If a passenger has marijuana do I get arrested?
To convict you of possession the state has to prove beyond a reasonable doubt that you had knowledge and actual or constructive control of a controlled substance.
You don't want the upfront experience of listening to lawyers argue over the fine distinctions between actual or constructive control, dominion, reach, knowledge.
You're certainly foolish, perhaps crazy, to remain in a vehicle when anyone in the car has a controlled substance. If a cop pulls the car over, your other passenger is almost certain to throw it under the seat, or on your lap, or out the window. Then it's anybody's game.
Do not ride in a vehicle if anyone in the vehicle has a controlled substance. They have to get out. If they don't get out of the car then you get out of the car. The End. No discussion.