linux-kernel - RE: [PATCH v2] usb: gadget: udc: renesas_usb3: Fix use after free bug in renesas_usb3

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Message-ID: <TYBPR01MB534196428158C2D79A910E07D8B99@TYBPR01MB5341.jpnprd01.prod.outlook.com>
Date:   Mon, 13 Mar 2023 08:28:09 +0000
From:   Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
To:     Zheng Wang <zyytlz.wz@....com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
CC:     "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
        Biju Das <biju.das.jz@...renesas.com>,
        "phil.edworthy@...esas.com" <phil.edworthy@...esas.com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "hackerzheng666@...il.com" <hackerzheng666@...il.com>,
        "1395428693sheep@...il.com" <1395428693sheep@...il.com>,
        "alex000young@...il.com" <alex000young@...il.com>
Subject: RE: [PATCH v2] usb: gadget: udc: renesas_usb3: Fix use after free bug
 in  renesas_usb3_remove due to race condition

Hi Zheng,

> From: Zheng Wang, Sent: Sunday, March 12, 2023 1:13 AM
> 
> In renesas_usb3_probe, &usb3->role_work is bound with
> renesas_usb3_role_work. renesas_usb3_start will be called
> to start the work.
> 
> to make cleanup, there may be an unfinished work. The possible
> sequence is as follows:

Why do you remove the following description on this v2 patch?
-----
If we remove the driver which will call usbhs_remove
-----
I think this description is helpful to understand.

Best regards,
Yoshihiro Shimoda

> Fix it by canceling the work before cleanup in the renesas_usb3_remove
> 
> CPU0                  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
> 
> Fixes: 39facfa01c9f ("usb: gadget: udc: renesas_usb3: Add register of usb role switch")
> Signed-off-by: Zheng Wang <zyytlz.wz@....com>
> ---
> v2:
> - fix typo, use clearer commit message and only cancel the UAF-related work suggested by Yoshihiro Shimoda
> ---
>  drivers/usb/gadget/udc/renesas_usb3.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/usb/gadget/udc/renesas_usb3.c b/drivers/usb/gadget/udc/renesas_usb3.c
> index bee6bceafc4f..a301af66bd91 100644
> --- a/drivers/usb/gadget/udc/renesas_usb3.c
> +++ b/drivers/usb/gadget/udc/renesas_usb3.c
> @@ -2661,6 +2661,7 @@ static int renesas_usb3_remove(struct platform_device *pdev)
>  	debugfs_remove_recursive(usb3->dentry);
>  	device_remove_file(&pdev->dev, &dev_attr_role);
> 
> +	cancel_work_sync(&usb3->role_work);
>  	usb_role_switch_unregister(usb3->role_sw);
> 
>  	usb_del_gadget_udc(&usb3->gadget);
> --
> 2.25.1