Xorg crashes when it tries to resume a scale transformation after that Screen has been closed. Crashed in __strlen_avx2() from transform_filter_length() from ProcRRGetCrtcTransform()

[Marco Trevisan (Treviño)]

Happens in X.Org X Server 2:1.20.3-1ubuntu1, but also previous versions

Very easy to reproduce:
    Start a simple (empty) X server instance (say Xorg :2 vt8)
    Set a scale transformation
        xrandr -d :2 --output eDP-1 --scale 2x2
    Call xrandr again so that the server tries to resume the previous transformation
        xrandr -d :2

I've addressed the issue at https://gitlab.freedesktop.org/xorg/xserver/issues/14 and proposed various fixes for that, but so far no feedback.

Marking it as incoming rls bug as this needs to be addressed as per supporting xrandr scaling support in desktop.

[Marco Trevisan (Treviño) (3v1n0)]

Since I'm not getting much feedback upstream, it might be worth to fix this in Ubuntu with something like this:

  https://gitlab.freedesktop.org/3v1n0/xserver/commit/a6ad02ea177

[Marco Trevisan (Treviño) (3v1n0)]

Another related issue with scaling is https://gitlab.freedesktop.org/xorg/xserver/issues/668

[Marco Trevisan (Treviño) (3v1n0)]

This bug was fixed in the package xorg-server - 2:1.20.4-1ubuntu3

---------------
xorg-server (2:1.20.4-1ubuntu3) disco; urgency=medium

  * sync-i965-pciids.diff: Sync with mesa, add support for CML. (LP:
    #1821863)
  * dix-ensure-work-queues-are-cleared-on-reset.diff: Fix a race
    condition that might crash the server.
  * reset-transforms-in-closescreen.diff: Fix a crash when resuming a
    scale transformation after closing the screen. (LP: #1820850, LP: #1805200)

 -- Timo Aaltonen <email address hidden> Wed, 03 Apr 2019 12:03:57 +0300