Here is the official rule for goaltending

Section 17. Basket Interference and Goaltending
Art. 1. It is a violation to commit basket interference or goaltending.
Art. 2. Basket interference
a. Basket interference occurs when a player:
1. Touches the ball or any part of the basket while the ball is on or within
the basket;
2-BasketballRule from JC.indd 84 8/5/2013 9:09:29 AM
Rule 9 / Violations and Penalties 85
2. Touches the ball while any part of it is within the cylinder that has the
ring as its lower base;
3. Reaches through the basket from below and touches the ball before it
enters the cylinder; or
4. Pulls down a movable ring so that it contacts the ball before the ring
returns to its original position.
5. Causes the basket or backboard to vibrate when the ball is on or within
the basket or the backboard and/or is on or in the cylinder.
b. The cylinder is the imaginary geometric figure that has the ring as its base
and is formed by the upward extension of that ring.
c. The ball shall be considered to be within the basket when any part of the ball
is below the cylinder and the level of the ring.
d. A player may have a hand legally in contact with the ball, when this contact
continues after the ball enters the cylinder or when, during such action, the
player touches or grabs the basket.
Art. 3. Goaltending.
a. Goaltending occurs when a defensive player touches the ball during a fieldgoal try and each of the following conditions is met: (Exceptions: Rule
10-4.1.i)
1. The ball is on its downward flight; and
2. The ball is above the level of the ring and has the possibility, while in
flight, of entering the basket and is not touching the cylinder.
b. It is goaltending to touch the ball outside the cylinder during a free throw,
regardless of whether the free throw is on its upward or downward flight.
c. When the ball contacts the backboard and any part of the ball is above the
rim during a field goal attempt, it is considered to be on its downward flight.
In such a case, it is goaltending when the ball is touched by a player as
long as it has a possibility of entering the basket.

https://ncaambb.arbitersports.com/Groups/104883/Library/files/BR15.pdf