Apparently there are two event horizons in this type of black hole, where the second one is known as the Cauchy horizon. According to Carroll, if you go into the first one, you will fall until you ...
This is it: Nonspinnig, equally massive black hole and white hole experience a direct collision. What shall happen? What shall be the result of such a collision?
So, the canned explanation that I always hear about why the white hole solution of the extended Schwarzschild solution is non-physical is that "The matter distribution cuts off the white hole ...