Overtaking on SC restart

Given how the China Sprint race played out on the SC restart, under what conditions are you allowed to overtake before the start/finish line?

Obviously able to overtake if a car goes off track, breaks down, loses control. But if P1 has recommenced race pace and, and say someone like P5 has a poor exit from the 2nd to last or last corner, but technically remains on track and is going significantly slower as a consequence, wouldn't it be more dangerous for P6, P7, etc, to over-slow to fix the mistake?