Commit deee93d1 authored by Tetsuo Handa's avatar Tetsuo Handa Committed by Luiz Augusto von Dentz
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Bluetooth: use hdev->workqueue when queuing hdev->{cmd,ncmd}_timer works 

syzbot is reporting attempt to schedule hdev->cmd_work work from system_wq
WQ into hdev->workqueue WQ which is under draining operation [1], for
commit c8efcc25 ("workqueue: allow chained queueing during
destruction") does not allow such operation.

The check introduced by commit 877afada ("Bluetooth: When HCI work
queue is drained, only queue chained work") was incomplete.

Use hdev->workqueue WQ when queuing hdev->{cmd,ncmd}_timer works because
hci_{cmd,ncmd}_timeout() calls queue_work(hdev->workqueue). Also, protect
the queuing operation with RCU read lock in order to avoid calling
queue_delayed_work() after cancel_delayed_work() completed.

Link: https://syzkaller.appspot.com/bug?extid=243b7d89777f90f7613b

 [1]
Reported-by: default avatarsyzbot <syzbot+243b7d89777f90f7613b@syzkaller.appspotmail.com>
Signed-off-by: default avatarTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Fixes: 877afada ("Bluetooth: When HCI work queue is drained, only queue chained work")
Signed-off-by: default avatarLuiz Augusto von Dentz <luiz.von.dentz@intel.com>
parent 2d2cb306

net/bluetooth/hci_core.c

+13 −2
Original line number Diff line number Diff line
@@ -597,6 +597,15 @@ static int hci_dev_do_reset(struct hci_dev *hdev) 


	/* Cancel these to avoid queueing non-chained pending work */

	hci_dev_set_flag(hdev, HCI_CMD_DRAIN_WORKQUEUE);

	/* Wait for

	 *

	 *    if (!hci_dev_test_flag(hdev, HCI_CMD_DRAIN_WORKQUEUE))

	 *        queue_delayed_work(&hdev->{cmd,ncmd}_timer)

	 *

	 * inside RCU section to see the flag or complete scheduling.

	 */

	synchronize_rcu();

	/* Explicitly cancel works in case scheduled after setting the flag. */

	cancel_delayed_work(&hdev->cmd_timer);

	cancel_delayed_work(&hdev->ncmd_timer);
@@ -4063,12 +4072,14 @@ static void hci_cmd_work(struct work_struct *work) 
			if (res < 0)

				__hci_cmd_sync_cancel(hdev, -res);



			rcu_read_lock();

			if (test_bit(HCI_RESET, &hdev->flags) ||

			    hci_dev_test_flag(hdev, HCI_CMD_DRAIN_WORKQUEUE))

				cancel_delayed_work(&hdev->cmd_timer);

			else

				schedule_delayed_work(&hdev->cmd_timer,

				queue_delayed_work(hdev->workqueue, &hdev->cmd_timer,

						   HCI_CMD_TIMEOUT);

			rcu_read_unlock();

		} else {

			skb_queue_head(&hdev->cmd_q, skb);

			queue_work(hdev->workqueue, &hdev->cmd_work);

net/bluetooth/hci_event.c

+4 −2
Original line number Diff line number Diff line
@@ -3767,16 +3767,18 @@ static inline void handle_cmd_cnt_and_timer(struct hci_dev *hdev, u8 ncmd) 
{

	cancel_delayed_work(&hdev->cmd_timer);



	rcu_read_lock();

	if (!test_bit(HCI_RESET, &hdev->flags)) {

		if (ncmd) {

			cancel_delayed_work(&hdev->ncmd_timer);

			atomic_set(&hdev->cmd_cnt, 1);

		} else {

			if (!hci_dev_test_flag(hdev, HCI_CMD_DRAIN_WORKQUEUE))

				schedule_delayed_work(&hdev->ncmd_timer,

				queue_delayed_work(hdev->workqueue, &hdev->ncmd_timer,

						   HCI_NCMD_TIMEOUT);

		}

	}

	rcu_read_unlock();

}



static u8 hci_cc_le_read_buffer_size_v2(struct hci_dev *hdev, void *data,