[PATCH v4 05/21] wifi: mt76: mt7925: add NULL checks for link_conf and mlink in main.c

[Zac <zac@zacbowling.com>]

From: Zac Bowling <zbowling@gmail.com>

Add NULL pointer checks throughout main.c for functions that call
mt792x_vif_to_bss_conf(), mt792x_vif_to_link(), and mt792x_sta_to_link()
without verifying the return value before dereferencing.

Functions fixed:
- mt7925_set_key(): Check link_conf, mconf, and mlink before use
- mt7925_mac_link_sta_add(): Check link_conf before BSS info update
- mt7925_mac_link_sta_assoc(): Check mlink and link_conf before use
- mt7925_mac_link_sta_remove(): Check mlink and link_conf, add goto
  label for proper cleanup path
- mt7925_change_vif_links(): Check link_conf before adding BSS

These functions can receive NULL when the link configuration in mac80211
is not yet synchronized with the driver's link tracking during MLO
operations or state transitions.

Without these checks, the driver crashes during station add/remove/
association operations with NULL pointer dereference:

  BUG: kernel NULL pointer dereference, address: 0000000000000010
  Call Trace:
   mt7925_mac_link_sta_add+0x...
   ...

Found through static analysis and triggered during BSSID roaming on
systems with multiple access points.

Reported-by: Zac Bowling <zac@zacbowling.com>
Fixes: c948b5da6bbe ("wifi: mt76: mt7925: add Mediatek Wi-Fi7 driver for mt7925 chips")
Signed-off-by: Zac Bowling <zac@zacbowling.com>
---
 .../net/wireless/mediatek/mt76/mt7925/main.c  | 27 ++++++++++++++++---
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/mt7925/main.c b/drivers/net/wireless/mediatek/mt76/mt7925/main.c
index 9f17b21aef..7d3322461b 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7925/main.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7925/main.c
@@ -604,6 +604,10 @@ static int mt7925_set_link_key(struct ieee80211_hw *hw, enum set_key_cmd cmd,
 	link_sta = sta ? mt792x_sta_to_link_sta(vif, sta, link_id) : NULL;
 	mconf = mt792x_vif_to_link(mvif, link_id);
 	mlink = mt792x_sta_to_link(msta, link_id);
+
+	if (!link_conf || !mconf || !mlink)
+		return -EINVAL;
+
 	wcid = &mlink->wcid;
 	wcid_keyidx = &wcid->hw_key_idx;
 
@@ -889,6 +893,8 @@ static int mt7925_mac_link_sta_add(struct mt76_dev *mdev,
 			       MT_WTBL_UPDATE_ADM_COUNT_CLEAR);
 
 	link_conf = mt792x_vif_to_bss_conf(vif, link_id);
+	if (!link_conf)
+		return -EINVAL;
 
 	/* should update bss info before STA add */
 	if (vif->type == NL80211_IFTYPE_STATION && !link_sta->sta->tdls) {
@@ -1034,6 +1040,8 @@ static void mt7925_mac_link_sta_assoc(struct mt76_dev *mdev,
 
 	msta = (struct mt792x_sta *)link_sta->sta->drv_priv;
 	mlink = mt792x_sta_to_link(msta, link_sta->link_id);
+	if (!mlink)
+		return;
 
 	mt792x_mutex_acquire(dev);
 
@@ -1043,12 +1051,13 @@ static void mt7925_mac_link_sta_assoc(struct mt76_dev *mdev,
 		link_conf = mt792x_vif_to_bss_conf(vif, vif->bss_conf.link_id);
 	}
 
-	if (vif->type == NL80211_IFTYPE_STATION && !link_sta->sta->tdls) {
+	if (link_conf && vif->type == NL80211_IFTYPE_STATION && !link_sta->sta->tdls) {
 		struct mt792x_bss_conf *mconf;
 
 		mconf = mt792x_link_conf_to_mconf(link_conf);
-		mt7925_mcu_add_bss_info(&dev->phy, mconf->mt76.ctx,
-					link_conf, link_sta, true);
+		if (mconf)
+			mt7925_mcu_add_bss_info(&dev->phy, mconf->mt76.ctx,
+						link_conf, link_sta, true);
 	}
 
 	ewma_avg_signal_init(&mlink->avg_ack_signal);
@@ -1095,6 +1104,8 @@ static void mt7925_mac_link_sta_remove(struct mt76_dev *mdev,
 
 	msta = (struct mt792x_sta *)link_sta->sta->drv_priv;
 	mlink = mt792x_sta_to_link(msta, link_id);
+	if (!mlink)
+		return;
 
 	mt7925_roc_abort_sync(dev);
 
@@ -1108,10 +1119,12 @@ static void mt7925_mac_link_sta_remove(struct mt76_dev *mdev,
 
 	link_conf = mt792x_vif_to_bss_conf(vif, link_id);
 
-	if (vif->type == NL80211_IFTYPE_STATION && !link_sta->sta->tdls) {
+	if (link_conf && vif->type == NL80211_IFTYPE_STATION && !link_sta->sta->tdls) {
 		struct mt792x_bss_conf *mconf;
 
 		mconf = mt792x_link_conf_to_mconf(link_conf);
+		if (!mconf)
+			goto out;
 
 		if (ieee80211_vif_is_mld(vif))
 			mt792x_mac_link_bss_remove(dev, mconf, mlink);
@@ -1119,6 +1132,7 @@ static void mt7925_mac_link_sta_remove(struct mt76_dev *mdev,
 			mt7925_mcu_add_bss_info(&dev->phy, mconf->mt76.ctx, link_conf,
 						link_sta, false);
 	}
+out:
 
 	spin_lock_bh(&mdev->sta_poll_lock);
 	if (!list_empty(&mlink->wcid.poll_list))
@@ -2031,6 +2045,11 @@ mt7925_change_vif_links(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
 		mlink = mlinks[link_id];
 		link_conf = mt792x_vif_to_bss_conf(vif, link_id);
 
+		if (!link_conf) {
+			err = -EINVAL;
+			goto free;
+		}
+
 		rcu_assign_pointer(mvif->link_conf[link_id], mconf);
 		rcu_assign_pointer(mvif->sta.link[link_id], mlink);
 
-- 
2.52.0