linux-kernel - Re: [PATCH net v2] net: ethernet: fix use after free bug in ns83820_remove

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Message-ID: <20230413100128.bcnqvdpu6hgilws4@soft-dev3-1>
Date:   Thu, 13 Apr 2023 12:01:28 +0200
From:   Horatiu Vultur <horatiu.vultur@...rochip.com>
To:     Zheng Wang <zyytlz.wz@....com>
CC:     <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
        <pabeni@...hat.com>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <hackerzheng666@...il.com>,
        <1395428693sheep@...il.com>, <alex000young@...il.com>
Subject: Re: [PATCH net v2] net: ethernet: fix use after free bug in
 ns83820_remove_one due to race condition

The 04/13/2023 15:14, Zheng Wang wrote:

Hi Zheng,

> 
> 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

Will you not have the same issue if you remove the driver after you
schedule rx_tasklet? Because rx_action will use also ndev.

> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Zheng Wang <zyytlz.wz@....com>
> ---
> 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
> 

-- 
/Horatiu