--- 4.7-rc6-xenbus_scanf.orig/drivers/char/tpm/xen-tpmfront.c
+++ 4.7-rc6-xenbus_scanf/drivers/char/tpm/xen-tpmfront.c
@@ -344,7 +344,7 @@ static void backend_changed(struct xenbu
 			break;
 
 		if (xenbus_scanf(XBT_NIL, dev->otherend,
-				"feature-protocol-v2", "%d", &val) < 0)
+				"feature-protocol-v2", "%d", &val) <= 0)
 			val = 0;
 		if (!val) {
 			xenbus_dev_fatal(dev, -EINVAL,