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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.

Change-Id: Ib0cb4fc4549a813bc7f788961e37c1b89d318d83
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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Martijn Coenen 2018-02-16 09:47:15 +01:00 committed by L R
parent ccbf8c8202
commit 676c759154
1 changed files with 9 additions and 0 deletions
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9
drivers/android/binder.c
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@ -3252,6 +3252,15 @@ static int binder_free_thread(struct binder_proc *proc,
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);