linux-kernel - Re: [PATCH v3] usbip: vudc: Fix use after free bug in vudc

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Date:   Fri, 17 Mar 2023 01:47:35 +0800
From:   Zheng Hacker <hackerzheng666@...il.com>
To:     Zheng Wang <zyytlz.wz@....com>
Cc:     valentina.manea.m@...il.com, shuah@...nel.org,
        gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, 1395428693sheep@...il.com,
        alex000young@...il.com
Subject: Re: [PATCH v3] usbip: vudc: Fix use after free bug in vudc_remove due
 to race condition

Sorry this is not v3 but v1, I will resubmit v1 again. Sorry again for
my mistake.

Thanks,
Zheng

Zheng Wang <zyytlz.wz@....com> 于2023年3月17日周五 01:44写道：
>
> In vudc_probe, it calls init_vudc_hw, which bound &udc->timer with v_timer.
>
> When it calls usbip_sockfd_store, it will call v_start_timer to start the
> timer work.
>
> When we call vudc_remove to remove the driver, theremay be a sequence as
> follows:
>
> Fix it by shutdown the timer work before cleanup in vudc_remove.
>
> Note that removing a driver is a root-only operation, and should never
> happen.
>
> CPU0                  CPU1
>
>                      |v_timer
> vudc_remove          |
> kfree(udc);          |
> //free shost         |
>                      |udc->gadget
>                      |//use
>
> Fixes: b6a0ca111867 ("usbip: vudc: Add UDC specific ops")
> Signed-off-by: Zheng Wang <zyytlz.wz@....com>
> ---
>  drivers/usb/usbip/vudc_dev.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/usb/usbip/vudc_dev.c b/drivers/usb/usbip/vudc_dev.c
> index 2bc428f2e261..33d0991755bb 100644
> --- a/drivers/usb/usbip/vudc_dev.c
> +++ b/drivers/usb/usbip/vudc_dev.c
> @@ -633,6 +633,7 @@ int vudc_remove(struct platform_device *pdev)
>  {
>         struct vudc *udc = platform_get_drvdata(pdev);
>
> +       timer_shutdown_sync(&udc->timer);
>         usb_del_gadget_udc(&udc->gadget);
>         cleanup_vudc_hw(udc);
>         kfree(udc);
> --
> 2.25.1
>