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gh-115874: Don't use module state in teedataobject tp_dealloc #116204

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Merged
merged 3 commits into from
Mar 18, 2024
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gh-115874: Don't use module state in teedataobject tp_dealloc #116204

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gh-115874: Don't use module state in teedataobject tp_dealloc
brandtbucher Mar 1, 2024
c10f509
No need for the tdo type; also add test
erlend-aasland Mar 2, 2024
5f098f2
Pull in main
erlend-aasland Mar 2, 2024
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10 changes: 9 additions & 1 deletion Lib/test/test_itertools.py
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
import doctest
import unittest
from test import support
from test.support import threading_helper
from test.support import threading_helper, script_helper
from itertools import *
import weakref
from decimal import Decimal
Expand Down Expand Up @@ -1699,6 +1699,14 @@ def test_tee(self):
self.pickletest(proto, a, compare=ans)
self.pickletest(proto, b, compare=ans)

def test_tee_dealloc_segfault(self):
# gh-115874: segfaults when accessing module state in tp_dealloc.
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@erlend-aasland erlend-aasland Mar 12, 2024 •
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@brandtbucher, how about this:

Suggested change
# gh-115874: segfaults when accessing module state in tp_dealloc.
# gh-115874: Segfault when accessing module state in tp_dealloc.
# The repro depends on multiple ref cycles; by importing
# typing, we implicitly create ref cycles between typing
# and copyreg. Without these cycles, the reproducer does
# not work.

script = (
"import typing, copyreg, itertools; "
"copyreg.buggy_tee = itertools.tee(())"
)
script_helper.assert_python_ok("-c", script)

# Issue 13454: Crash when deleting backward iterator from tee()
def test_tee_del_backward(self):
forward, backward = tee(repeat(None, 20000000))
Expand Down
8 changes: 3 additions & 5 deletions Modules/itertoolsmodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -815,10 +815,9 @@ teedataobject_traverse(teedataobject *tdo, visitproc visit, void * arg)
}

static void
teedataobject_safe_decref(PyObject *obj, PyTypeObject *tdo_type)
teedataobject_safe_decref(PyObject *obj)
{
while (obj && Py_IS_TYPE(obj, tdo_type) &&
Py_REFCNT(obj) == 1) {
while (obj && Py_REFCNT(obj) == 1) {
PyObject *nextlink = ((teedataobject *)obj)->nextlink;
((teedataobject *)obj)->nextlink = NULL;
Py_SETREF(obj, nextlink);
Expand All @@ -837,8 +836,7 @@ teedataobject_clear(teedataobject *tdo)
Py_CLEAR(tdo->values[i]);
tmp = tdo->nextlink;
tdo->nextlink = NULL;
itertools_state *state = get_module_state_by_cls(Py_TYPE(tdo));
teedataobject_safe_decref(tmp, state->teedataobject_type);
teedataobject_safe_decref(tmp);
return 0;
}

Expand Down