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xwayland: do not crash if gbm_bo_create() fails

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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>
This commit is contained in:
Olivier Fourdan 2018-10-19 16:04:32 +02:00 committed by Adam Jackson
parent 32abc22288
commit 036794bebc
1 changed files with 6 additions and 0 deletions
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6
hw/xwayland/xwayland-glamor-gbm.c
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@ -260,6 +260,9 @@ xwl_glamor_gbm_get_wl_buffer_for_pixmap(PixmapPtr pixmap,
uint64_t modifier;
int i;
if (xwl_pixmap == NULL)
return NULL;
if (xwl_pixmap->buffer) {
/* Buffer already exists. Return it and inform caller if interested. */
if (created)
@ -510,6 +513,9 @@ glamor_egl_fds_from_pixmap(ScreenPtr screen, PixmapPtr pixmap, int *fds,
xwl_pixmap = xwl_pixmap_get(pixmap);
if (xwl_pixmap == NULL)
return 0;
if (!xwl_pixmap->bo)
return 0;