scsi: lpfc: Fix FLOGI failure due to accessing a freed node

After an initial successful FLOGI into the switch, if a subsequent FLOGI
fails the driver crashed accessing a node struct. On FLOGI error, the flogi
completion logic triggers the final dereference on the node structure
without checking if it is registered with a backend. The devloss logic is
triggered after node is freed leading to the access of freed node.

Fix by adjusting the error path to not take the final dereferece if there
is an outstanding transport registration. Let the transport devloss call
remove the final reference.

Link: https://lore.kernel.org/r/20210301171821.3427-6-jsmart2021@gmail.com
Co-developed-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/lpfc/lpfc_els.c

@@ -1182,7 +1182,8 @@ lpfc_cmpl_els_flogi(struct lpfc_hba *phba, struct lpfc_iocbq *cmdiocb,
 	phba->fcf.fcf_flag &= ~FCF_DISCOVERY;
 	spin_unlock_irq(&phba->hbalock);
 
-	lpfc_nlp_put(ndlp);
+	if (!(ndlp->fc4_xpt_flags & (SCSI_XPT_REGD | NVME_XPT_REGD)))
+		lpfc_nlp_put(ndlp);
 	if (!lpfc_error_lost_link(irsp)) {
 		/* FLOGI failed, so just use loop map to make discovery list */
 		lpfc_disc_list_loopmap(vport);