[PATCH AUTOSEL 4.9 05/48] tun: Consistently configure generic netdev params via rtnetlink

From: Sasha Levin
Date: Wed Oct 31 2018 - 19:21:58 EST

From: Serhey Popovych <serhe.popovych@xxxxxxxxx>

[ Upstream commit df52eab23d703142c766ac00bdb8db19d71238d0 ]

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@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
drivers/net/tun.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index eb6dc28e5e52..0260bc15bc0c 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1570,6 +1570,8 @@ static void tun_setup(struct net_device *dev)
static int tun_validate(struct nlattr *tb[], struct nlattr *data[])
+ if (!data)
+ return 0;
return -EINVAL;