diff --git a/contrib/gregbook/readpng.c b/contrib/gregbook/readpng.c
index e6a01c6f7..fad9b536a 100644
--- a/contrib/gregbook/readpng.c
+++ b/contrib/gregbook/readpng.c
@@ -4,7 +4,7 @@
 
   ---------------------------------------------------------------------------
 
-      Copyright (c) 1998-2007 Greg Roelofs.  All rights reserved.
+      Copyright (c) 1998-2007,2017 Greg Roelofs.  All rights reserved.
 
       This software is provided "as is," without warranty of any kind,
       express or implied.  In no event shall the author or contributors
diff --git a/contrib/gregbook/readpng2.c b/contrib/gregbook/readpng2.c
index 4d5e38fe2..5d13e1530 100644
--- a/contrib/gregbook/readpng2.c
+++ b/contrib/gregbook/readpng2.c
@@ -55,6 +55,7 @@
 
    Changelog:
      2015-11-12 - Check return value of png_get_bKGD() (Glenn R-P)
+     2017-04-22 - Guard against integer overflow (Glenn R-P)
 
   ---------------------------------------------------------------------------*/
 
diff --git a/contrib/gregbook/readppm.c b/contrib/gregbook/readppm.c
index 3a41f3e1d..52e702777 100644
--- a/contrib/gregbook/readppm.c
+++ b/contrib/gregbook/readppm.c
@@ -9,7 +9,7 @@
 
   ---------------------------------------------------------------------------
 
-      Copyright (c) 1998-2007 Greg Roelofs.  All rights reserved.
+      Copyright (c) 1998-2007,2017 Greg Roelofs.  All rights reserved.
 
       This software is provided "as is," without warranty of any kind,
       express or implied.  In no event shall the author or contributors
diff --git a/contrib/gregbook/rpng-win.c b/contrib/gregbook/rpng-win.c
index 313beaff1..4254c17ef 100644
--- a/contrib/gregbook/rpng-win.c
+++ b/contrib/gregbook/rpng-win.c
@@ -24,10 +24,11 @@
     - 1.10:  enabled "message window"/console (thanks to David Geldreich)
     - 2.00:  dual-licensed (added GNU GPL)
     - 2.01:  fixed improper display of usage screen on PNG error(s)
+    - 2.02:  check for integer overflow (Glenn R-P)
 
   ---------------------------------------------------------------------------
 
-      Copyright (c) 1998-2008 Greg Roelofs.  All rights reserved.
+      Copyright (c) 1998-2008, 2017 Greg Roelofs.  All rights reserved.
 
       This software is provided "as is," without warranty of any kind,
       express or implied.  In no event shall the author or contributors
diff --git a/contrib/gregbook/rpng-x.c b/contrib/gregbook/rpng-x.c
index ddd7c58d6..92effaa6d 100644
--- a/contrib/gregbook/rpng-x.c
+++ b/contrib/gregbook/rpng-x.c
@@ -28,10 +28,11 @@
     - 2.01:  fixed improper display of usage screen on PNG error(s)
     - 2.02:  Added "void(argc);" statement to quiet pedantic compiler warnings
              about unused variable (GR-P)
+    - 2.03:  check for integer overflow (Glenn R-P)
 
   ---------------------------------------------------------------------------
 
-      Copyright (c) 1998-2008 Greg Roelofs.  All rights reserved.
+      Copyright (c) 1998-2008, 2017 Greg Roelofs.  All rights reserved.
 
       This software is provided "as is," without warranty of any kind,
       express or implied.  In no event shall the author or contributors
diff --git a/contrib/gregbook/rpng2-win.c b/contrib/gregbook/rpng2-win.c
index 8720bb011..ed6b526ec 100644
--- a/contrib/gregbook/rpng2-win.c
+++ b/contrib/gregbook/rpng2-win.c
@@ -33,12 +33,11 @@
     - 2.02:  fixed improper display of usage screen on PNG error(s); fixed
               unexpected-EOF and file-read-error cases
     - 2.03:  removed runtime MMX-enabling/disabling and obsolete -mmx* options
-    - 2.04:
-             (GR-P)
+    - 2.04:  check for integer overflow (Glenn R-P)
 
   ---------------------------------------------------------------------------
 
-      Copyright (c) 1998-2008 Greg Roelofs.  All rights reserved.
+      Copyright (c) 1998-2008, 2017 Greg Roelofs.  All rights reserved.
 
       This software is provided "as is," without warranty of any kind,
       express or implied.  In no event shall the author or contributors
diff --git a/contrib/gregbook/rpng2-x.c b/contrib/gregbook/rpng2-x.c
index 2585203b4..af944c0f2 100644
--- a/contrib/gregbook/rpng2-x.c
+++ b/contrib/gregbook/rpng2-x.c
@@ -44,9 +44,11 @@
     - 2.04:  Added "void(foo);" statements to quiet pedantic compiler warnings
              about unused variables (GR-P)
     - 2.05:  Use nanosleep() instead of usleep(), which is deprecated (GR-P).
+    - 2.06:  check for integer overflow (Glenn R-P)
   ---------------------------------------------------------------------------
 
-      Copyright (c) 1998-2010, 2014-2015 Greg Roelofs.  All rights reserved.
+      Copyright (c) 1998-2010, 2014-2015, 2017 Greg Roelofs.  All rights
+      reserved.
 
       This software is provided "as is," without warranty of any kind,
       express or implied.  In no event shall the author or contributors
diff --git a/contrib/gregbook/wpng.c b/contrib/gregbook/wpng.c
index 3b5b8118d..a8f367fb8 100644
--- a/contrib/gregbook/wpng.c
+++ b/contrib/gregbook/wpng.c
@@ -29,6 +29,7 @@
     - 1.04:  fixed DOS/OS2/Win32 detection, including partial Cygwin fix
               (see http://home.att.net/~perlspinr/diffs/GregBook_cygwin.diff)
     - 2.00:  dual-licensed (added GNU GPL)
+    - 2.01:  check for integer overflow (Glenn R-P)
 
         [REPORTED BUG (win32 only):  "contrib/gregbook/wpng.c - cmd line
          dose not work!  In order to do something useful I needed to redirect
@@ -38,7 +39,7 @@
 
   ---------------------------------------------------------------------------
 
-      Copyright (c) 1998-2007 Greg Roelofs.  All rights reserved.
+      Copyright (c) 1998-2007, 2017 Greg Roelofs.  All rights reserved.
 
       This software is provided "as is," without warranty of any kind,
       express or implied.  In no event shall the author or contributors
@@ -705,14 +706,15 @@ int main(int argc, char **argv)
         ulg image_bytes;
 
         /* Guard against integer overflow */
-        if (wpng_info_height > ((size_t)(-1)/rowbytes) {
+        if (wpng_info_height > ((size_t)(-1)/rowbytes ||
+            wpng_info_height > ((ulg)(-1)/rowbytes) {
             fprintf(stderr, PROGNAME ":  image_data buffer too large\n");
             writepng_cleanup(&wpng_info);
             wpng_cleanup();
             exit(5);
         }
 
-        image_bytes = rowbytes * wpng_info.height;   /* overflow? */
+        image_bytes = rowbytes * wpng_info.height;
 
         wpng_info.image_data = (uch *)malloc(image_bytes);
         wpng_info.row_pointers = (uch **)malloc(wpng_info.height*sizeof(uch *));
diff --git a/contrib/gregbook/writepng.c b/contrib/gregbook/writepng.c
index c5c953479..055c74374 100644
--- a/contrib/gregbook/writepng.c
+++ b/contrib/gregbook/writepng.c
@@ -4,7 +4,7 @@
 
   ---------------------------------------------------------------------------
 
-      Copyright (c) 1998-2007 Greg Roelofs.  All rights reserved.
+      Copyright (c) 1998-2007, 2017 Greg Roelofs.  All rights reserved.
 
       This software is provided "as is," without warranty of any kind,
       express or implied.  In no event shall the author or contributors
diff --git a/contrib/pngminus/png2pnm.c b/contrib/pngminus/png2pnm.c
index 4f01a5ebd..c9f16237d 100644
--- a/contrib/pngminus/png2pnm.c
+++ b/contrib/pngminus/png2pnm.c
@@ -3,6 +3,7 @@
  *  copyright (C) 1999 by Willem van Schaik <willem at schaik.com>
  *
  *  version 1.0 - 1999.10.15 - First version.
+ *          1.1 - 2017.04.22 - Add buffer-size check (Glenn Randers-Pehrson)
  *
  *  Permission to use, copy, modify, and distribute this software and
  *  its documentation for any purpose and without fee is hereby granted,
diff --git a/contrib/pngminus/pnm2png.c b/contrib/pngminus/pnm2png.c
index 7346d57a7..adc32069d 100644
--- a/contrib/pngminus/pnm2png.c
+++ b/contrib/pngminus/pnm2png.c
@@ -4,6 +4,7 @@
  *
  *  version 1.0 - 1999.10.15 - First version.
  *  version 1.1 - 2015.07.29 - Fixed leaks (Glenn Randers-Pehrson)
+ *  version 1.2 - 2017.04.22 - Add buffer-size check
  *
  *  Permission to use, copy, modify, and distribute this software and
  *  its documentation for any purpose and without fee is hereby granted,
diff --git a/contrib/visupng/PngFile.c b/contrib/visupng/PngFile.c
index dde2a421d..d46318f44 100644
--- a/contrib/visupng/PngFile.c
+++ b/contrib/visupng/PngFile.c
@@ -2,7 +2,7 @@
  *  PNGFILE.C -- Image File Functions
  *-------------------------------------
  *
- * Copyright 2000, Willem van Schaik.
+ * Copyright 2000,2017 Willem van Schaik.
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
diff --git a/contrib/visupng/VisualPng.c b/contrib/visupng/VisualPng.c
index 03b3d8539..20e1625fa 100644
--- a/contrib/visupng/VisualPng.c
+++ b/contrib/visupng/VisualPng.c
@@ -2,7 +2,7 @@
  *  VisualPng.C -- Shows a PNG image
  *------------------------------------
  *
- * Copyright 2000, Willem van Schaik.
+ * Copyright 2000,2017 Willem van Schaik.
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer