The 2017/18 rule ok defining when a goalkeeper has a ball under control has changed slightly. It now reads “A goalkeeper is considered to be in control of the ball when the ball is between the hand and any surface ( eg ground, own body) or touching it with any part of the hands or arms.
A goalkeeper cannot be challenged by an opponent when in control of the ball with the hand.
Under the current and yes very soft guidelines he probably did have the ball under his control so any contact would be defined as a challenge and yes as Poll said contact is all that’s required for it to be a foul.