From 08d665d607aded4be5461319b61023debdaacbd0 Mon Sep 17 00:00:00 2001 From: Serhiy Storchaka Date: Wed, 17 Dec 2025 19:15:21 +0200 Subject: [PATCH] [3.13] gh-112127: Fix possible use-after-free in atexit.unregister() (GH-114092) (GH-142880) (cherry picked from commit 2b466c47c333106dc9522ab77898e6972e25a2c6) Co-authored-by: Benjamin Johnson --- Lib/test/_test_atexit.py | 13 +++++++++++++ Misc/ACKS | 1 + .../2025-12-17-14-41-09.gh-issue-112127.13OHQk.rst | 2 ++ Modules/atexitmodule.c | 4 +++- 4 files changed, 19 insertions(+), 1 deletion(-) create mode 100644 Misc/NEWS.d/next/Library/2025-12-17-14-41-09.gh-issue-112127.13OHQk.rst diff --git a/Lib/test/_test_atexit.py b/Lib/test/_test_atexit.py index f618c1fcbca5..490b0686a0c1 100644 --- a/Lib/test/_test_atexit.py +++ b/Lib/test/_test_atexit.py @@ -135,6 +135,19 @@ class GeneralTest(unittest.TestCase): finally: atexit.unregister(func) + def test_eq_unregister_clear(self): + # Issue #112127: callback's __eq__ may call unregister or _clear + class Evil: + def __eq__(self, other): + action(other) + return NotImplemented + + for action in atexit.unregister, lambda o: atexit._clear(): + with self.subTest(action=action): + atexit.register(lambda: None) + atexit.unregister(Evil()) + atexit._clear() + if __name__ == "__main__": unittest.main() diff --git a/Misc/ACKS b/Misc/ACKS index 55713d3b2868..85ac1d5feefb 100644 --- a/Misc/ACKS +++ b/Misc/ACKS @@ -892,6 +892,7 @@ Jim Jewett Pedro Diaz Jimenez Orjan Johansen Fredrik Johansson +Benjamin Johnson Gregory K. Johnson Kent Johnson Michael Johnson diff --git a/Misc/NEWS.d/next/Library/2025-12-17-14-41-09.gh-issue-112127.13OHQk.rst b/Misc/NEWS.d/next/Library/2025-12-17-14-41-09.gh-issue-112127.13OHQk.rst new file mode 100644 index 000000000000..c983683ebd55 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2025-12-17-14-41-09.gh-issue-112127.13OHQk.rst @@ -0,0 +1,2 @@ +Fix possible use-after-free in :func:`atexit.unregister` when the callback +is unregistered during comparison. diff --git a/Modules/atexitmodule.c b/Modules/atexitmodule.c index c009235b7a36..93d4c4ede325 100644 --- a/Modules/atexitmodule.c +++ b/Modules/atexitmodule.c @@ -287,7 +287,9 @@ atexit_unregister(PyObject *module, PyObject *func) continue; } - int eq = PyObject_RichCompareBool(cb->func, func, Py_EQ); + PyObject *to_compare = Py_NewRef(cb->func); + int eq = PyObject_RichCompareBool(to_compare, func, Py_EQ); + Py_DECREF(to_compare); if (eq < 0) { return NULL; } -- 2.47.3