From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755895Ab2LCO4V (ORCPT ); Mon, 3 Dec 2012 09:56:21 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:43582 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932109Ab2LCOfs (ORCPT ); Mon, 3 Dec 2012 09:35:48 -0500 Message-Id: <20121203143147.609467839@decadent.org.uk> User-Agent: quilt/0.60-1 Date: Mon, 03 Dec 2012 14:31:52 +0000 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Tejun Heo , "Serge E. Hallyn" , Aristeu Rozanski , Li Zefan Subject: [ 06/89] device_cgroup: fix RCU usage In-Reply-To: <20121203143146.549859007@decadent.org.uk> X-SA-Exim-Connect-IP: 2001:470:1f08:1539:21c:bfff:fe03:f805 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Tejun Heo commit 201e72acb2d3821e2de9ce6091e98859c316b29a upstream. dev_cgroup->exceptions is protected with devcgroup_mutex for writes and RCU for reads; however, RCU usage isn't correct. * dev_exception_clean() doesn't use RCU variant of list_del() and kfree(). The function can race with may_access() and may_access() may end up dereferencing already freed memory. Use list_del_rcu() and kfree_rcu() instead. * may_access() may be called only with RCU read locked but doesn't use RCU safe traversal over ->exceptions. Use list_for_each_entry_rcu(). Signed-off-by: Tejun Heo Acked-by: Serge E. Hallyn Cc: Aristeu Rozanski Cc: Li Zefan [bwh: Backported to 3.2: - Adjust context - Exception list is called whitelist] Signed-off-by: Ben Hutchings --- security/device_cgroup.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/security/device_cgroup.c +++ b/security/device_cgroup.c @@ -202,8 +202,8 @@ static void devcgroup_destroy(struct cgr dev_cgroup = cgroup_to_devcgroup(cgroup); list_for_each_entry_safe(wh, tmp, &dev_cgroup->whitelist, list) { - list_del(&wh->list); - kfree(wh); + list_del_rcu(&wh->list); + kfree_rcu(wh, rcu); } kfree(dev_cgroup); } @@ -278,7 +278,7 @@ static int may_access_whitelist(struct d { struct dev_whitelist_item *whitem; - list_for_each_entry(whitem, &c->whitelist, list) { + list_for_each_entry_rcu(whitem, &c->whitelist, list) { if (whitem->type & DEV_ALL) return 1; if ((refwh->type & DEV_BLOCK) && !(whitem->type & DEV_BLOCK))