[PATCH 3.11 224/233] sit: fix double free of fb_tunnel_dev on exit

From: Luis Henriques
Date: Fri Feb 07 2014 - 06:56:44 EST -stable review patch. If anyone has any objections, please let me know.


From: Nicolas Dichtel <nicolas.dichtel@xxxxxxxxx>

[ No relevant upstream commit. ]

This problem was fixed upstream by commit 9434266f2c64 ("sit: fix use after free
of fb_tunnel_dev").
The upstream patch depends on upstream commit 5e6700b3bf98 ("sit: add support of
x-netns"), which was not backported into 3.10 branch.

First, explain the problem: when the sit module is unloaded, sit_cleanup() is
rmmod sit
=> sit_cleanup()
=> rtnl_link_unregister()
=> __rtnl_kill_links()
=> for_each_netdev(net, dev) {
if (dev->rtnl_link_ops == ops)
ops->dellink(dev, &list_kill);
At this point, the FB device is deleted (and all sit tunnels).
=> unregister_pernet_device()
=> unregister_pernet_operations()
=> ops_exit_list()
=> sit_exit_net()
=> sit_destroy_tunnels()
In this function, no tunnel is found.
=> unregister_netdevice_queue(sitn->fb_tunnel_dev, &list);
We delete the FB device a second time here!

Because we cannot simply remove the second deletion (sit_exit_net() must remove
the FB device when a netns is deleted), we add an rtnl ops which delete all sit
device excepting the FB device and thus we can keep the explicit deletion in

CC: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@xxxxxxxxx>
Acked-by: Willem de Bruijn <willemb@xxxxxxxxxx>
Reported-by: Steven Rostedt <srostedt@xxxxxxxxxx>
Tested-by: Steven Rostedt <srostedt@xxxxxxxxxx> (and our entire MRG team)
Tested-by: "Luis Claudio R. Goncalves" <lgoncalv@xxxxxxxxxx>
Tested-by: John Kacur <jkacur@xxxxxxxxxx>
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
net/ipv6/sit.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
index a51ad07..bbe1402 100644
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -1601,6 +1601,15 @@ static const struct nla_policy ipip6_policy[IFLA_IPTUN_MAX + 1] = {

+static void ipip6_dellink(struct net_device *dev, struct list_head *head)
+ struct net *net = dev_net(dev);
+ struct sit_net *sitn = net_generic(net, sit_net_id);
+ if (dev != sitn->fb_tunnel_dev)
+ unregister_netdevice_queue(dev, head);
static struct rtnl_link_ops sit_link_ops __read_mostly = {
.kind = "sit",
.maxtype = IFLA_IPTUN_MAX,
@@ -1612,6 +1621,7 @@ static struct rtnl_link_ops sit_link_ops __read_mostly = {
.changelink = ipip6_changelink,
.get_size = ipip6_get_size,
.fill_info = ipip6_fill_info,
+ .dellink = ipip6_dellink,

static struct xfrm_tunnel sit_handler __read_mostly = {

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/