[FFmpeg-devel] [RFC] d3dva security hw+threads

[Anton Khirnov]

Quoting Soft Works (2022-09-04 09:43:36)
> 
> 
> > -----Original Message-----
> > From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of
> > Anton Khirnov
> > Sent: Sunday, September 4, 2022 8:58 AM
> > To: FFmpeg development discussions and patches <ffmpeg-
> > devel at ffmpeg.org>
> > Subject: Re: [FFmpeg-devel] [RFC] d3dva security hw+threads
> > 
> > Quoting Timo Rothenpieler (2022-09-02 01:46:59)
> > > On 02.09.2022 01:32, Michael Niedermayer wrote:
> > > > Hi all
> > > >
> > > > Theres a use after free issue in H.264 Decoding on d3d11va with
> > multiple threads
> > > > I dont have the hardware/platform nor do i know the hw decoding
> > code so i made
> > > > no attempt to fix this beyond asking others to ...
> > >
> > > hwaccel with multiple threads being broken is not exactly a
> > surprise.
> > > So we could just disable that, and always have it be one single
> > thread?
> > 
> > We are already disabling it in a way - the frame threading code
> > ensures
> > that threads run one at a time when hwaccel is being used.
> 
> 
> Is there a described way to repro? I would try whether it still 
> happens after removing the lock code in hwcontext_d3d11va.c.
> Those locks are not really needed and might prevent release 
> of dx11 resources in proper order. It's a guess only but 
> easy to try.

The problem is not in d3d11 locking code, but in the generic code that
does not have clear enough ownership rules. Steve already tested that my
patch from Friday fixes this.

-- 
Anton Khirnov