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1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _LINUX_NSPROXY_H
3#define _LINUX_NSPROXY_H
4
5#include <linux/spinlock.h>
6#include <linux/sched.h>
7
8struct mnt_namespace;
9struct uts_namespace;
10struct ipc_namespace;
11struct pid_namespace;
12struct cgroup_namespace;
13struct fs_struct;
14
15/*
16 * A structure to contain pointers to all per-process
17 * namespaces - fs (mount), uts, network, sysvipc, etc.
18 *
19 * The pid namespace is an exception -- it's accessed using
20 * task_active_pid_ns. The pid namespace here is the
21 * namespace that children will use.
22 *
23 * 'count' is the number of tasks holding a reference.
24 * The count for each namespace, then, will be the number
25 * of nsproxies pointing to it, not the number of tasks.
26 *
27 * The nsproxy is shared by tasks which share all namespaces.
28 * As soon as a single namespace is cloned or unshared, the
29 * nsproxy is copied.
30 */
31struct nsproxy {
32 atomic_t count;
33 struct uts_namespace *uts_ns;
34 struct ipc_namespace *ipc_ns;
35 struct mnt_namespace *mnt_ns;
36 struct pid_namespace *pid_ns_for_children;
37 struct net *net_ns;
38 struct time_namespace *time_ns;
39 struct time_namespace *time_ns_for_children;
40 struct cgroup_namespace *cgroup_ns;
41};
42extern struct nsproxy init_nsproxy;
43
44/*
45 * the namespaces access rules are:
46 *
47 * 1. only current task is allowed to change tsk->nsproxy pointer or
48 * any pointer on the nsproxy itself. Current must hold the task_lock
49 * when changing tsk->nsproxy.
50 *
51 * 2. when accessing (i.e. reading) current task's namespaces - no
52 * precautions should be taken - just dereference the pointers
53 *
54 * 3. the access to other task namespaces is performed like this
55 * task_lock(task);
56 * nsproxy = task->nsproxy;
57 * if (nsproxy != NULL) {
58 * / *
59 * * work with the namespaces here
60 * * e.g. get the reference on one of them
61 * * /
62 * } / *
63 * * NULL task->nsproxy means that this task is
64 * * almost dead (zombie)
65 * * /
66 * task_unlock(task);
67 *
68 */
69
70int copy_namespaces(unsigned long flags, struct task_struct *tsk);
71void exit_task_namespaces(struct task_struct *tsk);
72void switch_task_namespaces(struct task_struct *tsk, struct nsproxy *new);
73void free_nsproxy(struct nsproxy *ns);
74int unshare_nsproxy_namespaces(unsigned long, struct nsproxy **,
75 struct cred *, struct fs_struct *);
76int __init nsproxy_cache_init(void);
77
78static inline void put_nsproxy(struct nsproxy *ns)
79{
80 if (atomic_dec_and_test(&ns->count)) {
81 free_nsproxy(ns);
82 }
83}
84
85static inline void get_nsproxy(struct nsproxy *ns)
86{
87 atomic_inc(&ns->count);
88}
89
90#endif