iwlwifi: prevent read outside array bounds

With EDCA and HCCA we have 16 potential tid values. This is accommodated by
mac80211, but iwlwifi only supports EDCA. With this implementation it is
thus possible for mac80211 to request a tid that will cause iwlwifi to read
outside array bounds. A similar problem exists if traffic is received in an
unsupported category.

We add error checking to catch these situations.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-agn-rs.c

@@ -332,6 +332,9 @@ static u8 rs_tl_add_packet(struct iwl_lq_sta *lq_data,
 	} else
 		return MAX_TID_COUNT;
 
+	if (unlikely(tid >= TID_MAX_LOAD_COUNT))
+		return MAX_TID_COUNT;
+
 	tl = &lq_data->load[tid];
 
 	curr_time -= curr_time % TID_ROUND_VALUE;