[PATCH 4.14 14/89] tun: forbid iface creation with rtnl ops

From: Greg Kroah-Hartman
Date: Fri Dec 14 2018 - 07:07:47 EST

4.14-stable review patch. If anyone has any objections, please let me know.


From: Nicolas Dichtel <nicolas.dichtel@xxxxxxxxx>

[ Upstream commit 35b827b6d06199841a83839e8bb69c0cd13a28be ]

It's not supported right now (the goal of the initial patch was to support
'ip link del' only).

Before the patch:
$ ip link add foo type tun
[ 239.632660] BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
[ 239.636410] RIP: 0010:register_netdevice+0x8e/0x3a0

This panic occurs because dev->netdev_ops is not set by tun_setup(). But to
have something usable, it will require more than just setting

Fixes: f019a7a594d9 ("tun: Implement ip link del tunXXX")
CC: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
drivers/net/tun.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1818,9 +1818,9 @@ 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;
+ NL_SET_ERR_MSG(extack,
+ "tun/tap creation via rtnetlink is not supported.");
+ return -EOPNOTSUPP;

static struct rtnl_link_ops tun_link_ops __read_mostly = {