From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755607AbZHMTsL (ORCPT ); Thu, 13 Aug 2009 15:48:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932192AbZHMTsH (ORCPT ); Thu, 13 Aug 2009 15:48:07 -0400 Received: from kroah.org ([198.145.64.141]:36808 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932175AbZHMTsD (ORCPT ); Thu, 13 Aug 2009 15:48:03 -0400 X-Mailbox-Line: From gregkh@mini.kroah.org Thu Aug 13 12:43:39 2009 Message-Id: <20090813194339.506180651@mini.kroah.org> User-Agent: quilt/0.48-1 Date: Thu, 13 Aug 2009 12:40:46 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Oleg Nesterov , Serge Hallyn , James Morris Subject: [patch 25/28] mm_for_maps: shift down_read(mmap_sem) to the caller References: <20090813194021.446758568@mini.kroah.org> Content-Disposition: inline; filename=mm_for_maps-shift-down_read-to-the-caller.patch In-Reply-To: <20090813194554.GA13947@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.27-stable review patch. If anyone has any objections, please let us know. ------------------ From: Oleg Nesterov commit 00f89d218523b9bf6b522349c039d5ac80aa536d upstream. mm_for_maps() takes ->mmap_sem after security checks, this looks strange and obfuscates the locking rules. Move this lock to its single caller, m_start(). Signed-off-by: Oleg Nesterov Acked-by: Serge Hallyn Signed-off-by: James Morris Signed-off-by: Greg Kroah-Hartman --- fs/proc/base.c | 8 +++----- fs/proc/task_mmu.c | 1 + fs/proc/task_nommu.c | 1 + 3 files changed, 5 insertions(+), 5 deletions(-) --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -240,9 +240,8 @@ static int check_mem_permission(struct t struct mm_struct *mm_for_maps(struct task_struct *task) { struct mm_struct *mm = get_task_mm(task); - if (!mm) - return NULL; - if (mm != current->mm) { + + if (mm && mm != current->mm) { /* * task->mm can be changed before security check, * in that case we must notice the change after. @@ -250,10 +249,9 @@ struct mm_struct *mm_for_maps(struct tas if (!ptrace_may_access(task, PTRACE_MODE_READ) || mm != task->mm) { mmput(mm); - return NULL; + mm = NULL; } } - down_read(&mm->mmap_sem); return mm; } --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -119,6 +119,7 @@ static void *m_start(struct seq_file *m, mm = mm_for_maps(priv->task); if (!mm) return NULL; + down_read(&mm->mmap_sem); tail_vma = get_gate_vma(priv->task); priv->tail_vma = tail_vma; --- a/fs/proc/task_nommu.c +++ b/fs/proc/task_nommu.c @@ -137,6 +137,7 @@ static void *m_start(struct seq_file *m, priv->task = NULL; return NULL; } + down_read(&mm->mmap_sem); /* start from the Nth VMA */ for (vml = mm->context.vmlist; vml; vml = vml->next)