From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752655AbeCZRfi (ORCPT ); Mon, 26 Mar 2018 13:35:38 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:35632 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751684AbeCZRfh (ORCPT ); Mon, 26 Mar 2018 13:35:37 -0400 Date: Mon, 26 Mar 2018 10:35:23 -0700 From: Ram Pai To: Dave Hansen Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, tglx@linutronix.de, dave.hansen@intel.com, mpe@ellerman.id.au, mingo@kernel.org, akpm@linux-foundation.org, shuah@kernel.org Subject: Re: [PATCH 1/9] x86, pkeys: do not special case protection key 0 Reply-To: Ram Pai References: <20180323180903.33B17168@viggo.jf.intel.com> <20180323180905.B40984E6@viggo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180323180905.B40984E6@viggo.jf.intel.com> User-Agent: Mutt/1.5.20 (2009-12-10) X-TM-AS-GCONF: 00 x-cbid: 18032617-0040-0000-0000-000004271CAD X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18032617-0041-0000-0000-0000262A31C9 Message-Id: <20180326173522.GB5743@ram.oc3035372033.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2018-03-26_08:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=2 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1803260180 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 23, 2018 at 11:09:05AM -0700, Dave Hansen wrote: > > 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 2018-03-21 15:47:48.182198927 -0700 > +++ b/arch/x86/include/asm/mmu_context.h 2018-03-21 15:47:48.187198927 -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; In the second patch, you introduce DEFAULT_KEY. Maybe you should introduce here and express the above code as mm->context.pkey_allocation_map = (0x1 << DEFAULT_KEY); Incase your default key changes to something else, you are still good. > /* -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 2018-03-21 15:47:48.184198927 -0700 > +++ b/arch/x86/include/asm/pkeys.h 2018-03-21 15:47:48.188198927 -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; > _ -- Ram Pai