Re: [RFC 3/4] HVM x86 deprivileged mode: Code for switching into/out of deprivileged mode

[David Vrabel <david.vrabel@citrix.com>]

On 07/08/15 13:51, Ben Catterall wrote:
> 
> I don't know if we can make these synchronous as we need a way to
> interrupt the vcpu if it's spinning for a long time. Otherwise an
> attacker could just spin in depriv and cause a DoS. With that in mind,
> the scheduler may decide to migrate the vcpu whilst it's in depriv mode
> which would mean this per-pcpu data is held in the stack copy which is
> then migrated to another pcpu incorrectly.

IMO, DoS attacks on depriv'd emulators aren't very interesting.

I think it is counter-productive to address this attack in this initial
implementation at the expense (delays/complexity/etc.) of solving the
key requirement of mitigating information leaks and privilege escalation
attacks

David