LXR linux/include/linux/nsproxy.h

   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 cgroup_namespace *cgroup_ns;
  39};
  40extern 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
  68int copy_namespaces(unsigned long flags, struct task_struct *tsk);
  69void exit_task_namespaces(struct task_struct *tsk);
  70void switch_task_namespaces(struct task_struct *tsk, struct nsproxy *new);
  71void free_nsproxy(struct nsproxy *ns);
  72int unshare_nsproxy_namespaces(unsigned long, struct nsproxy **,
  73        struct cred *, struct fs_struct *);
  74int __init nsproxy_cache_init(void);
  75
  76static inline void put_nsproxy(struct nsproxy *ns)
  77{
  78        if (atomic_dec_and_test(&ns->count)) {
  79                free_nsproxy(ns);
  80        }
  81}
  82
  83static inline void get_nsproxy(struct nsproxy *ns)
  84{
  85        atomic_inc(&ns->count);
  86}
  87
  88#endif
  89