[FFmpeg-devel] [PATCH] avcodec/alsdec: Consider frame_size in ra_block handling

[Thilo Borgmann]

Am 20.06.19 um 16:17 schrieb Michael Niedermayer:
> Fixes: out of array access
> Fixes: 15277/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ALS_fuzzer-5184853437317120
> 
> 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/alsdec.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/libavcodec/alsdec.c b/libavcodec/alsdec.c
> index e50a287f19..f94086efcb 100644
> --- a/libavcodec/alsdec.c
> +++ b/libavcodec/alsdec.c
> @@ -789,14 +789,15 @@ static int read_var_block_data(ALSDecContext *ctx, ALSBlockData *bd)
>  
>      // read first value and residuals in case of a random access block
>      if (bd->ra_block) {
> -        if (opt_order)

pls add a comment here like:

// limit possibly corrupted opt_order

and push if tested.

> +        int len = FFMIN(opt_order, sconf->frame_length);
> +        if (len)
>              bd->raw_samples[0] = decode_rice(gb, avctx->bits_per_raw_sample - 4);
> -        if (opt_order > 1)
> +        if (len > 1)
>              bd->raw_samples[1] = decode_rice(gb, FFMIN(s[0] + 3, ctx->s_max));
> -        if (opt_order > 2)
> +        if (len > 2)
>              bd->raw_samples[2] = decode_rice(gb, FFMIN(s[0] + 1, ctx->s_max));
>  
> -        start = FFMIN(opt_order, 3);
> +        start = FFMIN(len, 3);
>      }
>  
>      // read all residuals
> 

-Thilo