Re: [Xen-devel] Security Implications of letting customers use theirown kernel

[Jonathan Tripathy <jonnyt@xxxxxxxxxxx>]

> On Thu, Dec 16, 2010 at 3:51 AM, James Harper
> <james.harper@xxxxxxxxxxxxxxxx>  wrote:
> > > An area of potential concern is if someone were to build a kernel that
> > > enabled "No Execute" or "Disable Execution", could that compromise
> > other
> > > DomUs? Or would that just leave their DomU vulnerable to running
> > > malicious code?
> I assume you mean a kernel that *disabled* No-Execute?
Yes, sorry
> No -- Xen
> should isolate decisions of individual VMs from each other (if the NX
> bit can be disabled from a PV kernel at all -- I'm not sure about
> that).
>
> That said, developers certainly *aim* to make it the case that a DomU
> cannot crash or gain access to Xen or Dom0 (or affect other security
> measures, like NX, in any way).
> However, as far as I'm aware, there
> is no testing or auditing done to verify this.
Given that Xen is used in many hosting  companies around the world, such 
as Amazon, isn't this alarming?
> And as James H. said,
> buggy DomU drivers do occasionally crash dom0: and if untrusted code
> can accidentally crash privileged code, it's often the case that a
> well-crafted exploit can use the same bug to gain control of the
> privileged code.
>
>   -George
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