diff options
Diffstat (limited to 'kernel/pid_namespace.c')
| -rw-r--r-- | kernel/pid_namespace.c | 469 |
1 files changed, 469 insertions, 0 deletions
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c new file mode 100644 index 000000000..33de14435 --- /dev/null +++ b/kernel/pid_namespace.c @@ -0,0 +1,469 @@ +/* + * 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/cred.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> +#include <linux/sched/task.h> +#include <linux/sched/signal.h> +#include <linux/idr.h> + +static DEFINE_MUTEX(pid_caches_mutex); +static struct kmem_cache *pid_ns_cachep; +/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */ +#define MAX_PID_NS_LEVEL 32 +/* Write once array, filled from the beginning. */ +static struct kmem_cache *pid_cache[MAX_PID_NS_LEVEL]; + +/* + * creates the kmem cache to allocate pids from. + * @level: pid namespace level + */ + +static struct kmem_cache *create_pid_cachep(unsigned int level) +{ + /* Level 0 is init_pid_ns.pid_cachep */ + struct kmem_cache **pkc = &pid_cache[level - 1]; + struct kmem_cache *kc; + char name[4 + 10 + 1]; + unsigned int len; + + kc = READ_ONCE(*pkc); + if (kc) + return kc; + + snprintf(name, sizeof(name), "pid_%u", level + 1); + len = sizeof(struct pid) + level * sizeof(struct upid); + mutex_lock(&pid_caches_mutex); + /* Name collision forces to do allocation under mutex. */ + if (!*pkc) + *pkc = kmem_cache_create(name, len, 0, + SLAB_HWCACHE_ALIGN | SLAB_ACCOUNT, 0); + mutex_unlock(&pid_caches_mutex); + /* current can fail, but someone else can succeed. */ + return READ_ONCE(*pkc); +} + +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); +} + +static struct ucounts *inc_pid_namespaces(struct user_namespace *ns) +{ + return inc_ucount(ns, current_euid(), UCOUNT_PID_NAMESPACES); +} + +static void dec_pid_namespaces(struct ucounts *ucounts) +{ + dec_ucount(ucounts, UCOUNT_PID_NAMESPACES); +} + +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; + struct ucounts *ucounts; + int err; + + err = -EINVAL; + if (!in_userns(parent_pid_ns->user_ns, user_ns)) + goto out; + + err = -ENOSPC; + if (level > MAX_PID_NS_LEVEL) + goto out; + ucounts = inc_pid_namespaces(user_ns); + if (!ucounts) + goto out; + + err = -ENOMEM; + ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL); + if (ns == NULL) + goto out_dec; + + idr_init(&ns->idr); + + ns->pid_cachep = create_pid_cachep(level); + if (ns->pid_cachep == NULL) + goto out_free_idr; + + err = ns_alloc_inum(&ns->ns); + if (err) + goto out_free_idr; + 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->ucounts = ucounts; + ns->pid_allocated = PIDNS_ADDING; + INIT_WORK(&ns->proc_work, proc_cleanup_work); + + return ns; + +out_free_idr: + idr_destroy(&ns->idr); + kmem_cache_free(pid_ns_cachep, ns); +out_dec: + dec_pid_namespaces(ucounts); +out: + return ERR_PTR(err); +} + +static void delayed_free_pidns(struct rcu_head *p) +{ + struct pid_namespace *ns = container_of(p, struct pid_namespace, rcu); + + dec_pid_namespaces(ns->ucounts); + put_user_ns(ns->user_ns); + + kmem_cache_free(pid_ns_cachep, ns); +} + +static void destroy_pid_namespace(struct pid_namespace *ns) +{ + ns_free_inum(&ns->ns); + + idr_destroy(&ns->idr); + 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; + struct pid *pid; + + /* 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. + * + */ + rcu_read_lock(); + read_lock(&tasklist_lock); + nr = 2; + idr_for_each_entry_continue(&pid_ns->idr, pid, nr) { + task = pid_task(pid, PIDTYPE_PID); + if (task && !__fatal_signal_pending(task)) + send_sig_info(SIGKILL, SEND_SIG_FORCED, task); + } + read_unlock(&tasklist_lock); + rcu_read_unlock(); + + /* + * Reap the EXIT_ZOMBIE children we had before we ignored SIGCHLD. + * kernel_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 = kernel_wait4(-1, NULL, __WALL, NULL); + } while (rc != -ECHILD); + + /* + * kernel_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(pid_allocated == 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_INTERRUPTIBLE); + if (pid_ns->pid_allocated == 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; + int ret, next; + + 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. + */ + + next = idr_get_cursor(&pid_ns->idr) - 1; + + tmp.data = &next; + ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos); + if (!ret && write) + idr_set_cursor(&pid_ns->idr, next + 1); + + return ret; +} + +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); + send_sig(SIGKILL, pid_ns->child_reaper, 1); + 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 struct ns_common *pidns_for_children_get(struct task_struct *task) +{ + struct pid_namespace *ns = NULL; + + task_lock(task); + if (task->nsproxy) { + ns = task->nsproxy->pid_ns_for_children; + get_pid_ns(ns); + } + task_unlock(task); + + if (ns) { + read_lock(&tasklist_lock); + if (!ns->child_reaper) { + put_pid_ns(ns); + ns = NULL; + } + read_unlock(&tasklist_lock); + } + + 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; +} + +static struct ns_common *pidns_get_parent(struct ns_common *ns) +{ + struct pid_namespace *active = task_active_pid_ns(current); + struct pid_namespace *pid_ns, *p; + + /* See if the parent is in the current namespace */ + pid_ns = p = to_pid_ns(ns)->parent; + for (;;) { + if (!p) + return ERR_PTR(-EPERM); + if (p == active) + break; + p = p->parent; + } + + return &get_pid_ns(pid_ns)->ns; +} + +static struct user_namespace *pidns_owner(struct ns_common *ns) +{ + return to_pid_ns(ns)->user_ns; +} + +const struct proc_ns_operations pidns_operations = { + .name = "pid", + .type = CLONE_NEWPID, + .get = pidns_get, + .put = pidns_put, + .install = pidns_install, + .owner = pidns_owner, + .get_parent = pidns_get_parent, +}; + +const struct proc_ns_operations pidns_for_children_operations = { + .name = "pid_for_children", + .real_ns_name = "pid", + .type = CLONE_NEWPID, + .get = pidns_for_children_get, + .put = pidns_put, + .install = pidns_install, + .owner = pidns_owner, + .get_parent = pidns_get_parent, +}; + +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); |