Commit d2891c4d authored Mar 28, 2017 by Michael Scott Committed by Marcel Holtmann Apr 12, 2017

Bluetooth: 6lowpan: fix delay work init in add_peer_chan()



When adding 6lowpan devices very rapidly we sometimes see a crash:
[23122.306615] CPU: 2 PID: 0 Comm: swapper/2 Not tainted 4.9.0-43-arm64 #1 Debian 4.9.9.linaro.43-1
[23122.315400] Hardware name: HiKey Development Board (DT)
[23122.320623] task: ffff800075443080 task.stack: ffff800075484000
[23122.326551] PC is at expire_timers+0x70/0x150
[23122.330907] LR is at run_timer_softirq+0xa0/0x1a0
[23122.335616] pc : [<ffff000008142dd8>] lr : [<ffff000008142f58>] pstate: 600001c5

This was due to add_peer_chan() unconditionally initializing the
lowpan_btle_dev->notify_peers delayed work structure, even if the
lowpan_btle_dev passed into add_peer_chan() had previously been
initialized.

Normally, this would go unnoticed as the delayed work timer is set for
100 msec, however when calling add_peer_chan() faster than 100 msec it
clears out a previously queued delay work causing the crash above.

To fix this, let add_peer_chan() know when a new lowpan_btle_dev is passed
in so that it only performs the delay work initialization when needed.

Signed-off-by: Michael Scott <michael.scott@linaro.org>
Acked-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

parent dcb9cfaa

net/bluetooth/6lowpan.c

+7 −3

Original line number	Diff line number	Diff line
		@@ -676,7 +676,8 @@ static struct l2cap_chan *chan_create(void)
		}

		static struct l2cap_chan add_peer_chan(struct l2cap_chan chan,
		struct lowpan_btle_dev *dev)
		struct lowpan_btle_dev *dev,
		bool new_netdev)
		{
		struct lowpan_peer *peer;

		@@ -697,6 +698,7 @@ static struct l2cap_chan add_peer_chan(struct l2cap_chan chan,
		spin_unlock(&devices_lock);

		/* Notifying peers about us needs to be done without locks held */
		if (new_netdev)
		INIT_DELAYED_WORK(&dev->notify_peers, do_notify_peers);
		schedule_delayed_work(&dev->notify_peers, msecs_to_jiffies(100));

		@@ -755,6 +757,7 @@ out:
		static inline void chan_ready_cb(struct l2cap_chan *chan)
		{
		struct lowpan_btle_dev *dev;
		bool new_netdev = false;

		dev = lookup_dev(chan->conn);

		@@ -765,12 +768,13 @@ static inline void chan_ready_cb(struct l2cap_chan *chan)
		l2cap_chan_del(chan, -ENOENT);
		return;
		}
		new_netdev = true;
		}

		if (!try_module_get(THIS_MODULE))
		return;

		add_peer_chan(chan, dev);
		add_peer_chan(chan, dev, new_netdev);
		ifup(dev->netdev);
		}

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