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=-8.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,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 62B42C10F12 for ; Mon, 15 Apr 2019 19:50:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2BEC320854 for ; Mon, 15 Apr 2019 19:50:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="OOqT3Caf" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728855AbfDOTuL (ORCPT ); Mon, 15 Apr 2019 15:50:11 -0400 Received: from mail.skyhub.de ([5.9.137.197]:55668 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728605AbfDOTuK (ORCPT ); Mon, 15 Apr 2019 15:50:10 -0400 Received: from zn.tnic (p4FED3D80.dip0.t-ipconnect.de [79.237.61.128]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 448EE1EC02AE; Mon, 15 Apr 2019 21:50:08 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1555357808; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=Ief1bSeBDooFjV+/QSkceSHzeIIB5ciAHxhEmjiNw7s=; b=OOqT3CafFcizE4FwSgROrgjYicpEKSTeoPegIba43hVDBRuZ+yVcdkLAM3u1F65ZY7LGCo 1D1kEN8ACAcX9nDk6TbwHoBm05SmhITXQy8F0HtvGmfzCn2X16b+Oo/3WeXL0Bv2k4ozYh NCf8bD3F+G7DhDsDgN3tM+UI4muJoNc= Date: Mon, 15 Apr 2019 21:47:55 +0200 From: Borislav Petkov To: Baoquan He , kirill@shutemov.name Cc: linux-kernel@vger.kernel.org, x86@kernel.org, tglx@linutronix.de, mingo@kernel.org, hpa@zytor.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 v2 RESEND 2/2] x86/mm/KASLR: Fix the size of vmemmap section Message-ID: <20190415194755.GJ29317@zn.tnic> References: <20190414072804.12560-1-bhe@redhat.com> <20190414072804.12560-3-bhe@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190414072804.12560-3-bhe@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Apr 14, 2019 at 03:28:04PM +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 methor, ^^^^^^^ Please introduce a spellchecker into your patch creation workflow. > the left space can be saved to join randomization to increase the entropy. > > Signed-off-by: Baoquan He > --- > 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; > > + /** > + * 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++) > -- Kirill, ack? -- Regards/Gruss, Boris. Good mailing practices for 400: avoid top-posting and trim the reply.