From e65fcfd63a9a62baa5708484ff8edbe56eb3e7ec Mon Sep 17 00:00:00 2001
From: Paul Menage <menage@google.com>
Date: Tue, 26 May 2009 20:47:02 -0700
Subject: [PATCH] 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 <menage@google.com>
Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
net/sched/cls_cgroup.c | 22 +++++++++++-----------
1 file changed, 11 insertions(+), 11 deletions(-)
diff --git a/net/sched/cls_cgroup.c b/net/sched/cls_cgroup.c
index 91a3db4a76f83..cc29b44b1500e 100644
--- a/net/sched/cls_cgroup.c
+++ b/net/sched/cls_cgroup.c
@@ -104,8 +104,7 @@ 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
@@ -121,17 +120,18 @@ 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)
--
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