From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757831AbZEEKLo (ORCPT ); Tue, 5 May 2009 06:11:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754244AbZEEKLe (ORCPT ); Tue, 5 May 2009 06:11:34 -0400 Received: from cantor2.suse.de ([195.135.220.15]:43000 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753975AbZEEKLd (ORCPT ); Tue, 5 May 2009 06:11:33 -0400 Date: Tue, 5 May 2009 12:11:32 +0200 From: Nick Piggin To: David Rientjes Cc: Andrew Morton , Greg Kroah-Hartman , San Mehat , Arve =?iso-8859-1?B?SGr4bm5lduVn?= , linux-kernel@vger.kernel.org Subject: Re: [patch 5/7] oom: fix possible oom_dump_tasks NULL pointer Message-ID: <20090505101132.GA28917@wotan.suse.de> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 04, 2009 at 05:27:02PM -0700, David Rientjes wrote: > When /proc/sys/vm/oom_dump_tasks is enabled, it is possible to get a NULL > pointer for tasks that have detached mm's since task_lock() is not held > during the tasklist scan. > > Cc: Nick Piggin > Signed-off-by: David Rientjes I hope I'm not the oom killer maintainer ;) But anyway, Acked-by: Nick Piggin > --- > mm/oom_kill.c | 24 +++++++++++++++--------- > 1 files changed, 15 insertions(+), 9 deletions(-) > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -284,22 +284,28 @@ static void dump_tasks(const struct mem_cgroup *mem) > printk(KERN_INFO "[ pid ] uid tgid total_vm rss cpu oom_adj " > "name\n"); > do_each_thread(g, p) { > - /* > - * total_vm and rss sizes do not exist for tasks with a > - * detached mm so there's no need to report them. > - */ > - if (!p->mm) > - continue; > + struct mm_struct *mm; > + > if (mem && !task_in_mem_cgroup(p, mem)) > continue; > if (!thread_group_leader(p)) > continue; > > task_lock(p); > + mm = p->mm; > + if (!mm) { > + /* > + * total_vm and rss sizes do not exist for tasks with no > + * mm so there's no need to report them; they can't be > + * oom killed anyway. > + */ > + task_unlock(p); > + continue; > + } > printk(KERN_INFO "[%5d] %5d %5d %8lu %8lu %3d %3d %s\n", > - p->pid, __task_cred(p)->uid, p->tgid, > - p->mm->total_vm, get_mm_rss(p->mm), (int)task_cpu(p), > - p->oomkilladj, p->comm); > + p->pid, __task_cred(p)->uid, p->tgid, mm->total_vm, > + get_mm_rss(mm), (int)task_cpu(p), p->oomkilladj, > + p->comm); > task_unlock(p); > } while_each_thread(g, p); > }