bpo-32869: Fix incorrect dst buffer size for MultiByteToWideChar (GH-5739)

miss-islington · izbyshev · web-flow · commit ca82e3c0ec4d · 2018-02-18T10:40:07.000-08:00
This function expects the destination buffer size to be given in wide characters, not bytes. (cherry picked from commit b3b4a9d) Co-authored-by: Alexey Izbyshev <izbyshev@users.noreply.github.com>
diff --git a/Python/fileutils.c b/Python/fileutils.c
@@ -1289,7 +1289,8 @@ _Py_fopen_obj(PyObject *path, const char *mode)
     if (wpath == NULL)
         return NULL;
 
-    usize = MultiByteToWideChar(CP_ACP, 0, mode, -1, wmode, sizeof(wmode));
+    usize = MultiByteToWideChar(CP_ACP, 0, mode, -1,
+                                wmode, Py_ARRAY_LENGTH(wmode));
     if (usize == 0) {
         PyErr_SetFromWindowsErr(0);
         return NULL;
