vxlan: correctly validate VXLAN ID against VXLAN_N_VID

commit 4e37d691 upstream.

The incorrect check caused an off-by-one error: the maximum VID 0xffffff
was unusable.

Fixes: d342894c ("vxlan: virtual extensible lan")
Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>
Acked-by: Jiri Benc <jbenc@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/net/vxlan.c

@@ -2326,7 +2326,7 @@ static int vxlan_validate(struct nlattr *tb[], struct nlattr *data[])
 
 	if (data[IFLA_VXLAN_ID]) {
 		__u32 id = nla_get_u32(data[IFLA_VXLAN_ID]);
-		if (id >= VXLAN_VID_MASK)
+		if (id >= VXLAN_N_VID)
 			return -ERANGE;
 	}