linux-kernel - Re: [PATCH v2 3/6] kvm: Sanitize KVM

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Date:	Wed, 27 Jun 2012 14:12:18 -0600
From:	Alex Williamson <alex.williamson@...hat.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	avi@...hat.com, kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	jan.kiszka@...mens.com
Subject: Re: [PATCH v2 3/6] kvm: Sanitize KVM_IRQFD flags

On Wed, 2012-06-27 at 12:21 +0300, Michael S. Tsirkin wrote:
> On Tue, Jun 26, 2012 at 11:09:32PM -0600, Alex Williamson wrote:
> > We only know of one so far.
> > 
> > Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
> 
> Ugh. So we have a bug: we should have sanitized the fields.
> If there's buggy userspace that only set the low bit
> it will break with this change.
> Is it too late now? Do we need KVM_IRQFD2 which
> sanitized fields properly? Avi?

If we take that attitude that we haven't sanitized the bits in the past
and therefore all other bits are tainted from future use, we might as
well toss out this ioctl and start over.  There's no way to add
anything. :-\

> > ---
> > 
> >  virt/kvm/eventfd.c |    3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
> > index c307c24..7d7e2aa 100644
> > --- a/virt/kvm/eventfd.c
> > +++ b/virt/kvm/eventfd.c
> > @@ -340,6 +340,9 @@ kvm_irqfd_deassign(struct kvm *kvm, struct kvm_irqfd *args)
> >  int
> >  kvm_irqfd(struct kvm *kvm, struct kvm_irqfd *args)
> >  {
> > +	if (args->flags & ~KVM_IRQFD_FLAG_DEASSIGN)
> > +		return -EINVAL;
> > +
> >  	if (args->flags & KVM_IRQFD_FLAG_DEASSIGN)
> >  		return kvm_irqfd_deassign(kvm, args);
> >  



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