[FFmpeg-devel] [PATCH 1/2] avformat/matroskadec: Check desc_bytes

[Andreas Rheinhardt]

Michael Niedermayer:
> Fixes: Division by 0
> Fixes: 44035/clusterfuzz-testcase-minimized-ffmpeg_dem_WEBM_DASH_MANIFEST_fuzzer-4826721386364928
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> ---
>  libavformat/matroskadec.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
> index 5a9acfb247..f433391a16 100644
> --- a/libavformat/matroskadec.c
> +++ b/libavformat/matroskadec.c
> @@ -4216,6 +4216,8 @@ static int64_t webm_dash_manifest_compute_bandwidth(AVFormatContext *s, int64_t
>              do {
>                  int64_t desc_bytes = desc_end.end_offset - desc_beg.start_offset;
>                  int64_t desc_ns = desc_end.end_time_ns - desc_beg.start_time_ns;
> +                if (desc_bytes <= 0)
> +                    return -1;
>                  double desc_sec = desc_ns / nano_seconds_per_second;
>                  double calc_bits_per_second = (desc_bytes * 8) / desc_sec;
>  

This should give a declaration-after-statement error.

- Andreas