linux-kernel - [PATCH 4.9 079/222] ath9k: Fix a locking bug in ath9k_add

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Message-Id: <20191122100909.124357643@linuxfoundation.org>
Date:   Fri, 22 Nov 2019 11:26:59 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dan Carpenter <dan.carpenter@...cle.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.9 079/222] ath9k: Fix a locking bug in ath9k_add_interface()

From: Dan Carpenter <dan.carpenter@...cle.com>

[ Upstream commit 461cf036057477805a8a391e5fd0f5264a5e56a8 ]

We tried to revert commit d9c52fd17cb4 ("ath9k: fix tx99 with monitor
mode interface") but accidentally missed part of the locking change.

The lock has to be held earlier so that we're holding it when we do
"sc->tx99_vif = vif;" and also there in the current code there is a
stray unlock before we have taken the lock.

Fixes: 6df0580be8bc ("ath9k: add back support for using active monitor interfaces for tx99")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Kalle Valo <kvalo@...eaurora.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/wireless/ath/ath9k/main.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/net/wireless/ath/ath9k/main.c b/drivers/net/wireless/ath/ath9k/main.c
index f6151a00041d6..abc997427bae5 100644
--- a/drivers/net/wireless/ath/ath9k/main.c
+++ b/drivers/net/wireless/ath/ath9k/main.c
@@ -1249,6 +1249,7 @@ static int ath9k_add_interface(struct ieee80211_hw *hw,
 	struct ath_vif *avp = (void *)vif->drv_priv;
 	struct ath_node *an = &avp->mcast_node;
 
+	mutex_lock(&sc->mutex);
 	if (IS_ENABLED(CONFIG_ATH9K_TX99)) {
 		if (sc->cur_chan->nvifs >= 1) {
 			mutex_unlock(&sc->mutex);
@@ -1257,8 +1258,6 @@ static int ath9k_add_interface(struct ieee80211_hw *hw,
 		sc->tx99_vif = vif;
 	}
 
-	mutex_lock(&sc->mutex);
-
 	ath_dbg(common, CONFIG, "Attach a VIF of type: %d\n", vif->type);
 	sc->cur_chan->nvifs++;
 
-- 
2.20.1