Re: RFC: fsyscall

["Serge E. Hallyn" <serge@hallyn.com>]

On Thu, Sep 10, 2015 at 09:01:20AM -0500, Serge E. Hallyn wrote:
> On Thu, Sep 10, 2015 at 02:51:28PM +0100, David Drysdale wrote:
> > On Thu, Sep 10, 2015 at 2:43 PM, Serge E. Hallyn <serge@hallyn.com> wrote:
> > > On Tue, Sep 08, 2015 at 07:25:17PM -0500, Eric W. Biederman wrote:
> > >> Andy Lutomirski <luto@amacapital.net> writes:
> > >>
> > >> > On Tue, Sep 8, 2015 at 4:07 PM, Eric W. Biederman <ebiederm@xmission.com> wrote:
> > >>
> > >> >> Perhaps I had missed it but I don't recall capsicum being able to wrap
> > >> >> things like reboot(2).
> > >> >>
> > >> >
> > >> > Ah, so you want to be able to grant BPF-defined capabilities :)
> > >>
> > >> Pretty much.
> > >>
> > >> Where I am focusing is turning Posix capabilities into real
> > >> capabilities.  I would not mind if the functionality was a bit more
> > >> general.  Say to be able to handle things like security labels, or
> > >> anywhere else you might reasonably be asked can you do X?
> > >>
> > >> But I would be happy if we just managed to wrap the Posix capabilities
> > >> and turned them into real capablilities.
> > >
> > > If there were a clever way to exec an open fd, then you could do this
> > 
> > execveat(fd, "", argv, envp, AT_EMPTY_PATH) ?
> 
> ???  I looked for it but I don't have a manpage for it.  I see it at
> man7.org though.  Thanks :)

But this isn't quite what I was suggesting.  I was suggesting a call which
would exec the fd, not exec a file inside the dirfd.