Re: [PATCH] media: hantro: fix use after free bug in hantro_release due to race condition

[Zheng Hacker]

Hans Verkuil <hverkuil@xxxxxxxxx> 于2023年3月13日周一 21:17写道：
>
> 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@xxxxxxx>
> > ---
> >  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 ‘hantro_release’:
> drivers/media/platform/verisilicon/hantro_drv.c:604:30: error: ‘vpu’ undeclared (first use in this function); did you mean ‘fpu’?
>   604 |         cancel_delayed_work(&vpu->watchdog_work);
>       |                              ^~~
>       |                              fpu
> drivers/media/platform/verisilicon/hantro_drv.c:604:30: note: each undeclared 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