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Date: Wed, 29 Jun 2011 15:58:03 -0400 (EDT)
From: Josh Bressers <bressers@...hat.com>
To: oss-security@...ts.openwall.com
Cc: "Steven M. Christey" <coley@...us.mitre.org>
Subject: Re: CVE request: qemu-kvm: OOB memory access caused
 by negative vq notifies

Please use CVE-2011-2512.

Thanks.

-- 
    JB

----- Original Message -----
> The virtio_queue_notify() function checks that the virtqueue number is
> less than the maximum number of virtqueues. A signed comparison is
> used but the virtqueue number could be negative if a buggy or
> malicious
> guest is run. This results in memory accesses outside of the virtqueue
> array.
> 
> To trigger this issue the attacker needs to issue 32bit write to Queue
> Notify field of Virtio Header in the virtio pci config space even
> though
> the field is 16bit only by specs. Qemu-kvm allows that for the moment
> and provides whole 32bit value to the underlying functions.
> 
> Unprivileged guest user could use this flaw to crash the guest (denial
> of service) or, possibly, escalate their privileges on the host.
> 
> Upstream patch:
> http://patchwork.ozlabs.org/patch/94604/
> 
> References:
> https://bugzilla.redhat.com/show_bug.cgi?id=717399
> http://patchwork.ozlabs.org/patch/94604/
> 
> Thanks,
> --
> Petr Matousek / Red Hat Security Response Team

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