From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:39883 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751245AbbDZLrb (ORCPT ); Sun, 26 Apr 2015 07:47:31 -0400 Subject: Patch "proc/pagemap: walk page tables under pte lock" has been added to the 3.14-stable tree To: khlebnikov@yandex-team.ru, a.ryabinin@samsung.com, akpm@linux-foundation.org, gorcunov@openvz.org, gregkh@linuxfoundation.org, kirill.shutemov@linux.intel.com, n-horiguchi@ah.jp.nec.com, stable@vger.kernel.org, torvalds@linux-foundation.org Cc: , From: Date: Sun, 26 Apr 2015 13:47:19 +0200 Message-ID: <1430048839347@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled proc/pagemap: walk page tables under pte lock to the 3.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: proc-pagemap-walk-page-tables-under-pte-lock.patch and it can be found in the queue-3.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 05fbf357d94152171bc50f8a369390f1f16efd89 Mon Sep 17 00:00:00 2001 From: Konstantin Khlebnikov Date: Wed, 11 Feb 2015 15:27:31 -0800 Subject: proc/pagemap: walk page tables under pte lock From: Konstantin Khlebnikov commit 05fbf357d94152171bc50f8a369390f1f16efd89 upstream. Lockless access to pte in pagemap_pte_range() might race with page migration and trigger BUG_ON(!PageLocked()) in migration_entry_to_page(): CPU A (pagemap) CPU B (migration) lock_page() try_to_unmap(page, TTU_MIGRATION...) make_migration_entry() set_pte_at() pte_to_pagemap_entry() remove_migration_ptes() unlock_page() if(is_migration_entry()) migration_entry_to_page() BUG_ON(!PageLocked(page)) Also lockless read might be non-atomic if pte is larger than wordsize. Other pte walkers (smaps, numa_maps, clear_refs) already lock ptes. Fixes: 052fb0d635df ("proc: report file/anon bit in /proc/pid/pagemap") Signed-off-by: Konstantin Khlebnikov Reported-by: Andrey Ryabinin Reviewed-by: Cyrill Gorcunov Acked-by: Naoya Horiguchi Acked-by: Kirill A. Shutemov Cc: [3.5+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- fs/proc/task_mmu.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -993,7 +993,7 @@ static int pagemap_pte_range(pmd_t *pmd, struct vm_area_struct *vma; struct pagemapread *pm = walk->private; spinlock_t *ptl; - pte_t *pte; + pte_t *pte, *orig_pte; int err = 0; /* find the first VMA at or above 'addr' */ @@ -1054,15 +1054,19 @@ static int pagemap_pte_range(pmd_t *pmd, BUG_ON(is_vm_hugetlb_page(vma)); /* Addresses in the VMA. */ - for (; addr < min(end, vma->vm_end); addr += PAGE_SIZE) { + orig_pte = pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); + for (; addr < min(end, vma->vm_end); pte++, addr += PAGE_SIZE) { pagemap_entry_t pme; - pte = pte_offset_map(pmd, addr); + pte_to_pagemap_entry(&pme, pm, vma, addr, *pte); - pte_unmap(pte); err = add_to_pagemap(addr, &pme, pm); if (err) - return err; + break; } + pte_unmap_unlock(orig_pte, ptl); + + if (err) + return err; if (addr == end) break; Patches currently in stable-queue which might be from khlebnikov@yandex-team.ru are queue-3.14/proc-pagemap-walk-page-tables-under-pte-lock.patch