Re: [RFC PATCH 09/11] kallsyms: hide layout and expose seed

Kees Cook
2020-02-27T16:02:43Z

On Thu, Feb 27, 2020 at 10:42:53AM +0800, Baoquan He wrote:
> On 02/06/20 at 09:51am, Kristen Carlson Accardi wrote:
> > On Thu, 2020-02-06 at 04:32 -0800, Kees Cook wrote:
>
> > > In the past, making kallsyms entirely unreadable seemed to break
> > > weird
> > > stuff in userspace. How about having an alternative view that just
> > > contains a alphanumeric sort of the symbol names (and they will
> > > continue
> > > to have zeroed addresses for unprivileged users)?
> > >
> > > Or perhaps we wait to hear about this causing a problem, and deal
> > > with
> > > it then? :)
> > >
> >
> > Yeah - I don't know what people want here. Clearly, we can't leave
> > kallsyms the way it is. Removing it entirely is a pretty fast way to
> > figure out how people use it though :).
>
> Kexec-tools and makedumpfile are the users of /proc/kallsyms currently.
> We use kallsyms to get page_offset_base and _stext.

AIUI, those run as root so they'd be able to consume the uncensored
output.

--
Kees Cook