To prevent races with ep_remove_waitqueue() removing the
waitqueue at the same time.
Reported-by: syzbot+a2a3c4909716e2714...@syzkaller.appspotmail.com
Signed-off-by: Martijn Coenen <m...@android.com>
---
drivers/android/binder.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 15e3d3c2260d..359220f87e1d 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -4376,6 +4376,15 @@ static int binder_thread_release(struct binder_proc
*proc,
binder_inner_proc_unlock(thread->proc);
+ /*
+ * 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(proc, &thread->todo);
--
2.16.1.291.g4437f3f132-goog
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