net/smc: cancel event worker during device removal

During IB device removal, cancel the event worker before the device
structure is freed.

Fixes: a4cf0443 ("smc: introduce SMC as an IB-client")
Reported-by: syzbot+b297c6825752e7a07272@syzkaller.appspotmail.com
Signed-off-by: NKarsten Graul <kgraul@linux.ibm.com>
Reviewed-by: NUrsula Braun <ubraun@linux.ibm.com>
Reviewed-by: NLeon Romanovsky <leonro@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/smc/smc_ib.c

@@ -582,6 +582,7 @@ static void smc_ib_remove_dev(struct ib_device *ibdev, void *client_data)
 	smc_smcr_terminate_all(smcibdev);
 	smc_ib_cleanup_per_ibdev(smcibdev);
 	ib_unregister_event_handler(&smcibdev->event_handler);
+	cancel_work_sync(&smcibdev->port_event_work);
 	kfree(smcibdev);
 }