[PATCH 18/19] wifi: mt76: mt7925: publish msta->link after successful link add

[Sean Wang <sean.wang@kernel.org>]

From: Sean Wang <sean.wang@mediatek.com>

Move the msta->link[link_id] publication until after
mt7925_mac_link_sta_add() succeeds.

msta->link[] is RCU-visible, so publishing it before setup completes can
expose a link whose add path later fails. Publish it only after success
to avoid partially initialized link state becoming visible.

Signed-off-by: Sean Wang <sean.wang@mediatek.com>
---
 .../net/wireless/mediatek/mt76/mt7925/main.c   | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/mt7925/main.c b/drivers/net/wireless/mediatek/mt76/mt7925/main.c
index eb16c4683100..95c631b57894 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7925/main.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7925/main.c
@@ -1000,10 +1000,11 @@ mt7925_mac_sta_add_links(struct mt792x_dev *dev, struct ieee80211_vif *vif,
 	for_each_set_bit(link_id, &new_links, IEEE80211_MLD_MAX_NUM_LINKS) {
 		struct ieee80211_link_sta *link_sta;
 		struct mt792x_link_sta *mlink;
+		bool is_deflink = false;
 
 		if (msta->deflink_id == IEEE80211_LINK_UNSPECIFIED) {
 			mlink = &msta->deflink;
-			msta->deflink_id = link_id;
+			is_deflink = true;
 		} else {
 			mlink = kzalloc(sizeof(*mlink), GFP_KERNEL);
 			if (!mlink) {
@@ -1012,14 +1013,23 @@ mt7925_mac_sta_add_links(struct mt792x_dev *dev, struct ieee80211_vif *vif,
 			}
 		}
 
-		msta->valid_links |= BIT(link_id);
-		rcu_assign_pointer(msta->link[link_id], mlink);
 		mlink->sta = msta;
 		mlink->pri_link = &sta->deflink;
 		mlink->wcid.def_wcid = &msta->deflink.wcid;
 
 		link_sta = mt792x_sta_to_link_sta(vif, sta, link_id);
-		mt7925_mac_link_sta_add(&dev->mt76, vif, link_sta, mlink);
+		err = mt7925_mac_link_sta_add(&dev->mt76, vif, link_sta, mlink);
+		if (err) {
+			if (!is_deflink)
+				kfree_rcu(mlink, rcu_head);
+			break;
+		}
+
+		if (is_deflink)
+			msta->deflink_id = link_id;
+
+		rcu_assign_pointer(msta->link[link_id], mlink);
+		msta->valid_links |= BIT(link_id);
 	}
 
 	return err;
-- 
2.43.0