[PATCH] wifi: mt76: mt7603: initialize global station WCID

[Cristian Papa <pcristian292@gmail.com>]

mt7603 uses a driver-private global station WCID for frames that have
neither a station nor a vif, including frames injected through a monitor
interface. Unlike the core global WCID initialized by
mt76_register_device(), this WCID is published without ever being passed
to mt76_wcid_init().

Since commit 0335c034e726 ("wifi: mt76: fix race condition related to
checking tx queue fill status"), mt76_tx() queues every such frame on the
WCID's tx_pending or tx_offchannel queue and links its tx_list. The first
injected frame therefore reaches __skb_queue_tail() with an uninitialized
sk_buff_head and dereferences a NULL prev pointer.

Initialize the WCID before publishing it.

The fix was tested on an MT7603 PCIe device. Three wildcard probe requests
were injected through a monitor interface. The hardware queue head and tail
advanced from 0 to 3 and a second radio captured the third request over the
air. No oops or reset occurred. After restoring AP mode, a 150 MB transfer
also completed without a reset.

Fixes: 0335c034e726 ("wifi: mt76: fix race condition related to checking tx queue fill status")
Cc: stable@vger.kernel.org
Signed-off-by: Cristian Papa <pcristian292@gmail.com>
---
 drivers/net/wireless/mediatek/mt76/mt7603/init.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/wireless/mediatek/mt76/mt7603/init.c b/drivers/net/wireless/mediatek/mt76/mt7603/init.c
index 10f2ec70c792..218ec406d2a8 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7603/init.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7603/init.c
@@ -230,6 +230,7 @@ mt7603_mac_init(struct mt7603_dev *dev)
 
 	eth_broadcast_addr(bc_addr);
 	mt7603_wtbl_init(dev, MT7603_WTBL_RESERVED, -1, bc_addr);
+	mt76_wcid_init(&dev->global_sta.wcid, 0);
 	dev->global_sta.wcid.idx = MT7603_WTBL_RESERVED;
 	rcu_assign_pointer(dev->mt76.wcid[MT7603_WTBL_RESERVED],
 			   &dev->global_sta.wcid);
-- 
2.51.0