// SPDX-License-Identifier: GPL-2.0-only/* * 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, 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))			group_send_sig_info(SIGKILL, SEND_SIG_PRIV, task, PIDTYPE_MAX);	}	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_RESTOREstatic 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 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 = SYSCTL_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);