Government-controlled mortgage buyer Freddie Mac on Wednesday posted a narrower loss of $4.1 billon in the third quarter as it asked for an additional $100 million in federal aid — substantially less than the $1.8 billion it sought in the second quarter. The government rescued McLean, Virginia-based Freddie Mac and sibling company Fannie Mae nearly two years ago to cover their losses on soured mortgage loans, and it estimates the bailouts will cost taxpayers up to $259 billion.