[Xen-users] malicious paravirtualized guests: security and isolation

["Vasiliy Baranov" <vasiliy.baranov@xxxxxxxxx>]

Hi,

I have a question about isolation and security guarantees Xen provides,
if any, in cases when domU guests are not completely trusted, that is,
can be malicious. Right now I am specifically interested in the
scenario where all guests are paravirtualized, but HVM case is of some
interest too.

Say, I want to let my users run their own guests on a Xen host that I
own. Users will bring their own disk images. I don't completely trust
my users. Does the use of Xen guarantees that malicious guests will be
unable to harm other guests or the entire host in any way (for example, kill the
entire host)? It is interesting to know both what is
guaranteed in theory (that is, if Xen and dom0 work as designed) and
how things go in practice.

If I disallow users to use their kernels, that is, if I run guests with
my own kernel(s) only, will that improve the situation? How about
loadable kernel modules? If I allow Linux guests to load their custom
kernel modules, will that nullify the effect of using trusted kernels?

I currently use Xen 3.1.4, if that matters.

Thank you very much in advance,
Vasiliy
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