[libpng12] Avoid out-of-bounds memory access while checking version string in

pngread.c and pngwrite.c

1 files changed, 15 insertions, 6 deletions

diff --git a/pngwrite.c b/pngwrite.c
index 1d94404db..c5cd9ec8f 100644
--- a/pngwrite.c
+++ b/pngwrite.c
@@ -525,15 +525,23 @@ png_create_write_struct_2(png_const_charp user_png_ver, png_voidp error_ptr,
 #endif /* PNG_USER_MEM_SUPPORTED */
    png_set_error_fn(png_ptr, error_ptr, error_fn, warn_fn);
 
-   if (user_png_ver)
+   if (user_png_ver != NULL)
    {
-      i = 0;
+      int found_dots = 0;
+      i = -1;
+
       do
       {
-         if (user_png_ver[i] != png_libpng_ver[i])
+         i++;
+         if (user_png_ver[i] != PNG_LIBPNG_VER_STRING[i])
             png_ptr->flags |= PNG_FLAG_LIBRARY_MISMATCH;
-      } while (png_libpng_ver[i++]);
+         if (user_png_ver[i] == '.')
+            found_dots++;
+      } while (found_dots < 2 && user_png_ver[i] != 0 &&
+            PNG_LIBPNG_VER_STRING[i] != 0);
    }
+   else
+      png_ptr->flags |= PNG_FLAG_LIBRARY_MISMATCH;
 
    if (png_ptr->flags & PNG_FLAG_LIBRARY_MISMATCH)
    {
@@ -684,8 +692,9 @@ png_write_init_3(png_structpp ptr_ptr, png_const_charp user_png_ver,
          png_warning(png_ptr,
  "Application uses deprecated png_write_init() and should be recompiled.");
 #endif
-      }
-   } while (png_libpng_ver[i++]);
+   }
+      i++;
+   } while (png_libpng_ver[i] != 0 && user_png_ver[i] != 0);
 
    png_debug(1, "in png_write_init_3");