Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755067Ab3CAUOg (ORCPT ); Fri, 1 Mar 2013 15:14:36 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:51539 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752938Ab3CATpm (ORCPT ); Fri, 1 Mar 2013 14:45:42 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Li Zefan , Tejun Heo Subject: [ 63/77] cgroup: fix exit() vs rmdir() race Date: Fri, 1 Mar 2013 11:44:48 -0800 Message-Id: <20130301194358.650244539@linuxfoundation.org> X-Mailer: git-send-email 1.8.1.rc1.5.g7e0651a In-Reply-To: <20130301194351.913471337@linuxfoundation.org> References: <20130301194351.913471337@linuxfoundation.org> User-Agent: quilt/0.60-2.1.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1752 Lines: 61 3.8-stable review patch. If anyone has any objections, please let me know. ------------------ From: Li Zefan commit 71b5707e119653039e6e95213f00479668c79b75 upstream. In cgroup_exit() put_css_set_taskexit() is called without any lock, which might lead to accessing a freed cgroup: thread1 thread2 --------------------------------------------- exit() cgroup_exit() put_css_set_taskexit() atomic_dec(cgrp->count); rmdir(); /* not safe !! */ check_for_release(cgrp); rcu_read_lock() can be used to make sure the cgroup is alive. Signed-off-by: Li Zefan Signed-off-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman --- kernel/cgroup.c | 8 ++++++++ 1 file changed, 8 insertions(+) --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -426,12 +426,20 @@ static void __put_css_set(struct css_set struct cgroup *cgrp = link->cgrp; list_del(&link->cg_link_list); list_del(&link->cgrp_link_list); + + /* + * We may not be holding cgroup_mutex, and if cgrp->count is + * dropped to 0 the cgroup can be destroyed at any time, hence + * rcu_read_lock is used to keep it alive. + */ + rcu_read_lock(); if (atomic_dec_and_test(&cgrp->count) && notify_on_release(cgrp)) { if (taskexit) set_bit(CGRP_RELEASABLE, &cgrp->flags); check_for_release(cgrp); } + rcu_read_unlock(); kfree(link); } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/