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From:   John Stultz <jstultz@google.com>
Date:   Mon, 13 Mar 2023 12:57:44 -0700
Message-ID: <CANDhNCr=hdhKS4c+U=+W1ONHDWv6BrwL5TovGjs0G2G+Reqc9g@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:     Zheng Wang <zyytlz.wz@163.com>,
        Yongqin Liu <yongqin.liu@linaro.org>,
        Sumit Semwal <sumit.semwal@linaro.org>
Cc:     arnd@arndb.de, gregkh@linuxfoundation.org,
        linux-kernel@vger.kernel.org, hackerzheng666@gmail.com,
        1395428693sheep@gmail.com, alex000young@gmail.com,
        Mauro Carvalho Chehab <mchehab@kernel.org>
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On Sun, Mar 12, 2023 at 7:53=E2=80=AFAM Zheng Wang <zyytlz.wz@163.com> wrot=
e:
>
> 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_devic=
e *pdev)
>  static int  hisi_hikey_usb_remove(struct platform_device *pdev)
>  {
>         struct hisi_hikey_usb *hisi_hikey_usb =3D platform_get_drvdata(pd=
ev);
> +       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.

thanks
-john