[3.13] gh-148660: Fix use-after-free in OrderedDict.copy() on reentrant mutation (GH-151573)#152542
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…eentrant mutation (pythonGH-151573) OrderedDict.copy() walks the internal linked list while building the new dict. The loop body can run arbitrary Python (a key's __eq__/__hash__, or a subclass __getitem__/__setitem__) which can clear the source dict and free the nodes being iterated. Detect this the same way OrderedDict.__eq__ already does (pythongh-119004): snapshot od_state before the loop, hold a strong reference to the key and read the hash before any reentrant call, and raise RuntimeError if the state changed before advancing to the next node. (cherry picked from commit 7d128e3)
This was referenced Jun 29, 2026
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OrderedDict.copy() walks the internal linked list while building the new
dict. The loop body can run arbitrary Python (a key's
__eq__/__hash__, ora subclass
__getitem__/__setitem__) which can clear the source dict andfree the nodes being iterated.
Detect this the same way
OrderedDict.__eq__already does (gh-119004):snapshot od_state before the loop, hold a strong reference to the key and
read the hash before any reentrant call, and raise RuntimeError if the
state changed before advancing to the next node.
(cherry picked from commit 7d128e3)
Manual backport notes (3.13): The test additions and NEWS entry applied cleanly; only
Objects/odictobject.cneeded adaptation because 3.13'sodict_copyis hand-written (not Argument Clinic) and predates the free-threading refactor. The cherry-pick conflict was resolved to 3.13's idioms:odis already typedPyODictObject *, so_PyODictObject_CAST(od)->od_statebecomesod->od_state; the lock-held insert helper_PyODict_SetItem_KnownHash_LockHeld()becomes the plain_PyODict_SetItem_KnownHash(); and(PyObject *)odcasts were added on thePyODict_GetItemWithError()/PyObject_GetItem()calls. The fix logic is otherwise identical.test_ordered_dictpasses in full (run=299), including the newtest_issue148660_*cases on both the C and pure-Python OrderedDict variants.