mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-08-30 12:13:51 -04:00
ed267f783c
l2tp_tunnel_notify() and l2tp_session_notify() use genlmsg_multicast_allns(), which delivers to listeners in every network namespace. l2tp is per-namespace, and a tunnel records the namespace it belongs to in tunnel->l2tp_net. Each event concerns one namespace, yet every namespace is told about it. A tunnel event carries the tunnel and peer tunnel ids, plus the socket's addresses with both ports for a UDP tunnel. A session event carries the session and peer session ids, the interface name, plus the L2TP cookies where those are set. A listener needs no privilege for any of this, because l2tp_multicast_group[] carries no flags and genl_bind() asks for no capability. The fix is to send to the tunnel's namespace with genlmsg_multicast_netns(). Commit134e63756d("genetlink: make netns aware") added both helpers and drew the line between them. The netns variant is for an object that lives in a namespace. I found this by auditing the tree's six genlmsg_multicast_allns() call sites for objects that live in a network namespace. Only the two l2tp ones do. I reproduced it on net atdd057113ac, in a virtual machine, with no real hardware involved. A process in the initial namespace, running as an ordinary user with an empty capability set, receives the create and delete events of a tunnel. The tunnel was set up inside an unprivileged user and network namespace. tools/testing/selftests/net/l2tp.sh passes before and after. On a container host, any local user and every other tenant can read a tenant's tunnel parameters. Cc: stable+noautosel@kernel.org # high regression risk Signed-off-by: Maoyi Xie <maoyixie.tju@gmail.com> Reviewed-by: Simon Horman <horms@kernel.org> Link: https://patch.msgid.link/20260809094252.2107242-1-maoyixie.tju@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>