Date: Wed, 6 Apr 2016 15:16:16 -0700 From: Kees Cook <keescook@...omium.org> To: "Rafael J. Wysocki" <rafael@...nel.org> Cc: Ingo Molnar <mingo@...nel.org>, Linus Torvalds <torvalds@...ux-foundation.org>, 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>, "Rafael J. Wysocki" <rjw@...ysocki.net>, Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>, Borislav Petkov <bp@...e.de>, Andy Lutomirski <luto@...nel.org>, "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>, "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com> Subject: Re: [PATCH] Prefer kASLR over Hibernation On Wed, Apr 6, 2016 at 3:04 PM, Rafael J. Wysocki <rafael@...nel.org> wrote: > On Wed, Apr 6, 2016 at 11:56 PM, Ingo Molnar <mingo@...nel.org> wrote: >> >> * Rafael J. Wysocki <rafael@...nel.org> wrote: >> >>> On Wed, Apr 6, 2016 at 9:44 PM, Kees Cook <keescook@...omium.org> wrote: >>> > When building with both CONFIG_HIBERNATION and CONFIG_RANDOMIZE_BASE, >>> > one or the other must be chosen at boot-time. Until now, hibernation >>> > was selected when no choice was made on the command line. >>> > >>> > To make the security benefits of kASLR more widely available to end >>> > users (since the use of hibernation is becoming more rare and kASLR, >>> > already available on x86, will be available on arm64 and MIPS soon), >>> > this changes the default to preferring kASLR over hibernation. Users >>> > wanting hibernation can turn off kASLR by adding "nokaslr" to the kernel >>> > command line. >>> > >>> > Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org> >>> > Signed-off-by: Kees Cook <keescook@...omium.org> >>> >>> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com> >>> >>> Or do you want me to apply it? >> >> I don't think this is a good idea, as it turns off emergency hibernation of >> laptops - many desktop distros support it by default. > > Right, I forgot about this one. When I last checked Ubuntu doesn't enable hibernation by default any more: https://help.ubuntu.com/16.04/ubuntu-help/power-hibernate.html And it seems like Fedora either doesn't either, or has a lot of people for whom it doesn't work: https://bugzilla.redhat.com/show_bug.cgi?id=1206936 https://bugzilla.redhat.com/show_bug.cgi?id=1224151 http://blog.kriptonium.com/2015/12/fedora-23-hibernate.html -Kees -- Kees Cook Chrome OS & Brillo Security
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