wayland/pointer-gestures: Fix crash in get_*_gesture after pointer is destroyed

Properly handle cases where the pointer object has already been
destroyed to prevent the compositor from crashing with a null pointer
dereference when a client invokes a get_*_gesture method after the
pointer object is destroyed e.g. when the current login session is not on
foreground.

Closes: https://gitlab.gnome.org/GNOME/mutter/-/issues/2237
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2690>

3 files changed, 27 insertions, 15 deletions

diff --git a/src/wayland/meta-wayland-pointer-gesture-hold.c b/src/wayland/meta-wayland-pointer-gesture-hold.c
index 90c63cd25..5ccc42407 100644
--- a/src/wayland/meta-wayland-pointer-gesture-hold.c
+++ b/src/wayland/meta-wayland-pointer-gesture-hold.c
@@ -139,15 +139,19 @@ meta_wayland_pointer_gesture_hold_create_new_resource (MetaWaylandPointer *point
   MetaWaylandPointerClient *pointer_client;
   struct wl_resource *res;
 
-  pointer_client = meta_wayland_pointer_get_pointer_client (pointer, client);
-  g_return_if_fail (pointer_client != NULL);
-
   res = wl_resource_create (client, &zwp_pointer_gesture_hold_v1_interface,
                             wl_resource_get_version (pointer_resource), id);
   wl_resource_set_implementation (res, &pointer_gesture_hold_interface, pointer,
                                   meta_wayland_pointer_unbind_pointer_client_resource);
-  wl_list_insert (&pointer_client->hold_gesture_resources,
-                  wl_resource_get_link (res));
+
+  if (pointer)
+    {
+      pointer_client = meta_wayland_pointer_get_pointer_client (pointer, client);
+      g_return_if_fail (pointer_client != NULL);
+
+      wl_list_insert (&pointer_client->hold_gesture_resources,
+                      wl_resource_get_link (res));
+    }
 }
 
 void
diff --git a/src/wayland/meta-wayland-pointer-gesture-pinch.c b/src/wayland/meta-wayland-pointer-gesture-pinch.c
index 32a6bad69..16f106a76 100644
--- a/src/wayland/meta-wayland-pointer-gesture-pinch.c
+++ b/src/wayland/meta-wayland-pointer-gesture-pinch.c
@@ -170,15 +170,19 @@ meta_wayland_pointer_gesture_pinch_create_new_resource (MetaWaylandPointer *poin
   MetaWaylandPointerClient *pointer_client;
   struct wl_resource *res;
 
-  pointer_client = meta_wayland_pointer_get_pointer_client (pointer, client);
-  g_return_if_fail (pointer_client != NULL);
-
   res = wl_resource_create (client, &zwp_pointer_gesture_pinch_v1_interface,
                             wl_resource_get_version (gestures_resource), id);
   wl_resource_set_implementation (res, &pointer_gesture_pinch_interface, pointer,
                                   meta_wayland_pointer_unbind_pointer_client_resource);
-  wl_list_insert (&pointer_client->pinch_gesture_resources,
-                  wl_resource_get_link (res));
+
+  if (pointer)
+    {
+      pointer_client = meta_wayland_pointer_get_pointer_client (pointer, client);
+      g_return_if_fail (pointer_client != NULL);
+
+      wl_list_insert (&pointer_client->pinch_gesture_resources,
+                      wl_resource_get_link (res));
+    }
 }
 
 void
diff --git a/src/wayland/meta-wayland-pointer-gesture-swipe.c b/src/wayland/meta-wayland-pointer-gesture-swipe.c
index dc7abb3c8..924a9ded1 100644
--- a/src/wayland/meta-wayland-pointer-gesture-swipe.c
+++ b/src/wayland/meta-wayland-pointer-gesture-swipe.c
@@ -166,15 +166,19 @@ meta_wayland_pointer_gesture_swipe_create_new_resource (MetaWaylandPointer *poin
   MetaWaylandPointerClient *pointer_client;
   struct wl_resource *res;
 
-  pointer_client = meta_wayland_pointer_get_pointer_client (pointer, client);
-  g_return_if_fail (pointer_client != NULL);
-
   res = wl_resource_create (client, &zwp_pointer_gesture_swipe_v1_interface,
                             wl_resource_get_version (pointer_resource), id);
   wl_resource_set_implementation (res, &pointer_gesture_swipe_interface, pointer,
                                   meta_wayland_pointer_unbind_pointer_client_resource);
-  wl_list_insert (&pointer_client->swipe_gesture_resources,
-                  wl_resource_get_link (res));
+
+  if (pointer)
+    {
+      pointer_client = meta_wayland_pointer_get_pointer_client (pointer, client);
+      g_return_if_fail (pointer_client != NULL);
+
+      wl_list_insert (&pointer_client->swipe_gesture_resources,
+                      wl_resource_get_link (res));
+    }
 }
 
 void