From: Martijn Coenen maco@android.com
commit 5eeb2ca02a2f6084fc57ae5c244a38baab07033a upstream.
To prevent races with ep_remove_waitqueue() removing the waitqueue at the same time.
Reported-by: syzbot+a2a3c4909716e271487e@syzkaller.appspotmail.com Signed-off-by: Martijn Coenen maco@android.com Cc: stable stable@vger.kernel.org # 4.14+ Signed-off-by: Mattias Nissler mnissler@chromium.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/android/binder.c | 9 +++++++++ 1 file changed, 9 insertions(+)
--- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -2623,6 +2623,15 @@ static int binder_free_thread(struct bin wake_up_poll(&thread->wait, POLLHUP | POLLFREE); }
+ /* + * This is needed to avoid races between wake_up_poll() above and + * and ep_remove_waitqueue() called for other reasons (eg the epoll file + * descriptor being closed); ep_remove_waitqueue() holds an RCU read + * lock, so we can be sure it's done after calling synchronize_rcu(). + */ + if (thread->looper & BINDER_LOOPER_STATE_POLL) + synchronize_rcu(); + if (send_reply) binder_send_failed_reply(send_reply, BR_DEAD_REPLY); binder_release_work(&thread->todo);