From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757994AbZEZUA1 (ORCPT ); Tue, 26 May 2009 16:00:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756753AbZEZUAM (ORCPT ); Tue, 26 May 2009 16:00:12 -0400 Received: from smtp-out.google.com ([216.239.33.17]:55552 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756686AbZEZUAK (ORCPT ); Tue, 26 May 2009 16:00:10 -0400 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=from:subject:to:cc:date:message-id:user-agent: mime-version:content-type:content-transfer-encoding:x-system-of-record; b=ZxmTV+0pAaol71xmmCIeELvzbKXMUpRZviyQbm6ebicPOk1ZIQsdx0JxHxWRtoQrC VtNr8Q2ueljm3ehoiZ1vQ== From: Paul Menage Subject: [PATCH] cls_cgroup: read classid atomically in classifier To: lizf@cn.fujitsu.com, akpm@linux-foundation.org, davem@davemloft.net, tgraf@suug.ch Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org Date: Tue, 26 May 2009 12:59:11 -0700 Message-ID: <20090526195840.8464.36548.stgit@menage.mtv.corp.google.com> User-Agent: StGIT/0.14.3 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org cls_cgroup: read classid atomically in classifier Avoid reading the unsynchronized value cs->classid multiple times, since it could change concurrently from non-zero to zero; this would result in the classifier returning a positive result with a bogus (zero) classid. Signed-off-by: Paul Menage Reviewed-by: Li Zefan --- Fixes a whitespace issue from the previous version of the patch net/sched/cls_cgroup.c | 22 +++++++++++----------- 1 files changed, 11 insertions(+), 11 deletions(-) diff --git a/net/sched/cls_cgroup.c b/net/sched/cls_cgroup.c index 1ab4542..0f815cc 100644 --- a/net/sched/cls_cgroup.c +++ b/net/sched/cls_cgroup.c @@ -98,8 +98,7 @@ static int cls_cgroup_classify(struct sk_buff *skb, struct tcf_proto *tp, struct tcf_result *res) { struct cls_cgroup_head *head = tp->root; - struct cgroup_cls_state *cs; - int ret = 0; + u32 classid; /* * Due to the nature of the classifier it is required to ignore all @@ -115,17 +114,18 @@ static int cls_cgroup_classify(struct sk_buff *skb, struct tcf_proto *tp, return -1; rcu_read_lock(); - cs = task_cls_state(current); - if (cs->classid && tcf_em_tree_match(skb, &head->ematches, NULL)) { - res->classid = cs->classid; - res->class = 0; - ret = tcf_exts_exec(skb, &head->exts, res); - } else - ret = -1; - + classid = task_cls_state(current)->classid; rcu_read_unlock(); - return ret; + if (!classid) + return -1; + + if (!tcf_em_tree_match(skb, &head->ematches, NULL)) + return -1; + + res->classid = classid; + res->class = 0; + return tcf_exts_exec(skb, &head->exts, res); } static unsigned long cls_cgroup_get(struct tcf_proto *tp, u32 handle)