linux-kernel - Re: [PATCH v5] usb: gadget: udc: renesas_usb3: Fix use after free bug in renesas_usb3

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Date:   Fri, 17 Mar 2023 01:25:50 +0800
From:   Zheng Hacker <hackerzheng666@...il.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Zheng Wang <zyytlz.wz@....com>, p.zabel@...gutronix.de,
        biju.das.jz@...renesas.com, phil.edworthy@...esas.com,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        1395428693sheep@...il.com, alex000young@...il.com,
        yoshihiro.shimoda.uh@...esas.com
Subject: Re: [PATCH v5] usb: gadget: udc: renesas_usb3: Fix use after free bug
 in renesas_usb3_remove due to race condition

Greg KH <gregkh@...uxfoundation.org> 于2023年3月17日周五 00:23写道：
>
> On Thu, Mar 16, 2023 at 11:56:45PM +0800, Zheng Wang wrote:
> > In renesas_usb3_probe, &usb3->role_work is bound with
> > renesas_usb3_role_work. renesas_usb3_start will be called
> > to start the work.
>
> You have a full 72 columns to write in, please use them :)
>

Thanks for your kind reminder. I'll fix the format in the next version.

> >
> > 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.
> >
> > 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
>
> Why can't this be written so it looks better:

Sorry, I'll beautify the format next time.

>
>  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
>
> Note that removing a driver is a root-only operation, and should never
> happen so please also say that.
>
Get it.

Best regards,
Zheng

> thanks,
>
> greg k-h