[3.10] gh-101765: Fix SystemError / segmentation fault in iter `__reduce__` when internal access of `builtins.__dict__` exhausts the iterator (GH-101769) (#102229)

(cherry picked from commit 54dfa14c5a94b893b67a4d9e9e403ff538ce9023)

1 files changed, 16 insertions, 6 deletions

diff --git a/Objects/iterobject.c b/Objects/iterobject.c
index e493e41..980c04b 100644
--- a/Objects/iterobject.c
+++ b/Objects/iterobject.c
@@ -104,11 +104,16 @@ PyDoc_STRVAR(length_hint_doc, "Private method returning an estimate of len(list(
 static PyObject *
 iter_reduce(seqiterobject *it, PyObject *Py_UNUSED(ignored))
 {
+    PyObject *iter = _PyEval_GetBuiltinId(&PyId_iter);
+
+    /* _PyEval_GetBuiltinId can invoke arbitrary code,
+     * call must be before access of iterator pointers.
+     * see issue #101765 */
+
     if (it->it_seq != NULL)
-        return Py_BuildValue("N(O)n", _PyEval_GetBuiltinId(&PyId_iter),
-                             it->it_seq, it->it_index);
+        return Py_BuildValue("N(O)n", iter, it->it_seq, it->it_index);
     else
-        return Py_BuildValue("N(())", _PyEval_GetBuiltinId(&PyId_iter));
+        return Py_BuildValue("N(())", iter);
 }
 
 PyDoc_STRVAR(reduce_doc, "Return state information for pickling.");
@@ -243,11 +248,16 @@ calliter_iternext(calliterobject *it)
 static PyObject *
 calliter_reduce(calliterobject *it, PyObject *Py_UNUSED(ignored))
 {
+    PyObject *iter = _PyEval_GetBuiltinId(&PyId_iter);
+
+    /* _PyEval_GetBuiltinId can invoke arbitrary code,
+     * call must be before access of iterator pointers.
+     * see issue #101765 */
+
     if (it->it_callable != NULL && it->it_sentinel != NULL)
-        return Py_BuildValue("N(OO)", _PyEval_GetBuiltinId(&PyId_iter),
-                             it->it_callable, it->it_sentinel);
+        return Py_BuildValue("N(OO)", iter, it->it_callable, it->it_sentinel);
     else
-        return Py_BuildValue("N(())", _PyEval_GetBuiltinId(&PyId_iter));
+        return Py_BuildValue("N(())", iter);
 }
 
 static PyMethodDef calliter_methods[] = {