Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933219AbdCJJPC (ORCPT ); Fri, 10 Mar 2017 04:15:02 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:36414 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932502AbdCJJO7 (ORCPT ); Fri, 10 Mar 2017 04:14:59 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Minchan Kim , Michal Hocko , Matthew Wilcox , Andrew Morton , Linus Torvalds Subject: [PATCH 4.4 30/91] mm: do not access page->mapping directly on page_endio Date: Fri, 10 Mar 2017 10:08:29 +0100 Message-Id: <20170310083902.292392116@linuxfoundation.org> X-Mailer: git-send-email 2.12.0 In-Reply-To: <20170310083900.730556986@linuxfoundation.org> References: <20170310083900.730556986@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1875 Lines: 57 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Minchan Kim commit dd8416c47715cf324c9a16f13273f9fda87acfed upstream. 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()") Signed-off-by: Minchan Kim Acked-by: Michal Hocko Cc: Matthew Wilcox Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/filemap.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) --- a/mm/filemap.c +++ b/mm/filemap.c @@ -865,9 +865,12 @@ void page_endio(struct page *page, int r unlock_page(page); } else { /* rw == WRITE */ 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); }