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=-8.4 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT 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 D2AEFC04A6B for ; Wed, 8 May 2019 08:24:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AC54621019 for ; Wed, 8 May 2019 08:24:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726526AbfEHIYX (ORCPT ); Wed, 8 May 2019 04:24:23 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60560 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726521AbfEHIYW (ORCPT ); Wed, 8 May 2019 04:24:22 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 55ACB308620F; Wed, 8 May 2019 08:24:22 +0000 (UTC) Received: from localhost (ovpn-12-18.pek2.redhat.com [10.72.12.18]) by smtp.corp.redhat.com (Postfix) with ESMTPS id AE0F6600D4; Wed, 8 May 2019 08:24:21 +0000 (UTC) Date: Wed, 8 May 2019 16:24:18 +0800 From: Baoquan He To: linux-kernel@vger.kernel.org, stable@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 Subject: Re: [PATCH v4] x86/mm/KASLR: Fix the size of vmemmap section Message-ID: <20190508082418.GC24922@MiWiFi-R3L-srv> References: <20190508080417.15074-1-bhe@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190508080417.15074-1-bhe@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.42]); Wed, 08 May 2019 08:24:22 +0000 (UTC) Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On 05/08/19 at 04:04pm, Baoquan He wrote: > 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 I think this's worth noticing stable tree: Cc: stable@vger.kernel.org > --- > 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 >