Stop Chimney Leaks!?

I had a wood stove put in my basement the cinder block chimney back side goes up the side of my bedroom the mortor joints have lost mortor and it is leaking down the back of the panneling in my bedroom and into the basement celing, I have taken down the panneling and basement celing tiles. Don't want to put it back up till problem is fixed, need help to stop the leaks! Thanks!