Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752165AbZGJDGm (ORCPT ); Thu, 9 Jul 2009 23:06:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750782AbZGJDGf (ORCPT ); Thu, 9 Jul 2009 23:06:35 -0400 Received: from e39.co.us.ibm.com ([32.97.110.160]:52653 "EHLO e39.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750735AbZGJDGe (ORCPT ); Thu, 9 Jul 2009 23:06:34 -0400 Date: Thu, 9 Jul 2009 22:06:33 -0500 From: "Serge E. Hallyn" To: Oleg Nesterov Cc: James Morris , Christoph Hellwig , David Howells , Roland McGrath , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] mm_for_maps: shift down_read(mmap_sem) to the caller Message-ID: <20090710030633.GA11280@us.ibm.com> References: <20090710012738.GA392@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090710012738.GA392@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2284 Lines: 69 Quoting Oleg Nesterov (oleg@redhat.com): > 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 Looks sane. Acked-by: Serge Hallyn > --- > > fs/proc/task_mmu.c | 1 + > fs/proc/task_nommu.c | 1 + > fs/proc/base.c | 8 +++----- > 3 files changed, 5 insertions(+), 5 deletions(-) > > --- WAIT/fs/proc/task_mmu.c~1_MOVE_MMAP_SEM 2009-05-03 17:15:27.000000000 +0200 > +++ WAIT/fs/proc/task_mmu.c 2009-07-10 02:00:56.000000000 +0200 > @@ -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; > --- WAIT/fs/proc/task_nommu.c~1_MOVE_MMAP_SEM 2009-04-09 00:39:09.000000000 +0200 > +++ WAIT/fs/proc/task_nommu.c 2009-07-10 02:01:25.000000000 +0200 > @@ -189,6 +189,7 @@ static void *m_start(struct seq_file *m, > priv->task = NULL; > return NULL; > } > + down_read(&mm->mmap_sem); > > /* start from the Nth VMA */ > for (p = rb_first(&mm->mm_rb); p; p = rb_next(p)) > --- WAIT/fs/proc/base.c~1_MOVE_MMAP_SEM 2009-07-09 17:56:27.000000000 +0200 > +++ WAIT/fs/proc/base.c 2009-07-10 02:05:14.000000000 +0200 > @@ -235,9 +235,8 @@ 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. > @@ -245,10 +244,9 @@ 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; > } > -- 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/