vbf_stp_error(struct worker *wrk, struct busyobj *bo)
{
	ssize_t l, ll, o;
	double now;
	uint8_t *ptr;
	struct vsb *synth_body;

	CHECK_OBJ_NOTNULL(wrk, WORKER_MAGIC);
	CHECK_OBJ_NOTNULL(bo, BUSYOBJ_MAGIC);
	CHECK_OBJ_NOTNULL(bo->fetch_objcore, OBJCORE_MAGIC);
	AN(bo->fetch_objcore->flags & OC_F_BUSY);
	assert(bo->director_state == DIR_S_NULL);

	wrk->stats->fetch_failed++;

	now = W_TIM_real(wrk);
	VSLb_ts_busyobj(bo, "Error", now);

	if (bo->fetch_objcore->stobj->stevedore != NULL)
		ObjFreeObj(bo->wrk, bo->fetch_objcore);


	HTTP_Setup(bo->beresp, bo->ws, bo->vsl, SLT_BerespMethod);
	http_PutResponse(bo->beresp, "HTTP/1.1", 503, "Backend fetch failed");
	http_TimeHeader(bo->beresp, "Date: ", now);
	http_SetHeader(bo->beresp, "Server: Varnish");

	bo->fetch_objcore->t_origin = now;
	if (!VTAILQ_EMPTY(&bo->fetch_objcore->objhead->waitinglist)) {
		/*
		 * If there is a waitinglist, it means that there is no
		 * grace-able object, so cache the error return for a
		 * short time, so the waiting list can drain, rather than
		 * each objcore on the waiting list sequentially attempt
		 * to fetch from the backend.
		 */
		bo->fetch_objcore->ttl = 1;
		bo->fetch_objcore->grace = 5;
		bo->fetch_objcore->keep = 5;
	} else {
		bo->fetch_objcore->ttl = 0;
		bo->fetch_objcore->grace = 0;
		bo->fetch_objcore->keep = 0;
	}

	synth_body = VSB_new_auto();
	AN(synth_body);

	VCL_backend_error_method(bo->vcl, wrk, NULL, bo, synth_body);

	AZ(VSB_finish(synth_body));

	if (wrk->handling == VCL_RET_ABANDON || wrk->handling == VCL_RET_FAIL) {
		VSB_destroy(&synth_body);
		return (F_STP_FAIL);
	}

	if (wrk->handling == VCL_RET_RETRY) {
		VSB_destroy(&synth_body);
		if (bo->retries++ < cache_param->max_retries)
			return (F_STP_RETRY);
		VSLb(bo->vsl, SLT_VCL_Error, "Too many retries, failing");
		return (F_STP_FAIL);
	}

	assert(wrk->handling == VCL_RET_DELIVER);

	bo->vfc->bo = bo;
	bo->vfc->wrk = bo->wrk;
	bo->vfc->oc = bo->fetch_objcore;
	bo->vfc->http = bo->beresp;
	bo->vfc->esi_req = bo->bereq;

	if (vbf_beresp2obj(bo)) {
		(void)VFP_Error(bo->vfc, "Could not get storage");
		VSB_destroy(&synth_body);
		return (F_STP_FAIL);
	}

	ll = VSB_len(synth_body);
	o = 0;
	while (ll > 0) {
 		l = ll;
 		if (VFP_GetStorage(bo->vfc, &l, &ptr) != VFP_OK)
 			break;
		if (l > ll)
			l = ll;
 		memcpy(ptr, VSB_data(synth_body) + o, l);
 		VFP_Extend(bo->vfc, l);
 		ll -= l;
		o += l;
	}
	AZ(ObjSetU64(wrk, bo->fetch_objcore, OA_LEN, o));
	VSB_destroy(&synth_body);
	HSH_Unbusy(wrk, bo->fetch_objcore);
	ObjSetState(wrk, bo->fetch_objcore, BOS_FINISHED);
	return (F_STP_DONE);
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.