Re: [FFmpeg-devel] [PATCH] Check codec_whitelist before reinitializing AVCtx.priv_data.

[Dale Curtis <dalecurtis@chromium.org>]

On Wed, Jul 31, 2024 at 4:32 AM Anton Khirnov <anton@khirnov.net> wrote:

> Quoting Dale Curtis (2024-07-31 01:14:13)
> > I realized there are a couple more allocations that can be skipped here
> > when a codec is not on the allow list. Here's the updated patch.
> >
> > - dale
> >
> > On Mon, Jul 29, 2024 at 10:19 AM Dale Curtis <dalecurtis@chromium.org>
> > wrote:
> >
> > > This ensures that if a codec isn't on codec_whitelist, its VUI
> > > information can still be populated during find_stream_info()
> > > via parsers.
> > >
> > > Signed-off-by: Dale Curtis <dalecurtis@chromium.org>
> > > ---
> > >  libavcodec/avcodec.c | 12 ++++++------
> > >  1 file changed, 6 insertions(+), 6 deletions(-)
> > >
> > >
> >
> > From f87042d77d13c4c45f4b800146dc16347c1007d4 Mon Sep 17 00:00:00 2001
> > From: Dale Curtis <dalecurtis@chromium.org>
> > Date: Tue, 30 Jul 2024 23:12:21 +0000
> > Subject: [PATCH] Check codec_whitelist before reinitializing
> AVCtx.priv_data.
> >
> > This ensures that if a codec isn't on codec_whitelist, its VUI
> > information can still be populated during find_stream_info()
> > via parsers.
>
> Can you elaborate on this?
>

The current code reinitializes the private data structures then checks the
whitelist. If the private data section had already been filled out, it ends
up being overwritten causing find_stream_info to drop side channel data.


> >
> > Signed-off-by: Dale Curtis <dalecurtis@chromium.org>
> > ---
> >  libavcodec/avcodec.c | 11 +++++------
> >  1 file changed, 5 insertions(+), 6 deletions(-)
> >
> > diff --git a/libavcodec/avcodec.c b/libavcodec/avcodec.c
> > index 214dca4566..1f9b3eb360 100644
> > --- a/libavcodec/avcodec.c
> > +++ b/libavcodec/avcodec.c
> > @@ -174,6 +174,11 @@ int attribute_align_arg
> avcodec_open2(AVCodecContext *avctx, const AVCodec *code
> >      if (avctx->extradata_size < 0 || avctx->extradata_size >=
> FF_MAX_EXTRADATA_SIZE)
> >          return AVERROR(EINVAL);
> >
> > +    if (avctx->codec_whitelist && av_match_list(codec->name,
> avctx->codec_whitelist, ',') <= 0) {
> > +        av_log(avctx, AV_LOG_ERROR, "Codec (%s) not on whitelist
> \'%s\'\n", codec->name, avctx->codec_whitelist);
> > +        return AVERROR(EINVAL);
> > +    }
>
> I think this will break the case where the whitelist is provided in the
> options dictionary, as it's not applied yet at this point.
>

I just copied the existing code a few lines up, so it seems ancillary to
this patch, but I can fix it in this one too if you want.


>
> --
> Anton Khirnov
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