[PATCH 3/3] wifi: cfg80211: check if AP has been started before adding new station

[Slawomir Stepien]

Adding a new station to AP makes only sense when the AP has been started
beforehand (nl80211_start_ap()). Check if AP is up and beaconing on the
link when adding new station. Return error if this isn't the case.

Reported-by: syzbot+9bdc0c5998ab45b05030@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=9bdc0c5998ab45b05030
Signed-off-by: Slawomir Stepien <sst@xxxxxxxxx>
---
 net/wireless/nl80211.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index ebde52655904..75bbd78f91ba 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -9174,7 +9174,7 @@ static int nl80211_set_station(struct sk_buff *skb, struct genl_info *info)
 static int nl80211_new_station(struct sk_buff *skb, struct genl_info *info)
 {
 	struct cfg80211_registered_device *rdev = info->user_ptr[0];
-	int err;
+	int err, link_id;
 	struct wireless_dev *wdev = info->user_ptr[1];
 	struct net_device *dev = wdev->netdev;
 	struct station_parameters params;
@@ -9413,6 +9413,11 @@ static int nl80211_new_station(struct sk_buff *skb, struct genl_info *info)
 	switch (wdev->iftype) {
 	case NL80211_IFTYPE_AP:
 	case NL80211_IFTYPE_P2P_GO:
+		/* Add a new station only after the AP and link has been started */
+		link_id = wdev->valid_links ? params.link_sta_params.link_id : 0;
+		if (!wdev->links[link_id].ap.beacon_interval)
+			return -ENETDOWN;
+
 		/* ignore WME attributes if iface/sta is not capable */
 		if (!(rdev->wiphy.flags & WIPHY_FLAG_AP_UAPSD) ||
 		    !(params.sta_flags_set & BIT(NL80211_STA_FLAG_WME)))
-- 
2.55.0