Author: Julia Lawall <julia@diku.dk> genlmsg_cancel subtracts some constants from its second argument before calling nlmsg_cancel. nlmsg_cancel then calls nlmsg_trim on the same arguments. nlmsg_trim tests for NULL before doing any computation, but a NULL second argument to genlmsg_cancel is no longer NULL due to the initial subtraction. Nothing else happens in this execution, so the …