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/refcount.h>
   6 #include <linux/spinlock.h>
   7 #include <linux/sched.h>
   8
   9 struct mnt_namespace;
  10 struct uts_namespace;
  11 struct ipc_namespace;
  12 struct pid_namespace;
  13 struct cgroup_namespace;
  14 struct fs_struct;
  15
  16 /*
  17  * A structure to contain pointers to all per-process
  18  * namespaces - fs (mount), uts, network, sysvipc, etc.
  19  *
  20  * The pid namespace is an exception -- it's accessed using
  21  * task_active_pid_ns.  The pid namespace here is the
  22  * namespace that children will use.
  23  *
  24  * 'count' is the number of tasks holding a reference.
  25  * The count for each namespace, then, will be the number
  26  * of nsproxies pointing to it, not the number of tasks.
  27  *
  28  * The nsproxy is shared by tasks which share all namespaces.
  29  * As soon as a single namespace is cloned or unshared, the
  30  * nsproxy is copied.
  31  */
  32 struct nsproxy {
  33         refcount_t count;
  34         struct uts_namespace *uts_ns;
  35         struct ipc_namespace *ipc_ns;
  36         struct mnt_namespace *mnt_ns;
  37         struct pid_namespace *pid_ns_for_children;
  38         struct net           *net_ns;
  39         struct time_namespace *time_ns;
  40         struct time_namespace *time_ns_for_children;
  41         struct cgroup_namespace *cgroup_ns;
  42 };
  43 extern struct nsproxy init_nsproxy;
  44
  45 #define to_ns_common(__ns)                              \
  46         _Generic((__ns),                                \
  47                 struct cgroup_namespace *: &(__ns->ns), \
  48                 struct ipc_namespace *:    &(__ns->ns), \
  49                 struct net *:              &(__ns->ns), \
  50                 struct pid_namespace *:    &(__ns->ns), \
  51                 struct mnt_namespace *:    &(__ns->ns), \
  52                 struct time_namespace *:   &(__ns->ns), \
  53                 struct user_namespace *:   &(__ns->ns), \
  54                 struct uts_namespace *:    &(__ns->ns))
  55
  56 /*
  57  * A structure to encompass all bits needed to install
  58  * a partial or complete new set of namespaces.
  59  *
  60  * If a new user namespace is requested cred will
  61  * point to a modifiable set of credentials. If a pointer
  62  * to a modifiable set is needed nsset_cred() must be
  63  * used and tested.
  64  */
  65 struct nsset {
  66         unsigned flags;
  67         struct nsproxy *nsproxy;
  68         struct fs_struct *fs;
  69         const struct cred *cred;
  70 };
  71
  72 static inline struct cred *nsset_cred(struct nsset *set)
  73 {
  74         if (set->flags & CLONE_NEWUSER)
  75                 return (struct cred *)set->cred;
  76
  77         return NULL;
  78 }
  79
  80 /*
  81  * the namespaces access rules are:
  82  *
  83  *  1. only current task is allowed to change tsk->nsproxy pointer or
  84  *     any pointer on the nsproxy itself.  Current must hold the task_lock
  85  *     when changing tsk->nsproxy.
  86  *
  87  *  2. when accessing (i.e. reading) current task's namespaces - no
  88  *     precautions should be taken - just dereference the pointers
  89  *
  90  *  3. the access to other task namespaces is performed like this
  91  *     task_lock(task);
  92  *     nsproxy = task->nsproxy;
  93  *     if (nsproxy != NULL) {
  94  *             / *
  95  *               * work with the namespaces here
  96  *               * e.g. get the reference on one of them
  97  *               * /
  98  *     } / *
  99  *         * NULL task->nsproxy means that this task is
 100  *         * almost dead (zombie)
 101  *         * /
 102  *     task_unlock(task);
 103  *
 104  */
 105
 106 int copy_namespaces(unsigned long flags, struct task_struct *tsk);
 107 void exit_task_namespaces(struct task_struct *tsk);
 108 void switch_task_namespaces(struct task_struct *tsk, struct nsproxy *new);
 109 int exec_task_namespaces(void);
 110 void free_nsproxy(struct nsproxy *ns);
 111 int unshare_nsproxy_namespaces(unsigned long, struct nsproxy **,
 112         struct cred *, struct fs_struct *);
 113 int __init nsproxy_cache_init(void);
 114
 115 static inline void put_nsproxy(struct nsproxy *ns)
 116 {
 117         if (refcount_dec_and_test(&ns->count))
 118                 free_nsproxy(ns);
 119 }
 120
 121 static inline void get_nsproxy(struct nsproxy *ns)
 122 {
 123         refcount_inc(&ns->count);
 124 }
 125
 126 DEFINE_FREE(put_nsproxy, struct nsproxy *, if (_T) put_nsproxy(_T))
 127
 128 #endif