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

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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 61220ab349 ("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: 61220ab349 ("vti6: Enable namespace changing")
Reported-by: Maoyi Xie <maoyi.xie@ntu.edu.sg>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Cc: stable@vger.kernel.org # v5.15+
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20260521130555.3421684-2-maoyixie.tju@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Kuniyuki Iwashima 2026-05-21 21:05:54 +08:00 committed by Paolo Abeni
parent 25fe708bbc
commit 11b326fb0a
1 changed files with 7 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
net/ipv6/ip6_vti.c
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@ -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;