Commit 11b326fb authored by Kuniyuki Iwashima's avatar Kuniyuki Iwashima Committed by Paolo Abeni
Browse files

ip6: vti: Use ip6_tnl.net in vti6_changelink(). 



ip netns add ns1
ip netns add ns2
ip -n ns1 link add vti6_test type vti6 remote ::1 local ::2 key 7
ip -n ns1 link set vti6_test netns ns2
ip -n ns2 link set vti6_test type vti6 remote ::3 local ::4 key 9
ip netns del ns2
ip netns del ns1
[  132.495484] ------------[ cut here ]------------
[  132.497609] kernel BUG at net/core/dev.c:12376!

Commit 61220ab3 ("vti6: Enable namespace changing") dropped
NETIF_F_NETNS_LOCAL from vti6 devices. A vti6 tunnel can then
move through IFLA_NET_NS_FD. After the move dev_net(dev) points
at the new netns while t->net stays at the creation netns.

vti6_changelink() and vti6_update() still use dev_net(dev) and
dev_net(t->dev). They unlink from one per netns hash and relink
into another. The creation netns is left with a stale entry.
cleanup_net() of that netns later walks freed memory.

Reachable from an unprivileged user namespace (unshare --user
--map-root-user --net). Cross tenant scope on container hosts.

Fixes: 61220ab3 ("vti6: Enable namespace changing")
Reported-by: default avatarMaoyi Xie <maoyi.xie@ntu.edu.sg>
Reviewed-by: default avatarEric Dumazet <edumazet@google.com>
Cc: stable@vger.kernel.org # v5.15+
Signed-off-by: default avatarKuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20260521130555.3421684-2-maoyixie.tju@gmail.com


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent 25fe708b

net/ipv6/ip6_vti.c

+7 −5
Original line number Diff line number Diff line
@@ -722,10 +722,11 @@ vti6_tnl_change(struct ip6_tnl *t, const struct __ip6_tnl_parm *p, 
static int vti6_update(struct ip6_tnl *t, struct __ip6_tnl_parm *p,

		       bool keep_mtu)

{

	struct net *net = dev_net(t->dev);

	struct vti6_net *ip6n = net_generic(net, vti6_net_id);

	struct net *net = t->net;

	struct vti6_net *ip6n;

	int err;



	ip6n = net_generic(net, vti6_net_id);

	vti6_tnl_unlink(ip6n, t);

	synchronize_net();

	err = vti6_tnl_change(t, p, keep_mtu);
@@ -1031,11 +1032,12 @@ static int vti6_changelink(struct net_device *dev, struct nlattr *tb[], 
			   struct nlattr *data[],

			   struct netlink_ext_ack *extack)

{

	struct ip6_tnl *t;

	struct ip6_tnl *t = netdev_priv(dev);

	struct net *net = t->net;

	struct __ip6_tnl_parm p;

	struct net *net = dev_net(dev);

	struct vti6_net *ip6n = net_generic(net, vti6_net_id);

	struct vti6_net *ip6n;



	ip6n = net_generic(net, vti6_net_id);

	if (dev == ip6n->fb_tnl_dev)

		return -EINVAL;