complain when nbytes > buflen to fix possible buffer overflow (closes #20246)
diff --git a/Lib/test/test_socket.py b/Lib/test/test_socket.py
index 4a60be3..c7ad121 100644
--- a/Lib/test/test_socket.py
+++ b/Lib/test/test_socket.py
@@ -1620,6 +1620,16 @@
 
     _testRecvFromIntoMemoryview = _testRecvFromIntoArray
 
+    def testRecvFromIntoSmallBuffer(self):
+        # See issue #20246.
+        buf = bytearray(8)
+        self.assertRaises(ValueError, self.cli_conn.recvfrom_into, buf, 1024)
+
+    def _testRecvFromIntoSmallBuffer(self):
+        with test_support.check_py3k_warnings():
+            buf = buffer(MSG*2048)
+        self.serv_conn.send(buf)
+
 
 TIPC_STYPE = 2000
 TIPC_LOWER = 200