From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753476AbdF0SZN (ORCPT ); Tue, 27 Jun 2017 14:25:13 -0400 Received: from mail-lf0-f53.google.com ([209.85.215.53]:35160 "EHLO mail-lf0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753395AbdF0SYm (ORCPT ); Tue, 27 Jun 2017 14:24:42 -0400 MIME-Version: 1.0 In-Reply-To: <87lgodl6c8.fsf@e105922-lin.cambridge.arm.com> References: <20170624001738.GB7946@gmail.com> <20170624150824.GA19708@gmail.com> <20170627163734.6js4jkwkwlz6xwir@black.fi.intel.com> <87lgodl6c8.fsf@e105922-lin.cambridge.arm.com> From: Andrei Vagin Date: Tue, 27 Jun 2017 11:24:34 -0700 Message-ID: Subject: Re: linux-next: BUG: Bad page state in process ip6tables-save pfn:1499f4 To: Punit Agrawal Cc: "Kirill A. Shutemov" , Vlastimil Babka , Steve Capper , Andrew Morton , linux-mm@kvack.org, LKML , Stephen Rothwell , Cyrill Gorcunov Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 27, 2017 at 9:53 AM, Punit Agrawal wrote: > "Kirill A. Shutemov" writes: > >> On Tue, Jun 27, 2017 at 09:18:15AM +0200, Vlastimil Babka wrote: >>> On 06/24/2017 05:08 PM, Andrei Vagin wrote: >>> > On Fri, Jun 23, 2017 at 05:17:44PM -0700, Andrei Vagin wrote: >>> >> On Thu, Jun 22, 2017 at 11:21:03PM -0700, Andrei Vagin wrote: >>> >>> Hello, >>> >>> >>> >>> We run CRIU tests for linux-next and today they triggered a kernel >>> >>> bug. I want to mention that this kernel is built with kasan. This bug >>> >>> was triggered in travis-ci. I can't reproduce it on my host. Without >>> >>> kasan, kernel crashed but it is impossible to get a kernel log for >>> >>> this case. >>> >> >>> >> We use this tree >>> >> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/ >>> >> >>> >> This issue isn't reproduced on the akpm-base branch and >>> >> it is reproduced each time on the akpm branch. I didn't >>> >> have time today to bisect it, will do on Monday. >>> > >>> > c3aab7b2d4e8434d53bc81770442c14ccf0794a8 is the first bad commit >>> > >>> > commit c3aab7b2d4e8434d53bc81770442c14ccf0794a8 >>> > Merge: 849c34f 93a7379 >>> > Author: Stephen Rothwell >>> > Date: Fri Jun 23 16:40:07 2017 +1000 >>> > >>> > Merge branch 'akpm-current/current' >>> >>> Hm is it really the merge of mmotm itself and not one of the patches in >>> mmotm? >>> Anyway smells like THP, adding Kirill. >> >> Okay, it took a while to figure it out. > > I'm sorry you had to go chasing for this one again. > > I'd found the same issue while investigating an ltp failure on arm64[0] and > sent a fix[1]. The fix is effectively the same as your patch below. > > Andrew picked up the patch from v5 posting and I can see it in today's > next[2]. Our tests passed on today's next: https://travis-ci.org/avagin/criu/jobs/247377006 Thanks, Andrei > > > [0] http://lists.infradead.org/pipermail/linux-arm-kernel/2017-June/510318.html > [1] https://patchwork.kernel.org/patch/9766193/ > [2] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/mm/gup.c?h=next-20170627&id=d31945b5d4ab4490fb5f961dd5b066cc9f560eb3 > >> >> The bug is in patch "mm, gup: ensure real head page is ref-counted when >> using hugepages". We should look for a head *before* the loop. Otherwise >> 'page' may point to the first page beyond the compound page. >> >> The patch below should help. >> >> If no objections, Andrew, could you fold it into the problematic patch? >> >> diff --git a/mm/gup.c b/mm/gup.c >> index d8db6e5016a8..6f9ca86b3d03 100644 >> --- a/mm/gup.c >> +++ b/mm/gup.c >> @@ -1424,6 +1424,7 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, >> >> refs = 0; >> page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); >> + head = compound_head(page); >> do { >> pages[*nr] = page; >> (*nr)++; >> @@ -1431,7 +1432,6 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, >> refs++; >> } while (addr += PAGE_SIZE, addr != end); >> >> - head = compound_head(page); >> if (!page_cache_add_speculative(head, refs)) { >> *nr -= refs; >> return 0; >> @@ -1462,6 +1462,7 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, >> >> refs = 0; >> page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); >> + head = compound_head(page); >> do { >> pages[*nr] = page; >> (*nr)++; >> @@ -1469,7 +1470,6 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, >> refs++; >> } while (addr += PAGE_SIZE, addr != end); >> >> - head = compound_head(page); >> if (!page_cache_add_speculative(head, refs)) { >> *nr -= refs; >> return 0; >> @@ -1499,6 +1499,7 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr, >> BUILD_BUG_ON(pgd_devmap(orig)); >> refs = 0; >> page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT); >> + head = compound_head(page); >> do { >> pages[*nr] = page; >> (*nr)++; >> @@ -1506,7 +1507,6 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr, >> refs++; >> } while (addr += PAGE_SIZE, addr != end); >> >> - head = compound_head(page); >> if (!page_cache_add_speculative(head, refs)) { >> *nr -= refs; >> return 0;