scsi: lpfc: Fix pointer defereference before it is null checked issue

There is a null check on pointer lpfc_cmd after the pointer has been
dereferenced when pointers rdata and ndlp are initialized at the start of
the function. Fix this by only assigning rdata and ndlp after the pointer
lpfc_cmd has been null checked.

Link: https://lore.kernel.org/r/20201118131345.460631-1-colin.king@canonical.com
Fixes: 96e209be ("scsi: lpfc: Convert SCSI I/O completions to SLI-3 and SLI-4 handlers")
Reviewed-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Addresses-Coverity: ("Dereference before null check")

drivers/scsi/lpfc/lpfc_scsi.c

@@ -4022,8 +4022,8 @@ lpfc_fcp_io_cmd_wqe_cmpl(struct lpfc_hba *phba, struct lpfc_iocbq *pwqeIn,
 	struct lpfc_io_buf *lpfc_cmd =
 		(struct lpfc_io_buf *)pwqeIn->context1;
 	struct lpfc_vport *vport = pwqeIn->vport;
-	struct lpfc_rport_data *rdata = lpfc_cmd->rdata;
-	struct lpfc_nodelist *ndlp = rdata->pnode;
+	struct lpfc_rport_data *rdata;
+	struct lpfc_nodelist *ndlp;
 	struct scsi_cmnd *cmd;
 	unsigned long flags;
 	struct lpfc_fast_path_event *fast_path_evt;
@@ -4040,6 +4040,9 @@ lpfc_fcp_io_cmd_wqe_cmpl(struct lpfc_hba *phba, struct lpfc_iocbq *pwqeIn,
 		return;
 	}
 
+	rdata = lpfc_cmd->rdata;
+	ndlp = rdata->pnode;
+
 	if (bf_get(lpfc_wcqe_c_xb, wcqe)) {
 		/* TOREMOVE - currently this flag is checked during
 		 * the release of lpfc_iocbq. Remove once we move