Just update my Linux kernel from version 4.15.0 to 5.3.0 on Ubuntu 18.04 LTS and facing this problem. When unlock my desktop after screen turn-off, a “ghost” cursor showing up on my desktop and stuck there. The bug does not fix yet, but the ghost cursor can remove by this trick without need log off:

Step by step:

  • Lock current session (Windows + L)
  • On the lock screen, click on “Login as another user” (at this point, the ghost cursor should be gone)
  • Login as the same user / or click Cancel then unlock.

You may try a few times if the first time not successful.

Bug detail: https://bugs.launchpad.net/ubuntu/+source/mutter/+bug/1875528