Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755038AbYCQQ53 (ORCPT ); Mon, 17 Mar 2008 12:57:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752138AbYCQQ5W (ORCPT ); Mon, 17 Mar 2008 12:57:22 -0400 Received: from x346.tv-sign.ru ([89.108.83.215]:41841 "EHLO mail.screens.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751532AbYCQQ5V (ORCPT ); Mon, 17 Mar 2008 12:57:21 -0400 Date: Mon, 17 Mar 2008 20:01:24 +0300 From: Oleg Nesterov To: Atsushi Tsuji Cc: Andrew Morton , Roland McGrath , "Eric W. Biederman" , Davide Libenzi , Ingo Molnar , Jiri Kosina , Linus Torvalds , Pavel Emelyanov , linux-kernel@vger.kernel.org Subject: Re: [RFC,PATCH 2/2] kill_pid_info: don't take now unneeded tasklist_lock Message-ID: <20080317170124.GA115@tv-sign.ru> References: <20080304185745.GA8482@tv-sign.ru> <47DE5665.2030802@bk.jp.nec.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <47DE5665.2030802@bk.jp.nec.com> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1156 Lines: 34 On 03/17, Atsushi Tsuji wrote: > > (2008/03/05 3:57), Oleg Nesterov wrote: > >Previously handle_stop_signal(SIGCONT) could drop ->siglock. That is why > >kill_pid_info(SIGCONT) takes tasklist_lock to make sure the target task > >can't go away after unlock. Not needed now. > > > >Signed-off-by: Oleg Nesterov > > Hi Oleg, > > I tried your patches on vanila kernel 2.6.25-rc3 (ia64). Then, I got > the NULL pointer dereference at task_session_nr(t) in > check_kill_permission(). That is why t->signal->__session is accessed > after t->signal was released. It is reproducible by sending many > SIGCONT signals to exiting processes. Ah. Indeed!!! Thanks a lot Atsushi. Note that check_kill_permission() is the last user of the deprecated signal->__session/session, I was going to change this code later, but missed the issue you pointed out. I'll make the patch tomorrow. Thanks! Oleg. -- 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/