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Re: [Xen-devel] Module loading in unpriveledged domains

To: david.nospam.hopwood@xxxxxxxxxxxxxxxx
Subject: Re: [Xen-devel] Module loading in unpriveledged domains
From: Ian Pratt <Ian.Pratt@xxxxxxxxxxxx>
Date: Mon, 22 Nov 2004 21:57:03 +0000
Cc: xen-devel@xxxxxxxxxxxxxxxxxxxxx, Ian.Pratt@xxxxxxxxxxxx
Delivery-date: Mon, 22 Nov 2004 21:59:24 +0000
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In-reply-to: Your message of "Mon, 22 Nov 2004 19:37:56 GMT." <41A24014.9060400@xxxxxxxxxxxxxxxx>
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> Ian Pratt wrote:
> >>Is there any security risk in enabling loadable module support in the linux
> >>kernel used for the unpriveledged domains? I ask this question in the 
> >>context of
> >>a virtual private server hosting provider.
> > 
> > There shouldn't be any security risk at all -- Xen should provide
> > all the isolation you need (modulo any bugs).
> So the answer to the original question is, "yes, enabling loadable module
> support will increase your exposure to security risks due to any weaknesses
> in Xen's isolation." Xen hasn't had particularly extensive security review
> yet.

I don't think that preventing loadable module support is going to
buy you anything. If your users have root they can write to the
domain's memory image and hence in practice do anything that they
could if they had kernel modules.

Xen has been designed to provide secure isolation between
guests. It has undergone code review by a bunch of different
people. It may have security bugs, but at least they're
relatively obscure...


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