mac80211: fix handling of null-rate control in rate_control_get_rate

For hardware with IEEE80211_HW_HAS_RATE_CONTROL the rate controller is not
initialized. However, calling functions such as ieee80211_beacon_get result
in the rate_control_get_rate function getting called, which is accessing
(in this case uninitialized) rate control structures unconditionally.

Fix by exiting the function before setting the rates for HW with
IEEE80211_HW_HAS_RATE_CONTROL set. The initialization of the ieee80211_tx_info
struct is intentionally still executed.
Signed-off-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Reviewed-by: Kalle Valo <kalle.valo@nokia.com>
Cc: stable@kernel.org
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/rate.c

@@ -245,6 +245,9 @@ void rate_control_get_rate(struct ieee80211_sub_if_data *sdata,
 		info->control.rates[i].count = 1;
 	}
 
+	if (sdata->local->hw.flags & IEEE80211_HW_HAS_RATE_CONTROL)
+		return;
+
 	if (sta && sdata->force_unicast_rateidx > -1) {
 		info->control.rates[0].idx = sdata->force_unicast_rateidx;
 	} else {