mac80211: check if key has TKIP type before updating IV

commit 4045f72bcf3c293c7c5932ef001742d8bb5ded76 upstream.

This patch fix corruption which can manifest itself by following crash
when switching on rfkill switch with rt2x00 driver:
https://bugzilla.redhat.com/attachment.cgi?id=615362

Pointer key->u.ccmp.tfm of group key get corrupted in:

ieee80211_rx_h_michael_mic_verify():

        /* update IV in key information to be able to detect replays */
        rx->key->u.tkip.rx[rx->security_idx].iv32 = rx->tkip_iv32;
        rx->key->u.tkip.rx[rx->security_idx].iv16 = rx->tkip_iv16;

because rt2x00 always set RX_FLAG_MMIC_STRIPPED, even if key is not TKIP.

We already check type of the key in different path in
ieee80211_rx_h_michael_mic_verify() function, so adding additional
check here is reasonable.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>