From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0F464C04A6B for ; Wed, 8 May 2019 08:04:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E037321019 for ; Wed, 8 May 2019 08:04:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726842AbfEHIEZ (ORCPT ); Wed, 8 May 2019 04:04:25 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52098 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726428AbfEHIEY (ORCPT ); Wed, 8 May 2019 04:04:24 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 3797681DE5; Wed, 8 May 2019 08:04:24 +0000 (UTC) Received: from MiWiFi-R3L-srv.redhat.com (ovpn-12-18.pek2.redhat.com [10.72.12.18]) by smtp.corp.redhat.com (Postfix) with ESMTP id 23F2462671; Wed, 8 May 2019 08:04:20 +0000 (UTC) From: Baoquan He To: linux-kernel@vger.kernel.org Cc: x86@kernel.org, tglx@linutronix.de, mingo@kernel.org, bp@alien8.de, hpa@zytor.com, kirill.shutemov@linux.intel.com, keescook@chromium.org, Baoquan He Subject: [PATCH v4] x86/mm/KASLR: Fix the size of vmemmap section Date: Wed, 8 May 2019 16:04:17 +0800 Message-Id: <20190508080417.15074-1-bhe@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Wed, 08 May 2019 08:04:24 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org kernel_randomize_memory() hardcodes the size of vmemmap section as 1 TB, to support the maximum amount of system RAM in 4-level paging mode, 64 TB. However, 1 TB is not enough for vmemmap in 5-level paging mode. Assuming the size of struct page is 64 Bytes, to support 4 PB system RAM in 5-level, 64 TB of vmemmap area is needed. The wrong hardcoding may cause vmemmap stamping into the following cpu_entry_area section, if KASLR puts vmemmap very close to cpu_entry_area , and the actual area of vmemmap is much bigger than 1 TB. So here calculate the actual size of vmemmap region, then align up to 1 TB boundary. In 4-level it's always 1 TB. In 5-level it's adjusted on demand. The current code reserves 0.5 PB for vmemmap in 5-level. In this new way, the left space can be saved to join randomization to increase the entropy. Signed-off-by: Baoquan He Acked-by: Kirill A. Shutemov Reviewed-by: Kees Cook --- v3->v4: Fix the incorrect style of code comment; Add ack tags from Kirill and Kees. v3 discussion is here: http://lkml.kernel.org/r/20190422091045.GB3584@localhost.localdomain arch/x86/mm/kaslr.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c index dc3f058bdf9b..c0eedb85a92f 100644 --- a/arch/x86/mm/kaslr.c +++ b/arch/x86/mm/kaslr.c @@ -52,7 +52,7 @@ static __initdata struct kaslr_memory_region { } kaslr_regions[] = { { &page_offset_base, 0 }, { &vmalloc_base, 0 }, - { &vmemmap_base, 1 }, + { &vmemmap_base, 0 }, }; /* Get size in bytes used by the memory region */ @@ -78,6 +78,7 @@ void __init kernel_randomize_memory(void) unsigned long rand, memory_tb; struct rnd_state rand_state; unsigned long remain_entropy; + unsigned long vmemmap_size; vaddr_start = pgtable_l5_enabled() ? __PAGE_OFFSET_BASE_L5 : __PAGE_OFFSET_BASE_L4; vaddr = vaddr_start; @@ -109,6 +110,14 @@ void __init kernel_randomize_memory(void) if (memory_tb < kaslr_regions[0].size_tb) kaslr_regions[0].size_tb = memory_tb; + /* + * Calculate how many TB vmemmap region needs, and aligned to + * 1TB boundary. + */ + vmemmap_size = (kaslr_regions[0].size_tb << (TB_SHIFT - PAGE_SHIFT)) * + sizeof(struct page); + kaslr_regions[2].size_tb = DIV_ROUND_UP(vmemmap_size, 1UL << TB_SHIFT); + /* Calculate entropy available between regions */ remain_entropy = vaddr_end - vaddr_start; for (i = 0; i < ARRAY_SIZE(kaslr_regions); i++) -- 2.17.2