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From:   gregory.greenman@intel.com
To:     johannes@sipsolutions.net
Cc:     linux-wireless@vger.kernel.org,
        Ariel Malamud <ariel.malamud@intel.com>,
        Gregory Greenman <gregory.greenman@intel.com>
Subject: [PATCH wireless 12/12] wifi: iwlwifi: mvm: Add locking to the rate read flow
Date:   Sun, 14 May 2023 12:15:55 +0300
Message-Id: <20230514120631.b52c9ed5c379.I15290b78e0d966c1b68278263776ca9de841d5fe@changeid>
In-Reply-To: <20230514091555.168392-1-gregory.greenman@intel.com>
References: <20230514091555.168392-1-gregory.greenman@intel.com>
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From: Ariel Malamud <ariel.malamud@intel.com>

The rs_drv_get_rate flow reads the lq_sta to return the optimal rate
for tx frames. This read flow is not protected thereby leaving
a small window, a few instructions wide, open to contention by an
asynchronous rate update. Indeed this race condition was hit and the
update occurred in the middle of the read.

Fix this by locking the lq_sta struct during read.

Signed-off-by: Ariel Malamud <ariel.malamud@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
---
 drivers/net/wireless/intel/iwlwifi/mvm/rs.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/rs.c b/drivers/net/wireless/intel/iwlwifi/mvm/rs.c
index a4c1e3bf4ff1..23266d0c9ce4 100644
--- a/drivers/net/wireless/intel/iwlwifi/mvm/rs.c
+++ b/drivers/net/wireless/intel/iwlwifi/mvm/rs.c
@@ -2691,6 +2691,8 @@ static void rs_drv_get_rate(void *mvm_r, struct ieee80211_sta *sta,
 		return;
 
 	lq_sta = mvm_sta;
+
+	spin_lock(&lq_sta->pers.lock);
 	iwl_mvm_hwrate_to_tx_rate_v1(lq_sta->last_rate_n_flags,
 				     info->band, &info->control.rates[0]);
 	info->control.rates[0].count = 1;
@@ -2705,6 +2707,7 @@ static void rs_drv_get_rate(void *mvm_r, struct ieee80211_sta *sta,
 		iwl_mvm_hwrate_to_tx_rate_v1(last_ucode_rate, info->band,
 					     &txrc->reported_rate);
 	}
+	spin_unlock(&lq_sta->pers.lock);
 }
 
 static void *rs_drv_alloc_sta(void *mvm_rate, struct ieee80211_sta *sta,
-- 
2.38.1