Date: Fri, 15 Apr 2016 15:06:26 +0200 From: Pavel Machek <pavel@...x.de> To: Kees Cook <keescook@...omium.org> Cc: Linus Torvalds <torvalds@...ux-foundation.org>, "Rafael J. Wysocki" <rafael@...nel.org>, Ingo Molnar <mingo@...nel.org>, James Morse <james.morse@....com>, Ard Biesheuvel <ard.biesheuvel@...aro.org>, Matt Redfearn <matt.redfearn@...tec.com>, Yves-Alexis Perez <corsac@...ian.org>, Emrah Demir <ed@...sec.com>, Jonathan Corbet <corbet@....net>, "x86@...nel.org" <x86@...nel.org>, Len Brown <len.brown@...el.com>, Borislav Petkov <bp@...e.de>, Andy Lutomirski <luto@...nel.org>, "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>, Linux PM list <linux-pm@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com> Subject: Re: [PATCH v2] kaslr: allow kASLR to be default over Hibernation Hi! > > Now I notice that it is quite unclear if it actually changes > > anything... > > Okay, right. So, there are a few problems that this patch is solving, > and maybe it needs to be broken up into separate patches, but it > didn't seem like it to me at the time. Specifically: > > 1) The x86 hibernation and KASLR code don't play well together currently. > > "1" was worked around so that both could be built in, but only one > would be active at a time. This lead to: > 2) The general hibernation code contains kernel arguments that should > only affect x86. > > And we have the desire by folks to have KASLR enabled by default on > x86, giving us: > > 3) There is no build-time way on x86 to switch the preference of KASLR > vs hibernation. > > I think "2" should be solved for this release, since arm64 KASLR is > landing, and mistakenly booting an arm64 system with "kaslr" on the > command line will needlessly disable hibernation. Yes, I have no problem with "2". > 3 and 2 are a result of 1, and IIUC, you're saying you want to solve 1 > to make everything else go away? My only concern with that idea is > that I don't (yet) have the knowledge of x86 hibernation internals to > fix this, and it'll take a while to get to having KASLR on by default > if we have to wait on me to fix hibernation. (I'm not saying I > won't/can't, it's just that it'll take me time to come up to speed on > it.) > > That do you think? I believe it is more important to get it right than to have a solution right now. x86-64 should be best architecture to start... I don't understand kaslr, but it looks to me like you need to store the kaslr seed in the hibernation image, then use thet in set_up_temporary_mappings(). It should not be that bad. 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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