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Commit 5eeb2ca0 authored by Martijn Coenen's avatar Martijn Coenen Committed by Greg Kroah-Hartman
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ANDROID: binder: synchronize_rcu() when using POLLFREE. 



To prevent races with ep_remove_waitqueue() removing the
waitqueue at the same time.

Reported-by: default avatar <syzbot+a2a3c4909716e271487e@syzkaller.appspotmail.com>
Signed-off-by: default avatarMartijn Coenen <maco@android.com>
Cc: stable <stable@vger.kernel.org> # 4.14+
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 8ca86f16

drivers/android/binder.c

+9 −0
Original line number Original line Diff line number Diff line
@@ -4382,6 +4382,15 @@ static int binder_thread_release(struct binder_proc *proc, 




	binder_inner_proc_unlock(thread->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)

	if (send_reply)

		binder_send_failed_reply(send_reply, BR_DEAD_REPLY);

		binder_send_failed_reply(send_reply, BR_DEAD_REPLY);

	binder_release_work(proc, &thread->todo);

	binder_release_work(proc, &thread->todo);