From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:48558 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753714AbcLBRMx (ORCPT ); Fri, 2 Dec 2016 12:12:53 -0500 Subject: Patch "thp: fix corner case of munlock() of PTE-mapped THPs" has been added to the 4.8-stable tree To: kirill.shutemov@linux.intel.com, aarcange@redhat.com, akpm@linux-foundation.org, aryabinin@virtuozzo.com, dvyukov@google.com, gregkh@linuxfoundation.org, koct9i@gmail.com, syzkaller@googlegroups.com, torvalds@linux-foundation.org Cc: , From: Date: Fri, 02 Dec 2016 18:11:32 +0100 Message-ID: <14806986929931@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 corner case of munlock() of PTE-mapped THPs to the 4.8-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-corner-case-of-munlock-of-pte-mapped-thps.patch and it can be found in the queue-4.8 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 655548bf6271b212cd1e4c259da9dbe616348d38 Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" Date: Wed, 30 Nov 2016 15:54:05 -0800 Subject: thp: fix corner case of munlock() of PTE-mapped THPs From: Kirill A. Shutemov commit 655548bf6271b212cd1e4c259da9dbe616348d38 upstream. The following program triggers BUG() in munlock_vma_pages_range(): // autogenerated by syzkaller (http://github.com/google/syzkaller) #include int main() { mmap((void*)0x20105000ul, 0xc00000ul, 0x2ul, 0x2172ul, -1, 0); mremap((void*)0x201fd000ul, 0x4000ul, 0xc00000ul, 0x3ul, 0x203f0000ul); return 0; } The test-case constructs the situation when munlock_vma_pages_range() finds PTE-mapped THP-head in the middle of page table and, by mistake, skips HPAGE_PMD_NR pages after that. As result, on the next iteration it hits the middle of PMD-mapped THP and gets upset seeing mlocked tail page. The solution is only skip HPAGE_PMD_NR pages if the THP was mlocked during munlock_vma_page(). It would guarantee that the page is PMD-mapped as we never mlock PTE-mapeed THPs. Fixes: e90309c9f772 ("thp: allow mlocked THP again") Link: http://lkml.kernel.org/r/20161115132703.7s7rrgmwttegcdh4@black.fi.intel.com Signed-off-by: Kirill A. Shutemov Reported-by: Dmitry Vyukov Cc: Konstantin Khlebnikov Cc: Andrey Ryabinin Cc: syzkaller Cc: Andrea Arcangeli Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/mlock.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) --- a/mm/mlock.c +++ b/mm/mlock.c @@ -190,10 +190,13 @@ unsigned int munlock_vma_page(struct pag */ spin_lock_irq(zone_lru_lock(zone)); - nr_pages = hpage_nr_pages(page); - if (!TestClearPageMlocked(page)) + if (!TestClearPageMlocked(page)) { + /* Potentially, PTE-mapped THP: do not skip the rest PTEs */ + nr_pages = 1; goto unlock_out; + } + nr_pages = hpage_nr_pages(page); __mod_zone_page_state(zone, NR_MLOCK, -nr_pages); if (__munlock_isolate_lru_page(page, true)) { Patches currently in stable-queue which might be from kirill.shutemov@linux.intel.com are queue-4.8/mm-thp-propagation-of-conditional-compilation-in-khugepaged.c.patch queue-4.8/mm-fix-false-positive-warn_on-in-truncate-invalidate-for-hugetlb.patch queue-4.8/thp-fix-corner-case-of-munlock-of-pte-mapped-thps.patch