[Info-vax] Intel junk...Kernel-memory-leaking Intel processor design flaw forces Linux, Windows redesign

[Jan-Erik Soderholm]

Den 2018-01-07 kl. 00:09, skrev Andy Burns:
> Tim Streater wrote:
> 
>> Does that involve instructions that operate on the cache. Such as
>> "clear cache"?
> 
> Yes, for the example I saw
> 
> <https://gist.github.com/ErikAugust/724d4a969fb2c6ae1bbd7b2a9e3d4bb6/revisions> 
> 
> 
> but I think it was only using spectre techniques to read from a chunk of 
> memory within the same process, to demonstrate how the timing works.
> 
> The x86-64 reference manual
> 
> <https://www.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-software-developer-instruction-set-reference-manual-325383.pdf> 
> 
> 
> states
> 
> "The CLFLUSH instruction can be used at all privilege levels and is subject 
> to all permission checking and faults associated with a byte load"
> 
> so perhaps the example is too simplistic and a real attack wouldn't be able 
> to flush the target area of memory from the cache lines, unless it already 
> had permission to access that memory?

You just have to make sure that nothing that is related to what you are
doing is cached. Such as loading some *other* data that belongs to you.