[FFmpeg-devel] [PATCH] avcodec/vp3: Check that there will be sufficient input for the coded fragments in unpack_superblocks()

[wm4]

On Sat,  5 May 2018 21:10:06 +0200
Michael Niedermayer <michael at niedermayer.cc> wrote:

> Fixes: Timeout
> Fixes: 6292/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_VP3_fuzzer-4871218218926080
> 
> 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/vp3.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/libavcodec/vp3.c b/libavcodec/vp3.c
> index 1d83753314..fcc19a627b 100644
> --- a/libavcodec/vp3.c
> +++ b/libavcodec/vp3.c
> @@ -543,7 +543,11 @@ static int unpack_superblocks(Vp3DecodeContext *s, GetBitContext *gb)
>                                           : s->y_superblock_count);
>          int num_coded_frags = 0;
>  
> -        for (i = sb_start; i < sb_end && get_bits_left(gb) > 0; i++) {
> +        for (i = sb_start; i < sb_end; i++) {
> +            if (get_bits_left(gb) < ((s->total_num_coded_frags + num_coded_frags) >> 2)) {
> +                av_log(s->avctx, AV_LOG_ERROR, "Insufficient input data for coded fragments\n");
> +                return AVERROR_INVALIDDATA;
> +            }
>              /* iterate through all 16 fragments in a superblock */
>              for (j = 0; j < 16; j++) {
>                  /* if the fragment is in bounds, check its coding status */

The log message is pointless bloat.