Re: [RFC][PATCH] Randomize kernel base address on boot

Vivek Goyal
2011-05-26T20:56:18Z

On Thu, May 26, 2011 at 04:44:34PM -0400, Dan Rosenberg wrote:
> On Thu, 2011-05-26 at 16:40 -0400, Vivek Goyal wrote:
> > On Thu, May 26, 2011 at 04:35:02PM -0400, Vivek Goyal wrote:
> > > On Tue, May 24, 2011 at 04:31:45PM -0400, Dan Rosenberg wrote:
> > > > This introduces CONFIG_RANDOMIZE_BASE, which randomizes the address at
> > > > which the kernel is decompressed at boot as a security feature that
> > > > deters exploit attempts relying on knowledge of the location of kernel
> > > > internals. The default values of the kptr_restrict and dmesg_restrict
> > > > sysctls are set to (1) when this is enabled, since hiding kernel
> > > > pointers is necessary to preserve the secrecy of the randomized base
> > > > address.
> > >
> > > What happens to /proc/iomem interface which gives us the physical memory
> > > location where kernel is loaded. kexec-tools relies on that interface
> > > heavily so we can not take it away. And if we can not take it away then
> > > I think somebody should be easibly be able to calculate this randomized
> > > base address.
>
> Is it common to run kexec-tools as non-root? It may be necessary to
> restrict this interface to root when randomization is used (keep in mind
> nobody's going to force you to turn this on by default, at least for the
> foreseeable future).

kexec-tools runs as root. And I see that /proc/iomem permissions are
also for root only. So it probably is a non-issue.

Thanks
Vivek