scsi: lpfc: Fix null pointer dereference in lpfc_prep_els_iocb()

It is possible to call lpfc_issue_els_plogi() passing a did for which no
matching ndlp is found. A call is then made to lpfc_prep_els_iocb() with a
null pointer to a lpfc_nodelist structure resulting in a null pointer
dereference.

Fix by returning an error status if no valid ndlp is found. Fix up comments
regarding ndlp reference counting.

Link: https://lore.kernel.org/r/20210301171821.3427-10-jsmart2021@gmail.com
Fixes: 4430f7fd09ec ("scsi: lpfc: Rework locations of ndlp reference taking")
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>

diff --git a/drivers/scsi/lpfc/lpfc_els.c b/drivers/scsi/lpfc/lpfc_els.c
index e0454c5..de67ba7 100644 (file)
--- a/drivers/scsi/lpfc/lpfc_els.c
+++ b/drivers/scsi/lpfc/lpfc_els.c
@@ -1,7 +1,7 @@
 /*******************************************************************
  * This file is part of the Emulex Linux Device Driver for         *
  * Fibre Channel Host Bus Adapters.                                *
- * Copyright (C) 2017-2020 Broadcom. All Rights Reserved. The term *
+ * Copyright (C) 2017-2021 Broadcom. All Rights Reserved. The term *
  * “Broadcom” refers to Broadcom Inc. and/or its subsidiaries.     *
  * Copyright (C) 2004-2016 Emulex.  All rights reserved.           *
  * EMULEX and SLI are trademarks of Emulex.                        *
@@ -2052,13 +2052,12 @@ out_freeiocb:
  * This routine issues a Port Login (PLOGI) command to a remote N_Port
  * (with the @did) for a @vport. Before issuing a PLOGI to a remote N_Port,
  * the ndlp with the remote N_Port DID must exist on the @vport's ndlp list.
- * This routine constructs the proper feilds of the PLOGI IOCB and invokes
+ * This routine constructs the proper fields of the PLOGI IOCB and invokes
  * the lpfc_sli_issue_iocb() routine to send out PLOGI ELS command.
  *
- * Note that, in lpfc_prep_els_iocb() routine, the reference count of ndlp
- * will be incremented by 1 for holding the ndlp and the reference to ndlp
- * will be stored into the context1 field of the IOCB for the completion
- * callback function to the PLOGI ELS command.
+ * Note that the ndlp reference count will be incremented by 1 for holding
+ * the ndlp and the reference to ndlp will be stored into the context1 field
+ * of the IOCB for the completion callback function to the PLOGI ELS command.
  *
  * Return code
  *   0 - Successfully issued a plogi for @vport
@@ -2076,29 +2075,28 @@ lpfc_issue_els_plogi(struct lpfc_vport *vport, uint32_t did, uint8_t retry)
        int ret;
 
        ndlp = lpfc_findnode_did(vport, did);
+       if (!ndlp)
+               return 1;
 
-       if (ndlp) {
-               /* Defer the processing of the issue PLOGI until after the
-                * outstanding UNREG_RPI mbox command completes, unless we
-                * are going offline. This logic does not apply for Fabric DIDs
-                */
-               if ((ndlp->nlp_flag & NLP_UNREG_INP) &&
-                   ((ndlp->nlp_DID & Fabric_DID_MASK) != Fabric_DID_MASK) &&
-                   !(vport->fc_flag & FC_OFFLINE_MODE)) {
-                       lpfc_printf_vlog(vport, KERN_INFO, LOG_DISCOVERY,
-                                        "4110 Issue PLOGI x%x deferred "
-                                        "on NPort x%x rpi x%x Data: x%px\n",
-                                        ndlp->nlp_defer_did, ndlp->nlp_DID,
-                                        ndlp->nlp_rpi, ndlp);
-
-                       /* We can only defer 1st PLOGI */
-                       if (ndlp->nlp_defer_did == NLP_EVT_NOTHING_PENDING)
-                               ndlp->nlp_defer_did = did;
-                       return 0;
-               }
+       /* Defer the processing of the issue PLOGI until after the
+        * outstanding UNREG_RPI mbox command completes, unless we
+        * are going offline. This logic does not apply for Fabric DIDs
+        */
+       if ((ndlp->nlp_flag & NLP_UNREG_INP) &&
+           ((ndlp->nlp_DID & Fabric_DID_MASK) != Fabric_DID_MASK) &&
+           !(vport->fc_flag & FC_OFFLINE_MODE)) {
+               lpfc_printf_vlog(vport, KERN_INFO, LOG_DISCOVERY,
+                                "4110 Issue PLOGI x%x deferred "
+                                "on NPort x%x rpi x%x Data: x%px\n",
+                                ndlp->nlp_defer_did, ndlp->nlp_DID,
+                                ndlp->nlp_rpi, ndlp);
+
+               /* We can only defer 1st PLOGI */
+               if (ndlp->nlp_defer_did == NLP_EVT_NOTHING_PENDING)
+                       ndlp->nlp_defer_did = did;
+               return 0;
        }
 
-       /* If ndlp is not NULL, we will bump the reference count on it */
        cmdsize = (sizeof(uint32_t) + sizeof(struct serv_parm));
        elsiocb = lpfc_prep_els_iocb(vport, 1, cmdsize, retry, ndlp, did,
                                     ELS_CMD_PLOGI);