From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933195Ab3E1Dzd (ORCPT ); Mon, 27 May 2013 23:55:33 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:52600 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758865Ab3E1DyP (ORCPT ); Mon, 27 May 2013 23:54:15 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Mike Galbraith" , "Thomas Gleixner" , "Prarit Bhargava" Date: Tue, 28 May 2013 04:49:53 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [26/94] tick: Cleanup NOHZ per cpu data on cpu down In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.101 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.46-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Thomas Gleixner commit 4b0c0f294f60abcdd20994a8341a95c8ac5eeb96 upstream. Prarit reported a crash on CPU offline/online. The reason is that on CPU down the NOHZ related per cpu data of the dead cpu is not cleaned up. If at cpu online an interrupt happens before the per cpu tick device is registered the irq_enter() check potentially sees stale data and dereferences a NULL pointer. Cleanup the data after the cpu is dead. Reported-by: Prarit Bhargava Cc: Mike Galbraith Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1305031451561.2886@ionos Signed-off-by: Thomas Gleixner Signed-off-by: Ben Hutchings --- kernel/time/tick-sched.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -833,7 +833,7 @@ void tick_cancel_sched_timer(int cpu) hrtimer_cancel(&ts->sched_timer); # endif - ts->nohz_mode = NOHZ_MODE_INACTIVE; + memset(ts, 0, sizeof(*ts)); } #endif