diff --git a/Lib/test/test_asyncio/test_futures.py b/Lib/test/test_asyncio/test_futures.py index 050d33f4fab3ed..60e93a268ab00d 100644 --- a/Lib/test/test_asyncio/test_futures.py +++ b/Lib/test/test_asyncio/test_futures.py @@ -686,6 +686,24 @@ def test_future_iter_get_referents_segfault(self): evil = gc.get_referents(_asyncio) gc.collect() + def test_callbacks_copy(self): + # See https://github.com/python/cpython/issues/125789 + # In C implementation, the `_callbacks` attribute + # always returns a new list to avoid mutations of internal state + + fut = self._new_future(loop=self.loop) + f1 = lambda _: 1 + f2 = lambda _: 2 + fut.add_done_callback(f1) + fut.add_done_callback(f2) + callbacks = fut._callbacks + self.assertIsNot(callbacks, fut._callbacks) + fut.remove_done_callback(f1) + callbacks = fut._callbacks + self.assertIsNot(callbacks, fut._callbacks) + fut.remove_done_callback(f2) + self.assertIsNone(fut._callbacks) + @unittest.skipUnless(hasattr(futures, '_CFuture'), 'requires the C _asyncio module') diff --git a/Misc/NEWS.d/next/Library/2024-10-24-14-08-10.gh-issue-125789.eaiAMw.rst b/Misc/NEWS.d/next/Library/2024-10-24-14-08-10.gh-issue-125789.eaiAMw.rst new file mode 100644 index 00000000000000..964a006bb47b7b --- /dev/null +++ b/Misc/NEWS.d/next/Library/2024-10-24-14-08-10.gh-issue-125789.eaiAMw.rst @@ -0,0 +1 @@ +Fix possible crash when mutating list of callbacks returned by :attr:`!asyncio.Future._callbacks`. It now always returns a new copy in C implementation :mod:`!_asyncio`. Patch by Kumar Aditya. diff --git a/Modules/_asynciomodule.c b/Modules/_asynciomodule.c index da44bb6b714578..bd4eaf083f7fed 100644 --- a/Modules/_asynciomodule.c +++ b/Modules/_asynciomodule.c @@ -1290,52 +1290,49 @@ static PyObject * FutureObj_get_callbacks(FutureObj *fut, void *Py_UNUSED(ignored)) { asyncio_state *state = get_asyncio_state_by_def((PyObject *)fut); - Py_ssize_t i; - ENSURE_FUTURE_ALIVE(state, fut) - if (fut->fut_callback0 == NULL) { - if (fut->fut_callbacks == NULL) { - Py_RETURN_NONE; - } - - return Py_NewRef(fut->fut_callbacks); + Py_ssize_t len = 0; + if (fut->fut_callback0 != NULL) { + len++; } - - Py_ssize_t len = 1; if (fut->fut_callbacks != NULL) { len += PyList_GET_SIZE(fut->fut_callbacks); } - - PyObject *new_list = PyList_New(len); - if (new_list == NULL) { - return NULL; + if (len == 0) { + Py_RETURN_NONE; } - PyObject *tup0 = PyTuple_New(2); - if (tup0 == NULL) { - Py_DECREF(new_list); + PyObject *callbacks = PyList_New(len); + if (callbacks == NULL) { return NULL; } - Py_INCREF(fut->fut_callback0); - PyTuple_SET_ITEM(tup0, 0, fut->fut_callback0); - assert(fut->fut_context0 != NULL); - Py_INCREF(fut->fut_context0); - PyTuple_SET_ITEM(tup0, 1, (PyObject *)fut->fut_context0); - - PyList_SET_ITEM(new_list, 0, tup0); + Py_ssize_t i = 0; + if (fut->fut_callback0 != NULL) { + PyObject *tup0 = PyTuple_New(2); + if (tup0 == NULL) { + Py_DECREF(callbacks); + return NULL; + } + PyTuple_SET_ITEM(tup0, 0, Py_NewRef(fut->fut_callback0)); + assert(fut->fut_context0 != NULL); + PyTuple_SET_ITEM(tup0, 1, Py_NewRef(fut->fut_context0)); + PyList_SET_ITEM(callbacks, i, tup0); + i++; + } if (fut->fut_callbacks != NULL) { - for (i = 0; i < PyList_GET_SIZE(fut->fut_callbacks); i++) { - PyObject *cb = PyList_GET_ITEM(fut->fut_callbacks, i); + for (Py_ssize_t j = 0; j < PyList_GET_SIZE(fut->fut_callbacks); j++) { + PyObject *cb = PyList_GET_ITEM(fut->fut_callbacks, j); Py_INCREF(cb); - PyList_SET_ITEM(new_list, i + 1, cb); + PyList_SET_ITEM(callbacks, i, cb); + i++; } } - return new_list; + return callbacks; } static PyObject *