Re: [PATCH 3/5] vhost: support upto 509 memory regions

Michael S. Tsirkin
2015-06-17T14:32:14Z

On Wed, Jun 17, 2015 at 03:20:44PM +0200, Paolo Bonzini wrote:
>
>
> On 17/06/2015 15:13, Michael S. Tsirkin wrote:
> > > > Considering userspace can be malicious, I guess yes.
> > > I don't think it's a valid concern in this case,
> > > setting limit back from 509 to 64 will not help here in any way,
> > > userspace still can create as many vhost instances as it needs
> > > to consume memory it desires.
> >
> > Not really since vhost char device isn't world-accessible.
> > It's typically opened by a priveledged tool, the fd is
> > then passed to an unpriveledged userspace, or permissions dropped.
>
> Then what's the concern anyway?
>
> Paolo

Each fd now ties up 16K of kernel memory. It didn't use to, so
priveledged tool could safely give the unpriveledged userspace
a ton of these fds.

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MST