net: openvswitch: fix a NULL pointer dereference

mainline inclusion
from mainline-5.1-rc3
commit 6f19893b644a
category: bugfix
bugzilla: 13294
CVE: NA

-------------------------------------------------

upcall is dereferenced even when genlmsg_put fails. The fix
goto out to avoid the NULL pointer dereference in this case.
Signed-off-by: NKangjie Lu <kjlu@umn.edu>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NZhiqiang Liu <liuzhiqiang26@huawei.com>
Reviewed-by: NWenan Mao <maowenan@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

net/openvswitch/datapath.c

@@ -448,6 +448,10 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
 
 	upcall = genlmsg_put(user_skb, 0, 0, &dp_packet_genl_family,
 			     0, upcall_info->cmd);
+	if (!upcall) {
+		err = -EINVAL;
+		goto out;
+	}
 	upcall->dp_ifindex = dp_ifindex;
 
 	err = ovs_nla_put_key(key, key, OVS_PACKET_ATTR_KEY, false, user_skb);