skip_sfx(struct archive_read *a)
{
  const void *h;
  const char *p, *q;
  size_t skip, total;
  ssize_t bytes, window;

  total = 0;
  window = 4096;
  while (total + window <= (1024 * 128)) {
    h = __archive_read_ahead(a, window, &bytes);
    if (h == NULL) {
      /* Remaining bytes are less than window. */
      window >>= 1;
      if (window < 0x40)
      	goto fatal;
      continue;
    }
    if (bytes < 0x40)
      goto fatal;
    p = h;
    q = p + bytes;

    /*
     * Scan ahead until we find something that looks
     * like the RAR header.
     */
    while (p + 7 < q) {
      if (memcmp(p, RAR_SIGNATURE, 7) == 0) {
      	skip = p - (const char *)h;
      	__archive_read_consume(a, skip);
      	return (ARCHIVE_OK);
      }
      p += 0x10;
    }
    skip = p - (const char *)h;
    __archive_read_consume(a, skip);
	total += skip;
  }
fatal:
  archive_set_error(&a->archive, ARCHIVE_ERRNO_FILE_FORMAT,
      "Couldn't find out RAR header");
  return (ARCHIVE_FATAL);
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.