gh-97616: list_resize() checks for integer overflow (GH-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*)).
(cherry picked from commit a5f092f3c469b674b8d9ccbd4e4377230c9ac7cf)

Co-authored-by: Victor Stinner <vstinner@python.org>

1 files changed, 8 insertions, 2 deletions

diff --git a/Objects/listobject.c b/Objects/listobject.c
index 329fd1f..484d374 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -77,8 +77,14 @@ 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;