[PATCH net v5 7/7] xfrm: xfrm_interface: require CAP_NET_ADMIN in the device netns for changelink

[Maoyi Xie]

xfrmi_changelink() operates on at most two netns, dev_net(dev) and the
interface link netns xi->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 xi->net can rewrite an interface that
lives in xi->net.

Gate xfrmi_changelink() on rtnl_dev_link_net_capable() at its top,
before any attribute is parsed.

Reported-by: Xiao Liang <shaw.leon@xxxxxxxxx>
Closes: https://lore.kernel.org/netdev/CABAhCOSzP1vaThGV35_VnsRCb=87_CPjPVsTHbq905k8A+BuUg@xxxxxxxxxxxxxx/
Fixes: f203b76d7809 ("xfrm: Add virtual xfrm interfaces")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Maoyi Xie <maoyixie.tju@xxxxxxxxx>
---
 net/xfrm/xfrm_interface_core.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/xfrm/xfrm_interface_core.c b/net/xfrm/xfrm_interface_core.c
index 330a05286a56..688306bf62c5 100644
--- a/net/xfrm/xfrm_interface_core.c
+++ b/net/xfrm/xfrm_interface_core.c
@@ -869,6 +869,9 @@ static int xfrmi_changelink(struct net_device *dev, struct nlattr *tb[],
 	struct net *net = xi->net;
 	struct xfrm_if_parms p = {};
 
+	if (!rtnl_dev_link_net_capable(dev, net))
+		return -EPERM;
+
 	xfrmi_netlink_parms(data, &p);
 	if (!p.if_id) {
 		NL_SET_ERR_MSG(extack, "if_id must be non zero");
-- 
2.34.1