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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Felix Fietkau <nbd@nbd.name>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.4 055/388] mt76: do not use devm API for led classdev
Date:   Tue, 29 Sep 2020 12:56:26 +0200
Message-Id: <20200929110013.158835994@linuxfoundation.org>
In-Reply-To: <20200929110010.467764689@linuxfoundation.org>
References: <20200929110010.467764689@linuxfoundation.org>
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From: Felix Fietkau <nbd@nbd.name>

[ Upstream commit 36f7e2b2bb1de86f0072cd49ca93d82b9e8fd894 ]

With the devm API, the unregister happens after the device cleanup is done,
after which the struct mt76_dev which contains the led_cdev has already been
freed. This leads to a use-after-free bug that can crash the system.

Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/wireless/mediatek/mt76/mac80211.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireless/mediatek/mt76/mac80211.c b/drivers/net/wireless/mediatek/mt76/mac80211.c
index 1a2c143b34d01..7be5806a1c398 100644
--- a/drivers/net/wireless/mediatek/mt76/mac80211.c
+++ b/drivers/net/wireless/mediatek/mt76/mac80211.c
@@ -105,7 +105,15 @@ static int mt76_led_init(struct mt76_dev *dev)
 		dev->led_al = of_property_read_bool(np, "led-active-low");
 	}
 
-	return devm_led_classdev_register(dev->dev, &dev->led_cdev);
+	return led_classdev_register(dev->dev, &dev->led_cdev);
+}
+
+static void mt76_led_cleanup(struct mt76_dev *dev)
+{
+	if (!dev->led_cdev.brightness_set && !dev->led_cdev.blink_set)
+		return;
+
+	led_classdev_unregister(&dev->led_cdev);
 }
 
 static void mt76_init_stream_cap(struct mt76_dev *dev,
@@ -360,6 +368,7 @@ void mt76_unregister_device(struct mt76_dev *dev)
 {
 	struct ieee80211_hw *hw = dev->hw;
 
+	mt76_led_cleanup(dev);
 	mt76_tx_status_check(dev, NULL, true);
 	ieee80211_unregister_hw(hw);
 }
-- 
2.25.1