Re: [Qemu-devel] [RFC] [PATCH 0/2] Sandboxing Qemu guests with Libseccomp

[Corey Bryant <coreyb@linux.vnet.ibm.com>]

On 05/08/2012 07:32 AM, Stefano Stabellini wrote:
> On Tue, 8 May 2012, Daniel P. Berrange wrote:
>> On Fri, May 04, 2012 at 04:08:36PM -0300, Eduardo Otubo wrote:
>>> Hello all,
>>>
>>> This is the first effort to sandboxing Qemu guests using Libseccomp[0]. The
>>> patches that follows are pretty simple and straightforward. I added the correct
>>> options and checks to the configure script and the basic calls to libseccomp in
>>> the main loop at vl.c. Details of each one are in the emails of the patch set.
>>>
>>> This support limits the system call footprint of the entire QEMU process to a
>>> limited set of syscalls, those that we know QEMU uses.  The idea is to limit
>>> the allowable syscalls, therefore limiting the impact that an attacked guest
>>> could have on the host system.
>>
>> What functionality has been lost by applying this seccomp filter ? I've not
>> looked closely at the code, but it appears as if this blocks pretty much
>> any kind of runtime device changes. ie no hotplug of any kind will work ?
>
> Right, I was wondering the same thing: open is not on the list so adding
> a new disk shouldn't be possible.
>
> Regarding Xen, most of the hypercalls go through xc_* calls that are
> ioctls on the privcmd device. Is it possible to add ioctl to the list?
>

If the whitelist is complete there should be no functionality lost when 
using seccomp with QEMU.  The idea (at least at this point) is to 
disallow the system calls that QEMU doesn't use.  open and ioctl should 
be added to the whitelist.

-- 
Regards,
Corey