Re: [FFmpeg-devel] [PATCH 1/4] avcodec/j2kenc: Merge dwt_norm into lambda

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

Michael Niedermayer:
> This moves computations out of a loop
> 
> Fixes: signed integer overflow: 31665934879948800 * 9998 cannot be represented in type 'long'
> Fixes: 69024/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_JPEG2000_fuzzer-5949662967169024
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>  libavcodec/j2kenc.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/libavcodec/j2kenc.c b/libavcodec/j2kenc.c
> index 8cf82f7216c..91e66d81048 100644
> --- a/libavcodec/j2kenc.c
> +++ b/libavcodec/j2kenc.c
> @@ -1349,7 +1349,7 @@ static void makelayers(Jpeg2000EncoderContext *s, Jpeg2000Tile *tile)
>      }
>  }
>  
> -static int getcut(Jpeg2000Cblk *cblk, uint64_t lambda, int dwt_norm)
> +static int getcut(Jpeg2000Cblk *cblk, uint64_t lambda)
>  {
>      int passno, res = 0;
>      for (passno = 0; passno < cblk->npasses; passno++){
> @@ -1361,7 +1361,7 @@ static int getcut(Jpeg2000Cblk *cblk, uint64_t lambda, int dwt_norm)
>          dd = cblk->passes[passno].disto
>             - (res ? cblk->passes[res-1].disto : 0);
>  
> -        if (((dd * dwt_norm) >> WMSEDEC_SHIFT) * dwt_norm >= dr * lambda)
> +        if (dd  >= dr * lambda)
>              res = passno+1;
>      }
>      return res;
> @@ -1384,11 +1384,12 @@ static void truncpasses(Jpeg2000EncoderContext *s, Jpeg2000Tile *tile)
>                      Jpeg2000Band *band = reslevel->band + bandno;
>                      Jpeg2000Prec *prec = band->prec + precno;
>  
> +                    int64_t dwt_norm = dwt_norms[codsty->transform == FF_DWT53][bandpos][lev] * (int64_t)band->i_stepsize >> 15;
> +                    int64_t lambda_prime = av_rescale(s->lambda, 1 << WMSEDEC_SHIFT, dwt_norm * dwt_norm);
>                      for (cblkno = 0; cblkno < prec->nb_codeblocks_height * prec->nb_codeblocks_width; cblkno++){
>                          Jpeg2000Cblk *cblk = prec->cblk + cblkno;
>  
> -                        cblk->ninclpasses = getcut(cblk, s->lambda,
> -                                (int64_t)dwt_norms[codsty->transform == FF_DWT53][bandpos][lev] * (int64_t)band->i_stepsize >> 15);
> +                        cblk->ninclpasses = getcut(cblk, lambda_prime);
>                          cblk->layers[0].data_start = cblk->data;
>                          cblk->layers[0].cum_passes = cblk->ninclpasses;
>                          cblk->layers[0].npasses = cblk->ninclpasses;

Does this also fix the UB in the vsynth*-jpeg2000-yuva444p16 tests?

- Andreas

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