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gh-112127: Fix use-after-free in atexit.unregister() #114092

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Merged
serhiy-storchaka merged 12 commits into from
Dec 17, 2025
Merged

gh-112127: Fix use-after-free in atexit.unregister() #114092

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6c8db8a
Fix use-after-free in atexit.unregister()
benjaminJohnson2204 Jan 15, 2024
0623581
Merge branch 'main' into gh-112127
benjaminJohnson2204 Jan 15, 2024
8e6d5c6
Merge branch 'main' into gh-112127
benjaminJohnson2204 Feb 13, 2024
075c49f
Address code review comments in atexit tests
benjaminJohnson2204 Feb 13, 2024
5b022fc
Fix linter issue
benjaminJohnson2204 Feb 13, 2024
1148d80
Merge branch 'main' into gh-112127
serhiy-storchaka Jul 17, 2024
9056824
Address PR comments
benjaminJohnson2204 Jul 18, 2024
0775ca8
Remove trailing whitespace
benjaminJohnson2204 Jul 18, 2024
c01d7db
Merge branch 'main' into gh-112127
serhiy-storchaka Dec 17, 2025
143fd96
Fix tests.
serhiy-storchaka Dec 17, 2025
99e35c9
Add a NEWS entry.
serhiy-storchaka Dec 17, 2025
7ec0097
Fix use-after-free issue in atexit.unregister
serhiy-storchaka Dec 17, 2025
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Address PR comments
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@benjaminJohnson2204
benjaminJohnson2204 committed Jul 18, 2024
commit 90568246691435ac49cab85ecd0e153a7d53a19b
8 changes: 6 additions & 2 deletions Lib/test/_test_atexit.py
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Original file line number Diff line number Diff line change
Expand Up @@ -147,13 +147,17 @@ def __call__(self):
return

def __eq__(self, o):
nonlocal cnt
cnt += 1
if cnt == 1:
self.action(o)
return self.eq_ret_val(o)
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@serhiy-storchaka serhiy-storchaka Dec 17, 2025

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self.eq_ret_val is not callable.


for action in lambda o: atexit.unregister(self), \
lambda o: atexit.unregister(o), lambda o: atexit._clear():
for action in (
lambda o: atexit.unregister(self),
lambda o: atexit.unregister(o),
lambda o: atexit._clear()
):
for eq_ret_val in NotImplemented, True:
with self.subTest(action=action, eq_ret_val=eq_ret_val):
cnt = 0
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2 changes: 0 additions & 2 deletions Modules/atexitmodule.c
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Expand Up @@ -288,10 +288,8 @@ atexit_unregister(PyObject *module, PyObject *func)
* unregister one or both
*/
PyObject *cb_func = Py_NewRef(cb->func);
PyObject *cur_func = Py_NewRef(func);
int eq = PyObject_RichCompareBool(cb->func, func, Py_EQ);
Py_DECREF(cb_func);
Py_DECREF(cur_func);
if (eq < 0) {
return NULL;
}
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