openvswitch: meter: fix NULL pointer dereference in ovs_meter_cmd_reply_start

It seems that the intention of the code is to null check the value
returned by function genlmsg_put. But the current code is null
checking the address of the pointer that holds the value returned
by genlmsg_put.

Fix this by properly null checking the value returned by function
genlmsg_put in order to avoid a pontential null pointer dereference.

Addresses-Coverity-ID: 1461561 ("Dereference before null check")
Addresses-Coverity-ID: 1461562 ("Dereference null return value")
Fixes: 96fbc13d7e ("openvswitch: Add meter infrastructure")
Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/openvswitch/meter.c

@@ -99,7 +99,7 @@ ovs_meter_cmd_reply_start(struct genl_info *info, u8 cmd,
 	*ovs_reply_header = genlmsg_put(skb, info->snd_portid,
 					info->snd_seq,
 					&dp_meter_genl_family, 0, cmd);
-	if (!ovs_reply_header) {
+	if (!*ovs_reply_header) {
 		nlmsg_free(skb);
 		return ERR_PTR(-EMSGSIZE);
 	}