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

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Date:	Wed, 27 Jun 2012 23:22:04 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Alex Williamson <alex.williamson@...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, Jun 27, 2012 at 02:12:18PM -0600, Alex Williamson wrote:
> 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. :-\

This is what I'm asking.

> > > ---
> > > 
> > >  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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