mei: return error on notification request to a disconnected client

BugLink: http://bugs.launchpad.net/bugs/1731915

[ Upstream commit 7c47d2ca ]

Request for a notification from a disconnected client will be ignored
silently by the FW but the caller should know that the operation hasn't
succeeded.
Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

drivers/misc/mei/client.c

@@ -1300,6 +1300,9 @@ int mei_cl_notify_request(struct mei_cl *cl, struct file *file, u8 request)
 		return -EOPNOTSUPP;
 	}
 
+	if (!mei_cl_is_connected(cl))
+		return -ENODEV;
+
 	rets = pm_runtime_get(dev->dev);
 	if (rets < 0 && rets != -EINPROGRESS) {
 		pm_runtime_put_noidle(dev->dev);