From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758537Ab3KMR0T (ORCPT ); Wed, 13 Nov 2013 12:26:19 -0500 Received: from terminus.zytor.com ([198.137.202.10]:52912 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756795Ab3KMR0D (ORCPT ); Wed, 13 Nov 2013 12:26:03 -0500 Date: Wed, 13 Nov 2013 09:25:22 -0800 From: tip-bot for Rik van Riel Message-ID: Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org, peterz@infradead.org, riel@redhat.com, mgorman@suse.de, tglx@linutronix.de, prarit@redhat.com Reply-To: mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, peterz@infradead.org, riel@redhat.com, mgorman@suse.de, tglx@linutronix.de, prarit@redhat.com To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/urgent] sched/numa: Fix NULL pointer dereference in task_numa_migrate() Git-Commit-ID: 46a73e8a1c1720f7713b5e2df68e9dd272015b5d X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.1 (terminus.zytor.com [127.0.0.1]); Wed, 13 Nov 2013 09:25:29 -0800 (PST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 46a73e8a1c1720f7713b5e2df68e9dd272015b5d Gitweb: http://git.kernel.org/tip/46a73e8a1c1720f7713b5e2df68e9dd272015b5d Author: Rik van Riel AuthorDate: Mon, 11 Nov 2013 19:29:25 -0500 Committer: Ingo Molnar CommitDate: Wed, 13 Nov 2013 13:33:51 +0100 sched/numa: Fix NULL pointer dereference in task_numa_migrate() The cpusets code can split up the scheduler's domain tree into smaller domains. Some of those smaller domains may not cross NUMA nodes at all, leading to a NULL pointer dereference on the per-cpu sd_numa pointer. Tasks cannot be migrated out of their domain, so the patch also sets p->numa_preferred_nid to whereever they are, to prevent the migration from being retried over and over again. Reported-by: Prarit Bhargava Signed-off-by: Rik van Riel Signed-off-by: Peter Zijlstra Cc: Mel Gorman Link: http://lkml.kernel.org/n/tip-oosqomw0Jput0Jkvoowhrqtu@git.kernel.org Signed-off-by: Ingo Molnar --- kernel/sched/fair.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index df77c60..c11e36f 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1201,9 +1201,21 @@ static int task_numa_migrate(struct task_struct *p) */ rcu_read_lock(); sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu)); - env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2; + if (sd) + env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2; rcu_read_unlock(); + /* + * Cpusets can break the scheduler domain tree into smaller + * balance domains, some of which do not cross NUMA boundaries. + * Tasks that are "trapped" in such domains cannot be migrated + * elsewhere, so there is no point in (re)trying. + */ + if (unlikely(!sd)) { + p->numa_preferred_nid = cpu_to_node(task_cpu(p)); + return -EINVAL; + } + taskweight = task_weight(p, env.src_nid); groupweight = group_weight(p, env.src_nid); update_numa_stats(&env.src_stats, env.src_nid);