[FFmpeg-devel] [PATCH 2/4] avformat/rpl: Use 64bit in bitrate computation and check it

[Andreas Rheinhardt]

Michael Niedermayer:
> Fixes: signed integer overflow: 777777776 * 4 cannot be represented in type 'int'
> Fixes: 29102/clusterfuzz-testcase-minimized-ffmpeg_dem_RPL_fuzzer-6726188921913344
> 
> 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/rpl.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/libavformat/rpl.c b/libavformat/rpl.c
> index b98488c7b1..558e5718ba 100644
> --- a/libavformat/rpl.c
> +++ b/libavformat/rpl.c
> @@ -207,8 +207,10 @@ static int rpl_read_header(AVFormatContext *s)
>              ast->codecpar->bits_per_coded_sample = 4;
>  
>          ast->codecpar->bit_rate = ast->codecpar->sample_rate *
> -                                  ast->codecpar->bits_per_coded_sample *
> -                                  ast->codecpar->channels;
> +                                  (int64_t)ast->codecpar->bits_per_coded_sample;
> +        if (ast->codecpar->bit_rate > INT64_MAX / ast->codecpar->channels)
> +            return AVERROR_INVALIDDATA;
> +        ast->codecpar->bit_rate *= ast->codecpar->channels;
>  
>          ast->codecpar->codec_id = AV_CODEC_ID_NONE;
>          switch (audio_format) {
> 
read_line_and_int() can return zero and so you must not divide by
channels. (Something like __builtin_smulll_overflow() might be
advantageous here.)

- Andreas