mac80211: check power constraint IE size when parsing

The power constraint IE is always a single byte
so check the size when parsing instead of later.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 471fb05..ed75439 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -792,8 +792,11 @@
 			elems->country_elem_len = elen;
 			break;
 		case WLAN_EID_PWR_CONSTRAINT:
+			if (elen != 1) {
+				elem_parse_failed = true;
+				break;
+			}
 			elems->pwr_constr_elem = pos;
-			elems->pwr_constr_elem_len = elen;
 			break;
 		case WLAN_EID_TIMEOUT_INTERVAL:
 			elems->timeout_int = pos;