memory_utils: adapt to new infrastructure

[mirror_lxc.git] / src / lxc / start.c

/* SPDX-License-Identifier: LGPL-2.1+ */

#ifndef _GNU_SOURCE
#define _GNU_SOURCE 1
#endif
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <grp.h>
#include <poll.h>
#include <pthread.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/file.h>
#include <sys/mount.h>
#include <sys/param.h>
#include <sys/prctl.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/un.h>
#include <sys/wait.h>
#include <unistd.h>

#include "af_unix.h"
#include "caps.h"
#include "cgroup.h"
#include "commands.h"
#include "commands_utils.h"
#include "conf.h"
#include "config.h"
#include "confile_utils.h"
#include "error.h"
#include "file_utils.h"
#include "list.h"
#include "log.h"
#include "lsm/lsm.h"
#include "lxccontainer.h"
#include "lxclock.h"
#include "lxcseccomp.h"
#include "macro.h"
#include "mainloop.h"
#include "memory_utils.h"
#include "monitor.h"
#include "namespace.h"
#include "network.h"
#include "raw_syscalls.h"
#include "start.h"
#include "storage/storage.h"
#include "storage/storage_utils.h"
#include "sync.h"
#include "syscall_wrappers.h"
#include "terminal.h"
#include "utils.h"

#if HAVE_LIBCAP
#include <sys/capability.h>
#endif

#ifndef HAVE_STRLCPY
#include "include/strlcpy.h"
#endif

lxc_log_define(start, lxc);

extern void mod_all_rdeps(struct lxc_container *c, bool inc);
static bool do_destroy_container(struct lxc_handler *handler);
static int lxc_rmdir_onedev_wrapper(void *data);
static void lxc_destroy_container_on_signal(struct lxc_handler *handler,
                                            const char *name);

static void print_top_failing_dir(const char *path)
{
        __do_free char *copy = NULL;
        int ret;
        char *e, *p, saved;

        copy = must_copy_string(path);
        p = copy;
        e = copy + strlen(path);

        while (p < e) {
                while (p < e && *p == '/')
                        p++;

                while (p < e && *p != '/')
                        p++;

                saved = *p;
                *p = '\0';

                ret = access(copy, X_OK);
                if (ret != 0) {
                        SYSERROR("Could not access %s. Please grant it x access, or add an ACL for the container " "root", copy);
                        return;
                }
                *p = saved;
        }
}

static void lxc_put_nsfds(struct lxc_handler *handler)
{
        for (int i = 0; i < LXC_NS_MAX; i++) {
                if (handler->nsfd[i] < 0)
                        continue;

                close_prot_errno_disarm(handler->nsfd[i]);
        }
}

static int lxc_try_preserve_ns(const int pid, const char *ns)
{
        int fd;

        fd = lxc_preserve_ns(pid, ns);
        if (fd < 0) {
                if (errno != ENOENT)
                        return log_error_errno(-EINVAL,
                                               errno, "Failed to preserve %s namespace",
                                               ns);

                return log_warn_errno(-EOPNOTSUPP,
                                      errno, "Kernel does not support preserving %s namespaces",
                                      ns);
        }

        return fd;
}

/* lxc_try_preserve_namespaces: open /proc/@pid/ns/@ns for each namespace
 * specified in ns_clone_flags.
 * Return true on success, false on failure.
 */
static bool lxc_try_preserve_namespaces(struct lxc_handler *handler,
                                        int ns_clone_flags, pid_t pid)
{
        int i;

        for (i = 0; i < LXC_NS_MAX; i++)
                handler->nsfd[i] = -EBADF;

        for (i = 0; i < LXC_NS_MAX; i++) {
                int fd;

                if ((ns_clone_flags & ns_info[i].clone_flag) == 0)
                        continue;

                fd = lxc_try_preserve_ns(pid, ns_info[i].proc_name);
                if (fd < 0) {
                        /* Do not fail to start container on kernels that do
                         * not support interacting with namespaces through
                         * /proc.
                         */
                        if (fd == -EOPNOTSUPP)
                                continue;

                        lxc_put_nsfds(handler);
                        return false;
                }

                handler->nsfd[i] = fd;
                DEBUG("Preserved %s namespace via fd %d", ns_info[i].proc_name,
                      handler->nsfd[i]);
        }

        return true;
}

static inline bool match_stdfds(int fd)
{
        return (fd == STDIN_FILENO || fd == STDOUT_FILENO || fd == STDERR_FILENO);
}

#ifdef HAVE_DLOG
static bool match_dlog_fds(struct dirent *direntp)
{
        char path[PATH_MAX] = {0};
        char link[PATH_MAX] = {0};
        ssize_t linklen;
        int ret;

        ret = snprintf(path, PATH_MAX, "/proc/self/fd/%s", direntp->d_name);
        if (ret < 0 || ret >= PATH_MAX)
                return log_error(false, "Failed to create file descriptor name");

        linklen = readlink(path, link, PATH_MAX);
        if (linklen < 0)
                return log_error(false, "Failed to read link path - \"%s\"", path);
        else if (linklen >= PATH_MAX)
                return log_error(false, "The name of link path is too long - \"%s\"", path);

        if (strcmp(link, "/dev/log_main")       == 0 ||
            strcmp(link, "/dev/log_system")     == 0 ||
            strcmp(link, "/dev/log_radio")      == 0)
                return true;

        return false;
}
#endif

int lxc_check_inherited(struct lxc_conf *conf, bool closeall,
                        int *fds_to_ignore, size_t len_fds)
{
        int fd, fddir;
        size_t i;
        DIR *dir;
        struct dirent *direntp;

        if (conf && conf->close_all_fds)
                closeall = true;

restart:
        dir = opendir("/proc/self/fd");
        if (!dir)
                return log_warn(-1, "Failed to open directory");

        fddir = dirfd(dir);

        while ((direntp = readdir(dir))) {
                int ret;
                struct lxc_list *cur;
                bool matched = false;

                if (strcmp(direntp->d_name, ".") == 0)
                        continue;

                if (strcmp(direntp->d_name, "..") == 0)
                        continue;

                ret = lxc_safe_int(direntp->d_name, &fd);
                if (ret < 0) {
                        INFO("Could not parse file descriptor for \"%s\"", direntp->d_name);
                        continue;
                }

                for (i = 0; i < len_fds; i++)
                        if (fds_to_ignore[i] == fd)
                                break;

                if (fd == fddir || fd == lxc_log_fd ||
                    (i < len_fds && fd == fds_to_ignore[i]))
                        continue;

                /* Keep state clients that wait on reboots. */
                if (conf) {
                        lxc_list_for_each(cur, &conf->state_clients) {
                                struct lxc_state_client *client = cur->elem;

                                if (client->clientfd != fd)
                                        continue;

                                matched = true;
                                break;
                        }
                }

                if (matched)
                        continue;

                if (current_config && fd == current_config->logfd)
                        continue;

                if (match_stdfds(fd))
                        continue;

#ifdef HAVE_DLOG
                if (match_dlog_fds(direntp))
                        continue;

#endif
                if (closeall) {
                        close(fd);
                        closedir(dir);
                        INFO("Closed inherited fd %d", fd);
                        goto restart;
                }
                WARN("Inherited fd %d", fd);
        }

        /* Only enable syslog at this point to avoid the above logging function
         * to open a new fd and make the check_inherited function enter an
         * infinite loop.
         */
        lxc_log_enable_syslog();

        closedir(dir); /* cannot fail */
        return 0;
}

static int setup_signal_fd(sigset_t *oldmask)
{
        int ret;
        sigset_t mask;
        const int signals[] = {SIGBUS, SIGILL, SIGSEGV, SIGWINCH};

        /* Block everything except serious error signals. */
        ret = sigfillset(&mask);
        if (ret < 0)
                return -EBADF;

        for (int sig = 0; sig < (sizeof(signals) / sizeof(signals[0])); sig++) {
                ret = sigdelset(&mask, signals[sig]);
                if (ret < 0)
                        return -EBADF;
        }

        ret = pthread_sigmask(SIG_BLOCK, &mask, oldmask);
        if (ret < 0)
                return log_error_errno(-EBADF, errno,
                                       "Failed to set signal mask");

        ret = signalfd(-1, &mask, SFD_CLOEXEC);
        if (ret < 0)
                return log_error_errno(-EBADF,
                                       errno, "Failed to create signal file descriptor");

        TRACE("Created signal file descriptor %d", ret);

        return ret;
}

static int signal_handler(int fd, uint32_t events, void *data,
                          struct lxc_epoll_descr *descr)
{
        int ret;
        siginfo_t info;
        struct signalfd_siginfo siginfo;
        struct lxc_handler *hdlr = data;

        ret = lxc_read_nointr(fd, &siginfo, sizeof(siginfo));
        if (ret < 0)
                return log_error(LXC_MAINLOOP_ERROR, "Failed to read signal info from signal file descriptor %d", fd);

        if (ret != sizeof(siginfo))
                return log_error(-EINVAL, "Unexpected size for struct signalfd_siginfo");

        /* Check whether init is running. */
        info.si_pid = 0;
        ret = waitid(P_PID, hdlr->pid, &info, WEXITED | WNOWAIT | WNOHANG);
        if (ret == 0 && info.si_pid == hdlr->pid)
                hdlr->init_died = true;

        /* Try to figure out a reasonable exit status to report. */
        if (hdlr->init_died) {
                switch (info.si_code) {
                case CLD_EXITED:
                        hdlr->exit_status = info.si_status << 8;
                        break;
                case CLD_KILLED:
                case CLD_DUMPED:
                case CLD_STOPPED:
                        hdlr->exit_status = info.si_status << 8 | 0x7f;
                        break;
                case CLD_CONTINUED:
                        /* Huh? The waitid() told us it's dead *and* continued? */
                        WARN("Init %d dead and continued?", hdlr->pid);
                        hdlr->exit_status = 1;
                        break;
                default:
                        ERROR("Unknown si_code: %d", info.si_code);
                        hdlr->exit_status = 1;
                }
        }

        if (siginfo.ssi_signo == SIGHUP) {
                if (hdlr->pidfd >= 0)
                        lxc_raw_pidfd_send_signal(hdlr->pidfd, SIGTERM, NULL, 0);
                else
                        kill(hdlr->pid, SIGTERM);
                INFO("Killing %d since terminal hung up", hdlr->pid);
                return hdlr->init_died ? LXC_MAINLOOP_CLOSE
                                       : LXC_MAINLOOP_CONTINUE;
        }

        if (siginfo.ssi_signo != SIGCHLD) {
                if (hdlr->pidfd >= 0)
                        lxc_raw_pidfd_send_signal(hdlr->pidfd,
                                                  siginfo.ssi_signo, NULL, 0);
                else
                        kill(hdlr->pid, siginfo.ssi_signo);
                INFO("Forwarded signal %d to pid %d", siginfo.ssi_signo, hdlr->pid);
                return hdlr->init_died ? LXC_MAINLOOP_CLOSE
                                       : LXC_MAINLOOP_CONTINUE;
        }

        /* More robustness, protect ourself from a SIGCHLD sent
         * by a process different from the container init.
         */
        if (siginfo.ssi_pid != hdlr->pid) {
                NOTICE("Received %d from pid %d instead of container init %d",
                       siginfo.ssi_signo, siginfo.ssi_pid, hdlr->pid);
                return hdlr->init_died ? LXC_MAINLOOP_CLOSE
                                       : LXC_MAINLOOP_CONTINUE;
        }

        if (siginfo.ssi_code == CLD_STOPPED) {
                INFO("Container init process was stopped");
                return hdlr->init_died ? LXC_MAINLOOP_CLOSE
                                       : LXC_MAINLOOP_CONTINUE;
        }

        if (siginfo.ssi_code == CLD_CONTINUED) {
                INFO("Container init process was continued");
                return hdlr->init_died ? LXC_MAINLOOP_CLOSE
                                       : LXC_MAINLOOP_CONTINUE;
        }

        return log_debug(LXC_MAINLOOP_CLOSE, "Container init process %d exited", hdlr->pid);
}

int lxc_serve_state_clients(const char *name, struct lxc_handler *handler,
                            lxc_state_t state)
{
        size_t retlen;
        ssize_t ret;
        struct lxc_list *cur, *next;
        struct lxc_msg msg = {.type = lxc_msg_state, .value = state};

        if (state == THAWED)
                handler->state = RUNNING;
        else
                handler->state = state;

        TRACE("Set container state to %s", lxc_state2str(state));

        if (lxc_list_empty(&handler->conf->state_clients))
                return log_trace(0, "No state clients registered");

        retlen = strlcpy(msg.name, name, sizeof(msg.name));
        if (retlen >= sizeof(msg.name))
                return -E2BIG;

        lxc_list_for_each_safe(cur, &handler->conf->state_clients, next) {
                struct lxc_state_client *client = cur->elem;

                if (client->states[state] == 0) {
                        TRACE("State %s not registered for state client %d",
                              lxc_state2str(state), client->clientfd);
                        continue;
                }

                TRACE("Sending state %s to state client %d",
                      lxc_state2str(state), client->clientfd);

                ret = lxc_send_nointr(client->clientfd, &msg, sizeof(msg), MSG_NOSIGNAL);
                if (ret <= 0)
                        SYSERROR("Failed to send message to client");

                /* kick client from list */
                lxc_list_del(cur);
                close(client->clientfd);
                free(cur->elem);
                free(cur);
        }

        return 0;
}

static int lxc_serve_state_socket_pair(const char *name,
                                       struct lxc_handler *handler,
                                       lxc_state_t state)
{
        ssize_t ret;

        if (!handler->daemonize ||
            handler->state_socket_pair[1] < 0 ||
            state == STARTING)
                return 0;

        /* Close read end of the socket pair. */
        close_prot_errno_disarm(handler->state_socket_pair[0]);

again:
        ret = lxc_abstract_unix_send_credential(handler->state_socket_pair[1],
                                                &(int){state}, sizeof(int));
        if (ret < 0) {
                SYSERROR("Failed to send state to %d", handler->state_socket_pair[1]);

                if (errno == EINTR)
                        goto again;

                return -1;
        }

        if (ret != sizeof(int))
                return log_error(-1, "Message too long : %d", handler->state_socket_pair[1]);

        TRACE("Sent container state \"%s\" to %d", lxc_state2str(state),
              handler->state_socket_pair[1]);

        /* Close write end of the socket pair. */
        close_prot_errno_disarm(handler->state_socket_pair[1]);

        return 0;
}

int lxc_set_state(const char *name, struct lxc_handler *handler,
                  lxc_state_t state)
{
        int ret;

        ret = lxc_serve_state_socket_pair(name, handler, state);
        if (ret < 0)
                return log_error(-1, "Failed to synchronize via anonymous pair of unix sockets");

        ret = lxc_serve_state_clients(name, handler, state);
        if (ret < 0)
                return -1;

        /* This function will try to connect to the legacy lxc-monitord state
         * server and only exists for backwards compatibility.
         */
        lxc_monitor_send_state(name, state, handler->lxcpath);

        return 0;
}

int lxc_poll(const char *name, struct lxc_handler *handler)
{
        int ret;
        bool has_console = true;
        struct lxc_epoll_descr descr, descr_console;

        if (handler->conf->console.path &&
            strcmp(handler->conf->console.path, "none") == 0)
                has_console = false;

        ret = lxc_mainloop_open(&descr);
        if (ret < 0) {
                ERROR("Failed to create mainloop");
                goto out_sigfd;
        }

        if (has_console) {
                ret = lxc_mainloop_open(&descr_console);
                if (ret < 0) {
                        ERROR("Failed to create console mainloop");
                        goto out_mainloop;
                }
        }

        ret = lxc_mainloop_add_handler(&descr, handler->sigfd, signal_handler, handler);
        if (ret < 0) {
                ERROR("Failed to add signal handler for %d to mainloop", handler->sigfd);
                goto out_mainloop_console;
        }

        ret = lxc_seccomp_setup_proxy(&handler->conf->seccomp, &descr, handler);
        if (ret < 0) {
                ERROR("Failed to setup seccomp proxy");
                goto out_mainloop_console;
        }

        if (has_console) {
                struct lxc_terminal *console = &handler->conf->console;

                ret = lxc_terminal_mainloop_add(&descr, console);
                if (ret < 0) {
                        ERROR("Failed to add console handlers to mainloop");
                        goto out_mainloop_console;
                }

                ret = lxc_terminal_mainloop_add(&descr_console, console);
                if (ret < 0) {
                        ERROR("Failed to add console handlers to console mainloop");
                        goto out_mainloop_console;
                }

                handler->conf->console.descr = &descr;
        }

        ret = lxc_cmd_mainloop_add(name, &descr, handler);
        if (ret < 0) {
                ERROR("Failed to add command handler to mainloop");
                goto out_mainloop_console;
        }

        TRACE("Mainloop is ready");

        ret = lxc_mainloop(&descr, -1);
        close_prot_errno_disarm(descr.epfd);
        if (ret < 0 || !handler->init_died)
                goto out_mainloop_console;

        if (has_console)
                ret = lxc_mainloop(&descr_console, 0);

out_mainloop_console:
        if (has_console) {
                lxc_mainloop_close(&descr_console);
                TRACE("Closed console mainloop");
        }

out_mainloop:
        lxc_mainloop_close(&descr);
        TRACE("Closed mainloop");

out_sigfd:
        TRACE("Closed signal file descriptor %d", handler->sigfd);
        close_prot_errno_disarm(handler->sigfd);

        return ret;
}

void lxc_zero_handler(struct lxc_handler *handler)
{
        memset(handler, 0, sizeof(struct lxc_handler));

        handler->state = STOPPED;

        handler->pinfd = -EBADF;

        handler->pidfd = -EBADF;

        handler->sigfd = -EBADF;

        for (int i = 0; i < LXC_NS_MAX; i++)
                handler->nsfd[i] = -EBADF;

        handler->data_sock[0] = -EBADF;
        handler->data_sock[1] = -EBADF;

        handler->state_socket_pair[0] = -EBADF;
        handler->state_socket_pair[1] = -EBADF;

        handler->sync_sock[0] = -EBADF;
        handler->sync_sock[1] = -EBADF;
}

void lxc_free_handler(struct lxc_handler *handler)
{
        close_prot_errno_disarm(handler->pinfd);
        close_prot_errno_disarm(handler->pidfd);
        close_prot_errno_disarm(handler->sigfd);
        lxc_put_nsfds(handler);
        if (handler->conf && handler->conf->reboot == REBOOT_NONE)
                close_prot_errno_disarm(handler->conf->maincmd_fd);
        close_prot_errno_disarm(handler->monitor_status_fd);
        close_prot_errno_disarm(handler->state_socket_pair[0]);
        close_prot_errno_disarm(handler->state_socket_pair[1]);
        cgroup_exit(handler->cgroup_ops);
        handler->conf = NULL;
        free_disarm(handler);
}

struct lxc_handler *lxc_init_handler(const char *name, struct lxc_conf *conf,
                                     const char *lxcpath, bool daemonize)
{
        int ret;
        struct lxc_handler *handler;

        handler = malloc(sizeof(*handler));
        if (!handler)
                return NULL;

        memset(handler, 0, sizeof(*handler));

        /* Note that am_guest_unpriv() checks the effective uid. We
         * probably don't care if we are real root only if we are running
         * as root so this should be fine.
         */
        handler->am_root = !am_guest_unpriv();
        handler->conf = conf;
        handler->lxcpath = lxcpath;
        handler->init_died = false;
        handler->data_sock[0] = -EBADF;
        handler->data_sock[1] = -EBADF;
        handler->monitor_status_fd = -EBADF;
        handler->pinfd = -EBADF;
        handler->pidfd = -EBADF;
        handler->sigfd = -EBADF;
        handler->state_socket_pair[0] = -EBADF;
        handler->state_socket_pair[1] = -EBADF;
        if (handler->conf->reboot == REBOOT_NONE)
                lxc_list_init(&handler->conf->state_clients);

        for (int i = 0; i < LXC_NS_MAX; i++)
                handler->nsfd[i] = -EBADF;

        handler->name = name;
        if (daemonize)
                handler->transient_pid = lxc_raw_getpid();
        else
                handler->transient_pid = -1;

        if (daemonize && handler->conf->reboot == REBOOT_NONE) {
                /* Create socketpair() to synchronize on daemonized startup.
                 * When the container reboots we don't need to synchronize
                 * again currently so don't open another socketpair().
                 */
                ret = socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0,
                                 handler->state_socket_pair);
                if (ret < 0) {
                        ERROR("Failed to create anonymous pair of unix sockets");
                        goto on_error;
                }

                TRACE("Created anonymous pair {%d,%d} of unix sockets",
                      handler->state_socket_pair[0],
                      handler->state_socket_pair[1]);
        }

        if (handler->conf->reboot == REBOOT_NONE) {
                handler->conf->maincmd_fd = lxc_cmd_init(name, lxcpath, "command");
                if (handler->conf->maincmd_fd < 0) {
                        ERROR("Failed to set up command socket");
                        goto on_error;
                }
        }

        TRACE("Unix domain socket %d for command server is ready",
              handler->conf->maincmd_fd);

        return handler;

on_error:
        lxc_free_handler(handler);

        return NULL;
}

int lxc_init(const char *name, struct lxc_handler *handler)
{
        __do_close_prot_errno int status_fd = -EBADF;
        int ret;
        const char *loglevel;
        struct lxc_conf *conf = handler->conf;

        handler->monitor_pid = lxc_raw_getpid();
        status_fd = open("/proc/self/status", O_RDONLY | O_CLOEXEC);
        if (status_fd < 0) {
                SYSERROR("Failed to open monitor status fd");
                goto out_close_maincmd_fd;
        }

        lsm_init();
        TRACE("Initialized LSM");

        ret = lxc_read_seccomp_config(conf);
        if (ret < 0) {
                ERROR("Failed loading seccomp policy");
                goto out_close_maincmd_fd;
        }
        TRACE("Read seccomp policy");

        /* Begin by setting the state to STARTING. */
        ret = lxc_set_state(name, handler, STARTING);
        if (ret < 0) {
                ERROR("Failed to set state to \"%s\"", lxc_state2str(STARTING));
                goto out_close_maincmd_fd;
        }
        TRACE("Set container state to \"STARTING\"");

        /* Start of environment variable setup for hooks. */
        ret = setenv("LXC_NAME", name, 1);
        if (ret < 0)
                SYSERROR("Failed to set environment variable: LXC_NAME=%s", name);

        if (conf->rcfile) {
                ret = setenv("LXC_CONFIG_FILE", conf->rcfile, 1);
                if (ret < 0)
                        SYSERROR("Failed to set environment variable: LXC_CONFIG_FILE=%s", conf->rcfile);
        }

        if (conf->rootfs.mount) {
                ret = setenv("LXC_ROOTFS_MOUNT", conf->rootfs.mount, 1);
                if (ret < 0)
                        SYSERROR("Failed to set environment variable: LXC_ROOTFS_MOUNT=%s", conf->rootfs.mount);
        }

        if (conf->rootfs.path) {
                ret = setenv("LXC_ROOTFS_PATH", conf->rootfs.path, 1);
                if (ret < 0)
                        SYSERROR("Failed to set environment variable: LXC_ROOTFS_PATH=%s", conf->rootfs.path);
        }

        if (conf->console.path) {
                ret = setenv("LXC_CONSOLE", conf->console.path, 1);
                if (ret < 0)
                        SYSERROR("Failed to set environment variable: LXC_CONSOLE=%s", conf->console.path);
        }

        if (conf->console.log_path) {
                ret = setenv("LXC_CONSOLE_LOGPATH", conf->console.log_path, 1);
                if (ret < 0)
                        SYSERROR("Failed to set environment variable: LXC_CONSOLE_LOGPATH=%s", conf->console.log_path);
        }

        if (cgns_supported()) {
                ret = setenv("LXC_CGNS_AWARE", "1", 1);
                if (ret < 0)
                        SYSERROR("Failed to set environment variable LXC_CGNS_AWARE=1");
        }

        loglevel = lxc_log_priority_to_string(lxc_log_get_level());
        ret = setenv("LXC_LOG_LEVEL", loglevel, 1);
        if (ret < 0)
                SYSERROR("Set environment variable LXC_LOG_LEVEL=%s", loglevel);

        if (conf->hooks_version == 0)
                ret = setenv("LXC_HOOK_VERSION", "0", 1);
        else
                ret = setenv("LXC_HOOK_VERSION", "1", 1);
        if (ret < 0)
                SYSERROR("Failed to set environment variable LXC_HOOK_VERSION=%u", conf->hooks_version);
        /* End of environment variable setup for hooks. */

        TRACE("Set environment variables");

        ret = run_lxc_hooks(name, "pre-start", conf, NULL);
        if (ret < 0) {
                ERROR("Failed to run lxc.hook.pre-start for container \"%s\"", name);
                goto out_aborting;
        }
        TRACE("Ran pre-start hooks");

        /* The signal fd has to be created before forking otherwise if the child
         * process exits before we setup the signal fd, the event will be lost
         * and the command will be stuck.
         */
        handler->sigfd = setup_signal_fd(&handler->oldmask);
        if (handler->sigfd < 0) {
                ERROR("Failed to setup SIGCHLD fd handler.");
                goto out_delete_tty;
        }
        TRACE("Set up signal fd");

        /* Do this after setting up signals since it might unblock SIGWINCH. */
        ret = lxc_terminal_setup(conf);
        if (ret < 0) {
                ERROR("Failed to create console");
                goto out_restore_sigmask;
        }
        TRACE("Created console");

        ret = lxc_terminal_map_ids(conf, &conf->console);
        if (ret < 0) {
                ERROR("Failed to chown console");
                goto out_delete_terminal;
        }
        TRACE("Chowned console");

        handler->cgroup_ops = cgroup_init(handler->conf);
        if (!handler->cgroup_ops) {
                ERROR("Failed to initialize cgroup driver");
                goto out_delete_terminal;
        }
        TRACE("Initialized cgroup driver");

        ret = lsm_process_prepare(conf, handler->lxcpath);
        if (ret < 0) {
                ERROR("Failed to initialize LSM");
                goto out_delete_terminal;
        }
        TRACE("Initialized LSM");

        INFO("Container \"%s\" is initialized", name);
        handler->monitor_status_fd = move_fd(status_fd);
        return 0;

out_delete_terminal:
        lxc_terminal_delete(&handler->conf->console);

out_restore_sigmask:
        (void)pthread_sigmask(SIG_SETMASK, &handler->oldmask, NULL);

out_delete_tty:
        lxc_delete_tty(&conf->ttys);

out_aborting:
        (void)lxc_set_state(name, handler, ABORTING);

out_close_maincmd_fd:
        close_prot_errno_disarm(conf->maincmd_fd);
        return -1;
}

void lxc_fini(const char *name, struct lxc_handler *handler)
{
        int ret;
        pid_t self;
        struct lxc_list *cur, *next;
        char *namespaces[LXC_NS_MAX + 1];
        size_t namespace_count = 0;
        struct cgroup_ops *cgroup_ops = handler->cgroup_ops;

        /* The STOPPING state is there for future cleanup code which can take
         * awhile.
         */
        lxc_set_state(name, handler, STOPPING);

        self = lxc_raw_getpid();
        for (int i = 0; i < LXC_NS_MAX; i++) {
                if (handler->nsfd[i] < 0)
                        continue;

                if (handler->conf->hooks_version == 0)
                        ret = asprintf(&namespaces[namespace_count],
                                      "%s:/proc/%d/fd/%d", ns_info[i].proc_name,
                                      self, handler->nsfd[i]);
                else
                        ret = asprintf(&namespaces[namespace_count],
                                      "/proc/%d/fd/%d", self, handler->nsfd[i]);
                if (ret < 0) {
                        SYSERROR("Failed to allocate memory");
                        break;
                }

                if (handler->conf->hooks_version == 0) {
                        namespace_count++;
                        continue;
                }

                ret = setenv(ns_info[i].env_name, namespaces[namespace_count], 1);
                if (ret < 0)
                        SYSERROR("Failed to set environment variable %s=%s",
                                 ns_info[i].env_name, namespaces[namespace_count]);
                else
                        TRACE("Set environment variable %s=%s",
                              ns_info[i].env_name, namespaces[namespace_count]);

                namespace_count++;
        }
        namespaces[namespace_count] = NULL;

        if (handler->conf->reboot > REBOOT_NONE) {
                ret = setenv("LXC_TARGET", "reboot", 1);
                if (ret < 0)
                        SYSERROR("Failed to set environment variable: LXC_TARGET=reboot");
        }

        if (handler->conf->reboot == REBOOT_NONE) {
                ret = setenv("LXC_TARGET", "stop", 1);
                if (ret < 0)
                        SYSERROR("Failed to set environment variable: LXC_TARGET=stop");
        }

        if (handler->conf->hooks_version == 0)
                ret = run_lxc_hooks(name, "stop", handler->conf, namespaces);
        else
                ret = run_lxc_hooks(name, "stop", handler->conf, NULL);
        if (ret < 0)
                ERROR("Failed to run \"lxc.hook.stop\" hook");

        while (namespace_count--)
                free(namespaces[namespace_count]);

        lsm_process_cleanup(handler->conf, handler->lxcpath);

        if (cgroup_ops) {
                cgroup_ops->payload_destroy(cgroup_ops, handler);
                cgroup_ops->monitor_destroy(cgroup_ops, handler);
        }

        if (handler->conf->reboot == REBOOT_NONE) {
                /* For all new state clients simply close the command socket.
                 * This will inform all state clients that the container is
                 * STOPPED and also prevents a race between a open()/close() on
                 * the command socket causing a new process to get ECONNREFUSED
                 * because we haven't yet closed the command socket.
                 */
                close_prot_errno_disarm(handler->conf->maincmd_fd);
                TRACE("Closed command socket");

                /* This function will try to connect to the legacy lxc-monitord
                 * state server and only exists for backwards compatibility.
                 */
                lxc_monitor_send_state(name, STOPPED, handler->lxcpath);

                /* The command socket is closed so no one can acces the command
                 * socket anymore so there's no need to lock it.
                 */
                handler->state = STOPPED;
                TRACE("Set container state to \"STOPPED\"");
        } else {
                lxc_set_state(name, handler, STOPPED);
        }

        /* Avoid lingering namespace references. */
        lxc_put_nsfds(handler);

        ret = run_lxc_hooks(name, "post-stop", handler->conf, NULL);
        if (ret < 0) {
                ERROR("Failed to run lxc.hook.post-stop for container \"%s\"", name);
                if (handler->conf->reboot > REBOOT_NONE) {
                        WARN("Container will be stopped instead of rebooted");
                        handler->conf->reboot = REBOOT_NONE;

                        ret = setenv("LXC_TARGET", "stop", 1);
                        if (ret < 0)
                                WARN("Failed to set environment variable: LXC_TARGET=stop");
                }
        }

        /* Reset mask set by setup_signal_fd. */
        ret = pthread_sigmask(SIG_SETMASK, &handler->oldmask, NULL);
        if (ret < 0)
                SYSWARN("Failed to restore signal mask");

        lxc_terminal_delete(&handler->conf->console);
        lxc_delete_tty(&handler->conf->ttys);

        /* The command socket is now closed, no more state clients can register
         * themselves from now on. So free the list of state clients.
         */
        lxc_list_for_each_safe(cur, &handler->conf->state_clients, next) {
                struct lxc_state_client *client = cur->elem;

                /* Keep state clients that want to be notified about reboots. */
                if ((handler->conf->reboot > REBOOT_NONE) &&
                    (client->states[RUNNING] == 2))
                        continue;

                /* close state client socket */
                lxc_list_del(cur);
                close(client->clientfd);
                free(cur->elem);
                free(cur);
        }

        if (handler->conf->ephemeral == 1 && handler->conf->reboot != REBOOT_REQ)
                lxc_destroy_container_on_signal(handler, name);

        lxc_free_handler(handler);
}

void lxc_abort(const char *name, struct lxc_handler *handler)
{
        int ret = 0;
        int status;

        lxc_set_state(name, handler, ABORTING);

        if (handler->pidfd >= 0) {
                ret = lxc_raw_pidfd_send_signal(handler->pidfd, SIGKILL, NULL, 0);
                if (ret)
                        SYSWARN("Failed to send SIGKILL via pidfd %d for process %d",
                                handler->pidfd, handler->pid);
        }

        if (!ret || errno != ESRCH)
                if (kill(handler->pid, SIGKILL))
                        SYSWARN("Failed to send SIGKILL to %d", handler->pid);

        do {
                ret = waitpid(-1, &status, 0);
        } while (ret > 0);
}

static int do_start(void *data)
{
        struct lxc_handler *handler = data;
        __lxc_unused __do_close_prot_errno int data_sock0 = handler->data_sock[0],
                                           data_sock1 = handler->data_sock[1];
        __do_close_prot_errno int status_fd = -EBADF;
        int ret;
        uid_t new_uid;
        gid_t new_gid;
        struct lxc_list *iterator;
        uid_t nsuid = 0;
        gid_t nsgid = 0;
        int devnull_fd = -1;

        lxc_sync_fini_parent(handler);

        if (lxc_abstract_unix_recv_fds(data_sock1, &status_fd, 1, NULL, 0) < 0) {
                ERROR("Failed to receive status file descriptor to child process");
                goto out_warn_father;
        }

        /* This prctl must be before the synchro, so if the parent dies before
         * we set the parent death signal, we will detect its death with the
         * synchro right after, otherwise we have a window where the parent can
         * exit before we set the pdeath signal leading to a unsupervized
         * container.
         */
        ret = lxc_set_death_signal(SIGKILL, handler->monitor_pid, status_fd);
        if (ret < 0) {
                SYSERROR("Failed to set PR_SET_PDEATHSIG to SIGKILL");
                goto out_warn_father;
        }

        ret = lxc_ambient_caps_up();
        if (ret < 0) {
                ERROR("Failed to raise ambient capabilities");
                goto out_warn_father;
        }

        ret = pthread_sigmask(SIG_SETMASK, &handler->oldmask, NULL);
        if (ret < 0) {
                SYSERROR("Failed to set signal mask");
                goto out_warn_father;
        }

        /* Don't leak the pinfd to the container. */
        close_prot_errno_disarm(handler->pinfd);

        ret = lxc_sync_wait_parent(handler, LXC_SYNC_STARTUP);
        if (ret < 0)
                goto out_warn_father;

        /* Unshare CLONE_NEWNET after CLONE_NEWUSER. See
         * https://github.com/lxc/lxd/issues/1978.
         */
        if ((handler->ns_clone_flags & (CLONE_NEWNET | CLONE_NEWUSER)) ==
            (CLONE_NEWNET | CLONE_NEWUSER)) {
                ret = unshare(CLONE_NEWNET);
                if (ret < 0) {
                        SYSERROR("Failed to unshare CLONE_NEWNET");
                        goto out_warn_father;
                }
                INFO("Unshared CLONE_NEWNET");
        }

        /* Tell the parent task it can begin to configure the container and wait
         * for it to finish.
         */
        ret = lxc_sync_barrier_parent(handler, LXC_SYNC_CONFIGURE);
        if (ret < 0)
                goto out_error;

        if (handler->ns_clone_flags & CLONE_NEWNET) {
                ret = lxc_network_recv_from_parent(handler);
                if (ret < 0) {
                        ERROR("Failed to receive veth names from parent");
                        goto out_warn_father;
                }
        }

        /* If we are in a new user namespace, become root there to have
         * privilege over our namespace.
         */
        if (!lxc_list_empty(&handler->conf->id_map)) {
                if (!handler->conf->root_nsuid_map)
                        nsuid = handler->conf->init_uid;

                if (!handler->conf->root_nsgid_map)
                        nsgid = handler->conf->init_gid;

                /* Drop groups only after we switched to a valid gid in the new
                 * user namespace.
                 */
                if (!lxc_setgroups(0, NULL) &&
                    (handler->am_root || errno != EPERM))
                        goto out_warn_father;

                if (!lxc_switch_uid_gid(nsuid, nsgid))
                        goto out_warn_father;

                ret = prctl(PR_SET_DUMPABLE, prctl_arg(1), prctl_arg(0),
                            prctl_arg(0), prctl_arg(0));
                if (ret < 0)
                        goto out_warn_father;

                /* set{g,u}id() clears deathsignal */
                ret = lxc_set_death_signal(SIGKILL, handler->monitor_pid, status_fd);
                if (ret < 0) {
                        SYSERROR("Failed to set PR_SET_PDEATHSIG to SIGKILL");
                        goto out_warn_father;
                }
        }

        ret = access(handler->lxcpath, X_OK);
        if (ret != 0) {
                print_top_failing_dir(handler->lxcpath);
                goto out_warn_father;
        }

        /* In order to checkpoint restore, we need to have everything in the
         * same mount namespace. However, some containers may not have a
         * reasonable /dev (in particular, they may not have /dev/null), so we
         * can't set init's std fds to /dev/null by opening it from inside the
         * container.
         *
         * If that's the case, fall back to using the host's /dev/null. This
         * means that migration won't work, but at least we won't spew output
         * where it isn't wanted.
         */
        if (handler->daemonize && !handler->conf->autodev) {
                char path[PATH_MAX];

                ret = snprintf(path, sizeof(path), "%s/dev/null",
                               handler->conf->rootfs.mount);
                if (ret < 0 || ret >= sizeof(path))
                        goto out_warn_father;

                ret = access(path, F_OK);
                if (ret != 0) {
                        devnull_fd = open_devnull();

                        if (devnull_fd < 0)
                                goto out_warn_father;
                        WARN("Using /dev/null from the host for container init's standard file descriptors. Migration will not work");
                }
        }

        /* Ask father to setup cgroups and wait for him to finish. */
        ret = lxc_sync_barrier_parent(handler, LXC_SYNC_CGROUP);
        if (ret < 0)
                goto out_error;

        /* Unshare cgroup namespace after we have setup our cgroups. If we do it
         * earlier we end up with a wrong view of /proc/self/cgroup. For
         * example, assume we unshare(CLONE_NEWCGROUP) first, and then create
         * the cgroup for the container, say /sys/fs/cgroup/cpuset/lxc/c, then
         * /proc/self/cgroup would show us:
         *
         *      8:cpuset:/lxc/c
         *
         * whereas it should actually show
         *
         *      8:cpuset:/
         */
        if (handler->ns_clone_flags & CLONE_NEWCGROUP) {
                ret = unshare(CLONE_NEWCGROUP);
                if (ret < 0) {
                        if (errno != EINVAL) {
                                SYSERROR("Failed to unshare CLONE_NEWCGROUP");
                                goto out_warn_father;
                        }

                        handler->ns_clone_flags &= ~CLONE_NEWCGROUP;
                        SYSINFO("Kernel does not support CLONE_NEWCGROUP");
                } else {
                        INFO("Unshared CLONE_NEWCGROUP");
                }
        }

        /* Add the requested environment variables to the current environment to
         * allow them to be used by the various hooks, such as the start hook
         * below.
         */
        lxc_list_for_each(iterator, &handler->conf->environment) {
                ret = putenv((char *)iterator->elem);
                if (ret < 0) {
                        SYSERROR("Failed to set environment variable: %s",
                                 (char *)iterator->elem);
                        goto out_warn_father;
                }
        }

        /* Setup the container, ip, names, utsname, ... */
        ret = lxc_setup(handler);
        if (ret < 0) {
                ERROR("Failed to setup container \"%s\"", handler->name);
                goto out_warn_father;
        }

        /* Set the label to change to when we exec(2) the container's init. */
        ret = lsm_process_label_set(NULL, handler->conf, true);
        if (ret < 0)
                goto out_warn_father;

        /* Set PR_SET_NO_NEW_PRIVS after we changed the lsm label. If we do it
         * before we aren't allowed anymore.
         */
        if (handler->conf->no_new_privs) {
                ret = prctl(PR_SET_NO_NEW_PRIVS, prctl_arg(1), prctl_arg(0),
                            prctl_arg(0), prctl_arg(0));
                if (ret < 0) {
                        SYSERROR("Could not set PR_SET_NO_NEW_PRIVS to block execve() gainable privileges");
                        goto out_warn_father;
                }
                DEBUG("Set PR_SET_NO_NEW_PRIVS to block execve() gainable privileges");
        }

        /* Some init's such as busybox will set sane tty settings on stdin,
         * stdout, stderr which it thinks is the console. We already set them
         * the way we wanted on the real terminal, and we want init to do its
         * setup on its console ie. the pty allocated in lxc_terminal_setup() so
         * make sure that that pty is stdin,stdout,stderr.
         */
         if (handler->conf->console.slave >= 0) {
                 if (handler->daemonize || !handler->conf->is_execute)
                         ret = set_stdfds(handler->conf->console.slave);
                 else
                         ret = lxc_terminal_set_stdfds(handler->conf->console.slave);
                 if (ret < 0) {
                        ERROR("Failed to redirect std{in,out,err} to pty file descriptor %d",
                              handler->conf->console.slave);
                        goto out_warn_father;
                 }
         }

        /* If we mounted a temporary proc, then unmount it now. */
        tmp_proc_unmount(handler->conf);

        ret = lxc_seccomp_load(handler->conf);
        if (ret < 0)
                goto out_warn_father;

        ret = lxc_seccomp_send_notifier_fd(&handler->conf->seccomp, data_sock0);
        if (ret < 0) {
                SYSERROR("Failed to send seccomp notify fd to parent");
                goto out_warn_father;
        }

        ret = run_lxc_hooks(handler->name, "start", handler->conf, NULL);
        if (ret < 0) {
                ERROR("Failed to run lxc.hook.start for container \"%s\"",
                      handler->name);
                goto out_warn_father;
        }

        close_prot_errno_disarm(handler->sigfd);

        if (handler->conf->console.slave < 0 && handler->daemonize) {
                if (devnull_fd < 0) {
                        devnull_fd = open_devnull();
                        if (devnull_fd < 0)
                                goto out_warn_father;
                }

                ret = set_stdfds(devnull_fd);
                if (ret < 0) {
                        ERROR("Failed to redirect std{in,out,err} to \"/dev/null\"");
                        goto out_warn_father;
                }
        }

        close_prot_errno_disarm(devnull_fd);

        setsid();

        if (handler->conf->init_cwd) {
                ret = chdir(handler->conf->init_cwd);
                if (ret < 0) {
                        SYSERROR("Could not change directory to \"%s\"",
                                 handler->conf->init_cwd);
                        goto out_warn_father;
                }
        }

        ret = lxc_sync_barrier_parent(handler, LXC_SYNC_CGROUP_LIMITS);
        if (ret < 0)
                goto out_warn_father;

        /* Reset the environment variables the user requested in a clear
         * environment.
         */
        ret = clearenv();
        /* Don't error out though. */
        if (ret < 0)
                SYSERROR("Failed to clear environment.");

        lxc_list_for_each(iterator, &handler->conf->environment) {
                ret = putenv((char *)iterator->elem);
                if (ret < 0) {
                        SYSERROR("Failed to set environment variable: %s",
                                 (char *)iterator->elem);
                        goto out_warn_father;
                }
        }

        ret = putenv("container=lxc");
        if (ret < 0) {
                SYSERROR("Failed to set environment variable: container=lxc");
                goto out_warn_father;
        }

        if (handler->conf->ttys.tty_names) {
                ret = putenv(handler->conf->ttys.tty_names);
                if (ret < 0) {
                        SYSERROR("Failed to set environment variable for container ptys");
                        goto out_warn_father;
                }
        }

        /* The container has been setup. We can now switch to an unprivileged
         * uid/gid.
         */
        new_uid = handler->conf->init_uid;
        new_gid = handler->conf->init_gid;

        /* Avoid unnecessary syscalls. */
        if (new_uid == nsuid)
                new_uid = LXC_INVALID_UID;

        if (new_gid == nsgid)
                new_gid = LXC_INVALID_GID;

        /* If we are in a new user namespace we already dropped all groups when
         * we switched to root in the new user namespace further above. Only
         * drop groups if we can, so ensure that we have necessary privilege.
         */
        if (lxc_list_empty(&handler->conf->id_map))
                #if HAVE_LIBCAP
                if (lxc_proc_cap_is_set(CAP_SETGID, CAP_EFFECTIVE))
                #endif
                        if (!lxc_setgroups(0, NULL))
                                goto out_warn_father;

        if (!lxc_switch_uid_gid(new_uid, new_gid))
                goto out_warn_father;

        ret = lxc_ambient_caps_down();
        if (ret < 0) {
                ERROR("Failed to clear ambient capabilities");
                goto out_warn_father;
        }

        if (handler->conf->monitor_signal_pdeath != SIGKILL) {
                ret = lxc_set_death_signal(handler->conf->monitor_signal_pdeath,
                                           handler->monitor_pid, status_fd);
                if (ret < 0) {
                        SYSERROR("Failed to set PR_SET_PDEATHSIG to %d",
                                 handler->conf->monitor_signal_pdeath);
                        goto out_warn_father;
                }
        }

        /* After this call, we are in error because this ops should not return
         * as it execs.
         */
        handler->ops->start(handler, handler->data);

out_warn_father:
        /* We want the parent to know something went wrong, so we return a
         * special error code.
         */
        lxc_sync_wake_parent(handler, LXC_SYNC_ERROR);

out_error:
        close_prot_errno_disarm(devnull_fd);

        return -1;
}

static int lxc_recv_ttys_from_child(struct lxc_handler *handler)
{
        int i;
        struct lxc_terminal_info *tty;
        int ret = -1;
        int sock = handler->data_sock[1];
        struct lxc_conf *conf = handler->conf;
        struct lxc_tty_info *ttys = &conf->ttys;

        if (!conf->ttys.max)
                return 0;

        ttys->tty = malloc(sizeof(*ttys->tty) * ttys->max);
        if (!ttys->tty)
                return -1;

        for (i = 0; i < conf->ttys.max; i++) {
                int ttyfds[2];

                ret = lxc_abstract_unix_recv_fds(sock, ttyfds, 2, NULL, 0);
                if (ret < 0)
                        break;

                tty = &ttys->tty[i];
                tty->busy = -1;
                tty->master = ttyfds[0];
                tty->slave = ttyfds[1];
                TRACE("Received pty with master fd %d and slave fd %d from child", tty->master, tty->slave);
        }

        if (ret < 0)
                SYSERROR("Failed to receive %zu ttys from child", ttys->max);
        else
                TRACE("Received %zu ttys from child", ttys->max);

        return ret;
}

int resolve_clone_flags(struct lxc_handler *handler)
{
        int i;
        struct lxc_conf *conf = handler->conf;

        for (i = 0; i < LXC_NS_MAX; i++) {
                if (conf->ns_keep) {
                        if (!(conf->ns_keep & ns_info[i].clone_flag))
                                handler->ns_clone_flags |= ns_info[i].clone_flag;
                } else if (conf->ns_clone) {
                        if ((conf->ns_clone & ns_info[i].clone_flag))
                                handler->ns_clone_flags |= ns_info[i].clone_flag;
                } else {
                        if (i == LXC_NS_USER && lxc_list_empty(&handler->conf->id_map))
                                continue;

                        if (i == LXC_NS_NET && lxc_requests_empty_network(handler))
                                continue;

                        if (i == LXC_NS_CGROUP && !cgns_supported())
                                continue;

                        handler->ns_clone_flags |= ns_info[i].clone_flag;
                }

                if (!conf->ns_share[i])
                        continue;

                handler->ns_clone_flags &= ~ns_info[i].clone_flag;
                TRACE("Sharing %s namespace", ns_info[i].proc_name);
        }

        return 0;
}

/* Note that this function is used with clone(CLONE_VM). Some glibc versions
 * used to reset the pid/tid to -1 when CLONE_VM was used without CLONE_THREAD.
 * But since the memory between parent and child is shared on CLONE_VM this
 * would invalidate the getpid() cache that glibc used to maintain and so
 * getpid() in the child would return the parent's pid. This is all fixed in
 * newer glibc versions where the getpid() cache is removed and the pid/tid is
 * not reset anymore.
 * However, if for whatever reason you - dear committer - somehow need to get the
 * pid of the dummy intermediate process for do_share_ns() you need to call
 * lxc_raw_getpid(). The next lxc_raw_clone() call does not employ CLONE_VM and
 * will be fine.
 */
static inline int do_share_ns(void *arg)
{
        int i, flags, ret;
        struct lxc_handler *handler = arg;

        for (i = 0; i < LXC_NS_MAX; i++) {
                if (handler->nsfd[i] < 0)
                        continue;

                ret = setns(handler->nsfd[i], 0);
                if (ret < 0) {
                        /*
                         * Note that joining a user and/or mount namespace
                         * requires the process is not multithreaded otherwise
                         * setns() will fail here.
                         */
                        SYSERROR("Failed to inherit %s namespace",
                                 ns_info[i].proc_name);
                        return -1;
                }

                DEBUG("Inherited %s namespace", ns_info[i].proc_name);
        }

        flags = handler->ns_on_clone_flags;
        flags |= CLONE_PARENT;
        handler->pid = lxc_raw_clone_cb(do_start, handler, CLONE_PIDFD | flags,
                                        &handler->pidfd);
        if (handler->pid < 0)
                return -1;

        return 0;
}

/* lxc_spawn() performs crucial setup tasks and clone()s the new process which
 * exec()s the requested container binary.
 * Note that lxc_spawn() runs in the parent namespaces. Any operations performed
 * right here should be double checked if they'd pose a security risk. (For
 * example, any {u}mount() operations performed here will be reflected on the
 * host!)
 */
static int lxc_spawn(struct lxc_handler *handler)
{
        __do_close_prot_errno int data_sock0 = -EBADF, data_sock1 = -EBADF;
        int i, ret;
        char pidstr[20];
        bool wants_to_map_ids;
        struct lxc_list *id_map;
        const char *name = handler->name;
        const char *lxcpath = handler->lxcpath;
        bool share_ns = false;
        struct lxc_conf *conf = handler->conf;
        struct cgroup_ops *cgroup_ops = handler->cgroup_ops;

        id_map = &conf->id_map;
        wants_to_map_ids = !lxc_list_empty(id_map);

        for (i = 0; i < LXC_NS_MAX; i++) {
                if (!conf->ns_share[i])
                        continue;

                handler->nsfd[i] = lxc_inherit_namespace(conf->ns_share[i], lxcpath, ns_info[i].proc_name);
                if (handler->nsfd[i] < 0)
                        return -1;

                share_ns = true;
        }

        ret = lxc_sync_init(handler);
        if (ret < 0)
                return -1;

        ret = socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0,
                         handler->data_sock);
        if (ret < 0)
                goto out_sync_fini;
        data_sock0 = handler->data_sock[0];
        data_sock1 = handler->data_sock[1];

        ret = resolve_clone_flags(handler);
        if (ret < 0)
                goto out_sync_fini;

        if (handler->ns_clone_flags & CLONE_NEWNET) {
                ret = lxc_find_gateway_addresses(handler);
                if (ret) {
                        ERROR("Failed to find gateway addresses");
                        goto out_sync_fini;
                }
        }

        if (!cgroup_ops->payload_create(cgroup_ops, handler)) {
                ERROR("Failed creating cgroups");
                goto out_delete_net;
        }

        /* If the rootfs is not a blockdev, prevent the container from marking
         * it readonly.
         * If the container is unprivileged then skip rootfs pinning.
         */
        if (!wants_to_map_ids) {
                handler->pinfd = pin_rootfs(conf->rootfs.path);
                if (handler->pinfd == -EBADF)
                        INFO("Failed to pin the rootfs for container \"%s\"", handler->name);
        }

        /* Create a process in a new set of namespaces. */
        handler->ns_on_clone_flags = handler->ns_clone_flags;
        if (handler->ns_clone_flags & CLONE_NEWUSER) {
                /* If CLONE_NEWUSER and CLONE_NEWNET was requested, we need to
                 * clone a new user namespace first and only later unshare our
                 * network namespace to ensure that network devices ownership is
                 * set up correctly.
                 */
                handler->ns_on_clone_flags &= ~CLONE_NEWNET;
        }
        /* The cgroup namespace gets unshare()ed not clone()ed. */
        handler->ns_on_clone_flags &= ~CLONE_NEWCGROUP;

        if (share_ns) {
                pid_t attacher_pid;

                attacher_pid = lxc_clone(do_share_ns, handler,
                                         CLONE_VFORK | CLONE_VM | CLONE_FILES, NULL);
                if (attacher_pid < 0) {
                        SYSERROR(LXC_CLONE_ERROR);
                        goto out_delete_net;
                }

                ret = wait_for_pid(attacher_pid);
                if (ret < 0) {
                        SYSERROR("Intermediate process failed");
                        goto out_delete_net;
                }
        } else {
                handler->pid = lxc_raw_clone_cb(do_start, handler,
                                                CLONE_PIDFD | handler->ns_on_clone_flags,
                                                &handler->pidfd);
        }
        if (handler->pid < 0) {
                SYSERROR(LXC_CLONE_ERROR);
                goto out_delete_net;
        }
        TRACE("Cloned child process %d", handler->pid);

        /* Verify that we can actually make use of pidfds. */
        if (!lxc_can_use_pidfd(handler->pidfd))
                close_prot_errno_disarm(handler->pidfd);

        ret = snprintf(pidstr, 20, "%d", handler->pid);
        if (ret < 0 || ret >= 20)
                goto out_delete_net;

        ret = setenv("LXC_PID", pidstr, 1);
        if (ret < 0)
                SYSERROR("Failed to set environment variable: LXC_PID=%s", pidstr);

        for (i = 0; i < LXC_NS_MAX; i++)
                if (handler->ns_on_clone_flags & ns_info[i].clone_flag)
                        INFO("Cloned %s", ns_info[i].flag_name);

        if (!lxc_try_preserve_namespaces(handler, handler->ns_on_clone_flags, handler->pid)) {
                ERROR("Failed to preserve cloned namespaces for lxc.hook.stop");
                goto out_delete_net;
        }

        lxc_sync_fini_child(handler);

        if (lxc_abstract_unix_send_fds(handler->data_sock[0], &handler->monitor_status_fd, 1, NULL, 0) < 0) {
                ERROR("Failed to send status file descriptor to child process");
                goto out_delete_net;
        }
        close_prot_errno_disarm(handler->monitor_status_fd);

        /* Map the container uids. The container became an invalid userid the
         * moment it was cloned with CLONE_NEWUSER. This call doesn't change
         * anything immediately, but allows the container to setuid(0) (0 being
         * mapped to something else on the host.) later to become a valid uid
         * again.
         */
        if (wants_to_map_ids) {
                if (!handler->conf->ns_share[LXC_NS_USER] &&
                    (handler->conf->ns_keep & CLONE_NEWUSER) == 0) {
                        ret = lxc_map_ids(id_map, handler->pid);
                        if (ret < 0) {
                                ERROR("Failed to set up id mapping.");
                                goto out_delete_net;
                        }
                }
        }

        ret = lxc_sync_wake_child(handler, LXC_SYNC_STARTUP);
        if (ret < 0)
                goto out_delete_net;

        ret = lxc_sync_wait_child(handler, LXC_SYNC_CONFIGURE);
        if (ret < 0)
                goto out_delete_net;

        if (!cgroup_ops->setup_limits_legacy(cgroup_ops, handler->conf, false)) {
                ERROR("Failed to setup cgroup limits for container \"%s\"", name);
                goto out_delete_net;
        }

        if (!cgroup_ops->payload_enter(cgroup_ops, handler)) {
                goto out_delete_net;
        }

        if (!cgroup_ops->payload_delegate_controllers(cgroup_ops)) {
                ERROR("Failed to delegate controllers to payload cgroup");
                goto out_delete_net;
        }

        if (!cgroup_ops->setup_limits(cgroup_ops, handler)) {
                ERROR("Failed to setup cgroup limits for container \"%s\"", name);
                goto out_delete_net;
        }

        if (!cgroup_ops->chown(cgroup_ops, handler->conf))
                goto out_delete_net;

        /* If not done yet, we're now ready to preserve the network namespace */
        if (handler->nsfd[LXC_NS_NET] < 0) {
                ret = lxc_try_preserve_ns(handler->pid, "net");
                if (ret < 0) {
                        if (ret != -EOPNOTSUPP) {
                                SYSERROR("Failed to preserve net namespace");
                                goto out_delete_net;
                        }
                } else {
                        handler->nsfd[LXC_NS_NET] = ret;
                        DEBUG("Preserved net namespace via fd %d", ret);
                }
        }
        ret = lxc_netns_set_nsid(handler->nsfd[LXC_NS_NET]);
        if (ret < 0)
                SYSWARN("Failed to allocate new network namespace id");
        else
                TRACE("Allocated new network namespace id");

        /* Create the network configuration. */
        if (handler->ns_clone_flags & CLONE_NEWNET) {
                ret = lxc_create_network(handler);
                if (ret < 0) {
                        ERROR("Failed to create the network");
                        goto out_delete_net;
                }

                ret = lxc_network_send_to_child(handler);
                if (ret < 0) {
                        ERROR("Failed to send veth names to child");
                        goto out_delete_net;
                }
        }

        if (!lxc_list_empty(&conf->procs)) {
                ret = setup_proc_filesystem(&conf->procs, handler->pid);
                if (ret < 0)
                        goto out_delete_net;
        }

        /* Tell the child to continue its initialization. We'll get
         * LXC_SYNC_CGROUP when it is ready for us to setup cgroups.
         */
        ret = lxc_sync_barrier_child(handler, LXC_SYNC_POST_CONFIGURE);
        if (ret < 0)
                goto out_delete_net;

        if (!lxc_list_empty(&conf->limits)) {
                ret = setup_resource_limits(&conf->limits, handler->pid);
                if (ret < 0) {
                        ERROR("Failed to setup resource limits");
                        goto out_delete_net;
                }
        }

        ret = lxc_sync_barrier_child(handler, LXC_SYNC_CGROUP_UNSHARE);
        if (ret < 0)
                goto out_delete_net;

        if (!cgroup_ops->setup_limits_legacy(cgroup_ops, handler->conf, true)) {
                ERROR("Failed to setup legacy device cgroup controller limits");
                goto out_delete_net;
        }
        TRACE("Set up legacy device cgroup controller limits");

        if (!cgroup_ops->devices_activate(cgroup_ops, handler)) {
                ERROR("Failed to setup cgroup2 device controller limits");
                goto out_delete_net;
        }
        TRACE("Set up cgroup2 device controller limits");

        if (handler->ns_clone_flags & CLONE_NEWCGROUP) {
                /* Now we're ready to preserve the cgroup namespace */
                ret = lxc_try_preserve_ns(handler->pid, "cgroup");
                if (ret < 0) {
                        if (ret != -EOPNOTSUPP) {
                                SYSERROR("Failed to preserve cgroup namespace");
                                goto out_delete_net;
                        }
                } else {
                        handler->nsfd[LXC_NS_CGROUP] = ret;
                        DEBUG("Preserved cgroup namespace via fd %d", ret);
                }
        }

        cgroup_ops->payload_finalize(cgroup_ops);
        TRACE("Finished setting up cgroups");

        /* Run any host-side start hooks */
        ret = run_lxc_hooks(name, "start-host", conf, NULL);
        if (ret < 0) {
                ERROR("Failed to run lxc.hook.start-host");
                goto out_delete_net;
        }

        /* Tell the child to complete its initialization and wait for it to exec
         * or return an error. (The child will never return
         * LXC_SYNC_READY_START+1. It will either close the sync pipe, causing
         * lxc_sync_barrier_child to return success, or return a different
         * value, causing us to error out).
         */
        ret = lxc_sync_barrier_child(handler, LXC_SYNC_READY_START);
        if (ret < 0)
                goto out_delete_net;

        if (handler->ns_clone_flags & CLONE_NEWNET) {
                ret = lxc_network_recv_name_and_ifindex_from_child(handler);
                if (ret < 0) {
                        ERROR("Failed to receive names and ifindices for network devices from child");
                        goto out_delete_net;
                }
        }

        /* Now all networks are created, network devices are moved into place,
         * and the correct names and ifindices in the respective namespaces have
         * been recorded. The corresponding structs have now all been filled. So
         * log them for debugging purposes.
         */
        lxc_log_configured_netdevs(conf);

        /* Read tty fds allocated by child. */
        ret = lxc_recv_ttys_from_child(handler);
        if (ret < 0) {
                ERROR("Failed to receive tty info from child process");
                goto out_delete_net;
        }

        ret = lxc_seccomp_recv_notifier_fd(&handler->conf->seccomp, data_sock1);
        if (ret < 0) {
                SYSERROR("Failed to receive seccomp notify fd from child");
                goto out_delete_net;
        }

        ret = handler->ops->post_start(handler, handler->data);
        if (ret < 0)
                goto out_abort;

        ret = lxc_set_state(name, handler, RUNNING);
        if (ret < 0) {
                ERROR("Failed to set state to \"%s\"", lxc_state2str(RUNNING));
                goto out_abort;
        }

        lxc_sync_fini(handler);

        return 0;

out_delete_net:
        if (handler->ns_clone_flags & CLONE_NEWNET)
                lxc_delete_network(handler);

out_abort:
        lxc_abort(name, handler);

out_sync_fini:
        lxc_sync_fini(handler);
        close_prot_errno_disarm(handler->pinfd);

        return -1;
}

int __lxc_start(const char *name, struct lxc_handler *handler,
                struct lxc_operations* ops, void *data, const char *lxcpath,
                bool daemonize, int *error_num)
{
        int ret, status;
        struct lxc_conf *conf = handler->conf;
        struct cgroup_ops *cgroup_ops;

        ret = lxc_init(name, handler);
        if (ret < 0) {
                ERROR("Failed to initialize container \"%s\"", name);
                goto out_fini_nonet;
        }
        handler->ops = ops;
        handler->data = data;
        handler->daemonize = daemonize;
        cgroup_ops = handler->cgroup_ops;

        if (!attach_block_device(handler->conf)) {
                ERROR("Failed to attach block device");
                ret = -1;
                goto out_fini_nonet;
        }

        if (!cgroup_ops->monitor_create(cgroup_ops, handler)) {
                ERROR("Failed to create monitor cgroup");
                ret = -1;
                goto out_fini_nonet;
        }

        if (!cgroup_ops->monitor_enter(cgroup_ops, handler)) {
                ERROR("Failed to enter monitor cgroup");
                ret = -1;
                goto out_fini_nonet;
        }

        if (!cgroup_ops->monitor_delegate_controllers(cgroup_ops)) {
                ERROR("Failed to delegate controllers to monitor cgroup");
                ret = -1;
                goto out_fini_nonet;
        }

        if (geteuid() == 0 && !lxc_list_empty(&conf->id_map)) {
                /* If the backing store is a device, mount it here and now. */
                if (rootfs_is_blockdev(conf)) {
                        ret = unshare(CLONE_NEWNS);
                        if (ret < 0) {
                                ERROR("Failed to unshare CLONE_NEWNS");
                                goto out_fini_nonet;
                        }
                        INFO("Unshared CLONE_NEWNS");

                        remount_all_slave();
                        ret = lxc_setup_rootfs_prepare_root(conf, name, lxcpath);
                        if (ret < 0) {
                                ERROR("Error setting up rootfs mount as root before spawn");
                                goto out_fini_nonet;
                        }
                        INFO("Set up container rootfs as host root");
                }
        }

        ret = lxc_spawn(handler);
        if (ret < 0) {
                ERROR("Failed to spawn container \"%s\"", name);
                goto out_detach_blockdev;
        }

        handler->conf->reboot = REBOOT_NONE;

        ret = lxc_poll(name, handler);
        if (ret) {
                ERROR("LXC mainloop exited with error: %d", ret);
                goto out_abort;
        }

        if (!handler->init_died && handler->pid > 0) {
                ERROR("Child process is not killed");
                ret = -1;
                goto out_abort;
        }

        status = lxc_wait_for_pid_status(handler->pid);
        if (status < 0)
                SYSERROR("Failed to retrieve status for %d", handler->pid);

        /* If the child process exited but was not signaled, it didn't call
         * reboot. This should mean it was an lxc-execute which simply exited.
         * In any case, treat it as a 'halt'.
         */
        if (WIFSIGNALED(status)) {
                switch(WTERMSIG(status)) {
                case SIGINT: /* halt */
                        DEBUG("Container \"%s\" is halting", name);
                        break;
                case SIGHUP: /* reboot */
                        DEBUG("Container \"%s\" is rebooting", name);
                        handler->conf->reboot = REBOOT_REQ;
                        break;
                case SIGSYS: /* seccomp */
                        DEBUG("Container \"%s\" violated its seccomp policy", name);
                        break;
                default:
                        DEBUG("Unknown exit status for container \"%s\" init %d", name, WTERMSIG(status));
                        break;
                }
        }

        ret = lxc_restore_phys_nics_to_netns(handler);
        if (ret < 0)
                ERROR("Failed to move physical network devices back to parent network namespace");

        close_prot_errno_disarm(handler->pinfd);

        lxc_monitor_send_exit_code(name, status, handler->lxcpath);
        lxc_error_set_and_log(handler->pid, status);
        if (error_num)
                *error_num = handler->exit_status;

out_fini:
        lxc_delete_network(handler);

out_detach_blockdev:
        detach_block_device(handler->conf);

out_fini_nonet:
        lxc_fini(name, handler);
        return ret;

out_abort:
        lxc_abort(name, handler);
        goto out_fini;
}

struct start_args {
        char *const *argv;
};

static int start(struct lxc_handler *handler, void* data)
{
        struct start_args *arg = data;

        NOTICE("Exec'ing \"%s\"", arg->argv[0]);

        execvp(arg->argv[0], arg->argv);
        SYSERROR("Failed to exec \"%s\"", arg->argv[0]);
        return 0;
}

static int post_start(struct lxc_handler *handler, void* data)
{
        struct start_args *arg = data;

        NOTICE("Started \"%s\" with pid \"%d\"", arg->argv[0], handler->pid);
        return 0;
}

static struct lxc_operations start_ops = {
        .start = start,
        .post_start = post_start
};

int lxc_start(const char *name, char *const argv[], struct lxc_handler *handler,
              const char *lxcpath, bool daemonize, int *error_num)
{
        struct start_args start_arg = {
                .argv = argv,
        };

        TRACE("Doing lxc_start");
        return __lxc_start(name, handler, &start_ops, &start_arg, lxcpath, daemonize, error_num);
}

static void lxc_destroy_container_on_signal(struct lxc_handler *handler,
                                            const char *name)
{
        char destroy[PATH_MAX];
        struct lxc_container *c;
        int ret = 0;
        bool bret = true;

        if (handler->conf->rootfs.path && handler->conf->rootfs.mount) {
                bret = do_destroy_container(handler);
                if (!bret) {
                        ERROR("Error destroying rootfs for container \"%s\"", name);
                        return;
                }
        }
        INFO("Destroyed rootfs for container \"%s\"", name);

        ret = snprintf(destroy, PATH_MAX, "%s/%s", handler->lxcpath, name);
        if (ret < 0 || ret >= PATH_MAX) {
                ERROR("Error destroying directory for container \"%s\"", name);
                return;
        }

        c = lxc_container_new(name, handler->lxcpath);
        if (c) {
                if (container_disk_lock(c)) {
                        INFO("Could not update lxc_snapshots file");
                        lxc_container_put(c);
                } else {
                        mod_all_rdeps(c, false);
                        container_disk_unlock(c);
                        lxc_container_put(c);
                }
        }

        if (!handler->am_root)
                ret = userns_exec_full(handler->conf, lxc_rmdir_onedev_wrapper,
                                       destroy, "lxc_rmdir_onedev_wrapper");
        else
                ret = lxc_rmdir_onedev(destroy, NULL);

        if (ret < 0) {
                ERROR("Error destroying directory for container \"%s\"", name);
                return;
        }
        INFO("Destroyed directory for container \"%s\"", name);
}

static int lxc_rmdir_onedev_wrapper(void *data)
{
        char *arg = (char *) data;
        return lxc_rmdir_onedev(arg, NULL);
}

static bool do_destroy_container(struct lxc_handler *handler)
{
        int ret;

        if (!handler->am_root) {
                ret = userns_exec_full(handler->conf, storage_destroy_wrapper,
                                       handler->conf, "storage_destroy_wrapper");
                if (ret < 0)
                        return false;

                return true;
        }

        return storage_destroy(handler->conf);
}