Re: [PATCH net-next 2/2 v3] netns: restrict uevents

From: Eric W. Biederman
Date: Fri Apr 27 2018 - 12:30:44 EST


Christian Brauner <christian.brauner@xxxxxxxxxx> writes:
> ---
> lib/kobject_uevent.c | 140 ++++++++++++++++++++++++++++++-------------
> 1 file changed, 99 insertions(+), 41 deletions(-)
>
> diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c
> index c3cb110f663b..d8ce5e6d83af 100644
> --- a/lib/kobject_uevent.c
> +++ b/lib/kobject_uevent.c
>
> +static int uevent_net_broadcast_tagged(struct sock *usk,
> + struct kobj_uevent_env *env,
> + const char *action_string,
> + const char *devpath)
> +{
> + struct user_namespace *owning_user_ns = sock_net(usk)->user_ns;
> + struct sk_buff *skb = NULL;
> + int ret;
> +
> + skb = alloc_uevent_skb(env, action_string, devpath);
> + if (!skb)
> + return -ENOMEM;
> +
> + /* fix credentials */
> + if (owning_user_ns != &init_user_ns) {

Nit: This test is just a performance optimization as such is not
necessary. That is we can safely unconditionally set the
credentials this way.

> + struct netlink_skb_parms *parms = &NETLINK_CB(skb);
> + kuid_t root_uid;
> + kgid_t root_gid;
> +
> + /* fix uid */
> + root_uid = make_kuid(owning_user_ns, 0);
> + if (!uid_valid(root_uid))
> + root_uid = GLOBAL_ROOT_UID;
> + parms->creds.uid = root_uid;
> +
> + /* fix gid */
> + root_gid = make_kgid(owning_user_ns, 0);
> + if (!gid_valid(root_gid))
> + root_gid = GLOBAL_ROOT_GID;
> + parms->creds.gid = root_gid;
> + }
> +
> + ret = netlink_broadcast(usk, skb, 0, 1, GFP_KERNEL);
> + /* ENOBUFS should be handled in userspace */
> + if (ret == -ENOBUFS || ret == -ESRCH)
> + ret = 0;
> +
> + return ret;
> +}
> +#endif