From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1752497AbdGDPqj (ORCPT <rfc822;w@1wt.eu>);
        Tue, 4 Jul 2017 11:46:39 -0400
Received: from Galois.linutronix.de ([146.0.238.70]:49164 "EHLO
        Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1752286AbdGDPqi (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Tue, 4 Jul 2017 11:46:38 -0400
Date: Tue, 4 Jul 2017 17:46:35 +0200 (CEST)
From: Thomas Gleixner <tglx@linutronix.de>
To: Matt Fleming <matt@codeblueprint.co.uk>
cc: Baoquan He <bhe@redhat.com>, LKML <linux-kernel@vger.kernel.org>,
        x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
        Ingo Molnar <mingo@kernel.org>, Kees Cook <keescook@chromium.org>,
        thgarnie@google.com, caoj.fnst@cn.fujitsu.com,
        izumi.taku@jp.fujitsu.com
Subject: Re: [PATCH v2 2/2] x86/boot/KASLR: Restrict kernel to be randomized
 in mirror regions
In-Reply-To: <20170704153633.GA3149@codeblueprint.co.uk>
Message-ID: <alpine.DEB.2.20.1707041744510.9000@nanos>
References: <1499155442-17467-1-git-send-email-bhe@redhat.com> <1499155442-17467-3-git-send-email-bhe@redhat.com> <alpine.DEB.2.20.1707041555570.9000@nanos> <20170704143034.GA25192@x1> <alpine.DEB.2.20.1707041643400.9000@nanos>
 <20170704153633.GA3149@codeblueprint.co.uk>
User-Agent: Alpine 2.20 (DEB 67 2015-01-07)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Tue, 4 Jul 2017, Matt Fleming wrote:
> On Tue, 04 Jul, at 04:46:58PM, Thomas Gleixner wrote:
> > On Tue, 4 Jul 2017, Baoquan He wrote:
> >  
> > > In fact I just referred to code in setup_arch(). Now I have a question,
> > > though CONFIG_EFI=y but efi firmware is not enabled,
> > > boot_params.efi_info.efi_loader_signature should be initilized to 0.
> > > Then below code is also problematic.
> > >
> > > #ifdef CONFIG_EFI
> > >         if (!strncmp((char *)&boot_params.efi_info.efi_loader_signature,                                                                         
> > >                      EFI32_LOADER_SIGNATURE, 4)) {
> > >                 set_bit(EFI_BOOT, &efi.flags);
> > >         } else if (!strncmp((char *)&boot_params.efi_info.efi_loader_signature,
> > >                      EFI64_LOADER_SIGNATURE, 4)) {
> > >                 set_bit(EFI_BOOT, &efi.flags);
> > >                 set_bit(EFI_64BIT, &efi.flags);
> > >         }
> > > 
> > >         if (efi_enabled(EFI_BOOT))
> > >                 efi_memblock_x86_reserve_range();
> > > #endif
> > 
> > Indeed. Matt?
> 
> It's possibly that I'm missing some context, but boot_params should be
> zero'd -- the x86 boot protocol requires that the entire data
> structure be zero'd on allocation.
> 
> Have I missed something?

No. I misread the code. The strncmp() operates on
boot_params.efi_info.efi_loader_signature itself, so yes, all is fine.

It's just Baoquans copy and paste wreckage which is busted.

Thanks,

	tglx