Photoshop CC - Marquee Tool selecting to edge of visible canvas

My marquee tool no longer selects the pixel range that I define, and instead selects all the way to to "edge" of my workspace. This is true of both round and rectangular marquee. I suspected that perhaps my external keyboard had some sort of hotkey pressed, but when I unplugged it the issue was still present. It could perhaps be a hotkey on my laptop body but when I tried to "unstick" every key, the issue was still present again.

I also tried resetting all of my tools, which didn't work. A reboot seems to fix it temporarily but it comes back within a couple uses of the tool.

Any ideas what this might be?

Attached is an example. Picture 1 is the selection I define, picture 2 is what happens.