start: set PR_SET_NO_NEW_PRIVS when requested

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

/*
 * lxc: linux Container library
 *
 * (C) Copyright IBM Corp. 2007, 2008
 *
 * Authors:
 * Daniel Lezcano <daniel.lezcano at free.fr>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#define _GNU_SOURCE
#include "config.h"

#include <alloca.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <grp.h>
#include <poll.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.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>

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

#if !HAVE_DECL_PR_CAPBSET_DROP
#define PR_CAPBSET_DROP 24
#endif

#include "af_unix.h"
#include "bdev.h"
#include "caps.h"
#include "cgroup.h"
#include "commands.h"
#include "conf.h"
#include "console.h"
#include "error.h"
#include "log.h"
#include "lxclock.h"
#include "lxcseccomp.h"
#include "lxcutmp.h"
#include "mainloop.h"
#include "monitor.h"
#include "namespace.h"
#include "start.h"
#include "sync.h"
#include "utils.h"
#include "lsm/lsm.h"

lxc_log_define(lxc_start, lxc);

const struct ns_info ns_info[LXC_NS_MAX] = {
        [LXC_NS_MNT] = {"mnt", CLONE_NEWNS},
        [LXC_NS_PID] = {"pid", CLONE_NEWPID},
        [LXC_NS_UTS] = {"uts", CLONE_NEWUTS},
        [LXC_NS_IPC] = {"ipc", CLONE_NEWIPC},
        [LXC_NS_USER] = {"user", CLONE_NEWUSER},
        [LXC_NS_NET] = {"net", CLONE_NEWNET},
        [LXC_NS_CGROUP] = {"cgroup", CLONE_NEWCGROUP}
};

extern void mod_all_rdeps(struct lxc_container *c, bool inc);
static bool do_destroy_container(struct lxc_conf *conf);
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)
{
        size_t len = strlen(path);
        char *copy = alloca(len + 1), *p, *e, saved;
        strcpy(copy, path);

        p = copy;
        e = copy + len;
        while (p < e) {
                while (p < e && *p == '/')
                        p++;
                while (p < e && *p != '/')
                        p++;
                saved = *p;
                *p = '\0';
                if (access(copy, X_OK)) {
                        SYSERROR("could not access %s.  Please grant it 'x' " \
                              "access, or add an ACL for the container root.",
                              copy);
                        return;
                }
                *p = saved;
        }
}

static void close_ns(int ns_fd[LXC_NS_MAX]) {
        int i;

        for (i = 0; i < LXC_NS_MAX; i++) {
                if (ns_fd[i] > -1) {
                        close(ns_fd[i]);
                        ns_fd[i] = -1;
                }
        }
}

/*
 * preserve_ns: open /proc/@pid/ns/@ns for each namespace specified
 * in clone_flags.
 * Return true on success, false on failure.  On failure, leave an error
 * message in *errmsg, which caller must free.
 */
static bool preserve_ns(int ns_fd[LXC_NS_MAX], int clone_flags, pid_t pid,
                        char **errmsg)
{
        int i, ret;
        char path[MAXPATHLEN];

        for (i = 0; i < LXC_NS_MAX; i++)
                ns_fd[i] = -1;

        snprintf(path, MAXPATHLEN, "/proc/%d/ns", pid);
        if (access(path, X_OK)) {
                if (asprintf(errmsg, "Kernel does not support setns.") == -1)
                        *errmsg = NULL;
                return false;
        }

        for (i = 0; i < LXC_NS_MAX; i++) {
                if ((clone_flags & ns_info[i].clone_flag) == 0)
                        continue;
                snprintf(path, MAXPATHLEN, "/proc/%d/ns/%s", pid,
                         ns_info[i].proc_name);
                ns_fd[i] = open(path, O_RDONLY | O_CLOEXEC);
                if (ns_fd[i] < 0)
                        goto error;
        }

        return true;

error:
        if (errno == ENOENT) {
                ret = asprintf(errmsg, "Kernel does not support setns for %s",
                        ns_info[i].proc_name);
        } else {
                ret = asprintf(errmsg, "Failed to open %s: %s",
                        path, strerror(errno));
        }
        if (ret == -1)
                *errmsg = NULL;
        close_ns(ns_fd);
        return false;
}

static int attach_ns(const int ns_fd[LXC_NS_MAX]) {
        int i;

        for (i = 0; i < LXC_NS_MAX; i++) {
                if (ns_fd[i] < 0)
                        continue;

                if (setns(ns_fd[i], 0) != 0)
                        goto error;
        }
        return 0;

error:
        SYSERROR("failed to set namespace '%s'", ns_info[i].proc_name);
        return -1;
}

static int match_fd(int fd)
{
        return (fd == 0 || fd == 1 || fd == 2);
}

/*
 * Check for any fds we need to close
 * * if fd_to_ignore != -1, then if we find that fd open we will ignore it.
 * * By default we warn about open fds we find.
 * * If closeall is true, we will close open fds.
 * * If lxc-start was passed "-C", then conf->close_all_fds will be true,
 *     in which case we also close all open fds.
 * * A daemonized container will always pass closeall=true.
 */
int lxc_check_inherited(struct lxc_conf *conf, bool closeall, int fd_to_ignore)
{
        struct dirent *direntp;
        int fd, fddir;
        DIR *dir;

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

restart:
        dir = opendir("/proc/self/fd");
        if (!dir) {
                WARN("failed to open directory: %m");
                return -1;
        }

        fddir = dirfd(dir);

        while ((direntp = readdir(dir))) {
                if (!direntp)
                        break;

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

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

                fd = atoi(direntp->d_name);

                if (fd == fddir || fd == lxc_log_fd || fd == fd_to_ignore)
                        continue;

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

                if (match_fd(fd))
                        continue;

                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)
{
        sigset_t mask;
        int fd;

        /* Block everything except serious error signals */
        if (sigfillset(&mask) ||
            sigdelset(&mask, SIGILL) ||
            sigdelset(&mask, SIGSEGV) ||
            sigdelset(&mask, SIGBUS) ||
            sigdelset(&mask, SIGWINCH) ||
            sigprocmask(SIG_BLOCK, &mask, oldmask)) {
                SYSERROR("failed to set signal mask");
                return -1;
        }

        fd = signalfd(-1, &mask, 0);
        if (fd < 0) {
                SYSERROR("failed to create the signal fd");
                return -1;
        }

        if (fcntl(fd, F_SETFD, FD_CLOEXEC)) {
                SYSERROR("failed to set sigfd to close-on-exec");
                close(fd);
                return -1;
        }

        DEBUG("sigchild handler set");

        return fd;
}

static int signal_handler(int fd, uint32_t events, void *data,
                          struct lxc_epoll_descr *descr)
{
        struct signalfd_siginfo siginfo;
        siginfo_t info;
        int ret;
        pid_t *pid = data;
        bool init_died = false;

        ret = read(fd, &siginfo, sizeof(siginfo));
        if (ret < 0) {
                ERROR("failed to read signal info");
                return -1;
        }

        if (ret != sizeof(siginfo)) {
                ERROR("unexpected siginfo size");
                return -1;
        }

        // check whether init is running
        info.si_pid = 0;
        ret = waitid(P_PID, *pid, &info, WEXITED | WNOWAIT | WNOHANG);
        if (ret == 0 && info.si_pid == *pid) {
                init_died = true;
        }

        if (siginfo.ssi_signo != SIGCHLD) {
                kill(*pid, siginfo.ssi_signo);
                INFO("forwarded signal %d to pid %d", siginfo.ssi_signo, *pid);
                return init_died ? 1 : 0;
        }

        if (siginfo.ssi_code == CLD_STOPPED ||
            siginfo.ssi_code == CLD_CONTINUED) {
                INFO("container init process was stopped/continued");
                return init_died ? 1 : 0;
        }

        /* more robustness, protect ourself from a SIGCHLD sent
         * by a process different from the container init
         */
        if (siginfo.ssi_pid != *pid) {
                WARN("invalid pid for SIGCHLD");
                return init_died ? 1 : 0;
        }

        DEBUG("container init process exited");
        return 1;
}

int lxc_set_state(const char *name, struct lxc_handler *handler, lxc_state_t state)
{
        handler->state = state;
        lxc_monitor_send_state(name, state, handler->lxcpath);
        return 0;
}

int lxc_poll(const char *name, struct lxc_handler *handler)
{
        int sigfd = handler->sigfd;
        int pid = handler->pid;
        struct lxc_epoll_descr descr;

        if (lxc_mainloop_open(&descr)) {
                ERROR("failed to create mainloop");
                goto out_sigfd;
        }

        if (lxc_mainloop_add_handler(&descr, sigfd, signal_handler, &pid)) {
                ERROR("failed to add handler for the signal");
                goto out_mainloop_open;
        }

        if (lxc_console_mainloop_add(&descr, handler->conf)) {
                ERROR("failed to add console handler to mainloop");
                goto out_mainloop_open;
        }

        if (lxc_cmd_mainloop_add(name, &descr, handler)) {
                ERROR("failed to add command handler to mainloop");
                goto out_mainloop_open;
        }

        if (handler->conf->need_utmp_watch) {
                #if HAVE_SYS_CAPABILITY_H
                if (lxc_utmp_mainloop_add(&descr, handler)) {
                        ERROR("failed to add utmp handler to mainloop");
                        goto out_mainloop_open;
                }
                #else
                        DEBUG("not starting utmp handler as cap_sys_boot cannot be dropped without capabilities support");
                #endif
        }

        return lxc_mainloop(&descr, -1);

out_mainloop_open:
        lxc_mainloop_close(&descr);
out_sigfd:
        close(sigfd);
        return -1;
}

struct lxc_handler *lxc_init(const char *name, struct lxc_conf *conf, const char *lxcpath)
{
        int i;
        struct lxc_handler *handler;

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

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

        handler->ttysock[0] = handler->ttysock[1] = -1;
        handler->conf = conf;
        handler->lxcpath = lxcpath;
        handler->pinfd = -1;

        for (i = 0; i < LXC_NS_MAX; i++)
                handler->nsfd[i] = -1;

        lsm_init();

        handler->name = strdup(name);
        if (!handler->name) {
                ERROR("failed to allocate memory");
                goto out_free;
        }

        if (lxc_cmd_init(name, handler, lxcpath))
                goto out_free_name;

        if (lxc_read_seccomp_config(conf) != 0) {
                ERROR("failed loading seccomp policy");
                goto out_close_maincmd_fd;
        }

        /* Begin by setting the state to STARTING */
        if (lxc_set_state(name, handler, STARTING)) {
                ERROR("failed to set state '%s'", lxc_state2str(STARTING));
                goto out_close_maincmd_fd;
        }

        /* Start of environment variable setup for hooks */
        if (name && setenv("LXC_NAME", name, 1)) {
                SYSERROR("failed to set environment variable for container name");
        }
        if (conf->rcfile && setenv("LXC_CONFIG_FILE", conf->rcfile, 1)) {
                SYSERROR("failed to set environment variable for config path");
        }
        if (conf->rootfs.mount && setenv("LXC_ROOTFS_MOUNT", conf->rootfs.mount, 1)) {
                SYSERROR("failed to set environment variable for rootfs mount");
        }
        if (conf->rootfs.path && setenv("LXC_ROOTFS_PATH", conf->rootfs.path, 1)) {
                SYSERROR("failed to set environment variable for rootfs mount");
        }
        if (conf->console.path && setenv("LXC_CONSOLE", conf->console.path, 1)) {
                SYSERROR("failed to set environment variable for console path");
        }
        if (conf->console.log_path && setenv("LXC_CONSOLE_LOGPATH", conf->console.log_path, 1)) {
                SYSERROR("failed to set environment variable for console log");
        }
        if (setenv("LXC_CGNS_AWARE", "1", 1)) {
                SYSERROR("failed to set LXC_CGNS_AWARE environment variable");
        }
        /* End of environment variable setup for hooks */

        if (run_lxc_hooks(name, "pre-start", conf, handler->lxcpath, NULL)) {
                ERROR("failed to run pre-start hooks for container '%s'.", name);
                goto out_aborting;
        }

        /* 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 set sigchild fd handler");
                goto out_delete_tty;
        }

        /* do this after setting up signals since it might unblock SIGWINCH */
        if (lxc_console_create(conf)) {
                ERROR("failed to create console");
                goto out_restore_sigmask;
        }

        if (ttys_shift_ids(conf) < 0) {
                ERROR("Failed to shift tty into container");
                goto out_restore_sigmask;
        }

        INFO("'%s' is initialized", name);
        return handler;

out_restore_sigmask:
        sigprocmask(SIG_SETMASK, &handler->oldmask, NULL);
out_delete_tty:
        lxc_delete_tty(&conf->tty_info);
out_aborting:
        lxc_set_state(name, handler, ABORTING);
out_close_maincmd_fd:
        close(conf->maincmd_fd);
        conf->maincmd_fd = -1;
out_free_name:
        free(handler->name);
        handler->name = NULL;
out_free:
        free(handler);
        return NULL;
}

void lxc_fini(const char *name, struct lxc_handler *handler)
{
        int i, rc;
        pid_t self = getpid();
        char *namespaces[LXC_NS_MAX+1];
        size_t namespace_count = 0;

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

        for (i = 0; i < LXC_NS_MAX; i++) {
                if (handler->nsfd[i] != -1) {
                        rc = asprintf(&namespaces[namespace_count], "%s:/proc/%d/fd/%d",
                                      ns_info[i].proc_name, self, handler->nsfd[i]);
                        if (rc == -1) {
                                SYSERROR("failed to allocate memory");
                                break;
                        }
                        ++namespace_count;
                }
        }
        namespaces[namespace_count] = NULL;

        if (handler->conf->reboot && setenv("LXC_TARGET", "reboot", 1)) {
                SYSERROR("failed to set environment variable for stop target");
        }
        if (!handler->conf->reboot && setenv("LXC_TARGET", "stop", 1)) {
                SYSERROR("failed to set environment variable for stop target");
        }

        if (run_lxc_hooks(name, "stop", handler->conf, handler->lxcpath, namespaces))
                ERROR("failed to run stop hooks for container '%s'.", name);

        while (namespace_count--)
                free(namespaces[namespace_count]);
        for (i = 0; i < LXC_NS_MAX; i++) {
                if (handler->nsfd[i] != -1) {
                        close(handler->nsfd[i]);
                        handler->nsfd[i] = -1;
                }
        }
        lxc_set_state(name, handler, STOPPED);

        if (run_lxc_hooks(name, "post-stop", handler->conf, handler->lxcpath, NULL)) {
                ERROR("failed to run post-stop hooks for container '%s'.", name);
                if (handler->conf->reboot) {
                        WARN("Container will be stopped instead of rebooted.");
                        handler->conf->reboot = 0;
                        setenv("LXC_TARGET", "stop", 1);
                }
        }

        /* reset mask set by setup_signal_fd */
        if (sigprocmask(SIG_SETMASK, &handler->oldmask, NULL))
                WARN("failed to restore sigprocmask");

        lxc_console_delete(&handler->conf->console);
        lxc_delete_tty(&handler->conf->tty_info);
        close(handler->conf->maincmd_fd);
        handler->conf->maincmd_fd = -1;
        free(handler->name);
        if (handler->ttysock[0] != -1) {
                close(handler->ttysock[0]);
                close(handler->ttysock[1]);
        }

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

        cgroup_destroy(handler);
        free(handler);
}

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

        lxc_set_state(name, handler, ABORTING);
        if (handler->pid > 0)
                kill(handler->pid, SIGKILL);
        while ((ret = waitpid(-1, &status, 0)) > 0) ;
}

#include <sys/reboot.h>
#include <linux/reboot.h>

/*
 * reboot(LINUX_REBOOT_CMD_CAD_ON) will return -EINVAL
 * in a child pid namespace if container reboot support exists.
 * Otherwise, it will either succeed or return -EPERM.
 */
static int container_reboot_supported(void *arg)
{
        int *cmd = arg;
        int ret;

        ret = reboot(*cmd);
        if (ret == -1 && errno == EINVAL)
                return 1;
        return 0;
}

static int must_drop_cap_sys_boot(struct lxc_conf *conf)
{
        FILE *f;
        int ret, cmd, v, flags;
        long stack_size = 4096;
        void *stack = alloca(stack_size);
        int status;
        pid_t pid;

        f = fopen("/proc/sys/kernel/ctrl-alt-del", "r");
        if (!f) {
                DEBUG("failed to open /proc/sys/kernel/ctrl-alt-del");
                return 1;
        }

        ret = fscanf(f, "%d", &v);
        fclose(f);
        if (ret != 1) {
                DEBUG("Failed to read /proc/sys/kernel/ctrl-alt-del");
                return 1;
        }
        cmd = v ? LINUX_REBOOT_CMD_CAD_ON : LINUX_REBOOT_CMD_CAD_OFF;

        flags = CLONE_NEWPID | SIGCHLD;
        if (!lxc_list_empty(&conf->id_map))
                flags |= CLONE_NEWUSER;

#ifdef __ia64__
        pid = __clone2(container_reboot_supported, stack, stack_size, flags,  &cmd);
#else
        stack += stack_size;
        pid = clone(container_reboot_supported, stack, flags, &cmd);
#endif
        if (pid < 0) {
                if (flags & CLONE_NEWUSER)
                        ERROR("failed to clone (%#x): %s (includes CLONE_NEWUSER)", flags, strerror(errno));
                else
                        ERROR("failed to clone (%#x): %s", flags, strerror(errno));
                return -1;
        }
        if (wait(&status) < 0) {
                SYSERROR("unexpected wait error: %m");
                return -1;
        }

        if (WEXITSTATUS(status) != 1)
                return 1;

        return 0;
}

/*
 * netpipe is used in the unprivileged case to transfer the ifindexes
 * from parent to child
 */
static int netpipe = -1;

static inline int count_veths(struct lxc_list *network)
{
        struct lxc_list *iterator;
        struct lxc_netdev *netdev;
        int count = 0;

        lxc_list_for_each(iterator, network) {
                netdev = iterator->elem;
                if (netdev->type != LXC_NET_VETH)
                        continue;
                count++;
        }
        return count;
}

static int read_unpriv_netifindex(struct lxc_list *network)
{
        struct lxc_list *iterator;
        struct lxc_netdev *netdev;

        if (netpipe == -1)
                return 0;
        lxc_list_for_each(iterator, network) {
                netdev = iterator->elem;
                if (netdev->type != LXC_NET_VETH)
                        continue;
                if (!(netdev->name = malloc(IFNAMSIZ))) {
                        ERROR("Out of memory");
                        close(netpipe);
                        return -1;
                }
                if (read(netpipe, netdev->name, IFNAMSIZ) != IFNAMSIZ) {
                        close(netpipe);
                        return -1;
                }
        }
        close(netpipe);
        return 0;
}

static int do_start(void *data)
{
        struct lxc_list *iterator;
        struct lxc_handler *handler = data;
        int devnull_fd = -1, ret;
        char path[PATH_MAX];

        if (sigprocmask(SIG_SETMASK, &handler->oldmask, NULL)) {
                SYSERROR("failed to set sigprocmask");
                return -1;
        }

        /* 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.
         */
        if (prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0)) {
                SYSERROR("failed to set pdeath signal");
                return -1;
        }

        lxc_sync_fini_parent(handler);

        /* don't leak the pinfd to the container */
        if (handler->pinfd >= 0) {
                close(handler->pinfd);
        }

        if (lxc_sync_wait_parent(handler, LXC_SYNC_STARTUP))
                return -1;

        /* Unshare CLONE_NEWNET after CLONE_NEWUSER  - see
          https://github.com/lxc/lxd/issues/1978 */
        if ((handler->clone_flags & (CLONE_NEWNET | CLONE_NEWUSER)) ==
                        (CLONE_NEWNET | CLONE_NEWUSER)) {
                ret = unshare(CLONE_NEWNET);
                if (ret < 0) {
                        SYSERROR("Error unsharing network namespace");
                        goto out_warn_father;
                }
        }

        /* Tell the parent task it can begin to configure the
         * container and wait for it to finish
         */
        if (lxc_sync_barrier_parent(handler, LXC_SYNC_CONFIGURE))
                return -1;

        if (read_unpriv_netifindex(&handler->conf->network) < 0)
                goto out_warn_father;

        /*
         * if we are in a new user namespace, become root there to have
         * privilege over our namespace. When using lxc-execute we default to root,
         * but this can be overriden using the lxc.init_uid and lxc.init_gid
         * configuration options.
         */
        if (!lxc_list_empty(&handler->conf->id_map)) {
                gid_t new_gid = 0;
                if (handler->conf->is_execute && handler->conf->init_gid)
                        new_gid = handler->conf->init_gid;

                uid_t new_uid = 0;
                if (handler->conf->is_execute && handler->conf->init_uid)
                        new_uid = handler->conf->init_uid;

                NOTICE("switching to gid/uid %d/%d in new user namespace", new_gid, new_uid);
                if (setgid(new_gid)) {
                        SYSERROR("setgid");
                        goto out_warn_father;
                }
                if (setuid(new_uid)) {
                        SYSERROR("setuid");
                        goto out_warn_father;
                }
                if (setgroups(0, NULL)) {
                        SYSERROR("setgroups");
                        goto out_warn_father;
                }
        }

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

        #if HAVE_SYS_CAPABILITY_H
        if (handler->conf->need_utmp_watch) {
                if (prctl(PR_CAPBSET_DROP, CAP_SYS_BOOT, 0, 0, 0)) {
                        SYSERROR("failed to remove CAP_SYS_BOOT capability");
                        goto out_warn_father;
                }
                DEBUG("Dropped cap_sys_boot");
        }
        #endif

        ret = snprintf(path, sizeof(path), "%s/dev/null", handler->conf->rootfs.mount);
        if (ret < 0 || ret >= sizeof(path)) {
                SYSERROR("sprintf'd too many chars");
                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->backgrounded && !handler->conf->autodev && access(path, F_OK) < 0) {
                devnull_fd = open_devnull();

                if (devnull_fd < 0)
                        goto out_warn_father;
                WARN("using host's /dev/null for container init's std fds, migraiton won't work");
        }

        /* Setup the container, ip, names, utsname, ... */
        if (lxc_setup(handler)) {
                ERROR("failed to setup the container");
                goto out_warn_father;
        }

        /* ask father to setup cgroups and wait for him to finish */
        if (lxc_sync_barrier_parent(handler, LXC_SYNC_CGROUP))
                goto out_error;

        /* Set the label to change to when we exec(2) the container's init */
        if (lsm_process_label_set(NULL, handler->conf, 1, 1) < 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) {
                if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) < 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_console_create()
         * so make sure that that pty is stdin,stdout,stderr.
         */
        if (lxc_console_set_stdfds(handler->conf->console.slave) < 0)
                goto out_warn_father;

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

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

        if (run_lxc_hooks(handler->name, "start", handler->conf, handler->lxcpath, NULL)) {
                ERROR("failed to run start hooks for container '%s'.", handler->name);
                goto out_warn_father;
        }

        /* The clearenv() and putenv() calls have been moved here
         * to allow us to use environment variables passed to the various
         * hooks, such as the start hook above.  Not all of the
         * variables like CONFIG_PATH or ROOTFS are valid in this
         * context but others are. */
        if (clearenv()) {
                SYSERROR("failed to clear environment");
                /* don't error out though */
        }

        lxc_list_for_each(iterator, &handler->conf->environment) {
                if (putenv((char *)iterator->elem)) {
                        SYSERROR("failed to set environment variable '%s'", (char *)iterator->elem);
                        goto out_warn_father;
                }
        }

        if (putenv("container=lxc")) {
                SYSERROR("failed to set environment variable 'container=lxc'");
                goto out_warn_father;
        }

        if (handler->conf->pty_names) {
                if (putenv(handler->conf->pty_names)) {
                        SYSERROR("failed to set environment variable for container ptys");
                        goto out_warn_father;
                }
        }

        close(handler->sigfd);

        if (devnull_fd < 0) {
                devnull_fd = open_devnull();

                if (devnull_fd < 0)
                        goto out_warn_father;
        }

        if (handler->backgrounded && set_stdfds(devnull_fd))
                goto out_warn_father;

        if (devnull_fd >= 0) {
                close(devnull_fd);
                devnull_fd = -1;
        }

        if (cgns_supported() && unshare(CLONE_NEWCGROUP) != 0) {
                SYSERROR("Failed to unshare cgroup namespace");
                goto out_warn_father;
        }

        setsid();

        /* 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:
        if (devnull_fd >= 0)
                close(devnull_fd);

        return -1;
}

static int save_phys_nics(struct lxc_conf *conf)
{
        struct lxc_list *iterator;
        int am_root = (getuid() == 0);

        if (!am_root)
                return 0;

        lxc_list_for_each(iterator, &conf->network) {
                struct lxc_netdev *netdev = iterator->elem;

                if (netdev->type != LXC_NET_PHYS)
                        continue;
                conf->saved_nics = realloc(conf->saved_nics,
                                (conf->num_savednics+1)*sizeof(struct saved_nic));
                if (!conf->saved_nics) {
                        SYSERROR("failed to allocate memory");
                        return -1;
                }
                conf->saved_nics[conf->num_savednics].ifindex = netdev->ifindex;
                conf->saved_nics[conf->num_savednics].orig_name = strdup(netdev->link);
                if (!conf->saved_nics[conf->num_savednics].orig_name) {
                        SYSERROR("failed to allocate memory");
                        return -1;
                }
                INFO("stored saved_nic #%d idx %d name %s", conf->num_savednics,
                        conf->saved_nics[conf->num_savednics].ifindex,
                        conf->saved_nics[conf->num_savednics].orig_name);
                conf->num_savednics++;
        }

        return 0;
}

static int recv_fd(int sock, int *fd)
{
        if (lxc_abstract_unix_recv_fd(sock, fd, NULL, 0) < 0) {
                SYSERROR("Error receiving tty fd from child");
                return -1;
        }
        if (*fd == -1)
                return -1;
        return 0;
}

static int recv_ttys_from_child(struct lxc_handler *handler)
{
        struct lxc_conf *conf = handler->conf;
        int i, sock = handler->ttysock[1];
        struct lxc_tty_info *tty_info = &conf->tty_info;

        if (!conf->tty)
                return 0;

        tty_info->pty_info = malloc(sizeof(*tty_info->pty_info)*conf->tty);
        if (!tty_info->pty_info) {
                SYSERROR("failed to allocate pty_info");
                return -1;
        }

        for (i = 0; i < conf->tty; i++) {
                struct lxc_pty_info *pty_info = &tty_info->pty_info[i];
                pty_info->busy = 0;
                if (recv_fd(sock, &pty_info->slave) < 0 ||
                                recv_fd(sock, &pty_info->master) < 0) {
                        ERROR("Error receiving tty info from child");
                        return -1;
                }
        }
        tty_info->nbtty = conf->tty;

        return 0;
}

void resolve_clone_flags(struct lxc_handler *handler)
{
        handler->clone_flags = CLONE_NEWPID | CLONE_NEWNS;

        if (!lxc_list_empty(&handler->conf->id_map)) {
                INFO("Cloning a new user namespace");
                handler->clone_flags |= CLONE_NEWUSER;
        }

        if (handler->conf->inherit_ns_fd[LXC_NS_NET] == -1) {
                if (!lxc_requests_empty_network(handler))
                        handler->clone_flags |= CLONE_NEWNET;
        } else {
                INFO("Inheriting a net namespace");
        }

        if (handler->conf->inherit_ns_fd[LXC_NS_IPC] == -1) {
                handler->clone_flags |= CLONE_NEWIPC;
        } else {
                INFO("Inheriting an IPC namespace");
        }

        if (handler->conf->inherit_ns_fd[LXC_NS_UTS] == -1) {
                handler->clone_flags |= CLONE_NEWUTS;
        } else {
                INFO("Inheriting a UTS namespace");
        }
}

static int lxc_spawn(struct lxc_handler *handler)
{
        int failed_before_rename = 0;
        const char *name = handler->name;
        char *errmsg = NULL;
        bool cgroups_connected = false;
        int saved_ns_fd[LXC_NS_MAX];
        int preserve_mask = 0, i, flags;
        int netpipepair[2], nveths;

        netpipe = -1;

        for (i = 0; i < LXC_NS_MAX; i++)
                if (handler->conf->inherit_ns_fd[i] != -1)
                        preserve_mask |= ns_info[i].clone_flag;

        if (lxc_sync_init(handler))
                return -1;

        if (socketpair(AF_UNIX, SOCK_DGRAM, 0, handler->ttysock) < 0) {
                lxc_sync_fini(handler);
                return -1;
        }

        resolve_clone_flags(handler);

        if (handler->clone_flags & CLONE_NEWNET) {
                if (!lxc_list_empty(&handler->conf->network)) {

                        /* Find gateway addresses from the link device, which is
                         * no longer accessible inside the container. Do this
                         * before creating network interfaces, since goto
                         * out_delete_net does not work before lxc_clone. */
                        if (lxc_find_gateway_addresses(handler)) {
                                ERROR("failed to find gateway addresses");
                                lxc_sync_fini(handler);
                                return -1;
                        }

                        /* that should be done before the clone because we will
                         * fill the netdev index and use them in the child
                         */
                        if (lxc_create_network(handler)) {
                                ERROR("failed to create the network");
                                lxc_sync_fini(handler);
                                return -1;
                        }
                }

                if (save_phys_nics(handler->conf)) {
                        ERROR("failed to save physical nic info");
                        goto out_abort;
                }
        }

        if (!cgroup_init(handler)) {
                ERROR("failed initializing cgroup support");
                goto out_delete_net;
        }

        cgroups_connected = true;

        if (!cgroup_create(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 (lxc_list_empty(&handler->conf->id_map)) {
                handler->pinfd = pin_rootfs(handler->conf->rootfs.path);
                if (handler->pinfd == -1)
                        INFO("failed to pin the container's rootfs");
        }

        if (!preserve_ns(saved_ns_fd, preserve_mask, getpid(), &errmsg)) {
                SYSERROR("Failed to preserve requested namespaces: %s",
                        errmsg ? errmsg : "(Out of memory)");
                free(errmsg);
                goto out_delete_net;
        }
        if (attach_ns(handler->conf->inherit_ns_fd) < 0)
                goto out_delete_net;

        if (am_unpriv() && (nveths = count_veths(&handler->conf->network))) {
                if (pipe(netpipepair) < 0) {
                        SYSERROR("Error creating pipe");
                        goto out_delete_net;
                }
                /* store netpipe in the global var for do_start's use */
                netpipe = netpipepair[0];
        }

        /* Create a process in a new set of namespaces */
        flags = handler->clone_flags;
        if (handler->clone_flags & CLONE_NEWUSER)
                flags &= ~CLONE_NEWNET;
        handler->pid = lxc_clone(do_start, handler, handler->clone_flags);
        if (handler->pid < 0) {
                SYSERROR("failed to fork into a new namespace");
                goto out_delete_net;
        }

        if (!preserve_ns(handler->nsfd, handler->clone_flags | preserve_mask, handler->pid, &errmsg)) {
                INFO("Failed to store namespace references for stop hook: %s",
                        errmsg ? errmsg : "(Out of memory)");
                free(errmsg);
        }

        if (attach_ns(saved_ns_fd))
                WARN("failed to restore saved namespaces");

        lxc_sync_fini_child(handler);

        /* 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 (lxc_map_ids(&handler->conf->id_map, handler->pid)) {
                ERROR("failed to set up id mapping");
                goto out_delete_net;
        }

        if (lxc_sync_wake_child(handler, LXC_SYNC_STARTUP)) {
                failed_before_rename = 1;
                goto out_delete_net;
        }

        if (lxc_sync_wait_child(handler, LXC_SYNC_CONFIGURE)) {
                failed_before_rename = 1;
                goto out_delete_net;
        }

        if (!cgroup_create_legacy(handler)) {
                ERROR("failed to setup the legacy cgroups for %s", name);
                goto out_delete_net;
        }
        if (!cgroup_setup_limits(handler, false)) {
                ERROR("failed to setup the cgroup limits for '%s'", name);
                goto out_delete_net;
        }

        if (!cgroup_enter(handler))
                goto out_delete_net;

        if (!cgroup_chown(handler))
                goto out_delete_net;

        if (failed_before_rename)
                goto out_delete_net;

        /* Create the network configuration */
        if (handler->clone_flags & CLONE_NEWNET) {
                if (lxc_assign_network(handler->lxcpath, handler->name,
                                        &handler->conf->network, handler->pid)) {
                        ERROR("failed to create the configured network");
                        goto out_delete_net;
                }
        }

        if (netpipe != -1) {
                struct lxc_list *iterator;
                struct lxc_netdev *netdev;

                close(netpipe);
                lxc_list_for_each(iterator, &handler->conf->network) {
                        netdev = iterator->elem;
                        if (netdev->type != LXC_NET_VETH)
                                continue;
                        if (write(netpipepair[1], netdev->name, IFNAMSIZ) != IFNAMSIZ) {
                                ERROR("Error writing veth name to container");
                                goto out_delete_net;
                        }
                }
                close(netpipepair[1]);
        }

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

        if (!cgroup_setup_limits(handler, true)) {
                ERROR("failed to setup the devices cgroup for '%s'", name);
                goto out_delete_net;
        }

        cgroup_disconnect();
        cgroups_connected = false;

        /* read tty fds allocated by child */
        if (recv_ttys_from_child(handler) < 0) {
                ERROR("failed to receive tty info from child");
                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_POST_CGROUP+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, LXC_SYNC_POST_CGROUP))
                return -1;

        if (detect_shared_rootfs())
                umount2(handler->conf->rootfs.mount, MNT_DETACH);

        if (handler->ops->post_start(handler, handler->data))
                goto out_abort;

        if (lxc_set_state(name, handler, RUNNING)) {
                ERROR("failed to set state to %s",
                              lxc_state2str(RUNNING));
                goto out_abort;
        }

        lxc_sync_fini(handler);

        return 0;

out_delete_net:
        if (cgroups_connected)
                cgroup_disconnect();
        if (handler->clone_flags & CLONE_NEWNET)
                lxc_delete_network(handler);
out_abort:
        lxc_abort(name, handler);
        lxc_sync_fini(handler);
        if (handler->pinfd >= 0) {
                close(handler->pinfd);
                handler->pinfd = -1;
        }

        return -1;
}

int get_netns_fd(int pid)
{
        char path[MAXPATHLEN];
        int ret, fd;

        ret = snprintf(path, MAXPATHLEN, "/proc/%d/ns/net", pid);
        if (ret < 0 || ret >= MAXPATHLEN) {
                WARN("Failed to pin netns file for pid %d", pid);
                return -1;
        }

        fd = open(path, O_RDONLY);
        if (fd < 0) {
                WARN("Failed to pin netns file %s for pid %d: %s",
                                path, pid, strerror(errno));
                return -1;
        }
        return fd;
}

int __lxc_start(const char *name, struct lxc_conf *conf,
                struct lxc_operations* ops, void *data, const char *lxcpath,
                bool backgrounded)
{
        struct lxc_handler *handler;
        int err = -1;
        int status;
        int netnsfd = -1;

        handler = lxc_init(name, conf, lxcpath);
        if (!handler) {
                ERROR("failed to initialize the container");
                return -1;
        }
        handler->ops = ops;
        handler->data = data;
        handler->backgrounded = backgrounded;

        if (must_drop_cap_sys_boot(handler->conf)) {
                #if HAVE_SYS_CAPABILITY_H
                DEBUG("Dropping cap_sys_boot");
                #else
                DEBUG("Can't drop cap_sys_boot as capabilities aren't supported");
                #endif
        } else {
                DEBUG("Not dropping cap_sys_boot or watching utmp");
                handler->conf->need_utmp_watch = 0;
        }

        if (!attach_block_device(handler->conf)) {
                ERROR("Failure attaching block device");
                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)) {
                        if (unshare(CLONE_NEWNS) < 0) {
                                ERROR("Error unsharing mounts");
                                goto out_fini_nonet;
                        }
                        remount_all_slave();
                        if (do_rootfs_setup(conf, name, lxcpath) < 0) {
                                ERROR("Error setting up rootfs mount as root before spawn");
                                goto out_fini_nonet;
                        }
                        INFO("Set up container rootfs as host root");
                }
        }

        err = lxc_spawn(handler);
        if (err) {
                ERROR("failed to spawn '%s'", name);
                goto out_detach_blockdev;
        }

        handler->conf->reboot = 0;

        netnsfd = get_netns_fd(handler->pid);

        err = lxc_poll(name, handler);
        if (err) {
                ERROR("mainloop exited with an error");
                if (netnsfd >= 0)
                        close(netnsfd);
                goto out_abort;
        }

        while (waitpid(handler->pid, &status, 0) < 0 && errno == EINTR)
                continue;

        /*
         * 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 halting");
                        break;
                case SIGHUP: /* reboot */
                        DEBUG("Container rebooting");
                        handler->conf->reboot = 1;
                        break;
                case SIGSYS: /* seccomp */
                        DEBUG("Container violated its seccomp policy");
                        break;
                default:
                        DEBUG("unknown exit status for init: %d", WTERMSIG(status));
                        break;
                }
        }

        DEBUG("Pushing physical nics back to host namespace");
        lxc_rename_phys_nics_on_shutdown(netnsfd, handler->conf);

        DEBUG("Tearing down virtual network devices used by container");
        lxc_delete_network(handler);

        if (netnsfd >= 0)
                close(netnsfd);

        if (handler->pinfd >= 0) {
                close(handler->pinfd);
                handler->pinfd = -1;
        }

        lxc_monitor_send_exit_code(name, status, handler->lxcpath);
        err =  lxc_error_set_and_log(handler->pid, status);
out_fini:
        lxc_delete_network(handler);

out_detach_blockdev:
        detach_block_device(handler->conf);

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

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("'%s' started 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_conf *conf,
              const char *lxcpath, bool backgrounded)
{
        struct start_args start_arg = {
                .argv = argv,
        };

        conf->need_utmp_watch = 1;
        return __lxc_start(name, conf, &start_ops, &start_arg, lxcpath, backgrounded);
}

static void lxc_destroy_container_on_signal(struct lxc_handler *handler,
                                            const char *name)
{
        char destroy[MAXPATHLEN];
        bool bret = true;
        int ret = 0;
        struct lxc_container *c;
        if (handler->conf->rootfs.path && handler->conf->rootfs.mount) {
                bret = do_destroy_container(handler->conf);
                if (!bret) {
                        ERROR("Error destroying rootfs for %s", name);
                        return;
                }
        }
        INFO("Destroyed rootfs for %s", name);

        ret = snprintf(destroy, MAXPATHLEN, "%s/%s", handler->lxcpath, name);
        if (ret < 0 || ret >= MAXPATHLEN) {
                ERROR("Error printing path for %s", name);
                ERROR("Error destroying directory for %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 (am_unpriv())
                ret = userns_exec_1(handler->conf, lxc_rmdir_onedev_wrapper, destroy);
        else
                ret = lxc_rmdir_onedev(destroy, NULL);

        if (ret < 0) {
                ERROR("Error destroying directory for %s", name);
                return;
        }
        INFO("Destroyed directory for %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_conf *conf) {
        if (am_unpriv()) {
                if (userns_exec_1(conf, bdev_destroy_wrapper, conf) < 0)
                        return false;
                return true;
        }
        return bdev_destroy(conf);
}