Re: Kdump with signed images

Vivek Goyal
2012-11-06T19:34:32Z

On Mon, Nov 05, 2012 at 11:44:48AM -0800, Eric W. Biederman wrote:
> Vivek Goyal <vgoyal@redhat.com> writes:
>
> > On Fri, Nov 02, 2012 at 02:32:48PM -0700, Eric W. Biederman wrote:
> >>
> >> It needs to be checked but /sbin/kexec should not use any functions that
> >> trigger nss switch. No user or password or host name lookup should be
> >> happening.
> >
> > I also think that we don't call routines which trigger nss switch but
> > be probably can't rely on that as somebody might introduce it in
> > future. So we need more robust mechanism to prevent it than just code
> > inspection.
>
> The fact that we shouldn't use those routines is enough to let us
> walk down a path where they are not used. Either with a static glibc
> linked told to use no nss modules (--enable-static-nss ?), or with
> another more restricted libc.

I installed glibc-static and built kexec-tools using gcc "-static" option.
It built just fine and infact kdump is working with it.

Size of new kexec binary is around 1.4MB.

Did not get any warning w.r.t nss, so I am assuming we are not calling
any relevant functions.

I did try building my own libc using --enable-static-nss but it does not
seem to have built static versions of libnss*. Will look more into it
and try linking kexec with this new glibc and see if that works.

Also tried playing with klibc and uclibc a bit but can't get anything
going quickly.

Thanks
Vivek