From:   Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
To:     Zheng Wang <zyytlz.wz@163.com>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
CC:     "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>,
        "hackerzheng666@gmail.com" <hackerzheng666@gmail.com>,
        "1395428693sheep@gmail.com" <1395428693sheep@gmail.com>,
        "alex000young@gmail.com" <alex000young@gmail.com>
Subject: RE: [PATCH]  usb: gadget: udc: renesas_usb3: Fix use after free bug
 in renesas_usb3_remove due to race condition
Thread-Topic: [PATCH]  usb: gadget: udc: renesas_usb3: Fix use after free bug
 in renesas_usb3_remove due to race condition
Thread-Index: AQHZUr39MlZtZyaKY0ew3UxiZBCn+67zcgAw
Date:   Fri, 10 Mar 2023 04:56:31 +0000
Message-ID: <TYBPR01MB53412E8BDBB67C38E0B5E80CD8BA9@TYBPR01MB5341.jpnprd01.prod.outlook.com>
References: <20230309193020.374950-1-zyytlz.wz@163.com>
In-Reply-To: <20230309193020.374950-1-zyytlz.wz@163.com>
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Hi Zheng,

> From: Zheng Wang, Sent: Friday, March 10, 2023 4:30 AM
>=20
> In renesas_usb3_probe, &usb3->role_work is bound with
> renesas_usb3_role_work. renesas_usb3_start will be called
> to start the work.
>=20
> If we remove the module which will call renesas_usb3_remove
>   to make cleanup, there may be a unfinished work. The possible
>   sequence is as follows:

Thank you for the patch!
I think we should remove double spaces like below. (Also "an" unfinished):

-----
If we remove the module which will call renesas_usb3_remove
to make cleanup, there may be an unfinished work. The possible
sequence is as follows:
-----

> Fix it by canceling the work before cleanup in the renesas_usb3_remove
>=20
> CPU0                  CPUc1

s/CPUc1/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

Adding a blank line here is better, I think.

> Fixes: 39facfa01c9f ("usb: gadget: udc: renesas_usb3: Add register of usb=
 role switch")
> Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
> ---
>  drivers/usb/gadget/udc/renesas_usb3.c | 2 ++
>  1 file changed, 2 insertions(+)
>=20
> diff --git a/drivers/usb/gadget/udc/renesas_usb3.c b/drivers/usb/gadget/u=
dc/renesas_usb3.c
> index bee6bceafc4f..23b5f1706d25 100644
> --- a/drivers/usb/gadget/udc/renesas_usb3.c
> +++ b/drivers/usb/gadget/udc/renesas_usb3.c
> @@ -2658,6 +2658,8 @@ static int renesas_usb3_remove(struct platform_devi=
ce *pdev)
>  {
>  	struct renesas_usb3 *usb3 =3D platform_get_drvdata(pdev);
>=20
> +	cancel_work_sync(&usb3->extcon_work);

IIUC, this work is not related to the issue.
But, what do you think?
If so, adding this should be a separate patch with the following Fixes tag:

Fixes: 3b68e7ca3888 ("usb: gadget: udc: renesas_usb3: add extcon support")

Best regards,
Yoshihiro Shimoda

> +	cancel_work_sync(&usb3->role_work);
>  	debugfs_remove_recursive(usb3->dentry);
>  	device_remove_file(&pdev->dev, &dev_attr_role);
>=20
> --
> 2.25.1