netdev - Re: [PATCH 1/2] virtio-net: Verify page list size before fitting into skb

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Message-ID: <20110926195716.GB23086@redhat.com>
Date:	Mon, 26 Sep 2011 22:57:17 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Pekka Enberg <penberg@...helsinki.fi>
Cc:	Sasha Levin <levinsasha928@...il.com>,
	linux-kernel@...r.kernel.org,
	Rusty Russell <rusty@...tcorp.com.au>,
	virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
	kvm@...r.kernel.org
Subject: Re: [PATCH 1/2] virtio-net: Verify page list size before fitting
 into skb

On Mon, Sep 26, 2011 at 10:45:35PM +0300, Pekka Enberg wrote:
> On Mon, Sep 26, 2011 at 10:37 PM, Sasha Levin <levinsasha928@...il.com> wrote:
> >> Interesting.  This is a theoretical issue, correct?
> >> Not a crash you actually see.
> >
> > Actually it was an actual crash caused when our virtio-net driver in kvm
> > tools did funny things and passed '(u32)-1' length as a buffer length to
> > the guest kernel.
> 
> I'm not sure what Michael means with "theoretical issue" here. Can the guest
> driver assume that the hypervisor doesn't attempt to do nasty things?
> 
>                           Pekka

IMO yes, hypervisor has full access to guest memory so it's a safe
assumption. But surviving in the face of hypervisor bugs
is laudable goal, bugs do happen.

-- 
MST
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