David Howells <dhowe...@redhat.com> wrote:

> >     int (*capable) (struct task_struct *tsk, const struct cred *cred,
> > -                   int cap, int audit);
> > +                   struct user_namespace *ns, int cap, int audit);
> 
> Hmmm...  A chunk of the contents of the cred struct are user-namespaced.
> Could you add the user_namespace pointer to the cred struct and thus avoid
> passing it as an argument to other things.

Ah, no...  Ignore that, I think I see that you do need it.

> +int cap_capable(struct task_struct *tsk, const struct cred *cred,
> +             struct user_namespace *targ_ns, int cap, int audit)
>  {
> -     return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
> +     for (;;) {
> +             /* The creator of the user namespace has all caps. */
> +             if (targ_ns != &init_user_ns && targ_ns->creator == cred->user)
> +                     return 0;

Why is that last comment so?  Why should the creating namespace sport all
possible capabilities?  Do you have to have all capabilities available to you
to be permitted create a new user namespace?

Also, would it be worth having a separate cap_ns_capable()?  Wouldn't most
calls to cap_capable() only be checking the caps granted in the current user
namespace?

David
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