Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030573AbWJ3Swg (ORCPT ); Mon, 30 Oct 2006 13:52:36 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030575AbWJ3Swg (ORCPT ); Mon, 30 Oct 2006 13:52:36 -0500 Received: from omx2-ext.sgi.com ([192.48.171.19]:15750 "EHLO omx2.sgi.com") by vger.kernel.org with ESMTP id S1030573AbWJ3Swf (ORCPT ); Mon, 30 Oct 2006 13:52:35 -0500 Message-ID: <454649CE.80804@engr.sgi.com> Date: Mon, 30 Oct 2006 10:51:58 -0800 From: Jay Lan User-Agent: Thunderbird 1.5.0.5 (X11/20060725) MIME-Version: 1.0 To: Oleg Nesterov CC: Andrew Morton , Shailabh Nagar , Balbir Singh , Jay Lan , linux-kernel@vger.kernel.org Subject: Re: [PATCH] xacct_add_tsk: fix pure theoretical ->mm use-after-free References: <20061029185826.GA1619@oleg> In-Reply-To: <20061029185826.GA1619@oleg> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1692 Lines: 55 Oleg Nesterov wrote: > Paranoid fix. The task can free its ->mm after the 'if (p->mm)' check. Why this change is necessary? This routine is indirectly invoked by taskstats_exit_send() routine called inside do_exit(): do_exit() { ... taskstats_exit_send(tsk, tidstats, group_dead, mycpu); taskstats_exit_free(tidstats); delayacct_tsk_exit(tsk); exit_mm(tsk); ... } The mm is freed in exit_mm(), right? - jay > > Signed-off-by: Oleg Nesterov > > --- STATS/kernel/tsacct.c~3_mm 2006-10-27 01:03:26.000000000 +0400 > +++ STATS/kernel/tsacct.c 2006-10-29 21:46:12.000000000 +0300 > @@ -80,13 +80,17 @@ void bacct_add_tsk(struct taskstats *sta > */ > void xacct_add_tsk(struct taskstats *stats, struct task_struct *p) > { > + struct mm_struct *mm; > + > /* convert pages-jiffies to Mbyte-usec */ > stats->coremem = jiffies_to_usecs(p->acct_rss_mem1) * PAGE_SIZE / MB; > stats->virtmem = jiffies_to_usecs(p->acct_vm_mem1) * PAGE_SIZE / MB; > - if (p->mm) { > + mm = get_task_mm(p); > + if (mm) { > /* adjust to KB unit */ > - stats->hiwater_rss = p->mm->hiwater_rss * PAGE_SIZE / KB; > - stats->hiwater_vm = p->mm->hiwater_vm * PAGE_SIZE / KB; > + stats->hiwater_rss = mm->hiwater_rss * PAGE_SIZE / KB; > + stats->hiwater_vm = mm->hiwater_vm * PAGE_SIZE / KB; > + mmput(mm); > } > stats->read_char = p->rchar; > stats->write_char = p->wchar; > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/