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In-Reply-To: <7f9796d2-1885-a6f2-b9e3-d6ea58524033@xs4all.nl>
From:   Zheng Hacker <hackerzheng666@gmail.com>
Date:   Mon, 13 Mar 2023 21:45:45 +0800
Message-ID: <CAJedcCwnvNK8Gbcxz2V5+ebRJFrEYjpoJsKTKZ7DOSETr_7LEQ@mail.gmail.com>
Subject: Re: [PATCH] media: hantro: fix use after free bug in hantro_release
 due to race condition
To:     Hans Verkuil <hverkuil@xs4all.nl>
Cc:     Zheng Wang <zyytlz.wz@163.com>, ezequiel@vanguardiasur.com.ar,
        p.zabel@pengutronix.de, mchehab@kernel.org,
        linux-media@vger.kernel.org, linux-rockchip@lists.infradead.org,
        linux-kernel@vger.kernel.org, 1395428693sheep@gmail.com,
        alex000young@gmail.com
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Hans Verkuil <hverkuil@xs4all.nl> =E4=BA=8E2023=E5=B9=B43=E6=9C=8813=E6=97=
=A5=E5=91=A8=E4=B8=80 21:17=E5=86=99=E9=81=93=EF=BC=9A
>
> On 07/03/2023 16:35, Zheng Wang wrote:
> > In hantro_probe, vpu->watchdog_work is bound with
> > hantro_watchdog. Then hantro_end_prepare_run may
> > be called to start the work.
> >
> > If we close the file or remove the module which will
> > call hantro_release and hantro_remove to make cleanup,
> > there may be a unfinished work. The possible sequence
> > is as follows, which will cause a typical UAF bug.
> >
> > The same thing will happen in hantro_release, and use
> > ctx after freeing it.
> >
> > Fix it by canceling the work before cleanup in hantro_release.
> >
> > CPU0                  CPU1
> >
> >                     |hantro_watchdog
> > hantro_remove     |
> >   v4l2_m2m_release  |
> >     kfree(m2m_dev); |
> >                     |
> >                     | v4l2_m2m_get_curr_priv
> >                     |   m2m_dev->curr_ctx //use
> >
> > Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
> > ---
> >  drivers/media/platform/verisilicon/hantro_drv.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/media/platform/verisilicon/hantro_drv.c b/drivers/=
media/platform/verisilicon/hantro_drv.c
> > index b0aeedae7b65..cf00ccaa7829 100644
> > --- a/drivers/media/platform/verisilicon/hantro_drv.c
> > +++ b/drivers/media/platform/verisilicon/hantro_drv.c
> > @@ -601,6 +601,7 @@ static int hantro_release(struct file *filp)
> >        * No need for extra locking because this was the last reference
> >        * to this file.
> >        */
> > +     cancel_delayed_work(&vpu->watchdog_work);
> >       v4l2_m2m_ctx_release(ctx->fh.m2m_ctx);
> >       v4l2_fh_del(&ctx->fh);
> >       v4l2_fh_exit(&ctx->fh);
>
> drivers/media/platform/verisilicon/hantro_drv.c: In function =E2=80=98han=
tro_release=E2=80=99:
> drivers/media/platform/verisilicon/hantro_drv.c:604:30: error: =E2=80=98v=
pu=E2=80=99 undeclared (first use in this function); did you mean =E2=80=98=
fpu=E2=80=99?
>   604 |         cancel_delayed_work(&vpu->watchdog_work);
>       |                              ^~~
>       |                              fpu
> drivers/media/platform/verisilicon/hantro_drv.c:604:30: note: each undecl=
ared identifier is reported only once for each function it appears in
>
> You clearly didn't compile this patch!
>
Sorry for my mistake. I was hurried to report the issue and discuss
with developer to confirm it . I'll complete it and test it locally.

Best regards,
Zheng