netlabel: Prevent setsockopt() from changing the hop-by-hop option.

If a socket has a netlabel in place then don't let setsockopt() alter
the socket's IPv6 hop-by-hop option.  This is in the same spirit as
the existing check for IPv4.
Signed-off-by: Huw Davies <huw@codeweavers.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

security/selinux/netlabel.c

@@ -409,6 +409,21 @@ int selinux_netlbl_sock_rcv_skb(struct sk_security_struct *sksec,
 	return rc;
 }
 
+/**
+ * selinux_netlbl_option - Is this a NetLabel option
+ * @level: the socket level or protocol
+ * @optname: the socket option name
+ *
+ * Description:
+ * Returns true if @level and @optname refer to a NetLabel option.
+ * Helper for selinux_netlbl_socket_setsockopt().
+ */
+static inline int selinux_netlbl_option(int level, int optname)
+{
+	return (level == IPPROTO_IP && optname == IP_OPTIONS) ||
+		(level == IPPROTO_IPV6 && optname == IPV6_HOPOPTS);
+}
+
 /**
  * selinux_netlbl_socket_setsockopt - Do not allow users to remove a NetLabel
  * @sock: the socket
@@ -431,7 +446,7 @@ int selinux_netlbl_socket_setsockopt(struct socket *sock,
 	struct sk_security_struct *sksec = sk->sk_security;
 	struct netlbl_lsm_secattr secattr;
 
-	if (level == IPPROTO_IP && optname == IP_OPTIONS &&
+	if (selinux_netlbl_option(level, optname) &&
 	    (sksec->nlbl_state == NLBL_LABELED ||
 	     sksec->nlbl_state == NLBL_CONNLABELED)) {
 		netlbl_secattr_init(&secattr);