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xwayland: remove dirty window unconditionally on unrealize

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This is a rare occurrence of a crash in Xwayland for which I don't have
the reproducing steps, just a core file.

The backtrace looks as follow:

  #0  raise () from /usr/lib64/libc.so.6
  #1  abort () from /usr/lib64/libc.so.6
  #2  OsAbort () at utils.c:1361
  #3  AbortServer () at log.c:877
  #4  FatalError () at log.c:1015
  #5  OsSigHandler () at osinit.c:154
  #6  <signal handler called>
  #7  xwl_glamor_pixmap_get_wl_buffer () at xwayland-glamor.c:162
  #8  xwl_screen_post_damage () at xwayland.c:514
  #9  block_handler () at xwayland.c:665
  #10 BlockHandler () at dixutils.c:388
  #11 WaitForSomething () at WaitFor.c:219
  #12 Dispatch () at dispatch.c:422
  #13 dix_main () at main.c:287

The crash is caused by dereferencing “xwl_pixmap->buffer” in
xwl_glamor_pixmap_get_wl_buffer() because “xwl_pixmap” is NULL.

Reason for this is because the corresponding pixmap is from the root
window and xwayland is rootless by default.

This can happen if the window was mapped, redirected, damaged and
unredirected immediately, before the damage is processed by Xwayland.

Make sure to remove the dirty window from the damage list on unrealize
to prevent this from happening.

Credit goes to Adam Jackson <ajax@nwnk.net> and Daniel Stone
<daniel@fooishbar.org> for finding the root cause the issue.

Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
This commit is contained in:
Olivier Fourdan 2018-01-24 17:45:37 +01:00 committed by Adam Jackson
parent 29a5423abd
commit 3362422e84
1 changed files with 1 additions and 2 deletions
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3
hw/xwayland/xwayland.c
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@ -587,8 +587,7 @@ xwl_unrealize_window(WindowPtr window)
}
wl_surface_destroy(xwl_window->surface);
if (RegionNotEmpty(DamageRegion(xwl_window->damage)))
xorg_list_del(&xwl_window->link_damage);
xorg_list_del(&xwl_window->link_damage);
DamageUnregister(xwl_window->damage);
DamageDestroy(xwl_window->damage);
if (xwl_window->frame_callback)