net: kernel socket should be released in init_net namespace

Creating a kernel socket with sock_create_kern() happens in "init_net"
namespace, however, releasing it with sk_release_kernel() occurs in
the current namespace which may be different with "init_net" namespace.
Therefore, we should guarantee that the namespace in which a kernel
socket is created is same as the socket is created.
Signed-off-by: NYing Xue <ying.xue@windriver.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/sock.c

@@ -1454,8 +1454,8 @@ void sk_release_kernel(struct sock *sk)
 		return;
 
 	sock_hold(sk);
-	sock_release(sk->sk_socket);
 	sock_net_set(sk, get_net(&init_net));
+	sock_release(sk->sk_socket);
 	sock_put(sk);
 }
 EXPORT_SYMBOL(sk_release_kernel);