On Mon, Jan 6, 2014 at 8:36 AM, Anton Khirnov <[email protected]> wrote:
> An invalid VUI is not considered a fatal error, so the SPS containing it
> may still be used. Leaving an invalid value of num_reorder_frames there
> can result in writing over the bounds of H264Context.delayed_pic.
>
> Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
> CC:[email protected]
> ---
>  libavcodec/h264_ps.c |    1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/libavcodec/h264_ps.c b/libavcodec/h264_ps.c
> index 9eb252d..b5feff2 100644
> --- a/libavcodec/h264_ps.c
> +++ b/libavcodec/h264_ps.c
> @@ -223,6 +223,7 @@ static inline int decode_vui_parameters(H264Context *h, 
> SPS *sps)
>
>          if (sps->num_reorder_frames > 16U
>              /* max_dec_frame_buffering || max_dec_frame_buffering > 16 */) {
> +            sps->num_reorder_frames = 16;
>              av_log(h->avctx, AV_LOG_ERROR,
>                     "illegal num_reorder_frames %d\n", 
> sps->num_reorder_frames);
>              return AVERROR_INVALIDDATA;

I'd move the error message after the initialization and mention that
we clip it. This is so that log contains the real decoded value and
also because 16 is actually a legal value.
Extra bonus points if you comment that that 16 corresponds to MaxDpbFrames.
Vittorio
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