sddm hangs with mouse cursor on blank screen when pam_mount.conf.xml is malformed(?)

[cleary]

What you expected to happen:
sddm would display the theme, dialogs etc that would allow me to login

What actually happened:
sddm loads far enough to show the mouse cursor, but the background is still black/blank/showing tty1 boot logs

It doesn't go any further, and I can't login with it.

A minimal series of steps necessary to make it happen:
1. install sddm
2. install libpam-mount
3. Add a minimal config to /etc/security/pam_mount.conf.xml, ala:
     https://paste.debian.net/1030743/
    - note the "malformed" entry does not have an sgrp attribute defined (I'm not convinced this actually constitutes a malformed entry)

4. run pam-auth-update and enable the entry "Mount volumes for user"
5. restart sddm

At this point sddm hangs with a blank screen, and mouse cursor. There are no errors in logs, the only clue is that the PAM logging pauses

This doesn't affect any other DMs that I've tried (lightdm, gdm3)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[ITEAS (info-tux-pc)]

Same Problem.

[ITEAS (info-tux-pc)]

Fixed, with an exclude option:

...
<volume fstype="cifs" server="storage.tux.local" options="vers=3.0" path="iso-images" mountpoint="~/iso-images"> <not><user>root</user></not> <not><user>sddm</user></not> </volume>
...