ipip_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 ipip_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: 6c742e714d8c ("ipip: add x-netns support") Cc: stable@vger.kernel.org Signed-off-by: Maoyi Xie Reviewed-by: Kuniyuki Iwashima --- net/ipv4/ipip.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/ipv4/ipip.c b/net/ipv4/ipip.c index ff95b1b9908e..e7378569bd5b 100644 --- a/net/ipv4/ipip.c +++ b/net/ipv4/ipip.c @@ -494,6 +494,9 @@ static int ipip_changelink(struct net_device *dev, struct nlattr *tb[], bool collect_md; __u32 fwmark = t->fwmark; + if (!rtnl_dev_link_net_capable(dev, t->net)) + return -EPERM; + if (ip_tunnel_netlink_encap_parms(data, &ipencap)) { int err = ip_tunnel_encap_setup(t, &ipencap); -- 2.34.1