mysterious -1 offset in staging rt2860 driver

[Dan Carpenter]

So here is a mystery for people who enjoy such mysterious things.

drivers/staging/rt2860/sta_ioctl.c +1020 rt_ioctl_giwscan(219)
  1011                  if (CAP_IS_PRIVACY_ON
  1012                      (pAdapter->ScanTab.BssEntry[i].CapabilityInfo))
  1013                          iwe.u.data.flags = IW_ENCODE_ENABLED | IW_ENCODE_NOKEY;
  1014                  else
  1015                          iwe.u.data.flags = IW_ENCODE_DISABLED;
  1016
  1017                  __smatch_value("iwe.u.data.flags");
  1018                  previous_ev = current_ev;
  1019                  current_ev =
  1020                      iwe_stream_add_point(info, current_ev, end_buf, &iwe,
  1021                                           (char *)pAdapter->
  1022                                           SharedKey[BSS0][(iwe.u.data.
  1023                                                            flags &
  1024                                                            IW_ENCODE_INDEX) -
  1025                                                           1].Key);


That last bit is easier to read if it's on one line.

SharedKey[BSS0][(iwe.u.data.flags & IW_ENCODE_INDEX) - 1].Key);

iwe.u.data.flags is either 0x0400 or 0x8000.  IW_ENCODE_INDEX is 0xff, so
after we mask off the lower bits we get 0x00 and then we subtract 1 we get
an array offset of -1.

I doubt that's what we want, but what _do_ we want here?

regards,
dan carpenter