[S390] cio: Use strict_strtoul() for attributes.

Make parsing of attribute writes handle incorrect input better.

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/drivers/s390/cio/device.c b/drivers/s390/cio/device.c
index e0c7adb..abfd601 100644
--- a/drivers/s390/cio/device.c
+++ b/drivers/s390/cio/device.c
@@ -512,8 +512,8 @@
 			     const char *buf, size_t count)
 {
 	struct ccw_device *cdev = to_ccwdev(dev);
-	int i, force;
-	char *tmp;
+	int force, ret;
+	unsigned long i;
 
 	if (atomic_cmpxchg(&cdev->private->onoff, 0, 1) != 0)
 		return -EAGAIN;
@@ -525,25 +525,30 @@
 	if (!strncmp(buf, "force\n", count)) {
 		force = 1;
 		i = 1;
+		ret = 0;
 	} else {
 		force = 0;
-		i = simple_strtoul(buf, &tmp, 16);
+		ret = strict_strtoul(buf, 16, &i);
 	}
-
+	if (ret)
+		goto out;
 	switch (i) {
 	case 0:
 		online_store_handle_offline(cdev);
+		ret = count;
 		break;
 	case 1:
 		online_store_handle_online(cdev, force);
+		ret = count;
 		break;
 	default:
-		count = -EINVAL;
+		ret = -EINVAL;
 	}
+out:
 	if (cdev->drv)
 		module_put(cdev->drv->owner);
 	atomic_set(&cdev->private->onoff, 0);
-	return count;
+	return ret;
 }
 
 static ssize_t