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

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Message-ID: <20120627092150.GD17507@redhat.com>
Date:	Wed, 27 Jun 2012 12:21:50 +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 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?

> ---
> 
>  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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