net: Modify sk_alloc to not reference count the netns of kernel sockets.

Now that sk_alloc knows when a kernel socket is being allocated modify
it to not reference count the network namespace of kernel sockets.

Keep track of if a socket needs reference counting by adding a flag to
struct sock called sk_net_refcnt.

Update all of the callers of sock_create_kern to stop using
sk_change_net and sk_release_kernel as those hacks are no longer
needed, to avoid reference counting a kernel socket.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/sock.h b/include/net/sock.h
index d8dcf91..9e6b2c0 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -184,6 +184,7 @@
 	unsigned char		skc_reuse:4;
 	unsigned char		skc_reuseport:1;
 	unsigned char		skc_ipv6only:1;
+	unsigned char		skc_net_refcnt:1;
 	int			skc_bound_dev_if;
 	union {
 		struct hlist_node	skc_bind_node;
@@ -323,6 +324,7 @@
 #define sk_reuse		__sk_common.skc_reuse
 #define sk_reuseport		__sk_common.skc_reuseport
 #define sk_ipv6only		__sk_common.skc_ipv6only
+#define sk_net_refcnt		__sk_common.skc_net_refcnt
 #define sk_bound_dev_if		__sk_common.skc_bound_dev_if
 #define sk_bind_node		__sk_common.skc_bind_node
 #define sk_prot			__sk_common.skc_prot