[FFmpeg-devel] [PATCH] avcodec/av1dec: Always set ret before goto end

[Hendrik Leppkes]

On Thu, May 2, 2024 at 10:22 AM Andreas Rheinhardt
<andreas.rheinhardt at outlook.com> wrote:
>
> Before 0f8763fbea4e8816cd54c2a481d4c048fec58394, av1_frame_ref()
> and update_reference_list() could fail and therefore needed to
> be checked, which incidentally set ret. This is no longer happening,
> leading to a potential use of an uninitialized value which is
> also the subject of Coverity ticket #1596605.
>
> Fix this by always setting ret before goto end; do not return
> some random ancient value.
>
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at outlook.com>
> ---
>  libavcodec/av1dec.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/libavcodec/av1dec.c b/libavcodec/av1dec.c
> index 79a30a114d..c3f255a29a 100644
> --- a/libavcodec/av1dec.c
> +++ b/libavcodec/av1dec.c
> @@ -1335,6 +1335,12 @@ static int av1_receive_frame_internal(AVCodecContext *avctx, AVFrame *frame)
>                      ret = set_output_frame(avctx, frame);
>                      if (ret < 0)
>                          av_log(avctx, AV_LOG_ERROR, "Set output frame error.\n");
> +                } else {
> +                    // CBS checks for us that the frame to be shown actually existed
> +                    // in the bitstream; if it doesn't it could be e.g. due to
> +                    // skip_frame setting. Return EAGAIN to indicate that we are
> +                    // currently unable to produce output.
> +                    ret = AVERROR(EAGAIN);
>                  }
>

In the vein of this comment, set_output_frame will also return 0
without returning a frame in some cases - eg. with multiple layers.
Should this equally return EAGAIN rather than claiming success without
a frame?

- Hendrik