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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, Thara Gopinath <thara.gopinath@linaro.org>,
        Zhang Rui <rui.zhang@intel.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.20 094/352] thermal: Fix locking in cooling device sysfs update cur_state
Date:   Mon, 11 Feb 2019 15:15:21 +0100
Message-Id: <20190211141851.856039832@linuxfoundation.org>
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4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit 68000a0d983f539c95ebe5dccd4f29535c7ac0af ]

Sysfs interface to update cooling device cur_state does not
currently holding cooling device lock sometimes leading to
stale values in cur_state if getting updated simultanelously
from user space and thermal framework. Adding the proper locking
code fixes this issue.

Signed-off-by: Thara Gopinath <thara.gopinath@linaro.org>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/thermal/thermal_sysfs.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c
index 2241ceae7d7f..aa99edb4dff7 100644
--- a/drivers/thermal/thermal_sysfs.c
+++ b/drivers/thermal/thermal_sysfs.c
@@ -712,11 +712,14 @@ cur_state_store(struct device *dev, struct device_attribute *attr,
 	if ((long)state < 0)
 		return -EINVAL;
 
+	mutex_lock(&cdev->lock);
+
 	result = cdev->ops->set_cur_state(cdev, state);
-	if (result)
-		return result;
-	thermal_cooling_device_stats_update(cdev, state);
-	return count;
+	if (!result)
+		thermal_cooling_device_stats_update(cdev, state);
+
+	mutex_unlock(&cdev->lock);
+	return result ? result : count;
 }
 
 static struct device_attribute
-- 
2.19.1