From 17fc6d054e41444b64b3f56bdca60b2765402071 Mon Sep 17 00:00:00 2001
From: oehhar <harald.oehlmann@elmicron.de>
Date: Sun, 3 Feb 2019 11:21:11 +0000
Subject: [PATCH 644/693] gif read not complete on overflow image - information
 missinterpreted if following subimage is querried [4da2191b]

---
 generic/tkImgGIF.c  | 21 ++++++++++++++++++++-
 tests/imgPhoto.test | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 53 insertions(+), 1 deletion(-)

diff --git a/generic/tkImgGIF.c b/generic/tkImgGIF.c
index 7c4872bef..fa4b728d3 100644
--- a/generic/tkImgGIF.c
+++ b/generic/tkImgGIF.c
@@ -1034,7 +1034,7 @@ ReadImage(
     int transparent)
 {
     unsigned char initialCodeSize;
-    int xpos = 0, ypos = 0, pass = 0, i;
+    int xpos = 0, ypos = 0, pass = 0, i, count;
     register unsigned char *pixelPtr;
     static const int interlaceStep[] = { 8, 8, 4, 2 };
     static const int interlaceStart[] = { 0, 4, 2, 1 };
@@ -1252,6 +1252,25 @@ ReadImage(
 	}
 	pixelPtr = imagePtr + (ypos) * len * ((transparent>=0)?4:3);
     }
+
+    /*
+     * Now read until the final zero byte.
+     * It was observed that there might be 1 length blocks
+     * (test imgPhoto-14.1) which are not read.
+     *
+     * The field "stack" is abused for temporary buffer. it has 4096 bytes
+     * and we need 256.
+     * 
+     * Loop until we hit a 0 length block which is the end sign.
+     */
+    while ( 0 < (count = GetDataBlock(gifConfPtr, chan, stack)))
+    {
+	if (-1 == count ) {
+	    Tcl_SetObjResult(interp, Tcl_ObjPrintf(
+		    "error reading GIF image: %s", Tcl_PosixError(interp)));
+	    return TCL_ERROR;
+	}
+    }
     return TCL_OK;
 }
 
-- 
2.19.1

