kernel/pid_namespace.c - linux - Git at Google

 /*
  * 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/syscalls.h>
 #include <linux/err.h>
 #include <linux/acct.h>
 #include <linux/slab.h>
 #include <linux/proc_fs.h>
 #include <linux/reboot.h>
 #include <linux/export.h>

 #define BITS_PER_PAGE		(PAGE_SIZE*8)

 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;
 }

 /* 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 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;

 	kref_init(&ns->kref);
 	ns->level = level;
 	ns->parent = get_pid_ns(parent_pid_ns);

 	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);

 	err = pid_ns_prepare_proc(ns);
 	if (err)
 		goto out_put_parent_pid_ns;

 	return ns;

 out_put_parent_pid_ns:
 	put_pid_ns(parent_pid_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 destroy_pid_namespace(struct pid_namespace *ns)
 {
 	int i;

 	for (i = 0; i < PIDMAP_ENTRIES; i++)
 		kfree(ns->pidmap[i].page);
 	kmem_cache_free(pid_ns_cachep, ns);
 }

 struct pid_namespace *copy_pid_ns(unsigned long flags, struct pid_namespace *old_ns)
 {
 	if (!(flags & CLONE_NEWPID))
 		return get_pid_ns(old_ns);
 	if (flags & (CLONE_THREAD|CLONE_PARENT))
 		return ERR_PTR(-EINVAL);
 	return create_pid_namespace(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;

 	/* Ignore SIGCHLD causing any terminated children to autoreap */
 	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);

 	/* Firstly reap the EXIT_ZOMBIE children we may have. */
 	do {
 		clear_thread_flag(TIF_SIGPENDING);
 		rc = sys_wait4(-1, NULL, __WALL, NULL);
 	} while (rc != -ECHILD);

 	/*
 	 * sys_wait4() above can't reap the TASK_DEAD children.
 	 * Make sure they all go away, see __unhash_process().
 	 */
 	for (;;) {
 		bool need_wait = false;

 		read_lock(&tasklist_lock);
 		if (!list_empty(&current->children)) {
 			__set_current_state(TASK_UNINTERRUPTIBLE);
 			need_wait = true;
 		}
 		read_unlock(&tasklist_lock);

 		if (!need_wait)
 			break;
 		schedule();
 	}

 	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 ctl_table tmp = *table;

 	if (write && !capable(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 = &current->nsproxy->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 __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);
	/*
	* 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/syscalls.h>
	#include <linux/err.h>
	#include <linux/acct.h>
	#include <linux/slab.h>
	#include <linux/proc_fs.h>
	#include <linux/reboot.h>
	#include <linux/export.h>

	#define BITS_PER_PAGE (PAGE_SIZE*8)

	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;
	}

	/* 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 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;

	kref_init(&ns->kref);
	ns->level = level;
	ns->parent = get_pid_ns(parent_pid_ns);

	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);

	err = pid_ns_prepare_proc(ns);
	if (err)
	goto out_put_parent_pid_ns;

	return ns;

	out_put_parent_pid_ns:
	put_pid_ns(parent_pid_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 destroy_pid_namespace(struct pid_namespace *ns)
	{
	int i;

	for (i = 0; i < PIDMAP_ENTRIES; i++)
	kfree(ns->pidmap[i].page);
	kmem_cache_free(pid_ns_cachep, ns);
	}

	struct pid_namespace copy_pid_ns(unsigned long flags, struct pid_namespace old_ns)
	{
	if (!(flags & CLONE_NEWPID))
	return get_pid_ns(old_ns);
	if (flags & (CLONE_THREAD\|CLONE_PARENT))
	return ERR_PTR(-EINVAL);
	return create_pid_namespace(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;

	/* Ignore SIGCHLD causing any terminated children to autoreap */
	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);

	/* Firstly reap the EXIT_ZOMBIE children we may have. */
	do {
	clear_thread_flag(TIF_SIGPENDING);
	rc = sys_wait4(-1, NULL, __WALL, NULL);
	} while (rc != -ECHILD);

	/*
	* sys_wait4() above can't reap the TASK_DEAD children.
	* Make sure they all go away, see __unhash_process().
	*/
	for (;;) {
	bool need_wait = false;

	read_lock(&tasklist_lock);
	if (!list_empty(&current->children)) {
	__set_current_state(TASK_UNINTERRUPTIBLE);
	need_wait = true;
	}
	read_unlock(&tasklist_lock);

	if (!need_wait)
	break;
	schedule();
	}

	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 ctl_table tmp = *table;

	if (write && !capable(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 = &current->nsproxy->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 __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);