Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1948986AbdDYPLY (ORCPT ); Tue, 25 Apr 2017 11:11:24 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:54680 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1948859AbdDYPK0 (ORCPT ); Tue, 25 Apr 2017 11:10:26 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Martin Schwidefsky Subject: [PATCH 4.4 08/28] s390/mm: fix CMMA vs KSM vs others Date: Tue, 25 Apr 2017 16:08:39 +0100 Message-Id: <20170425150815.085058481@linuxfoundation.org> X-Mailer: git-send-email 2.12.2 In-Reply-To: <20170425150814.719042460@linuxfoundation.org> References: <20170425150814.719042460@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1251 Lines: 37 4.4-stable 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 Signed-off-by: Greg Kroah-Hartman --- 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 @@ -829,6 +829,8 @@ 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;