Re: Are root privileges really needed to run kvm?

[Anthony Liguori <anthony-rdkfGonbjUSkNkDKm+mE6A@public.gmane.org>]

Dimitry Golubovsky wrote:
> Anthony,
>
> On 6/13/07, Anthony Liguori <anthony-rdkfGonbjUSkNkDKm+mE6A@public.gmane.org> wrote:
>
>> One thing to consider is that if a userspace process can create KVM
>> guests, they are capable of pinning large quantities of physical
>> memory.  This could be used as a DoS attack so consider VM creation a
>> privileged operation.
>
> No, that's not what is intended. I was asking about possibility to run
> KVM at users privileges after some necessary actions have been
> completed, and tried to compile a list of such actions.
>
> That is,
>
> - adjust RTC (I just added this to the system startup script)

You can also just run guests with -no-rtc.

> - create a tap
> - add tap to the bridge (if bridging is used)/adjust iptables if no
> bridging (another example in qemu wiki)

You may want to look at VDE (http://vde.sf.net).  One of it's purposes 
was to allow non-privileged users to access bridges.

> - open /dev/kvm (as it has been found, group membership is sufficient
> if group can write to /dev/kvm)
>
> After that, process privileges might be dropped to those of the user
> who logged (ssh'd) in. Images of disk volumes and CDs may then be
> assigned proper permissions, so users may be more flexible on what to
> run, and regular Unix filesystem mechanisms will control access.

Yup.

> BTW if qemu_system_x86-64 runs at user privileges, can the memory
> consumed be subject to whatever per-user limits that may be set
> systemwide?

I don't think so although as Avi mentioned, this will be addressed when 
the overcommit patches are merged.

Regards,

Anthony Liguori


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