From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756856Ab3EXQIE (ORCPT ); Fri, 24 May 2013 12:08:04 -0400 Received: from e06smtp10.uk.ibm.com ([195.75.94.106]:48353 "EHLO e06smtp10.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754791Ab3EXQIC (ORCPT ); Fri, 24 May 2013 12:08:02 -0400 From: Gerald Schaefer To: Ingo Molnar , Peter Zijlstra , Li Zefan Cc: linux-kernel@vger.kernel.org, Martin Schwidefsky , Heiko Carstens , Gerald Schaefer Subject: [PATCH 1/1] sched/autogroup: Fix race with task_groups list Date: Fri, 24 May 2013 18:07:49 +0200 Message-Id: <1369411669-46971-2-git-send-email-gerald.schaefer@de.ibm.com> X-Mailer: git-send-email 1.8.1.6 In-Reply-To: <1369411669-46971-1-git-send-email-gerald.schaefer@de.ibm.com> References: <1369411669-46971-1-git-send-email-gerald.schaefer@de.ibm.com> X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13052416-4966-0000-0000-000005D6BBB5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In autogroup_create(), a tg is allocated and added to the task_groups list. If CONFIG_RT_GROUP_SCHED is set, this tg is then modified while on the list, without locking. This can race with someone walking the list, like __enable_runtime() during CPU unplug, and result in a use-after-free bug. To fix this, move sched_online_group(), which adds the tg to the list, to the end of the autogroup_create() function after the modification. Signed-off-by: Gerald Schaefer --- kernel/sched/auto_group.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/kernel/sched/auto_group.c b/kernel/sched/auto_group.c index 64de5f8..4a07353 100644 --- a/kernel/sched/auto_group.c +++ b/kernel/sched/auto_group.c @@ -77,8 +77,6 @@ static inline struct autogroup *autogroup_create(void) if (IS_ERR(tg)) goto out_free; - sched_online_group(tg, &root_task_group); - kref_init(&ag->kref); init_rwsem(&ag->lock); ag->id = atomic_inc_return(&autogroup_seq_nr); @@ -98,6 +96,7 @@ static inline struct autogroup *autogroup_create(void) #endif tg->autogroup = ag; + sched_online_group(tg, &root_task_group); return ag; out_free: -- 1.8.1.6