[PATCH 6.6.y] wifi: mt76: mt7996: unlink TWT flow if the MCU rejects the agreement

[Sasha Levin <sashal@kernel.org>]

From: Zhao Li <enderaoelyther@gmail.com>

[ Upstream commit 022f5f8b7a0580da50fcbc34da853d03d4321fe2 ]

mt7996_mac_add_twt_setup() links a new flow into dev->twt_list before
asking the MCU to add the agreement, but exits without unlinking the flow
if the request fails. The flow-ID and table masks are only committed
after MCU success, so the still-linked flow is invisible to the
mask-gated teardown paths.

If the station retries the setup, the same slot is cleared and its
embedded list node reinitialized while it is still linked, corrupting
dev->twt_list. If the station disassociates instead, teardown skips the
flow and station storage can be freed while the node remains linked. A
later scheduling or debugfs twt_stats walk can then dereference the
freed flow, resulting in a use-after-free.

Unlink the flow when the MCU rejects the agreement. This restores the
list to its pre-request state while leaving the unchanged mask and
agreement accounting untouched.

Fixes: 98686cd21624 ("wifi: mt76: mt7996: add driver for MediaTek Wi-Fi 7 (802.11be) devices")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20260729173632.14387-3-enderaoelyther@gmail.com/
Assisted-by: Codex:gpt-5.6-sol
Assisted-by: Kimi:K3
Signed-off-by: Zhao Li <enderaoelyther@gmail.com>
Link: https://patch.msgid.link/20260825112620.97568-1-enderaoelyther@gmail.com
Signed-off-by: Felix Fietkau <nbd@nbd.name>
[ sashal: Adapted mt7996_mcu_twt_agrt_update() to pass msta->vif instead of &msta->vif->deflink. ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/wireless/mediatek/mt76/mt7996/mac.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/mediatek/mt76/mt7996/mac.c b/drivers/net/wireless/mediatek/mt76/mt7996/mac.c
index 14c84219ef750..42e75e7416ed4 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7996/mac.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7996/mac.c
@@ -2551,8 +2551,10 @@ void mt7996_mac_add_twt_setup(struct ieee80211_hw *hw,
 	}
 	flow->tsf = le64_to_cpu(twt_agrt->twt);
 
-	if (mt7996_mcu_twt_agrt_update(dev, msta->vif, flow, MCU_TWT_AGRT_ADD))
+	if (mt7996_mcu_twt_agrt_update(dev, msta->vif, flow, MCU_TWT_AGRT_ADD)) {
+		list_del(&flow->list);
 		goto unlock;
+	}
 
 	setup_cmd = TWT_SETUP_CMD_ACCEPT;
 	dev->twt.table_mask |= BIT(table_id);
-- 
2.53.0