1 files changed, 485 insertions, 0 deletions
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
new file mode 100644
index 000000000..20243682e
--- /dev/null
+++ b/kernel/pid_namespace.c
@@ -0,0 +1,485 @@
+// 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;
+/* 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 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;
+
+	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() misses EXIT_DEAD children, and EXIT_ZOMBIE
+	 * process whose parents processes are outside of the pid
+	 * namespace.  Such processes are created with setns()+fork().
+	 *
+	 * If those EXIT_ZOMBIE processes are not reaped by their
+	 * parents before their parents exit, they will be reparented
+	 * to pid_ns->child_reaper.  Thus pidns->child_reaper needs to
+	 * stay valid until they all go away.
+	 *
+	 * The code relies on the pid_ns->child_reaper ignoring
+	 * SIGCHILD to cause those EXIT_ZOMBIE processes to be
+	 * autoreaped if reparented.
+	 *
+	 * Semantically it is also desirable to wait for EXIT_ZOMBIE
+	 * processes before allowing the child_reaper to be reaped, as
+	 * that gives the invariant that when the init process of a
+	 * pid namespace is reaped all of the processes in the pid
+	 * namespace are gone.
+	 *
+	 * Once all of the other tasks are gone from the pid_namespace
+	 * free_pid() will awaken this task.
+	 */
+	for (;;) {
+		set_current_state(TASK_INTERRUPTIBLE);
+		if (pid_ns->pid_allocated == init_pids)
+			break;
+		/*
+		 * Release tasks_rcu_exit_srcu to avoid following deadlock:
+		 *
+		 * 1) TASK A unshare(CLONE_NEWPID)
+		 * 2) TASK A fork() twice -> TASK B (child reaper for new ns)
+		 *    and TASK C
+		 * 3) TASK B exits, kills TASK C, waits for TASK A to reap it
+		 * 4) TASK A calls synchronize_rcu_tasks()
+		 *                   -> synchronize_srcu(tasks_rcu_exit_srcu)
+		 * 5) *DEADLOCK*
+		 *
+		 * It is considered safe to release tasks_rcu_exit_srcu here
+		 * because we assume the current task can not be concurrently
+		 * reaped at this point.
+		 */
+		exit_tasks_rcu_stop();
+		schedule();
+		exit_tasks_rcu_start();
+	}
+	__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 *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 && !checkpoint_restore_ns_capable(pid_ns->user_ns))
+		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 nsset *nsset, struct ns_common *ns)
+{
+	struct nsproxy *nsproxy = nsset->nsproxy;
+	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(nsset->cred->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);