From 11b326fb0a374f4654f9be22d0f0f7abd9f7d3fe Mon Sep 17 00:00:00 2001 From: Kuniyuki Iwashima Date: Thu, 21 May 2026 21:05:54 +0800 Subject: [PATCH] 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 61220ab34948 ("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: 61220ab34948 ("vti6: Enable namespace changing") Reported-by: Maoyi Xie Reviewed-by: Eric Dumazet Cc: stable@vger.kernel.org # v5.15+ Signed-off-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20260521130555.3421684-2-maoyixie.tju@gmail.com Signed-off-by: Paolo Abeni --- net/ipv6/ip6_vti.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/net/ipv6/ip6_vti.c b/net/ipv6/ip6_vti.c index ad5290be4dd6..dcb257411d6e 100644 --- a/net/ipv6/ip6_vti.c +++ b/net/ipv6/ip6_vti.c @@ -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;