scsi: ufs: core: Fix an error handler crash

The UFS error handler may be activated before SCSI scanning has started
and hence before hba->ufs_device_wlun has been set. Check the
hba->ufs_device_wlun pointer before using it.

Cc: Peter Wang <peter.wang@mediatek.com>
Cc: Nitin Rawat <nitin.rawat@oss.qualcomm.com>
Fixes: e23ef4f ("scsi: ufs: core: Fix error handler host_sem issue")
Fixes: f966e02 ("scsi: ufs: core: Fix runtime suspend error deadlock")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Peter Wang <peter.wang@mediatek.com>
Reviewed-by: Nitin Rawat <nitin.rawat@oss.qualcomm.com>
Tested-by: Nitin Rawat <nitin.rawat@oss.qualcomm.com> #SM8750
Link: https://patch.msgid.link/20251204170457.994851-1-bvanassche@acm.org
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Author: bvanassche

drivers/ufs/core/ufshcd.c

@@ -6699,19 +6699,22 @@ static void ufshcd_err_handler(struct work_struct *work)
 		 hba->saved_uic_err, hba->force_reset,
 		 ufshcd_is_link_broken(hba) ? "; link is broken" : "");
 
-	/*
-	 * Use ufshcd_rpm_get_noresume() here to safely perform link recovery
-	 * even if an error occurs during runtime suspend or runtime resume.
-	 * This avoids potential deadlocks that could happen if we tried to
-	 * resume the device while a PM operation is already in progress.
-	 */
-	ufshcd_rpm_get_noresume(hba);
-	if (hba->pm_op_in_progress) {
-		ufshcd_link_recovery(hba);
+	if (hba->ufs_device_wlun) {
+		/*
+		 * Use ufshcd_rpm_get_noresume() here to safely perform link
+		 * recovery even if an error occurs during runtime suspend or
+		 * runtime resume. This avoids potential deadlocks that could
+		 * happen if we tried to resume the device while a PM operation
+		 * is already in progress.
+		 */
+		ufshcd_rpm_get_noresume(hba);
+		if (hba->pm_op_in_progress) {
+			ufshcd_link_recovery(hba);
+			ufshcd_rpm_put(hba);
+			return;
+		}
 		ufshcd_rpm_put(hba);
-		return;
 	}
-	ufshcd_rpm_put(hba);
 
 	down(&hba->host_sem);
 	spin_lock_irqsave(hba->host->host_lock, flags);