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gh-126138: Fix use-after-free in _asyncio.Task by evil __getattribute__ (#126305)

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Co-authored-by: Carol Willing <carolcode@willingconsulting.com>
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Nico-Posada 2024-11-02 03:46:00 -04:00 • committed by GitHub
parent 914356f4d4
commit f032f6ba8f
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2 changed files with 23 additions and 2 deletions
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3
Misc/NEWS.d/next/Library/2024-11-01-14-31-41.gh-issue-126138.yTniOG.rst Normal file
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@ -0,0 +1,3 @@
Fix a use-after-free crash on :class:`asyncio.Task` objects
whose underlying coroutine yields an object that implements
an evil :meth:`~object.__getattribute__`. Patch by Nico Posada.

22
Modules/_asynciomodule.c
View file

@ -2967,8 +2967,17 @@ task_step_handle_result_impl(asyncio_state *state, TaskObj *task, PyObject *resu
if (task->task_must_cancel) { if (task->task_must_cancel) {
PyObject *r; PyObject *r;
int is_true; int is_true;
// Beware: An evil `__getattribute__` could
// prematurely delete task->task_cancel_msg before the
// task is cancelled, thereby causing a UAF crash.
//
// See https://github.com/python/cpython/issues/126138
PyObject *task_cancel_msg = Py_NewRef(task->task_cancel_msg);
r = PyObject_CallMethodOneArg(result, &_Py_ID(cancel), r = PyObject_CallMethodOneArg(result, &_Py_ID(cancel),
task->task_cancel_msg); task_cancel_msg);
Py_DECREF(task_cancel_msg);
if (r == NULL) { if (r == NULL) {
return NULL; return NULL;
} }
@ -3060,8 +3069,17 @@ task_step_handle_result_impl(asyncio_state *state, TaskObj *task, PyObject *resu
if (task->task_must_cancel) { if (task->task_must_cancel) {
PyObject *r; PyObject *r;
int is_true; int is_true;
// Beware: An evil `__getattribute__` could
// prematurely delete task->task_cancel_msg before the
// task is cancelled, thereby causing a UAF crash.
//
// See https://github.com/python/cpython/issues/126138
PyObject *task_cancel_msg = Py_NewRef(task->task_cancel_msg);
r = PyObject_CallMethodOneArg(result, &_Py_ID(cancel), r = PyObject_CallMethodOneArg(result, &_Py_ID(cancel),
task->task_cancel_msg); task_cancel_msg);
Py_DECREF(task_cancel_msg);
if (r == NULL) { if (r == NULL) {
return NULL; return NULL;
} }