Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753799AbdHKVNG (ORCPT ); Fri, 11 Aug 2017 17:13:06 -0400 Received: from mail-io0-f180.google.com ([209.85.223.180]:38092 "EHLO mail-io0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753295AbdHKVNF (ORCPT ); Fri, 11 Aug 2017 17:13:05 -0400 Date: Fri, 11 Aug 2017 15:13:02 -0600 From: Tycho Andersen To: Laura Abbott Cc: 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: <20170811211302.limmjv4rmq23b25b@smitten> References: <20170809200755.11234-1-tycho@docker.com> <20170809200755.11234-7-tycho@docker.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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: 2344 Lines: 72 Hi Laura, On Fri, Aug 11, 2017 at 10:25:14AM -0700, Laura Abbott wrote: > On 08/09/2017 01:07 PM, Tycho Andersen wrote: > > From: Juerg Haefliger > > > > XPFO (eXclusive Page Frame Ownership) doesn't support section mappings > > yet, so disable it if XPFO is turned on. > > > > Signed-off-by: Juerg Haefliger > > Tested-by: Tycho Andersen > > --- > > arch/arm64/mm/mmu.c | 14 +++++++++++++- > > 1 file changed, 13 insertions(+), 1 deletion(-) > > > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > > index f1eb15e0e864..38026b3ccb46 100644 > > --- a/arch/arm64/mm/mmu.c > > +++ b/arch/arm64/mm/mmu.c > > @@ -176,6 +176,18 @@ static void alloc_init_cont_pte(pmd_t *pmd, unsigned long addr, > > } while (addr = next, addr != end); > > } > > > > +static inline bool use_section_mapping(unsigned long addr, unsigned long next, > > + unsigned long phys) > > +{ > > + if (IS_ENABLED(CONFIG_XPFO)) > > + return false; > > + > > + if (((addr | next | phys) & ~SECTION_MASK) != 0) > > + return false; > > + > > + return true; > > +} > > + > > static void init_pmd(pud_t *pud, unsigned long addr, unsigned long end, > > phys_addr_t phys, pgprot_t prot, > > phys_addr_t (*pgtable_alloc)(void), int flags) > > @@ -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; /* * Take care not to create a writable alias for the Cheers, Tycho