[PATCH net v3] net: ethernet: fix use after free bug in ns83820_remove_one due to race condition

[PATCH net v3] 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@163.com>
---
v3:
- add tasklet_kill to stop more task scheduling suggested by
Horatiu Vultur
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 | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/ethernet/natsemi/ns83820.c b/drivers/net/ethernet/natsemi/ns83820.c
index 998586872599..af597719795d 100644
--- a/drivers/net/ethernet/natsemi/ns83820.c
+++ b/drivers/net/ethernet/natsemi/ns83820.c
@@ -2208,8 +2208,14 @@ 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);
+	tasklet_kill(&dev->rx_tasklet);
+	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

Re: [PATCH net v3] net: ethernet: fix use after free bug in ns83820_remove_one due to race condition

[Horatiu Vultur]

The 04/17/2023 09:31, Zheng Wang wrote:
> 
> 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@163.com>

I think it looks OK:
Reviewed-by: Horatiu Vultur <horatiu.vultur@microchip.com>

> ---
> v3:
> - add tasklet_kill to stop more task scheduling suggested by
> Horatiu Vultur
> 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 | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/net/ethernet/natsemi/ns83820.c b/drivers/net/ethernet/natsemi/ns83820.c
> index 998586872599..af597719795d 100644
> --- a/drivers/net/ethernet/natsemi/ns83820.c
> +++ b/drivers/net/ethernet/natsemi/ns83820.c
> @@ -2208,8 +2208,14 @@ 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);
> +       tasklet_kill(&dev->rx_tasklet);
> +       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
> 

-- 
/Horatiu

Re: [PATCH net v3] net: ethernet: fix use after free bug in ns83820_remove_one due to race condition

[Jakub Kicinski]

On Mon, 17 Apr 2023 09:31:07 +0800 Zheng Wang wrote:
> +	netif_carrier_off(ndev);
> +	netif_tx_disable(ndev);
> +
>  	unregister_netdev(ndev

It's not immediately obvious to me why disabling carrier and tx
are supposed to help. Please elaborate in the commit message if
you're confident that this is right.

-- 
pw-bot: cr

Re: [PATCH net v3] net: ethernet: fix use after free bug in ns83820_remove_one due to race condition

[Zheng Hacker]

Jakub Kicinski <kuba@kernel.org> 于2023年4月19日周三 12:33写道：
>
> On Mon, 17 Apr 2023 09:31:07 +0800 Zheng Wang wrote:
> > +     netif_carrier_off(ndev);
> > +     netif_tx_disable(ndev);
> > +
> >       unregister_netdev(ndev
>
> It's not immediately obvious to me why disabling carrier and tx
> are supposed to help. Please elaborate in the commit message if
> you're confident that this is right.
>

Hi Jakub,

Thanks for your reply. I'll figure it out to see if it's really necessary.

Best regards,
Zheng

> --
> pw-bot: cr