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bpo-35615: Fix crashes when copying a Weak{Key,Value}Dictionary. (GH-… · python/cpython@96d37db · GitHub

  1. python
  2. cpython

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Commit 96d37db

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ltfish
authored and
pitrou
committed
bpo-35615: Fix crashes when copying a Weak{Key,Value}Dictionary. (GH-11384)
Protect dict iterations by wrapping them with _IterationGuard in the following methods: - WeakValueDictionary.copy() - WeakValueDictionary.__deepcopy__() - WeakKeyDictionary.copy() - WeakKeyDictionary.__deepcopy__()
1 parent df8d2cd commit 96d37db

3 files changed

Lines changed: 105 additions & 16 deletions

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‎Lib/test/test_weakref.py‎

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Original file line numberDiff line numberDiff line change
@@ -8,6 +8,7 @@
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import copy
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import threading
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import time
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import random
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from test import support
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from test.support import script_helper
@@ -1688,6 +1689,87 @@ def test_threaded_weak_valued_consistency(self):
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self.assertEqual(len(d), 1)
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o = None # lose ref
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def check_threaded_weak_dict_copy(self, type_, deepcopy):
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# `type_` should be either WeakKeyDictionary or WeakValueDictionary.
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# `deepcopy` should be either True or False.
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exc = []
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class DummyKey:
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def __init__(self, ctr):
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self.ctr = ctr
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class DummyValue:
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def __init__(self, ctr):
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self.ctr = ctr
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def dict_copy(d, exc):
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try:
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if deepcopy is True:
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_ = copy.deepcopy(d)
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else:
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_ = d.copy()
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except Exception as ex:
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exc.append(ex)
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def pop_and_collect(lst):
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gc_ctr = 0
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while lst:
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i = random.randint(0, len(lst) - 1)
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gc_ctr += 1
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lst.pop(i)
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if gc_ctr % 10000 == 0:
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gc.collect() # just in case
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self.assertIn(type_, (weakref.WeakKeyDictionary, weakref.WeakValueDictionary))
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d = type_()
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keys = []
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values = []
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# Initialize d with many entries
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for i in range(70000):
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k, v = DummyKey(i), DummyValue(i)
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keys.append(k)
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values.append(v)
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d[k] = v
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del k
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del v
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t_copy = threading.Thread(target=dict_copy, args=(d, exc,))
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if type_ is weakref.WeakKeyDictionary:
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t_collect = threading.Thread(target=pop_and_collect, args=(keys,))
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else: # weakref.WeakValueDictionary
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t_collect = threading.Thread(target=pop_and_collect, args=(values,))
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t_copy.start()
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t_collect.start()
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t_copy.join()
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t_collect.join()
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# Test exceptions
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if exc:
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raise exc[0]
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def test_threaded_weak_key_dict_copy(self):
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# Issue #35615: Weakref keys or values getting GC'ed during dict
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# copying should not result in a crash.
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self.check_threaded_weak_dict_copy(weakref.WeakKeyDictionary, False)
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def test_threaded_weak_key_dict_deepcopy(self):
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# Issue #35615: Weakref keys or values getting GC'ed during dict
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# copying should not result in a crash.
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self.check_threaded_weak_dict_copy(weakref.WeakKeyDictionary, True)
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def test_threaded_weak_value_dict_copy(self):
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# Issue #35615: Weakref keys or values getting GC'ed during dict
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# copying should not result in a crash.
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self.check_threaded_weak_dict_copy(weakref.WeakValueDictionary, False)
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def test_threaded_weak_value_dict_deepcopy(self):
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# Issue #35615: Weakref keys or values getting GC'ed during dict
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# copying should not result in a crash.
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self.check_threaded_weak_dict_copy(weakref.WeakValueDictionary, True)
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16911773

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from test import mapping_tests
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‎Lib/weakref.py‎

Lines changed: 20 additions & 16 deletions
Original file line numberDiff line numberDiff line change
@@ -171,10 +171,11 @@ def copy(self):
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if self._pending_removals:
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self._commit_removals()
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new = WeakValueDictionary()
174-
for key, wr in self.data.items():
175-
o = wr()
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if o is not None:
177-
new[key] = o
174+
with _IterationGuard(self):
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for key, wr in self.data.items():
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o = wr()
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if o is not None:
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new[key] = o
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return new
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180181
__copy__ = copy
@@ -184,10 +185,11 @@ def __deepcopy__(self, memo):
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if self._pending_removals:
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self._commit_removals()
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new = self.__class__()
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for key, wr in self.data.items():
188-
o = wr()
189-
if o is not None:
190-
new[deepcopy(key, memo)] = o
188+
with _IterationGuard(self):
189+
for key, wr in self.data.items():
190+
o = wr()
191+
if o is not None:
192+
new[deepcopy(key, memo)] = o
191193
return new
192194

193195
def get(self, key, default=None):
@@ -408,21 +410,23 @@ def __setitem__(self, key, value):
408410

409411
def copy(self):
410412
new = WeakKeyDictionary()
411-
for key, value in self.data.items():
412-
o = key()
413-
if o is not None:
414-
new[o] = value
413+
with _IterationGuard(self):
414+
for key, value in self.data.items():
415+
o = key()
416+
if o is not None:
417+
new[o] = value
415418
return new
416419

417420
__copy__ = copy
418421

419422
def __deepcopy__(self, memo):
420423
from copy import deepcopy
421424
new = self.__class__()
422-
for key, value in self.data.items():
423-
o = key()
424-
if o is not None:
425-
new[o] = deepcopy(value, memo)
425+
with _IterationGuard(self):
426+
for key, value in self.data.items():
427+
o = key()
428+
if o is not None:
429+
new[o] = deepcopy(value, memo)
426430
return new
427431

428432
def get(self, key, default=None):

‎Misc/NEWS.d/next/Library/2018-12-30-20-00-05.bpo-35615.Uz1SVh.rst‎

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@@ -0,0 +1,3 @@
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:mod:`weakref`: Fix a RuntimeError when copying a WeakKeyDictionary or a
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WeakValueDictionary, due to some keys or values disappearing while
3+
iterating.

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