From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751441AbdBXJNO (ORCPT ); Fri, 24 Feb 2017 04:13:14 -0500 Received: from mx2.suse.de ([195.135.220.15]:41353 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750964AbdBXJNL (ORCPT ); Fri, 24 Feb 2017 04:13:11 -0500 Date: Fri, 24 Feb 2017 10:13:07 +0100 From: Michal Hocko To: Minchan Kim Cc: Andrew Morton , linux-kernel@vger.kernel.org, kernel-team@lge.com, Matthew Wilcox , stable@vger.kernel.org Subject: Re: [PATCH] mm: do not access page->mapping directly on page_endio Message-ID: <20170224091307.GC19161@dhcp22.suse.cz> References: <1487741964-17913-1-git-send-email-minchan@kernel.org> <20170222121100.GA7954@dhcp22.suse.cz> <20170222143517.GA18974@bbox> <20170222145316.GL5753@dhcp22.suse.cz> <20170223232609.GA5631@bbox> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170223232609.GA5631@bbox> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 24-02-17 08:26:09, Minchan Kim wrote: [...] > >From 9efb87a873db67a9e6ebf44fdabf7d05fe4b4e21 Mon Sep 17 00:00:00 2001 > From: Minchan Kim > Date: Fri, 4 Nov 2016 09:12:39 +0900 > Subject: [PATCH v2] mm: do not access page->mapping directly on page_endio > > With rw_page, page_endio is used for completing IO on a page > and it propagates write error to the address space if the IO > fails. The problem is it accesses page->mapping directly which > might be okay for file-backed pages but it shouldn't for > anonymous page. Otherwise, it can corrupt one of field from > anon_vma under us and system goes panic randomly. > > swap_writepage > bdev_writepage > ops->rw_page > > I encountered the BUG during developing new zram feature and > it was really hard to figure it out because it made random > crash, somtime mmap_sem lockdep, sometime other places where > places never related to zram/zsmalloc, and not reproducible > with some configuration. > > When I consider how that bug is subtle and people do fast-swap > test with brd, it's worth to add stable mark, I think. > > Fixes: dd6bd0d9c7db ("swap: use bdev_read_page() / bdev_write_page()") > Cc: Michal Hocko > Cc: Matthew Wilcox > Cc: > Signed-off-by: Minchan Kim Acked-by: Michal Hocko Thanks for the chagelog update > --- > * from v1 > * add more detailed description with Fix tag - Michal > > mm/filemap.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/mm/filemap.c b/mm/filemap.c > index 2ba46f410c7c..1944c631e3e6 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -1008,9 +1008,12 @@ void page_endio(struct page *page, bool is_write, int err) > unlock_page(page); > } else { > if (err) { > + struct address_space *mapping; > + > SetPageError(page); > - if (page->mapping) > - mapping_set_error(page->mapping, err); > + mapping = page_mapping(page); > + if (mapping) > + mapping_set_error(mapping, err); > } > end_page_writeback(page); > } > -- > 2.7.4 -- Michal Hocko SUSE Labs