register_many(vxlan_vnifilter_rtnl_msg_handlers);
 }
 
 void vxlan_vnifilter_uninit(void)
 {
-	rtnl_unregister(PF_BRIDGE, RTM_GETTUNNEL);
-	rtnl_unregister(PF_BRIDGE, RTM_NEWTUNNEL);
-	rtnl_unregister(PF_BRIDGE, RTM_DELTUNNEL);
+	rtnl_unregister_many(vxlan_vnifilter_rtnl_msg_handlers);
 }