From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl0-f69.google.com (mail-pl0-f69.google.com [209.85.160.69]) by kanga.kvack.org (Postfix) with ESMTP id 611956B0005 for ; Fri, 9 Mar 2018 05:20:02 -0500 (EST) Received: by mail-pl0-f69.google.com with SMTP id 62-v6so4324016ply.4 for ; Fri, 09 Mar 2018 02:20:02 -0800 (PST) Received: from ozlabs.org (ozlabs.org. [2401:3900:2:1::2]) by mx.google.com with ESMTPS id v10-v6si583919ply.700.2018.03.09.02.20.00 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 09 Mar 2018 02:20:00 -0800 (PST) From: Michael Ellerman Subject: Re: [PATCH] x86, powerpc : pkey-mprotect must allow pkey-0 In-Reply-To: <1520583161-11741-1-git-send-email-linuxram@us.ibm.com> References: <1520583161-11741-1-git-send-email-linuxram@us.ibm.com> Date: Fri, 09 Mar 2018 21:19:53 +1100 Message-ID: <87lgf1v9di.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain Sender: owner-linux-mm@kvack.org List-ID: To: Ram Pai , mingo@redhat.com, akpm@linux-foundation.org Cc: linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, x86@kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, dave.hansen@intel.com, benh@kernel.crashing.org, paulus@samba.org, khandual@linux.vnet.ibm.com, aneesh.kumar@linux.vnet.ibm.com, bsingharora@gmail.com, hbabu@us.ibm.com, mhocko@kernel.org, bauerman@linux.vnet.ibm.com, ebiederm@xmission.com, corbet@lwn.net, arnd@arndb.de, fweimer@redhat.com, msuchanek@suse.com, Ulrich.Weigand@de.ibm.com Ram Pai writes: > Once an address range is associated with an allocated pkey, it cannot be > reverted back to key-0. There is no valid reason for the above behavior. On > the contrary applications need the ability to do so. Please explain this in much more detail. Is it an ABI change? And why did we just notice this? > The patch relaxes the restriction. > > Tested on powerpc and x86_64. Thanks, but please split the patch, one for each arch. cheers > diff --git a/arch/powerpc/include/asm/pkeys.h b/arch/powerpc/include/asm/pkeys.h > index 0409c80..3e8abe4 100644 > --- a/arch/powerpc/include/asm/pkeys.h > +++ b/arch/powerpc/include/asm/pkeys.h > @@ -101,10 +101,18 @@ static inline u16 pte_to_pkey_bits(u64 pteflags) > > static inline bool mm_pkey_is_allocated(struct mm_struct *mm, int pkey) > { > - /* A reserved key is never considered as 'explicitly allocated' */ > - return ((pkey < arch_max_pkey()) && > - !__mm_pkey_is_reserved(pkey) && > - __mm_pkey_is_allocated(mm, pkey)); > + /* pkey 0 is allocated by default. */ > + if (!pkey) > + return true; > + > + if (pkey < 0 || pkey >= arch_max_pkey()) > + return false; > + > + /* reserved keys are never allocated. */ > + if (__mm_pkey_is_reserved(pkey)) > + return false; > + > + return(__mm_pkey_is_allocated(mm, pkey)); > } > > extern void __arch_activate_pkey(int pkey); > @@ -150,7 +158,8 @@ static inline int mm_pkey_free(struct mm_struct *mm, int pkey) > if (static_branch_likely(&pkey_disabled)) > return -1; > > - if (!mm_pkey_is_allocated(mm, pkey)) > + /* pkey 0 cannot be freed */ > + if (!pkey || !mm_pkey_is_allocated(mm, pkey)) > return -EINVAL; > > /* > diff --git a/arch/x86/include/asm/pkeys.h b/arch/x86/include/asm/pkeys.h > index a0ba1ff..6ea7486 100644 > --- a/arch/x86/include/asm/pkeys.h > +++ b/arch/x86/include/asm/pkeys.h > @@ -52,7 +52,7 @@ bool mm_pkey_is_allocated(struct mm_struct *mm, int pkey) > * from pkey_alloc(). pkey 0 is special, and never > * returned from pkey_alloc(). > */ > - if (pkey <= 0) > + if (pkey < 0) > return false; > if (pkey >= arch_max_pkey()) > return false; > @@ -92,7 +92,8 @@ int mm_pkey_alloc(struct mm_struct *mm) > static inline > int mm_pkey_free(struct mm_struct *mm, int pkey) > { > - if (!mm_pkey_is_allocated(mm, pkey)) > + /* pkey 0 is special and can never be freed */ > + if (!pkey || !mm_pkey_is_allocated(mm, pkey)) > return -EINVAL; > > mm_set_pkey_free(mm, pkey); > -- > 1.8.3.1