A tunnel 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. Add rtnl_dev_link_net_capable() next to rtnl_get_net_ns_capable() in net/core/rtnetlink.c. It requires CAP_NET_ADMIN in the link netns and is skipped when the link netns is dev_net(dev), where the rtnl path already checked it. The other patches in this series use the same helper. Gate ipgre_changelink() and erspan_changelink() with it, at the top of the op before any attribute is parsed, because the parsers update live tunnel fields first. ipgre_netlink_parms() sets t->collect_md before ip_tunnel_changelink() runs. Commit 8b484efd5cb4 ("ip6: vti: Use ip6_tnl.net in vti6_siocdevprivate().") added the same check on the ioctl path. This adds it on RTM_NEWLINK. Reported-by: Xiao Liang Closes: https://lore.kernel.org/netdev/CABAhCOSzP1vaThGV35_VnsRCb=87_CPjPVsTHbq905k8A+BuUg@mail.gmail.com/ Fixes: b57708add314 ("gre: add x-netns support") Cc: stable@vger.kernel.org Signed-off-by: Maoyi Xie Reviewed-by: Kuniyuki Iwashima --- include/net/rtnetlink.h | 2 ++ net/core/rtnetlink.c | 8 ++++++++ net/ipv4/ip_gre.c | 6 ++++++ 3 files changed, 16 insertions(+) diff --git a/include/net/rtnetlink.h b/include/net/rtnetlink.h index ec65a8cebb99..2bff41aacc98 100644 --- a/include/net/rtnetlink.h +++ b/include/net/rtnetlink.h @@ -256,6 +256,8 @@ int rtnl_configure_link(struct net_device *dev, const struct ifinfomsg *ifm, int rtnl_nla_parse_ifinfomsg(struct nlattr **tb, const struct nlattr *nla_peer, struct netlink_ext_ack *exterr); struct net *rtnl_get_net_ns_capable(struct sock *sk, int netnsid); +bool rtnl_dev_link_net_capable(const struct net_device *dev, + const struct net *link_net); #define MODULE_ALIAS_RTNL_LINK(kind) MODULE_ALIAS("rtnl-link-" kind) diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c index 511c25bf6f2a..3be5f264f5ad 100644 --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -2421,6 +2421,14 @@ struct net *rtnl_get_net_ns_capable(struct sock *sk, int netnsid) } EXPORT_SYMBOL_GPL(rtnl_get_net_ns_capable); +bool rtnl_dev_link_net_capable(const struct net_device *dev, + const struct net *link_net) +{ + return net_eq(link_net, dev_net(dev)) || + ns_capable(link_net->user_ns, CAP_NET_ADMIN); +} +EXPORT_SYMBOL_GPL(rtnl_dev_link_net_capable); + static int rtnl_valid_dump_ifinfo_req(const struct nlmsghdr *nlh, bool strict_check, struct nlattr **tb, struct netlink_ext_ack *extack) diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c index 169e2921a851..0ebed1438f6c 100644 --- a/net/ipv4/ip_gre.c +++ b/net/ipv4/ip_gre.c @@ -1457,6 +1457,9 @@ static int ipgre_changelink(struct net_device *dev, struct nlattr *tb[], __u32 fwmark = t->fwmark; int err; + if (!rtnl_dev_link_net_capable(dev, t->net)) + return -EPERM; + err = ipgre_newlink_encap_setup(dev, data); if (err) return err; @@ -1486,6 +1489,9 @@ static int erspan_changelink(struct net_device *dev, struct nlattr *tb[], __u32 fwmark = t->fwmark; int err; + if (!rtnl_dev_link_net_capable(dev, t->net)) + return -EPERM; + err = ipgre_newlink_encap_setup(dev, data); if (err) return err; -- 2.34.1