mei: bus: don't clean driver pointer

commit e852c2c251ed9c23ae6e3efebc5ec49adb504207 upstream.

It's not needed to set driver to NULL in mei_cl_device_remove()
which is bus_type remove() handler as this is done anyway
in __device_release_driver().

Actually this is causing an endless loop in driver_detach()
on ubuntu patched kernel, while removing (rmmod) the mei_hdcp module.
The reason list_empty(&drv->p->klist_devices.k_list) is always not-empty.
as the check is always true in  __device_release_driver()
	if (dev->driver != drv)
		return;

The non upstream patch is causing this behavior, titled:
'vfio -- release device lock before userspace requests'

Nevertheless the fix is correct also for the upstream.

Link: https://patchwork.ozlabs.org/project/ubuntu-kernel/patch/20180912085046.3401-2-apw@canonical.com/
Cc: <stable@vger.kernel.org>
Cc: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Link: https://lore.kernel.org/r/20200628225359.2185929-1-tomas.winkler@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/misc/mei/bus.c b/drivers/misc/mei/bus.c
index 8f6ab516041b471cb95a7b14515cb94c21adb8d3..73a93e3fc18d2dda1ca3c01e2c1c847a5c18b246 100644 (file)
--- a/drivers/misc/mei/bus.c
+++ b/drivers/misc/mei/bus.c
@@ -722,9 +722,8 @@ static int mei_cl_device_remove(struct device *dev)
        mei_cldev_unregister_callbacks(cldev);
 
        module_put(THIS_MODULE);
-       dev->driver = NULL;
-       return ret;
 
+       return ret;
 }
 
 static ssize_t name_show(struct device *dev, struct device_attribute *a,