Commit 4527025d authored Mar 17, 2026 by Jakub Kicinski

nfc: nci: fix circular locking dependency in nci_close_device



nci_close_device() flushes rx_wq and tx_wq while holding req_lock.
This causes a circular locking dependency because nci_rx_work()
running on rx_wq can end up taking req_lock too:

  nci_rx_work -> nci_rx_data_packet -> nci_data_exchange_complete
    -> __sk_destruct -> rawsock_destruct -> nfc_deactivate_target
    -> nci_deactivate_target -> nci_request -> mutex_lock(&ndev->req_lock)

Move the flush of rx_wq after req_lock has been released.
This should safe (I think) because NCI_UP has already been cleared
and the transport is closed, so the work will see it and return
-ENETDOWN.

NIPA has been hitting this running the nci selftest with a debug
kernel on roughly 4% of the runs.

Fixes: 6a2968aa ("NFC: basic NCI protocol implementation")
Reviewed-by: Ian Ray <ian.ray@gehealthcare.com>
Link: https://patch.msgid.link/20260317193334.988609-1-kuba@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>

parent 57ce3b2e

net/nfc/nci/core.c

+6 −4

Original line number	Diff line number	Diff line
		@@ -579,8 +579,7 @@ static int nci_close_device(struct nci_dev *ndev)
		skb_queue_purge(&ndev->rx_q);
		skb_queue_purge(&ndev->tx_q);

		/* Flush RX and TX wq */
		flush_workqueue(ndev->rx_wq);
		/* Flush TX wq, RX wq flush can't be under the lock */
		flush_workqueue(ndev->tx_wq);

		/* Reset device */
		@@ -592,13 +591,13 @@ static int nci_close_device(struct nci_dev *ndev)
		msecs_to_jiffies(NCI_RESET_TIMEOUT));

		/* After this point our queues are empty
		* and no works are scheduled.
		* rx work may be running but will see that NCI_UP was cleared
		*/
		ndev->ops->close(ndev);

		clear_bit(NCI_INIT, &ndev->flags);

		/* Flush cmd wq */
		/* Flush cmd and tx wq */
		flush_workqueue(ndev->cmd_wq);

		timer_delete_sync(&ndev->cmd_timer);
		@@ -613,6 +612,9 @@ static int nci_close_device(struct nci_dev *ndev)

		mutex_unlock(&ndev->req_lock);

		/* rx_work may take req_lock via nci_deactivate_target */
		flush_workqueue(ndev->rx_wq);

		return 0;
		}