Re: [PATCH net-next] modules: allow modprobe load regular elf binaries

[Alexei Starovoitov]

On Fri, Mar 09, 2018 at 01:04:39AM +0000, Andy Lutomirski wrote:
> On Fri, Mar 9, 2018 at 12:57 AM, Alexei Starovoitov <ast@xxxxxx> wrote:
> > On 3/8/18 4:24 PM, Kees Cook wrote:
> >>
> >> As Andy asked earlier, why not DYN too to catch PIE executables? Seems
> >> like forcing the userspace helper to be non-PIE would defeat some of
> >> the userspace defenses in use in most distros.
> >
> >
> > because we don't add features without concrete users.
> 
> I disagree here.  If you're going to add a magic trick that triggers
> an execve(), then I think you should either support *both* standard,
> widely-used types of ELF programs or you should give a compelling use
> case that works for ET_EXEC but not for ET_DYN.  Keep in mind that
> many distros have a very strong preference for ET_DYN.

misunderstanding here is that this bpfiler.ko is part of _kernel build_.
Kernel decides how it's build.
Nothing to do with distros.
Current Makefile is very dumb and it's built with HOSTCC:
https://git.kernel.org/pub/scm/linux/kernel/git/ast/bpf.git/tree/net/bpfilter/Makefile?h=ipt_bpf
but it will be standalone with CC before final to make sure crosscompiling works.