Re: [LSF/MM TOPIC] Address space isolation inside the kernel

[Matthew Wilcox <willy@infradead.org>]

On Sat, Feb 16, 2019 at 08:30:16AM -0800, James Bottomley wrote:
> On Sat, 2019-02-16 at 23:19 +1100, Balbir Singh wrote:
> > For namespaces, does allocating the right memory protection key
> > work? At some point we'll need to recycle the keys
> 
> I don't think anyone mentioned memory keys and namespaces ... I take it
> you're thinking of SEV/MKTME?

I thought he meant Protection Keys
https://en.wikipedia.org/wiki/Memory_protection#Protection_keys

> The idea being to shield one container's
> execution from another using memory encryption?  We've speculated it's
> possible but the actual mechanism we were looking at is tagging pages
> to namespaces (essentially using the mount namspace and tags on the
> page cache) so the kernel would refuse to map a page into the wrong
> namespace.  This approach doesn't seem to be as promising as the
> separated address space one because the security properties are harder
> to measure.

What do you mean by "tags on the pages cache"?  Is that different from
the radix tree tags (now renamed to XArray marks), which are search keys.