Foul/Contact on a post up

[lordrayvin]

Okay, here's the situation: Player A has the ball in the post and is being guarded by Player B. Player A has his back to the basket and Player B. Now, Player B is toe to heel with Player A with his body bent at the waist with is back hovering over Player A's back. First off, is this legal defense in NBA? Secondly, if Player A jumps up for a shot and hits Player B on the way up because Player B is hovering over their back, what is the call? Thanks for any help and let me know if you need some more clarification.