Fix SIGSEGV if DbusExportHandle outlives exported object

igo95862 · igo95862 · commit 26a7100208e1 · 2025-12-21T20:00:48.000Z
Avoid exposing `SdBusInterface.slot` because the slot object
depends on `SdBusInterface-&gt;vtable`. Instead provide a method
to stop exporting.
diff --git a/src/sdbus/dbus_proxy_async_interface_base.py b/src/sdbus/dbus_proxy_async_interface_base.py
@@ -453,11 +453,8 @@ def new_proxy(
 class DbusExportHandle:
     def __init__(self, local_meta: DbusLocalObjectMeta):
         self._tasks = local_meta.tasks
-        self._dbus_slots: list[SdBusSlot] = [
-            i.slot
-            for i in local_meta.activated_interfaces
-            if i.slot is not None
-        ]
+        self._dbus_slots: list[SdBusSlot] = []
+        self._dbus_interfaces = local_meta.activated_interfaces
 
     async def __aenter__(self) -> DbusExportHandle:
         return self
@@ -485,5 +482,8 @@ def stop(self) -> None:
         for task in self._tasks:
             task.cancel("D-Bus export stopped")
 
+        for interface in self._dbus_interfaces:
+            interface._stop_export()
+
         for slot in self._dbus_slots:
             slot.close()
diff --git a/src/sdbus/sd_bus_internals.py b/src/sdbus/sd_bus_internals.py
@@ -49,7 +49,6 @@ def close(self) -> None:
 
 
 class SdBusInterface:
-    slot: Optional[SdBusSlot]
     method_list: list[object]
     method_dict: dict[bytes, object]
     property_list: list[object]
@@ -86,6 +85,9 @@ def add_signal(
     ) -> None:
         raise NotImplementedError(__STUB_ERROR)
 
+    def _stop_export(self) -> None:
+        raise NotImplementedError(__STUB_ERROR)
+
 
 class SdBusMessage:
     def append_data(self, signature: str, *args: DbusCompleteTypes) -> None:
diff --git a/src/sdbus/sd_bus_internals_interface.c b/src/sdbus/sd_bus_internals_interface.c
@@ -323,16 +323,23 @@ static PyObject* SdBusInterface_create_vtable(SdBusInterfaceObject* self, PyObje
         Py_RETURN_NONE;
 }
 
+static PyObject* SdBusInterface_stop_export(SdBusInterfaceObject* self, PyObject* Py_UNUSED(args)) {
+        Py_XDECREF(self->interface_slot);
+        self->interface_slot = NULL;
+
+        Py_RETURN_NONE;
+}
+
 static PyMethodDef SdBusInterface_methods[] = {
     {"add_method", (SD_BUS_PY_FUNC_TYPE)SdBusInterface_add_method, SD_BUS_PY_METH, PyDoc_STR("Add method to the D-Bus interface.")},
     {"add_property", (SD_BUS_PY_FUNC_TYPE)SdBusInterface_add_property, SD_BUS_PY_METH, PyDoc_STR("Add property to the D-Bus interface.")},
     {"add_signal", (SD_BUS_PY_FUNC_TYPE)SdBusInterface_add_signal, SD_BUS_PY_METH, PyDoc_STR("Add signal to the D-Bus interface.")},
     {"_create_vtable", (PyCFunction)SdBusInterface_create_vtable, METH_NOARGS, PyDoc_STR("Creates the vtable.")},
+    {"_stop_export", (PyCFunction)SdBusInterface_stop_export, METH_NOARGS, PyDoc_STR("Stop exporting object.")},
     {NULL, NULL, 0, NULL},
 };
 
-static PyMemberDef SdBusInterface_members[] = {{"slot", T_OBJECT, offsetof(SdBusInterfaceObject, interface_slot), READONLY, NULL},
-                                               {"method_list", T_OBJECT, offsetof(SdBusInterfaceObject, method_list), READONLY, NULL},
+static PyMemberDef SdBusInterface_members[] = {{"method_list", T_OBJECT, offsetof(SdBusInterfaceObject, method_list), READONLY, NULL},
                                                {"method_dict", T_OBJECT, offsetof(SdBusInterfaceObject, method_dict), READONLY, NULL},
                                                {"property_list", T_OBJECT, offsetof(SdBusInterfaceObject, property_list), READONLY, NULL},
                                                {"property_get_dict", T_OBJECT, offsetof(SdBusInterfaceObject, property_get_dict), READONLY, NULL},
diff --git a/test/test_sdbus_async.py b/test/test_sdbus_async.py
@@ -1008,6 +1008,28 @@ async def test_export_handle(self) -> None:
         with self.assertRaises(DbusUnknownObjectError):
             await test_object_connection.returns_none_method()
 
+    async def test_export_handle_lifetime(self) -> None:
+        test_object = TestInterface()
+        test_object_connection = TestInterface.new_proxy(
+            TEST_SERVICE_NAME, '/',
+        )
+        handle = test_object.export_to_dbus("/")
+        await test_object_connection.returns_none_method()
+
+        del test_object
+
+        handle.stop()
+
+        with self.assertRaises(DbusUnknownObjectError):
+            await test_object_connection.returns_none_method()
+
+        # Test idempotency
+        handle.stop()
+        handle.stop()
+
+        with self.assertRaises(DbusUnknownObjectError):
+            await test_object_connection.returns_none_method()
+
     def test_asyncio_run_different_loops(self) -> None:
         bus = self.bus
 
