Care to explain, instead of posting snarky remarks?
You can't exploit this without making Xorg overflow its stack. Even with the changes to the kernel that will cause Xorg to crash. Ergo, it is a bug in Xorg. It's nice that the kernel offers a way to catch stack overflows, but the responsibility lies with Xorg not to do that in the first place. This is no more a kernel security bug than an internal Xorg buffer overflow or the like, which can lead to exactly the same sort of privilege elevation.
If you're the kind to rely on guard pages for security rather than avoiding stack overflow by design, I suppose we can be glad you don't do security development.