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Re: [Qemu-devel] Re: [PATCHv2 09/12] vhost: vhost net support

From: Michael S. Tsirkin
Subject: Re: [Qemu-devel] Re: [PATCHv2 09/12] vhost: vhost net support
Date: Sun, 28 Feb 2010 12:15:09 +0200
User-agent: Mutt/1.5.19 (2009-01-05)

On Sun, Feb 28, 2010 at 01:59:27AM +0000, Paul Brook wrote:
> > > I'm pretty sure a guest can cause those to change and I'm not 100%
> > > sure,   but I think it's a potential source of exploits if you assume a
> > > mapping. In the very least, a guest can trick vhost into writing to ram
> > > that it wouldn't normally write to.
> > 
> > This seems harmless. guest can write anywhere in ram, anyway.
> Surely writing to the wrong address is always a fatal flaw.

If guest does an illegal operation, it can corrupt its own memory.
This is the case with physical devices as well.

>  There certainly 
> exist machines that can change physical RAM mapping.

I am talking about mapping between phy RAM offset and qemu virt address.
When can it change without RAM in question going away?

> While I wouldn't expect 
> this to happen during normal operation, it could occur between a (virtio-
> aware) bootloader/BIOS and real kernel.
> Paul

Should not matter for vhost, it is only active if driver is active ...

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