From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:42997 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757417AbbKFRSO (ORCPT ); Fri, 6 Nov 2015 12:18:14 -0500 Subject: Patch "thp: use is_zero_pfn() only after pte_present() check" has been added to the 4.2-stable tree To: minchan@kernel.org, aarcange@redhat.com, akpm@linux-foundation.org, gregkh@linuxfoundation.org, hughd@google.com, kirill.shutemov@linux.intel.com, mgorman@suse.de, riel@redhat.com, torvalds@linux-foundation.org, vbabka@suse.cz Cc: , From: Date: Fri, 06 Nov 2015 09:18:10 -0800 Message-ID: <144683029034130@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: use is_zero_pfn() only after pte_present() check to the 4.2-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-use-is_zero_pfn-only-after-pte_present-check.patch and it can be found in the queue-4.2 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 47aee4d8e314384807e98b67ade07f6da476aa75 Mon Sep 17 00:00:00 2001 From: Minchan Kim Date: Thu, 22 Oct 2015 13:32:19 -0700 Subject: thp: use is_zero_pfn() only after pte_present() check From: Minchan Kim commit 47aee4d8e314384807e98b67ade07f6da476aa75 upstream. Use is_zero_pfn() on pteval only after pte_present() check on pteval (It might be better idea to introduce is_zero_pte() which checks pte_present() first). Otherwise when working on a swap or migration entry and if pte_pfn's result is equal to zero_pfn by chance, we lose user's data in __collapse_huge_page_copy(). So if you're unlucky, the application segfaults and finally you could see below message on exit: BUG: Bad rss-counter state mm:ffff88007f099300 idx:2 val:3 Fixes: ca0984caa823 ("mm: incorporate zero pages into transparent huge pages") Signed-off-by: Minchan Kim Reviewed-by: Andrea Arcangeli Acked-by: Kirill A. Shutemov Cc: Mel Gorman Acked-by: Vlastimil Babka Cc: Hugh Dickins Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/huge_memory.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2132,7 +2132,8 @@ static int __collapse_huge_page_isolate( for (_pte = pte; _pte < pte+HPAGE_PMD_NR; _pte++, address += PAGE_SIZE) { pte_t pteval = *_pte; - if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) { + if (pte_none(pteval) || (pte_present(pteval) && + is_zero_pfn(pte_pfn(pteval)))) { if (++none_or_zero <= khugepaged_max_ptes_none) continue; else Patches currently in stable-queue which might be from minchan@kernel.org are queue-4.2/thp-use-is_zero_pfn-only-after-pte_present-check.patch