[FFmpeg-devel] [PATCH 4/4] avcodec/sonic: Check channels before deallocating

[Andreas Rheinhardt]

Michael Niedermayer:
> Fixes: heap-buffer-overflow
> Fixes: 25744/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SONIC_fuzzer-5172961169113088
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> ---
>  libavcodec/sonic.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/libavcodec/sonic.c b/libavcodec/sonic.c
> index fa4ecc3a7a..d09de6156b 100644
> --- a/libavcodec/sonic.c
> +++ b/libavcodec/sonic.c
> @@ -980,12 +980,11 @@ static av_cold int sonic_decode_close(AVCodecContext *avctx)
>      av_freep(&s->int_samples);
>      av_freep(&s->tap_quant);
>      av_freep(&s->predictor_k);
> -
> -    for (i = 0; i < s->channels; i++)
> -    {
> -        av_freep(&s->predictor_state[i]);
> -        av_freep(&s->coded_samples[i]);
> -    }
> +    if (s->channels <= MAX_CHANNELS)
> +        for (i = 0; i < s->channels; i++) {
> +            av_freep(&s->predictor_state[i]);
> +            av_freep(&s->coded_samples[i]);
> +        }
>  
>      return 0;
>  }
> 
for (i = 0; i < MAX_CHANNELS; i++) would be simpler.
(Sorry for not noticing this before
7d91f9271ee336da93b6871bf3306348ac1595a7; I only tested that
everything's fine when one of the allocations is made to fail.)

- Andreas