Fix bug

[ 1180997 ] lax error-checking in new-in-2.4 marshal stuff

which I'd assigned to Martin, but actually turned out to be easy to fix.

Also, a test.

Lib/test/test_marshal.py

@@ -211,6 +211,15 @@ class BugsTestCase(unittest.TestCase):
         self.assertEquals(marshal.loads(marshal.dumps(5, 0)), 5)
         self.assertEquals(marshal.loads(marshal.dumps(5, 1)), 5)
 
+    def test_fuzz(self):
+        # simple test that it's at least not *totally* trivial to
+        # crash from bad marshal data
+        for c in [chr(i) for i in range(256)]:
+            try:
+                marshal.loads(c)
+            except Exception:
+                pass
+
 def test_main():
     test_support.run_unittest(IntTestCase,
                               FloatTestCase,

Python/marshal.c

@@ -648,6 +648,10 @@ r_object(RFILE *p)
 
 	case TYPE_STRINGREF:
 		n = r_long(p);
+		if (n < 0 || n >= PyList_GET_SIZE(p->strings)) {
+			PyErr_SetString(PyExc_ValueError, "bad marshal data");
+			return NULL;
+		}
 		v = PyList_GET_ITEM(p->strings, n);
 		Py_INCREF(v);
 		return v;