Merge pull request #3918 from brauner/2021-07-30.devpts

[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 "cgroups/cgroup.h"
#include "cgroups/cgroup_utils.h"
#include "commands.h"
#include "commands_utils.h"
#include "compiler.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 "process_utils.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_namespace(struct lxc_handler *handler,
                                      lxc_namespace_t idx, const char *ns)
{
        __do_close int fd = -EBADF;
        int ret;

        fd = lxc_preserve_ns(handler->pid, ns);
        if (fd < 0)
                return -errno;

        ret = strnprintf(handler->nsfd_paths[idx],
                         sizeof(handler->nsfd_paths[idx]), "%s:/proc/%d/fd/%d",
                         ns_info[idx].proc_name, handler->monitor_pid, fd);
        if (ret < 0)
                return ret_errno(EIO);

        /*
         * In case LXC is configured for exposing information to hooks as
         * argv-style arguments prepare an argv array we can use.
         */
        handler->hook_argv[handler->hook_argc] = handler->nsfd_paths[idx];
        handler->hook_argc++;

        DEBUG("Preserved %s namespace via fd %d and stashed path as %s",
              ns_info[idx].proc_name, fd, handler->nsfd_paths[idx]);

        handler->nsfd[idx] = move_fd(fd);
        return 0;
}

/* 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)
{
        for (lxc_namespace_t ns_idx = 0; ns_idx < LXC_NS_MAX; ns_idx++)
                handler->nsfd[ns_idx] = -EBADF;

        for (lxc_namespace_t ns_idx = 0; ns_idx < LXC_NS_MAX; ns_idx++) {
                int ret;
                const char *ns = ns_info[ns_idx].proc_name;

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

                ret = lxc_try_preserve_namespace(handler, ns_idx,
                                                 ns_info[ns_idx].proc_name);
                if (ret < 0) {
                        if (ret == -ENOENT) {
                                SYSERROR("Kernel does not support preserving %s namespaces", ns);
                                continue;
                        }

                        /*
                         * Handle kernels that do not support interacting with
                         * namespaces through procfs.
                         */
                        lxc_put_nsfds(handler);
                        return log_error_errno(false, errno, "Failed to preserve %s namespace", ns);
                }
        }

        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 = strnprintf(path, sizeof(path), "/proc/self/fd/%s", direntp->d_name);
        if (ret < 0)
                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 (strequal(link, "/dev/log_main") ||
            strequal(link, "/dev/log_system") ||
            strequal(link, "/dev/log_radio"))
                return true;

        return false;
}
#endif

/* Parses the LISTEN_FDS environment variable value.
 * The returned value is the highest fd number up to which the
 * file descriptors must be passed to the container process.
 *
 * For example, if LISTEN_FDS=2 then 4 is returned and file descriptors 3 and 4
 * MUST be passed to the container process (in addition to the standard streams)
 * to support [socket activation][systemd-listen-fds].
 */
static unsigned int get_listen_fds_max(void)
{
        int ret;
        unsigned int num_fds;
        const char *val;

        val = getenv("LISTEN_FDS");
        if (!val)
                return 0;

        ret = lxc_safe_uint(val, &num_fds);
        if (ret < 0)
                return syserror_ret(0, "Failed to parse \"LISTEN_FDS=%s\" environment variable", val);

        return log_trace(num_fds, "Parsed \"LISTEN_FDS=%s\" environment variable", val);
}

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;
        unsigned int listen_fds_max;

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

        listen_fds_max = get_listen_fds_max();

        /*
         * Disable 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_syslog_disable();

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 (strequal(direntp->d_name, "."))
                        continue;

                if (strequal(direntp->d_name, ".."))
                        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 (fd <= listen_fds_max) {
                        INFO("Inheriting fd %d (using the LISTEN_FDS environment variable)", fd);
                        continue;
                }

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

        /*
         * 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_syslog_enable();

        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(LXC_MAINLOOP_ERROR, "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 &&
            strequal(handler->conf->console.path, "none"))
                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_put_handler(struct lxc_handler *handler)
{
        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);
        if (handler->conf && handler->conf->reboot == REBOOT_NONE)
                free_disarm(handler);
        else
                handler->conf = NULL;
}

struct lxc_handler *lxc_init_handler(struct lxc_handler *old,
                                     const char *name, struct lxc_conf *conf,
                                     const char *lxcpath, bool daemonize)
{
        int nr_keep_fds = 0;
        int ret;
        struct lxc_handler *handler;

        if (!old)
                handler = zalloc(sizeof(*handler));
        else
                handler = old;
        if (!handler)
                return NULL;

        /* 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->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 (lxc_namespace_t idx = 0; idx < LXC_NS_MAX; idx++) {
                handler->nsfd[idx] = -EBADF;

                if (handler->conf->reboot == REBOOT_NONE)
                        continue;

                handler->nsfd_paths[idx][0] = '\0';
                handler->hook_argv[idx] = NULL;

                if (handler->hook_argc != 0)
                        handler->hook_argc = 0;
        }

        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]);
                handler->keep_fds[nr_keep_fds++] = handler->state_socket_pair[0];
                handler->keep_fds[nr_keep_fds++] = handler->state_socket_pair[1];
        }

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

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

        return handler;

on_error:
        lxc_put_handler(handler);

        return NULL;
}

int lxc_init(const char *name, struct lxc_handler *handler)
{
        __do_close 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)
                return log_error_errno(-1, errno, "Failed to open monitor status fd");

        handler->lsm_ops = lsm_init_static();
        TRACE("Initialized LSM");

        /* Begin by setting the state to STARTING. */
        ret = lxc_set_state(name, handler, STARTING);
        if (ret < 0)
                return log_error(-1, "Failed to set state to \"%s\"", lxc_state2str(STARTING));
        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)
                return log_error(-1, "Failed to run lxc.hook.pre-start for container \"%s\"", name);
        TRACE("Ran pre-start hooks");

        ret = lxc_terminal_parent(conf);
        if (ret < 0)
                return log_error(-1, "Failed to allocate terminal");

        /* 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)
                return log_error(-1, "Failed to setup SIGCHLD fd handler.");
        TRACE("Set up signal fd");

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

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

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

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

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

        return -1;
}

void lxc_expose_namespace_environment(const struct lxc_handler *handler)
{
        for (lxc_namespace_t i = 0; i < LXC_NS_MAX; i++) {
                int ret;
                const char *fd_path;

                if (handler->nsfd[i] < 0)
                        continue;

                fd_path = handler->nsfd_paths[i] + strcspn(handler->nsfd_paths[i], "/");
                ret = setenv(ns_info[i].env_name, fd_path, 1);
                if (ret < 0)
                        SYSERROR("Failed to set environment variable %s=%s",
                                 ns_info[i].env_name, fd_path);
                else
                        TRACE("Set environment variable %s=%s",
                              ns_info[i].env_name, fd_path);
        }
}

void lxc_end(struct lxc_handler *handler)
{
        int ret;
        struct lxc_list *cur, *next;
        const char *name = handler->name;
        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);

        /* Passing information to hooks via environment variables. */
        if (handler->conf->hooks_version > 0)
                lxc_expose_namespace_environment(handler);

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

        handler->lsm_ops->cleanup(handler->lsm_ops, handler->conf, handler->lxcpath);

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

        put_lxc_rootfs(&handler->conf->rootfs, true);

        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);
                TRACE("Set container state to \"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);
        close_prot_errno_disarm(handler->conf->devpts_fd);

        /* 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_put_handler(handler);
}

void lxc_abort(struct lxc_handler *handler)
{
        int ret = 0;
        int status;

        lxc_set_state(handler->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) && handler->pid > 0)
                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 int data_sock0 = handler->data_sock[0],
                                           data_sock1 = handler->data_sock[1];
        __do_close int devnull_fd = -EBADF, 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;

        lxc_sync_fini_parent(handler);

        if (lxc_abstract_unix_recv_one_fd(data_sock1, &status_fd, NULL, 0) < 0) {
                ERROR("Failed to receive status file descriptor from parent 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;
        }

        if (!lxc_sync_wait_parent(handler, START_SYNC_STARTUP))
                goto out_warn_father;

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

        /* 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_drop_groups() &&
                    (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 = strnprintf(path, sizeof(path), "%s/dev/null",
                                 handler->conf->rootfs.mount);
                if (ret < 0)
                        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");
                }
        }

        /*
         * Tell the parent task it can begin to configure the container and wait
         * for it to finish.
         */
        if (!lxc_sync_wake_parent(handler, START_SYNC_CONFIGURE))
                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_unshare_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");
                }
        }

        if (handler->ns_unshare_flags & CLONE_NEWTIME) {
                ret = unshare(CLONE_NEWTIME);
                if (ret < 0) {
                        if (errno != EINVAL) {
                                SYSERROR("Failed to unshare CLONE_NEWTIME");
                                goto out_warn_father;
                        }

                        handler->ns_clone_flags &= ~CLONE_NEWTIME;
                        SYSINFO("Kernel does not support CLONE_NEWTIME");
                } else {
                        __do_close int timens_fd = -EBADF;

                        INFO("Unshared CLONE_NEWTIME");

                        if (handler->conf->timens.s_boot)
                                ret = timens_offset_write(CLOCK_BOOTTIME, handler->conf->timens.s_boot, 0);
                        else if (handler->conf->timens.ns_boot)
                                ret = timens_offset_write(CLOCK_BOOTTIME, 0, handler->conf->timens.ns_boot);
                        if (ret) {
                                SYSERROR("Failed to write CLONE_BOOTTIME offset");
                                goto out_warn_father;
                        }
                        TRACE("Wrote CLOCK_BOOTTIME offset");

                        if (handler->conf->timens.s_monotonic)
                                ret = timens_offset_write(CLOCK_MONOTONIC, handler->conf->timens.s_monotonic, 0);
                        else if (handler->conf->timens.ns_monotonic)
                                ret = timens_offset_write(CLOCK_MONOTONIC, 0, handler->conf->timens.ns_monotonic);
                        if (ret) {
                                SYSERROR("Failed to write CLONE_MONOTONIC offset");
                                goto out_warn_father;
                        }
                        TRACE("Wrote CLOCK_MONOTONIC offset");

                        timens_fd = open("/proc/self/ns/time_for_children", O_RDONLY | O_CLOEXEC);
                        if (timens_fd < 0) {
                                SYSERROR("Failed to open \"/proc/self/ns/time_for_children\"");
                                goto out_warn_father;
                        }

                        ret = setns(timens_fd, CLONE_NEWTIME);
                        if (ret) {
                                SYSERROR("Failed to setns(%d(\"/proc/self/ns/time_for_children\"))", timens_fd);
                                goto out_warn_father;
                        }
                }
        }

        /* 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;
                }
        }

        if (!lxc_sync_wait_parent(handler, START_SYNC_POST_CONFIGURE))
                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 = handler->lsm_ops->process_label_set(handler->lsm_ops, 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");
        }

        /* 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 = 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.pty < 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;
                }
        }

        if (!lxc_sync_barrier_parent(handler, START_SYNC_CGROUP_LIMITS))
                goto out_warn_father;

        ret = lxc_sync_fds_child(handler);
        if (ret < 0) {
                SYSERROR("Failed to sync file descriptors with parent");
                goto out_warn_father;
        }

        if (!lxc_sync_wait_parent(handler, START_SYNC_READY_START))
                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;

        /* Make sure that the processes STDIO is correctly owned by the user that we are switching to */
        ret = fix_stdio_permissions(new_uid);
        if (ret)
                WARN("Failed to ajust stdio permissions");

        /* 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 (handler->conf->init_groups.size > 0) {
                                if (!lxc_setgroups(handler->conf->init_groups.list,
                                                   handler->conf->init_groups.size))
                                        goto out_warn_father;
                        } else {
                                if (!lxc_drop_groups())
                                        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, SYNC_ERROR);

out_error:
        return -1;
}

int resolve_clone_flags(struct lxc_handler *handler)
{
        int i;
        struct lxc_conf *conf = handler->conf;
        bool wants_timens = conf->timens.s_boot || conf->timens.ns_boot ||
                            conf->timens.s_monotonic || conf->timens.ns_monotonic;

        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;

                        if (i == LXC_NS_TIME && !wants_timens)
                                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);
        }

        if (wants_timens && (conf->ns_keep & ns_info[LXC_NS_TIME].clone_flag))
                return log_trace_errno(-1, EINVAL, "Requested to keep time namespace while also specifying offsets");

        /* Deal with namespaces that are unshared. */
        if (handler->ns_clone_flags & CLONE_NEWTIME)
                handler->ns_unshare_flags |= CLONE_NEWTIME;

        if (!pure_unified_layout(handler->cgroup_ops) && handler->ns_clone_flags & CLONE_NEWCGROUP)
                handler->ns_unshare_flags |= CLONE_NEWCGROUP;

        if ((handler->ns_clone_flags & (CLONE_NEWNET | CLONE_NEWUSER)) ==
            (CLONE_NEWNET | CLONE_NEWUSER))
                handler->ns_unshare_flags |= CLONE_NEWNET;

        /* Deal with namespaces that are spawned. */
        handler->ns_on_clone_flags = handler->ns_clone_flags & ~handler->ns_unshare_flags;

        handler->clone_flags = handler->ns_on_clone_flags | CLONE_PIDFD;

        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 placeholder 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 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;
        }

        if (!lxc_sync_init(handler))
                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;
        }

        /* Create a process in a new set of namespaces. */
        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;
                }

                if (handler->pid < 0) {
                        SYSERROR(LXC_CLONE_ERROR);
                        goto out_delete_net;
                }
        } else {
                int cgroup_fd = -EBADF;

                struct lxc_clone_args clone_args = {
                        .flags = handler->clone_flags,
                        .pidfd = ptr_to_u64(&handler->pidfd),
                        .exit_signal = SIGCHLD,
                };

                if (handler->ns_clone_flags & CLONE_NEWCGROUP) {
                        cgroup_fd = cgroup_unified_fd(cgroup_ops);
                        if (cgroup_fd >= 0) {
                                handler->clone_flags    |= CLONE_INTO_CGROUP;
                                clone_args.flags        |= CLONE_INTO_CGROUP;
                                clone_args.cgroup       = cgroup_fd;
                        }
                }

                /* Try to spawn directly into target cgroup. */
                handler->pid = lxc_clone3(&clone_args, CLONE_ARGS_SIZE_VER2);
                if (handler->pid < 0) {
                        SYSTRACE("Failed to spawn container directly into target cgroup");

                        /* Kernel might simply be too old for CLONE_INTO_CGROUP. */
                        handler->clone_flags            &= ~(CLONE_INTO_CGROUP | CLONE_NEWCGROUP);
                        handler->ns_on_clone_flags      &= ~CLONE_NEWCGROUP;
                        handler->ns_unshare_flags       |= CLONE_NEWCGROUP;

                        clone_args.flags                = handler->clone_flags;

                        handler->pid = lxc_clone3(&clone_args, CLONE_ARGS_SIZE_VER0);
                } else if (cgroup_fd >= 0) {
                        TRACE("Spawned container directly into target cgroup via cgroup2 fd %d", cgroup_fd);
                }

                /* Kernel might be too old for clone3(). */
                if (handler->pid < 0) {
                        SYSTRACE("Failed to spawn container via clone3()");

                /*
                 * In contrast to all other architectures arm64 verifies that
                 * the argument we use to retrieve the pidfd with is
                 * initialized to 0. But we need to be able to initialize it to
                 * a negative value such as our customary -EBADF so we can
                 * detect whether this kernel supports pidfds. If the syscall
                 * returns and the pidfd variable is set to something >= 0 then
                 * we know this is a kernel supporting pidfds. But if we can't
                 * set it to -EBADF then this won't work since 0 is a valid
                 * file descriptor too. And since legacy clone silently ignores
                 * unknown flags we are left without any way to detect support
                 * for pidfds. So let's special-case arm64 to not fail starting
                 * containers.
                 */
                #if defined(__aarch64__)
                        handler->pid = lxc_raw_legacy_clone(handler->clone_flags & ~CLONE_PIDFD, NULL);
                #else
                        handler->pid = lxc_raw_legacy_clone(handler->clone_flags, &handler->pidfd);
                #endif
                }

                if (handler->pid < 0) {
                        SYSERROR(LXC_CLONE_ERROR);
                        goto out_delete_net;
                }

                if (handler->pid == 0) {
                        (void)do_start(handler);
                        _exit(EXIT_FAILURE);
                }
        }
        if (handler->pidfd < 0)
                handler->clone_flags &= ~CLONE_PIDFD;
        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 = strnprintf(pidstr, 20, "%d", handler->pid);
        if (ret < 0)
                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)) {
                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;
                        }
                }
        }

        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_delegate_controllers(cgroup_ops)) {
                ERROR("Failed to delegate controllers to payload cgroup");
                goto out_delete_net;
        }

        if (!cgroup_ops->payload_enter(cgroup_ops, handler)) {
                ERROR("Failed to enter cgroups");
                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 (!lxc_sync_barrier_child(handler, START_SYNC_STARTUP))
                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_namespace(handler, LXC_NS_NET, "net");
                if (ret < 0) {
                        if (ret != -ENOENT) {
                                SYSERROR("Failed to preserve net namespace");
                                goto out_delete_net;
                        }
                }
        }
        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;
                }
        }

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

        /* Tell the child to continue its initialization. */
        if (!lxc_sync_wake_child(handler, START_SYNC_POST_CONFIGURE))
                goto out_delete_net;

        ret = lxc_rootfs_prepare_parent(handler);
        if (ret) {
                ERROR("Failed to prepare rootfs");
                goto out_delete_net;
        }

        if (handler->ns_clone_flags & CLONE_NEWNET) {
                ret = lxc_network_send_to_child(handler);
                if (ret < 0) {
                        SYSERROR("Failed to send veth names to child");
                        goto out_delete_net;
                }
        }

        if (!lxc_sync_wait_child(handler, START_SYNC_IDMAPPED_MOUNTS))
                goto out_delete_net;

        ret = lxc_idmapped_mounts_parent(handler);
        if (ret) {
                ERROR("Failed to setup mount entries");
                goto out_delete_net;
        }

        if (!lxc_sync_wait_child(handler, START_SYNC_CGROUP_LIMITS))
                goto out_delete_net;

        /*
         * With isolation the limiting devices cgroup was already setup, so
         * only setup devices here if we have no namespace directory.
         */
        if (!handler->conf->cgroup_meta.namespace_dir &&
            !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");

        cgroup_ops->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;
        }

        if (!lxc_sync_wake_child(handler, START_SYNC_FDS))
                goto out_delete_net;

        if (handler->ns_unshare_flags & CLONE_NEWCGROUP) {
                /* Now we're ready to preserve the cgroup namespace */
                ret = lxc_try_preserve_namespace(handler, LXC_NS_CGROUP, "cgroup");
                if (ret < 0) {
                        if (ret != -ENOENT) {
                                SYSERROR("Failed to preserve cgroup namespace");
                                goto out_delete_net;
                        }
                }
        }

        if (handler->ns_unshare_flags & CLONE_NEWTIME) {
                /* Now we're ready to preserve the time namespace */
                ret = lxc_try_preserve_namespace(handler, LXC_NS_TIME, "time");
                if (ret < 0) {
                        if (ret != -ENOENT) {
                                SYSERROR("Failed to preserve time namespace");
                                goto out_delete_net;
                        }
                }
        }

        ret = lxc_sync_fds_parent(handler);
        if (ret < 0) {
                SYSERROR("Failed to sync file descriptors with child");
                goto out_delete_net;
        }

        ret = lxc_terminal_setup(conf);
        if (ret < 0) {
                SYSERROR("Failed to create console");
                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
         * START_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).
         */
        if (!lxc_sync_barrier_child(handler, START_SYNC_READY_START))
                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);

        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(handler);

out_sync_fini:
        lxc_sync_fini(handler);

        return -1;
}

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

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

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

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

        /* If the rootfs is not a blockdev, prevent the container from marking
         * it readonly.
         * If the container is unprivileged then skip rootfs pinning.
         */
        ret = lxc_rootfs_init(conf, !lxc_list_empty(&conf->id_map));
        if (ret) {
                ERROR("Failed to handle rootfs pinning for container \"%s\"", handler->name);
                ret = -1;
                goto out_abort;
        }

        if (geteuid() == 0 && !lxc_list_empty(&conf->id_map)) {
                /*
                 * Most filesystems can't be mounted inside a userns so handle them here.
                 */
                if (rootfs_is_blockdev(conf)) {
                        ret = unshare(CLONE_NEWNS);
                        if (ret < 0) {
                                ERROR("Failed to unshare CLONE_NEWNS");
                                goto out_abort;
                        }
                        INFO("Unshared CLONE_NEWNS");

                        ret = lxc_setup_rootfs_prepare_root(conf, name, lxcpath);
                        if (ret < 0) {
                                ERROR("Error setting up rootfs mount as root before spawn");
                                goto out_abort;
                        }
                        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_delete_network;
        }

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

        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");

        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;

        lxc_delete_network(handler);
        detach_block_device(handler->conf);
        lxc_end(handler);
        return ret;

out_abort:
        lxc_abort(handler);
        lxc_end(handler);
        return ret;

out_detach_blockdev:
        lxc_abort(handler);
        detach_block_device(handler->conf);
        lxc_end(handler);
        return ret;

out_delete_network:
        lxc_abort(handler);
        lxc_restore_phys_nics_to_netns(handler);
        lxc_delete_network(handler);
        detach_block_device(handler->conf);
        lxc_end(handler);
        return ret;
}

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(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(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 = strnprintf(destroy, sizeof(destroy), "%s/%s", handler->lxcpath, name);
        if (ret < 0) {
                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);
}