From 3b50e238b2d7ec2a3d46aa428694e02479477b7a Mon Sep 17 00:00:00 2001
From: "Christoph M. Becker" <cmbecker69@gmx.de>
Date: Wed, 29 Nov 2017 18:52:33 +0100
Subject: [PATCH 1/1] Fixed bug #75571: Potential infinite loop in
 gdImageCreateFromGifCtx

Due to a signedness confusion in `GetCode_` a corrupt GIF file can
trigger an infinite loop.  Furthermore we make sure that a GIF without
any palette entries is treated as invalid *after* open palette entries
have been removed.

(cherry picked from commit 8d6e9588671136837533fe3785657c31c5b52767)
Index: libgd2-2.2.5/src/gd_gif_in.c
===================================================================
--- libgd2-2.2.5.orig/src/gd_gif_in.c
+++ libgd2-2.2.5/src/gd_gif_in.c
@@ -334,12 +334,6 @@ terminated:
 	if(!im) {
 		return 0;
 	}
-
-	if(!im->colorsTotal) {
-		gdImageDestroy(im);
-		return 0;
-	}
-
 	/* Check for open colors at the end, so
 	 * we can reduce colorsTotal and ultimately
 	 * BitsPerPixel */
@@ -351,6 +345,10 @@ terminated:
 		}
 	}
 
+	if(!im->colorsTotal) {
+		gdImageDestroy(im);
+		return 0;
+	}
 	return im;
 }