When you take admission through entrances in any IIT, you are admitted to the institute as a provisional student which means that if you fail to satisfy any criteria then your admission will be cancelled. Thus if you get unable to show that you have passed your final exams  or don't satisfy the minimum eligibility marks for the course then your admission will be cancelled as per the rules and regulations.

To know more about GATE visit the link below:

https://engineering.careers360.com/articles/gate

I hope this helps.