Re: [PATCH] mm/mincore: allow for making sys_mincore() privileged

[Jiri Kosina]

On Wed, 9 Jan 2019, Dave Chinner wrote:

> > But mincore is certainly the easiest interface, and the one that
> > doesn't require much effort or setup.
> 
> Off the top of my head, here's a few vectors for reading the page
> cache residency state without perturbing the page cache residency
> pattern:
> 	- mincore
> 	- preadv2(RWF_NOWAIT)
> 	- fadvise(POSIX_FADV_RANDOM); timed read(2) syscalls
> 	- madvise(MADV_RANDOM); timed read of first byte in each page

While I obviously agree that all those are creating pagecache sidechannel 
in principle, I think we really should mostly focus on the first two (with 
mincore() already having been covered).

Rationale has been provided by Daniel Gruss in this thread -- if the 
attacker is left with cache timing as the only available vector, he's 
going to be much more successful with mounting hardware cache timing 
attack anyway.

Thanks,

-- 
Jiri Kosina
SUSE Labs