linux-kernel - Re: [Resend][PATCH] x86/power/64: Always create temporary identity mapping correctly

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Date:	Wed, 10 Aug 2016 23:52:38 +0200 (CEST)
From:	Jiri Kosina <jikos@...nel.org>
To:	Thomas Garnier <thgarnie@...gle.com>
cc:	Borislav Petkov <bp@...e.de>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Yinghai Lu <yinghai@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H . Peter Anvin" <hpa@...or.com>,
	Kees Cook <keescook@...omium.org>, Pavel Machek <pavel@....cz>,
	Kernel Hardening <kernel-hardening@...ts.openwall.com>
Subject: Re: [Resend][PATCH] x86/power/64: Always create temporary identity
 mapping correctly

On Wed, 10 Aug 2016, Thomas Garnier wrote:

> Ok, I want to know if the problem is the PUD alignment or the change
> of PAGE_OFFSET based all together. Can you test the following change?
> (on top of everything else with KASLR enabled). It will randomize the
> memory sections only on PGD level.
> 
> diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c
> index ec8654f..a8477b0 100644
> --- a/arch/x86/mm/kaslr.c
> +++ b/arch/x86/mm/kaslr.c
> @@ -120,7 +120,7 @@ void __init kernel_randomize_memory(void)
>                  */
>                 entropy = remain_entropy / (ARRAY_SIZE(kaslr_regions) - i);
>                 prandom_bytes_state(&rand_state, &rand, sizeof(rand));
> -               entropy = (rand % (entropy + 1)) & PUD_MASK;
> +               entropy = (rand % (entropy + 1)) & PGDIR_MASK;
>                 vaddr += entropy;
>                 *kaslr_regions[i].base = vaddr;
> 
> @@ -129,7 +129,7 @@ void __init kernel_randomize_memory(void)
>                  * randomization alignment.
>                  */
>                 vaddr += get_padding(&kaslr_regions[i]);
> -               vaddr = round_up(vaddr + 1, PUD_SIZE);
> +               vaddr = round_up(vaddr + 1, PGDIR_SIZE);
>                 remain_entropy -= entropy;
>         }
>  }

I applied this on top of both fixes from Rafael from this thread; still no 
change in behavior, i.e. reboot immediately after reading the hibernation 
image.

-- 
Jiri Kosina
SUSE Labs