From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yw0-f200.google.com (mail-yw0-f200.google.com [209.85.161.200]) by kanga.kvack.org (Postfix) with ESMTP id 744026B0038 for ; Thu, 15 Sep 2016 13:41:48 -0400 (EDT) Received: by mail-yw0-f200.google.com with SMTP id t67so115070633ywg.3 for ; Thu, 15 Sep 2016 10:41:48 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id p126si1993676ybg.298.2016.09.15.10.41.47 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 15 Sep 2016 10:41:47 -0700 (PDT) From: Andrea Arcangeli Subject: [PATCH 1/2] mm: vm_page_prot: update with WRITE_ONCE/READ_ONCE Date: Thu, 15 Sep 2016 19:41:43 +0200 Message-Id: <1473961304-19370-2-git-send-email-aarcange@redhat.com> In-Reply-To: <1473961304-19370-1-git-send-email-aarcange@redhat.com> References: <1473961304-19370-1-git-send-email-aarcange@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: linux-mm@kvack.org, Rik van Riel , Hugh Dickins , Mel Gorman , Jan Vorlicek , Aditya Mandaleeka vma->vm_page_prot is read lockless from the rmap_walk, it may be updated concurrently and this prevents the risk of reading intermediate values. Signed-off-by: Andrea Arcangeli --- mm/huge_memory.c | 2 +- mm/migrate.c | 2 +- mm/mmap.c | 9 ++++++--- 3 files changed, 8 insertions(+), 5 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index cb95a83..995f8a1 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1566,7 +1566,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, if (soft_dirty) entry = pte_swp_mksoft_dirty(entry); } else { - entry = mk_pte(page + i, vma->vm_page_prot); + entry = mk_pte(page + i, READ_ONCE(vma->vm_page_prot)); entry = maybe_mkwrite(entry, vma); if (!write) entry = pte_wrprotect(entry); diff --git a/mm/migrate.c b/mm/migrate.c index 00167df..e49ccce 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -234,7 +234,7 @@ static int remove_migration_pte(struct page *new, struct vm_area_struct *vma, goto unlock; get_page(new); - pte = pte_mkold(mk_pte(new, vma->vm_page_prot)); + pte = pte_mkold(mk_pte(new, READ_ONCE(vma->vm_page_prot))); if (pte_swp_soft_dirty(*ptep)) pte = pte_mksoft_dirty(pte); diff --git a/mm/mmap.c b/mm/mmap.c index c34f643..1abf106 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -112,13 +112,16 @@ static pgprot_t vm_pgprot_modify(pgprot_t oldprot, unsigned long vm_flags) void vma_set_page_prot(struct vm_area_struct *vma) { unsigned long vm_flags = vma->vm_flags; + pgprot_t vm_page_prot; - vma->vm_page_prot = vm_pgprot_modify(vma->vm_page_prot, vm_flags); + vm_page_prot = vm_pgprot_modify(vma->vm_page_prot, vm_flags); if (vma_wants_writenotify(vma)) { vm_flags &= ~VM_SHARED; - vma->vm_page_prot = vm_pgprot_modify(vma->vm_page_prot, - vm_flags); + vm_page_prot = vm_pgprot_modify(vma->vm_page_prot, + vm_flags); } + /* remove_protection_ptes reads vma->vm_page_prot without mmap_sem */ + WRITE_ONCE(vma->vm_page_prot, vm_page_prot); } static unsigned long vm_mergeable __read_mostly; -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org