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 
put_nsproxy(struct nsproxy * ns)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 
get_nsproxy(struct nsproxy * ns)83 static inline void get_nsproxy(struct nsproxy *ns)
84 {
85 	atomic_inc(&ns->count);
86 }
87 
88 #endif
89