Harden a vestigial check against overflow inside png_zalloc

Reported-by: Sergio Atienza Pastor, MTP Métodos y Tecnología

ANNOUNCE

@@ -1,3 +1,11 @@
+libpng 1.6.51.git
+=================
+
+This is a development version, not intended to be a public release.
+It will be replaced by a public release, or by another development
+version, at a later time.
+
+
 libpng 1.6.50 - July 1, 2025
 ============================
 

CHANGES

@@ -6278,6 +6278,8 @@ Version 1.6.50 [July 1, 2025]
     (Contributed by John Bowler)
   Fixed the CMake file for cross-platform builds that require `libm`.
 
+Version 1.6.51 [TODO]
+
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net.
 Subscription is required; visit
 https://lists.sourceforge.net/lists/listinfo/png-mng-implement

CMakeLists.txt

@@ -18,9 +18,9 @@ cmake_minimum_required(VERSION 3.14...4.0)
 
 set(PNGLIB_MAJOR 1)
 set(PNGLIB_MINOR 6)
-set(PNGLIB_REVISION 50)
-set(PNGLIB_SUBREVISION 0)
-#set(PNGLIB_SUBREVISION "git")
+set(PNGLIB_REVISION 51)
+#set(PNGLIB_SUBREVISION 0)
+set(PNGLIB_SUBREVISION "git")
 set(PNGLIB_VERSION ${PNGLIB_MAJOR}.${PNGLIB_MINOR}.${PNGLIB_REVISION})
 set(PNGLIB_ABI_VERSION ${PNGLIB_MAJOR}${PNGLIB_MINOR})
 set(PNGLIB_SHARED_VERSION ${PNGLIB_ABI_VERSION}.${PNGLIB_REVISION}.${PNGLIB_SUBREVISION})

README

@@ -1,5 +1,5 @@
-README for libpng version 1.6.50
-================================
+README for libpng version 1.6.51.git
+====================================
 
 See the note about version numbers near the top of `png.h`.
 See `INSTALL` for instructions on how to install libpng.

configure

@@ -1,6 +1,6 @@
 #! /bin/sh
 # Guess values for system-dependent variables and create Makefiles.
-# Generated by GNU Autoconf 2.72 for libpng 1.6.50.
+# Generated by GNU Autoconf 2.72 for libpng 1.6.51.git.
 #
 # Report bugs to <png-mng-implement@lists.sourceforge.net>.
 #
@@ -614,8 +614,8 @@ MAKEFLAGS=
 # Identity of this package.
 PACKAGE_NAME='libpng'
 PACKAGE_TARNAME='libpng'
-PACKAGE_VERSION='1.6.50'
-PACKAGE_STRING='libpng 1.6.50'
+PACKAGE_VERSION='1.6.51.git'
+PACKAGE_STRING='libpng 1.6.51.git'
 PACKAGE_BUGREPORT='png-mng-implement@lists.sourceforge.net'
 PACKAGE_URL=''
 
@@ -1424,7 +1424,7 @@ if test "$ac_init_help" = "long"; then
   # Omit some internal or obsolete options to make the list less imposing.
   # This message is too long to be a string in the A/UX 3.1 sh.
   cat <<_ACEOF
-'configure' configures libpng 1.6.50 to adapt to many kinds of systems.
+'configure' configures libpng 1.6.51.git to adapt to many kinds of systems.
 
 Usage: $0 [OPTION]... [VAR=VALUE]...
 
@@ -1495,7 +1495,7 @@ fi
 
 if test -n "$ac_init_help"; then
   case $ac_init_help in
-     short | recursive ) echo "Configuration of libpng 1.6.50:";;
+     short | recursive ) echo "Configuration of libpng 1.6.51.git:";;
    esac
   cat <<\_ACEOF
 
@@ -1698,7 +1698,7 @@ fi
 test -n "$ac_init_help" && exit $ac_status
 if $ac_init_version; then
   cat <<\_ACEOF
-libpng configure 1.6.50
+libpng configure 1.6.51.git
 generated by GNU Autoconf 2.72
 
 Copyright (C) 2023 Free Software Foundation, Inc.
@@ -1961,7 +1961,7 @@ cat >config.log <<_ACEOF
 This file contains any messages produced by compilers while
 running configure, to aid debugging if configure makes a mistake.
 
-It was created by libpng $as_me 1.6.50, which was
+It was created by libpng $as_me 1.6.51.git, which was
 generated by GNU Autoconf 2.72.  Invocation command line was
 
   $ $0$ac_configure_args_raw
@@ -3446,7 +3446,7 @@ fi
 
 # Define the identity of the package.
  PACKAGE='libpng'
- VERSION='1.6.50'
+ VERSION='1.6.51.git'
 
 
 printf "%s\n" "#define PACKAGE \"$PACKAGE\"" >>confdefs.h
@@ -3665,10 +3665,10 @@ fi
 
 
 
-PNGLIB_VERSION=1.6.50
+PNGLIB_VERSION=1.6.51.git
 PNGLIB_MAJOR=1
 PNGLIB_MINOR=6
-PNGLIB_RELEASE=50
+PNGLIB_RELEASE=51
 
 
 
@@ -16410,7 +16410,7 @@ cat >>$CONFIG_STATUS <<\_ACEOF || ac_write_fail=1
 # report actual input values of CONFIG_FILES etc. instead of their
 # values after options handling.
 ac_log="
-This file was extended by libpng $as_me 1.6.50, which was
+This file was extended by libpng $as_me 1.6.51.git, which was
 generated by GNU Autoconf 2.72.  Invocation command line was
 
   CONFIG_FILES    = $CONFIG_FILES
@@ -16478,7 +16478,7 @@ ac_cs_config_escaped=`printf "%s\n" "$ac_cs_config" | sed "s/^ //; s/'/'\\\\\\\\
 cat >>$CONFIG_STATUS <<_ACEOF || ac_write_fail=1
 ac_cs_config='$ac_cs_config_escaped'
 ac_cs_version="\\
-libpng config.status 1.6.50
+libpng config.status 1.6.51.git
 configured by $0, generated by GNU Autoconf 2.72,
   with options \\"\$ac_cs_config\\"
 

configure.ac

@@ -25,7 +25,7 @@ AC_PREREQ([2.68])
 
 dnl Version number stuff here:
 
-AC_INIT([libpng],[1.6.50],[png-mng-implement@lists.sourceforge.net])
+AC_INIT([libpng],[1.6.51.git],[png-mng-implement@lists.sourceforge.net])
 AC_CONFIG_MACRO_DIR([scripts/autoconf])
 
 # libpng does not follow GNU file name conventions (hence 'foreign')
@@ -46,10 +46,10 @@ dnl automake, so the following is not necessary (and is not defined anyway):
 dnl AM_PREREQ([1.11.2])
 dnl stop configure from automagically running automake
 
-PNGLIB_VERSION=1.6.50
+PNGLIB_VERSION=1.6.51.git
 PNGLIB_MAJOR=1
 PNGLIB_MINOR=6
-PNGLIB_RELEASE=50
+PNGLIB_RELEASE=51
 
 dnl End of version number stuff
 

png.c

@@ -13,7 +13,7 @@
 #include "pngpriv.h"
 
 /* Generate a compiler error if there is an old png.h in the search path. */
-typedef png_libpng_version_1_6_50 Your_png_h_is_not_version_1_6_50;
+typedef png_libpng_version_1_6_51_git Your_png_h_is_not_version_1_6_51_git;
 
 /* Sanity check the chunks definitions - PNG_KNOWN_CHUNKS from pngpriv.h and the
  * corresponding macro definitions.  This causes a compile time failure if
@@ -108,7 +108,13 @@ png_zalloc,(voidpf png_ptr, uInt items, uInt size),PNG_ALLOCATED)
    if (png_ptr == NULL)
       return NULL;
 
-   if (items >= (~(png_alloc_size_t)0)/size)
+   /* This check against overflow is vestigial, dating back from
+    * the old times when png_zalloc used to be an exported function.
+    * We're still keeping it here for now, as an extra-cautious
+    * prevention against programming errors inside zlib, although it
+    * should rather be a debug-time assertion instead.
+    */
+   if (size != 0 && items >= (~(png_alloc_size_t)0) / size)
    {
       png_warning(png_voidcast(png_structrp, png_ptr),
                   "Potential overflow in png_zalloc()");
@@ -815,7 +821,7 @@ png_get_copyright(png_const_structrp png_ptr)
    return PNG_STRING_COPYRIGHT
 #else
    return PNG_STRING_NEWLINE \
-      "libpng version 1.6.50" PNG_STRING_NEWLINE \
+      "libpng version 1.6.51.git" PNG_STRING_NEWLINE \
       "Copyright (c) 2018-2025 Cosmin Truta" PNG_STRING_NEWLINE \
       "Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson" \
       PNG_STRING_NEWLINE \

png.h

@@ -1,6 +1,6 @@
 /* png.h - header file for PNG reference library
  *
- * libpng version 1.6.50
+ * libpng version 1.6.51.git
  *
  * Copyright (c) 2018-2025 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
@@ -274,7 +274,7 @@
  */
 
 /* Version information for png.h - this should match the version in png.c */
-#define PNG_LIBPNG_VER_STRING "1.6.50"
+#define PNG_LIBPNG_VER_STRING "1.6.51.git"
 #define PNG_HEADER_VERSION_STRING " libpng version " PNG_LIBPNG_VER_STRING "\n"
 
 /* The versions of shared library builds should stay in sync, going forward */
@@ -285,12 +285,12 @@
 /* These should match the first 3 components of PNG_LIBPNG_VER_STRING: */
 #define PNG_LIBPNG_VER_MAJOR   1
 #define PNG_LIBPNG_VER_MINOR   6
-#define PNG_LIBPNG_VER_RELEASE 50
+#define PNG_LIBPNG_VER_RELEASE 51
 
 /* This should be zero for a public release, or non-zero for a
  * development version.
  */
-#define PNG_LIBPNG_VER_BUILD 0
+#define PNG_LIBPNG_VER_BUILD 1
 
 /* Release Status */
 #define PNG_LIBPNG_BUILD_ALPHA               1
@@ -307,7 +307,7 @@
 #define PNG_LIBPNG_BUILD_SPECIAL 32 /* Cannot be OR'ed with
                                        PNG_LIBPNG_BUILD_PRIVATE */
 
-#define PNG_LIBPNG_BUILD_BASE_TYPE PNG_LIBPNG_BUILD_STABLE
+#define PNG_LIBPNG_BUILD_BASE_TYPE PNG_LIBPNG_BUILD_BETA
 
 /* Careful here.  At one time, Guy wanted to use 082, but that
  * would be octal.  We must not include leading zeros.
@@ -316,7 +316,7 @@
  * From version 1.0.1 it is:
  * XXYYZZ, where XX=major, YY=minor, ZZ=release
  */
-#define PNG_LIBPNG_VER 10650 /* 1.6.50 */
+#define PNG_LIBPNG_VER 10651 /* 1.6.51.git */
 
 /* Library configuration: these options cannot be changed after
  * the library has been built.
@@ -426,7 +426,7 @@ extern "C" {
 /* This triggers a compiler error in png.c, if png.c and png.h
  * do not agree upon the version number.
  */
-typedef char* png_libpng_version_1_6_50;
+typedef char* png_libpng_version_1_6_51_git;
 
 /* Basic control structions.  Read libpng-manual.txt or libpng.3 for more info.
  *

pngconf.h

@@ -1,6 +1,6 @@
 /* pngconf.h - machine-configurable file for libpng
  *
- * libpng version 1.6.50
+ * libpng version 1.6.51.git
  *
  * Copyright (c) 2018-2025 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2016,2018 Glenn Randers-Pehrson

pngtest.c

@@ -50,7 +50,7 @@
 #define STDERR stdout
 
 /* Generate a compiler error if there is an old png.h in the search path. */
-typedef png_libpng_version_1_6_50 Your_png_h_is_not_version_1_6_50;
+typedef png_libpng_version_1_6_51_git Your_png_h_is_not_version_1_6_51_git;
 
 /* Ensure that all version numbers in png.h are consistent with one another. */
 #if (PNG_LIBPNG_VER != PNG_LIBPNG_VER_MAJOR * 10000 + \

scripts/libpng-config-head.in

@@ -11,7 +11,7 @@
 
 # Modeled after libxml-config.
 
-version=1.6.50
+version=1.6.51.git
 prefix=""
 libdir=""
 libs=""

scripts/libpng.pc.in

@@ -5,6 +5,6 @@ includedir=@includedir@/libpng16
 
 Name: libpng
 Description: Loads and saves PNG files
-Version: 1.6.50
+Version: 1.6.51.git
 Libs: -L${libdir} -lpng16
 Cflags: -I${includedir}

scripts/pnglibconf.h.prebuilt

@@ -1,6 +1,6 @@
 /* pnglibconf.h - library build configuration */
 
-/* libpng version 1.6.50 */
+/* libpng version 1.6.51.git */
 
 /* Copyright (c) 2018-2025 Cosmin Truta */
 /* Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson */