What were you trying to do that didn't work?

When using XDMCP in GDM (no xinetd/VNC configuration involved), when the display locks due to being idle, the file descriptor that is created for this is not cleared when the screen is woken up and the login prompt is shown. Should multiple clients (for example, 100+) be utilizing XDMCP at once and entering idle state frequently, this can cause the system to hit it's file descriptor limit quickly.

Please provide the package NVR for which bug is seen:

gdm-3.28.2-26.el7.x86_64

How reproducible:

Customer who I am filing this for and I were both able to reproduce this behavior.

Steps to reproduce

1.  Configure XDMCP for GDM via steps in https://access.redhat.com/solutions/2736
2.  After restarting GDM, connect and login to XDMCP session via a Xserver, then check file descriptor count for gdm with 'lsof -n | grep gdm | wc -l' in a SSH session.
3. Allow screen to idle, then run command again and observe the total.
4. Wake up screen, then login again. Run above command again and observe total is 1+ from prior 

Expected results

File descriptor for screen lock is cleared when the screen is unlocked.

Actual results

Screen lock file descriptor remains present even after unlocking screen.