From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934786Ab1KJFI6 (ORCPT ); Thu, 10 Nov 2011 00:08:58 -0500 Received: from cantor2.suse.de ([195.135.220.15]:42346 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934774Ab1KJD1C (ORCPT ); Wed, 9 Nov 2011 22:27:02 -0500 X-Mailbox-Line: From gregkh@clark.kroah.org Wed Nov 9 13:27:14 2011 Message-Id: <20111109212713.986369827@clark.kroah.org> User-Agent: quilt/0.48-16.4 Date: Wed, 09 Nov 2011 13:27:35 -0800 From: Greg KH To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Tejun Heo , Luke Macken , stable@kernel.org, Oleg Nesterov Subject: [133/262] ptrace: dont clear GROUP_STOP_SIGMASK on double-stop In-Reply-To: <20111109212847.GA20838@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: Oleg Nesterov [This does not correspond to any specific patch in the upstream tree as it was fixed accidentally by rewriting the code in the 3.1 release] https://bugzilla.redhat.com/show_bug.cgi?id=740121 1. Luke Macken triggered WARN_ON(!(group_stop & GROUP_STOP_SIGMASK)) in do_signal_stop(). This is because do_signal_stop() clears GROUP_STOP_SIGMASK part unconditionally but doesn't update it if task_is_stopped(). 2. Looking at this problem I noticed that WARN_ON_ONCE(!ptrace) is not right, a stopped-but-resumed tracee can clone the untraced thread in the SIGNAL_STOP_STOPPED group, the new thread can start another group-stop. Remove this warning, we need more fixes to make it true. Reported-by: Luke Macken Signed-off-by: Oleg Nesterov Signed-off-by: Greg Kroah-Hartman --- kernel/signal.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1894,21 +1894,19 @@ static int do_signal_stop(int signr) */ if (!(sig->flags & SIGNAL_STOP_STOPPED)) sig->group_exit_code = signr; - else - WARN_ON_ONCE(!task_ptrace(current)); current->group_stop &= ~GROUP_STOP_SIGMASK; current->group_stop |= signr | gstop; sig->group_stop_count = 1; for (t = next_thread(current); t != current; t = next_thread(t)) { - t->group_stop &= ~GROUP_STOP_SIGMASK; /* * Setting state to TASK_STOPPED for a group * stop is always done with the siglock held, * so this check has no races. */ if (!(t->flags & PF_EXITING) && !task_is_stopped(t)) { + t->group_stop &= ~GROUP_STOP_SIGMASK; t->group_stop |= signr | gstop; sig->group_stop_count++; signal_wake_up(t, 0);