[PATCH mt76-next 04/29] wifi: mt76: mt7915: unwind state on add_interface failure

[Felix Fietkau <nbd@nbd.name>]

When mt76_wcid_alloc() fails, mt7915_add_interface() returned without
clearing the vif_mask/omac_mask bits it had already set, without removing
the firmware dev info added earlier, and without clearing a monitor_vif
pointer to the vif mac80211 is about to free. mac80211 does not call
remove_interface() for a failed add, so the indices and firmware dev
entry leaked permanently and testmode could dereference the stale
monitor_vif. Add a proper error unwind.

Fixes: b619e01380ee ("mt76: fix MBSS index condition in DBDC mode")
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 drivers/net/wireless/mediatek/mt76/mt7915/main.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/mediatek/mt76/mt7915/main.c b/drivers/net/wireless/mediatek/mt76/mt7915/main.c
index 4ed3d808654f..d2130226de64 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7915/main.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7915/main.c
@@ -249,7 +249,7 @@ static int mt7915_add_interface(struct ieee80211_hw *hw,
 	idx = mt76_wcid_alloc(dev->mt76.wcid_mask, mt7915_wtbl_size(dev));
 	if (idx < 0) {
 		ret = -ENOSPC;
-		goto out;
+		goto err;
 	}
 
 	INIT_LIST_HEAD(&mvif->sta.rc_list);
@@ -277,7 +277,17 @@ static int mt7915_add_interface(struct ieee80211_hw *hw,
 	mt7915_mcu_add_sta(dev, vif, NULL, CONN_STATE_PORT_SECURE, true);
 	rcu_assign_pointer(dev->mt76.wcid[idx], &mvif->sta.wcid);
 
+	mutex_unlock(&dev->mt76.mutex);
+
+	return 0;
+
+err:
+	dev->mt76.vif_mask &= ~BIT_ULL(mvif->mt76.idx);
+	phy->omac_mask &= ~BIT_ULL(mvif->mt76.omac_idx);
+	mt7915_mcu_add_dev_info(phy, vif, false);
 out:
+	if (phy->monitor_vif == vif)
+		phy->monitor_vif = NULL;
 	mutex_unlock(&dev->mt76.mutex);
 
 	return ret;
-- 
2.53.0