net: openvswitch: fix a NULL pointer dereference

net: openvswitch: fix a NULL pointer dereference

Upstream commit:
    commit 6f19893b644a9454d85e593b5e90914e7a72b7dd
    Author: Kangjie Lu <kjlu@umn.edu>
    Date:   Thu Mar 14 23:20:16 2019 -0500

    net: openvswitch: fix a NULL pointer dereference

    upcall is dereferenced even when genlmsg_put fails. The fix
    goto out to avoid the NULL pointer dereference in this case.

    Signed-off-by: Kangjie Lu <kjlu@umn.edu>
    Signed-off-by: David S. Miller <davem@davemloft.net>
Cc:  Kangjie Lu <kjlu@umn.edu>
Reviewed-by: Yifeng Sun <pkusunyifeng@gmail.com>
Signed-off-by: Greg Rose <gvrose8192@gmail.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>