KVM, QEMU, and kernel project management [LWN.net]

KVM, QEMU, and kernel project management

Posted Mar 30, 2010 3:28 UTC (Tue) by dlang (guest, #313)
In reply to: KVM, QEMU, and kernel project management by jeremiah
Parent article: KVM, QEMU, and kernel project management

given that the guest doesn't really control it's own ram, but the host OS does, there is no way that the guest can prevent the host OS from examining or changing the ram in the guest, there is no way for the guest to protect itself from the host if the host is malicious.

what is possible in theory is that the host could prevent one guest from escaping then using the host privileges to attack another guest. However this is the same theory that says that one user on a system can be prevented from attacking another user on the same system. That hasn't worked in real life, and I doubt if the protecting one guest form another will work much better.

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KVM, QEMU, and kernel project management

Posted Mar 30, 2010 11:21 UTC (Tue) by jeremiah (subscriber, #1221) [Link] (1 responses)

I was thinking the the guest could encrypt or remap it's ram in a fashion that was known only to it.

KVM, QEMU, and kernel project management

Posted Mar 30, 2010 19:57 UTC (Tue) by nix (subscriber, #2304) [Link]

Sure it can. But the host can observe the guest's RAM, so can easily
acquire any necessary encryption keys and do the decryption itself. Even
if it got the key off the network, the host could spy on the network and
capture the key, or spy on the guest and watch the key come in, and then
capture it.

It is simply not possible to protect a VM guest from root on its host. The
host controls *everything*.