[Python-checkins] [3.10] GH-96187: Prevent _PyCode_GetExtra to return garbage for negative indexes (GH-96188). (#96210)

[pablogsal]

https://github.com/python/cpython/commit/a6c3f6d34792c5f9dc296ce8329938b7b2b02ea9
commit: a6c3f6d34792c5f9dc296ce8329938b7b2b02ea9
branch: 3.10
author: Pablo Galindo Salgado <Pablogsal at gmail.com>
committer: pablogsal <Pablogsal at gmail.com>
date: 2022-08-23T15:58:25+01:00
summary:

[3.10] GH-96187: Prevent _PyCode_GetExtra to return garbage for negative indexes (GH-96188). (#96210)

(cherry picked from commit 16ebae4cd4029205d932751f26c719c6cb8a6e92)

Co-authored-by: Pablo Galindo Salgado <Pablogsal at gmail.com>

files:
A Misc/NEWS.d/next/Core and Builtins/2022-08-22-21-33-28.gh-issue-96187.W_6SRG.rst
M Objects/codeobject.c

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
new file mode 100644
index 000000000000..fd194faa6854
--- /dev/null
+++ 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
index 976cec584e9f..390b76cafd51 100644
--- a/Objects/codeobject.c
+++ b/Objects/codeobject.c
@@ -1304,7 +1304,7 @@ _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;
     }