From: Martijn Coenen <maco@android.com>
To: gregkh@linuxfoundation.org, john.stultz@linaro.org,
tkjos@google.com, arve@android.com
Cc: devel@driverdev.osuosl.org, ebiggers@google.com,
linux-kernel@vger.kernel.org, maco@google.com,
Martijn Coenen <maco@android.com>,
dvyukov@google.com
Subject: [PATCH] ANDROID: binder: synchronize_rcu() when using POLLFREE.
Date: Fri, 16 Feb 2018 09:47:15 +0100 [thread overview]
Message-ID: <20180216084715.14969-1-maco@android.com> (raw)
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+
---
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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next reply other threads:[~2018-02-16 8:47 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-16 8:47 Martijn Coenen [this message]
2018-02-16 8:49 ` [PATCH] ANDROID: binder: synchronize_rcu() when using POLLFREE Martijn Coenen
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