From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759282AbZEEXvp (ORCPT ); Tue, 5 May 2009 19:51:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754075AbZEEXvb (ORCPT ); Tue, 5 May 2009 19:51:31 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:55269 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759061AbZEEXva (ORCPT ); Tue, 5 May 2009 19:51:30 -0400 Date: Tue, 5 May 2009 16:47:33 -0700 From: Andrew Morton To: Oleg Nesterov Cc: chrisw@sous-sol.org, roland@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] ptrace: ptrace_attach: check PF_KTHREAD + exit_state instead of ->mm Message-Id: <20090505164733.54cd4ca4.akpm@linux-foundation.org> In-Reply-To: <20090505224722.GA954@redhat.com> References: <20090505224722.GA954@redhat.com> X-Mailer: Sylpheed version 2.2.4 (GTK+ 2.8.20; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 6 May 2009 00:47:22 +0200 Oleg Nesterov wrote: > - Add PF_KTHREAD check to prevent attaching to the kernel thread > with a borrowed ->mm. > > With or without this change we can race with daemonize() which > can set PF_KTHREAD or clear ->mm after ptrace_attach() does the > check, but this doesn't matter because reparent_to_kthreadd() > does ptrace_unlink(). > > - Kill "!task->mm" check. We don't really care about ->mm != NULL, > and the task can call exit_mm() right after we drop task_lock(). > What we need is to make sure we can't attach after exit_notify(), > check task->exit_state != 0 instead. > These patches make a mess of utrace-core.patch. Do we really want to do that?