avfilter/af_stereotools: check s->length size

Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavfilter/af_stereotools.c

@@ -110,6 +110,10 @@ static int config_input(AVFilterLink *inlink)
     StereoToolsContext *s = ctx->priv;
 
     s->length = 2 * inlink->sample_rate * 0.05;
+    if (s->length <= 1 && s->length & 1) {
+        av_log(ctx, AV_LOG_ERROR, "sample rate is too small\n");
+        return AVERROR(EINVAL);
+    }
     s->buffer = av_calloc(s->length, sizeof(*s->buffer));
     if (!s->buffer)
         return AVERROR(ENOMEM);