2023-03-10 07:01:03

by Zheng Wang

Subject: [PATCH] USB: gadget: udc: Fix use after free bug in udc_plat_remove due to race condition

In udc_plat_probe, &udc->drd_work is bound with
udc_drd_work. udc_drd_work may be called by
usbd_connect_notify to start the work.

Besides, there is a invoking chain:
udc_plat_probe
->udc_probe
->usb_add_gadget_udc_release
->usb_add_gadget

It will add a new gadget to the udc class driver
list. In usb_add_gadget, it uses usb_udc_release
as its release function, which will kfree(udc)
to when destroying the gadget.

If we remove the module which will call udc_plat_remove
to make cleanup, there may be a unfinished work.
The possible sequence is as follows:

Fix it by finishing the work before cleanup in the udc_plat_remove

Fixes: 1b9f35adb0ff ("usb: gadget: udc: Add Synopsys UDC Platform driver")
Signed-off-by: Zheng Wang <[email protected]>
---
drivers/usb/gadget/udc/snps_udc_plat.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/drivers/usb/gadget/udc/snps_udc_plat.c b/drivers/usb/gadget/udc/snps_udc_plat.c
index 8bbb89c80348..6228e178cc0a 100644
--- a/drivers/usb/gadget/udc/snps_udc_plat.c
+++ b/drivers/usb/gadget/udc/snps_udc_plat.c
@@ -230,6 +230,7 @@ static int udc_plat_remove(struct platform_device *pdev)
struct udc *dev;

dev = platform_get_drvdata(pdev);
+ cancel_delayed_work_sync(&dev->drd_work);

usb_del_gadget_udc(&dev->gadget);
/* gadget driver must not be registered */
--
2.25.1

2023-03-23 16:33:09

by Greg KH

Subject: Re: [PATCH] USB: gadget: udc: Fix use after free bug in udc_plat_remove due to race condition

On Fri, Mar 10, 2023 at 03:00:39PM +0800, Zheng Wang wrote:
> In udc_plat_probe, &udc->drd_work is bound with
> udc_drd_work. udc_drd_work may be called by
> usbd_connect_notify to start the work.
>
> Besides, there is a invoking chain:
> udc_plat_probe
> ->udc_probe
> ->usb_add_gadget_udc_release
> ->usb_add_gadget
>
> It will add a new gadget to the udc class driver
> list. In usb_add_gadget, it uses usb_udc_release
> as its release function, which will kfree(udc)
> to when destroying the gadget.
>
> If we remove the module which will call udc_plat_remove
> to make cleanup, there may be a unfinished work.
> The possible sequence is as follows:
>
> Fix it by finishing the work before cleanup in the udc_plat_remove
>
> Fixes: 1b9f35adb0ff ("usb: gadget: udc: Add Synopsys UDC Platform driver")
> Signed-off-by: Zheng Wang <[email protected]>
> ---
> drivers/usb/gadget/udc/snps_udc_plat.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/usb/gadget/udc/snps_udc_plat.c b/drivers/usb/gadget/udc/snps_udc_plat.c
> index 8bbb89c80348..6228e178cc0a 100644
> --- a/drivers/usb/gadget/udc/snps_udc_plat.c
> +++ b/drivers/usb/gadget/udc/snps_udc_plat.c
> @@ -230,6 +230,7 @@ static int udc_plat_remove(struct platform_device *pdev)
> struct udc *dev;
>
> dev = platform_get_drvdata(pdev);
> + cancel_delayed_work_sync(&dev->drd_work);
>
> usb_del_gadget_udc(&dev->gadget);
> /* gadget driver must not be registered */
> --
> 2.25.1
>

Please test this to verify that it actually works.

thanks,

greg k-h

2023-03-24 15:39:11

by Zheng Hacker

Subject: Re: [PATCH] USB: gadget: udc: Fix use after free bug in udc_plat_remove due to race condition

Greg KH <[email protected]> 于2023年3月24日周五 00:20写道：
>
> On Fri, Mar 10, 2023 at 03:00:39PM +0800, Zheng Wang wrote:
> > In udc_plat_probe, &udc->drd_work is bound with
> > udc_drd_work. udc_drd_work may be called by
> > usbd_connect_notify to start the work.
> >
> > Besides, there is a invoking chain:
> > udc_plat_probe
> > ->udc_probe
> > ->usb_add_gadget_udc_release
> > ->usb_add_gadget
> >
> > It will add a new gadget to the udc class driver
> > list. In usb_add_gadget, it uses usb_udc_release
> > as its release function, which will kfree(udc)
> > to when destroying the gadget.
> >
> > If we remove the module which will call udc_plat_remove
> > to make cleanup, there may be a unfinished work.
> > The possible sequence is as follows:
> >
> > Fix it by finishing the work before cleanup in the udc_plat_remove
> >
> > Fixes: 1b9f35adb0ff ("usb: gadget: udc: Add Synopsys UDC Platform driver")
> > Signed-off-by: Zheng Wang <[email protected]>
> > ---
> > drivers/usb/gadget/udc/snps_udc_plat.c | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/usb/gadget/udc/snps_udc_plat.c b/drivers/usb/gadget/udc/snps_udc_plat.c
> > index 8bbb89c80348..6228e178cc0a 100644
> > --- a/drivers/usb/gadget/udc/snps_udc_plat.c
> > +++ b/drivers/usb/gadget/udc/snps_udc_plat.c
> > @@ -230,6 +230,7 @@ static int udc_plat_remove(struct platform_device *pdev)
> > struct udc *dev;
> >
> > dev = platform_get_drvdata(pdev);
> > + cancel_delayed_work_sync(&dev->drd_work);
> >
> > usb_del_gadget_udc(&dev->gadget);
> > /* gadget driver must not be registered */
> > --
> > 2.25.1
> >
>
> Please test this to verify that it actually works.
>

Hi,

Sorry for my late reply. I will try to simulate a device in qemu to test.

Best regards,
Zheng

> thanks,
>
> greg k-h