From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 41vtHr1WN1zF0hg for ; Wed, 22 Aug 2018 00:25:27 +1000 (AEST) Received: from pps.filterd (m0098414.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w7LEJF7c070605 for ; Tue, 21 Aug 2018 10:25:25 -0400 Received: from e06smtp02.uk.ibm.com (e06smtp02.uk.ibm.com [195.75.94.98]) by mx0b-001b2d01.pphosted.com with ESMTP id 2m0kp92dkx-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 21 Aug 2018 10:25:25 -0400 Received: from localhost by e06smtp02.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 21 Aug 2018 15:25:23 +0100 From: "Aneesh Kumar K.V" To: Christophe Leroy , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , aneesh.kumar@linux.vnet.ibm.com Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] powerpc/nohash: fix pte_access_permitted() In-Reply-To: <8097a1d32403ea47d076803e9070869badfe24bc.1534856426.git.christophe.leroy@c-s.fr> References: <8097a1d32403ea47d076803e9070869badfe24bc.1534856426.git.christophe.leroy@c-s.fr> Date: Tue, 21 Aug 2018 19:55:17 +0530 MIME-Version: 1.0 Content-Type: text/plain Message-Id: <87eferg5ki.fsf@linux.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Christophe Leroy writes: > Commit 5769beaf180a8 ("powerpc/mm: Add proper pte access check helper > for other platforms") replaced generic pte_access_permitted() by an > arch specific one. > > The generic one is defined as > (pte_present(pte) && (!(write) || pte_write(pte))) > > The arch specific one is open coded checking that _PAGE_USER and > _PAGE_WRITE (_PAGE_RW) flags are set, but lacking to check that > _PAGE_RO and _PAGE_PRIVILEGED are unset, leading to a useless test > on targets like the 8xx which defines _PAGE_RW and _PAGE_USER as 0. > > Commit 5fa5b16be5b31 ("powerpc/mm/hugetlb: Use pte_access_permitted > for hugetlb access check") replaced some tests performed with > pte helpers by a call to pte_access_permitted(), leading to the same > issue. > > This patch rewrites powerpc/nohash pte_access_permitted() > using pte helpers. > Thanks for fixing this. I should have used the helper instead of opencoding it on nohash platforms. This is another reason why I was also suggesting we should avoid consolidating pte accessors across platforms and user accessors instead of opencoding. https://lore.kernel.org/lkml/87lgcusc6z.fsf@linux.vnet.ibm.com/T/#u Reviewed-by: Aneesh Kumar K.V > Fixes: 5769beaf180a8 ("powerpc/mm: Add proper pte access check helper for other platforms") > Fixes: 5fa5b16be5b31 ("powerpc/mm/hugetlb: Use pte_access_permitted for hugetlb access check") > Cc: stable@vger.kernel.org # v4.15+ > Signed-off-by: Christophe Leroy > --- > arch/powerpc/include/asm/nohash/pgtable.h | 9 +++------ > 1 file changed, 3 insertions(+), 6 deletions(-) > > diff --git a/arch/powerpc/include/asm/nohash/pgtable.h b/arch/powerpc/include/asm/nohash/pgtable.h > index 2160be2e4339..b321c82b3624 100644 > --- a/arch/powerpc/include/asm/nohash/pgtable.h > +++ b/arch/powerpc/include/asm/nohash/pgtable.h > @@ -51,17 +51,14 @@ static inline int pte_present(pte_t pte) > #define pte_access_permitted pte_access_permitted > static inline bool pte_access_permitted(pte_t pte, bool write) > { > - unsigned long pteval = pte_val(pte); > /* > * A read-only access is controlled by _PAGE_USER bit. > * We have _PAGE_READ set for WRITE and EXECUTE > */ > - unsigned long need_pte_bits = _PAGE_PRESENT | _PAGE_USER; > - > - if (write) > - need_pte_bits |= _PAGE_WRITE; > + if (!pte_present(pte) || !pte_user(pte) || !pte_read(pte)) > + return false; > > - if ((pteval & need_pte_bits) != need_pte_bits) > + if (write && !pte_write(pte)) > return false; > > return true; > -- > 2.13.3