Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20230317100954.2626573-1-zyytlz.wz@163.com> <d05ae776-ee19-2ce0-c06b-9825e5cbea82@linuxfoundation.org>
 <CAJedcCwK8Z_nuBM4NnM1PwbTqTnfX2n6UEy9dd5LKf_GScq=xA@mail.gmail.com>
 <CAJedcCxT0ggGbVSQnqpcYcN=5gahUOEwGWZrP4P1Lz29A8Smqg@mail.gmail.com> <8219a54a-f83d-f31e-bd10-74660d829a06@linuxfoundation.org>
In-Reply-To: <8219a54a-f83d-f31e-bd10-74660d829a06@linuxfoundation.org>
From:   Zheng Hacker <hackerzheng666@gmail.com>
Date:   Fri, 14 Apr 2023 10:33:35 +0800
Message-ID: <CAJedcCxCK-J1zfKNU9q1VCxNJS-0kbeMc5XqVy2z6hatoEQBcA@mail.gmail.com>
Subject: Re: [PATCH v3] usbip: vudc: Fix use after free bug in vudc_remove due
 to race condition
To:     Shuah Khan <skhan@linuxfoundation.org>
Cc:     Zheng Wang <zyytlz.wz@163.com>, valentina.manea.m@gmail.com,
        gregkh@linuxfoundation.org, linux-usb@vger.kernel.org,
        linux-kernel@vger.kernel.org, 1395428693sheep@gmail.com,
        alex000young@gmail.com
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

Hi Shuah,

I got it. I'll try it.

Best regards,
Zheng

Shuah Khan <skhan@linuxfoundation.org> =E4=BA=8E2023=E5=B9=B44=E6=9C=8814=
=E6=97=A5=E5=91=A8=E4=BA=94 02:01=E5=86=99=E9=81=93=EF=BC=9A
>
> On 4/13/23 02:09, Zheng Hacker wrote:
> > Friendly ping about the issue.
> > Sorry that I couldn't make test about the driver.
> >
> > Thanks,
> > Zheng
> >
> > Zheng Hacker <hackerzheng666@gmail.com> =E4=BA=8E2023=E5=B9=B43=E6=9C=
=8818=E6=97=A5=E5=91=A8=E5=85=AD 15:39=E5=86=99=E9=81=93=EF=BC=9A
> >>
> >> Shuah Khan <skhan@linuxfoundation.org> =E4=BA=8E2023=E5=B9=B43=E6=9C=
=8818=E6=97=A5=E5=91=A8=E5=85=AD 06:53=E5=86=99=E9=81=93=EF=BC=9A
> >>>
> >>> On 3/17/23 04:09, Zheng Wang wrote:
> >>>> In vudc_probe, it calls init_vudc_hw, which bound &udc->timer with v=
_timer.
> >>>>
> >>>> When it calls usbip_sockfd_store, it will call v_start_timer to star=
t the
> >>>> timer work.
> >>>>
> >>>> When we call vudc_remove to remove the driver, theremay be a sequenc=
e as
> >>>> follows:
> >>>>
> >>>> Fix it by shutdown the timer work before cleanup in vudc_remove.
> >>>>
> >>>> Note that removing a driver is a root-only operation, and should nev=
er
> >>>> happen. But the attacker can directly unplug the usb to trigger the =
remove
> >>>> function.
> >>>>
> >>>> CPU0                  CPU1
> >>>>
> >>>>                        |v_timer
> >>>> vudc_remove          |
> >>>> kfree(udc);          |
> >>>> //free shost         |
> >>>>                        |udc->gadget
> >>>>                        |//use
> >>>>
> >>>> The udc might be removed before v_timer finished, and UAF happens.
> >>>>
> >>>> This bug was found by Codeql static analysis and might by false posi=
tive.
> >>>
> >>> This statement that this could be a false positive makes me hesitate
> >>> taking this patch.
> >>>
> >>> What kind of testing have you done with this fix? Were you able to te=
st
> >>> the scenario of unplugging usb?
> >>>
> >>
> >> Sorry I did't make a full test for I did't have the device. The
> >> attacking scenario if based on other cases.
> >>
>
> Sorry. I really need for you test this and provide information on how
> it was tested.
>
> thanks,
> -- Shuah
>