firewire-sbp2: fix panic after rmmod with slow targets

If firewire-sbp2 starts a login to a target that doesn't complete ORBs in a timely manner (and has to retry the login), and the module is removed before the operation times out, you end up with a null-pointer dereference and a kernel panic.

This happens because the code in sbp2_remove() just does a sbp2_target_put(), assuming it will be the last remaining reference. If there are jobs in the workqueue, this is not the case, and the module is successfully unloaded while references still exist.

This patch cancels pending work for each unit in sbp2_remove(), which hopefully means there are no extra references around that prevent us from unloading. This fixes my crash.

---
 drivers/firewire/sbp2.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

index 41841a3..3867aaa 100644
@@ -1198,6 +1198,11 @@ static int sbp2_remove(struct device *dev)
 {
 	struct fw_unit *unit = fw_unit(dev);
 	struct sbp2_target *tgt = dev_get_drvdata(&unit->device);
+	struct sbp2_logical_unit *lu, *next;
+
+	list_for_each_entry_safe(lu, next, &tgt->lu_list, link) {
+		cancel_delayed_work_sync(&lu->work);
+	}
 
 	sbp2_target_put(tgt);
 	return 0;

1.7.5.4