On Thu, Jun 20, 2019 at 10:22 PM Andy Lutomirski <luto@xxxxxxxxxx> wrote:
> On Thu, Jun 20, 2019 at 6:21 PM Matthew Garrett
> <matthewgarrett@xxxxxxxxxx> wrote:
> > --- a/security/lockdown/lockdown.c
> > +++ b/security/lockdown/lockdown.c
> > @@ -33,6 +33,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = {
> > [LOCKDOWN_INTEGRITY_MAX] = "integrity",
> > [LOCKDOWN_KCORE] = "/proc/kcore access",
> > [LOCKDOWN_KPROBES] = "use of kprobes",
> > + [LOCKDOWN_BPF] = "use of bpf",
> > [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality",
>
> The text here says "use of bpf", but what this patch is *really* doing
> is locking down use of BPF to read kernel memory. If the details
> change, then every LSM needs to get updated, and we risk breaking user
> policies that are based on LSMs that offer excessively fine
> granularity.
The text is descriptive rather than normative, and no changes should
be made that alter the semantics of a reason - it makes more sense to
just add another reason.
> I'd be more comfortable if the LSM only got to see "confidentiality"
> or "integrity".
If LSM authors can be trusted to do the right thing here, then I see
no problem in providing additional data. I'm happy to defer to James
on that.
