[PATCH v6 1/1] wifi: mt76: mt792x: fix use-after-free in mt76_rx_poll_complete

[Eason Lai <eason.lai@mediatek.com>]

From: Eason Lai <Eason.Lai@mediatek.com>

A use-after-free issue occurs in mt76_rx_poll_complete due to a race
condition. The STA has already been removed, but the rx_status still
had a pointer to the wcid in the STA.

Set the links' wcid pointers to be NULL for a MLD in
mt7925_sta_pre_rcu_remove()

BUG: KASAN: invalid-access in mt76_rx_poll_complete+0x280/0x470
Call trace:
dump_backtrace+0xec/0x128
show_stack+0x18/0x28
dump_stack_lvl+0x40/0xc8
print_report+0x1b8/0x710
kasan_report+0xe0/0x144
do_bad_area+0x120/0x260
do_tag_check_fault+0x20/0x34
do_mem_abort+0x54/0xa8
el1_abort+0x3c/0x5c
el1h_64_sync_handler+0x40/0xcc
el1h_64_sync+0x7c/0x80
mt76_rx_poll_complete+0x280/0x470
mt76_dma_rx_poll+0x114/0x51c
mt792x_poll_rx+0x60/0xf8
napi_threaded_poll_loop+0xe0/0x450
napi_threaded_poll+0x80/0x9c
kthread+0x11c/0x158
ret_from_fork+0x10/0x20

Fixes: c948b5da6bbe ("wifi: mt76: mt7925: add Mediatek Wi-Fi7 driver for mt7925 chips")
Signed-off-by: Eason Lai <Eason.Lai@mediatek.com>
---
v2: fix mt76x02 build errors
v3: fix mt76x02 build error due to variable set but not used
v4: fix use-after-free in MLO
v5: correct commit message
v6: correct commit message
---
 .../net/wireless/mediatek/mt76/mt7925/main.c  | 36 ++++++++++++++++++-
 1 file changed, 35 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/mediatek/mt76/mt7925/main.c b/drivers/net/wireless/mediatek/mt76/mt7925/main.c
index 73d3722739d0..e3fb6392eda2 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7925/main.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7925/main.c
@@ -2410,6 +2410,40 @@ static void mt7925_channel_switch_rx_beacon(struct ieee80211_hw *hw,
 	}
 }
 
+static void mt7925_sta_pre_rcu_remove(struct ieee80211_hw *hw,
+				      struct ieee80211_vif *vif,
+				      struct ieee80211_sta *sta)
+{
+	struct mt76_phy *phy = hw->priv;
+	struct mt76_dev *dev = phy->dev;
+	struct mt76_wcid *wcid = (struct mt76_wcid *)sta->drv_priv;
+
+	mutex_lock(&dev->mutex);
+	spin_lock_bh(&dev->status_lock);
+
+	if (ieee80211_vif_is_mld(vif)) {
+		struct mt792x_sta *msta = (struct mt792x_sta *)sta->drv_priv;
+		struct mt792x_vif *mvif = (struct mt792x_vif *)vif->drv_priv;
+		unsigned long valid = mvif->valid_links;
+		struct mt792x_link_sta *mlink;
+		unsigned int link_id;
+
+		for_each_set_bit(link_id, &valid, IEEE80211_MLD_MAX_NUM_LINKS) {
+			mlink = mt792x_sta_to_link(msta, link_id);
+			if (!mlink || !mlink->wcid.sta)
+				continue;
+			if (mlink->wcid.idx < ARRAY_SIZE(dev->wcid))
+				rcu_assign_pointer(dev->wcid[mlink->wcid.idx],
+						   NULL);
+		}
+	} else {
+		rcu_assign_pointer(dev->wcid[wcid->idx], NULL);
+	}
+
+	spin_unlock_bh(&dev->status_lock);
+	mutex_unlock(&dev->mutex);
+}
+
 const struct ieee80211_ops mt7925_ops = {
 	.tx = mt792x_tx,
 	.start = mt7925_start,
@@ -2422,7 +2456,7 @@ const struct ieee80211_ops mt7925_ops = {
 	.start_ap = mt7925_start_ap,
 	.stop_ap = mt7925_stop_ap,
 	.sta_state = mt76_sta_state,
-	.sta_pre_rcu_remove = mt76_sta_pre_rcu_remove,
+	.sta_pre_rcu_remove = mt7925_sta_pre_rcu_remove,
 	.set_key = mt7925_set_key,
 	.sta_set_decap_offload = mt7925_sta_set_decap_offload,
 #if IS_ENABLED(CONFIG_IPV6)
-- 
2.45.2