gh-93627: Align Python implementation of pickle with C implementation of pickle

Lib/pickle.py

@@ -396,6 +396,8 @@ def decode_long(data):
  return int.from_bytes(data, byteorder='little', signed=True)
 
 
+_NoValue = object()
+
 # Pickling machinery
 
 class _Pickler:
@@ -542,8 +544,8 @@ def save(self, obj, save_persistent_id=True):
  return
 
  rv = NotImplemented
- reduce = getattr(self, "reducer_override", None)
- if reduce is not None:
+ reduce = getattr(self, "reducer_override", _NoValue)
+ if reduce is not _NoValue:
  rv = reduce(obj)
 
  if rv is NotImplemented:
@@ -556,8 +558,8 @@ def save(self, obj, save_persistent_id=True):
 
  # Check private dispatch table if any, or else
  # copyreg.dispatch_table
- reduce = getattr(self, 'dispatch_table', dispatch_table).get(t)
- if reduce is not None:
+ reduce = getattr(self, 'dispatch_table', dispatch_table).get(t, _NoValue)
+ if reduce is not _NoValue:
  rv = reduce(obj)
  else:
  # Check for a class with a custom metaclass; treat as regular
@@ -567,12 +569,12 @@ def save(self, obj, save_persistent_id=True):
  return
 
  # Check for a __reduce_ex__ method, fall back to __reduce__
- reduce = getattr(obj, "__reduce_ex__", None)
- if reduce is not None:
+ reduce = getattr(obj, "__reduce_ex__", _NoValue)
+ if reduce is not _NoValue:
  rv = reduce(self.proto)
  else:
- reduce = getattr(obj, "__reduce__", None)
- if reduce is not None:
+ reduce = getattr(obj, "__reduce__", _NoValue)
+ if reduce is not _NoValue:
  rv = reduce()
  else:
  raise PicklingError("Can't pickle %r object: %r" %
@@ -1705,8 +1707,8 @@ def load_build(self):
  stack = self.stack
  state = stack.pop()
  inst = stack[-1]
- setstate = getattr(inst, "__setstate__", None)
- if setstate is not None:
+ setstate = getattr(inst, "__setstate__", _NoValue)
+ if setstate is not _NoValue:
  setstate(state)
  return
  slotstate = None

Lib/test/pickletester.py

@@ -2408,6 +2408,22 @@ def test_reduce_calls_base(self):
  y = self.loads(s)
  self.assertEqual(y._reduce_called, 1)
 
+ def test_reduce_ex_None(self):
+ c = REX_None()
+ with self.assertRaises(TypeError):
+ self.dumps(c)
+
+ def test_reduce_None(self):
+ c = R_None()
+ with self.assertRaises(TypeError):
+ self.dumps(c)
+
+ def test_pickle_setstate_None(self):
+ c = C_None_setstate()
+ p = self.dumps(c)
+ with self.assertRaises(TypeError):
+ self.loads(p)
+
  @no_tracing
  def test_bad_getattr(self):
  # Issue #3514: crash when there is an infinite loop in __getattr__
@@ -3349,6 +3365,21 @@ def __setstate__(self, state):
  def __reduce__(self):
  return type(self), (), self.state
 
+class REX_None:
+ """ Setting __reduce_ex__ to None should fail """
+ __reduce_ex__ = None
+
+class R_None:
+ """ Setting __reduce__ to None should fail """
+ __reduce__ = None
+
+class C_None_setstate:
+ """ Setting __setstate__ to None should fail """
+ def __getstate__(self):
+ return 1
+
+ __setstate__ = None
+
 
 # Test classes for newobj
 
@@ -3752,6 +3783,25 @@ def test_unpickling_buffering_readline(self):
  unpickler = self.unpickler_class(f)
  self.assertEqual(unpickler.load(), data)
 
+ def test_pickle_invalid_reducer_override(self):
+ # gh-103035
+ obj = object()
+
+ f = io.BytesIO()
+ class MyPickler(self.pickler_class):
+ pass
+ pickler = MyPickler(f)
+ pickler.dump(obj)
+
+ pickler.clear_memo()
+ pickler.reducer_override = None
+ with self.assertRaises(TypeError):
+ pickler.dump(obj)
+
+ pickler.clear_memo()
+ pickler.reducer_override = 10
+ with self.assertRaises(TypeError):
+ pickler.dump(obj)
 
 # Tests for dispatch_table attribute
 
@@ -3914,6 +3964,15 @@ def dumps(obj, protocol=None):
 
  self._test_dispatch_table(dumps, dt)
 
+ def test_dispatch_table_None_item(self):
+ # gh-93627
+ obj = object()
+ f = io.BytesIO()
+ pickler = self.pickler_class(f)
+ pickler.dispatch_table ={type(obj): None}
+ with self.assertRaises(TypeError):
+ pickler.dump(obj)
+
  def _test_dispatch_table(self, dumps, dispatch_table):
  def custom_load_dump(obj):
  return pickle.loads(dumps(obj, 0))

Misc/NEWS.d/next/Core and Builtins/2023-03-26-19-11-10.gh-issue-93627.0UgwBL.rst

@@ -0,0 +1 @@
+Update the Python pickle module implementation to match the C implementation of the pickle module. For objects setting reduction methods like :meth:`~object.__reduce_ex__` or :meth:`~object.__reduce__` to ``None``, pickling will result in a :exc:`TypeError`.