Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932365AbaJGXnJ (ORCPT ); Tue, 7 Oct 2014 19:43:09 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:39510 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755495AbaJGXTq (ORCPT ); Tue, 7 Oct 2014 19:19:46 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Mel Gorman , Rik van Riel , Linus Torvalds Subject: [PATCH 3.16 06/26] mm: migrate: Close race between migration completion and mprotect Date: Tue, 7 Oct 2014 16:19:22 -0700 Message-Id: <20141007231848.680657180@linuxfoundation.org> X-Mailer: git-send-email 2.1.2 In-Reply-To: <20141007231848.487609292@linuxfoundation.org> References: <20141007231848.487609292@linuxfoundation.org> User-Agent: quilt/0.63-1 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 3.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mel Gorman commit d3cb8bf6081b8b7a2dabb1264fe968fd870fa595 upstream. A migration entry is marked as write if pte_write was true at the time the entry was created. The VMA protections are not double checked when migration entries are being removed as mprotect marks write-migration-entries as read. It means that potentially we take a spurious fault to mark PTEs write again but it's straight-forward. However, there is a race between write migrations being marked read and migrations finishing. This potentially allows a PTE to be write that should have been read. Close this race by double checking the VMA permissions using maybe_mkwrite when migration completes. [torvalds@linux-foundation.org: use maybe_mkwrite] Signed-off-by: Mel Gorman Acked-by: Rik van Riel Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/migrate.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/mm/migrate.c +++ b/mm/migrate.c @@ -146,8 +146,11 @@ static int remove_migration_pte(struct p pte = pte_mkold(mk_pte(new, vma->vm_page_prot)); if (pte_swp_soft_dirty(*ptep)) pte = pte_mksoft_dirty(pte); + + /* Recheck VMA as permissions can change since migration started */ if (is_write_migration_entry(entry)) - pte = pte_mkwrite(pte); + pte = maybe_mkwrite(pte, vma); + #ifdef CONFIG_HUGETLB_PAGE if (PageHuge(new)) { pte = pte_mkhuge(pte); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/