scsi: lpfc: Prevent 'use after free' memory overwrite in nvmet LS handling

Use-after-free memory overwrite detected. Problem reported
by Ewan Milne at Red Hat after running lpfc target with additional
memory checking enabled.

Race condition when lpfc_nvmet_xmt_ls_rsp_cmp frees the ctxp
memory in interrupt context before lpfc_nvmet_xmt_ls_rsp
clears a field in the ctxp after successfully issuing the wqe.

Remove the unnecessary ctxp write after reposting the rq buffer. The
ctxp->rqb_buffer field is not checked in LS handling after the wqe
is submitted.
Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Reported-by: Ewan Milne <emilne@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/lpfc/lpfc_nvmet.c

@@ -907,7 +907,6 @@ lpfc_nvmet_xmt_ls_rsp(struct nvmet_fc_target_port *tgtport,
 		 * before freeing ctxp and iocbq.
 		 */
 		lpfc_in_buf_free(phba, &nvmebuf->dbuf);
-		ctxp->rqb_buffer = 0;
 		atomic_inc(&nvmep->xmt_ls_rsp);
 		return 0;
 	}