bpo-42814: Fix undefined behavior in Objects/genericaliasobject.c (GH-24073)

ZackerySpytz · web-flow · commit 5d3553b0a895 · 2021-01-03T13:18:25.000+01:00
In is_typing_name(), va_end() is not always called before the
function returns.  It is undefined behavior to call va_start()
without also calling va_end().
diff --git a/Misc/NEWS.d/next/Core and Builtins/2021-01-03-04-41-25.bpo-42814.sDvVbb.rst b/Misc/NEWS.d/next/Core and Builtins/2021-01-03-04-41-25.bpo-42814.sDvVbb.rst
@@ -0,0 +1 @@
+Fix undefined behavior in ``Objects/genericaliasobject.c``.
diff --git a/Objects/genericaliasobject.c b/Objects/genericaliasobject.c
@@ -173,6 +173,7 @@ is_typing_name(PyObject *obj, int num, ...)
             break;
         }
     }
+    va_end(names);
     if (!hit) {
         return 0;
     }
@@ -184,7 +185,6 @@ is_typing_name(PyObject *obj, int num, ...)
         && _PyUnicode_EqualToASCIIString(module, "typing");
     Py_DECREF(module);
     
-    va_end(names);
     return res;
 }
 

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	+Fix undefined behavior in ``Objects/genericaliasobject.c``.
Original file line number	Diff line number	Diff line change
`@@ -173,6 +173,7 @@ is_typing_name(PyObject *obj, int num, ...)`
`173`	`173`	`break;`
`174`	`174`	`}`
`175`	`175`	`}`
	`176`	`+ va_end(names);`
`176`	`177`	`if (!hit) {`
`177`	`178`	`return 0;`
`178`	`179`	`}`
`@@ -184,7 +185,6 @@ is_typing_name(PyObject *obj, int num, ...)`
`184`	`185`	`&& _PyUnicode_EqualToASCIIString(module, "typing");`
`185`	`186`	`Py_DECREF(module);`
`186`	`187`
`187`		`- va_end(names);`
`188`	`188`	`return res;`
`189`	`189`	`}`
`190`	`190`