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From:   Ryder Lee <ryder.lee@mediatek.com>
To:     Felix Fietkau <nbd@nbd.name>
CC:     Lorenzo Bianconi <lorenzo.bianconi@redhat.com>,
        Shayne Chen <shayne.chen@mediatek.com>,
        Evelyn Tsai <evelyn.tsai@mediatek.com>,
        <linux-wireless@vger.kernel.org>,
        <linux-mediatek@lists.infradead.org>,
        Ryder Lee <ryder.lee@mediatek.com>
Subject: [PATCH 1/3] mt76 mt7915: take RCU read lock when calling ieee80211_bss_get_elem()
Date:   Wed, 14 Jul 2021 13:36:49 +0800
Message-ID: <510ef14986079c731ea2879b3095831b60e4f648.1626240767.git.ryder.lee@mediatek.com>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

As ieee80211_bss_get_elem() derefences an RCU to return ssid_ie, both
the call to this function and any operation on this variable need
protection by the RCU read lock.

Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
---
 drivers/net/wireless/mediatek/mt76/mt7915/mcu.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/wireless/mediatek/mt76/mt7915/mcu.c b/drivers/net/wireless/mediatek/mt76/mt7915/mcu.c
index 863aa18b3024..4d2e5b5e6389 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7915/mcu.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7915/mcu.c
@@ -923,12 +923,15 @@ static void mt7915_check_he_obss_narrow_bw_ru_iter(struct wiphy *wiphy,
 	struct mt7915_he_obss_narrow_bw_ru_data *data = _data;
 	const struct element *elem;
 
+	rcu_read_lock();
 	elem = ieee80211_bss_get_elem(bss, WLAN_EID_EXT_CAPABILITY);
 
 	if (!elem || elem->datalen < 10 ||
 	    !(elem->data[10] &
 	      WLAN_EXT_CAPA10_OBSS_NARROW_BW_RU_TOLERANCE_SUPPORT))
 		data->tolerated = false;
+
+	rcu_read_unlock();
 }
 
 static bool mt7915_check_he_obss_narrow_bw_ru(struct ieee80211_hw *hw,
-- 
2.29.2