Issue #17872: Fix a segfault in marshal.load() when input stream returns

more bytes than requested.

1 files changed, 12 insertions, 0 deletions

diff --git a/Lib/test/test_marshal.py b/Lib/test/test_marshal.py
index 292746b..ab06237 100644
--- a/Lib/test/test_marshal.py
+++ b/Lib/test/test_marshal.py
@@ -2,6 +2,7 @@
 
 from test import support
 import array
+import io
 import marshal
 import sys
 import unittest
@@ -259,6 +260,17 @@ class BugsTestCase(unittest.TestCase):
         unicode_string = 'T'
         self.assertRaises(TypeError, marshal.loads, unicode_string)
 
+    def test_bad_reader(self):
+        class BadReader(io.BytesIO):
+            def read(self, n=-1):
+                b = super().read(n)
+                if n is not None and n > 4:
+                    b += b' ' * 10**6
+                return b
+        for value in (1.0, 1j, b'0123456789', '0123456789'):
+            self.assertRaises(ValueError, marshal.load,
+                              BadReader(marshal.dumps(value)))
+
     def _test_eof(self):
         data = marshal.dumps(("hello", "dolly", None))
         for i in range(len(data)):