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From:   Zheng Hacker <hackerzheng666@gmail.com>
Date:   Thu, 13 Apr 2023 23:38:38 +0800
Message-ID: <CAJedcCzGe7AwP4te_dO2_42SSkmPCxGraowtD=YED4Pd5BTaNA@mail.gmail.com>
Subject: Re: [RESEND PATCH] usb: renesas_usbhs: Fix use after free bug in
 usbhs_remove due to race condition
To:     Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Cc:     Zheng Wang <zyytlz.wz@163.com>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "p.zabel@pengutronix.de" <p.zabel@pengutronix.de>,
        "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "1395428693sheep@gmail.com" <1395428693sheep@gmail.com>,
        "alex000young@gmail.com" <alex000young@gmail.com>
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Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com> =E4=BA=8E2023=E5=B9=B4=
4=E6=9C=8813=E6=97=A5=E5=91=A8=E5=9B=9B 20:19=E5=86=99=E9=81=93=EF=BC=9A
>
> 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].

Thanks for your advice. Will apply in the next.

Best regards,
Zheng

> -----
> 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 w=
ork_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_u=
sbhs/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 *pde=
v)
> >
> >       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
>