Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750794AbdGYGWb convert rfc822-to-8bit (ORCPT ); Tue, 25 Jul 2017 02:22:31 -0400 Received: from tyo161.gate.nec.co.jp ([114.179.232.161]:36224 "EHLO tyo161.gate.nec.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750744AbdGYGW3 (ORCPT ); Tue, 25 Jul 2017 02:22:29 -0400 From: Naoya Horiguchi To: Matt Fleming CC: Baoquan He , Kees Cook , "linux-kernel@vger.kernel.org" , "x86@kernel.org" , Thomas Gleixner , "H. Peter Anvin" , Ingo Molnar , "izumi.taku@jp.fujitsu.com" , Thomas Garnier , "fanc.fnst@cn.fujitsu.com" , Junichi Nomura , Ard Biesheuvel Subject: Re: [PATCH v3 1/2] x86/boot/KASLR: exclude EFI_BOOT_SERVICES_{CODE|DATA} from KASLR's choice Thread-Topic: [PATCH v3 1/2] x86/boot/KASLR: exclude EFI_BOOT_SERVICES_{CODE|DATA} from KASLR's choice Thread-Index: AQHTBH8qi9Rzb/SLAkeDdA0kMcwBWqJje26A Date: Tue, 25 Jul 2017 06:17:11 +0000 Message-ID: <20170725061711.GB18610@hori1.linux.bs1.fc.nec.co.jp> References: <20170710054733.GA22619@hori1.linux.bs1.fc.nec.co.jp> <1499665896-23731-1-git-send-email-n-horiguchi@ah.jp.nec.com> <20170724131707.GA11076@codeblueprint.co.uk> In-Reply-To: <20170724131707.GA11076@codeblueprint.co.uk> Accept-Language: en-US, ja-JP Content-Language: ja-JP X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.128.101.4] Content-Type: text/plain; charset="iso-2022-jp" Content-ID: Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-TM-AS-MML: disable Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2131 Lines: 51 On Mon, Jul 24, 2017 at 02:17:07PM +0100, Matt Fleming wrote: > On Mon, 10 Jul, at 02:51:35PM, Naoya Horiguchi wrote: > > KASLR chooses kernel location from E820_TYPE_RAM regions by walking over > > e820 entries now. E820_TYPE_RAM includes EFI_BOOT_SERVICES_CODE and > > EFI_BOOT_SERVICES_DATA, so those regions can be the target. According to > > UEFI spec, all memory regions marked as EfiBootServicesCode and > > EfiBootServicesData are available for free memory after the first call > > of ExitBootServices(). So such regions should be usable for kernel on > > spec basis. > > > > In x86, however, we have some workaround for broken firmware, where we > > keep such regions reserved until SetVirtualAddressMap() is done. > > See the following code in should_map_region(): > > > > static bool should_map_region(efi_memory_desc_t *md) > > { > > ... > > /* > > * Map boot services regions as a workaround for buggy > > * firmware that accesses them even when they shouldn't. > > * > > * See efi_{reserve,free}_boot_services(). > > */ > > if (md->type == EFI_BOOT_SERVICES_CODE || > > md->type == EFI_BOOT_SERVICES_DATA) > > return false; > > > > This workaround suppressed a boot crash, but potential issues still > > remain because no one prevents the regions from overlapping with kernel > > image by KASLR. > > > > So let's make sure that EFI_BOOT_SERVICES_{CODE|DATA} regions are never > > chosen as kernel memory for the workaround to work fine. > > > > Signed-off-by: Naoya Horiguchi > > --- > > v2 -> v3: > > - skip EFI_LOADER_CODE and EFI_LOADER_DATA in region scan > > > > v1 -> v2: > > - switch efi_mirror_found to local variable > > - insert break when EFI_MEMORY_MORE_RELIABLE found > > --- > > arch/x86/boot/compressed/kaslr.c | 44 +++++++++++++++++++++++++++++----------- > > 1 file changed, 32 insertions(+), 12 deletions(-) > > I think the patch content is fine, but please update the comments and > the changelog to say why EFI_CONVENTIONAL_MEMORY was chosen, i.e. that > it's the only memory type that we know to be free. OK, I'll update this.