Compositor: Fix nullptr dereferences in fromResource functions

If there was no resource for the given wl_resource*, don't try to dereference
it.

Change-Id: I3a27a5805699148bb26029e8b4179042c3c1117a
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>
Reviewed-by: Pier Luigi Fiorini <pierluigi.fiorini@liri.io>

2 files changed, 9 insertions, 3 deletions

diff --git a/src/compositor/extensions/qwaylandxdgshell.cpp b/src/compositor/extensions/qwaylandxdgshell.cpp
index 175caea62..90841b117 100644
--- a/src/compositor/extensions/qwaylandxdgshell.cpp
+++ b/src/compositor/extensions/qwaylandxdgshell.cpp
@@ -1127,7 +1127,9 @@ QWaylandSurfaceRole *QWaylandXdgToplevel::role()
  */
 QWaylandXdgToplevel *QWaylandXdgToplevel::fromResource(wl_resource *resource)
 {
-    return static_cast<QWaylandXdgToplevelPrivate *>(QWaylandXdgToplevelPrivate::Resource::fromResource(resource)->xdg_toplevel_object)->q_func();
+    if (auto *r = QWaylandXdgToplevelPrivate::Resource::fromResource(resource))
+        return static_cast<QWaylandXdgToplevelPrivate *>(r->xdg_toplevel_object)->q_func();
+    return nullptr;
 }
 
 /*!
@@ -2006,7 +2008,9 @@ void QWaylandXdgPositioner::xdg_positioner_set_offset(QtWaylandServer::xdg_posit
 
 QWaylandXdgPositioner *QWaylandXdgPositioner::fromResource(wl_resource *resource)
 {
-    return static_cast<QWaylandXdgPositioner *>(Resource::fromResource(resource)->xdg_positioner_object);
+    if (auto *r = Resource::fromResource(resource))
+        return static_cast<QWaylandXdgPositioner *>(r->xdg_positioner_object);
+    return nullptr;
 }
 
 Qt::Edges QWaylandXdgPositioner::convertToEdges(anchor anchor)
diff --git a/src/compositor/extensions/qwaylandxdgshellv6.cpp b/src/compositor/extensions/qwaylandxdgshellv6.cpp
index 648f2a1e1..a8b0d3914 100644
--- a/src/compositor/extensions/qwaylandxdgshellv6.cpp
+++ b/src/compositor/extensions/qwaylandxdgshellv6.cpp
@@ -1997,7 +1997,9 @@ void QWaylandXdgPositionerV6::zxdg_positioner_v6_set_offset(QtWaylandServer::zxd
 
 QWaylandXdgPositionerV6 *QWaylandXdgPositionerV6::fromResource(wl_resource *resource)
 {
-    return static_cast<QWaylandXdgPositionerV6 *>(Resource::fromResource(resource)->zxdg_positioner_v6_object);
+    if (auto *r = Resource::fromResource(resource))
+        return static_cast<QWaylandXdgPositionerV6 *>(r->zxdg_positioner_v6_object);
+    return nullptr;
 }
 
 QT_END_NAMESPACE