On Sat, 31 Aug 2013 13:44:33 +0800
Cong Wang [off-list ref] wrote:

+#if IS_ENABLED(CONFIG_IPV6)
+	} else {
+		ipv6_stub->ipv6_sock_mc_join(sk, ifindex,
+					     &ip->sin6.sin6_addr);
+#endif

This isn't safe against IPv6 module getting unloaded. You either
have to figure out a reference count method, or disable IPv6
module unload.

Since it can only be forced unload anyway, I still argue
it should just be disabled (by removing the module exit hook
and code).