Re: [PATCH net-next 2/2 v4] netns: restrict uevents

Eric W. Biederman
2018-04-29T04:23:58Z

> + /* fix credentials */
> + if (owning_user_ns != &init_user_ns) {
> + 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;

One last nit:

You can only make the assignment if the uid is valid.
Leaving it GLBOAL_ROOT_UID if the composed uid is invalid.
AKA

/* fix uid */
root_uid = make_kuid(owning_user_ns, 0);
if (uid_valid(root_uid))
parms->creds.uid = root_uid;

/* fix gid */
root_gid = make_kgid(owning_user_ns, 0);
if (gid_valid(root_gid))
params->creds.gid = root_gid;

One line shorter and I think a little clearer. I suspect
it even results in better code.

Eric