From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ram Pai Subject: Re: [RFC v5 12/38] mm: ability to disable execute permission on a key at creation Date: Tue, 11 Jul 2017 15:19:30 -0700 Message-ID: <20170711221929.GC5542@ram.oc3035372033.ibm.com> References: <1499289735-14220-1-git-send-email-linuxram@us.ibm.com> <1499289735-14220-13-git-send-email-linuxram@us.ibm.com> <3bd2ffd4-33ad-ce23-3db1-d1292e69ca9b@intel.com> <1499808577.2865.30.camel@kernel.crashing.org> <20170711215105.GA5542@ram.oc3035372033.ibm.com> <1499810936.2865.32.camel@kernel.crashing.org> Reply-To: Ram Pai Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1499810936.2865.32.camel@kernel.crashing.org> Sender: owner-linux-mm@kvack.org To: Benjamin Herrenschmidt Cc: linux-arch@vger.kernel.org, corbet@lwn.net, arnd@arndb.de, linux-mm@kvack.org, x86@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Dave Hansen , mingo@redhat.com, paulus@samba.org, aneesh.kumar@linux.vnet.ibm.com, linux-kselftest@vger.kernel.org, akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org, khandual@linux.vnet.ibm.com List-Id: linux-arch.vger.kernel.org On Wed, Jul 12, 2017 at 08:08:56AM +1000, Benjamin Herrenschmidt wrote: > On Tue, 2017-07-11 at 14:51 -0700, Ram Pai wrote: > > On Wed, Jul 12, 2017 at 07:29:37AM +1000, Benjamin Herrenschmidt wrote: > > > On Tue, 2017-07-11 at 11:11 -0700, Dave Hansen wrote: > > > > On 07/05/2017 02:21 PM, Ram Pai wrote: > > > > > Currently sys_pkey_create() provides the ability to disable read > > > > > and write permission on the key, at creation. powerpc has the > > > > > hardware support to disable execute on a pkey as well.This patch > > > > > enhances the interface to let disable execute at key creation > > > > > time. x86 does not allow this. Hence the next patch will add > > > > > ability in x86 to return error if PKEY_DISABLE_EXECUTE is > > > > > specified. > > > > > > That leads to the question... How do you tell userspace. > > > > > > (apologies if I missed that in an existing patch in the series) > > > > > > How do we inform userspace of the key capabilities ? There are at least > > > two things userspace may want to know already: > > > > > > - What protection bits are supported for a key > > > > the userspace is the one which allocates the keys and enables/disables the > > protection bits on the key. the kernel is just a facilitator. Now if the > > use space wants to know the current permissions on a given key, it can > > just read the AMR/PKRU register on powerpc/intel respectively. > > You misunderstand. How does userspace knows on a given system whether > execute permission control is supported for keys ? Ah..sorry. did not catch that part. Yes the current patch set does not make that information available. The indirect way of find this out is, to try to allocate a key with execute-disable permission and decide based on the pass/fail status. we can expose that information through a procfs/sysfs interface. RP -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:41948 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756098AbdGKWTs (ORCPT ); Tue, 11 Jul 2017 18:19:48 -0400 Received: from pps.filterd (m0098414.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id v6BMJUsk066975 for ; Tue, 11 Jul 2017 18:19:47 -0400 Received: from e37.co.us.ibm.com (e37.co.us.ibm.com [32.97.110.158]) by mx0b-001b2d01.pphosted.com with ESMTP id 2bn0mxqc5x-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Tue, 11 Jul 2017 18:19:47 -0400 Received: from localhost by e37.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 11 Jul 2017 16:19:46 -0600 Date: Tue, 11 Jul 2017 15:19:30 -0700 From: Ram Pai Subject: Re: [RFC v5 12/38] mm: ability to disable execute permission on a key at creation Reply-To: Ram Pai References: <1499289735-14220-1-git-send-email-linuxram@us.ibm.com> <1499289735-14220-13-git-send-email-linuxram@us.ibm.com> <3bd2ffd4-33ad-ce23-3db1-d1292e69ca9b@intel.com> <1499808577.2865.30.camel@kernel.crashing.org> <20170711215105.GA5542@ram.oc3035372033.ibm.com> <1499810936.2865.32.camel@kernel.crashing.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1499810936.2865.32.camel@kernel.crashing.org> Message-ID: <20170711221929.GC5542@ram.oc3035372033.ibm.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Benjamin Herrenschmidt Cc: linux-arch@vger.kernel.org, corbet@lwn.net, arnd@arndb.de, linux-mm@kvack.org, x86@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Dave Hansen , mingo@redhat.com, paulus@samba.org, aneesh.kumar@linux.vnet.ibm.com, linux-kselftest@vger.kernel.org, akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org, khandual@linux.vnet.ibm.com Message-ID: <20170711221930.zDVlcsTrbqkqB57vrP6-XFo5RZ2mLnqe8dpidYd_RPM@z> On Wed, Jul 12, 2017 at 08:08:56AM +1000, Benjamin Herrenschmidt wrote: > On Tue, 2017-07-11 at 14:51 -0700, Ram Pai wrote: > > On Wed, Jul 12, 2017 at 07:29:37AM +1000, Benjamin Herrenschmidt wrote: > > > On Tue, 2017-07-11 at 11:11 -0700, Dave Hansen wrote: > > > > On 07/05/2017 02:21 PM, Ram Pai wrote: > > > > > Currently sys_pkey_create() provides the ability to disable read > > > > > and write permission on the key, at creation. powerpc has the > > > > > hardware support to disable execute on a pkey as well.This patch > > > > > enhances the interface to let disable execute at key creation > > > > > time. x86 does not allow this. Hence the next patch will add > > > > > ability in x86 to return error if PKEY_DISABLE_EXECUTE is > > > > > specified. > > > > > > That leads to the question... How do you tell userspace. > > > > > > (apologies if I missed that in an existing patch in the series) > > > > > > How do we inform userspace of the key capabilities ? There are at least > > > two things userspace may want to know already: > > > > > > - What protection bits are supported for a key > > > > the userspace is the one which allocates the keys and enables/disables the > > protection bits on the key. the kernel is just a facilitator. Now if the > > use space wants to know the current permissions on a given key, it can > > just read the AMR/PKRU register on powerpc/intel respectively. > > You misunderstand. How does userspace knows on a given system whether > execute permission control is supported for keys ? Ah..sorry. did not catch that part. Yes the current patch set does not make that information available. The indirect way of find this out is, to try to allocate a key with execute-disable permission and decide based on the pass/fail status. we can expose that information through a procfs/sysfs interface. RP