Re: [RFC]: mm,power: introduce MADV_WIPEONSUSPEND

Hi!

Cryptographic libraries carry pseudo random number generators to
quickly provide randomness when needed. If such a random pool gets
cloned, secrets may get revealed, as the same random number may get
used multiple times. For fork, this was fixed using the WIPEONFORK
madvise flag [1].

Unfortunately, the same problem surfaces when a virtual machine gets
cloned. The existing flag does not help there. This patch introduces a
new flag to automatically clear memory contents on VM suspend/resume,
which will allow random number generators to reseed when virtual
machines get cloned.

Umm. If this is real problem, should kernel provide such rng in the
vsdo page using vsyscalls? Kernel can have special interface to its
vsyscalls, but we may not want to offer this functionality to rest of
userland...

 - Provides a simple mechanism to avoid RAM exfiltration during
   traditional sleep/hibernate on a laptop or desktop when memory,
   and thus secrets, are vulnerable to offline tampering or
   inspection.

This second use has nothing to do with RNGs, right?

And I don't think we should do this in kernel.

It is userspace that initiates the suspend transition. Userspace
should lock the screen _before_ starting it, for example. Userspace
should also get rid of any secrets, first...

Best regards,
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html