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6dfeff09d5
There's really no overlap between uapi/linux/wait.h and linux/wait.h. There are two files which rely on the uapi file being implcitly included, so explicitly include it there and remove it from the main header file. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev> Reviewed-by: Christian Brauner <brauner@kernel.org>
478 lines
12 KiB
C
478 lines
12 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Pid namespaces
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*
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* Authors:
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* (C) 2007 Pavel Emelyanov <xemul@openvz.org>, OpenVZ, SWsoft Inc.
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* (C) 2007 Sukadev Bhattiprolu <sukadev@us.ibm.com>, IBM
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* Many thanks to Oleg Nesterov for comments and help
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*
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*/
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#include <linux/pid.h>
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#include <linux/pid_namespace.h>
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#include <linux/user_namespace.h>
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#include <linux/syscalls.h>
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#include <linux/cred.h>
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#include <linux/err.h>
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#include <linux/acct.h>
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#include <linux/slab.h>
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#include <linux/proc_ns.h>
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#include <linux/reboot.h>
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#include <linux/export.h>
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#include <linux/sched/task.h>
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#include <linux/sched/signal.h>
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#include <linux/idr.h>
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#include <uapi/linux/wait.h>
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#include "pid_sysctl.h"
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static DEFINE_MUTEX(pid_caches_mutex);
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static struct kmem_cache *pid_ns_cachep;
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/* Write once array, filled from the beginning. */
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static struct kmem_cache *pid_cache[MAX_PID_NS_LEVEL];
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/*
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* creates the kmem cache to allocate pids from.
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* @level: pid namespace level
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*/
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static struct kmem_cache *create_pid_cachep(unsigned int level)
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{
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/* Level 0 is init_pid_ns.pid_cachep */
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struct kmem_cache **pkc = &pid_cache[level - 1];
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struct kmem_cache *kc;
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char name[4 + 10 + 1];
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unsigned int len;
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kc = READ_ONCE(*pkc);
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if (kc)
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return kc;
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snprintf(name, sizeof(name), "pid_%u", level + 1);
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len = struct_size_t(struct pid, numbers, level + 1);
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mutex_lock(&pid_caches_mutex);
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/* Name collision forces to do allocation under mutex. */
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if (!*pkc)
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*pkc = kmem_cache_create(name, len, 0,
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SLAB_HWCACHE_ALIGN | SLAB_ACCOUNT, NULL);
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mutex_unlock(&pid_caches_mutex);
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/* current can fail, but someone else can succeed. */
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return READ_ONCE(*pkc);
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}
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static struct ucounts *inc_pid_namespaces(struct user_namespace *ns)
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{
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return inc_ucount(ns, current_euid(), UCOUNT_PID_NAMESPACES);
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}
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static void dec_pid_namespaces(struct ucounts *ucounts)
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{
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dec_ucount(ucounts, UCOUNT_PID_NAMESPACES);
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}
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static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns,
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struct pid_namespace *parent_pid_ns)
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{
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struct pid_namespace *ns;
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unsigned int level = parent_pid_ns->level + 1;
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struct ucounts *ucounts;
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int err;
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err = -EINVAL;
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if (!in_userns(parent_pid_ns->user_ns, user_ns))
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goto out;
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err = -ENOSPC;
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if (level > MAX_PID_NS_LEVEL)
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goto out;
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ucounts = inc_pid_namespaces(user_ns);
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if (!ucounts)
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goto out;
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err = -ENOMEM;
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ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
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if (ns == NULL)
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goto out_dec;
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idr_init(&ns->idr);
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ns->pid_cachep = create_pid_cachep(level);
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if (ns->pid_cachep == NULL)
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goto out_free_idr;
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err = ns_alloc_inum(&ns->ns);
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if (err)
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goto out_free_idr;
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ns->ns.ops = &pidns_operations;
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refcount_set(&ns->ns.count, 1);
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ns->level = level;
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ns->parent = get_pid_ns(parent_pid_ns);
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ns->user_ns = get_user_ns(user_ns);
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ns->ucounts = ucounts;
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ns->pid_allocated = PIDNS_ADDING;
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#if defined(CONFIG_SYSCTL) && defined(CONFIG_MEMFD_CREATE)
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ns->memfd_noexec_scope = pidns_memfd_noexec_scope(parent_pid_ns);
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#endif
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return ns;
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out_free_idr:
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idr_destroy(&ns->idr);
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kmem_cache_free(pid_ns_cachep, ns);
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out_dec:
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dec_pid_namespaces(ucounts);
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out:
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return ERR_PTR(err);
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}
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static void delayed_free_pidns(struct rcu_head *p)
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{
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struct pid_namespace *ns = container_of(p, struct pid_namespace, rcu);
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dec_pid_namespaces(ns->ucounts);
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put_user_ns(ns->user_ns);
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kmem_cache_free(pid_ns_cachep, ns);
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}
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static void destroy_pid_namespace(struct pid_namespace *ns)
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{
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ns_free_inum(&ns->ns);
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idr_destroy(&ns->idr);
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call_rcu(&ns->rcu, delayed_free_pidns);
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}
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struct pid_namespace *copy_pid_ns(unsigned long flags,
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struct user_namespace *user_ns, struct pid_namespace *old_ns)
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{
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if (!(flags & CLONE_NEWPID))
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return get_pid_ns(old_ns);
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if (task_active_pid_ns(current) != old_ns)
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return ERR_PTR(-EINVAL);
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return create_pid_namespace(user_ns, old_ns);
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}
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void put_pid_ns(struct pid_namespace *ns)
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{
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struct pid_namespace *parent;
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while (ns != &init_pid_ns) {
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parent = ns->parent;
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if (!refcount_dec_and_test(&ns->ns.count))
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break;
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destroy_pid_namespace(ns);
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ns = parent;
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}
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}
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EXPORT_SYMBOL_GPL(put_pid_ns);
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void zap_pid_ns_processes(struct pid_namespace *pid_ns)
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{
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int nr;
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int rc;
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struct task_struct *task, *me = current;
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int init_pids = thread_group_leader(me) ? 1 : 2;
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struct pid *pid;
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/* Don't allow any more processes into the pid namespace */
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disable_pid_allocation(pid_ns);
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/*
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* Ignore SIGCHLD causing any terminated children to autoreap.
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* This speeds up the namespace shutdown, plus see the comment
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* below.
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*/
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spin_lock_irq(&me->sighand->siglock);
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me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN;
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spin_unlock_irq(&me->sighand->siglock);
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/*
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* The last thread in the cgroup-init thread group is terminating.
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* Find remaining pid_ts in the namespace, signal and wait for them
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* to exit.
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*
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* Note: This signals each threads in the namespace - even those that
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* belong to the same thread group, To avoid this, we would have
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* to walk the entire tasklist looking a processes in this
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* namespace, but that could be unnecessarily expensive if the
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* pid namespace has just a few processes. Or we need to
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* maintain a tasklist for each pid namespace.
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*
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*/
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rcu_read_lock();
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read_lock(&tasklist_lock);
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nr = 2;
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idr_for_each_entry_continue(&pid_ns->idr, pid, nr) {
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task = pid_task(pid, PIDTYPE_PID);
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if (task && !__fatal_signal_pending(task))
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group_send_sig_info(SIGKILL, SEND_SIG_PRIV, task, PIDTYPE_MAX);
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}
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read_unlock(&tasklist_lock);
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rcu_read_unlock();
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/*
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* Reap the EXIT_ZOMBIE children we had before we ignored SIGCHLD.
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* kernel_wait4() will also block until our children traced from the
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* parent namespace are detached and become EXIT_DEAD.
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*/
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do {
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clear_thread_flag(TIF_SIGPENDING);
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rc = kernel_wait4(-1, NULL, __WALL, NULL);
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} while (rc != -ECHILD);
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/*
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* kernel_wait4() misses EXIT_DEAD children, and EXIT_ZOMBIE
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* process whose parents processes are outside of the pid
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* namespace. Such processes are created with setns()+fork().
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*
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* If those EXIT_ZOMBIE processes are not reaped by their
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* parents before their parents exit, they will be reparented
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* to pid_ns->child_reaper. Thus pidns->child_reaper needs to
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* stay valid until they all go away.
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*
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* The code relies on the pid_ns->child_reaper ignoring
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* SIGCHILD to cause those EXIT_ZOMBIE processes to be
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* autoreaped if reparented.
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*
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* Semantically it is also desirable to wait for EXIT_ZOMBIE
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* processes before allowing the child_reaper to be reaped, as
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* that gives the invariant that when the init process of a
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* pid namespace is reaped all of the processes in the pid
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* namespace are gone.
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*
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* Once all of the other tasks are gone from the pid_namespace
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* free_pid() will awaken this task.
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*/
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for (;;) {
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set_current_state(TASK_INTERRUPTIBLE);
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if (pid_ns->pid_allocated == init_pids)
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break;
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/*
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* Release tasks_rcu_exit_srcu to avoid following deadlock:
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*
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* 1) TASK A unshare(CLONE_NEWPID)
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* 2) TASK A fork() twice -> TASK B (child reaper for new ns)
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* and TASK C
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* 3) TASK B exits, kills TASK C, waits for TASK A to reap it
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* 4) TASK A calls synchronize_rcu_tasks()
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* -> synchronize_srcu(tasks_rcu_exit_srcu)
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* 5) *DEADLOCK*
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*
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* It is considered safe to release tasks_rcu_exit_srcu here
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* because we assume the current task can not be concurrently
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* reaped at this point.
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*/
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exit_tasks_rcu_stop();
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schedule();
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exit_tasks_rcu_start();
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}
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__set_current_state(TASK_RUNNING);
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if (pid_ns->reboot)
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current->signal->group_exit_code = pid_ns->reboot;
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acct_exit_ns(pid_ns);
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return;
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}
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#ifdef CONFIG_CHECKPOINT_RESTORE
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static int pid_ns_ctl_handler(struct ctl_table *table, int write,
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void *buffer, size_t *lenp, loff_t *ppos)
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{
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struct pid_namespace *pid_ns = task_active_pid_ns(current);
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struct ctl_table tmp = *table;
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int ret, next;
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if (write && !checkpoint_restore_ns_capable(pid_ns->user_ns))
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return -EPERM;
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next = idr_get_cursor(&pid_ns->idr) - 1;
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tmp.data = &next;
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ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
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if (!ret && write)
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idr_set_cursor(&pid_ns->idr, next + 1);
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return ret;
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}
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extern int pid_max;
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static struct ctl_table pid_ns_ctl_table[] = {
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{
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.procname = "ns_last_pid",
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.maxlen = sizeof(int),
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.mode = 0666, /* permissions are checked in the handler */
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.proc_handler = pid_ns_ctl_handler,
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.extra1 = SYSCTL_ZERO,
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.extra2 = &pid_max,
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},
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{ }
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};
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#endif /* CONFIG_CHECKPOINT_RESTORE */
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int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
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{
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if (pid_ns == &init_pid_ns)
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return 0;
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switch (cmd) {
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case LINUX_REBOOT_CMD_RESTART2:
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case LINUX_REBOOT_CMD_RESTART:
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pid_ns->reboot = SIGHUP;
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break;
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case LINUX_REBOOT_CMD_POWER_OFF:
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case LINUX_REBOOT_CMD_HALT:
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pid_ns->reboot = SIGINT;
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break;
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default:
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return -EINVAL;
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}
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read_lock(&tasklist_lock);
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send_sig(SIGKILL, pid_ns->child_reaper, 1);
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read_unlock(&tasklist_lock);
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do_exit(0);
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/* Not reached */
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return 0;
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}
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static inline struct pid_namespace *to_pid_ns(struct ns_common *ns)
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{
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return container_of(ns, struct pid_namespace, ns);
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}
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static struct ns_common *pidns_get(struct task_struct *task)
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{
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struct pid_namespace *ns;
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rcu_read_lock();
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ns = task_active_pid_ns(task);
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if (ns)
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get_pid_ns(ns);
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rcu_read_unlock();
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return ns ? &ns->ns : NULL;
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}
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static struct ns_common *pidns_for_children_get(struct task_struct *task)
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{
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struct pid_namespace *ns = NULL;
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task_lock(task);
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if (task->nsproxy) {
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ns = task->nsproxy->pid_ns_for_children;
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get_pid_ns(ns);
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}
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task_unlock(task);
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if (ns) {
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read_lock(&tasklist_lock);
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if (!ns->child_reaper) {
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put_pid_ns(ns);
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ns = NULL;
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}
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read_unlock(&tasklist_lock);
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}
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return ns ? &ns->ns : NULL;
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}
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static void pidns_put(struct ns_common *ns)
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{
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put_pid_ns(to_pid_ns(ns));
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}
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static int pidns_install(struct nsset *nsset, struct ns_common *ns)
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{
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struct nsproxy *nsproxy = nsset->nsproxy;
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struct pid_namespace *active = task_active_pid_ns(current);
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struct pid_namespace *ancestor, *new = to_pid_ns(ns);
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if (!ns_capable(new->user_ns, CAP_SYS_ADMIN) ||
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!ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN))
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return -EPERM;
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/*
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* Only allow entering the current active pid namespace
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* or a child of the current active pid namespace.
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*
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* This is required for fork to return a usable pid value and
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* this maintains the property that processes and their
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* children can not escape their current pid namespace.
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*/
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if (new->level < active->level)
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return -EINVAL;
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ancestor = new;
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while (ancestor->level > active->level)
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ancestor = ancestor->parent;
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if (ancestor != active)
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return -EINVAL;
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put_pid_ns(nsproxy->pid_ns_for_children);
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nsproxy->pid_ns_for_children = get_pid_ns(new);
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return 0;
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}
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static struct ns_common *pidns_get_parent(struct ns_common *ns)
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{
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struct pid_namespace *active = task_active_pid_ns(current);
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struct pid_namespace *pid_ns, *p;
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/* See if the parent is in the current namespace */
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pid_ns = p = to_pid_ns(ns)->parent;
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for (;;) {
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if (!p)
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return ERR_PTR(-EPERM);
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if (p == active)
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break;
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p = p->parent;
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}
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return &get_pid_ns(pid_ns)->ns;
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}
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static struct user_namespace *pidns_owner(struct ns_common *ns)
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{
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return to_pid_ns(ns)->user_ns;
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}
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const struct proc_ns_operations pidns_operations = {
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.name = "pid",
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.type = CLONE_NEWPID,
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.get = pidns_get,
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.put = pidns_put,
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.install = pidns_install,
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.owner = pidns_owner,
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.get_parent = pidns_get_parent,
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};
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const struct proc_ns_operations pidns_for_children_operations = {
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.name = "pid_for_children",
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.real_ns_name = "pid",
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.type = CLONE_NEWPID,
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.get = pidns_for_children_get,
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.put = pidns_put,
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.install = pidns_install,
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.owner = pidns_owner,
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.get_parent = pidns_get_parent,
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};
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static __init int pid_namespaces_init(void)
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{
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pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC | SLAB_ACCOUNT);
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#ifdef CONFIG_CHECKPOINT_RESTORE
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register_sysctl_init("kernel", pid_ns_ctl_table);
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#endif
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register_pid_ns_sysctl_table_vm();
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return 0;
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}
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__initcall(pid_namespaces_init);
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