Re: [Xen-devel] dom0 vs non-dom0 differentiation inside Xen hypervisor

[Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>]

On Mon, 2007-09-03 at 08:45 +0800, Peter Teoh wrote:
> In some parts of IA64 I can see that domain==dom0 checking is done,
> but in all of x86 - I have yet to find a proper checking that the
> hypercalls comes from a dom0 domain instead of any other domain. 
> 
> Theoretically, this means that any domain (PV or HVM) can always
> modify its own kernel binary and then make a direct hypercall (via int
> 0x82 or SYSENTER) into the hypervisor, executing domain controller
> commands like create domain etc. 
> 
> Is this possible?

No. The checks you are talking about are done using IS_PRIV() rather
than comparing directly domain==dom0.

e.g. from do_domctl and do_sysctl:
   if ( !IS_PRIV(current->domain) )
        return -EPERM;

In practise only dom0 passes this test.

Cheers,
Ian.



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