Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758152AbaJIVQl (ORCPT ); Thu, 9 Oct 2014 17:16:41 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:59693 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757949AbaJIVLz (ORCPT ); Thu, 9 Oct 2014 17:11:55 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Mel Gorman , Linus Torvalds , Kamal Mostafa Subject: [PATCH 3.13 154/163] mm: migrate: Close race between migration completion and mprotect Date: Thu, 9 Oct 2014 14:02:59 -0700 Message-Id: <1412888588-26755-155-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1412888588-26755-1-git-send-email-kamal@canonical.com> References: <1412888588-26755-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.13 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.13.11.9 -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: Kamal Mostafa --- mm/migrate.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/mm/migrate.c b/mm/migrate.c index 9194375..62047f8 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -164,8 +164,11 @@ static int remove_migration_pte(struct page *new, struct vm_area_struct *vma, 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); -- 1.9.1 -- 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/