From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760965AbYEGX5K (ORCPT ); Wed, 7 May 2008 19:57:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753976AbYEGX44 (ORCPT ); Wed, 7 May 2008 19:56:56 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:55857 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753048AbYEGX4y (ORCPT ); Wed, 7 May 2008 19:56:54 -0400 Date: Thu, 08 May 2008 08:55:45 +0900 From: KOSAKI Motohiro To: "Paul Menage" , balbir@linux.vnet.ibm.com, "Andrew Morton" Subject: [PATCH] on CONFIG_MM_OWNER=y, kernel panic is possible. take2 Cc: kosaki.motohiro@jp.fujitsu.com, "Lee Schermerhorn" , "KAMEZAWA Hiroyuki" , LKML , linux-mm In-Reply-To: <6599ad830805062037n221ef8e2n9ee7ac33417ab499@mail.gmail.com> References: <20080506153943.AC69.KOSAKI.MOTOHIRO@jp.fujitsu.com> <6599ad830805062037n221ef8e2n9ee7ac33417ab499@mail.gmail.com> Message-Id: <20080508083808.4A78.KOSAKI.MOTOHIRO@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Becky! ver. 2.42 [ja] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > 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