2023-03-16 17:45:13

by Zheng Wang

Subject: [PATCH v3] usbip: vudc: Fix use after free bug in vudc_remove due to race condition

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 <[email protected]>
---
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

2023-03-16 17:47:53

by Zheng Hacker

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 <[email protected]> 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 <[email protected]>
> ---
> 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
>

2023-03-16 17:57:53

by Shuah Khan

Subject: Re: [PATCH v3] usbip: vudc: Fix use after free bug in vudc_remove due to race condition

On 3/16/23 11:44, 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:
>

When you resend the patch as you indicated would, please add details
on how you found this proble,m.

> Fix it by shutdown the timer work before cleanup in vudc_remove.
>

thanks,
-- Shuah

2023-03-16 18:02:42

by Zheng Hacker

Subject: Re: [PATCH v3] usbip: vudc: Fix use after free bug in vudc_remove due to race condition

Shuah Khan <[email protected]> 于2023年3月17日周五 01:57写道：
>
> On 3/16/23 11:44, 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:
> >
>
> When you resend the patch as you indicated would, please add details
> on how you found this proble,m.
>

Get it, I found it by static analysis. So this might be false postive.

Best regards,
Zheng

> > Fix it by shutdown the timer work before cleanup in vudc_remove.
> >
>
> thanks,
> -- Shuah
>