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

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Message-ID: <a1ad3c9e-ee3d-7d30-fe8e-bca2eed77872@linuxfoundation.org>
Date:   Thu, 16 Mar 2023 11:59:18 -0600
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Zheng Wang <zyytlz.wz@....com>, valentina.manea.m@...il.com
Cc:     shuah@...nel.org, gregkh@...uxfoundation.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        hackerzheng666@...il.com, 1395428693sheep@...il.com,
        alex000young@...il.com, Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH RESEND] usbip: vudc: Fix use after free bug in vudc_remove
 due to race condition

On 3/16/23 11:48, Zheng Wang wrote:
> 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.
> 

Send me v2 for this patch with adding details on how you found this problem
to this commit log.
  
> 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);

thanks,
-- Shuah