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

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Date:   Mon, 13 Mar 2023 12:57:44 -0700
From:   John Stultz <jstultz@...gle.com>
To:     Zheng Wang <zyytlz.wz@....com>,
        Yongqin Liu <yongqin.liu@...aro.org>,
        Sumit Semwal <sumit.semwal@...aro.org>
Cc:     arnd@...db.de, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org, hackerzheng666@...il.com,
        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

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.

thanks
-john