Side-channel attacks (Meltdown, Spectre)

[Alexander Boettcher]

> I am not following the recent development of all those kernels, so I
> think it's best to directly consult the individual developers/teams for
> statements (like the one from Stefan above).
> 
> For my part, I can tell you that the NOVA microhypervisor (at least the
> official version) does not map physical RAM into the kernel virtual address
> space, other than the RAM in which microhypervisor itself resides. NOVA maps
> certain devices (like APIC, IOMMU), but those can't be speculatively
> accessed anyway. I cannot comment on modified NOVA versions.

I for my part, can confirm that the slightly, cough, modified NOVA
version [1], as used by Genode, kept the original behavior of the
official NOVA version [0] in that regard.

> Some commercial kernels and L4/Fiasco certainly used to map as much physical
> memory as can fit into the kernel address space. Not sure if Fiasco.OC
> retains that behavior. Check for Physmem in class Mem_layout.
> 
> Also any kernel that performs certain things like long IPC via a lazily
> flushed IPC window may have transient mappings of memory belonging
> to other user processes.

Thanks for the insights,

Alex.

[0] https://github.com/udosteinberg/NOVA
[1] https://github.com/alex-ab/NOVA/tree/r9
-- 
Alexander Boettcher
Genode Labs

http://www.genode-labs.com - http://www.genode.org

Genode Labs GmbH - Amtsgericht Dresden - HRB 28424 - Sitz Dresden
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