Re: Restricting rdtsc [was: kernel aslr]

[Alexander Nasonov <alnsn%yandex.ru@localhost>]

Maxime Villard wrote:
> Having read several papers on the exploitation of cache latency to defeat
> aslr (kernel or not), it appears that disabling the rdtsc instruction is a
> good mitigation on x86. However, some applications can legitimately use it,
> so I would rather suggest restricting it to root instead.

Why does root need it? For ntp? Properly implemented ntp should be
privsep'ed.

I think this should be either all-or-nothing. You either have rdtsc as
a time source or you don't. Similar for rdpmc (and other performance
counters).

-- 
Alex