[PATCH] wifi: mt76: mt7996: Fix possible NULL pointer dereference in mt7996_mac_write_txwi_80211()

[Lorenzo Bianconi]

For injected frames (e.g. via radiotap), mac80211 can pass
info->control.vif = NULL, as explicitly noted in struct ieee80211_tx_info.
Check vif pointer before executing ieee80211_vif_is_mld() in
mt7996_mac_write_txwi_80211 routine in order to avoid a possible NULL
pointer dereference.

Fixes: f0b0b239b8f36 ("wifi: mt76: mt7996: rework mt7996_mac_write_txwi() for MLO support")
Signed-off-by: Lorenzo Bianconi <lorenzo at kernel.org>
---
 drivers/net/wireless/mediatek/mt76/mt7996/mac.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/mt7996/mac.c b/drivers/net/wireless/mediatek/mt76/mt7996/mac.c
index c98446057282..5ed2c73d5c75 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7996/mac.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7996/mac.c
@@ -757,6 +757,7 @@ mt7996_mac_write_txwi_80211(struct mt7996_dev *dev, __le32 *txwi,
 	bool multicast = is_multicast_ether_addr(hdr->addr1);
 	u8 tid = skb->priority & IEEE80211_QOS_CTL_TID_MASK;
 	__le16 fc = hdr->frame_control, sc = hdr->seq_ctrl;
+	struct ieee80211_vif *vif = info->control.vif;
 	u16 seqno = le16_to_cpu(sc);
 	bool hw_bigtk = false;
 	u8 fc_type, fc_stype;
@@ -819,7 +820,7 @@ mt7996_mac_write_txwi_80211(struct mt7996_dev *dev, __le32 *txwi,
 		txwi[3] |= cpu_to_le32(MT_TXD3_REM_TX_COUNT);
 	}
 
-	if (multicast && ieee80211_vif_is_mld(info->control.vif)) {
+	if (multicast && vif && ieee80211_vif_is_mld(vif)) {
 		val = MT_TXD3_SN_VALID |
 		      FIELD_PREP(MT_TXD3_SEQ, IEEE80211_SEQ_TO_SN(seqno));
 		txwi[3] |= cpu_to_le32(val);
@@ -839,12 +840,12 @@ mt7996_mac_write_txwi_80211(struct mt7996_dev *dev, __le32 *txwi,
 		txwi[3] &= ~cpu_to_le32(MT_TXD3_HW_AMSDU);
 	}
 
-	if (ieee80211_vif_is_mld(info->control.vif) &&
+	if (vif && ieee80211_vif_is_mld(vif) &&
 	    (multicast || unlikely(skb->protocol == cpu_to_be16(ETH_P_PAE))))
 		txwi[5] |= cpu_to_le32(MT_TXD5_FL);
 
 	if (ieee80211_is_nullfunc(fc) && ieee80211_has_a4(fc) &&
-	    ieee80211_vif_is_mld(info->control.vif)) {
+	    vif && ieee80211_vif_is_mld(vif)) {
 		txwi[5] |= cpu_to_le32(MT_TXD5_FL);
 		txwi[6] |= cpu_to_le32(MT_TXD6_DIS_MAT);
 	}

---
base-commit: 4913f44167cf35a9536e9eec7352e15b2de0c573
change-id: 20260531-mt7996_mac_write_txwi_80211-null-ptr-deref-8ce8d08cf53a

Best regards,
-- 
Lorenzo Bianconi <lorenzo at kernel.org>