From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:50592 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752125AbdDRMur (ORCPT ); Tue, 18 Apr 2017 08:50:47 -0400 Subject: Patch "thp: fix MADV_DONTNEED vs. MADV_FREE race" has been added to the 4.9-stable tree To: kirill.shutemov@linux.intel.com, aarcange@redhat.com, akpm@linux-foundation.org, gregkh@linuxfoundation.org, hillf.zj@alibaba-inc.com, minchan@kernel.org, torvalds@linux-foundation.org Cc: , From: Date: Tue, 18 Apr 2017 14:50:25 +0200 Message-ID: <14925198251789@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 thp: fix MADV_DONTNEED vs. MADV_FREE race to the 4.9-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: thp-fix-madv_dontneed-vs.-madv_free-race.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 58ceeb6bec86d9140f9d91d71a710e963523d063 Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" Date: Thu, 13 Apr 2017 14:56:26 -0700 Subject: thp: fix MADV_DONTNEED vs. MADV_FREE race From: Kirill A. Shutemov commit 58ceeb6bec86d9140f9d91d71a710e963523d063 upstream. Both MADV_DONTNEED and MADV_FREE handled with down_read(mmap_sem). It's critical to not clear pmd intermittently while handling MADV_FREE to avoid race with MADV_DONTNEED: CPU0: CPU1: madvise_free_huge_pmd() pmdp_huge_get_and_clear_full() madvise_dontneed() zap_pmd_range() pmd_trans_huge(*pmd) == 0 (without ptl) // skip the pmd set_pmd_at(); // pmd is re-established It results in MADV_DONTNEED skipping the pmd, leaving it not cleared. It violates MADV_DONTNEED interface and can result is userspace misbehaviour. Basically it's the same race as with numa balancing in change_huge_pmd(), but a bit simpler to mitigate: we don't need to preserve dirty/young flags here due to MADV_FREE functionality. [kirill.shutemov@linux.intel.com: Urgh... Power is special again] Link: http://lkml.kernel.org/r/20170303102636.bhd2zhtpds4mt62a@black.fi.intel.com Link: http://lkml.kernel.org/r/20170302151034.27829-4-kirill.shutemov@linux.intel.com Signed-off-by: Kirill A. Shutemov Acked-by: Minchan Kim Cc: Minchan Kim Cc: Andrea Arcangeli Cc: Hillf Danton Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/huge_memory.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1380,8 +1380,7 @@ bool madvise_free_huge_pmd(struct mmu_ga deactivate_page(page); if (pmd_young(orig_pmd) || pmd_dirty(orig_pmd)) { - orig_pmd = pmdp_huge_get_and_clear_full(tlb->mm, addr, pmd, - tlb->fullmm); + pmdp_invalidate(vma, addr, pmd); orig_pmd = pmd_mkold(orig_pmd); orig_pmd = pmd_mkclean(orig_pmd); Patches currently in stable-queue which might be from kirill.shutemov@linux.intel.com are queue-4.9/thp-fix-madv_dontneed-vs-clear-soft-dirty-race.patch queue-4.9/thp-fix-madv_dontneed-vs.-madv_free-race.patch