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 	refcount_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 };
42 extern 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  */
53 struct nsset {
54 	unsigned flags;
55 	struct nsproxy *nsproxy;
56 	struct fs_struct *fs;
57 	const struct cred *cred;
58 };
59 
nsset_cred(struct nsset * set)60 static 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 
94 int copy_namespaces(unsigned long flags, struct task_struct *tsk);
95 void exit_task_namespaces(struct task_struct *tsk);
96 void switch_task_namespaces(struct task_struct *tsk, struct nsproxy *new);
97 int exec_task_namespaces(void);
98 void free_nsproxy(struct nsproxy *ns);
99 int unshare_nsproxy_namespaces(unsigned long, struct nsproxy **,
100 	struct cred *, struct fs_struct *);
101 int __init nsproxy_cache_init(void);
102 
put_nsproxy(struct nsproxy * ns)103 static inline void put_nsproxy(struct nsproxy *ns)
104 {
105 	if (refcount_dec_and_test(&ns->count))
106 		free_nsproxy(ns);
107 }
108 
get_nsproxy(struct nsproxy * ns)109 static inline void get_nsproxy(struct nsproxy *ns)
110 {
111 	refcount_inc(&ns->count);
112 }
113 
114 #endif
115