From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755232AbdL1SEU (ORCPT ); Thu, 28 Dec 2017 13:04:20 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:59100 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754194AbdL1RNZ (ORCPT ); Thu, 28 Dec 2017 12:13:25 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Martin Schwidefsky" , "Gerald Schaefer" Date: Thu, 28 Dec 2017 17:05:44 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 016/204] s390/mm: fix write access check in gup_huge_pmd() In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.52-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Gerald Schaefer commit ba385c0594e723d41790ecfb12c610e6f90c7785 upstream. The check for the _SEGMENT_ENTRY_PROTECT bit in gup_huge_pmd() is the wrong way around. It must not be set for write==1, and not be checked for write==0. Fix this similar to how it was fixed for ptes long time ago in commit 25591b070336 ("[S390] fix get_user_pages_fast"). One impact of this bug would be unnecessarily using the gup slow path for write==0 on r/w mappings. A potentially more severe impact would be that gup_huge_pmd() will succeed for write==1 on r/o mappings. Signed-off-by: Gerald Schaefer Signed-off-by: Martin Schwidefsky [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings --- arch/s390/mm/gup.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) --- a/arch/s390/mm/gup.c +++ b/arch/s390/mm/gup.c @@ -51,13 +51,12 @@ static inline int gup_pte_range(pmd_t *p static inline int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned long addr, unsigned long end, int write, struct page **pages, int *nr) { - unsigned long mask, result; struct page *head, *page, *tail; + unsigned long mask; int refs; - result = write ? 0 : _SEGMENT_ENTRY_PROTECT; - mask = result | _SEGMENT_ENTRY_INVALID; - if ((pmd_val(pmd) & mask) != result) + mask = (write ? _SEGMENT_ENTRY_PROTECT : 0) | _SEGMENT_ENTRY_INVALID; + if ((pmd_val(pmd) & mask) != 0) return 0; VM_BUG_ON(!pfn_valid(pmd_val(pmd) >> PAGE_SHIFT));