Backport gh-120298 list_richcompare use after free

This backports the fix to #120298.
commit id b884536

Author: gpshead

Misc/NEWS.d/next/Core and Builtins/2024-06-10-10-42-48.gh-issue-120298.napREA.rst

@@ -0,0 +1,2 @@
+Fix use-after free in ``list_richcompare_impl`` which can be invoked via
+some specificly tailored evil input.

Objects/listobject.c

@@ -2757,7 +2757,14 @@ list_richcompare(PyObject *v, PyObject *w, int op)
     }
 
     /* Compare the final item again using the proper operator */
-    return PyObject_RichCompare(vl->ob_item[i], wl->ob_item[i], op);
+    PyObject *vitem = vl->ob_item[i];
+    PyObject *witem = wl->ob_item[i];
+    Py_INCREF(vitem);
+    Py_INCREF(witem);
+    PyObject *result = PyObject_RichCompare(vl->ob_item[i], wl->ob_item[i], op);
+    Py_DECREF(vitem);
+    Py_DECREF(witem);
+    return result;
 }
 
 /*[clinic input]