linux-kernel - [PATCH 4.19 009/280] mei: bus: move hw module get/put to probe/release

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Date:   Fri, 22 Mar 2019 12:12:42 +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,
        Alexander Usyskin <alexander.usyskin@...el.com>,
        Tomas Winkler <tomas.winkler@...el.com>
Subject: [PATCH 4.19 009/280] mei: bus: move hw module get/put to probe/release

4.19-stable review patch.  If anyone has any objections, please let me know.

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

From: Alexander Usyskin <alexander.usyskin@...el.com>

commit b5958faa34e2f99f3475ad89c52d98dfea079d33 upstream.

Fix unbalanced module reference counting during internal reset, which
prevents the drivers unloading.
Tracking mei_me/txe modules on mei client bus via
mei_cldev_enable/disable is error prone due to possible internal
reset flow, where clients are disconnected underneath.
Moving reference counting to probe and release of mei bus client
driver solves this issue in simplest way, as each client provides only
a single connection to a client bus driver.

Cc: <stable@...r.kernel.org>
Signed-off-by: Alexander Usyskin <alexander.usyskin@...el.com>
Signed-off-by: Tomas Winkler <tomas.winkler@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/misc/mei/bus.c |   21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

--- a/drivers/misc/mei/bus.c
+++ b/drivers/misc/mei/bus.c
@@ -541,17 +541,9 @@ int mei_cldev_enable(struct mei_cl_devic
 		goto out;
 	}
 
-	if (!mei_cl_bus_module_get(cldev)) {
-		dev_err(&cldev->dev, "get hw module failed");
-		ret = -ENODEV;
-		goto out;
-	}
-
 	ret = mei_cl_connect(cl, cldev->me_cl, NULL);
-	if (ret < 0) {
+	if (ret < 0)
 		dev_err(&cldev->dev, "cannot connect\n");
-		mei_cl_bus_module_put(cldev);
-	}
 
 out:
 	mutex_unlock(&bus->device_lock);
@@ -614,7 +606,6 @@ int mei_cldev_disable(struct mei_cl_devi
 	if (err < 0)
 		dev_err(bus->dev, "Could not disconnect from the ME client\n");
 
-	mei_cl_bus_module_put(cldev);
 out:
 	/* Flush queues and remove any pending read */
 	mei_cl_flush_queues(cl, NULL);
@@ -725,9 +716,16 @@ static int mei_cl_device_probe(struct de
 	if (!id)
 		return -ENODEV;
 
+	if (!mei_cl_bus_module_get(cldev)) {
+		dev_err(&cldev->dev, "get hw module failed");
+		return -ENODEV;
+	}
+
 	ret = cldrv->probe(cldev, id);
-	if (ret)
+	if (ret) {
+		mei_cl_bus_module_put(cldev);
 		return ret;
+	}
 
 	__module_get(THIS_MODULE);
 	return 0;
@@ -755,6 +753,7 @@ static int mei_cl_device_remove(struct d
 
 	mei_cldev_unregister_callbacks(cldev);
 
+	mei_cl_bus_module_put(cldev);
 	module_put(THIS_MODULE);
 	dev->driver = NULL;
 	return ret;