From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751623AbeCPVsd (ORCPT ); Fri, 16 Mar 2018 17:48:33 -0400 Received: from mga12.intel.com ([192.55.52.136]:52828 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751233AbeCPVsb (ORCPT ); Fri, 16 Mar 2018 17:48:31 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.48,317,1517904000"; d="scan'208";a="183503467" Subject: [PATCH 1/3] x86, pkeys: do not special case protection key 0 To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, Dave Hansen , linuxram@us.ibm.com, tglx@linutronix.de, dave.hansen@intel.com, mpe@ellerman.id.au, mingo@kernel.org, akpm@linux-foundation.org, shuah@kernel.org From: Dave Hansen Date: Fri, 16 Mar 2018 14:46:56 -0700 References: <20180316214654.895E24EC@viggo.jf.intel.com> In-Reply-To: <20180316214654.895E24EC@viggo.jf.intel.com> Message-Id: <20180316214656.0E059008@viggo.jf.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Dave Hansen mm_pkey_is_allocated() treats pkey 0 as unallocated. That is inconsistent with the manpages, and also inconsistent with mm->context.pkey_allocation_map. Stop special casing it and only disallow values that are actually bad (< 0). The end-user visible effect of this is that you can now use mprotect_pkey() to set pkey=0. This is a bit nicer than what Ram proposed because it is simpler and removes special-casing for pkey 0. On the other hand, it does allow applciations to pkey_free() pkey-0, but that's just a silly thing to do, so we are not going to protect against it. Signed-off-by: Dave Hansen Cc: Ram Pai Cc: Thomas Gleixner Cc: Dave Hansen Cc: Michael Ellermen Cc: Ingo Molnar Cc: Andrew Morton p Cc: Shuah Khan --- b/arch/x86/include/asm/mmu_context.h | 2 +- b/arch/x86/include/asm/pkeys.h | 6 +++--- 2 files changed, 4 insertions(+), 4 deletions(-) diff -puN arch/x86/include/asm/mmu_context.h~x86-pkey-0-default-allocated arch/x86/include/asm/mmu_context.h --- a/arch/x86/include/asm/mmu_context.h~x86-pkey-0-default-allocated 2018-03-16 14:46:39.023285476 -0700 +++ b/arch/x86/include/asm/mmu_context.h 2018-03-16 14:46:39.028285476 -0700 @@ -191,7 +191,7 @@ static inline int init_new_context(struc #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS if (cpu_feature_enabled(X86_FEATURE_OSPKE)) { - /* pkey 0 is the default and always allocated */ + /* pkey 0 is the default and allocated implicitly */ mm->context.pkey_allocation_map = 0x1; /* -1 means unallocated or invalid */ mm->context.execute_only_pkey = -1; diff -puN arch/x86/include/asm/pkeys.h~x86-pkey-0-default-allocated arch/x86/include/asm/pkeys.h --- a/arch/x86/include/asm/pkeys.h~x86-pkey-0-default-allocated 2018-03-16 14:46:39.025285476 -0700 +++ b/arch/x86/include/asm/pkeys.h 2018-03-16 14:46:39.028285476 -0700 @@ -49,10 +49,10 @@ bool mm_pkey_is_allocated(struct mm_stru { /* * "Allocated" pkeys are those that have been returned - * from pkey_alloc(). pkey 0 is special, and never - * returned from pkey_alloc(). + * from pkey_alloc() or pkey 0 which is allocated + * implicitly when the mm is created. */ - if (pkey <= 0) + if (pkey < 0) return false; if (pkey >= arch_max_pkey()) return false; _