Subject: [PATCH] rtw88: hold RCU lock when calling ieee80211_find_sta_by_ifaddr()

From: Shuah Khan <[email-masked]>
Date: Thu, 11 Feb 2021 19:13:07 -0700

ieee80211_find_sta_by_ifaddr() must be called under the RCU lock and
the resulting pointer is only valid under RCU lock as well.

Fix rtw_rx_addr_match_iter() to hold RCU read lock before it calls
ieee80211_find_sta_by_ifaddr() and release it when the resulting
pointer is no longer needed.

This problem was found while reviewing code to debug RCU warn from
ath10k_wmi_tlv_parse_peer_stats_info() and a subsequent manual audit
of other callers of ieee80211_find_sta_by_ifaddr() that don't hold
RCU read lock.

Signed-off-by: Shuah Khan <[email-masked]>
---
- Note: This patch is compile tested. I don't have access to
  hardware.

 drivers/net/wireless/realtek/rtw88/rx.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/wireless/realtek/rtw88/rx.c b/drivers/net/wireless/realtek/rtw88/rx.c
index 7087e385a9b3..4ab3d3e2bfab 100644
--- a/drivers/net/wireless/realtek/rtw88/rx.c
+++ b/drivers/net/wireless/realtek/rtw88/rx.c
@@ -111,6 +111,9 @@ static void rtw_rx_addr_match_iter(void *data, u8 *mac,
 		return;
 
 	rtw_rx_phy_stat(rtwdev, pkt_stat, hdr);
+
+	rcu_read_lock();
+
 	sta = ieee80211_find_sta_by_ifaddr(rtwdev->hw, hdr->addr2,
 					   vif->addr);
 	if (!sta)
@@ -118,6 +121,9 @@ static void rtw_rx_addr_match_iter(void *data, u8 *mac,
 
 	si = (struct rtw_sta_info *)sta->drv_priv;
 	ewma_rssi_add(&si->avg_rssi, pkt_stat->rssi);
+
+exit:
+	rcu_read_unlock();
 }
 
 static void rtw_rx_addr_match(struct rtw_dev *rtwdev,
-- 
2.27.0