Commit 34934c37d6 restored calling register_damage() in
xwl_realize_window() before ensure_surface_for_window().
However if register_damage() succeeds and ensure_surface_for_window()
returns NULL, it would exit without "unregistering" the damage hook.
The X11 window, however, may still get damages reports, in which case
xwl_window_from_window() would return NULL, causing a NULL pointer
dereference in damage_report().
To avoid the issue, make sure we unregister the damage report if
ensure_surface_for_window() has failed, and add an early exit in
damage_report() if xwl_window is NULL.
v2: unregister_damage() unconditionally if ensure_surface_for_window()
failed (Michel Dänzer)
Fixes: commit 34934c37d6 ("revert: register damage before ensure_surface_for_window")
Closes: https://gitlab.freedesktop.org/xorg/xserver/-/work_items/1886
Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
(cherry picked from commit 36f53145e4)
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/2191>
d346a6dec0