Nastia Liukin didn't seem too upset to hear convicted child molester Larry Nassar was attacked in prison by another inmate ... telling TMZ Sports that was "karma."
The ex-Team USA gymnast -- who's friends with several Nassar victims including McKayla Maroney and Aly Raisman -- found justice in Larry's prison assault ... shrugging her shoulders at the news.
FYI ... HBO just picked up the rights to a Nassar documentary that will unveil what female gymnasts had to endure at the hands of the team doctor ... and Liukin tells us she'll watch to support her friends and former teammates.
Nassar is currently serving up to 175 years in prison for his crimes.