Re: [PATCH bpf-next 1/6] bpf: introduce BPF_PROG_TYPE_FILE_FILTER

[Alexei Starovoitov]

On Fri, Oct 05, 2018 at 03:09:20PM -0700, Andy Lutomirski wrote:
> On Fri, Oct 5, 2018 at 3:05 PM Alexei Starovoitov
> <alexei.starovoitov@xxxxxxxxx> wrote:
> >
> > On Fri, Oct 05, 2018 at 05:46:59AM +0100, Al Viro wrote:
> >
> > > Another problem is your direct poking in ->i_ino.  It's not
> > > something directly exposed to userland at the moment and it should
> > > not become such.
> >
> > The patch is not making i_ino directly exposed.
> > Only 'struct bpf_file_info' is exposed to user space / bpf programs.
> 
> I think Al is saying that the valie of i_ino is not something that
> user code is permitted to know regardless of how you format it because
> it may or may not actually match the value returned by stat().
> Another way of saying that is that your patch is digging into an
> internal data structure and is doing it wrong.

several fs implementation I've looked at just do generic_fillattr()
for these fields. Are you saying some FS don't use inode->i_ino at all?
And it's bogus, hence shouldn't be read?