[PATCH 5.4 31/43] Bluetooth: hci_core: cancel all works upon hci_unregister_dev()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

5.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>

[ Upstream commit 0d151a103775dd9645c78c97f77d6e2a5298d913 ]

syzbot is reporting that calling hci_release_dev() from hci_error_reset()
due to hci_dev_put() from hci_error_reset() can cause deadlock at
destroy_workqueue(), for hci_error_reset() is called from
hdev->req_workqueue which destroy_workqueue() needs to flush.

We need to make sure that hdev->{rx_work,cmd_work,tx_work} which are
queued into hdev->workqueue and hdev->{power_on,error_reset} which are
queued into hdev->req_workqueue are no longer running by the moment

       destroy_workqueue(hdev->workqueue);
       destroy_workqueue(hdev->req_workqueue);

are called from hci_release_dev().

Call cancel_work_sync() on these work items from hci_unregister_dev()
as soon as hdev->list is removed from hci_dev_list.

Reported-by: syzbot <syzbot+da0a9c9721e36db712e8@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=da0a9c9721e36db712e8
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/bluetooth/hci_core.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index c60204b639ab7..71a7e42097cc0 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -3412,7 +3412,11 @@ void hci_unregister_dev(struct hci_dev *hdev)
 	list_del(&hdev->list);
 	write_unlock(&hci_dev_list_lock);
 
+	cancel_work_sync(&hdev->rx_work);
+	cancel_work_sync(&hdev->cmd_work);
+	cancel_work_sync(&hdev->tx_work);
 	cancel_work_sync(&hdev->power_on);
+	cancel_work_sync(&hdev->error_reset);
 
 	hci_dev_do_close(hdev);
 
-- 
2.43.0