gh-136053: Check error for TYPE_SLICE in marshal.c (GH-136054)

akshat62 · web-flow · commit 30ba03ea8ed9 · 2025-06-29T10:07:24.000+03:00
Fix a possible crash when deserializing a large marshal data
(at least several GiBs) containing a slice.
diff --git a/Misc/NEWS.d/next/Security/2025-06-27-21-23-19.gh-issue-136053.QZxcee.rst b/Misc/NEWS.d/next/Security/2025-06-27-21-23-19.gh-issue-136053.QZxcee.rst
@@ -0,0 +1 @@
+:mod:`marshal`: fix a possible crash when deserializing :class:`slice` objects.
diff --git a/Python/marshal.c b/Python/marshal.c
@@ -1656,6 +1656,9 @@ r_object(RFILE *p)
     case TYPE_SLICE:
     {
         Py_ssize_t idx = r_ref_reserve(flag, p);
+        if (idx < 0) {
+            break;
+        }
         PyObject *stop = NULL;
         PyObject *step = NULL;
         PyObject *start = r_object(p);

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	+:mod:`marshal`: fix a possible crash when deserializing :class:`slice` objects.