[XFRM]: Fix existence lookup in xfrm_state_find

Use 'daddr' instead of &tmpl->id.daddr, since the latter
might be zero.  Also, only perform the lookup when
tmpl->id.spi is non-zero.
Signed-off-by: NPatrick McHardy <kaber@trash.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/xfrm/xfrm_state.c

@@ -357,8 +357,9 @@ xfrm_state_find(xfrm_address_t *daddr, xfrm_address_t *saddr,
 
 	x = best;
 	if (!x && !error && !acquire_in_progress) {
-		x0 = afinfo->state_lookup(&tmpl->id.daddr, tmpl->id.spi, tmpl->id.proto);
-		if (x0 != NULL) {
+		if (tmpl->id.spi &&
+		    (x0 = afinfo->state_lookup(daddr, tmpl->id.spi,
+		                               tmpl->id.proto)) != NULL) {
 			xfrm_state_put(x0);
 			error = -EEXIST;
 			goto out;