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From:   Zheng Hacker <hackerzheng666@gmail.com>
Date:   Fri, 17 Mar 2023 12:09:58 +0800
Message-ID: <CAJedcCzCq72UdFyuLJHP-cH-KzmhtA3EERGXSzdXnosOXqWYiA@mail.gmail.com>
Subject: Re: [PATCH v8] usb: gadget: udc: renesas_usb3: Fix use after free bug
 in renesas_usb3_remove due to race condition
To:     Greg KH <gregkh@linuxfoundation.org>
Cc:     Zheng Wang <zyytlz.wz@163.com>, skhan@linuxfoundation.org,
        p.zabel@pengutronix.de, biju.das.jz@bp.renesas.com,
        phil.edworthy@renesas.com, linux-usb@vger.kernel.org,
        linux-kernel@vger.kernel.org, 1395428693sheep@gmail.com,
        alex000young@gmail.com, yoshihiro.shimoda.uh@renesas.com
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Greg KH <gregkh@linuxfoundation.org> =E4=BA=8E2023=E5=B9=B43=E6=9C=8817=E6=
=97=A5=E5=91=A8=E4=BA=94 03:07=E5=86=99=E9=81=93=EF=BC=9A
>
> On Fri, Mar 17, 2023 at 02:16:23AM +0800, Zheng Wang wrote:
> > In renesas_usb3_probe, role_work is bound with renesas_usb3_role_work.
> > renesas_usb3_start will be called to start the work.
> >
> > If we remove the driver which will call usbhs_remove, there may be
> > an unfinished work. The possible sequence is as follows:
> >
> > Fix it by canceling the work before cleanup in the renesas_usb3_remove.
> >
> > Note that removing a driver is a root-only operation, and should never
> > happen.
> >
> > CPU0                                          CPU1
> >
> >                                        renesas_usb3_role_work
> > renesas_usb3_remove
> > usb_role_switch_unregister
> > device_unregister
> > kfree(sw)
> > free usb3->role_sw
> >                                        usb_role_switch_set_role
> >                                        //use usb3->role_sw
>
> No line at all?
>

Sorry, I'll remove the empty line. And I think there are other ways to
trigger device's remove like directly unpluging the USB device if
accessible. I think we nee to append this msg in the next version.

Best regards,
Zheng