Re: [uml-devel] [uml-user] [PATCH] uml hostfs: fix interaction between hostfs=path1 and -o path2 at mount time (was: Re: hostfs kernel parameter fail?)

Re: [uml-devel] [uml-user] [PATCH] uml hostfs: fix interaction between hostfs=path1 and -o path2 at mount time (was: Re: hostfs kernel parameter fail?)

[Blaisorblade]

On Sunday 04 March 2007 17:50, Sylvain Beucler wrote:
> On Sat, Mar 03, 2007 at 07:32:46PM +0100, Blaisorblade wrote:
> Hi,
>
> I tested and it works.
>
> Thanks,

You'll probably also see that -o .. allows bypassing the 'hostfs jail', and 
I've just implemented a fix to that. The question is whether this should be 
merged.

Indeed, the root user inside UML can bypass that anyway, if he modifies the 
hostfs module, compiles and loads it. So the host admin really needs to run 
UML in a chroot if he needs real security.

What do you all think?
-- 
Inform me of my mistakes, so I can add them to my list!
Paolo Giarrusso, aka Blaisorblade
http://www.user-mode-linux.org/~blaisorblade

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Re: [uml-devel] [uml-user] [PATCH] uml hostfs: fix interaction between hostfs=path1 and -o path2 at mount time

[Antoine Martin]

Blaisorblade wrote:
> On Sunday 04 March 2007 17:50, Sylvain Beucler wrote:
>> On Sat, Mar 03, 2007 at 07:32:46PM +0100, Blaisorblade wrote:
>> Hi,
>>
>> I tested and it works.
>>
>> Thanks,
> 
> You'll probably also see that -o .. allows bypassing the 'hostfs jail', and 
> I've just implemented a fix to that. The question is whether this should be 
> merged.
> 
> Indeed, the root user inside UML can bypass that anyway, if he modifies the 
> hostfs module, compiles and loads it.
If security is at stake then the host admin should use non-modular 
kernels to prevent such tampering.

> So the host admin really needs to run 
> UML in a chroot if he needs real security.
chroot isn't totally foolproof (see chroot-again issue), but when 
chrooting + changing user (like compartment does), it should be pretty safe.

Antoine

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Re: [uml-devel] [uml-user] [PATCH] uml hostfs: fix interaction between hostfs=path1 and -o path2 at mount time

[Blaisorblade]

On Sunday 04 March 2007 23:53, Antoine Martin wrote:
> Blaisorblade wrote:
> > On Sunday 04 March 2007 17:50, Sylvain Beucler wrote:
> >> On Sat, Mar 03, 2007 at 07:32:46PM +0100, Blaisorblade wrote:
> >> Hi,
> >>
> >> I tested and it works.
> >>
> >> Thanks,
> >
> > You'll probably also see that -o .. allows bypassing the 'hostfs jail',
> > and I've just implemented a fix to that. The question is whether this
> > should be merged.
> >
> > Indeed, the root user inside UML can bypass that anyway, if he modifies
> > the hostfs module, compiles and loads it.
>
> If security is at stake then the host admin should use non-modular
> kernels to prevent such tampering.

I know /dev/kmem allows bypassing that, but I don't know of any kmem-insmod 
out there (and that would make the issue quite practical).
-- 
Inform me of my mistakes, so I can add them to my list!
Paolo Giarrusso, aka Blaisorblade
http://www.user-mode-linux.org/~blaisorblade
Chiacchiera con i tuoi amici in tempo reale! 
 http://it.yahoo.com/mail_it/foot/*http://it.messenger.yahoo.com 


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