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Message-ID: <7d6f0ed3-678e-4fd5-bd64-f980e0035b87@I-love.SAKURA.ne.jp>
Date: Mon, 10 Jun 2024 20:00:32 +0900
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Subject: [PATCH] Bluetooth: hci_core: cancel
 rx_work,cmd_work,tx_work,power_on,error_reset works upon hci_unregister_dev()
To: Marcel Holtmann <marcel@holtmann.org>,
        Johan Hedberg <johan.hedberg@gmail.com>,
        Luiz Augusto von Dentz <luiz.dentz@gmail.com>
References: <00000000000097c554060f215b50@google.com>
Content-Language: en-US
Cc: "linux-bluetooth@vger.kernel.org" <linux-bluetooth@vger.kernel.org>,
        syzbot+da0a9c9721e36db712e8@syzkaller.appspotmail.com,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
In-Reply-To: <00000000000097c554060f215b50@google.com>
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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>
---
Completely untested. Please do tests with lockdep enabled before committing.
Maybe it is too early to cancel hdev->{rx_work,cmd_work,tx_work}.
Maybe there are more work items which should be canceled before
hci_unregister_dev() completes. I don't know...

 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 dd3b0f501018..dbbe5e2da210 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -2751,7 +2751,11 @@ 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_cmd_sync_clear(hdev);
 
-- 
2.18.4