077130c0cf
The problem: proc_net files remember which network namespace the are against but do not remember hold a reference count (as that would pin the network namespace). So we currently have a small window where the reference count on a network namespace may be incremented when opening a /proc file when it has already gone to zero. To fix this introduce maybe_get_net and get_proc_net. maybe_get_net increments the network namespace reference count only if it is greater then zero, ensuring we don't increment a reference count after it has gone to zero. get_proc_net handles all of the magic to go from a proc inode to the network namespace instance and call maybe_get_net on it. PROC_NET the old accessor is removed so that we don't get confused and use the wrong helper function. Then I fix up the callers to use get_proc_net and handle the case case where get_proc_net returns NULL. In that case I return -ENXIO because effectively the network namespace has already gone away so the files we are trying to access don't exist anymore. Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Acked-by: Paul E. McKenney <paulmck@us.ibm.com> Signed-off-by: David S. Miller <davem@davemloft.net>
97 lines
2.2 KiB
C
97 lines
2.2 KiB
C
/*
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* Operations on the network namespace
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*/
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#ifndef __NET_NET_NAMESPACE_H
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#define __NET_NET_NAMESPACE_H
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#include <asm/atomic.h>
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#include <linux/workqueue.h>
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#include <linux/list.h>
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struct proc_dir_entry;
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struct net {
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atomic_t count; /* To decided when the network
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* namespace should be freed.
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*/
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atomic_t use_count; /* To track references we
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* destroy on demand
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*/
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struct list_head list; /* list of network namespaces */
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struct work_struct work; /* work struct for freeing */
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struct proc_dir_entry *proc_net;
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struct proc_dir_entry *proc_net_stat;
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struct proc_dir_entry *proc_net_root;
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struct list_head dev_base_head;
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struct hlist_head *dev_name_head;
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struct hlist_head *dev_index_head;
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};
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#ifdef CONFIG_NET
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/* Init's network namespace */
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extern struct net init_net;
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#define INIT_NET_NS(net_ns) .net_ns = &init_net,
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#else
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#define INIT_NET_NS(net_ns)
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#endif
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extern struct list_head net_namespace_list;
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extern void __put_net(struct net *net);
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static inline struct net *get_net(struct net *net)
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{
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atomic_inc(&net->count);
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return net;
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}
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static inline struct net *maybe_get_net(struct net *net)
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{
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/* Used when we know struct net exists but we
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* aren't guaranteed a previous reference count
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* exists. If the reference count is zero this
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* function fails and returns NULL.
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*/
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if (!atomic_inc_not_zero(&net->count))
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net = NULL;
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return net;
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}
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static inline void put_net(struct net *net)
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{
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if (atomic_dec_and_test(&net->count))
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__put_net(net);
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}
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static inline struct net *hold_net(struct net *net)
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{
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atomic_inc(&net->use_count);
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return net;
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}
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static inline void release_net(struct net *net)
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{
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atomic_dec(&net->use_count);
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}
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extern void net_lock(void);
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extern void net_unlock(void);
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#define for_each_net(VAR) \
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list_for_each_entry(VAR, &net_namespace_list, list)
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struct pernet_operations {
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struct list_head list;
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int (*init)(struct net *net);
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void (*exit)(struct net *net);
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};
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extern int register_pernet_subsys(struct pernet_operations *);
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extern void unregister_pernet_subsys(struct pernet_operations *);
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extern int register_pernet_device(struct pernet_operations *);
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extern void unregister_pernet_device(struct pernet_operations *);
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#endif /* __NET_NET_NAMESPACE_H */
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