From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f198.google.com (mail-pf0-f198.google.com [209.85.192.198]) by kanga.kvack.org (Postfix) with ESMTP id 16E326B0006 for ; Fri, 27 Apr 2018 13:49:49 -0400 (EDT) Received: by mail-pf0-f198.google.com with SMTP id g15so2131070pfi.8 for ; Fri, 27 Apr 2018 10:49:49 -0700 (PDT) Received: from mga11.intel.com (mga11.intel.com. [192.55.52.93]) by mx.google.com with ESMTPS id u71-v6si1598409pgb.332.2018.04.27.10.49.47 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 27 Apr 2018 10:49:47 -0700 (PDT) Subject: [PATCH 1/9] x86, pkeys: do not special case protection key 0 From: Dave Hansen Date: Fri, 27 Apr 2018 10:45:28 -0700 References: <20180427174527.0031016C@viggo.jf.intel.com> In-Reply-To: <20180427174527.0031016C@viggo.jf.intel.com> Message-Id: <20180427174528.23748D52@viggo.jf.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, Dave Hansen , stable@vger.kernel.org, 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 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 Fixes: 58ab9a088dda ("x86/pkeys: Check against max pkey to avoid overflows") Cc: stable@kernel.org 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 2018-03-26 10:22:33.742170197 -0700 +++ b/arch/x86/include/asm/mmu_context.h 2018-03-26 10:22:33.747170197 -0700 @@ -192,7 +192,7 @@ 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 2018-03-26 10:22:33.744170197 -0700 +++ b/arch/x86/include/asm/pkeys.h 2018-03-26 10:22:33.747170197 -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; _