Re: [PATCH v6 0/1] ns: introduce binfmt_misc namespace

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Thu, 2018-11-01 at 04:51 +0100, Jann Horn wrote:
> On Thu, Nov 1, 2018 at 3:59 AM James Bottomley
> <James.Bottomley@hansenpartnership.com> wrote:
> > 
> > On Tue, 2018-10-16 at 11:52 +0200, Laurent Vivier wrote:
> > > Hi,
> > > 
> > > Any comment on this last version?
> > > 
> > > Any chance to be merged?
> > 
> > I've got a use case for this:  I went to one of the Graphene talks
> > in Edinburgh and it struck me that we seem to keep reinventing the
> > type of sandboxing that qemu-user already does.  However if you
> > want to do an x86 on x86 sandbox, you can't currently use the
> > binfmt_misc mechanism because that has you running *every* binary
> > on the system emulated. Doing it per user namespace fixes this
> > problem and allows us to at least cut down on all the pointless
> > duplication.
> 
> Waaaaaait. What? qemu-user does not do "sandboxing". qemu-user makes
> your code slower and *LESS* secure. As far as I know, qemu-user is
> only intended for purposes like development and testing.

Sandboxing is about protecting the cloud service provider (and other
tenants) from horizontal attack by reducing calls to the shared kernel.
 I think it's pretty indisputable that full emulation is an effective
sandbox in that regard.

We can argue for about bugginess vs completeness, but technologically
qemu-user already has most of the system calls, which seems to be a
significant problem with other sandboxes.  I also can't dispute it's
slower, but that's a tradeoff for people to make.

James