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From: Ingo Molnar <mingo@kernel.org>
To: Kees Cook <keescook@chromium.org>
Cc: Baoquan He <bhe@redhat.com>, Yinghai Lu <yinghai@kernel.org>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Matt Redfearn <matt.redfearn@imgtec.com>,
	"x86@kernel.org" <x86@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
	Borislav Petkov <bp@alien8.de>, Vivek Goyal <vgoyal@redhat.com>,
	Andy Lutomirski <luto@kernel.org>,
	lasse.collin@tukaani.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Dave Young <dyoung@redhat.com>,
	"kernel-hardening@lists.openwall.com" 
	<kernel-hardening@lists.openwall.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH v5 03/21] x86, KASLR: Drop CONFIG_RANDOMIZE_BASE_MAX_OFFSET
Date: Sat, 16 Apr 2016 10:42:28 +0200	[thread overview]
Message-ID: <20160416084228.GA30071@gmail.com> (raw)
In-Reply-To: <CAGXu5jKXP0i28gbZ9Yu=fgrJ8G6kcs5oWem_1av2bezj72KK2Q@mail.gmail.com>


* Kees Cook <keescook@chromium.org> wrote:

> > Also note the assertive tone: if this Kconfig feature is eanbled, we say that 
> > the kernel address _will_ be randomized, and we should make sure it is. (If 
> > for some weird reason randomization fails we should warn prominently during 
> > bootup.)
> 
> This will need some thought... is it better to fail to boot or to boot without 
> entropy? As-is, it's possible to randomly position the kernel base address at 
> exactly the location it was going to boot without KASLR too, yet this is still 
> considered random...

I think we should boot but print a prominent warning. On real systems it's not 
supposed to happen, right? So we want to know if it happens, but don't want to 
hassle the user with breaking the system by not booting.

> > Also, could we always mix the i8254 timer into this as well, not just when 
> > RDTSC is unavailable?
> 
> IIRC, hpa explicitly did not want to do this when he was making
> suggestions on this area. I would need to dig out the thread -- I
> can't find it now. I'd prefer to leave this as-is, since changing it
> would add yet another variable to the behavioral changes of this
> series.

Sure, can stay as-is for now.

Thanks,

	Ingo

WARNING: multiple messages have this Message-ID (diff)
From: Ingo Molnar <mingo@kernel.org>
To: Kees Cook <keescook@chromium.org>
Cc: Baoquan He <bhe@redhat.com>, Yinghai Lu <yinghai@kernel.org>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Matt Redfearn <matt.redfearn@imgtec.com>,
	"x86@kernel.org" <x86@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
	Borislav Petkov <bp@alien8.de>, Vivek Goyal <vgoyal@redhat.com>,
	Andy Lutomirski <luto@kernel.org>,
	lasse.collin@tukaani.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Dave Young <dyoung@redhat.com>,
	"kernel-hardening@lists.openwall.com"
	<kernel-hardening@lists.openwall.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: [kernel-hardening] Re: [PATCH v5 03/21] x86, KASLR: Drop CONFIG_RANDOMIZE_BASE_MAX_OFFSET
Date: Sat, 16 Apr 2016 10:42:28 +0200	[thread overview]
Message-ID: <20160416084228.GA30071@gmail.com> (raw)
In-Reply-To: <CAGXu5jKXP0i28gbZ9Yu=fgrJ8G6kcs5oWem_1av2bezj72KK2Q@mail.gmail.com>


* Kees Cook <keescook@chromium.org> wrote:

> > Also note the assertive tone: if this Kconfig feature is eanbled, we say that 
> > the kernel address _will_ be randomized, and we should make sure it is. (If 
> > for some weird reason randomization fails we should warn prominently during 
> > bootup.)
> 
> This will need some thought... is it better to fail to boot or to boot without 
> entropy? As-is, it's possible to randomly position the kernel base address at 
> exactly the location it was going to boot without KASLR too, yet this is still 
> considered random...

I think we should boot but print a prominent warning. On real systems it's not 
supposed to happen, right? So we want to know if it happens, but don't want to 
hassle the user with breaking the system by not booting.

> > Also, could we always mix the i8254 timer into this as well, not just when 
> > RDTSC is unavailable?
> 
> IIRC, hpa explicitly did not want to do this when he was making
> suggestions on this area. I would need to dig out the thread -- I
> can't find it now. I'd prefer to leave this as-is, since changing it
> would add yet another variable to the behavioral changes of this
> series.

Sure, can stay as-is for now.

Thanks,

	Ingo

  reply	other threads:[~2016-04-16  8:42 UTC|newest]

Thread overview: 80+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-04-14 22:28 [PATCH v5 00/21] x86, boot: KASLR cleanup and 64-bit improvements Kees Cook
2016-04-14 22:28 ` [kernel-hardening] " Kees Cook
2016-04-14 22:28 ` [PATCH v5 01/21] x86, KASLR: Remove unneeded boot_params argument Kees Cook
2016-04-14 22:28   ` [kernel-hardening] " Kees Cook
2016-04-15  7:29   ` Ingo Molnar
2016-04-15  7:29     ` [kernel-hardening] " Ingo Molnar
2016-04-15 18:55     ` Kees Cook
2016-04-15 18:55       ` [kernel-hardening] " Kees Cook
2016-04-14 22:28 ` [PATCH v5 02/21] x86, KASLR: Handle kernel relocation above 2G Kees Cook
2016-04-14 22:28   ` [kernel-hardening] " Kees Cook
2016-04-15  7:47   ` Ingo Molnar
2016-04-15  7:47     ` [kernel-hardening] " Ingo Molnar
2016-04-15 19:01     ` Kees Cook
2016-04-15 19:01       ` [kernel-hardening] " Kees Cook
2016-04-14 22:28 ` [PATCH v5 03/21] x86, KASLR: Drop CONFIG_RANDOMIZE_BASE_MAX_OFFSET Kees Cook
2016-04-14 22:28   ` [kernel-hardening] " Kees Cook
2016-04-15  8:07   ` Ingo Molnar
2016-04-15  8:07     ` [kernel-hardening] " Ingo Molnar
2016-04-15 19:12     ` Kees Cook
2016-04-15 19:12       ` [kernel-hardening] " Kees Cook
2016-04-16  8:42       ` Ingo Molnar [this message]
2016-04-16  8:42         ` Ingo Molnar
2016-04-14 22:28 ` [PATCH v5 04/21] x86, boot: Move compressed kernel to end of decompression buffer Kees Cook
2016-04-14 22:28   ` [kernel-hardening] " Kees Cook
2016-04-15  8:09   ` Ingo Molnar
2016-04-15  8:09     ` [kernel-hardening] " Ingo Molnar
2016-04-18 16:50     ` Kees Cook
2016-04-18 16:50       ` [kernel-hardening] " Kees Cook
2016-04-15  9:05   ` Ingo Molnar
2016-04-15  9:05     ` [kernel-hardening] " Ingo Molnar
2016-04-14 22:28 ` [PATCH v5 05/21] x86, boot: Calculate decompression size during boot not build Kees Cook
2016-04-14 22:28   ` [kernel-hardening] " Kees Cook
2016-04-15  8:12   ` Ingo Molnar
2016-04-15  8:12     ` [kernel-hardening] " Ingo Molnar
2016-04-15 19:14     ` Kees Cook
2016-04-15 19:14       ` [kernel-hardening] " Kees Cook
2016-04-14 22:28 ` [PATCH v5 06/21] x86, KASLR: Update description for decompressor worst case size Kees Cook
2016-04-14 22:28   ` [kernel-hardening] " Kees Cook
2016-04-15 16:17   ` Lasse Collin
2016-04-15 16:17     ` [kernel-hardening] " Lasse Collin
2016-04-14 22:29 ` [PATCH v5 07/21] x86, boot: Fix run_size calculation Kees Cook
2016-04-14 22:29   ` [kernel-hardening] " Kees Cook
2016-04-15  8:31   ` Ingo Molnar
2016-04-15  8:31     ` [kernel-hardening] " Ingo Molnar
2016-04-15 19:26     ` Kees Cook
2016-04-15 19:26       ` [kernel-hardening] " Kees Cook
2016-04-16  9:00       ` Ingo Molnar
2016-04-16  9:00         ` [kernel-hardening] " Ingo Molnar
2016-04-14 22:29 ` [PATCH v5 08/21] x86, KASLR: Clean up unused code from old run_size Kees Cook
2016-04-14 22:29   ` [kernel-hardening] " Kees Cook
2016-04-14 22:29 ` [PATCH v5 09/21] x86, KASLR: Correctly bounds-check relocations Kees Cook
2016-04-14 22:29   ` [kernel-hardening] " Kees Cook
2016-04-14 22:29 ` [PATCH v5 10/21] x86, KASLR: Consolidate mem_avoid entries Kees Cook
2016-04-14 22:29   ` [kernel-hardening] " Kees Cook
2016-04-14 22:29 ` [PATCH v5 11/21] x86, boot: Split out kernel_ident_mapping_init Kees Cook
2016-04-14 22:29   ` [kernel-hardening] " Kees Cook
2016-04-14 22:29 ` [PATCH v5 12/21] x86, 64bit: Set ident_mapping for KASLR Kees Cook
2016-04-14 22:29   ` [kernel-hardening] " Kees Cook
2016-04-14 22:29 ` [PATCH v5 13/21] x86, boot: Report overlap failures in memcpy Kees Cook
2016-04-14 22:29   ` [kernel-hardening] " Kees Cook
2016-04-15 14:42   ` Lasse Collin
2016-04-15 14:42     ` [kernel-hardening] " Lasse Collin
2016-04-15 19:28     ` Kees Cook
2016-04-15 19:28       ` [kernel-hardening] " Kees Cook
2016-04-14 22:29 ` [PATCH v5 14/21] x86, KASLR: Add slot_area to manage random slots Kees Cook
2016-04-14 22:29   ` [kernel-hardening] " Kees Cook
2016-04-14 22:29 ` [PATCH v5 15/21] x86, KASLR: Add slot_area support functions Kees Cook
2016-04-14 22:29   ` [kernel-hardening] " Kees Cook
2016-04-14 22:29 ` [PATCH v5 16/21] x86, KASLR: Add virtual address choosing function Kees Cook
2016-04-14 22:29   ` [kernel-hardening] " Kees Cook
2016-04-14 22:29 ` [PATCH v5 17/21] x86, KASLR: Clarify purpose of each get_random_long Kees Cook
2016-04-14 22:29   ` [kernel-hardening] " Kees Cook
2016-04-14 22:29 ` [PATCH v5 18/21] x86, KASLR: Randomize virtual address separately Kees Cook
2016-04-14 22:29   ` [kernel-hardening] " Kees Cook
2016-04-14 22:29 ` [PATCH v5 19/21] x86, KASLR: Add physical address randomization >4G Kees Cook
2016-04-14 22:29   ` [kernel-hardening] " Kees Cook
2016-04-14 22:29 ` [PATCH v5 20/21] x86, KASLR: Remove unused slot tracking code Kees Cook
2016-04-14 22:29   ` [kernel-hardening] " Kees Cook
2016-04-14 22:29 ` [PATCH v5 21/21] x86, KASLR: Allow randomization below load address Kees Cook
2016-04-14 22:29   ` [kernel-hardening] " Kees Cook

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