This is a note to let you know that I've just added the patch titled

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

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: bluetooth-6lowpan-fix-delay-work-init-in-add_peer_chan.patch and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Sun Mar 18 16:55:33 CET 2018

From: Michael Scott michael.scott@linaro.org Date: Tue, 28 Mar 2017 23:10:54 -0700 Subject: Bluetooth: 6lowpan: fix delay work init in add_peer_chan()

From: Michael Scott michael.scott@linaro.org

[ Upstream commit d2891c4d071d807f01cc911dc42a68f4568d65cf ]

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 Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/bluetooth/6lowpan.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)

--- a/net/bluetooth/6lowpan.c +++ b/net/bluetooth/6lowpan.c @@ -755,7 +755,8 @@ static void set_ip_addr_bits(u8 addr_typ }

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;

@@ -786,7 +787,8 @@ static struct l2cap_chan *add_peer_chan( spin_unlock(&devices_lock);

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

return peer->chan; @@ -843,6 +845,7 @@ 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);

@@ -853,12 +856,13 @@ static inline void chan_ready_cb(struct 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); }

Patches currently in stable-queue which might be from michael.scott@linaro.org are

queue-4.9/bluetooth-6lowpan-fix-delay-work-init-in-add_peer_chan.patch