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Commit 2da55cfd authored by Tomas Winkler's avatar Tomas Winkler Committed by Greg Kroah-Hartman
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mei: bus: use correct lock ordering 



The correct lock order is
  cl_bus_lock
    device_lock
      me_clients_rwsem

This order was violated in bus rescan and remove routines
when me_client_rwsem was locked before cl_bus_lock.

Chain exists of:
[    4.321653]   &dev->device_lock --> &dev->me_clients_rwsem -->
&dev->cl_bus_lock
[    4.321653]
[    4.321679]  Possible unsafe locking scenario:
[    4.321679]
[    4.321693]        CPU0                    CPU1
[    4.321701]        ----                    ----
[    4.321709]   lock(&dev->cl_bus_lock);
[    4.321720]
lock(&dev->me_clients_rwsem);
[    4.321733]                                lock(&dev->cl_bus_lock);
[    4.321745]   lock(&dev->device_lock);
[    4.321755]
[    4.321755]  *** DEADLOCK ***
[    4.321755]

Signed-off-by: default avatarTomas Winkler <tomas.winkler@intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 2be7010c

drivers/misc/mei/bus.c

+13 −5
Original line number Diff line number Diff line
@@ -830,17 +830,20 @@ static void mei_cl_bus_dev_stop(struct mei_cl_device *cldev) 
 * mei_cl_bus_dev_destroy - destroy me client devices object

 *

 * @cldev: me client device

 *

 * Locking: called under "dev->cl_bus_lock" lock

 */

static void mei_cl_bus_dev_destroy(struct mei_cl_device *cldev)

{



	WARN_ON(!mutex_is_locked(&cldev->bus->cl_bus_lock));



	if (!cldev->is_added)

		return;



	device_del(&cldev->dev);



	mutex_lock(&cldev->bus->cl_bus_lock);

	list_del_init(&cldev->bus_list);

	mutex_unlock(&cldev->bus->cl_bus_lock);



	cldev->is_added = 0;

	put_device(&cldev->dev);
@@ -866,8 +869,10 @@ void mei_cl_bus_remove_devices(struct mei_device *bus) 
{

	struct mei_cl_device *cldev, *next;



	mutex_lock(&bus->cl_bus_lock);

	list_for_each_entry_safe(cldev, next, &bus->device_list, bus_list)

		mei_cl_bus_remove_device(cldev);

	mutex_unlock(&bus->cl_bus_lock);

}
@@ -877,12 +882,16 @@ void mei_cl_bus_remove_devices(struct mei_device *bus) 
 *

 * @bus: mei device

 * @me_cl: me client

 *

 * Locking: called under "dev->cl_bus_lock" lock

 */

static void mei_cl_bus_dev_init(struct mei_device *bus,

				struct mei_me_client *me_cl)

{

	struct mei_cl_device *cldev;



	WARN_ON(!mutex_is_locked(&bus->cl_bus_lock));



	dev_dbg(bus->dev, "initializing %pUl", mei_me_cl_uuid(me_cl));



	if (me_cl->bus_added)
@@ -892,10 +901,8 @@ static void mei_cl_bus_dev_init(struct mei_device *bus, 
	if (!cldev)

		return;



	mutex_lock(&cldev->bus->cl_bus_lock);

	me_cl->bus_added = true;

	list_add_tail(&cldev->bus_list, &bus->device_list);

	mutex_unlock(&cldev->bus->cl_bus_lock);



}
@@ -910,12 +917,13 @@ void mei_cl_bus_rescan(struct mei_device *bus) 
	struct mei_cl_device *cldev, *n;

	struct mei_me_client *me_cl;



	mutex_lock(&bus->cl_bus_lock);



	down_read(&bus->me_clients_rwsem);

	list_for_each_entry(me_cl, &bus->me_clients, list)

		mei_cl_bus_dev_init(bus, me_cl);

	up_read(&bus->me_clients_rwsem);



	mutex_lock(&bus->cl_bus_lock);

	list_for_each_entry_safe(cldev, n, &bus->device_list, bus_list) {



		if (!mei_me_cl_is_active(cldev->me_cl)) {