From fcfe1b5e162bf473c1d47760962cec8523c00466 Mon Sep 17 00:00:00 2001
From: Felix Fietkau <nbd@nbd.name>
Date: Sat, 23 Apr 2022 07:01:18 +0200
Subject: [PATCH] mt76: fix tx status related use-after-free race on station removal
Git-commit: fcfe1b5e162bf473c1d47760962cec8523c00466
Patch-mainline: v5.19-rc1
References: bsc#1209980
There is a small race window where ongoing tx activity can lead to a skb
getting added to the status tracking idr after that idr has already been
cleaned up, which will keep the wcid linked in the status poll list.
Fix this by only adding status skbs if the wcid pointer is still assigned
in dev->wcid, which gets cleared early by mt76_sta_pre_rcu_remove
Fixes: bd1e3e7b693c ("mt76: introduce packet_id idr")
Tested-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/net/wireless/mediatek/mt76/mac80211.c | 2 ++
drivers/net/wireless/mediatek/mt76/tx.c | 2 +-
2 files changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/net/wireless/mediatek/mt76/mac80211.c b/drivers/net/wireless/mediatek/mt76/mac80211.c
index 2dd3ebd1863f..8a2fedbb1451 100644
--- a/drivers/net/wireless/mediatek/mt76/mac80211.c
+++ b/drivers/net/wireless/mediatek/mt76/mac80211.c
@@ -1381,7 +1381,9 @@ void mt76_sta_pre_rcu_remove(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
struct mt76_wcid *wcid = (struct mt76_wcid *)sta->drv_priv;
mutex_lock(&dev->mutex);
+ spin_lock_bh(&dev->status_lock);
rcu_assign_pointer(dev->wcid[wcid->idx], NULL);
+ spin_unlock_bh(&dev->status_lock);
mutex_unlock(&dev->mutex);
}
EXPORT_SYMBOL_GPL(mt76_sta_pre_rcu_remove);
diff --git a/drivers/net/wireless/mediatek/mt76/tx.c b/drivers/net/wireless/mediatek/mt76/tx.c
index c3be62f58b62..d5a8456c108b 100644
--- a/drivers/net/wireless/mediatek/mt76/tx.c
+++ b/drivers/net/wireless/mediatek/mt76/tx.c
@@ -120,7 +120,7 @@ mt76_tx_status_skb_add(struct mt76_dev *dev, struct mt76_wcid *wcid,
memset(cb, 0, sizeof(*cb));
- if (!wcid)
+ if (!wcid || !rcu_access_pointer(dev->wcid[wcid->idx]))
return MT_PACKET_ID_NO_ACK;
if (info->flags & IEEE80211_TX_CTL_NO_ACK)
--
2.35.3