[PATCH net v2] net: ethernet: fix use after free bug in ns83820_remove_one due to race condition

[Zheng Wang]

In ns83820_init_one, dev->tq_refill was bound with queue_refill.

If irq happens, it will call ns83820_irq->ns83820_do_isr.
Then it invokes tasklet_schedule(&dev->rx_tasklet) to start
rx_action function. And rx_action will call ns83820_rx_kick
and finally start queue_refill function.

If we remove the driver without finishing the work, there
may be a race condition between ndev, which may cause UAF
bug.

CPU0                  CPU1

                     |queue_refill
ns83820_remove_one   |
free_netdev	 		 |
put_device			 |
free ndev			 |
                     |rx_refill
                     |//use ndev

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Zheng Wang <zyytlz.wz@xxxxxxx>
---
v2:
- cancel the work after unregister_netdev to make sure there 
is no more request suggested by Jakub Kicinski
---
 drivers/net/ethernet/natsemi/ns83820.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/ethernet/natsemi/ns83820.c b/drivers/net/ethernet/natsemi/ns83820.c
index 998586872599..2e84b9fcd8e9 100644
--- a/drivers/net/ethernet/natsemi/ns83820.c
+++ b/drivers/net/ethernet/natsemi/ns83820.c
@@ -2208,8 +2208,13 @@ static void ns83820_remove_one(struct pci_dev *pci_dev)
 
 	ns83820_disable_interrupts(dev); /* paranoia */
 
+	netif_carrier_off(ndev);
+	netif_tx_disable(ndev);
+
 	unregister_netdev(ndev);
 	free_irq(dev->pci_dev->irq, ndev);
+	cancel_work_sync(&dev->tq_refill);
+
 	iounmap(dev->base);
 	dma_free_coherent(&dev->pci_dev->dev, 4 * DESC_SIZE * NR_TX_DESC,
 			  dev->tx_descs, dev->tx_phy_descs);
-- 
2.25.1