Re: NFS4 authentification / fsuid

J. Bruce Fields
2007-09-06T15:06:37Z

On Thu, Sep 06, 2007 at 01:44:05PM +0530, Satyam Sharma wrote:
> /dev/kmem was just an example -- IMHO differentiating between kernel and
> userspace from a security p.o.v. is always tricky.

The things that come to mind are /dev/kmem and module-loading. What
else is there? And what is it that makes this inherently difficult?

> Like Trond said, there are very high number of ways in which
> privileged userspace can compromise a running kernel if it really
> wants to do that, root-is-God has always been *the* major problem with
> Unix :-)
>
> The only _real_ way a kernel can lock itself completely against
> malicious userspace involves trusted tamperproof hardware,

The question of how to protect against someone with *physical* access
certainly is more difficult, but surely that's a separate problem.

--b.