scsi: lpfc: fix pci hot plug crash in list_add call

During pci hot plug, the kernel crashes in a list_add_call

The lookup by tag function will return null if the IOCB is out of range
or does not have the on txcmplq flag set.

Fix: Check for null return from lookup by tag.

Cc: <stable@vger.kernel.org> # 4.12+
Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <james.smart@broadcom.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/lpfc/lpfc_sli.c

@@ -12507,19 +12507,21 @@ lpfc_sli4_els_wcqe_to_rspiocbq(struct lpfc_hba *phba,
 	/* Look up the ELS command IOCB and create pseudo response IOCB */
 	cmdiocbq = lpfc_sli_iocbq_lookup_by_tag(phba, pring,
 				bf_get(lpfc_wcqe_c_request_tag, wcqe));
-	/* Put the iocb back on the txcmplq */
-	lpfc_sli_ringtxcmpl_put(phba, pring, cmdiocbq);
-	spin_unlock_irqrestore(&pring->ring_lock, iflags);
-
 	if (unlikely(!cmdiocbq)) {
+		spin_unlock_irqrestore(&pring->ring_lock, iflags);
 		lpfc_printf_log(phba, KERN_WARNING, LOG_SLI,
 				"0386 ELS complete with no corresponding "
-				"cmdiocb: iotag (%d)\n",
-				bf_get(lpfc_wcqe_c_request_tag, wcqe));
+				"cmdiocb: 0x%x 0x%x 0x%x 0x%x\n",
+				wcqe->word0, wcqe->total_data_placed,
+				wcqe->parameter, wcqe->word3);
 		lpfc_sli_release_iocbq(phba, irspiocbq);
 		return NULL;
 	}
 
+	/* Put the iocb back on the txcmplq */
+	lpfc_sli_ringtxcmpl_put(phba, pring, cmdiocbq);
+	spin_unlock_irqrestore(&pring->ring_lock, iflags);
+
 	/* Fake the irspiocbq and copy necessary response information */
 	lpfc_sli4_iocb_param_transfer(phba, irspiocbq, cmdiocbq, wcqe);
 
@@ -17134,6 +17136,7 @@ lpfc_sli4_handle_mds_loopback(struct lpfc_vport *vport,
 	if (pcmd && pcmd->virt)
 		dma_pool_free(phba->lpfc_drb_pool, pcmd->virt, pcmd->phys);
 	kfree(pcmd);
+	if (iocbq)
 		lpfc_sli_release_iocbq(phba, iocbq);
 	lpfc_in_buf_free(phba, &dmabuf->dbuf);
 }