Re: [PATCH 01/12] Security: Add CAP_COMPROMISE_KERNEL

["H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>]

On 03/19/2013 07:48 PM, H. Peter Anvin wrote:
> On 03/19/2013 06:28 PM, Matthew Garrett wrote:
>> Mm. The question is whether we can reliably determine the ranges a device should be able to access without having to trust userspace (and, ideally, without having to worry about whether iommu vendors have done their job). It's pretty important for PCI passthrough, so we do need to care. 
> 
> It is actually very simple: the device should be able to DMA into/out of:
> 
> 1. pinned pages
> 2. owned by the process controlling the device
> 
> ... and nothing else.
> 

The "pinning" process needs to involve a call to the kernel to process
the page for DMA (pinning the page and opening it in the iommu) and
return a transaction address, of course.

I think we have the interface for that in vfio, but I haven't followed
that work.

	-hpa