[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>

drivers/s390/cio/css.c

@@ -705,13 +705,17 @@ css_cm_enable_store(struct device *dev, struct device_attribute *attr,
 {
 	struct channel_subsystem *css = to_css(dev);
 	int ret;
+	unsigned long val;
 
+	ret = strict_strtoul(buf, 16, &val);
+	if (ret)
+		return ret;
 	mutex_lock(&css->mutex);
-	switch (buf[0]) {
-	case '0':
+	switch (val) {
+	case 0:
 		ret = css->cm_enabled ? chsc_secm(css, 0) : 0;
 		break;
-	case '1':
+	case 1:
 		ret = css->cm_enabled ? 0 : chsc_secm(css, 1);
 		break;
 	default: