DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 1FF31C056786
Date: Fri, 30 Jun 2017 14:14:23 +0800
From: Dave Young <dyoung@redhat.com>
To: Baoquan He <bhe@redhat.com>
Cc: mingo@kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de,
        hpa@zytor.com
Subject: Re: [PATCH v2 0/2] x86/boot/KASLR: Code bug fix about kernel virtual
 address randomization
Message-ID: <20170630061423.GA13433@dhcp-128-65.nay.redhat.com>
References: <1498567146-11990-1-git-send-email-bhe@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1498567146-11990-1-git-send-email-bhe@redhat.com>
User-Agent: Mutt/1.7.1 (2016-10-04)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1442
Lines: 36

On 06/27/17 at 08:39pm, Baoquan He wrote:
> People complained that crashkernel high doesn't work when kaslr code
> compiled in but add 'nokaslr' to diable it. Kexec has the same
> phenomenon.

This is a regression, with 4.12* kernel kexec reboot fails always on
my desktop pc now without kaslr being enabled.

> 
> The root cause is a code bug which assigned the original loading address
> of kernel to the local variable 'virt_addr' which represents the offset
> of kernel virtual address randmoization. As we know, kernel can be loaded
> to anywhere under 64T physically, this wrong assignment could cause kernel
> relocation handling of x86 64 error if no kaslr is taken.
> 
> The v1 post can be found here:
>   x86/boot/KASLR: Skip relocation handling in no kaslr case
>   https://patchwork.kernel.org/patch/9807789/
> 
> In v2, Ingo suggested that we should add a judgement to check if 'virt_addr'
> is randomized to make kernel beyond the kernel mapping area. This checking
> can let us know the error but not reset to firmware quietly as it does now.
> 
> Baoquan He (2):
>   x86/boot/KASLR: Add checking for the offset of kernel virtual address
>     randomization
>   x86/boot/KASLR: Fix the wrong assignment to 'virt_addr'
> 
>  arch/x86/boot/compressed/kaslr.c | 3 ---
>  arch/x86/boot/compressed/misc.c  | 6 ++++--
>  arch/x86/boot/compressed/misc.h  | 2 --
>  3 files changed, 4 insertions(+), 7 deletions(-)
> 
> -- 
> 2.5.5
>