From a5f092f3c469b674b8d9ccbd4e4377230c9ac7cf Mon Sep 17 00:00:00 2001
From: Victor Stinner <vstinner@python.org>
Date: Thu, 29 Sep 2022 00:07:07 +0200
Subject: [PATCH] gh-97616: list_resize() checks for integer overflow (#97617)

Fix multiplying a list by an integer (list *= int): detect the
integer overflow when the new allocated length is close to the
maximum size.  Issue reported by Jordan Limor.

list_resize() now checks for integer overflow before multiplying the
new allocated length by the list item size (sizeof(PyObject*)).
---
 Lib/test/test_list.py                               | 13 +++++++++++++
 .../2022-09-28-17-09-37.gh-issue-97616.K1e3Xs.rst   |  3 +++
 Objects/listobject.c                                | 10 ++++++++--
 3 files changed, 24 insertions(+), 2 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Security/2022-09-28-17-09-37.gh-issue-97616.K1e3Xs.rst

diff --git a/Lib/test/test_list.py b/Lib/test/test_list.py
index d3da05ba84a..9aa6dd10956 100644
--- a/Lib/test/test_list.py
+++ b/Lib/test/test_list.py
@@ -96,6 +96,19 @@ class ListTest(list_tests.CommonTest):
         self.assertRaises((MemoryError, OverflowError), mul, lst, n)
         self.assertRaises((MemoryError, OverflowError), imul, lst, n)
 
+    def test_list_resize_overflow(self):
+        # gh-97616: test new_allocated * sizeof(PyObject*) overflow
+        # check in list_resize()
+        lst = [0] * 65
+        del lst[1:]
+        self.assertEqual(len(lst), 1)
+
+        size = ((2 ** (tuple.__itemsize__ * 8) - 1) // 2)
+        with self.assertRaises((MemoryError, OverflowError)):
+            lst * size
+        with self.assertRaises((MemoryError, OverflowError)):
+            lst *= size
+
     def test_repr_large(self):
         # Check the repr of large list objects
         def check(n):
diff --git a/Misc/NEWS.d/next/Security/2022-09-28-17-09-37.gh-issue-97616.K1e3Xs.rst b/Misc/NEWS.d/next/Security/2022-09-28-17-09-37.gh-issue-97616.K1e3Xs.rst
new file mode 100644
index 00000000000..721427fe646
--- /dev/null
+++ b/Misc/NEWS.d/next/Security/2022-09-28-17-09-37.gh-issue-97616.K1e3Xs.rst
@@ -0,0 +1,3 @@
+Fix multiplying a list by an integer (``list *= int``): detect the integer
+overflow when the new allocated length is close to the maximum size. Issue
+reported by Jordan Limor.  Patch by Victor Stinner.
diff --git a/Objects/listobject.c b/Objects/listobject.c
index 6005466f95f..2cb3de9f147 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -76,8 +76,14 @@ list_resize(PyListObject *self, Py_ssize_t newsize)
 
     if (newsize == 0)
         new_allocated = 0;
-    num_allocated_bytes = new_allocated * sizeof(PyObject *);
-    items = (PyObject **)PyMem_Realloc(self->ob_item, num_allocated_bytes);
+    if (new_allocated <= (size_t)PY_SSIZE_T_MAX / sizeof(PyObject *)) {
+        num_allocated_bytes = new_allocated * sizeof(PyObject *);
+        items = (PyObject **)PyMem_Realloc(self->ob_item, num_allocated_bytes);
+    }
+    else {
+        // integer overflow
+        items = NULL;
+    }
     if (items == NULL) {
         PyErr_NoMemory();
         return -1;