From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755195AbbCaUL5 (ORCPT ); Tue, 31 Mar 2015 16:11:57 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:39310 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753452AbbCaTtu (ORCPT ); Tue, 31 Mar 2015 15:49:50 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Konstantin Khlebnikov , Andrew Morton , Linus Torvalds , Kamal Mostafa Subject: [PATCH 3.13.y-ckt 088/143] proc/pagemap: walk page tables under pte lock Date: Tue, 31 Mar 2015 12:47:33 -0700 Message-Id: <1427831308-1854-89-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1427831308-1854-1-git-send-email-kamal@canonical.com> References: <1427831308-1854-1-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-ckt18 -stable review patch. If anyone has any objections, please let me know. ------------------ 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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Kamal Mostafa --- fs/proc/task_mmu.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 396a204..903c19f 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -992,7 +992,7 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, 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' */ @@ -1053,15 +1053,19 @@ static int pagemap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, 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; -- 1.9.1