Re: One for the Security Guru's

From: Eric W. Biederman (ebiederm@xmission.com)
Date: Thu Oct 24 2002 - 11:46:39 EST


Ville Herva <vherva@niksula.hut.fi> writes:

> On Wed, Oct 23, 2002 at 11:15:14PM +0100, you [James Stevenson] wrote:
> >
> > As to load a module you must be root and if you are root you
> > can read / write disks. Thus you could recompile your own kernel
> > install it try to force a crash or a reboot which is not hard as root
> > and the person may not even notice that the kernel has grown by a few
> > bytes after the crash.
>
> Which is why some people configure kernels not to support installing modules
> and only use read-only media (e.g. CD-R) for booting. Sure, there's still
> the /dev/kmem hole, but this closes 2 classes of attacks - loading rootkit
> module and booting with a hacked kernel in straight-forward way.
>
> BTW, this might be a reason to make kexec syscall to be a config option (if
> it isn't already.)

It already is a config option.

Eric
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