ipv6,gre: do not leak info to user-space

There is a hole in struct ip6_tnl_parm2, so we have to
zero the struct on stack before copying it to user-space.

Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <amwang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ip6_gre.c

@@ -1081,6 +1081,7 @@ static int ip6gre_tunnel_ioctl(struct net_device *dev,
 		}
 		if (t == NULL)
 			t = netdev_priv(dev);
+		memset(&p, 0, sizeof(p));
 		ip6gre_tnl_parm_to_user(&p, &t->parms);
 		if (copy_to_user(ifr->ifr_ifru.ifru_data, &p, sizeof(p)))
 			err = -EFAULT;
@@ -1128,6 +1129,7 @@ static int ip6gre_tunnel_ioctl(struct net_device *dev,
 		if (t) {
 			err = 0;
 
+			memset(&p, 0, sizeof(p));
 			ip6gre_tnl_parm_to_user(&p, &t->parms);
 			if (copy_to_user(ifr->ifr_ifru.ifru_data, &p, sizeof(p)))
 				err = -EFAULT;