Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752355AbdGPOHN (ORCPT ); Sun, 16 Jul 2017 10:07:13 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:43234 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751769AbdGPN56 (ORCPT ); Sun, 16 Jul 2017 09:57:58 -0400 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" , "Christian Borntraeger" Date: Sun, 16 Jul 2017 14:56:46 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 147/178] s390/mm: fix CMMA vs KSM vs others 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 Content-Length: 1276 Lines: 35 3.16.46-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Christian Borntraeger commit a8f60d1fadf7b8b54449fcc9d6b15248917478ba upstream. On heavy paging with KSM I see guest data corruption. Turns out that KSM will add pages to its tree, where the mapping return true for pte_unused (or might become as such later). KSM will unmap such pages and reinstantiate with different attributes (e.g. write protected or special, e.g. in replace_page or write_protect_page)). This uncovered a bug in our pagetable handling: We must remove the unused flag as soon as an entry becomes present again. Signed-of-by: Christian Borntraeger Signed-off-by: Martin Schwidefsky [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings --- arch/s390/include/asm/pgtable.h | 2 ++ 1 file changed, 2 insertions(+) --- a/arch/s390/include/asm/pgtable.h +++ b/arch/s390/include/asm/pgtable.h @@ -868,6 +868,8 @@ static inline void set_pte_at(struct mm_ { pgste_t pgste; + if (pte_present(entry)) + pte_val(entry) &= ~_PAGE_UNUSED; if (mm_has_pgste(mm)) { pgste = pgste_get_lock(ptep); pgste_val(pgste) &= ~_PGSTE_GPS_ZERO;