mac80211: fix action frame length checks

The action frame length checks are one too small, there's not just
an action code as the comment makes you believe, there's a category
code too, and the category code is required in each action frame
(hence part of IEEE80211_MIN_ACTION_SIZE).

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/mesh_plink.c b/net/mac80211/mesh_plink.c
index 7714b0e..74983cf 100644
--- a/net/mac80211/mesh_plink.c
+++ b/net/mac80211/mesh_plink.c
@@ -421,6 +421,10 @@
 	DECLARE_MAC_BUF(mac);
 #endif
 
+	/* need action_code, aux */
+	if (len < IEEE80211_MIN_ACTION_SIZE + 3)
+		return;
+
 	if (is_multicast_ether_addr(mgmt->da)) {
 		mpl_dbg("Mesh plink: ignore frame from multicast address");
 		return;