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 * A structure to encompass all bits needed to install
46 * a partial or complete new set of namespaces.
47 *
48 * If a new user namespace is requested cred will
49 * point to a modifiable set of credentials. If a pointer
50 * to a modifiable set is needed nsset_cred() must be
51 * used and tested.
52 */
53struct nsset {
54 unsigned flags;
55 struct nsproxy *nsproxy;
56 struct fs_struct *fs;
57 const struct cred *cred;
58};
59
60static inline struct cred *nsset_cred(struct nsset *set)
61{
62 if (set->flags & CLONE_NEWUSER)
63 return (struct cred *)set->cred;
64
65 return NULL;
66}
67
68/*
69 * the namespaces access rules are:
70 *
71 * 1. only current task is allowed to change tsk->nsproxy pointer or
72 * any pointer on the nsproxy itself. Current must hold the task_lock
73 * when changing tsk->nsproxy.
74 *
75 * 2. when accessing (i.e. reading) current task's namespaces - no
76 * precautions should be taken - just dereference the pointers
77 *
78 * 3. the access to other task namespaces is performed like this
79 * task_lock(task);
80 * nsproxy = task->nsproxy;
81 * if (nsproxy != NULL) {
82 * / *
83 * * work with the namespaces here
84 * * e.g. get the reference on one of them
85 * * /
86 * } / *
87 * * NULL task->nsproxy means that this task is
88 * * almost dead (zombie)
89 * * /
90 * task_unlock(task);
91 *
92 */
93
94int copy_namespaces(unsigned long flags, struct task_struct *tsk);
95void exit_task_namespaces(struct task_struct *tsk);
96void switch_task_namespaces(struct task_struct *tsk, struct nsproxy *new);
97void free_nsproxy(struct nsproxy *ns);
98int unshare_nsproxy_namespaces(unsigned long, struct nsproxy **,
99 struct cred *, struct fs_struct *);
100int __init nsproxy_cache_init(void);
101
102static inline void put_nsproxy(struct nsproxy *ns)
103{
104 if (atomic_dec_and_test(&ns->count)) {
105 free_nsproxy(ns);
106 }
107}
108
109static inline void get_nsproxy(struct nsproxy *ns)
110{
111 atomic_inc(&ns->count);
112}
113
114#endif
115

source code of linux/include/linux/nsproxy.h