cfg80211: scan: drop entry from hidden_list on overflow

If we overflow the maximum number of BSS entries and free the
new entry, drop it from any hidden_list that it may have been
added to in the code above or in cfg80211_combine_bsses().

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20210416094212.5de7d1676ad7.Ied283b0bc5f504845e7d6ab90626bdfa68bb3dc0@changeid
Cc: stable@vger.kernel.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/scan.c

@@ -1751,6 +1751,8 @@ cfg80211_bss_update(struct cfg80211_registered_device *rdev,
 
 		if (rdev->bss_entries >= bss_entries_limit &&
 		    !cfg80211_bss_expire_oldest(rdev)) {
+			if (!list_empty(&new->hidden_list))
+				list_del(&new->hidden_list);
 			kfree(new);
 			goto drop;
 		}