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=-9.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,USER_AGENT_NEOMUTT 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 AC1F3C43219 for ; Mon, 29 Apr 2019 04:29:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 731472075E for ; Mon, 29 Apr 2019 04:29:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=shutemov-name.20150623.gappssmtp.com header.i=@shutemov-name.20150623.gappssmtp.com header.b="sXz89DjZ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726585AbfD2E3j (ORCPT ); Mon, 29 Apr 2019 00:29:39 -0400 Received: from mail-yw1-f65.google.com ([209.85.161.65]:43482 "EHLO mail-yw1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726073AbfD2E3i (ORCPT ); Mon, 29 Apr 2019 00:29:38 -0400 Received: by mail-yw1-f65.google.com with SMTP id w196so3245581ywd.10 for ; Sun, 28 Apr 2019 21:29:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=shutemov-name.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=65wEfYgxWk51SngzsWDGGLkeNi4aWWYP9+RVNbeVfio=; b=sXz89DjZyDhE7dpaYT8JxNeAH5uG99lZt0sZ/sJpDXkg0fUZUUB/AHEzHxuwRLTHet nV/x/MlEJ7VMk/avI5WCIVBqIq+G6FPTrgMvgnIG/Vc8Vo7oSbIB94OvMQvtW2aKQYA+ vXyEi/jovC3n6ZkYqBxDggU/OgA2KXdeSRYL25CX2/fkjrUj6OEweFCfVSneo3DHKCK3 swURCCq+ZS0NSHQpjxo4X6a51QGF96RYnwy9V5hLpCMCRq3w5OgMTC0C1VCHrBM2NYdO yHirmlFK4vy2EmZFZ6bn2Cy7BxGC0ePTo3yadbCv1fxlCutQHUiX7+gJP27Dp6GAayOL faFw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=65wEfYgxWk51SngzsWDGGLkeNi4aWWYP9+RVNbeVfio=; b=rL5i+cra6KRamQrnb2YR3vprIcXYXrS6WX32RvZcCnO1QfVHHVZY3KuwBdGK3jIiQU G5Pqp2D5sOI9NeNbGObfqut8OL9Uv1bxuz//O8hsMga1gvdY4qC5eFKJ/mOiBMTxSWCz bGShJ0UjlIgjYC4vVYl6u8G0gOHyITnABq3yW/KOLoizI6SZJ7leLbgSKxkPCgeasCfQ ejOY5kN5pDs4PTPpXol1AsVfTseN+CEJH0bWnv+mB9WMMos+SBMrZAodvveveaOeNV7h +4Pqhrc/gQrBVcJj9uTuceMtboWZSOB7foXA7qczK/rD8+Nq68DWdg/pENhNoh/JhDvG LV4g== X-Gm-Message-State: APjAAAUhUhMN7CjeE+G7pXuf2u94NF3W49Ear6YGRVDXH8d+s4OR8s0l A4QdpQqfTzZW6rpEoZYEK+f8Sg== X-Google-Smtp-Source: APXvYqwailRrO/Y8SgtDcG0XT1V+s+aZGQSVtaE1FynPC7PnKdorrn/A6pWmnDHW/MPjDhjfovR8tg== X-Received: by 2002:a81:a103:: with SMTP id y3mr37542865ywg.136.1556512177964; Sun, 28 Apr 2019 21:29:37 -0700 (PDT) Received: from kshutemo-mobl1.localdomain (adsl-173-228-226-134.prtc.net. [173.228.226.134]) by smtp.gmail.com with ESMTPSA id o11sm4779429ywj.15.2019.04.28.21.29.35 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 28 Apr 2019 21:29:36 -0700 (PDT) Received: by kshutemo-mobl1.localdomain (Postfix, from userid 1000) id 06DCB30008A; Sun, 28 Apr 2019 21:54:09 +0300 (+03) Date: Sun, 28 Apr 2019 21:54:08 +0300 From: "Kirill A. Shutemov" To: Baoquan He Cc: linux-kernel@vger.kernel.org, x86@kernel.org, tglx@linutronix.de, mingo@kernel.org, bp@alien8.de, hpa@zytor.com, kirill.shutemov@linux.intel.com, keescook@chromium.org, peterz@infradead.org, thgarnie@google.com, herbert@gondor.apana.org.au, mike.travis@hpe.com, frank.ramsay@hpe.com, yamada.masahiro@socionext.com Subject: Re: [PATCH v3 RESEND 2/2] x86/mm/KASLR: Fix the size of vmemmap section Message-ID: <20190428185408.macoxstmy5awsago@kshutemo-mobl1> References: <20190414072804.12560-1-bhe@redhat.com> <20190414072804.12560-3-bhe@redhat.com> <20190422091045.GB3584@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190422091045.GB3584@localhost.localdomain> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 22, 2019 at 05:10:45PM +0800, 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 method, > the left space can be saved to join randomization to increase the entropy. > > Signed-off-by: Baoquan He > --- > v2->v3: > Fix typo Boris pointed out. > > 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 387d4ed25d7c..4679a0075048 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; > > + /** Nit: that is weird style for inline comment. > + * 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); Hm. Don't we need to take into account alignment requirements for struct page here? I'm worried about some exotic debug kernel config where sizeof(struct page) doesn't satify __alignof__(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++) -- Kirill A. Shutemov