mac80211: don't check rates on PLCP error frames

Frames that failed PLCP error checks are most likely
microwave transmissions (well, maybe not ...) and
don't have a proper rate detected, so ignore it.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/rx.c

@@ -2615,14 +2615,22 @@ void ieee80211_rx(struct ieee80211_hw *hw, struct sk_buff *skb)
 	if (WARN_ON(!local->started))
 		goto drop;
 
+	if (likely(!(status->flag & RX_FLAG_FAILED_PLCP_CRC))) {
+		/*
+		 * Validate the rate, unless a PLCP error means that
+		 * we probably can't have a valid rate here anyway.
+		 */
+
 		if (status->flag & RX_FLAG_HT) {
 			/*
-		 * rate_idx is MCS index, which can be [0-76] as documented on:
+			 * rate_idx is MCS index, which can be [0-76]
+			 * as documented on:
 			 *
 			 * http://wireless.kernel.org/en/developers/Documentation/ieee80211/802.11n
 			 *
-		 * Anything else would be some sort of driver or hardware error.
-		 * The driver should catch hardware errors.
+			 * Anything else would be some sort of driver or
+			 * hardware error. The driver should catch hardware
+			 * errors.
 			 */
 			if (WARN((status->rate_idx < 0 ||
 				 status->rate_idx > 76),
@@ -2638,6 +2646,7 @@ void ieee80211_rx(struct ieee80211_hw *hw, struct sk_buff *skb)
 				goto drop;
 			rate = &sband->bitrates[status->rate_idx];
 		}
+	}
 
 	/*
 	 * key references and virtual interfaces are protected using RCU