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: <20230312145305.1908607-1-zyytlz.wz@163.com> <CANDhNCr=hdhKS4c+U=+W1ONHDWv6BrwL5TovGjs0G2G+Reqc9g@mail.gmail.com>
 <CAJedcCyJnV+KnFF5h+2-0W1R4uaUxUxXFUH3Q9HGYh-5F5LmBQ@mail.gmail.com>
 <CAJedcCyERP0-9DNgeKmS3C9Soqq590PteEorr_bxKzNanht=TQ@mail.gmail.com>
 <CAMSo37Vfr0DOqN+1XjH0o3pOY=BaHnSFkUbnZPOdMQ3TbfoAKg@mail.gmail.com>
 <CAJedcCzm3MqYe3QGT7V4sMmDsVHbjVSnEc2NXWPMGVZL=a_cBA@mail.gmail.com>
 <2023041308-nerd-dry-98a6@gregkh> <CAJedcCyeM2a79i0=ffKwdKfnQayo7svhTTEth2ka6K9np0Ztiw@mail.gmail.com>
 <2023041308-unvisited-slinky-a56f@gregkh> <CAJedcCxzGbUSj0nh4xYp8P2zhYSM31CGi2fGE+9VJt7mkg6h4g@mail.gmail.com>
 <CAMSo37V3vgjzgM_3Toy2HGwVuFcTw9DfVKDnVNaD-j4UJtOPvg@mail.gmail.com> <CAJedcCwow9sTEzZpiqmmcEDZ0XFLauA_tVBTJf5MfpadC1M+cQ@mail.gmail.com>
In-Reply-To: <CAJedcCwow9sTEzZpiqmmcEDZ0XFLauA_tVBTJf5MfpadC1M+cQ@mail.gmail.com>
From:   Yongqin Liu <yongqin.liu@linaro.org>
Date:   Thu, 20 Apr 2023 14:30:57 +0800
Message-ID: <CAMSo37VxLfqg7UGY8CYAYz8nqoJ12T2mERbKNn67e_+yOD3cXQ@mail.gmail.com>
Subject: Re: [PATCH] misc: hisi_hikey_usb: Fix use after free bug in
 hisi_hikey_usb_remove due to race condition
To:     Zheng Hacker <hackerzheng666@gmail.com>
Cc:     Greg KH <gregkh@linuxfoundation.org>,
        John Stultz <jstultz@google.com>,
        Zheng Wang <zyytlz.wz@163.com>,
        Sumit Semwal <sumit.semwal@linaro.org>, arnd@arndb.de,
        linux-kernel@vger.kernel.org, 1395428693sheep@gmail.com,
        alex000young@gmail.com, Mauro Carvalho Chehab <mchehab@kernel.org>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

Hi, Zheng

BTW, I just see cancel_delayed_work_sync is used in
the drivers/usb/common/usb-conn-gpio.c usb_conn_remove function.
    https://android.googlesource.com/kernel/common/+/refs/heads/android-mai=
nline/drivers/usb/common/usb-conn-gpio.c#274

I know nothing about the cancel_delayed_work_sync and cancel_work_sync
functions,
just for your information in case cancel_delayed_work_sync might be
better to be used here.

Thanks,
Yongqin Liu
On Tue, 18 Apr 2023 at 21:18, Zheng Hacker <hackerzheng666@gmail.com> wrote=
:
>
> Yongqin Liu <yongqin.liu@linaro.org> =E4=BA=8E2023=E5=B9=B44=E6=9C=8818=
=E6=97=A5=E5=91=A8=E4=BA=8C 01:31=E5=86=99=E9=81=93=EF=BC=9A
> >
> > Hi, Zheng
> >
> > Sorry for the late reply.
> >
> > I tested this change with Android build based on the ACK
> > android-mainline branch.
> > The hisi_hikey_usb module could not be removed with error like this:
> >     console:/ # rmmod -f hisi_hikey_usb
> >     rmmod: failed to unload hisi_hikey_usb: Try again
> >     1|console:/ #
> > Sorry I am not able to reproduce any problem without this commit,
> > but I do not see any problem with this change applied either.
> >
> > If there is any specific things you want to check, please feel free let=
 me know
> >
>
> Hi Yongqin,
>
> Thanks for your testing. I have no more questions about the issue.
>
> Best regards,
> Zheng
>
> > Thanks,
> > Yongqin Liu
> >
> >
> > On Fri, 14 Apr 2023 at 00:46, Zheng Hacker <hackerzheng666@gmail.com> w=
rote:
> > >
> > > Greg KH <gregkh@linuxfoundation.org> =E4=BA=8E2023=E5=B9=B44=E6=9C=88=
13=E6=97=A5=E5=91=A8=E5=9B=9B 23:56=E5=86=99=E9=81=93=EF=BC=9A
> > > >
> > > > On Thu, Apr 13, 2023 at 11:35:17PM +0800, Zheng Hacker wrote:
> > > > > Greg KH <gregkh@linuxfoundation.org> =E4=BA=8E2023=E5=B9=B44=E6=
=9C=8813=E6=97=A5=E5=91=A8=E5=9B=9B 20:48=E5=86=99=E9=81=93=EF=BC=9A
> > > > > >
> > > > > > On Thu, Apr 13, 2023 at 07:12:07PM +0800, Zheng Hacker wrote:
> > > > > > > Yongqin Liu <yongqin.liu@linaro.org> =E4=BA=8E2023=E5=B9=B44=
=E6=9C=8813=E6=97=A5=E5=91=A8=E5=9B=9B 18:55=E5=86=99=E9=81=93=EF=BC=9A
> > > > > > > >
> > > > > > > > Hi, Zheng
> > > > > > > >
> > > > > > > > On Thu, 13 Apr 2023 at 16:08, Zheng Hacker <hackerzheng666@=
gmail.com> wrote:
> > > > > > > > >
> > > > > > > > > Friendly ping about the bug.
> > > > > > > >
> > > > > > > > Sorry, wasn't aware of this message before,
> > > > > > > >
> > > > > > > > Could you please help share the instructions to reproduce t=
he problem
> > > > > > > > this change fixes?
> > > > > > > >
> > > > > > >
> > > > > > > Hi Yongqin,
> > > > > > >
> > > > > > > Thanks for your reply. This bug is found by static analysis. =
There is no PoC.
> > > > > > >
> > > > > > > >From my personal experience, triggering race condition bugs =
stably in
> > > > > > > the kernel needs some tricks.
> > > > > > > For example, you can insert some sleep-time code to slow down=
 the
> > > > > > > thread until the related object is freed.
> > > > > > > Besides, you can use gdb to control the time window. Also, th=
ere are
> > > > > > > some other tricks as [1] said.
> > > > > > >
> > > > > > > As for the reproduction, this attack vector requires that the=
 attacker
> > > > > > > can physically access the device.
> > > > > > > When he/she unplugs the usb, the remove function is triggered=
, and if
> > > > > > > the set callback is invoked, there might be a race condition.
> > > > > >
> > > > > > How does the removal of the USB device trigger a platform devic=
e
> > > > > > removal?
> > > > >
> > > > > Sorry I made a mistake. The USB device usually calls disconnect
> > > > > callback when it's unpluged.
> > > >
> > > > Yes, but you are changing the platform device disconnect, not the U=
SB
> > > > device disconnect.
> > > >
> > > > > What I want to express here is When the driver-related device(her=
e
> > > > > it's USB GPIO Hub) was removed, the remove function is triggered.
> > > >
> > > > And is this a patform device on a USB device?  If so, that's a bigg=
er
> > > > problem that we need to fix as that is not allowed.
> > >
> > > No this is not a platform  device on a USB device.
> > >
> > > >
> > > > But in looking at the code, it does not seem to be that at all, thi=
s is
> > > > just a "normal" platform device.  So how can it ever be removed fro=
m the
> > > > system?  (and no, unloading the driver doesn't count, that can neve=
r
> > > > happen on a normal machine.)
> > > >
> > >
> > > Yes, I finally figured out your meaning. I know it's hard to unplug
> > > the platform device
> > > directly. All I want to express is that it's a theoretical method
> > > except  rmmod. I think it's better to fix the bug. But if the
> > > developers think it's practically impossible, I think there's no need
> > > to take further action.
> > >
> > > Sorry for wasting your time and thanks for your explanation.
> > >
> > > Best regards,
> > > Zheng
> > >
> > > > thanks,
> > > >
> > > > greg k-h
> >
> >
> >
> > --
> > Best Regards,
> > Yongqin Liu
> > ---------------------------------------------------------------
> > #mailing list
> > linaro-android@lists.linaro.org
> > http://lists.linaro.org/mailman/listinfo/linaro-android


--=20
Best Regards,
Yongqin Liu
---------------------------------------------------------------
#mailing list
linaro-android@lists.linaro.org
http://lists.linaro.org/mailman/listinfo/linaro-android