scsi: message: mptlan: Fix use after free bug in mptlan_remove() due to race condition

scsi: message: mptlan: Fix use after free bug in mptlan_remove() due to race condition

mptlan_probe() calls mpt_register_lan_device() which initializes the
&priv->post_buckets_task workqueue. A call to
mpt_lan_wake_post_buckets_task() will subsequently start the work.

During driver unload in mptlan_remove() the following race may occur:

CPU0                  CPU1

                    |mpt_lan_post_receive_buckets_work()
mptlan_remove()     |
  free_netdev()     |
    kfree(dev);     |
                    |
                    | dev->mtu
                    |   //use

Fix this by finishing the work prior to cleaning up in mptlan_remove().

[mkp: we really should remove mptlan instead of attempting to fix it]

Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
Link: https://lore.kernel.org/r/20230318081635.796479-1-zyytlz.wz@163.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>