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Subject[PATCH] mt76: hold RCU lock when calling ieee80211_find_sta_by_ifaddr()
Date
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 mt76_check_sta() 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 <skhan@linuxfoundation.org>
---
- Note: This patch is compile tested. I don't have access to
hardware.

drivers/net/wireless/mediatek/mt76/mac80211.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/mac80211.c b/drivers/net/wireless/mediatek/mt76/mac80211.c
index a840396f2c74..3c732da2a53f 100644
--- a/drivers/net/wireless/mediatek/mt76/mac80211.c
+++ b/drivers/net/wireless/mediatek/mt76/mac80211.c
@@ -867,6 +867,9 @@ mt76_check_sta(struct mt76_dev *dev, struct sk_buff *skb)
bool ps;

hw = mt76_phy_hw(dev, status->ext_phy);
+
+ rcu_read_lock();
+
if (ieee80211_is_pspoll(hdr->frame_control) && !wcid) {
sta = ieee80211_find_sta_by_ifaddr(hw, hdr->addr2, NULL);
if (sta)
@@ -876,7 +879,7 @@ mt76_check_sta(struct mt76_dev *dev, struct sk_buff *skb)
mt76_airtime_check(dev, skb);

if (!wcid || !wcid->sta)
- return;
+ goto exit;

sta = container_of((void *)wcid, struct ieee80211_sta, drv_priv);

@@ -886,17 +889,17 @@ mt76_check_sta(struct mt76_dev *dev, struct sk_buff *skb)
wcid->inactive_count = 0;

if (!test_bit(MT_WCID_FLAG_CHECK_PS, &wcid->flags))
- return;
+ goto exit;

if (ieee80211_is_pspoll(hdr->frame_control)) {
ieee80211_sta_pspoll(sta);
- return;
+ goto exit;
}

if (ieee80211_has_morefrags(hdr->frame_control) ||
!(ieee80211_is_mgmt(hdr->frame_control) ||
ieee80211_is_data(hdr->frame_control)))
- return;
+ goto exit;

ps = ieee80211_has_pm(hdr->frame_control);

@@ -905,7 +908,7 @@ mt76_check_sta(struct mt76_dev *dev, struct sk_buff *skb)
ieee80211_sta_uapsd_trigger(sta, status->tid);

if (!!test_bit(MT_WCID_FLAG_PS, &wcid->flags) == ps)
- return;
+ goto exit;

if (ps)
set_bit(MT_WCID_FLAG_PS, &wcid->flags);
@@ -914,6 +917,9 @@ mt76_check_sta(struct mt76_dev *dev, struct sk_buff *skb)

dev->drv->sta_ps(dev, sta, ps);
ieee80211_sta_ps_transition(sta, ps);
+
+exit:
+ rcu_read_unlock();
}

void mt76_rx_complete(struct mt76_dev *dev, struct sk_buff_head *frames,
--
2.27.0
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