[FFmpeg-devel] [PATCH] avutil/hwcontext_dxva2: Don't improperly free IDirect3DSurface9 objects

[Steven Liu]

2017-05-16 20:23 GMT+08:00 wm4 <nfxjfg at googlemail.com>:

> On Tue, 16 May 2017 05:04:36 -0700
> Aaron Levinson <alevinsn at aracnet.com> wrote:
>
> > Add dxva2_pool_release_dummy() and use it in call to
> > av_buffer_create() in dxva2_pool_alloc().
> >
> > Prior to this change, av_buffer_create() was called with NULL for the
> > third argument, which indicates that av_buffer_default_free() should
> > be used to free the buffer's data.  Eventually, it gets to
> > buffer_pool_free() and calls buf->free() on a surface object (which is
> > av_buffer_default_free()).
> >
> > This can result in a crash when the debug version of the C-runtime is
> > used on Windows.  While it doesn't appear to result in a crash when
> > the release version of the C-runtime is used on Windows, it likely
> > results in memory corruption, since av_free() is being called on
> > memory that was allocated using
> > IDirectXVideoAccelerationService::CreateSurface().
> >
> > Signed-off-by: Aaron Levinson <alevinsn at aracnet.com>
> > ---
> >  libavutil/hwcontext_dxva2.c | 9 ++++++++-
> >  1 file changed, 8 insertions(+), 1 deletion(-)
> >
> > diff --git a/libavutil/hwcontext_dxva2.c b/libavutil/hwcontext_dxva2.c
> > index 4ed0d56..6c41788 100644
> > --- a/libavutil/hwcontext_dxva2.c
> > +++ b/libavutil/hwcontext_dxva2.c
> > @@ -121,6 +121,13 @@ static void dxva2_frames_uninit(AVHWFramesContext
> *ctx)
> >      }
> >  }
> >
> > +static void dxva2_pool_release_dummy(void *opaque, uint8_t *data)
> > +{
> > +    // important not to free anything here--data is a surface object
> > +    // associated with the call to CreateSurface(), and these surfaces
> are
> > +    // released in dxva2_frames_uninit()
> > +}
> > +
> >  static AVBufferRef *dxva2_pool_alloc(void *opaque, int size)
> >  {
> >      AVHWFramesContext      *ctx = (AVHWFramesContext*)opaque;
> > @@ -130,7 +137,7 @@ static AVBufferRef *dxva2_pool_alloc(void *opaque,
> int size)
> >      if (s->nb_surfaces_used < hwctx->nb_surfaces) {
> >          s->nb_surfaces_used++;
> >          return av_buffer_create((uint8_t*)s->surfaces_internal[s->nb_surfaces_used
> - 1],
> > -                                sizeof(*hwctx->surfaces), NULL, 0, 0);
> > +                                sizeof(*hwctx->surfaces),
> dxva2_pool_release_dummy, 0, 0);
> >      }
> >
> >      return NULL;
>
> LGTM
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>

LGTM