ipv6: Fix the return value of Set Hop-by-Hop options header with NULL data pointer

When Set Hop-by-Hop options header with NULL data 
pointer and optlen is not zero use setsockopt(),
the kernel successfully return 0 instead of 
return error EINVAL or EFAULT.

This patch fix the problem.
Signed-off-by: NYang Hongyang <yanghy@cn.fujitsu.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv6/ipv6_sockglue.c

@@ -346,6 +346,8 @@ static int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
 		 */
 		if (optlen == 0)
 			optval = NULL;
+		else if (optval == NULL)
+			goto e_inval;
 		else if (optlen < sizeof(struct ipv6_opt_hdr) ||
 			 optlen & 0x7 || optlen > 8 * 255)
 			goto e_inval;