Re: [PATCH 02/10] userns: Add per user namespace sysctls.

["Serge E. Hallyn" <serge-A9i7LUbDfNHQT0dZR+AlfA@public.gmane.org>]

Quoting Eric W. Biederman (ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org):
> "Serge E. Hallyn" <serge-A9i7LUbDfNHQT0dZR+AlfA@public.gmane.org> writes:
> 
> > Quoting Eric W. Biederman (ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org):
> >> "Serge E. Hallyn" <serge-A9i7LUbDfNHQT0dZR+AlfA@public.gmane.org> writes:
> >> 
> >> > Quoting Eric W. Biederman (ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org):
> >> >> +static bool setup_userns_sysctls(struct user_namespace *ns)
> >> >> +{
> >> >> +#ifdef CONFIG_SYSCTL
> >> >> +	struct ctl_table *tbl;
> >> >> +	setup_sysctl_set(&ns->set, &set_root, set_is_seen);
> >> >> +	tbl = kmemdup(userns_table, sizeof(userns_table), GFP_KERNEL);
> >> >> +	if (tbl) {
> >> >> +		ns->sysctls = __register_sysctl_table(&ns->set, "userns", tbl);
> >> >> +	}
> >> >
> >> > What happens if tbl is null due to oom?  Would it be better to just
> >> > return false in that case here?
> >> 
> >> ns->sysctls is initialized to NULL and kfree(NULL) is a noop.
> >> So I don't see any problems.
> >> 
> >> I admit it isn't a usual pattern for error handling.
> >
> > Right I didn't mean that - I meant, is there a way that a namespace
> > could end up escaping its limits as a result?  I think not, since
> > either it has hierarchical limits which will still be enforced, or
> > the admin tries to set a new limit and that step will fail visibly,
> > which suffices.
> 
> And what I meant is that we do actually return false in the case you are
> worrying about.  And if we return false we don't even create the user
> namespace.

D'oh.  Right.  Thanks :)