From 631856a2021d60d29e96d07872c06246eff25a96 Mon Sep 17 00:00:00 2001
From: Nils Philippsen <nils@redhat.com>
Date: Fri, 12 Aug 2011 14:44:52 +0200
Subject: [PATCH] patch: gif-load

Squashed commit of the following:

commit 366d6b546e8fb91909550a61abeafc11672667c4
Author: Nils Philippsen <nils@redhat.com>
Date:   Thu Aug 4 12:51:42 2011 +0200

    file-gif-load: fix heap corruption and buffer overflow (CVE-2011-2896)
    (cherry picked from commit 376ad788c1a1c31d40f18494889c383f6909ebfc)

commit 3c5864851ea5fe8f89d273ee8ac4df0c1101b315
Author: Nils Philippsen <nils@redhat.com>
Date:   Thu Aug 4 12:47:44 2011 +0200

    file-gif-load: ensure return value of LZWReadByte() is <= 255
    (cherry picked from commit b1a3de761362db982c0ddfaff60ab4a3c4267f32)
---
 plug-ins/common/file-gif-load.c |   25 ++++++++++++++-----------
 1 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/plug-ins/common/file-gif-load.c b/plug-ins/common/file-gif-load.c
index 9a0720b..8460ec0 100644
--- a/plug-ins/common/file-gif-load.c
+++ b/plug-ins/common/file-gif-load.c
@@ -697,7 +697,8 @@ LZWReadByte (FILE *fd,
   static gint firstcode, oldcode;
   static gint clear_code, end_code;
   static gint table[2][(1 << MAX_LZW_BITS)];
-  static gint stack[(1 << (MAX_LZW_BITS)) * 2], *sp;
+#define STACK_SIZE ((1 << (MAX_LZW_BITS)) * 2)
+  static gint stack[STACK_SIZE], *sp;
   gint        i;
 
   if (just_reset_LZW)
@@ -743,11 +744,11 @@ LZWReadByte (FILE *fd,
         }
       while (firstcode == clear_code);
 
-      return firstcode;
+      return firstcode & 255;
     }
 
   if (sp > stack)
-    return *--sp;
+    return (*--sp) & 255;
 
   while ((code = GetCode (fd, code_size, FALSE)) >= 0)
     {
@@ -770,9 +771,9 @@ LZWReadByte (FILE *fd,
           sp            = stack;
           firstcode     = oldcode = GetCode (fd, code_size, FALSE);
 
-          return firstcode;
+          return firstcode & 255;
         }
-      else if (code == end_code)
+      else if (code == end_code || code > max_code)
         {
           gint   count;
           guchar buf[260];
@@ -791,13 +792,14 @@ LZWReadByte (FILE *fd,
 
       incode = code;
 
-      if (code >= max_code)
+      if (code == max_code)
         {
-          *sp++ = firstcode;
+          if (sp < &(stack[STACK_SIZE]))
+            *sp++ = firstcode;
           code = oldcode;
         }
 
-      while (code >= clear_code)
+      while (code >= clear_code && sp < &(stack[STACK_SIZE]))
         {
           *sp++ = table[1][code];
           if (code == table[0][code])
@@ -808,7 +810,8 @@ LZWReadByte (FILE *fd,
           code = table[0][code];
         }
 
-      *sp++ = firstcode = table[1][code];
+      if (sp < &(stack[STACK_SIZE]))
+        *sp++ = firstcode = table[1][code];
 
       if ((code = max_code) < (1 << MAX_LZW_BITS))
         {
@@ -826,10 +829,10 @@ LZWReadByte (FILE *fd,
       oldcode = incode;
 
       if (sp > stack)
-        return *--sp;
+        return (*--sp) & 255;
     }
 
-  return code;
+  return code & 255;
 }
 
 static gint32
-- 
1.7.6