[PATCH 4.4 29/56] IB/core: Fix sysfs registration error flow

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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

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

From: Jack Morgenstein <jackm@dev.mellanox.co.il>

commit b312be3d87e4c80872cbea869e569175c5eb0f9a upstream.

The kernel commit cited below restructured ib device management
so that the device kobject is initialized in ib_alloc_device.

As part of the restructuring, the kobject is now initialized in
procedure ib_alloc_device, and is later added to the device hierarchy
in the ib_register_device call stack, in procedure
ib_device_register_sysfs (which calls device_add).

However, in the ib_device_register_sysfs error flow, if an error
occurs following the call to device_add, the cleanup procedure
device_unregister is called. This call results in the device object
being deleted -- which results in various use-after-free crashes.

The correct cleanup call is device_del -- which undoes device_add
without deleting the device object.

The device object will then (correctly) be deleted in the
ib_register_device caller's error cleanup flow, when the caller invokes
ib_dealloc_device.

Fixes: 55aeed06544f6 ("IB/core: Make ib_alloc_device init the kobject")
Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/infiniband/core/sysfs.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/infiniband/core/sysfs.c
+++ b/drivers/infiniband/core/sysfs.c
@@ -863,7 +863,7 @@ err_put:
 	free_port_list_attributes(device);
 
 err_unregister:
-	device_unregister(class_dev);
+	device_del(class_dev);
 
 err:
 	return ret;