It's not totally a rubber stamp. There have been a few outright rejections in the previous decade. In addition, they often force bills that have been passed in the house of commons to be reviewed/changed before it evens comes to the Senate. Over the course of the review, the law almost always get changed into something the Senate agrees with and so it gets passed.

But you are correct in the broad sense typically, once a bill passes the house of commons, it will become a law.