[PATCH RESEND] usbip: vudc: Fix use after free bug in vudc_remove due to race condition

[PATCH RESEND] usbip: vudc: Fix use after free bug in vudc_remove due to race condition

[Zheng Wang]

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@163.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

Re: [PATCH RESEND] usbip: vudc: Fix use after free bug in vudc_remove due to race condition

[Shuah Khan]

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@163.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

Re: [PATCH RESEND] usbip: vudc: Fix use after free bug in vudc_remove due to race condition

[Zheng Hacker]

Shuah Khan <skhan@linuxfoundation.org> 于2023年3月17日周五 01:59写道：
>
> 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.
>

Get it, I found it by static analysis. So this might be false postive.
Will add this
to next version of patch

Best regards,
Zheng

> > 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@163.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