From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755653AbZHMTtN (ORCPT ); Thu, 13 Aug 2009 15:49:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755731AbZHMTtL (ORCPT ); Thu, 13 Aug 2009 15:49:11 -0400 Received: from kroah.org ([198.145.64.141]:36801 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932177AbZHMTsC (ORCPT ); Thu, 13 Aug 2009 15:48:02 -0400 X-Mailbox-Line: From gregkh@mini.kroah.org Thu Aug 13 12:43:39 2009 Message-Id: <20090813194339.335447424@mini.kroah.org> User-Agent: quilt/0.48-1 Date: Thu, 13 Aug 2009 12:40:45 -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 , James Morris Subject: [patch 24/28] mm_for_maps: simplify, use ptrace_may_access() References: <20090813194021.446758568@mini.kroah.org> Content-Disposition: inline; filename=mm_for_maps-simplify-use-ptrace_may_access.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 13f0feafa6b8aead57a2a328e2fca6a5828bf286 upstream. It would be nice to kill __ptrace_may_access(). It requires task_lock(), but this lock is only needed to read mm->flags in the middle. Convert mm_for_maps() to use ptrace_may_access(), this also simplifies the code a little bit. Also, we do not need to take ->mmap_sem in advance. In fact I think mm_for_maps() should not play with ->mmap_sem at all, the caller should take this lock. With or without this patch, without ->cred_guard_mutex held we can race with exec() and get the new ->mm but check old creds. Signed-off-by: Oleg Nesterov Reviewed-by: Serge Hallyn Signed-off-by: James Morris Signed-off-by: Greg Kroah-Hartman --- fs/proc/base.c | 23 +++++++++++------------ 1 file changed, 11 insertions(+), 12 deletions(-) --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -242,20 +242,19 @@ struct mm_struct *mm_for_maps(struct tas struct mm_struct *mm = get_task_mm(task); if (!mm) return NULL; + if (mm != current->mm) { + /* + * task->mm can be changed before security check, + * in that case we must notice the change after. + */ + if (!ptrace_may_access(task, PTRACE_MODE_READ) || + mm != task->mm) { + mmput(mm); + return NULL; + } + } down_read(&mm->mmap_sem); - task_lock(task); - if (task->mm != mm) - goto out; - if (task->mm != current->mm && - __ptrace_may_access(task, PTRACE_MODE_READ) < 0) - goto out; - task_unlock(task); return mm; -out: - task_unlock(task); - up_read(&mm->mmap_sem); - mmput(mm); - return NULL; } static int proc_pid_cmdline(struct task_struct *task, char * buffer)