linux-kernel - [PATCH AUTOSEL 6.1 42/57] wifi: iwlwifi: mvm: Add locking to the rate read flow

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Message-Id: <20230525183607.1793983-42-sashal@kernel.org>
Date:   Thu, 25 May 2023 14:35:52 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Ariel Malamud <ariel.malamud@...el.com>,
        Gregory Greenman <gregory.greenman@...el.com>,
        Johannes Berg <johannes.berg@...el.com>,
        Sasha Levin <sashal@...nel.org>, kvalo@...nel.org,
        benjamin.berg@...el.com, trix@...hat.com,
        mordechay.goodstein@...el.com, linux-wireless@...r.kernel.org
Subject: [PATCH AUTOSEL 6.1 42/57] wifi: iwlwifi: mvm: Add locking to the rate read flow

From: Ariel Malamud <ariel.malamud@...el.com>

[ Upstream commit a8938bc881d2a03f9b77f19fae924fe798a01285 ]

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@...el.com>
Signed-off-by: Gregory Greenman <gregory.greenman@...el.com>
Link: https://lore.kernel.org/r/20230514120631.b52c9ed5c379.I15290b78e0d966c1b68278263776ca9de841d5fe@changeid
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 0b50b816684a0..2be6801d48aca 100644
--- a/drivers/net/wireless/intel/iwlwifi/mvm/rs.c
+++ b/drivers/net/wireless/intel/iwlwifi/mvm/rs.c
@@ -2692,6 +2692,8 @@ 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;
@@ -2706,6 +2708,7 @@ 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,
-- 
2.39.2