wifi: mac80211: fix potential sta-link leak

When a station is allocated, links are added but not
set to valid yet (e.g. during connection to an AP MLD),
we might remove the station without ever marking links
valid, and leak them. Fix that.

Fixes: cb71f1d1 ("wifi: mac80211: add sta link addition/removal")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Reviewed-by: Ilan Peer <ilan.peer@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://msgid.link/20240111181514.6573998beaf8.I09ac2e1d41c80f82a5a616b8bd1d9d8dd709a6a6@changeidSigned-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/sta_info.c

@@ -404,7 +404,10 @@ void sta_info_free(struct ieee80211_local *local, struct sta_info *sta)
 	int i;
 
 	for (i = 0; i < ARRAY_SIZE(sta->link); i++) {
-		if (!(sta->sta.valid_links & BIT(i)))
+		struct link_sta_info *link_sta;
+
+		link_sta = rcu_access_pointer(sta->link[i]);
+		if (!link_sta)
 			continue;
 
 		sta_remove_link(sta, i, false);