linux-kernel - [char-misc-next 2/3] mei: bus: do not start a read for disconnected clients

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Date:   Thu, 29 Oct 2020 11:54:43 +0200
From:   Tomas Winkler <tomas.winkler@...el.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Alexander Usyskin <alexander.usyskin@...el.com>,
        linux-kernel@...r.kernel.org,
        Tomas Winkler <tomas.winkler@...el.com>
Subject: [char-misc-next 2/3] mei: bus: do not start a read for disconnected clients

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

Avoid queuing reads and registering rx callbacks in
case the client is not connected, to prevent null
dereferencing and memory leaks.

Signed-off-by: Alexander Usyskin <alexander.usyskin@...el.com>
Signed-off-by: Tomas Winkler <tomas.winkler@...el.com>
---
 drivers/misc/mei/bus.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/mei/bus.c b/drivers/misc/mei/bus.c
index 9cdaa7f3af23..1a54bf3ed0c3 100644
--- a/drivers/misc/mei/bus.c
+++ b/drivers/misc/mei/bus.c
@@ -276,7 +276,8 @@ static void mei_cl_bus_rx_work(struct work_struct *work)
 		cldev->rx_cb(cldev);
 
 	mutex_lock(&bus->device_lock);
-	mei_cl_read_start(cldev->cl, mei_cl_mtu(cldev->cl), NULL);
+	if (mei_cl_is_connected(cldev->cl))
+		mei_cl_read_start(cldev->cl, mei_cl_mtu(cldev->cl), NULL);
 	mutex_unlock(&bus->device_lock);
 }
 
@@ -364,7 +365,10 @@ int mei_cldev_register_rx_cb(struct mei_cl_device *cldev, mei_cldev_cb_t rx_cb)
 	INIT_WORK(&cldev->rx_work, mei_cl_bus_rx_work);
 
 	mutex_lock(&bus->device_lock);
-	ret = mei_cl_read_start(cldev->cl, mei_cl_mtu(cldev->cl), NULL);
+	if (mei_cl_is_connected(cldev->cl))
+		ret = mei_cl_read_start(cldev->cl, mei_cl_mtu(cldev->cl), NULL);
+	else
+		ret = -ENODEV;
 	mutex_unlock(&bus->device_lock);
 	if (ret && ret != -EBUSY)
 		return ret;
-- 
2.25.4