Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752487AbdHNU2s (ORCPT ); Mon, 14 Aug 2017 16:28:48 -0400 Received: from mail-it0-f52.google.com ([209.85.214.52]:38519 "EHLO mail-it0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752412AbdHNU2q (ORCPT ); Mon, 14 Aug 2017 16:28:46 -0400 Date: Mon, 14 Aug 2017 14:28:44 -0600 From: Tycho Andersen To: Laura Abbott Cc: Mark Rutland , linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-hardening@lists.openwall.com, Marco Benatto , Juerg Haefliger Subject: Re: [kernel-hardening] [PATCH v5 06/10] arm64/mm: Disable section mappings if XPFO is enabled Message-ID: <20170814202844.f2ianjmwr3wl4bbh@smitten> References: <20170809200755.11234-1-tycho@docker.com> <20170809200755.11234-7-tycho@docker.com> <20170811211302.limmjv4rmq23b25b@smitten> <20170812111733.GA16374@remoulade> <20170814162219.h2lcmli677bx2lwh@smitten> <86105819-3ec6-e220-5ba3-787bbeecb6ba@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <86105819-3ec6-e220-5ba3-787bbeecb6ba@redhat.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1832 Lines: 52 On Mon, Aug 14, 2017 at 11:42:45AM -0700, Laura Abbott wrote: > On 08/14/2017 09:22 AM, Tycho Andersen wrote: > > On Sat, Aug 12, 2017 at 12:17:34PM +0100, Mark Rutland wrote: > >> Hi, > >> > >> On Fri, Aug 11, 2017 at 03:13:02PM -0600, Tycho Andersen wrote: > >>> On Fri, Aug 11, 2017 at 10:25:14AM -0700, Laura Abbott wrote: > >>>> On 08/09/2017 01:07 PM, Tycho Andersen wrote: > >>>>> @@ -190,7 +202,7 @@ static void init_pmd(pud_t *pud, unsigned long addr, unsigned long end, > >>>>> next = pmd_addr_end(addr, end); > >>>>> > >>>>> /* try section mapping first */ > >>>>> - if (((addr | next | phys) & ~SECTION_MASK) == 0 && > >>>>> + if (use_section_mapping(addr, next, phys) && > >>>>> (flags & NO_BLOCK_MAPPINGS) == 0) { > >>>>> pmd_set_huge(pmd, phys, prot); > >>>>> > >>>>> > >>>> > >>>> There is already similar logic to disable section mappings for > >>>> debug_pagealloc at the start of map_mem, can you take advantage > >>>> of that? > >>> > >>> You're suggesting something like this instead? Seems to work fine. > >>> > >>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > >>> index 38026b3ccb46..3b2c17bbbf12 100644 > >>> --- a/arch/arm64/mm/mmu.c > >>> +++ b/arch/arm64/mm/mmu.c > >>> @@ -434,6 +434,8 @@ static void __init map_mem(pgd_t *pgd) > >>> > >>> if (debug_pagealloc_enabled()) > >>> flags = NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS; > >>> + if (IS_ENABLED(CONFIG_XPFO)) > >>> + flags |= NO_BLOCK_MAPPINGS; > >>> > >> > >> IIUC, XPFO carves out individual pages just like DEBUG_PAGEALLOC, so you'll > >> also need NO_CONT_MAPPINGS. > > > > Yes, thanks! > > > > Tycho > > > > Setting NO_CONT_MAPPINGS fixes the TLB conflict aborts I was seeing > on my machine. Great, thanks for testing! I've also fixed the lookup_page_ext bug you noted in the other thread. Tycho