pythonGH-96187: Prevent _PyCode_GetExtra to return garbage for negati…

…ve indexes (pythonGH-96188)
swtaarrs · Aug 23, 2022 · 16ebae4 · 16ebae4
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diff --git a/Misc/NEWS.d/next/Core and Builtins/2022-08-22-21-33-28.gh-issue-96187.W_6SRG.rst b/Misc/NEWS.d/next/Core and Builtins/2022-08-22-21-33-28.gh-issue-96187.W_6SRG.rst
@@ -0,0 +1,2 @@
+Fixed a bug that caused ``_PyCode_GetExtra`` to return garbage for negative
+indexes. Patch by Pablo Galindo
diff --git a/Objects/codeobject.c b/Objects/codeobject.c
@@ -1339,7 +1339,7 @@ _PyCode_GetExtra(PyObject *code, Py_ssize_t index, void **extra)
     PyCodeObject *o = (PyCodeObject*) code;
     _PyCodeObjectExtra *co_extra = (_PyCodeObjectExtra*) o->co_extra;
 
-    if (co_extra == NULL || co_extra->ce_size <= index) {
+    if (co_extra == NULL || index < 0 || co_extra->ce_size <= index) {
         *extra = NULL;
         return 0;
     }