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
   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