cls_cgroup: Fix rcu lockdep warning
Dave reported an rcu lockdep warning on 2.6.35.4 kernel task->cgroups and task->cgroups->subsys[i] are protected by RCU. So we avoid accessing invalid pointers here. This might happen, for example, when you are deref-ing those pointers while someone move @task from one cgroup to another. Reported-by: Dave Jones <davej@redhat.com> Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -27,11 +27,17 @@ struct cgroup_cls_state
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#ifdef CONFIG_NET_CLS_CGROUP
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static inline u32 task_cls_classid(struct task_struct *p)
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{
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int classid;
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if (in_interrupt())
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return 0;
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return container_of(task_subsys_state(p, net_cls_subsys_id),
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struct cgroup_cls_state, css)->classid;
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rcu_read_lock();
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classid = container_of(task_subsys_state(p, net_cls_subsys_id),
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struct cgroup_cls_state, css)->classid;
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rcu_read_unlock();
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return classid;
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}
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#else
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extern int net_cls_subsys_id;
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