[FFmpeg-devel] [PATCH 4/5] avcodec/alac: Check for bps of 0

James Almer jamrial at gmail.com
Fri Aug 23 17:20:48 EEST 2019


On 8/8/2019 8:23 PM, Michael Niedermayer wrote:
> Fixes: shift exponent 32 is too large for 32-bit type 'unsigned int'
> Fixes: 15764/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ALAC_fuzzer-5102101203517440
> 
> 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/alac.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/libavcodec/alac.c b/libavcodec/alac.c
> index 6086e2caa8..1196925aa7 100644
> --- a/libavcodec/alac.c
> +++ b/libavcodec/alac.c
> @@ -250,7 +250,7 @@ static int decode_element(AVCodecContext *avctx, AVFrame *frame, int ch_index,
>  
>      alac->extra_bits = get_bits(&alac->gb, 2) << 3;
>      bps = alac->sample_size - alac->extra_bits + channels - 1;
> -    if (bps > 32U) {
> +    if (bps > 32 || bps < 1) {
>          avpriv_report_missing_feature(avctx, "bps %d", bps);
>          return AVERROR_PATCHWELCOME;

bps 0 (or negative) is obviously a broken file, so asking for a sample
is pointless. Just return invalid data in those cases, and leave this
check for > 32.

>      }
> 



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