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From:   Zheng Hacker <hackerzheng666@gmail.com>
Date:   Thu, 13 Apr 2023 16:07:49 +0800
Message-ID: <CAJedcCyERP0-9DNgeKmS3C9Soqq590PteEorr_bxKzNanht=TQ@mail.gmail.com>
Subject: Re: [PATCH] misc: hisi_hikey_usb: Fix use after free bug in
 hisi_hikey_usb_remove due to race condition
To:     John Stultz <jstultz@google.com>
Cc:     Zheng Wang <zyytlz.wz@163.com>,
        Yongqin Liu <yongqin.liu@linaro.org>,
        Sumit Semwal <sumit.semwal@linaro.org>, arnd@arndb.de,
        gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org,
        1395428693sheep@gmail.com, alex000young@gmail.com,
        Mauro Carvalho Chehab <mchehab@kernel.org>
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Friendly ping about the bug.

Thanks,
Zheng

Zheng Hacker <hackerzheng666@gmail.com> =E4=BA=8E2023=E5=B9=B43=E6=9C=8814=
=E6=97=A5=E5=91=A8=E4=BA=8C 09:01=E5=86=99=E9=81=93=EF=BC=9A
>
> John Stultz <jstultz@google.com> =E4=BA=8E2023=E5=B9=B43=E6=9C=8814=E6=97=
=A5=E5=91=A8=E4=BA=8C 03:57=E5=86=99=E9=81=93=EF=BC=9A
> >
> > On Sun, Mar 12, 2023 at 7:53=E2=80=AFAM Zheng Wang <zyytlz.wz@163.com> =
wrote:
> > >
> > > In hisi_hikey_usb_probe, it called hisi_hikey_usb_of_role_switch
> > > and bound &hisi_hikey_usb->work with relay_set_role_switch.
> > > When it calls hub_usb_role_switch_set, it will finally call
> > > schedule_work to start the work.
> > >
> > > When we call hisi_hikey_usb_remove to remove the driver, there
> > > may be a sequence as follows:
> > >
> > > Fix it by finishing the work before cleanup in hisi_hikey_usb_remove.
> > >
> > > CPU0                  CPU1
> > >
> > >                     |relay_set_role_switch
> > > hisi_hikey_usb_remove|
> > >   usb_role_switch_put|
> > >     usb_role_switch_release  |
> > >      kfree(sw)     |
> > >                     | usb_role_switch_set_role
> > >                     |   //use
> > >
> > > Fixes: 7a6ff4c4cbc3 ("misc: hisi_hikey_usb: Driver to support onboard=
 USB gpio hub on Hikey960")
> > > Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
> > > ---
> > >  drivers/misc/hisi_hikey_usb.c | 1 +
> > >  1 file changed, 1 insertion(+)
> > >
> > > diff --git a/drivers/misc/hisi_hikey_usb.c b/drivers/misc/hisi_hikey_=
usb.c
> > > index 2165ec35a343..26fc895c4418 100644
> > > --- a/drivers/misc/hisi_hikey_usb.c
> > > +++ b/drivers/misc/hisi_hikey_usb.c
> > > @@ -242,6 +242,7 @@ static int hisi_hikey_usb_probe(struct platform_d=
evice *pdev)
> > >  static int  hisi_hikey_usb_remove(struct platform_device *pdev)
> > >  {
> > >         struct hisi_hikey_usb *hisi_hikey_usb =3D platform_get_drvdat=
a(pdev);
> > > +       cancel_work_sync(&hisi_hikey_usb->work);
> > >
> > >         if (hisi_hikey_usb->hub_role_sw) {
> > >                 usb_role_switch_unregister(hisi_hikey_usb->hub_role_s=
w);
> >
> > Looks sane to me.
> > Pulling in Sumit and YongQin as they have hardware and can test with it=
.
> >
> Hi John,
>
> Thanks for your reply. Thank Sumit and YongQin for being willing to
> test the solution with their hardware.
>
> Best regards,
> Zheng