bpo-33989: Ensure that ms.key_compare is always initialized in list_sort_impl(). (GH-8710)

miss-islington · ZackerySpytz · web-flow · commit 0e73ea26a55a · 2019-02-21T00:05:22.000-08:00
(cherry picked from commit ebc793d) Co-authored-by: Zackery Spytz <zspytz@gmail.com>
diff --git a/Misc/NEWS.d/next/Core and Builtins/2018-08-08-20-52-55.bpo-33989.TkLBui.rst b/Misc/NEWS.d/next/Core and Builtins/2018-08-08-20-52-55.bpo-33989.TkLBui.rst
@@ -0,0 +1,2 @@
+Fix a possible crash in :meth:`list.sort` when sorting objects with
+``ob_type->tp_richcompare == NULL``.  Patch by Zackery Spytz.
diff --git a/Objects/listobject.c b/Objects/listobject.c
@@ -2279,6 +2279,9 @@ list_sort_impl(PyListObject *self, PyObject *keyfunc, int reverse)
             else if ((ms.key_richcompare = key_type->tp_richcompare) != NULL) {
                 ms.key_compare = unsafe_object_compare;
             }
+            else {
+                ms.key_compare = safe_object_compare;
+            }
         }
         else {
             ms.key_compare = safe_object_compare;

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	+Fix a possible crash in :meth:`list.sort` when sorting objects with
	`2`	+``ob_type->tp_richcompare == NULL``. Patch by Zackery Spytz.
Original file line number	Diff line number	Diff line change
`@@ -2279,6 +2279,9 @@ list_sort_impl(PyListObject self, PyObject keyfunc, int reverse)`
`2279`	`2279`	`else if ((ms.key_richcompare = key_type->tp_richcompare) != NULL) {`
`2280`	`2280`	`ms.key_compare = unsafe_object_compare;`
`2281`	`2281`	`}`
	`2282`	`+ else {`
	`2283`	`+ ms.key_compare = safe_object_compare;`
	`2284`	`+ }`
`2282`	`2285`	`}`
`2283`	`2286`	`else {`
`2284`	`2287`	`ms.key_compare = safe_object_compare;`