linux-kernel - Re: [PATCH v3] usb: gadget: udc: renesas_usb3: Fix use after free bug in renesas_usb3

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Message-ID: <CAJedcCxw3Uqah_d0Uh_4CeT7-ajjspjixfWLvj0xNNOwBAxE9g@mail.gmail.com>
Date:   Tue, 14 Mar 2023 00:51:58 +0800
From:   Zheng Hacker <hackerzheng666@...il.com>
To:     Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
Cc:     Zheng Wang <zyytlz.wz@....com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "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>,
        "1395428693sheep@...il.com" <1395428693sheep@...il.com>,
        "alex000young@...il.com" <alex000young@...il.com>
Subject: Re: [PATCH v3] usb: gadget: udc: renesas_usb3: Fix use after free bug
 in renesas_usb3_remove due to race condition

Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com> 于2023年3月13日周一 20:56写道：
>
> Hi Zheng,
>
> > From: Zheng Wang, Sent: Monday, March 13, 2023 6:49 PM
> >
> > In renesas_usb3_probe, &usb3->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
> >
> > 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>
>
> Thank you for the patch!
>
> Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
>
Thanks for the detailed review :)

Best regards,
Zheng
>
> > ---
> > v3:
> > - modify the commit message to make it clearer suggested by Yoshihiro Shimoda
> > 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
>