vti6_changelink() operates on at most two netns, dev_net(dev) and the tunnel link netns t->net. They differ once the device is created in or moved to a netns other than the one the request runs in. The rtnl changelink path checks CAP_NET_ADMIN only against dev_net(dev), so a caller privileged there but not in t->net can rewrite a tunnel that lives in t->net. Gate vti6_changelink() on rtnl_dev_link_net_capable() at its top, before any attribute is parsed. Reported-by: Xiao Liang Closes: https://lore.kernel.org/netdev/CABAhCOSzP1vaThGV35_VnsRCb=87_CPjPVsTHbq905k8A+BuUg@mail.gmail.com/ Fixes: 61220ab34948 ("vti6: Enable namespace changing") Cc: stable@vger.kernel.org Signed-off-by: Maoyi Xie Reviewed-by: Kuniyuki Iwashima --- net/ipv6/ip6_vti.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/ipv6/ip6_vti.c b/net/ipv6/ip6_vti.c index d871cab6938d..ab94b3a4ba9c 100644 --- a/net/ipv6/ip6_vti.c +++ b/net/ipv6/ip6_vti.c @@ -1046,6 +1046,9 @@ static int vti6_changelink(struct net_device *dev, struct nlattr *tb[], struct __ip6_tnl_parm p; struct vti6_net *ip6n; + if (!rtnl_dev_link_net_capable(dev, net)) + return -EPERM; + ip6n = net_generic(net, vti6_net_id); if (dev == ip6n->fb_tnl_dev) return -EINVAL; -- 2.34.1