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

From: Pavel Machek <pavel@ucw.cz>
To: Jann Horn <jannh@google.com>
Cc: "Catangiu, Adrian Costin" <acatan@amazon.com>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
	"virtualization@lists.linux-foundation.org" 
	<virtualization@lists.linux-foundation.org>,
	"linux-api@vger.kernel.org" <linux-api@vger.kernel.org>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
	"rjw@rjwysocki.net" <rjw@rjwysocki.net>,
	"len.brown@intel.com" <len.brown@intel.com>,
	"mhocko@kernel.org" <mhocko@kernel.org>,
	"fweimer@redhat.com" <fweimer@redhat.com>,
	"keescook@chromium.org" <keescook@chromium.org>,
	"luto@amacapital.net" <luto@amacapital.net>,
	"wad@chromium.org" <wad@chromium.org>,
	"mingo@kernel.org" <mingo@kernel.org>,
	"bonzini@gnu.org" <bonzini@gnu.org>, "Graf (AWS),
	Alexander" <graf@amazon.de>,
	"MacCarthaigh, Colm" <colmmacc@amazon.com>,
	"Singh, Balbir" <sblbir@amazon.com>,
	"Sandu, Andrei" <sandreim@amazon.com>,
	"Brooker, Marc" <mbrooker@amazon.com>,
	"Weiss, Radu" <raduweis@amazon.com>,
	"Manwaring, Derek" <derekmn@amazon.com>
Subject: Re: [RFC]: mm,power: introduce MADV_WIPEONSUSPEND
Date: Sat, 4 Jul 2020 13:48:20 +0200	[thread overview]
Message-ID: <20200704114820.GA16083@amd> (raw)
In-Reply-To: <CAG48ez0oWQd42a-H-Dzw1Wq7HgB5PpFRGCZeYxP8ohxaoZHmvQ@mail.gmail.com>

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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...
> 
> And then the kernel would just need to maintain a sequence
> number in the vDSO data page that gets bumped on suspen

Yes, something like that would work. Plus, we'd be free to change the
mechanism in future.

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

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