Messages in this thread Patch in this message | | | From | Paul Menage <> | Subject | [PATCH] cls_cgroup: read classid atomically in classifier | Date | Tue, 26 May 2009 12:59:11 -0700 |
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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>
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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)
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