RE: [PATCH v6 1/3] x86/speculation: apply IBPB more strictly to avoid cross-process data leak

[Thomas Gleixner]

On Fri, 14 Sep 2018, Jiri Kosina wrote:
> On Thu, 13 Sep 2018, Schaufler, Casey wrote:
> 
> > > -	return security_ptrace_access_check(task, mode);
> > > +	if (!(mode & PTRACE_MODE_NOACCESS_CHK))
> > > +		return security_ptrace_access_check(task, mode);
> > > +	return 0;
> > 
> > Because PTRACE_MODE_IBPB includes PTRACE_MODE_NOAUDIT you
> > shouldn't need this change. 
> 
> That is true, but that's not my concern here. 
> 
> 	security_ptrace_access_check() -> call_int_hook() -> P->hook.FUNC().
> 
> If it's somehow guaranteed that all functions called this ways are fine to 
> be called from scheduler context (wrt. locks), then it's all fine and I'll 
> happily drop that check.
> 
> Is it guaranteed?

The related question is whether it is guaranteed for backports. We don't
want to end up with a separate hell there.

Thanks,

	tglx