From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752891Ab2ALIVN (ORCPT ); Thu, 12 Jan 2012 03:21:13 -0500 Received: from cantor2.suse.de ([195.135.220.15]:45265 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752850Ab2ALIVK (ORCPT ); Thu, 12 Jan 2012 03:21:10 -0500 Date: Thu, 12 Jan 2012 09:21:05 +0100 From: Michal Hocko To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Mel Gorman , KAMEZAWA Hiroyuki , Andrea Arcangeli , David Rientjes Subject: Re: [PATCH] mm: Fix NULL ptr dereference in __count_immobile_pages Message-ID: <20120112082105.GA1042@tiehlicka.suse.cz> References: <1326213022-11761-1-git-send-email-mhocko@suse.cz> <20120111143439.538bf274.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120111143439.538bf274.akpm@linux-foundation.org> 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 11-01-12 14:34:39, Andrew Morton wrote: > On Tue, 10 Jan 2012 17:30:22 +0100 > Michal Hocko wrote: > > > This patch fixes the following NULL ptr dereference caused by > > cat /sys/devices/system/memory/memory0/removable: > > Which is world-readable, I assume? Right. But considering that we haven't seen any report like that it seems that the HW is rather rare > > > ... > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -5608,6 +5608,17 @@ __count_immobile_pages(struct zone *zone, struct page *page, int count) > > bool is_pageblock_removable_nolock(struct page *page) > > { > > struct zone *zone = page_zone(page); > > + unsigned long pfn = page_to_pfn(page); > > + > > + /* > > + * We have to be careful here because we are iterating over memory > > + * sections which are not zone aware so we might end up outside of > > + * the zone but still within the section. > > + */ > > + if (!zone || zone->zone_start_pfn > pfn || > > + zone->zone_start_pfn + zone->spanned_pages <= pfn) > > + return false; > > + > > return __count_immobile_pages(zone, page, 0); > > } > > So I propose that we backport it into -stable? Agreed. -- Michal Hocko SUSE Labs SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic