https://github.com/python/cpython/commit/cae853e3b44cd5cb033b904e163c490dd28bc30a
commit: cae853e3b44cd5cb033b904e163c490dd28bc30a
branch: main
author: Kumar Aditya <[email protected]>
committer: kumaraditya303 <[email protected]>
date: 2024-10-25T18:19:30+05:30
summary:
GH-125789: fix `fut._callbacks` to always return a copy of callbacks (#125922)
Fix `asyncio.Future._callbacks` to always return a copy of the internal list of
callbacks to avoid mutation from user code affecting the internal state.
files:
A Misc/NEWS.d/next/Library/2024-10-24-14-08-10.gh-issue-125789.eaiAMw.rst
M Lib/test/test_asyncio/test_futures.py
M Modules/_asynciomodule.c
diff --git a/Lib/test/test_asyncio/test_futures.py
b/Lib/test/test_asyncio/test_futures.py
index c566b28adb2408..b3517407e5394f 100644
--- a/Lib/test/test_asyncio/test_futures.py
+++ b/Lib/test/test_asyncio/test_futures.py
@@ -697,6 +697,24 @@ def test_future_del_segfault(self):
with self.assertRaises(AttributeError):
del fut._log_traceback
+ 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 0a769c46b87ac8..a7385b4c541df9 100644
--- a/Modules/_asynciomodule.c
+++ b/Modules/_asynciomodule.c
@@ -1265,52 +1265,49 @@ 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 *
_______________________________________________
Python-checkins mailing list -- [email protected]
To unsubscribe send an email to [email protected]
https://mail.python.org/mailman3/lists/python-checkins.python.org/
Member address: [email protected]
