[PATCH] 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>
---
 drivers/scsi/qedi/qedi_main.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/scsi/qedi/qedi_main.c b/drivers/scsi/qedi/qedi_main.c
index f2ee49756df8..25223f6f5344 100644
--- a/drivers/scsi/qedi/qedi_main.c
+++ b/drivers/scsi/qedi/qedi_main.c
@@ -2414,6 +2414,10 @@ static void __qedi_remove(struct pci_dev *pdev, int mode)
 	int rval;
 	u16 retry = 10;
 
+	/*cancel work*/
+	cancel_delayed_work_sync(&qedi->recovery_work);
+	cancel_delayed_work_sync(&qedi->board_disable_work);
+
 	if (mode == QEDI_MODE_NORMAL)
 		iscsi_host_remove(qedi->shost, false);
 	else if (mode == QEDI_MODE_SHUTDOWN)
-- 
2.25.1