Re: NFS4 authentification / fsuid

J. Bruce Fields
2007-09-07T15:34:35Z

On Fri, Sep 07, 2007 at 01:32:52AM +0200, Trond Myklebust wrote:
> Sorry. Of course, you have to copy the entire /lib, etc. onto the tmpfs,
> but you get the gist....
>
> The point is that it is easy to subvert userspace if you have enough
> privileges. In the above example it may not be entirely undetectable,
> but who here is running a script on every login to check that / is
> indeed uncompromised?

I suppose this is the motivation for things like the "secure attention
key"?

But I'm most curious actually about to what degree the kernel itself is
vulnerable to root (without a reboot). Is disabling /dev/kmem and
module-loading in theory enough? (Modulo bugs like filesystems that
aren't secure against untrusted filesystems, etc.)

--b.