From a1736926e9ae51706b537776722e816a4d1f6b36 Mon Sep 17 00:00:00 2001
From: Michael Niedermayer <michaelni@gmx.at>
Date: Mon, 29 Jun 2015 21:57:12 +0200
Subject: [PATCH] avcodec/pngdec: Require a IHDR chunk before fctl

This is required by the APNG spec

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
---
 libavcodec/pngdec.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/libavcodec/pngdec.c b/libavcodec/pngdec.c
index f8b398ffde..85bc447a81 100644
--- a/libavcodec/pngdec.c
+++ b/libavcodec/pngdec.c
@@ -824,6 +824,11 @@ static int decode_fctl_chunk(AVCodecContext *avctx, PNGDecContext *s,
     if (length != 26)
         return AVERROR_INVALIDDATA;
 
+    if (!(s->state & PNG_IHDR)) {
+        av_log(avctx, AV_LOG_ERROR, "fctl before IHDR\n");
+        return AVERROR_INVALIDDATA;
+    }
+
     s->last_w = s->cur_w;
     s->last_h = s->cur_h;
     s->last_x_offset = s->x_offset;