[Qemu-devel] Re: [PATCH] whitelist host virtio networking features [was Re: qemu-kvm-0.11 regression, crashes on older ...]

[Dustin Kirkland <kirkland@canonical.com>]

On Thu, Oct 29, 2009 at 10:34 AM, Dustin Kirkland
<kirkland@canonical.com> wrote:
> whitelist host virtio networking features
>
> This patch is a followup to 8eca6b1bc770982595db2f7207c65051572436cb,
> fixing crashes when guests with 2.6.25 virtio drivers have saturated
> virtio network connections.
>
> https://bugs.edge.launchpad.net/ubuntu/+source/qemu-kvm/+bug/458521
>
> That patch should have been whitelisting *_HOST_* rather than the the
> *_GUEST_* features.
>
> I tested this by running an Ubuntu 8.04 Hardy guest (2.6.24 kernel +
> 2.6.25-virtio driver).  I saturated both the incoming, and outgoing
> network connection with nc, seeing sustained 6MB/s up and 6MB/s down
> bitrates for ~20 minutes.  Previously, this crashed immediately.  Now,
> the guest does not crash and maintains network connectivity throughout
> the test.
<snip>

FYI...

Canonical's Ubuntu Security Team will be filing a CVE on this issue,
since there is a bit of an attack vector here, and since
qemu-kvm-0.11.0 is generally available as an official release (and now
part of Ubuntu 9.10).

Guests running linux <= 2.6.25 virtio-net (e.g Ubuntu 8.04 hardy) on
top of qemu-kvm-0.11.0 can be remotely crashed by a non-privileged
network user flooding an open port on the guest.  The crash happens in
a manner that abruptly terminates the guest's execution (ie, without
shutting down cleanly).  This may affect the guest filesystem's
general happiness.

:-Dustin