Subject: Re: [PATCH net-net 0/4] Increase the limit of tuntap queues

From: "Michael S. Tsirkin" <[email-masked]>
Date: Mon, 24 Nov 2014 10:02:43 +0200

On Sun, Nov 23, 2014 at 08:23:21PM -0500, David Miller wrote:
> From: "Michael S. Tsirkin" <[email-masked]>
> Date: Sun, 23 Nov 2014 22:30:32 +0200
> 
> > qemu runs in the host, but it's unpriveledged: it gets
> > passed tun FDs by a priveledged daemon, and it only
> > has the rights to some operations,
> > in particular to attach and detach queues.
> > 
> > The assumption always was that this operation is safe
> > and can't make kernel run out of resources.
> 
> This creates a rather rediculous situation in my opinion.
> 
> Configuring a network device is a privileged operation, the daemon
> should be setting this thing up.
> 
> In no other context would we have to worry about something like this.

Right.  Jason corrected me.  I got it wrong:
what qemu does is TUNSETQUEUE and that needs to get a queue
that's already initialized by the daemon.

To create new queues daemon calls TUNSETIFF,
and that already can be used to create new devices,
so it's a priveledged operation.

This means it's safe to just drop the restriction,
exactly as you suggested originally.
-- 
MST