fix super() calls on unusual types (e.g. meta-types)

Carl Meyer · facebook-github-bot · commit c6386293fec5 · 2023-05-30T11:41:14.000-07:00
Summary: This bug was discovered in the upstream `LOAD_SUPER_ATTR` implementation in 3.12b1, and it also exists in the Cinder implementation. `_PyObject_GetMethod` checks whether the type has a non-standard `tp_getattro` (i.e. not `PyObject_GenericGetAttr`), and if so, refuses to attempt the load-method optimization. We didn't have this check in the `super()` optimization, causing incompatible behavior in the case of a `super()` lookup on a type with unusual `tp_getattro`, e.g. meta-types. Upstream fix is python/cpython#105094 Reviewed By: mpage Differential Revision: D46281340 fbshipit-source-id: 41aba762d3e2925042a3d897a690317ba2767cf2
diff --git a/Lib/test/test_super.py b/Lib/test/test_super.py
@@ -317,6 +317,15 @@ def test_super_init_leaks(self):
         for i in range(1000):
             super.__init__(sp, int, i)
 
+    def test_unusual_getattro(self):
+        class MyType(type):
+            pass
+
+        mytype = MyType("foo", (MyType,), {})
+        super(MyType, type(mytype)).__setattr__(mytype, "bar", 1)
+
+        self.assertEqual(mytype.bar, 1)
+
 
 if __name__ == "__main__":
     unittest.main()
diff --git a/Python/ceval.c b/Python/ceval.c
@@ -1724,6 +1724,9 @@ Ci_SuperLookupMethodOrAttr(PyThreadState *tstate,
         }
         return result;
     }
+    if (type->tp_getattro != PyObject_GenericGetAttr) {
+        meth_found = NULL;
+    }
     return Ci_Super_Lookup(type, self, name, NULL, meth_found);
 }
 

Original file line number	Diff line number	Diff line change
`@@ -1724,6 +1724,9 @@ Ci_SuperLookupMethodOrAttr(PyThreadState *tstate,`
`1724`	`1724`	`}`
`1725`	`1725`	`return result;`
`1726`	`1726`	`}`
	`1727`	`+ if (type->tp_getattro != PyObject_GenericGetAttr) {`
	`1728`	`+ meth_found = NULL;`
	`1729`	`+ }`
`1727`	`1730`	`return Ci_Super_Lookup(type, self, name, NULL, meth_found);`
`1728`	`1731`	`}`
`1729`	`1732`