mac80211: remove STA entries when taking down interface

When we take down an interface, we need to remove the STA info
items that belong to it because otherwise we might invoke a
sta_notify() callback in the driver when we later delete the
STA entries, but in that case the driver will already have
removed its knowledge of the interface they belonged to leading
to confusion. Also, we could invoke the set_tim() callback after
the driver removed its knowledge of the interface, which can
lead to a crash if it requests a beacon with a then-invalid vif
pointer!

A side effect of this patch is that, because it was easier, it
disallows changing the WDS peer while an interface is up. Should
that actually be necessary, it can be added back, but the WDS
peer STA entry may not be added while the interface is UP so for
now I've simplified the WDS peer's STA entry lifetime management.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 12 insertions, 2 deletions

diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index a230a9597398..a767042ec4fd 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -258,6 +258,8 @@ int sta_info_insert(struct sta_info *sta)
 	unsigned long flags;
 	DECLARE_MAC_BUF(mac);
 
+	WARN_ON(!netif_running(sdata->dev));
+
 	spin_lock_irqsave(&local->sta_lock, flags);
 	/* check if STA exists already */
 	if (__sta_info_find(local, sta->addr)) {
@@ -608,14 +610,18 @@ void sta_info_stop(struct ieee80211_local *local)
 
 /**
  * sta_info_flush - flush matching STA entries from the STA table
+ *
+ * Returns the number of removed STA entries.
+ *
  * @local: local interface data
  * @sdata: matching rule for the net device (sta->dev) or %NULL to match all STAs
  */
-void sta_info_flush(struct ieee80211_local *local,
+int sta_info_flush(struct ieee80211_local *local,
 		    struct ieee80211_sub_if_data *sdata)
 {
 	struct sta_info *sta, *tmp;
 	LIST_HEAD(tmp_list);
+	int ret = 0;
 	unsigned long flags;
 
 	might_sleep();
@@ -624,8 +630,10 @@ void sta_info_flush(struct ieee80211_local *local,
 	list_for_each_entry_safe(sta, tmp, &local->sta_list, list) {
 		if (!sdata || sdata == sta->sdata) {
 			__sta_info_unlink(&sta);
-			if (sta)
+			if (sta) {
 				list_add_tail(&sta->list, &tmp_list);
+				ret++;
+			}
 		}
 	}
 	spin_unlock_irqrestore(&local->sta_lock, flags);
@@ -634,4 +642,6 @@ void sta_info_flush(struct ieee80211_local *local,
 
 	list_for_each_entry_safe(sta, tmp, &tmp_list, list)
 		sta_info_destroy(sta);
+
+	return ret;
 }