[FFmpeg-devel] [PATCH 1/2] avformat/mvdec: Fix integer overflow with billions of channels

Andreas Rheinhardt andreas.rheinhardt at gmail.com
Tue Jun 23 06:22:53 EEST 2020


Michael Niedermayer:
> Fixes: signed integer overflow: 1394614304 * 2 cannot be represented in type 'int'
> Fixes: 23491/clusterfuzz-testcase-minimized-ffmpeg_DEMUXER_fuzzer-5697377020411904
> 
> 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/mvdec.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/libavformat/mvdec.c b/libavformat/mvdec.c
> index 64166a84b1..fa87384c6b 100644
> --- a/libavformat/mvdec.c
> +++ b/libavformat/mvdec.c
> @@ -355,7 +355,7 @@ static int mv_read_header(AVFormatContext *avctx)
>              avio_skip(pb, 8);
>              av_add_index_entry(ast, pos, timestamp, asize, 0, AVINDEX_KEYFRAME);
>              av_add_index_entry(vst, pos + asize, i, vsize, 0, AVINDEX_KEYFRAME);
> -            timestamp += asize / (ast->codecpar->channels * 2);
> +            timestamp += asize / (ast->codecpar->channels * 2LL);
>          }
>      } else if (!version && avio_rb16(pb) == 3) {
>          avio_skip(pb, 4);
> 
You could avoid using 64 the 64 bit intermediate by multiplying with 2U
or by using asize / ast->codecpar->channels / 2.

Whatever you prefer should also be applied to read_index.

- Andreas


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