linux-kernel - [PATCH 3.16 086/305] tun: Consistently configure generic netdev params via rtnetlink

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Message-ID: <lsq.1549201508.691929041@decadent.org.uk>
Date:   Sun, 03 Feb 2019 14:45:08 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "David S. Miller" <davem@...emloft.net>,
        "Serhey Popovych" <serhe.popovych@...il.com>
Subject: [PATCH 3.16 086/305] tun: Consistently configure generic netdev
 params via rtnetlink

3.16.63-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Serhey Popovych <serhe.popovych@...il.com>

commit df52eab23d703142c766ac00bdb8db19d71238d0 upstream.

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@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/net/tun.c | 2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1415,6 +1415,8 @@ static void tun_setup(struct net_device
  */
 static int tun_validate(struct nlattr *tb[], struct nlattr *data[])
 {
+	if (!data)
+		return 0;
 	return -EINVAL;
 }