[PATCH net 2/3] net: enc28j60: disable work before freeing the netdev

[BeaCox]

enc28j60_remove() unregisters the interface, frees the IRQ and frees the
netdev, but tx_work, setrx_work and restart_work can still be pending or
running.  tx_work is queued from enc28j60_send_packet(), setrx_work from
enc28j60_set_multicast_list(), and restart_work from
enc28j60_tx_timeout().  The handlers access the private data, the SPI
device and the netdev, all of which are freed with the netdev.

Unregister the interface first so the xmit and set_rx_mode paths can no
longer queue work, then disable the three works synchronously before
freeing the IRQ and the netdev.  disable_work_sync() drains a queued or
running instance and rejects a later queue_work(), which a plain
cancel_work_sync() would not.

Fixes: 3ec9c11da033 ("add driver for enc28j60 ethernet chip")
Cc: stable@xxxxxxxxxxxxxxx # 6.10+
Signed-off-by: BeaCox <0xbeac@xxxxxxxxx>
---
 drivers/net/ethernet/microchip/enc28j60.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/net/ethernet/microchip/enc28j60.c b/drivers/net/ethernet/microchip/enc28j60.c
index d6c9491537..bb29a94a1e 100644
--- a/drivers/net/ethernet/microchip/enc28j60.c
+++ b/drivers/net/ethernet/microchip/enc28j60.c
@@ -1600,7 +1600,16 @@ static void enc28j60_remove(struct spi_device *spi)
 {
 	struct enc28j60_net *priv = spi_get_drvdata(spi);
 
+	/*
+	 * Stop the interface first so the xmit and set_rx_mode paths can no
+	 * longer queue new work.  Then drain the works that were already
+	 * queued; the IRQ handler does not queue work, so the IRQ can be
+	 * released after the drain and before free_netdev().
+	 */
 	unregister_netdev(priv->netdev);
+	disable_work_sync(&priv->tx_work);
+	disable_work_sync(&priv->setrx_work);
+	disable_work_sync(&priv->restart_work);
 	free_irq(spi->irq, priv);
 	free_netdev(priv->netdev);
 }
-- 
2.43.0