[PATCH wireless 2/2] wifi: mac80211: set the link addresses of a 4-address AP_VLAN before its links

[Piotr Kubik]

ieee80211_set_sta_4addr() gives the AP_VLAN of a 4-address MLD station
the links of that station. It added the links first and set
wdev->links[].addr afterwards, from the link_conf of the AP_VLAN
itself. ieee80211_link_init() takes the address of a new link from
wdev->links[].addr, so a link that the station gained later came up
with the zero address that an earlier call had set, and the copy from
its own link_conf kept it at zero. With two such links,
ieee80211_check_dup_link_addrs() refuses the change with -EALREADY,
and the station stays on the AP interface instead of its AP_VLAN.

Set the addresses from the link_conf of the AP before the links are
added, as the AP_VLAN link update in link.c does.

Fixes: 469d5d5a3b7a ("wifi: mac80211: synchronize valid links for WDS AP_VLAN interfaces")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Piotr Kubik <piotr@xxxxxxxx>
---
  net/mac80211/cfg.c |   17 ++++++++++-------
  1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -2823,26 +2823,29 @@ static int ieee80211_set_sta_4addr(struc
 
 		wdev->valid_links = new_links;
 
-		err = ieee80211_vif_set_links(sdata, new_links, 0);
-		if (err) {
-			wdev->valid_links = orig_links;
-			return err;
-		}
-
 		master_iter = master->vif.valid_links;
 
+		/* ieee80211_link_init() takes the address of a new link from
+		 * wdev->links, so set it before the links are added.
+		 */
 		for_each_set_bit(link_id, &master_iter,
 				 IEEE80211_MLD_MAX_NUM_LINKS) {
 			if (!(sta_links & BIT(link_id))) {
 				eth_zero_addr(wdev->links[link_id].addr);
 			} else {
 				link_conf = wiphy_dereference(wiphy,
-							      vif->link_conf[link_id]);
+							      master->vif.link_conf[link_id]);
 
 				ether_addr_copy(wdev->links[link_id].addr,
 						link_conf->bssid);
 			}
 		}
+
+		err = ieee80211_vif_set_links(sdata, new_links, 0);
+		if (err) {
+			wdev->valid_links = orig_links;
+			return err;
+		}
 	}
 
 	rcu_assign_pointer(sdata->u.vlan.sta, sta);