[SRU][Eoan] scsi: hisi_sas: Check sas_port before using it

[Ike Panhc]

From: Xiang Chen <chenxiang66 at hisilicon.com>

BugLink: https://bugs.launchpad.net/bugs/1855952

This patch fixes a potential NULL pointer reference on Hisilicon
SCSI host driver.

Need to check the structure sas_port before using it.

Link: https://lore.kernel.org/r/1573551059-107873-2-git-send-email-john.garry@huawei.com
Signed-off-by: Xiang Chen <chenxiang66 at hisilicon.com>
Signed-off-by: John Garry <john.garry at huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen at oracle.com>
(cherry picked from commit 8c39673d5474b95374df2104dc1f65205c5278b8)
Signed-off-by: Ike Panhc <ike.pan at canonical.com>
---
 drivers/scsi/hisi_sas/hisi_sas_main.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/hisi_sas/hisi_sas_main.c b/drivers/scsi/hisi_sas/hisi_sas_main.c
index cb746cfc2fa8..4a991e79ff23 100644
--- a/drivers/scsi/hisi_sas/hisi_sas_main.c
+++ b/drivers/scsi/hisi_sas/hisi_sas_main.c
@@ -1000,12 +1000,13 @@ static void hisi_sas_port_notify_formed(struct asd_sas_phy *sas_phy)
 	struct hisi_hba *hisi_hba = sas_ha->lldd_ha;
 	struct hisi_sas_phy *phy = sas_phy->lldd_phy;
 	struct asd_sas_port *sas_port = sas_phy->port;
-	struct hisi_sas_port *port = to_hisi_sas_port(sas_port);
+	struct hisi_sas_port *port;
 	unsigned long flags;
 
 	if (!sas_port)
 		return;
 
+	port = to_hisi_sas_port(sas_port);
 	spin_lock_irqsave(&hisi_hba->lock, flags);
 	port->port_attached = 1;
 	port->id = phy->port_id;
-- 
2.17.1