[3.12] gh-126405: fix use-after-free in _asyncio.Future.remove_done_callback (GH-126733) (#126737)

gh-126405: fix use-after-free in `_asyncio.Future.remove_done_callback` (GH-126733)
(cherry picked from commit 37c57df)

Co-authored-by: Kumar Aditya <[email protected]>

Author: miss-islington

Modules/_asynciomodule.c

@@ -1073,8 +1073,10 @@ _asyncio_Future_remove_done_callback_impl(FutureObj *self, PyTypeObject *cls,
 
     if (len == 1) {
         PyObject *cb_tup = PyList_GET_ITEM(self->fut_callbacks, 0);
+        Py_INCREF(cb_tup);
         int cmp = PyObject_RichCompareBool(
             PyTuple_GET_ITEM(cb_tup, 0), fn, Py_EQ);
+        Py_DECREF(cb_tup);
         if (cmp == -1) {
             return NULL;
         }