net: tun: Convert to use sysfs_emit() APIs

Follow the advice of the Documentation/filesystems/sysfs.rst and show()
should only use sysfs_emit() or sysfs_emit_at() when formatting the value
to be returned to user space.
Signed-off-by: Wang Yufen <wangyufen@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/tun.c

@@ -2664,7 +2664,7 @@ static ssize_t tun_flags_show(struct device *dev, struct device_attribute *attr,
 			      char *buf)
 {
 	struct tun_struct *tun = netdev_priv(to_net_dev(dev));
-	return sprintf(buf, "0x%x\n", tun_flags(tun));
+	return sysfs_emit(buf, "0x%x\n", tun_flags(tun));
 }
 
 static ssize_t owner_show(struct device *dev, struct device_attribute *attr,
@@ -2672,9 +2672,9 @@ static ssize_t owner_show(struct device *dev, struct device_attribute *attr,
 {
 	struct tun_struct *tun = netdev_priv(to_net_dev(dev));
 	return uid_valid(tun->owner)?
-		sprintf(buf, "%u\n",
-			from_kuid_munged(current_user_ns(), tun->owner)):
-		sprintf(buf, "-1\n");
+		sysfs_emit(buf, "%u\n",
+			   from_kuid_munged(current_user_ns(), tun->owner)) :
+		sysfs_emit(buf, "-1\n");
 }
 
 static ssize_t group_show(struct device *dev, struct device_attribute *attr,
@@ -2682,9 +2682,9 @@ static ssize_t group_show(struct device *dev, struct device_attribute *attr,
 {
 	struct tun_struct *tun = netdev_priv(to_net_dev(dev));
 	return gid_valid(tun->group) ?
-		sprintf(buf, "%u\n",
-			from_kgid_munged(current_user_ns(), tun->group)):
-		sprintf(buf, "-1\n");
+		sysfs_emit(buf, "%u\n",
+			   from_kgid_munged(current_user_ns(), tun->group)) :
+		sysfs_emit(buf, "-1\n");
 }
 
 static DEVICE_ATTR_RO(tun_flags);