Basically, if your study permit is expired, then you are not allow to stay in Canada anymore....
The only way that you can stay even your study permit expired is if you waiting for the renewal process of your study permit,
Please check this link
https://www.cic.gc.ca/english/helpcentre/answer.asp?qnum=475
and its written ;
"
If your study permit has already expired
If you applied to extend your study permit before it expired, but haven’t received a decision on your application, you’re allowed to stay in Canada because you’ve maintained your status. This means you’re a temporary resident until we decide on your application. You can keep studying until you get a decision on your application.
If you haven’t applied to extend your study permit, you lost your status in Canada. You can’t continue or restart your studies until we’ve restored your status and issued a new study permit. You have 90 days to apply to restore your status and extend your permit. There’s a CAN$200 fee to restore your status, as well as a CAN$150 fee for the new study permit. Find out what to do if your
study permit has expired and you haven’t applied to extend it.
"
Good luck.,
