linux-kernel - Re: [PATCH] misc: hisi_hikey_usb: Fix use after free bug in hisi_hikey_usb

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Date:   Tue, 14 Mar 2023 09:01:46 +0800
From:   Zheng Hacker <hackerzheng666@...il.com>
To:     John Stultz <jstultz@...gle.com>
Cc:     Zheng Wang <zyytlz.wz@....com>,
        Yongqin Liu <yongqin.liu@...aro.org>,
        Sumit Semwal <sumit.semwal@...aro.org>, arnd@...db.de,
        gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        1395428693sheep@...il.com, alex000young@...il.com,
        Mauro Carvalho Chehab <mchehab@...nel.org>
Subject: Re: [PATCH] misc: hisi_hikey_usb: Fix use after free bug in
 hisi_hikey_usb_remove due to race condition

John Stultz <jstultz@...gle.com> 于2023年3月14日周二 03:57写道：
>
> On Sun, Mar 12, 2023 at 7:53 AM Zheng Wang <zyytlz.wz@....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@....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_device *pdev)
> >  static int  hisi_hikey_usb_remove(struct platform_device *pdev)
> >  {
> >         struct hisi_hikey_usb *hisi_hikey_usb = platform_get_drvdata(pdev);
> > +       cancel_work_sync(&hisi_hikey_usb->work);
> >
> >         if (hisi_hikey_usb->hub_role_sw) {
> >                 usb_role_switch_unregister(hisi_hikey_usb->hub_role_sw);
>
> 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