Re: Is PIE randomization breaking klibc binaries?

H. Peter Anvin
2007-07-20T22:06:18Z

Ulrich Kunitz wrote:
> Since this week new linux-2.6/master kernels don't work with my
> initial ram disks. The sleep binary runs repeatingly into
> segmentation faults until the Busybox shell starts. My system is a
> x86-64 with Kubuntu Feisty Fawn.
>
> By bisecting I found out that the PIE randomization patch (commit 60bfba7e)
> appears to cause the segmentation faults.
>
> Digging further into the issue I found out, that the sleep binary
> on the initial ramdisk is a klibc binary. /usr/bin/file says it is
> statically linked and uses shared libraries. I have no clue about
> klibc, but the binaries seem to be statically linked, but load a
> shared library; probably at a fixed address. Other klibc binaries are also
> running into segmentation faults. Busybox is working, but it is
> statically linked and doesn't use a shared library.
>
> It looks like that the PIE randomization patch breaks klibc
> binaries on x86-64.
>

Interesting.

klibc binaries are indeed statically linked, but composed of two
different ELF images: the application itself and the shared libary
(which is referenced from the application header as the "interpreter").
Neither of these is an ET_DYN file; they are both ET_EXEC, so it
*should* be unaffected by the PIE randomization patch. Obviously, that
seems to not be the case.

My guess is that this patch mishandles interpreter images which are
ET_EXEC. Jan, any insight?

-hpa