[PATCH v2] scsi: qedi: Fix use after free bug in qedi_remove due to race condition

[Zheng Wang]

In qedi_probe, it calls __qedi_probe, which bound &qedi->recovery_work
with qedi_recovery_handler and bound &qedi->board_disable_work
with qedi_board_disable_work.

When it calls qedi_schedule_recovery_handler, it will finally
call schedule_delayed_work to start the work.

When we call qedi_remove to remove the driver, there
may be a sequence as follows:

Fix it by finishing the work before cleanup in qedi_remove.

CPU0                  CPU1

                     |qedi_recovery_handler
qedi_remove          |
  __qedi_remove      |
iscsi_host_free      |
scsi_host_put        |
//free shost         |
                     |iscsi_host_for_each_session
                     |//use qedi->shost

Fixes: 4b1068f5d74b ("scsi: qedi: Add MFW error recovery process")
Signed-off-by: Zheng Wang <zyytlz.wz@xxxxxxx>
---
v2:
- remove unnecessary comment suggested by Mike Christie and cancel the work
after qedi_ops->stop and qedi_ops->ll2->stop which ensure there is no more
work suggested by Manish Rangankar
---
 drivers/scsi/qedi/qedi_main.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/scsi/qedi/qedi_main.c b/drivers/scsi/qedi/qedi_main.c
index f2ee49756df8..45d359554182 100644
--- a/drivers/scsi/qedi/qedi_main.c
+++ b/drivers/scsi/qedi/qedi_main.c
@@ -2450,6 +2450,9 @@ static void __qedi_remove(struct pci_dev *pdev, int mode)
 		qedi_ops->ll2->stop(qedi->cdev);
 	}
 
+	cancel_delayed_work_sync(&qedi->recovery_work);
+	cancel_delayed_work_sync(&qedi->board_disable_work);
+
 	qedi_free_iscsi_pf_param(qedi);
 
 	rval = qedi_ops->common->update_drv_state(qedi->cdev, false);
-- 
2.25.1