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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,
        Vincent Donnefort <vincent.donnefort@arm.com>,
        John Einar Reitan <john.reitan@arm.com>,
        Chanwoo Choi <cw00.choi@samsung.com>,
        MyungJoo Ham <myungjoo.ham@samsung.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.19 043/220] PM / devfreq: stopping the governor before device_unregister()
Date:   Fri, 22 Nov 2019 11:26:48 +0100
Message-Id: <20191122100915.371382417@linuxfoundation.org>
In-Reply-To: <20191122100912.732983531@linuxfoundation.org>
References: <20191122100912.732983531@linuxfoundation.org>
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From: Vincent Donnefort <vincent.donnefort@arm.com>

[ Upstream commit 2f061fd0c2d852e32e03a903fccd810663c5c31e ]

device_release() is freeing the resources before calling the device
specific release callback which is, in the case of devfreq, stopping
the governor.

It is a problem as some governors are using the device resources. e.g.
simpleondemand which is using the devfreq deferrable monitoring work. If it
is not stopped before the resources are freed, it might lead to a use after
free.

Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
Reviewed-by: John Einar Reitan <john.reitan@arm.com>
[cw00.choi: Fix merge conflict]
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/devfreq/devfreq.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 8e21bedc74c38..bcd2279106760 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -578,10 +578,6 @@ static void devfreq_dev_release(struct device *dev)
 	list_del(&devfreq->node);
 	mutex_unlock(&devfreq_list_lock);
 
-	if (devfreq->governor)
-		devfreq->governor->event_handler(devfreq,
-						 DEVFREQ_GOV_STOP, NULL);
-
 	if (devfreq->profile->exit)
 		devfreq->profile->exit(devfreq->dev.parent);
 
@@ -717,7 +713,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
 err_init:
 	mutex_unlock(&devfreq_list_lock);
 
-	device_unregister(&devfreq->dev);
+	devfreq_remove_device(devfreq);
 	devfreq = NULL;
 err_dev:
 	if (devfreq)
@@ -738,6 +734,9 @@ int devfreq_remove_device(struct devfreq *devfreq)
 	if (!devfreq)
 		return -EINVAL;
 
+	if (devfreq->governor)
+		devfreq->governor->event_handler(devfreq,
+						 DEVFREQ_GOV_STOP, NULL);
 	device_unregister(&devfreq->dev);
 
 	return 0;
-- 
2.20.1