From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932229Ab2HQPXA (ORCPT ); Fri, 17 Aug 2012 11:23:00 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:44978 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754886Ab2HQPWv (ORCPT ); Fri, 17 Aug 2012 11:22:51 -0400 Date: Fri, 17 Aug 2012 12:22:39 -0300 From: Herton Ronaldo Krzesinski To: Paul Gortmaker Cc: stable@vger.kernel.org, linux-kernel@vger.kernel.org, Mitsuo Hayasaka , Andrew Morton , David Rientjes , Namhyung Kim , "Paul E. McKenney" , Jeremy Fitzhardinge , Linus Torvalds , Mel Gorman , Luciano Chavez , Rik van Riel Subject: Re: [v2.6.34-stable 134/165] mm: avoid null pointer access in vm_struct via /proc/vmallocinfo Message-ID: <20120817152233.GB4039@herton-Z68MA-D2H-B3> References: <1345060109-9187-1-git-send-email-paul.gortmaker@windriver.com> <1345060109-9187-135-git-send-email-paul.gortmaker@windriver.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1345060109-9187-135-git-send-email-paul.gortmaker@windriver.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 15, 2012 at 03:47:58PM -0400, Paul Gortmaker wrote: > From: Mitsuo Hayasaka > > ------------------- > This is a commit scheduled for the next v2.6.34 longterm release. > http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git > If you see a problem with using this for longterm, please comment. > ------------------- > > commit f5252e009d5b87071a919221e4f6624184005368 upstream. > > The /proc/vmallocinfo shows information about vmalloc allocations in > vmlist that is a linklist of vm_struct. It, however, may access pages > field of vm_struct where a page was not allocated. This results in a null > pointer access and leads to a kernel panic. > > Why this happens: In __vmalloc_node_range() called from vmalloc(), newly > allocated vm_struct is added to vmlist at __get_vm_area_node() and then, > some fields of vm_struct such as nr_pages and pages are set at > __vmalloc_area_node(). In other words, it is added to vmlist before it is > fully initialized. At the same time, when the /proc/vmallocinfo is read, > it accesses the pages field of vm_struct according to the nr_pages field > at show_numa_info(). Thus, a null pointer access happens. > > The patch adds the newly allocated vm_struct to the vmlist *after* it is > fully initialized. So, it can avoid accessing the pages field with > unallocated page when show_numa_info() is called. > > Signed-off-by: Mitsuo Hayasaka > Cc: Andrew Morton > Cc: David Rientjes > Cc: Namhyung Kim > Cc: "Paul E. McKenney" > Cc: Jeremy Fitzhardinge > Signed-off-by: Andrew Morton > Signed-off-by: Linus Torvalds > [PG: .34 has VMALLOC_START/END vs. start/end in f5252e009d5] > Signed-off-by: Paul Gortmaker [...] commit 1368edf0647ac112d8cfa6ce47257dc950c50f5c ("mm: vmalloc: check for page allocation failure before vmlist insertion") addresses a regression on this change, something to consider for inclusion in this stable update as well. -- []'s Herton