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
8 struct mnt_namespace;
9 struct uts_namespace;
10 struct ipc_namespace;
11 struct pid_namespace;
12 struct cgroup_namespace;
13 struct 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 */
31 struct 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 cgroup_namespace *cgroup_ns;
39 };
40 extern struct nsproxy init_nsproxy;
41
42 /*
43 * the namespaces access rules are:
44 *
45 * 1. only current task is allowed to change tsk->nsproxy pointer or
46 * any pointer on the nsproxy itself. Current must hold the task_lock
47 * when changing tsk->nsproxy.
48 *
49 * 2. when accessing (i.e. reading) current task's namespaces - no
50 * precautions should be taken - just dereference the pointers
51 *
52 * 3. the access to other task namespaces is performed like this
53 * task_lock(task);
54 * nsproxy = task->nsproxy;
55 * if (nsproxy != NULL) {
56 * / *
57 * * work with the namespaces here
58 * * e.g. get the reference on one of them
59 * * /
60 * } / *
61 * * NULL task->nsproxy means that this task is
62 * * almost dead (zombie)
63 * * /
64 * task_unlock(task);
65 *
66 */
67
68 int copy_namespaces(unsigned long flags, struct task_struct *tsk);
69 void exit_task_namespaces(struct task_struct *tsk);
70 void switch_task_namespaces(struct task_struct *tsk, struct nsproxy *new);
71 void free_nsproxy(struct nsproxy *ns);
72 int unshare_nsproxy_namespaces(unsigned long, struct nsproxy **,
73 struct cred *, struct fs_struct *);
74 int __init nsproxy_cache_init(void);
75
76 static inline void put_nsproxy(struct nsproxy *ns)
77 {
78 if (atomic_dec_and_test(&ns->count)) {
79 free_nsproxy(ns);
80 }
81 }
82
83 static inline void get_nsproxy(struct nsproxy *ns)
84 {
85 atomic_inc(&ns->count);
86 }
87
88 #endif