Hi

On Fri, May 03, 2024 at 12:26:52PM +0000, Niklas Haas wrote:
> ffmpeg | branch: master | Niklas Haas <git@haasn.dev> | Wed Apr 24 12:03:00 2024 +0200| [bb8044581366fe286e16b14515d873979133dbda] | committer: Niklas Haas
> 
> avfilter/vf_scale: add optional "ref" input
> 
> This is automatically enabled if the width/height expressions reference
> any ref_* variable. This will ultimately serve as a more principled
> replacement for the fundamentally broken scale2ref.
> 
> See-Also: https://trac.ffmpeg.org/ticket/10795
> 
> > http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=bb8044581366fe286e16b14515d873979133dbda
[...]
>      ret = scale_frame(ctx->inputs[0], in, &out);
>      if (out) {
> @@ -933,6 +1053,9 @@ static int do_scale(FFFrameSync *fs)
>          return ff_filter_frame(outlink, out);
>      }
>  
> +err:
> +    if (ret < 0)
> +        av_frame_free(&in);

double free
this can be already freed in

    out = ff_get_video_buffer(outlink, outlink->w, outlink->h);
    if (!out) {
        av_frame_free(&in);
        return AVERROR(ENOMEM);
    }

Also the interaction of these functions is a bit complex
(which is why iam not proposing a fix but rather point this out
 also as you are working on the scale code ...)
 Found by coverity: CID1596782 Double free

thx

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