gh-139122: Propagate SafeUUID lookup errors in is_safe getter

Author: 1st1

Lib/test/test_uuid.py

@@ -1753,6 +1753,28 @@ def time_func(self):
 
 @unittest.skipUnless(c_uuid, "requires the C _uuid module")
 class TestCImplementationCompat(unittest.TestCase):
+    def test_is_safe_lookup_error(self):
+        # Force the lazy SafeUUID lookup to fail before it is cached. The getter
+        # must propagate AttributeError and recover when the attribute returns.
+        # Run in a subprocess because using the failed lookup can crash Python.
+        assert_python_ok('-c', textwrap.dedent('''
+            import uuid
+
+            obj = uuid.UUID(int=1)
+            SafeUUID = uuid.SafeUUID
+            del uuid.SafeUUID
+            try:
+                try:
+                    obj.is_safe
+                except AttributeError as exc:
+                    assert 'SafeUUID' in str(exc)
+                else:
+                    raise AssertionError('SafeUUID lookup unexpectedly succeeded')
+            finally:
+                uuid.SafeUUID = SafeUUID
+            assert obj.is_safe is SafeUUID.unknown
+        '''))
+
     def test_compatibility(self):
         import uuid
 

Modules/_uuidmodule.c

@@ -1106,6 +1106,9 @@ Uuid_get_is_safe(PyObject *op, void *Py_UNUSED(closure))
     uuid_state *state = get_uuid_state_by_cls(Py_TYPE(self));
     if (self->is_safe == NULL) {
         PyObject *SafeUUID = get_SafeUUID(state);
+        if (SafeUUID == NULL) {
+            return NULL;
+        }
         PyObject *ret = PyObject_GetAttrString(SafeUUID, "unknown");
         Py_DECREF(SafeUUID);
         return ret;