cap the block size to 8 MB.

Author: rmmancom

Lib/_pyio.py

@@ -241,7 +241,7 @@ def open(file, mode="r", buffering=-1, encoding=None, errors=None,
             buffering = -1
             line_buffering = True
         if buffering < 0:
-            buffering = max(raw._blksize, DEFAULT_BUFFER_SIZE)
+            buffering = max(min(raw._blksize, 8192 * 1024), DEFAULT_BUFFER_SIZE)
         if buffering < 0:
             raise ValueError("invalid buffering size")
         if buffering == 0:

Modules/_io/_iomodule.c

@@ -367,6 +367,10 @@ _io_open_impl(PyObject *module, PyObject *file, const char *mode,
         if (blksize_obj == NULL)
             goto error;
         buffering = PyLong_AsLong(blksize_obj);
+        if (buffering > 8192 * 1024)
+        {
+            buffering = 8192 * 1024;
+        }
         if (buffering < DEFAULT_BUFFER_SIZE)
         {
             buffering = DEFAULT_BUFFER_SIZE;