From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755305AbYEHNx7 (ORCPT ); Thu, 8 May 2008 09:53:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751969AbYEHNxs (ORCPT ); Thu, 8 May 2008 09:53:48 -0400 Received: from E23SMTP04.au.ibm.com ([202.81.18.173]:34931 "EHLO e23smtp04.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750937AbYEHNxr (ORCPT ); Thu, 8 May 2008 09:53:47 -0400 Message-ID: <482305E5.6070107@linux.vnet.ibm.com> Date: Thu, 08 May 2008 19:23:41 +0530 From: Balbir Singh Reply-To: balbir@linux.vnet.ibm.com Organization: IBM User-Agent: Thunderbird 2.0.0.14 (X11/20080505) MIME-Version: 1.0 To: KOSAKI Motohiro CC: Paul Menage , Andrew Morton , Lee Schermerhorn , KAMEZAWA Hiroyuki , LKML , linux-mm Subject: Re: [PATCH] on CONFIG_MM_OWNER=y, kernel panic is possible. take2 References: <20080506153943.AC69.KOSAKI.MOTOHIRO@jp.fujitsu.com> <6599ad830805062037n221ef8e2n9ee7ac33417ab499@mail.gmail.com> <20080508083808.4A78.KOSAKI.MOTOHIRO@jp.fujitsu.com> In-Reply-To: <20080508083808.4A78.KOSAKI.MOTOHIRO@jp.fujitsu.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org KOSAKI Motohiro wrote: >> I'd word it as >> >> /* >> * "owner" points to a task that is regarded as the canonical >> * user/owner of this mm. All of the following must be true in >> * order for it to be changed: >> * >> * current == mm->owner >> * current->mm != mm >> * new_owner->mm == mm >> * new_owner->alloc_lock is held >> */ > > Wow, Thank you a lot! > new version attached. > > Cheers! > > > ----------------------------------------------------------- > When mm destruct happend, We should pass mm_update_next_owner() > old mm. > but unfortunately new mm is passed in exec_mmap(). > > thus, kernel panic is possible when multi thread process use exec(). > > > and, owner member comment description is wrong. > mm->owner don't not necessarily point to thread group leader. > > > Signed-off-by: KOSAKI Motohiro > CC: Balbir Singh > CC: "Paul Menage" > CC: "KAMEZAWA Hiroyuki" > > --- > fs/exec.c | 2 +- > include/linux/mm_types.h | 13 +++++++++++-- > 2 files changed, 12 insertions(+), 3 deletions(-) > > Index: b/fs/exec.c > =================================================================== > --- a/fs/exec.c 2008-05-04 22:57:09.000000000 +0900 > +++ b/fs/exec.c 2008-05-06 15:40:35.000000000 +0900 > @@ -735,7 +735,7 @@ static int exec_mmap(struct mm_struct *m > tsk->active_mm = mm; > activate_mm(active_mm, mm); > task_unlock(tsk); > - mm_update_next_owner(mm); > + mm_update_next_owner(old_mm); > arch_pick_mmap_layout(mm); > if (old_mm) { > up_read(&old_mm->mmap_sem); > Index: b/include/linux/mm_types.h > =================================================================== > --- a/include/linux/mm_types.h 2008-05-08 09:20:13.000000000 +0900 > +++ b/include/linux/mm_types.h 2008-05-08 09:22:13.000000000 +0900 > @@ -231,8 +231,17 @@ struct mm_struct { > rwlock_t ioctx_list_lock; /* aio lock */ > struct kioctx *ioctx_list; > #ifdef CONFIG_MM_OWNER > - struct task_struct *owner; /* The thread group leader that */ > - /* owns the mm_struct. */ > + /* > + * "owner" points to a task that is regarded as the canonical > + * user/owner of this mm. All of the following must be true in > + * order for it to be changed: > + * > + * current == mm->owner > + * current->mm != mm > + * new_owner->mm == mm > + * new_owner->alloc_lock is held > + */ > + struct task_struct *owner; > #endif > > #ifdef CONFIG_PROC_FS > Looks good to me, but I've not tested it Acked-by: Balbir Singh -- Warm Regards, Balbir Singh Linux Technology Center IBM, ISTL