The function `xwl_glamor_gbm_create_pixmap()` first creates a buffer
objects and then creates the xwl_pixmap from it.
However, `xwl_glamor_gbm_create_pixmap_for_bo()` is not called if the
buffer object creation fails, and `xwl_glamor_gbm_create_pixmap()`
simply returns `glamor_create_pixmap()`.
The problem with this is that if `xwl_glamor_gbm_create_pixmap_for_bo()`
is not called then neither is `xwl_pixmap_set_private()` and further
calls to `xwl_pixmap_get()` will return NULL and cause a NULL pointer
dereference if the return value is not checked:
#0 xwl_glamor_gbm_get_wl_buffer_for_pixmap ()
at hw/xwayland/xwayland-glamor-gbm.c:248
#1 xwl_window_post_damage () at hw/xwayland/xwayland.c:697
#2 xwl_display_post_damage () at hw/xwayland/xwayland.c:759
#3 block_handler () at hw/xwayland/xwayland.c:890
#4 BlockHandler () at dix/dixutils.c:388
#5 WaitForSomething () at os/WaitFor.c:201
#6 Dispatch () at dix/dispatch.c:421
#7 dix_main () at dix/main.c:276
#8 __libc_start_main () at ../csu/libc-start.c:308
#9 _start ()
(gdb) print xwl_pixmap
$1 = (struct xwl_pixmap *) 0x0
Make sure we check for `xwl_pixmap_get()` returned value where relevant
and fail gracefully if this is the case.
See also: https://gitlab.gnome.org/GNOME/mutter/issues/340
Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Reviewed-by: Marco Trevisan <mail@3v1n0.net>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
036794bebc