From mboxrd@z Thu Jan 1 00:00:00 1970 Reply-To: kernel-hardening@lists.openwall.com From: Thomas Garnier Date: Tue, 9 Aug 2016 10:11:05 -0700 Message-Id: <1470762665-88032-2-git-send-email-thgarnie@google.com> In-Reply-To: <1470762665-88032-1-git-send-email-thgarnie@google.com> References: <1470762665-88032-1-git-send-email-thgarnie@google.com> Subject: [kernel-hardening] [PATCH v4 2/2] x86/KASLR: Increase BRK pages for KASLR memory randomization To: Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" , Borislav Petkov , Joerg Roedel , Dave Young , "Rafael J . Wysocki" , Lv Zheng , Thomas Garnier , Baoquan He , Dave Hansen , Mark Salter , Aleksey Makarov , Kees Cook , Andrew Morton , Christian Borntraeger , Fabian Frederick , Toshi Kani , Dan Williams Cc: x86@kernel.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com List-ID: Default implementation expects 6 pages maximum are needed for low page allocations. If KASLR memory randomization is enabled, the worse case of e820 layout would require 12 pages (no large pages). It is due to the PUD level randomization and the variable e820 memory layout. This bug was found while doing extensive testing of KASLR memory randomization on different type of hardware. Fixes: 021182e52fe0 ("Enable KASLR for physical mapping memory regions") Signed-off-by: Thomas Garnier --- Based on next-20160805 --- arch/x86/mm/init.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c index 6209289..796e7af 100644 --- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -122,8 +122,18 @@ __ref void *alloc_low_pages(unsigned int num) return __va(pfn << PAGE_SHIFT); } -/* need 3 4k for initial PMD_SIZE, 3 4k for 0-ISA_END_ADDRESS */ -#define INIT_PGT_BUF_SIZE (6 * PAGE_SIZE) +/* + * By default need 3 4k for initial PMD_SIZE, 3 4k for 0-ISA_END_ADDRESS. + * With KASLR memory randomization, depending on the machine e820 memory + * and the PUD alignment. We may need twice more pages when KASLR memory + * randomization is enabled. + */ +#ifndef CONFIG_RANDOMIZE_MEMORY +#define INIT_PGD_PAGE_COUNT 6 +#else +#define INIT_PGD_PAGE_COUNT 12 +#endif +#define INIT_PGT_BUF_SIZE (INIT_PGD_PAGE_COUNT * PAGE_SIZE) RESERVE_BRK(early_pgt_alloc, INIT_PGT_BUF_SIZE); void __init early_alloc_pgt_buf(void) { -- 2.8.0.rc3.226.g39d4020 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752499AbcHIRLt (ORCPT ); Tue, 9 Aug 2016 13:11:49 -0400 Received: from mail-pf0-f172.google.com ([209.85.192.172]:32941 "EHLO mail-pf0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932455AbcHIRLj (ORCPT ); Tue, 9 Aug 2016 13:11:39 -0400 From: Thomas Garnier To: Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" , Borislav Petkov , Joerg Roedel , Dave Young , "Rafael J . Wysocki" , Lv Zheng , Thomas Garnier , Baoquan He , Dave Hansen , Mark Salter , Aleksey Makarov , Kees Cook , Andrew Morton , Christian Borntraeger , Fabian Frederick , Toshi Kani , Dan Williams Cc: x86@kernel.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com Subject: [PATCH v4 2/2] x86/KASLR: Increase BRK pages for KASLR memory randomization Date: Tue, 9 Aug 2016 10:11:05 -0700 Message-Id: <1470762665-88032-2-git-send-email-thgarnie@google.com> X-Mailer: git-send-email 2.8.0.rc3.226.g39d4020 In-Reply-To: <1470762665-88032-1-git-send-email-thgarnie@google.com> References: <1470762665-88032-1-git-send-email-thgarnie@google.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Default implementation expects 6 pages maximum are needed for low page allocations. If KASLR memory randomization is enabled, the worse case of e820 layout would require 12 pages (no large pages). It is due to the PUD level randomization and the variable e820 memory layout. This bug was found while doing extensive testing of KASLR memory randomization on different type of hardware. Fixes: 021182e52fe0 ("Enable KASLR for physical mapping memory regions") Signed-off-by: Thomas Garnier --- Based on next-20160805 --- arch/x86/mm/init.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c index 6209289..796e7af 100644 --- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -122,8 +122,18 @@ __ref void *alloc_low_pages(unsigned int num) return __va(pfn << PAGE_SHIFT); } -/* need 3 4k for initial PMD_SIZE, 3 4k for 0-ISA_END_ADDRESS */ -#define INIT_PGT_BUF_SIZE (6 * PAGE_SIZE) +/* + * By default need 3 4k for initial PMD_SIZE, 3 4k for 0-ISA_END_ADDRESS. + * With KASLR memory randomization, depending on the machine e820 memory + * and the PUD alignment. We may need twice more pages when KASLR memory + * randomization is enabled. + */ +#ifndef CONFIG_RANDOMIZE_MEMORY +#define INIT_PGD_PAGE_COUNT 6 +#else +#define INIT_PGD_PAGE_COUNT 12 +#endif +#define INIT_PGT_BUF_SIZE (INIT_PGD_PAGE_COUNT * PAGE_SIZE) RESERVE_BRK(early_pgt_alloc, INIT_PGT_BUF_SIZE); void __init early_alloc_pgt_buf(void) { -- 2.8.0.rc3.226.g39d4020