From: Martin Panter <vadmium+py@gmail.com>
Date: Sat, 14 Jan 2017 06:30:37 +0000 (+0000)
Subject: Issue #1621: Overflow should not be possible in listextend()
X-Git-Tag: v3.7.0a1~1559
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=94b39ceb736997eb924dc509ea0ef55f4a19c706;p=python

Issue #1621: Overflow should not be possible in listextend()
---

diff --git a/Objects/listobject.c b/Objects/listobject.c
index dcd7b5efe5..05dddfc6d7 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -804,6 +804,9 @@ listextend(PyListObject *self, PyObject *b)
             Py_RETURN_NONE;
         }
         m = Py_SIZE(self);
+        /* It should not be possible to allocate a list large enough to cause
+        an overflow on any relevant platform */
+        assert(m < PY_SSIZE_T_MAX - n);
         if (list_resize(self, m + n) < 0) {
             Py_DECREF(b);
             return NULL;