[PATCH v5 04/10] lpfc: Check fc4_xpt_flags before decrementing ndlp kref on FDISC error

[Nigel Kirkland <nkirkland2304@gmail.com>]

The current initial kref count drop logic for an ndlp that fails FDISC
assumes that the ndlp has never registered with transport layer and thus
the lpfc_dev_loss_tmo_callbk never called.  However, a failed FDISC can
occur after a successful transport layer registration too.  So,
lpfc_dev_loss_tmo_callbk can occur and there is a potential use-after-free
on the ndlp.

Check ndlp->fc4_xpt_flags if previously registered with an upper layer
transport and check ndlp->nlp_flags if there is a LPFC_EVT_DEV_LOSS work
pending.  If not previously registered nor LPFC_EVT_DEV_LOSS work pending,
then set the NLP_DROPPED flag as before and decrement the initial kref on
FDISC error.  However, if ndlp has been previously registered, then let the
pre-existing logic for each transport's respective dev_loss_tmo_callbk
perform the initial kref decrement.

Signed-off-by: Nigel Kirkland <nkirkland2304@gmail.com>
---
 drivers/scsi/lpfc/lpfc_els.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/drivers/scsi/lpfc/lpfc_els.c b/drivers/scsi/lpfc/lpfc_els.c
index 6f6394a0047c..45aad4cd2dc8 100644
--- a/drivers/scsi/lpfc/lpfc_els.c
+++ b/drivers/scsi/lpfc/lpfc_els.c
@@ -11416,7 +11416,6 @@ lpfc_cmpl_els_fdisc(struct lpfc_hba *phba, struct lpfc_iocbq *cmdiocb,
 		ulp_status, ulp_word4, vport->fc_prevDID);
 
 	if (ulp_status) {
-
 		if (lpfc_fabric_login_reqd(phba, cmdiocb, rspiocb)) {
 			lpfc_retry_pport_discovery(phba);
 			goto out;
@@ -11427,11 +11426,22 @@ lpfc_cmpl_els_fdisc(struct lpfc_hba *phba, struct lpfc_iocbq *cmdiocb,
 			goto out;
 		/* Warn FDISC status */
 		lpfc_vlog_msg(vport, KERN_WARNING, LOG_ELS,
-			      "0126 FDISC cmpl status: x%x/x%x)\n",
-			      ulp_status, ulp_word4);
+			      "0126 FDISC cmpl status: (x%x/x%x) ndlp x%px "
+			      "Data: x%lx x%x x%x x%x x%x x%x x%x x%x x%x\n",
+			      ulp_status, ulp_word4, ndlp, ndlp->nlp_flag,
+			      ndlp->nlp_DID, ndlp->nlp_last_elscmd,
+			      ndlp->nlp_type, ndlp->nlp_rpi, ndlp->nlp_state,
+			      ndlp->nlp_prev_state, ndlp->fc4_xpt_flags,
+			      kref_read(&ndlp->kref));
 
-		/* drop initial reference */
-		if (!test_and_set_bit(NLP_DROPPED, &ndlp->nlp_flag))
+		/* If have not previously registered with transport layer and no
+		 * LPFC_EVT_DEV_LOSS work pending, then drop initial reference.
+		 * Otherwise, let the dev_loss_tmo_callbk drop the initial
+		 * reference.
+		 */
+		if (!(ndlp->fc4_xpt_flags & (SCSI_XPT_REGD | NVME_XPT_REGD)) &&
+		    !test_bit(NLP_IN_DEV_LOSS, &ndlp->nlp_flag) &&
+		    !test_and_set_bit(NLP_DROPPED, &ndlp->nlp_flag))
 			lpfc_nlp_put(ndlp);
 
 		goto fdisc_failed;
-- 
2.38.0