--- /dev/null
+/*
+ * Pid namespaces
+ *
+ * Authors:
+ * (C) 2007 Pavel Emelyanov <xemul@openvz.org>, OpenVZ, SWsoft Inc.
+ * (C) 2007 Sukadev Bhattiprolu <sukadev@us.ibm.com>, IBM
+ * Many thanks to Oleg Nesterov for comments and help
+ *
+ */
+
+#include <linux/pid.h>
+#include <linux/pid_namespace.h>
+#include <linux/user_namespace.h>
+#include <linux/syscalls.h>
+#include <linux/err.h>
+#include <linux/acct.h>
+#include <linux/slab.h>
+#include <linux/proc_ns.h>
+#include <linux/reboot.h>
+#include <linux/export.h>
+
+struct pid_cache {
+ int nr_ids;
+ char name[16];
+ struct kmem_cache *cachep;
+ struct list_head list;
+};
+
+static LIST_HEAD(pid_caches_lh);
+static DEFINE_MUTEX(pid_caches_mutex);
+static struct kmem_cache *pid_ns_cachep;
+
+/*
+ * creates the kmem cache to allocate pids from.
+ * @nr_ids: the number of numerical ids this pid will have to carry
+ */
+
+static struct kmem_cache *create_pid_cachep(int nr_ids)
+{
+ struct pid_cache *pcache;
+ struct kmem_cache *cachep;
+
+ mutex_lock(&pid_caches_mutex);
+ list_for_each_entry(pcache, &pid_caches_lh, list)
+ if (pcache->nr_ids == nr_ids)
+ goto out;
+
+ pcache = kmalloc(sizeof(struct pid_cache), GFP_KERNEL);
+ if (pcache == NULL)
+ goto err_alloc;
+
+ snprintf(pcache->name, sizeof(pcache->name), "pid_%d", nr_ids);
+ cachep = kmem_cache_create(pcache->name,
+ sizeof(struct pid) + (nr_ids - 1) * sizeof(struct upid),
+ 0, SLAB_HWCACHE_ALIGN, NULL);
+ if (cachep == NULL)
+ goto err_cachep;
+
+ pcache->nr_ids = nr_ids;
+ pcache->cachep = cachep;
+ list_add(&pcache->list, &pid_caches_lh);
+out:
+ mutex_unlock(&pid_caches_mutex);
+ return pcache->cachep;
+
+err_cachep:
+ kfree(pcache);
+err_alloc:
+ mutex_unlock(&pid_caches_mutex);
+ return NULL;
+}
+
+static void proc_cleanup_work(struct work_struct *work)
+{
+ struct pid_namespace *ns = container_of(work, struct pid_namespace, proc_work);
+ pid_ns_release_proc(ns);
+}
+
+/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
+#define MAX_PID_NS_LEVEL 32
+
+static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns,
+ struct pid_namespace *parent_pid_ns)
+{
+ struct pid_namespace *ns;
+ unsigned int level = parent_pid_ns->level + 1;
+ int i;
+ int err;
+
+ if (level > MAX_PID_NS_LEVEL) {
+ err = -EINVAL;
+ goto out;
+ }
+
+ err = -ENOMEM;
+ ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
+ if (ns == NULL)
+ goto out;
+
+ ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
+ if (!ns->pidmap[0].page)
+ goto out_free;
+
+ ns->pid_cachep = create_pid_cachep(level + 1);
+ if (ns->pid_cachep == NULL)
+ goto out_free_map;
+
+ err = ns_alloc_inum(&ns->ns);
+ if (err)
+ goto out_free_map;
+ ns->ns.ops = &pidns_operations;
+
+ kref_init(&ns->kref);
+ ns->level = level;
+ ns->parent = get_pid_ns(parent_pid_ns);
+ ns->user_ns = get_user_ns(user_ns);
+ ns->nr_hashed = PIDNS_HASH_ADDING;
+ INIT_WORK(&ns->proc_work, proc_cleanup_work);
+
+ set_bit(0, ns->pidmap[0].page);
+ atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1);
+
+ for (i = 1; i < PIDMAP_ENTRIES; i++)
+ atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE);
+
+ return ns;
+
+out_free_map:
+ kfree(ns->pidmap[0].page);
+out_free:
+ kmem_cache_free(pid_ns_cachep, ns);
+out:
+ return ERR_PTR(err);
+}
+
+static void delayed_free_pidns(struct rcu_head *p)
+{
+ kmem_cache_free(pid_ns_cachep,
+ container_of(p, struct pid_namespace, rcu));
+}
+
+static void destroy_pid_namespace(struct pid_namespace *ns)
+{
+ int i;
+
+ ns_free_inum(&ns->ns);
+ for (i = 0; i < PIDMAP_ENTRIES; i++)
+ kfree(ns->pidmap[i].page);
+ put_user_ns(ns->user_ns);
+ call_rcu(&ns->rcu, delayed_free_pidns);
+}
+
+struct pid_namespace *copy_pid_ns(unsigned long flags,
+ struct user_namespace *user_ns, struct pid_namespace *old_ns)
+{
+ if (!(flags & CLONE_NEWPID))
+ return get_pid_ns(old_ns);
+ if (task_active_pid_ns(current) != old_ns)
+ return ERR_PTR(-EINVAL);
+ return create_pid_namespace(user_ns, old_ns);
+}
+
+static void free_pid_ns(struct kref *kref)
+{
+ struct pid_namespace *ns;
+
+ ns = container_of(kref, struct pid_namespace, kref);
+ destroy_pid_namespace(ns);
+}
+
+void put_pid_ns(struct pid_namespace *ns)
+{
+ struct pid_namespace *parent;
+
+ while (ns != &init_pid_ns) {
+ parent = ns->parent;
+ if (!kref_put(&ns->kref, free_pid_ns))
+ break;
+ ns = parent;
+ }
+}
+EXPORT_SYMBOL_GPL(put_pid_ns);
+
+void zap_pid_ns_processes(struct pid_namespace *pid_ns)
+{
+ int nr;
+ int rc;
+ struct task_struct *task, *me = current;
+ int init_pids = thread_group_leader(me) ? 1 : 2;
+
+ /* Don't allow any more processes into the pid namespace */
+ disable_pid_allocation(pid_ns);
+
+ /*
+ * Ignore SIGCHLD causing any terminated children to autoreap.
+ * This speeds up the namespace shutdown, plus see the comment
+ * below.
+ */
+ spin_lock_irq(&me->sighand->siglock);
+ me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN;
+ spin_unlock_irq(&me->sighand->siglock);
+
+ /*
+ * The last thread in the cgroup-init thread group is terminating.
+ * Find remaining pid_ts in the namespace, signal and wait for them
+ * to exit.
+ *
+ * Note: This signals each threads in the namespace - even those that
+ * belong to the same thread group, To avoid this, we would have
+ * to walk the entire tasklist looking a processes in this
+ * namespace, but that could be unnecessarily expensive if the
+ * pid namespace has just a few processes. Or we need to
+ * maintain a tasklist for each pid namespace.
+ *
+ */
+ read_lock(&tasklist_lock);
+ nr = next_pidmap(pid_ns, 1);
+ while (nr > 0) {
+ rcu_read_lock();
+
+ task = pid_task(find_vpid(nr), PIDTYPE_PID);
+ if (task && !__fatal_signal_pending(task))
+ send_sig_info(SIGKILL, SEND_SIG_FORCED, task);
+
+ rcu_read_unlock();
+
+ nr = next_pidmap(pid_ns, nr);
+ }
+ read_unlock(&tasklist_lock);
+
+ /*
+ * Reap the EXIT_ZOMBIE children we had before we ignored SIGCHLD.
+ * sys_wait4() will also block until our children traced from the
+ * parent namespace are detached and become EXIT_DEAD.
+ */
+ do {
+ clear_thread_flag(TIF_SIGPENDING);
+ rc = sys_wait4(-1, NULL, __WALL, NULL);
+ } while (rc != -ECHILD);
+
+ /*
+ * sys_wait4() above can't reap the EXIT_DEAD children but we do not
+ * really care, we could reparent them to the global init. We could
+ * exit and reap ->child_reaper even if it is not the last thread in
+ * this pid_ns, free_pid(nr_hashed == 0) calls proc_cleanup_work(),
+ * pid_ns can not go away until proc_kill_sb() drops the reference.
+ *
+ * But this ns can also have other tasks injected by setns()+fork().
+ * Again, ignoring the user visible semantics we do not really need
+ * to wait until they are all reaped, but they can be reparented to
+ * us and thus we need to ensure that pid->child_reaper stays valid
+ * until they all go away. See free_pid()->wake_up_process().
+ *
+ * We rely on ignored SIGCHLD, an injected zombie must be autoreaped
+ * if reparented.
+ */
+ for (;;) {
+ set_current_state(TASK_UNINTERRUPTIBLE);
+ if (pid_ns->nr_hashed == init_pids)
+ break;
+ schedule();
+ }
+ __set_current_state(TASK_RUNNING);
+
+ if (pid_ns->reboot)
+ current->signal->group_exit_code = pid_ns->reboot;
+
+ acct_exit_ns(pid_ns);
+ return;
+}
+
+#ifdef CONFIG_CHECKPOINT_RESTORE
+static int pid_ns_ctl_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ struct pid_namespace *pid_ns = task_active_pid_ns(current);
+ struct ctl_table tmp = *table;
+
+ if (write && !ns_capable(pid_ns->user_ns, CAP_SYS_ADMIN))
+ return -EPERM;
+
+ /*
+ * Writing directly to ns' last_pid field is OK, since this field
+ * is volatile in a living namespace anyway and a code writing to
+ * it should synchronize its usage with external means.
+ */
+
+ tmp.data = &pid_ns->last_pid;
+ return proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
+}
+
+extern int pid_max;
+static int zero = 0;
+static struct ctl_table pid_ns_ctl_table[] = {
+ {
+ .procname = "ns_last_pid",
+ .maxlen = sizeof(int),
+ .mode = 0666, /* permissions are checked in the handler */
+ .proc_handler = pid_ns_ctl_handler,
+ .extra1 = &zero,
+ .extra2 = &pid_max,
+ },
+ { }
+};
+static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } };
+#endif /* CONFIG_CHECKPOINT_RESTORE */
+
+int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
+{
+ if (pid_ns == &init_pid_ns)
+ return 0;
+
+ switch (cmd) {
+ case LINUX_REBOOT_CMD_RESTART2:
+ case LINUX_REBOOT_CMD_RESTART:
+ pid_ns->reboot = SIGHUP;
+ break;
+
+ case LINUX_REBOOT_CMD_POWER_OFF:
+ case LINUX_REBOOT_CMD_HALT:
+ pid_ns->reboot = SIGINT;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ read_lock(&tasklist_lock);
+ force_sig(SIGKILL, pid_ns->child_reaper);
+ read_unlock(&tasklist_lock);
+
+ do_exit(0);
+
+ /* Not reached */
+ return 0;
+}
+
+static inline struct pid_namespace *to_pid_ns(struct ns_common *ns)
+{
+ return container_of(ns, struct pid_namespace, ns);
+}
+
+static struct ns_common *pidns_get(struct task_struct *task)
+{
+ struct pid_namespace *ns;
+
+ rcu_read_lock();
+ ns = task_active_pid_ns(task);
+ if (ns)
+ get_pid_ns(ns);
+ rcu_read_unlock();
+
+ return ns ? &ns->ns : NULL;
+}
+
+static void pidns_put(struct ns_common *ns)
+{
+ put_pid_ns(to_pid_ns(ns));
+}
+
+static int pidns_install(struct nsproxy *nsproxy, struct ns_common *ns)
+{
+ struct pid_namespace *active = task_active_pid_ns(current);
+ struct pid_namespace *ancestor, *new = to_pid_ns(ns);
+
+ if (!ns_capable(new->user_ns, CAP_SYS_ADMIN) ||
+ !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
+ return -EPERM;
+
+ /*
+ * Only allow entering the current active pid namespace
+ * or a child of the current active pid namespace.
+ *
+ * This is required for fork to return a usable pid value and
+ * this maintains the property that processes and their
+ * children can not escape their current pid namespace.
+ */
+ if (new->level < active->level)
+ return -EINVAL;
+
+ ancestor = new;
+ while (ancestor->level > active->level)
+ ancestor = ancestor->parent;
+ if (ancestor != active)
+ return -EINVAL;
+
+ put_pid_ns(nsproxy->pid_ns_for_children);
+ nsproxy->pid_ns_for_children = get_pid_ns(new);
+ return 0;
+}
+
+const struct proc_ns_operations pidns_operations = {
+ .name = "pid",
+ .type = CLONE_NEWPID,
+ .get = pidns_get,
+ .put = pidns_put,
+ .install = pidns_install,
+};
+
+static __init int pid_namespaces_init(void)
+{
+ pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
+
+#ifdef CONFIG_CHECKPOINT_RESTORE
+ register_sysctl_paths(kern_path, pid_ns_ctl_table);
+#endif
+ return 0;
+}
+
+__initcall(pid_namespaces_init);
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