From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752764AbdCAKo5 (ORCPT ); Wed, 1 Mar 2017 05:44:57 -0500 Received: from terminus.zytor.com ([65.50.211.136]:48460 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752331AbdCAKnE (ORCPT ); Wed, 1 Mar 2017 05:43:04 -0500 Date: Wed, 1 Mar 2017 01:57:36 -0800 From: tip-bot for Dave Hansen Message-ID: Cc: dave.hansen@linux.intel.com, hpa@zytor.com, mingo@kernel.org, tglx@linutronix.de, linux-kernel@vger.kernel.org Reply-To: dave.hansen@linux.intel.com, mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, tglx@linutronix.de In-Reply-To: <20170223222603.A022ED65@viggo.jf.intel.com> References: <20170223222603.A022ED65@viggo.jf.intel.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/urgent] x86/pkeys: Check against max pkey to avoid overflows Git-Commit-ID: 58ab9a088ddac4efe823471275859d64f735577e X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 58ab9a088ddac4efe823471275859d64f735577e Gitweb: http://git.kernel.org/tip/58ab9a088ddac4efe823471275859d64f735577e Author: Dave Hansen AuthorDate: Thu, 23 Feb 2017 14:26:03 -0800 Committer: Thomas Gleixner CommitDate: Wed, 1 Mar 2017 10:51:50 +0100 x86/pkeys: Check against max pkey to avoid overflows Kirill reported a warning from UBSAN about undefined behavior when using protection keys. He is running on hardware that actually has support for it, which is not widely available. The warning triggers because of very large shifts of integers when doing a pkey_free() of a large, invalid value. This happens because we never check that the pkey "fits" into the mm_pkey_allocation_map(). I do not believe there is any danger here of anything bad happening other than some aliasing issues where somebody could do: pkey_free(35); and the kernel would effectively execute: pkey_free(8); While this might be confusing to an app that was doing something stupid, it has to do something stupid and the effects are limited to the app shooting itself in the foot. Signed-off-by: Dave Hansen Cc: stable@vger.kernel.org Cc: linux-kselftest@vger.kernel.org Cc: shuah@kernel.org Cc: kirill.shutemov@linux.intel.com Link: http://lkml.kernel.org/r/20170223222603.A022ED65@viggo.jf.intel.com Signed-off-by: Thomas Gleixner --- arch/x86/include/asm/pkeys.h | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/arch/x86/include/asm/pkeys.h b/arch/x86/include/asm/pkeys.h index 34684ad..b3b09b9 100644 --- a/arch/x86/include/asm/pkeys.h +++ b/arch/x86/include/asm/pkeys.h @@ -46,6 +46,15 @@ extern int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey, static inline bool mm_pkey_is_allocated(struct mm_struct *mm, int pkey) { + /* + * "Allocated" pkeys are those that have been returned + * from pkey_alloc(). pkey 0 is special, and never + * returned from pkey_alloc(). + */ + if (pkey <= 0) + return false; + if (pkey >= arch_max_pkey()) + return false; return mm_pkey_allocation_map(mm) & (1U << pkey); } @@ -82,12 +91,6 @@ int mm_pkey_alloc(struct mm_struct *mm) static inline int mm_pkey_free(struct mm_struct *mm, int pkey) { - /* - * pkey 0 is special, always allocated and can never - * be freed. - */ - if (!pkey) - return -EINVAL; if (!mm_pkey_is_allocated(mm, pkey)) return -EINVAL;