Re: [FFmpeg-devel] [PATCH 1/2] avformat/vividas: Check packet size

[Anton Khirnov <anton@khirnov.net>]

Quoting Michael Niedermayer (2022-09-22 20:08:51)
> Fixes: signed integer overflow: 119760682 - -2084600173 cannot be represented in type 'int'
> Fixes: 50993/clusterfuzz-testcase-minimized-ffmpeg_dem_VIVIDAS_fuzzer-6745781167587328
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>  libavformat/vividas.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/libavformat/vividas.c b/libavformat/vividas.c
> index e9954f73ed0..e8efe49a5c0 100644
> --- a/libavformat/vividas.c
> +++ b/libavformat/vividas.c
> @@ -683,6 +683,7 @@ static int viv_read_packet(AVFormatContext *s,
>  
>      if (viv->sb_entries[viv->current_sb_entry].flag == 0) {
>          uint64_t v_size = ffio_read_varlen(pb);
> +        int last, last_start;
>  
>          if (!viv->num_audio)
>              return AVERROR_INVALIDDATA;
> @@ -704,14 +705,22 @@ static int viv_read_packet(AVFormatContext *s,
>              start = ffio_read_varlen(pb);
>              pcm_bytes = ffio_read_varlen(pb);
>  
> -            if (i > 0 && start == 0)
> -                break;
> +            if (i > 0) {
> +                if (start == 0)
> +                    break;
> +                if (start < last || start - (unsigned)last > INT_MAX)

What is the second condition for?

-- 
Anton Khirnov
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