Re: [FFmpeg-devel] [PATCH 02/13] avformat/mxfdec: Check run_in to fit in int and be valid

["Tomas Härdin" <tjoppen@acc.umu.se>]

sön 2022-09-18 klockan 19:13 +0200 skrev Michael Niedermayer:
> Fixes: signed integer overflow: 9223372036854775807 - -2146905566
> cannot be represented in type 'long'
> Fixes: 50993/clusterfuzz-testcase-minimized-ffmpeg_dem_MXF_fuzzer-
> 6570996594769920
> 
> Found-by: continuous fuzzing process 
> https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>  libavformat/mxfdec.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/libavformat/mxfdec.c b/libavformat/mxfdec.c
> index e63e803aa56..da81fea3bc1 100644
> --- a/libavformat/mxfdec.c
> +++ b/libavformat/mxfdec.c
> @@ -3681,6 +3681,7 @@ static int mxf_read_header(AVFormatContext *s)
>      KLVPacket klv;
>      int64_t essence_offset = 0;
>      int ret;
> +    int64_t run_in;
>  
>      mxf->last_forward_tell = INT64_MAX;
>  
> @@ -3690,7 +3691,10 @@ static int mxf_read_header(AVFormatContext *s)
>      }
>      avio_seek(s->pb, -14, SEEK_CUR);
>      mxf->fc = s;
> -    mxf->run_in = avio_tell(s->pb);
> +    run_in = avio_tell(s->pb);
> +    if (run_in < 0 || run_in != (int)run_in)

run_in > INT_MAX is more clear

It strikes me that run_in is also used in lots of places in the demuxer
without checking for overflow

/Tomas

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