From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752431Ab2LTBm0 (ORCPT ); Wed, 19 Dec 2012 20:42:26 -0500 Received: from mail-da0-f43.google.com ([209.85.210.43]:48353 "EHLO mail-da0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752152Ab2LTBmU (ORCPT ); Wed, 19 Dec 2012 20:42:20 -0500 Date: Wed, 19 Dec 2012 17:42:16 -0800 (PST) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Mel Gorman cc: Linus Torvalds , Andrew Morton , Ingo Molnar , Sasha Levin , Petr Holasek , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH] sched: numa: ksm: fix oops in task_numa_placment() Message-ID: User-Agent: Alpine 2.00 (LNX 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org task_numa_placement() oopsed on NULL p->mm when task_numa_fault() got called in the handling of break_ksm() for ksmd. That might be a peculiar case, which perhaps KSM could takes steps to avoid? but it's more robust if task_numa_placement() allows for such a possibility. Signed-off-by: Hugh Dickins --- kernel/sched/fair.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- 3.7+git/kernel/sched/fair.c 2012-12-16 16:35:08.724441527 -0800 +++ linux/kernel/sched/fair.c 2012-12-18 21:37:24.727964195 -0800 @@ -793,8 +793,11 @@ unsigned int sysctl_numa_balancing_scan_ static void task_numa_placement(struct task_struct *p) { - int seq = ACCESS_ONCE(p->mm->numa_scan_seq); + int seq; + if (!p->mm) /* for example, ksmd faulting in a user's mm */ + return; + seq = ACCESS_ONCE(p->mm->numa_scan_seq); if (p->numa_scan_seq == seq) return; p->numa_scan_seq = seq;