My 3 month old kitten doesn't know when to stop eating

This is my first time adopting a kitten, he's been with me since he was a week old because his mother died. I have recently started giving him dry food and he likes it. The problem is he tore through the 3kg packet and ate too much. I sealed the packet again and kept it where I was sure he wouldn't reach (I was wrong). Tore through it again and his belly has been like this. Do all orphaned cats don't know when they should stop or is it just a kitten thing? Any advice on how to teach him is welcome.

Ps. 3rd one is an older picture of him for belly size reference (a very handsome boi he is).

Ps. I have now transferred all the contents from the packet to a sealed food storage container made from food grade hard plastic.