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Re: [Qemu-devel] Re: [PATCH] whitelist host virtio networking features [


From: Anthony Liguori
Subject: Re: [Qemu-devel] Re: [PATCH] whitelist host virtio networking features [was Re: qemu-kvm-0.11 regression, crashes on older ...]
Date: Mon, 02 Nov 2009 12:55:36 -0600
User-agent: Thunderbird 2.0.0.23 (X11/20090825)

Jamie Lokier wrote:
Anthony Liguori wrote:
Mark McLoughlin wrote:
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.
IMHO, the CVE should be against the 2.6.25 virtio drivers - the bug is
in the guest and the issue we're discussing here is just a hacky
workaround for the guest bug.
Yeah, I'm inclined to agree. The guest generates bad data and we exit. exit()ing is probably not wonderful but it's a well understood behavior.

The fundamental bug here is in the guest, not in qemu.

Guests should never be able to crash or terminate qemu, unless they
call something that is intentionally an "exit qemu" hook for the
guest.  And even that should be possible to disable.

They can exit qemu via an ACPI shutdown.  I don't see the difference.

Regards,

Anthony Liguori




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