[3.11] gh-99184: Bypass instance attribute access in repr of `weakr…

…ef.ref` (GH-99244) (#103789)

gh-99184: Bypass instance attribute access in `repr` of `weakref.ref` (GH-99244)
(cherry picked from commit 58b6be3)

Co-authored-by: Nikita Sobolev <mail@sobolevn.me>

Lib/test/test_weakref.py

@@ -116,6 +116,17 @@ def test_basic_ref(self):
         del o
         repr(wr)
 
+    def test_repr_failure_gh99184(self):
+        class MyConfig(dict):
+            def __getattr__(self, x):
+                return self[x]
+
+        obj = MyConfig(offset=5)
+        obj_weakref = weakref.ref(obj)
+
+        self.assertIn('MyConfig', repr(obj_weakref))
+        self.assertIn('MyConfig', str(obj_weakref))
+
     def test_basic_callback(self):
         self.check_basic_callback(C)
         self.check_basic_callback(create_function)

Misc/NEWS.d/next/Core and Builtins/2022-11-08-12-36-25.gh-issue-99184.KIaqzz.rst

@@ -0,0 +1,2 @@
+Bypass instance attribute access of ``__name__`` in ``repr`` of
+:class:`weakref.ref`.

Objects/weakrefobject.c

@@ -170,10 +170,7 @@ weakref_repr(PyWeakReference *self)
     }
 
     Py_INCREF(obj);
-    if (_PyObject_LookupAttr(obj, &_Py_ID(__name__), &name) < 0) {
-        Py_DECREF(obj);
-        return NULL;
-    }
+    name = _PyObject_LookupSpecial(obj, &_Py_ID(__name__));
     if (name == NULL || !PyUnicode_Check(name)) {
         repr = PyUnicode_FromFormat(
             "<weakref at %p; to '%s' at %p>",