From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754664Ab2JDSO5 (ORCPT ); Thu, 4 Oct 2012 14:14:57 -0400 Received: from zene.cmpxchg.org ([85.214.230.12]:58774 "EHLO zene.cmpxchg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752722Ab2JDSJa (ORCPT ); Thu, 4 Oct 2012 14:09:30 -0400 From: Johannes Weiner To: Andrew Morton Cc: Michal Hocko , Konstantin Khlebnikov , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [patch 1/2] mm: memcontrol: handle potential crash when rmap races with task exit Date: Thu, 4 Oct 2012 14:09:16 -0400 Message-Id: <1349374157-20604-2-git-send-email-hannes@cmpxchg.org> X-Mailer: git-send-email 1.7.11.4 In-Reply-To: <1349374157-20604-1-git-send-email-hannes@cmpxchg.org> References: <1349374157-20604-1-git-send-email-hannes@cmpxchg.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org page_referenced() counts only references of mm's that are associated with the memcg hierarchy that is being reclaimed. However, if it races with the owner of the mm exiting, mm->owner may be NULL. Don't crash, just ignore the reference. Signed-off-by: Johannes Weiner Cc: stable@kernel.org [3.5] --- include/linux/memcontrol.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 8d9489f..8686294 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -91,7 +91,7 @@ int mm_match_cgroup(const struct mm_struct *mm, const struct mem_cgroup *cgroup) rcu_read_lock(); memcg = mem_cgroup_from_task(rcu_dereference((mm)->owner)); - match = __mem_cgroup_same_or_subtree(cgroup, memcg); + match = memcg && __mem_cgroup_same_or_subtree(cgroup, memcg); rcu_read_unlock(); return match; } -- 1.7.11.4