ipip6_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 ipip6_changelink() on rtnl_dev_link_net_capable() at its top, before any attribute is parsed. sit was the one tunnel type not covered by the recent series that added this check to the other changelink() handlers. Fixes: 5e6700b3bf98 ("sit: add support of x-netns") Link: https://lore.kernel.org/netdev/20260612085941.3158249-1-maoyixie.tju@gmail.com/ Cc: stable@vger.kernel.org Signed-off-by: Maoyi Xie --- net/ipv6/sit.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c index 64f0d1b..a38b24f 100644 --- a/net/ipv6/sit.c +++ b/net/ipv6/sit.c @@ -1613,6 +1613,9 @@ static int ipip6_changelink(struct net_device *dev, struct nlattr *tb[], __u32 fwmark = t->fwmark; int err; + if (!rtnl_dev_link_net_capable(dev, net)) + return -EPERM; + if (dev == sitn->fb_tunnel_dev) return -EINVAL; -- 2.43.0