openvswitch: Validate IPv6 flow key and mask values.

Reject flow label key and mask values with invalid bits set.
Introduced by commit 3fdbd1ce11e5 ("openvswitch: add ipv6 'set'
action").

Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
Acked-by: Jesse Gross <jesse@nicira.com>
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>

net/openvswitch/flow_netlink.c

@@ -689,6 +689,13 @@ static int ovs_key_from_nlattrs(struct sw_flow_match *match, u64 attrs,
 				ipv6_key->ipv6_frag, OVS_FRAG_TYPE_MAX);
 			return -EINVAL;
 		}
+
+		if (ipv6_key->ipv6_label & htonl(0xFFF00000)) {
+			OVS_NLERR("IPv6 flow label %x is out of range (max=%x).\n",
+				  ntohl(ipv6_key->ipv6_label), (1 << 20) - 1);
+			return -EINVAL;
+		}
+
 		SW_FLOW_KEY_PUT(match, ipv6.label,
 				ipv6_key->ipv6_label, is_mask);
 		SW_FLOW_KEY_PUT(match, ip.proto,