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Thu, 15 Jan 2026 17:05:37 -0800 (PST) Sender: Zac Bowling From: Zac To: sean.wang@kernel.org Cc: deren.wu@mediatek.com, kvalo@kernel.org, linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org, linux-wireless@vger.kernel.org, lorenzo@kernel.org, nbd@nbd.name, linux@frame.work, ryder.lee@mediatek.com, sean.wang@mediatek.com, Zac Bowling , Zac Bowling Subject: [PATCH v4 10/21] wifi: mt76: mt792x: fix NULL pointer dereference in TX path Date: Thu, 15 Jan 2026 17:05:08 -0800 Message-ID: <20260116010519.37001-11-zac@zacbowling.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260116010519.37001-1-zac@zacbowling.com> References: <20260116010519.37001-1-zac@zacbowling.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Zac Bowling Add NULL pointer checks in mt792x_tx() to prevent kernel crashes when transmitting packets during MLO link removal. The function calls mt792x_sta_to_link() which can return NULL if the link is being removed, but the return value was dereferenced without checking. Similarly, the RCU-protected link_conf and link_sta pointers were used without NULL validation. This race can occur when: 1. A packet is queued for transmission 2. Concurrently, the link is being removed (mt7925_mac_link_sta_remove) 3. mt792x_sta_to_link() returns NULL for the removed link 4. Kernel crashes on wcid =3D &mlink->wcid dereference Example crash trace: BUG: kernel NULL pointer dereference RIP: mt792x_tx+0x... Call Trace: ieee80211_tx+0x... __ieee80211_subif_start_xmit+0x... Fix by: - Check mlink return value before dereferencing wcid - Check RCU-dereferenced conf and link_sta before use - Free the SKB and return early if any pointer is NULL This affects both MT7921 and MT7925 drivers as mt792x_core.c is shared. Fixes: c74df1c067f2 ("wifi: mt76: mt792x: introduce mt792x-lib module") Reported-by: Zac Bowling Signed-off-by: Zac Bowling --- drivers/net/wireless/mediatek/mt76/mt792x_core.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/drivers/net/wireless/mediatek/mt76/mt792x_core.c b/drivers/net= /wireless/mediatek/mt76/mt792x_core.c index f2ed16feb6..9dc768aa8b 100644 --- a/drivers/net/wireless/mediatek/mt76/mt792x_core.c +++ b/drivers/net/wireless/mediatek/mt76/mt792x_core.c @@ -95,6 +95,8 @@ void mt792x_tx(struct ieee80211_hw *hw, struct ieee80211_= tx_control *control, IEEE80211_TX_CTRL_MLO_LINK); sta =3D (struct mt792x_sta *)control->sta->drv_priv; mlink =3D mt792x_sta_to_link(sta, link_id); + if (!mlink) + goto free_skb; wcid =3D &mlink->wcid; } =20 @@ -113,9 +115,12 @@ void mt792x_tx(struct ieee80211_hw *hw, struct ieee802= 11_tx_control *control, link_id =3D wcid->link_id; rcu_read_lock(); conf =3D rcu_dereference(vif->link_conf[link_id]); - memcpy(hdr->addr2, conf->addr, ETH_ALEN); - link_sta =3D rcu_dereference(control->sta->link[link_id]); + if (!conf || !link_sta) { + rcu_read_unlock(); + goto free_skb; + } + memcpy(hdr->addr2, conf->addr, ETH_ALEN); memcpy(hdr->addr1, link_sta->addr, ETH_ALEN); =20 if (vif->type =3D=3D NL80211_IFTYPE_STATION) @@ -136,6 +141,10 @@ void mt792x_tx(struct ieee80211_hw *hw, struct ieee802= 11_tx_control *control, } =20 mt76_connac_pm_queue_skb(hw, &dev->pm, wcid, skb); + return; + +free_skb: + ieee80211_free_txskb(hw, skb); } EXPORT_SYMBOL_GPL(mt792x_tx); =20 --=20 2.52.0