Description of problem:
Attempting to lock the screen using "dm-tool lock"/"dm-tool switch-to-greeter" or the GUI equivalents appears to break LightDM entirely, making it impossible to log back in graphically, use a tty, or restart X with keyboard shortcuts or the terminal.

Version-Release number of selected component (if applicable):
lightdm-1.10.6-4.fc23.x86_64

This appears to have started after updating from lightdm-1.10.6-2.fc23.x86_64 to lightdm-1.10.6-4.fc23.x86_64. However, I updated lightdm along with a bunch of other packages, so I'm not certain if there's something else involved.

How reproducible:
Always.

Steps to Reproduce:
1. Log in to a graphical session using LightDM (in my case, I'm running XFCE).
2. Run "dm-tool lock".

Actual results:
I get dumped to what appears to be tty2, and can't get back into my graphical session. Additionally, half of my keyboard inputs get eaten seemingly at random, rendering it effectively impossible to log in to the tty, switch ttys, or kill the X server.

Hitting the power button on the machine still works, and triggers a normal shutdown, as do SysRq inputs. Lately, I've taken to SSHing into the machine and restarting the lightdm service that way, after which things seem to work again.

Expected results:
The graphical session is locked, allowing the user to unlock their session or log in with a new one via the LightDM greeter.

Additional info:
Given the weirdness of the situation, and the fact that no one else has reported it, I'd hazard a guess that there's something specific to my setup involved here. As to what that could be, I haven't a clue. I am running the NVIDIA binary drivers via kmod-nvidia from RPM Fusion, in case that's relevant.