From df52eab23d703142c766ac00bdb8db19d71238d0 Mon Sep 17 00:00:00 2001
From: Serhey Popovych <serhe.popovych@gmail.com>
Date: Tue, 9 Oct 2018 21:21:01 +0300
Subject: [PATCH] tun: Consistently configure generic netdev params via rtnetlink
Git-commit: df52eab23d703142c766ac00bdb8db19d71238d0
Patch-mainline: v4.20-rc1
References: bsc#1051510

Configuring generic network device parameters on tun will fail in
presence of IFLA_INFO_KIND attribute in IFLA_LINKINFO nested attribute
since tun_validate() always return failure.

This can be visualized with following ip-link(8) command sequences:

  # ip link set dev tun0 group 100
  # ip link set dev tun0 group 100 type tun
  RTNETLINK answers: Invalid argument

with contrast to dummy and veth drivers:

  # ip link set dev dummy0 group 100
  # ip link set dev dummy0 type dummy

  # ip link set dev veth0 group 100
  # ip link set dev veth0 group 100 type veth

Fix by returning zero in tun_validate() when @data is NULL that is
always in case since rtnl_link_ops->maxtype is zero in tun driver.

Fixes: f019a7a594d9 ("tun: Implement ip link del tunXXX")
Signed-off-by: Serhey Popovych <serhe.popovych@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/net/tun.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -2290,6 +2290,8 @@ static void tun_setup(struct net_device
 static int tun_validate(struct nlattr *tb[], struct nlattr *data[],
 			struct netlink_ext_ack *extack)
 {
+	if (!data)
+		return 0;
 	return -EINVAL;
 }