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This allows an unprivileged user with a user namespace to create interfaces in arbitrary network namespaces, including init_net. Add a netlink_ns_capable() check for CAP_NET_ADMIN in the peer namespace before allowing device creation to proceed. Fixes: 81adee47dfb6 ("net: Support specifying the network namespace upon device creation.") Signed-off-by: Nikolaos Gkarlis --- v5: - Rework rtnl_get_peer_net() to explicitly handle early exit for clarity (suggested by Jakub Kicinski) v4: - Use IS_ERR_OR_NULL instead of IS_ERR + null check. v3: - Move netlink_ns_capable() check from rtnl_newlink() into rtnl_get_peer_net(), after the last rtnl_link_get_net_ifla(tb) call. The tbp path is already covered by rtnl_link_get_net_capable() in the caller. (suggested by Kuniyuki) - Pass skb to rtnl_get_peer_net() for the capability check. - Add IS_ERR() check on rtnl_link_get_net_ifla(tb) return value. v2: - Removed "Reported-by" tag - Fixed "Fixes" tag with the help of Kuniyuki Iwashima (thanks !) net/core/rtnetlink.c | 40 +++++++++++++++++++++++++++------------- 1 file changed, 27 insertions(+), 13 deletions(-) diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c index fae8034efbf..69daba3ddaf 100644 --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -3894,28 +3894,42 @@ static int rtnl_newlink_create(struct sk_buff *skb, struct ifinfomsg *ifm, goto out; } -static struct net *rtnl_get_peer_net(const struct rtnl_link_ops *ops, +static struct net *rtnl_get_peer_net(struct sk_buff *skb, + const struct rtnl_link_ops *ops, struct nlattr *tbp[], struct nlattr *data[], struct netlink_ext_ack *extack) { - struct nlattr *tb[IFLA_MAX + 1]; + struct nlattr *tb[IFLA_MAX + 1], **attrs; + struct net *net; int err; - if (!data || !data[ops->peer_type]) - return rtnl_link_get_net_ifla(tbp); - - err = rtnl_nla_parse_ifinfomsg(tb, data[ops->peer_type], extack); - if (err < 0) - return ERR_PTR(err); - - if (ops->validate) { - err = ops->validate(tb, NULL, extack); + if (!data || !data[ops->peer_type]) { + attrs = tbp; + } else { + err = rtnl_nla_parse_ifinfomsg(tb, data[ops->peer_type], extack); if (err < 0) return ERR_PTR(err); + + if (ops->validate) { + err = ops->validate(tb, NULL, extack); + if (err < 0) + return ERR_PTR(err); + } + + attrs = tb; } - return rtnl_link_get_net_ifla(tb); + net = rtnl_link_get_net_ifla(attrs); + if (IS_ERR_OR_NULL(net)) + return net; + + if (!netlink_ns_capable(skb, net->user_ns, CAP_NET_ADMIN)) { + put_net(net); + return ERR_PTR(-EPERM); + } + + return net; } static int __rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh, @@ -4054,7 +4068,7 @@ static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh, } if (ops->peer_type) { - peer_net = rtnl_get_peer_net(ops, tb, data, extack); + peer_net = rtnl_get_peer_net(skb, ops, tb, data, extack); if (IS_ERR(peer_net)) { ret = PTR_ERR(peer_net); goto put_ops; -- 2.34.1