[PATCH net-next 3/3 V1] rtnetlink: enable IFLA_IF_NETNSID for RTM_DELLINK

From: Christian Brauner
Date: Wed Jan 24 2018 - 09:26:57 EST


- Backwards Compatibility:
If userspace wants to determine whether RTM_DELLINK supports the
IFLA_IF_NETNSID property they should first send an RTM_GETLINK request
with IFLA_IF_NETNSID on lo. If either EACCESS is returned or the reply
does not include IFLA_IF_NETNSID userspace should assume that
IFLA_IF_NETNSID is not supported on this kernel.
If the reply does contain an IFLA_IF_NETNSID property userspace
can send an RTM_DELLINK with a IFLA_IF_NETNSID property. If they receive
EOPNOTSUPP then the kernel does not support the IFLA_IF_NETNSID property
with RTM_DELLINK. Userpace should then fallback to other means.

- Security:
Callers must have CAP_NET_ADMIN in the owning user namespace of the
target network namespace.

Signed-off-by: Christian Brauner <christian.brauner@xxxxxxxxxx>
---
Changelog 2018-01-24:
* Preserve old behavior and report -ENODEV when either ifindex or ifname is
provided and IFLA_GROUP is set. Spotted by Wolfgang Bumiller.
---
net/core/rtnetlink.c | 39 ++++++++++++++++++++++++++++-----------
1 file changed, 28 insertions(+), 11 deletions(-)

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index a4d4409685e3..fdb9e8777abb 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -2630,36 +2630,53 @@ static int rtnl_dellink(struct sk_buff *skb, struct nlmsghdr *nlh,
struct netlink_ext_ack *extack)
{
struct net *net = sock_net(skb->sk);
- struct net_device *dev;
+ struct net *tgt_net = net;
+ struct net_device *dev = NULL;
struct ifinfomsg *ifm;
char ifname[IFNAMSIZ];
struct nlattr *tb[IFLA_MAX+1];
int err;
+ int netnsid = -1;

err = nlmsg_parse(nlh, sizeof(*ifm), tb, IFLA_MAX, ifla_policy, extack);
if (err < 0)
return err;

- if (tb[IFLA_IF_NETNSID])
- return -EOPNOTSUPP;
-
if (tb[IFLA_IFNAME])
nla_strlcpy(ifname, tb[IFLA_IFNAME], IFNAMSIZ);

+ if (tb[IFLA_IF_NETNSID]) {
+ netnsid = nla_get_s32(tb[IFLA_IF_NETNSID]);
+ tgt_net = get_target_net(NETLINK_CB(skb).sk, netnsid);
+ if (IS_ERR(tgt_net))
+ return PTR_ERR(tgt_net);
+ }
+
+ err = -EINVAL;
ifm = nlmsg_data(nlh);
if (ifm->ifi_index > 0)
- dev = __dev_get_by_index(net, ifm->ifi_index);
+ dev = __dev_get_by_index(tgt_net, ifm->ifi_index);
else if (tb[IFLA_IFNAME])
- dev = __dev_get_by_name(net, ifname);
+ dev = __dev_get_by_name(tgt_net, ifname);
else if (tb[IFLA_GROUP])
- return rtnl_group_dellink(net, nla_get_u32(tb[IFLA_GROUP]));
+ err = rtnl_group_dellink(tgt_net, nla_get_u32(tb[IFLA_GROUP]));
else
- return -EINVAL;
+ goto out;

- if (!dev)
- return -ENODEV;
+ if (!dev) {
+ if (tb[IFLA_IFNAME] || ifm->ifi_index > 0)
+ err = -ENODEV;

- return rtnl_delete_link(dev);
+ goto out;
+ }
+
+ err = rtnl_delete_link(dev);
+
+out:
+ if (netnsid >= 0)
+ put_net(tgt_net);
+
+ return err;
}

int rtnl_configure_link(struct net_device *dev, const struct ifinfomsg *ifm)
--
2.14.1