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Date:   Tue, 18 Apr 2023 13:44:32 +0200
From:   Horatiu Vultur <horatiu.vultur@microchip.com>
To:     Zheng Wang <zyytlz.wz@163.com>
CC:     <davem@davemloft.net>, <edumazet@google.com>, <kuba@kernel.org>,
        <pabeni@redhat.com>, <netdev@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <hackerzheng666@gmail.com>,
        <1395428693sheep@gmail.com>, <alex000young@gmail.com>
Subject: Re: [PATCH net v3] net: ethernet: fix use after free bug in
 ns83820_remove_one  due to race condition
Message-ID: <20230418114432.4zd5vec4q7t4w7ll@soft-dev3-1>
References: <20230417013107.360888-1-zyytlz.wz@163.com>
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In-Reply-To: <20230417013107.360888-1-zyytlz.wz@163.com>
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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