[NET]: fix oops after tunnel module unload

Tunnel modules used to obtain module refcount each time when
some tunnel was created, which meaned that tunnel could be unloaded
only after all the tunnels are deleted.

Since killing old MOD_*_USE_COUNT macros this protection has gone.
It is possible to return it back as module_get/put, but it looks
more natural and practically useful to force destruction of all
the child tunnels on module unload.

Signed-off-by: Alexey Kuznetsov <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/ipv4/ip_gre.c

···
 
 	dev_hold(dev);
 	ipgre_tunnel_link(nt);
-	/* Do not decrement MOD_USE_COUNT here. */
 	return nt;
 
 failed:
···
 	goto out;
 }
 
-static void ipgre_fini(void)
+static void __exit ipgre_destroy_tunnels(void)
+{
+	int prio;
+
+	for (prio = 0; prio < 4; prio++) {
+		int h;
+		for (h = 0; h < HASH_SIZE; h++) {
+			struct ip_tunnel *t;
+			while ((t = tunnels[prio][h]) != NULL)
+				unregister_netdevice(t->dev);
+		}
+	}
+}
+
+static void __exit ipgre_fini(void)
 {
 	if (inet_del_protocol(&ipgre_protocol, IPPROTO_GRE) < 0)
 		printk(KERN_INFO "ipgre close: can't remove protocol\n");
 
-	unregister_netdev(ipgre_fb_tunnel_dev);
+	rtnl_lock();
+	ipgre_destroy_tunnels();
+	rtnl_unlock();
 }
 
 module_init(ipgre_init);

net/ipv4/ipip.c

···
 
 	dev_hold(dev);
 	ipip_tunnel_link(nt);
-	/* Do not decrement MOD_USE_COUNT here. */
 	return nt;
 
 failed:
···
 	goto out;
 }
 
+static void __exit ipip_destroy_tunnels(void)
+{
+	int prio;
+
+	for (prio = 1; prio < 4; prio++) {
+		int h;
+		for (h = 0; h < HASH_SIZE; h++) {
+			struct ip_tunnel *t;
+			while ((t = tunnels[prio][h]) != NULL)
+				unregister_netdevice(t->dev);
+		}
+	}
+}
+
 static void __exit ipip_fini(void)
 {
 	if (ipip_unregister() < 0)
 		printk(KERN_INFO "ipip close: can't deregister tunnel\n");
 
-	unregister_netdev(ipip_fb_tunnel_dev);
+	rtnl_lock();
+	ipip_destroy_tunnels();
+	unregister_netdevice(ipip_fb_tunnel_dev);
+	rtnl_unlock();
 }
 
 module_init(ipip_init);

net/ipv6/sit.c

···
 	dev_hold(dev);
 
 	ipip6_tunnel_link(nt);
-	/* Do not decrement MOD_USE_COUNT here. */
 	return nt;
 
 failed:
···
 	.err_handler	=	ipip6_err,
 };
 
+static void __exit sit_destroy_tunnels(void)
+{
+	int prio;
+
+	for (prio = 1; prio < 4; prio++) {
+		int h;
+		for (h = 0; h < HASH_SIZE; h++) {
+			struct ip_tunnel *t;
+			while ((t = tunnels[prio][h]) != NULL)
+				unregister_netdevice(t->dev);
+		}
+	}
+}
+
 void __exit sit_cleanup(void)
 {
 	inet_del_protocol(&sit_protocol, IPPROTO_IPV6);
-	unregister_netdev(ipip6_fb_tunnel_dev);
+
+	rtnl_lock();
+	sit_destroy_tunnels();
+	unregister_netdevice(ipip6_fb_tunnel_dev);
+	rtnl_unlock();
 }
 
 int __init sit_init(void)