linux-kernel - Re: [PATCH v6] usb: gadget: udc: renesas_usb3: Fix use after free bug in renesas_usb3

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Message-ID: <ZBNbRrKaNomV4nyJ@kroah.com>
Date:   Thu, 16 Mar 2023 19:09:10 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Zheng Wang <zyytlz.wz@....com>
Cc:     p.zabel@...gutronix.de, biju.das.jz@...renesas.com,
        phil.edworthy@...esas.com, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, hackerzheng666@...il.com,
        1395428693sheep@...il.com, alex000young@...il.com,
        yoshihiro.shimoda.uh@...esas.com
Subject: Re: [PATCH v6] usb: gadget: udc: renesas_usb3: Fix use after free
 bug in  renesas_usb3_remove due to race condition

On Fri, Mar 17, 2023 at 01:54:57AM +0800, Zheng Wang wrote:
> In renesas_usb3_probe, role_work is bound with renesas_usb3_role_work.
> renesas_usb3_start will be called to start the work.
> 
> If we remove the driver which will call usbhs_remove, 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.
> 
> Note that removing a driver is a root-only operation, and should never
> happen.
> 
> 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

Please use spaces for this, as something went wrong and it does not line
up :(