bpo-37013: Fix the error handling in socket.if_indextoname() (GH-13503)

* Fix a crash when pass UINT_MAX.
* Fix an integer overflow on 64-bit non-Windows platforms.

1 files changed, 11 insertions, 5 deletions

diff --git a/Modules/socketmodule.c b/Modules/socketmodule.c
index 9ac2001..0a0e0e7 100644
--- a/Modules/socketmodule.c
+++ b/Modules/socketmodule.c
@@ -7071,17 +7071,23 @@ _socket_socket_if_nametoindex_impl(PySocketSockObject *self, PyObject *oname)
 static PyObject *
 socket_if_indextoname(PyObject *self, PyObject *arg)
 {
+    unsigned long index_long = PyLong_AsUnsignedLong(arg);
+    if (index_long == (unsigned long) -1 && PyErr_Occurred()) {
+        return NULL;
+    }
+
 #ifdef MS_WINDOWS
-    NET_IFINDEX index;
+    NET_IFINDEX index = (NET_IFINDEX)index_long;
 #else
-    unsigned long index;
+    unsigned int index = (unsigned int)index_long;
 #endif
-    char name[IF_NAMESIZE + 1];
 
-    index = PyLong_AsUnsignedLong(arg);
-    if (index == (unsigned long) -1)
+    if ((unsigned long)index != index_long) {
+        PyErr_SetString(PyExc_OverflowError, "index is too large");
         return NULL;
+    }
 
+    char name[IF_NAMESIZE + 1];
     if (if_indextoname(index, name) == NULL) {
         PyErr_SetFromErrno(PyExc_OSError);
         return NULL;