png_inflate_claim(png_structrp png_ptr, png_uint_32 owner)
{
   if (png_ptr->zowner != 0)
   {
      char msg[64];

      PNG_STRING_FROM_CHUNK(msg, png_ptr->zowner);
      /* So the message that results is "<chunk> using zstream"; this is an
       * internal error, but is very useful for debugging.  i18n requirements
       * are minimal.
       */
      (void)png_safecat(msg, (sizeof msg), 4, " using zstream");
#if PNG_RELEASE_BUILD
      png_chunk_warning(png_ptr, msg);
      png_ptr->zowner = 0;
#else
      png_chunk_error(png_ptr, msg);
#endif
   }

   /* Implementation note: unlike 'png_deflate_claim' this internal function
    * does not take the size of the data as an argument.  Some efficiency could
    * be gained by using this when it is known *if* the zlib stream itself does
    * not record the number; however, this is an illusion: the original writer
    * of the PNG may have selected a lower window size, and we really must
    * follow that because, for systems with with limited capabilities, we
    * would otherwise reject the application's attempts to use a smaller window
    * size (zlib doesn't have an interface to say "this or lower"!).
    *
    * inflateReset2 was added to zlib 1.2.4; before this the window could not be
    * reset, therefore it is necessary to always allocate the maximum window
    * size with earlier zlibs just in case later compressed chunks need it.
    */
   {
      int ret; /* zlib return code */
#if ZLIB_VERNUM >= 0x1240
      int window_bits = 0;

# if defined(PNG_SET_OPTION_SUPPORTED) && defined(PNG_MAXIMUM_INFLATE_WINDOW)
      if (((png_ptr->options >> PNG_MAXIMUM_INFLATE_WINDOW) & 3) ==
          PNG_OPTION_ON)
      {
         window_bits = 15;
         png_ptr->zstream_start = 0; /* fixed window size */
      }

      else
      {
         png_ptr->zstream_start = 1;
      }
# endif

#endif /* ZLIB_VERNUM >= 0x1240 */

      /* Set this for safety, just in case the previous owner left pointers to
       * memory allocations.
       */
      png_ptr->zstream.next_in = NULL;
      png_ptr->zstream.avail_in = 0;
      png_ptr->zstream.next_out = NULL;
      png_ptr->zstream.avail_out = 0;

      if ((png_ptr->flags & PNG_FLAG_ZSTREAM_INITIALIZED) != 0)
      {
#if ZLIB_VERNUM >= 0x1240
         ret = inflateReset2(&png_ptr->zstream, window_bits);
#else
         ret = inflateReset(&png_ptr->zstream);
#endif
      }

      else
      {
#if ZLIB_VERNUM >= 0x1240
         ret = inflateInit2(&png_ptr->zstream, window_bits);
#else
         ret = inflateInit(&png_ptr->zstream);
#endif

         if (ret == Z_OK)
            png_ptr->flags |= PNG_FLAG_ZSTREAM_INITIALIZED;
      }

#if ZLIB_VERNUM >= 0x1290 && \
   defined(PNG_SET_OPTION_SUPPORTED) && defined(PNG_IGNORE_ADLER32)
      if (((png_ptr->options >> PNG_IGNORE_ADLER32) & 3) == PNG_OPTION_ON)
         /* Turn off validation of the ADLER32 checksum in IDAT chunks */
         ret = inflateValidate(&png_ptr->zstream, 0);
#endif

      if (ret == Z_OK)
         png_ptr->zowner = owner;

      else
         png_zstream_error(png_ptr, ret);

      return ret;
   }

#ifdef window_bits
# undef window_bits
#endif
}

The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.