RE: [RESEND PATCH] usb: renesas_usbhs: Fix use after free bug in usbhs_remove due to race condition

[Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>]

Hi,

> From: Zheng Wang, Sent: Thursday, April 13, 2023 4:49 PM
> 
> In usbhs_probe, &priv->notify_hotplug_work is bound with
> usbhsc_notify_hotplug. It will be started then.
> 
> If we remove the driver which will call usbhs_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 usbhs_remove
> 
> CPU0                  CPU1
> 
>                     |usbhsc_notify_hotplug
> usbhs_remove         |
> usbhs_mod_remove     |
> usbhs_mod_gadget_remove|
> kfree(gpriv);       |
>                     |usbhsc_hotplug
>                     |usbhs_mod_call start
>                     |usbhsg_start
>                     |usbhsg_try_start
>                     |//use gpriv

Thank you for the patch!

You should adjust the figure like followings because Greg mentioned it on other patch [1].
-----
CPU0                      CPU1

                        | usbhsc_notify_hotplug
usbhs_remove            |
usbhs_mod_remove        |
usbhs_mod_gadget_remove |
kfree(gpriv);           |
                        | usbhsc_hotplug
                        | usbhs_mod_call start
                        | usbhsg_start
                        | usbhsg_try_start
                        | //use gpriv
-----

[1]
https://lore.kernel.org/lkml/ZBNCam0XjWehrF3c@kroah.com/

Best regards,
Yoshihiro Shimoda

> Fixes: bc57381e6347 ("usb: renesas_usbhs: use delayed_work instead of work_struct")
> Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
> ---
>  drivers/usb/renesas_usbhs/common.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/usb/renesas_usbhs/common.c b/drivers/usb/renesas_usbhs/common.c
> index 96f3939a65e2..17a0987ef4f5 100644
> --- a/drivers/usb/renesas_usbhs/common.c
> +++ b/drivers/usb/renesas_usbhs/common.c
> @@ -768,6 +768,7 @@ static int usbhs_remove(struct platform_device *pdev)
> 
>  	dev_dbg(&pdev->dev, "usb remove\n");
> 
> +	cancel_delayed_work_sync(&priv->notify_hotplug_work);
>  	/* power off */
>  	if (!usbhs_get_dparam(priv, runtime_pwctrl))
>  		usbhsc_power_ctrl(priv, 0);
> --
> 2.25.1