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From:   Zheng Hacker <hackerzheng666@gmail.com>
Date:   Mon, 13 Mar 2023 16:48:54 +0800
Message-ID: <CAJedcCztRHuHVtrqsA3Osn+yp+Swgbu1GEAyfDE3d90CREn25g@mail.gmail.com>
Subject: Re: [PATCH v2] usb: gadget: udc: renesas_usb3: Fix use after free bug
 in renesas_usb3_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>,
        Biju Das <biju.das.jz@bp.renesas.com>,
        "phil.edworthy@renesas.com" <phil.edworthy@renesas.com>,
        "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=
3=E6=9C=8813=E6=97=A5=E5=91=A8=E4=B8=80 16:28=E5=86=99=E9=81=93=EF=BC=9A
>
> Hi Zheng,
>
> > From: Zheng Wang, Sent: Sunday, March 12, 2023 1:13 AM
> >
> > In renesas_usb3_probe, &usb3->role_work is bound with
> > renesas_usb3_role_work. renesas_usb3_start will be called
> > to start the work.
> >
> > to make cleanup, there may be an unfinished work. The possible
> > sequence is as follows:
>
> Why do you remove the following description on this v2 patch?
> -----
> If we remove the driver which will call usbhs_remove
> -----
> I think this description is helpful to understand.
>

Sorry I misunderstood you previous response for my poor English. Will
append it again in the next version.

Best reagrds,
Zheng

>
> > Fix it by canceling the work before cleanup in the renesas_usb3_remove
> >
> > 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
> >
> > Fixes: 39facfa01c9f ("usb: gadget: udc: renesas_usb3: Add register of u=
sb role switch")
> > Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
> > ---
> > v2:
> > - fix typo, use clearer commit message and only cancel the UAF-related =
work suggested by Yoshihiro Shimoda
> > ---
> >  drivers/usb/gadget/udc/renesas_usb3.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/usb/gadget/udc/renesas_usb3.c b/drivers/usb/gadget=
/udc/renesas_usb3.c
> > index bee6bceafc4f..a301af66bd91 100644
> > --- a/drivers/usb/gadget/udc/renesas_usb3.c
> > +++ b/drivers/usb/gadget/udc/renesas_usb3.c
> > @@ -2661,6 +2661,7 @@ static int renesas_usb3_remove(struct platform_de=
vice *pdev)
> >       debugfs_remove_recursive(usb3->dentry);
> >       device_remove_file(&pdev->dev, &dev_attr_role);
> >
> > +     cancel_work_sync(&usb3->role_work);
> >       usb_role_switch_unregister(usb3->role_sw);
> >
> >       usb_del_gadget_udc(&usb3->gadget);
> > --
> > 2.25.1
>