[MLSXFRM]: Add security sid to sock

This adds security for IP sockets at the sock level. Security at the
sock level is needed to enforce the SELinux security policy for
security associations even when a sock is orphaned (such as in the TCP
LAST_ACK state).

This will also be used to enforce SELinux controls over data arriving
at or leaving a child socket while it's still waiting to be accepted.

Signed-off-by: Venkat Yekkirala <vyekkirala@TrustedCS.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/sock.h b/include/net/sock.h
index 324b3ea..91cdceb 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -972,6 +972,19 @@
 	write_unlock_bh(&sk->sk_callback_lock);
 }
 
+static inline void sock_copy(struct sock *nsk, const struct sock *osk)
+{
+#ifdef CONFIG_SECURITY_NETWORK
+	void *sptr = nsk->sk_security;
+#endif
+
+	memcpy(nsk, osk, osk->sk_prot->obj_size);
+#ifdef CONFIG_SECURITY_NETWORK
+	nsk->sk_security = sptr;
+	security_sk_clone(osk, nsk);
+#endif
+}
+
 extern int sock_i_uid(struct sock *sk);
 extern unsigned long sock_i_ino(struct sock *sk);