cgroups: remove pointless NULL checks

[mirror_lxc.git] / src / lxc / cgroups / cgfsng.c

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

/*
 * cgfs-ng.c: this is a new, simplified implementation of a filesystem
 * cgroup backend.  The original cgfs.c was designed to be as flexible
 * as possible.  It would try to find cgroup filesystems no matter where
 * or how you had them mounted, and deduce the most usable mount for
 * each controller.
 *
 * This new implementation assumes that cgroup filesystems are mounted
 * under /sys/fs/cgroup/clist where clist is either the controller, or
 * a comma-separated list of controllers.
 */

#ifndef _GNU_SOURCE
#define _GNU_SOURCE 1
#endif
#include <ctype.h>
#include <dirent.h>
#include <errno.h>
#include <grp.h>
#include <linux/kdev_t.h>
#include <linux/types.h>
#include <poll.h>
#include <signal.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/epoll.h>
#include <sys/types.h>
#include <unistd.h>

#include "af_unix.h"
#include "caps.h"
#include "cgroup.h"
#include "cgroup2_devices.h"
#include "cgroup_utils.h"
#include "commands.h"
#include "conf.h"
#include "config.h"
#include "log.h"
#include "macro.h"
#include "mainloop.h"
#include "memory_utils.h"
#include "storage/storage.h"
#include "utils.h"

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

#ifndef HAVE_STRLCAT
#include "include/strlcat.h"
#endif

lxc_log_define(cgfsng, cgroup);

/* Given a pointer to a null-terminated array of pointers, realloc to add one
 * entry, and point the new entry to NULL. Do not fail. Return the index to the
 * second-to-last entry - that is, the one which is now available for use
 * (keeping the list null-terminated).
 */
static int append_null_to_list(void ***list)
{
        int newentry = 0;

        if (*list)
                for (; (*list)[newentry]; newentry++)
                        ;

        *list = must_realloc(*list, (newentry + 2) * sizeof(void **));
        (*list)[newentry + 1] = NULL;
        return newentry;
}

/* Given a null-terminated array of strings, check whether @entry is one of the
 * strings.
 */
static bool string_in_list(char **list, const char *entry)
{
        if (!list)
                return false;

        for (int i = 0; list[i]; i++)
                if (strcmp(list[i], entry) == 0)
                        return true;

        return false;
}

/* Return a copy of @entry prepending "name=", i.e.  turn "systemd" into
 * "name=systemd". Do not fail.
 */
static char *cg_legacy_must_prefix_named(char *entry)
{
        size_t len;
        char *prefixed;

        len = strlen(entry);
        prefixed = must_realloc(NULL, len + 6);

        memcpy(prefixed, "name=", STRLITERALLEN("name="));
        memcpy(prefixed + STRLITERALLEN("name="), entry, len);
        prefixed[len + 5] = '\0';

        return prefixed;
}

/* Append an entry to the clist. Do not fail. @clist must be NULL the first time
 * we are called.
 *
 * We also handle named subsystems here. Any controller which is not a kernel
 * subsystem, we prefix "name=". Any which is both a kernel and named subsystem,
 * we refuse to use because we're not sure which we have here.
 * (TODO: We could work around this in some cases by just remounting to be
 * unambiguous, or by comparing mountpoint contents with current cgroup.)
 *
 * The last entry will always be NULL.
 */
static void must_append_controller(char **klist, char **nlist, char ***clist,
                                   char *entry)
{
        int newentry;
        char *copy;

        if (string_in_list(klist, entry) && string_in_list(nlist, entry)) {
                ERROR("Refusing to use ambiguous controller \"%s\"", entry);
                ERROR("It is both a named and kernel subsystem");
                return;
        }

        newentry = append_null_to_list((void ***)clist);

        if (strncmp(entry, "name=", 5) == 0)
                copy = must_copy_string(entry);
        else if (string_in_list(klist, entry))
                copy = must_copy_string(entry);
        else
                copy = cg_legacy_must_prefix_named(entry);

        (*clist)[newentry] = copy;
}

/* Given a handler's cgroup data, return the struct hierarchy for the controller
 * @c, or NULL if there is none.
 */
static struct hierarchy *get_hierarchy(struct cgroup_ops *ops, const char *controller)
{
        if (!ops->hierarchies)
                return log_trace_errno(NULL, errno, "There are no useable cgroup controllers");

        for (int i = 0; ops->hierarchies[i]; i++) {
                if (!controller) {
                        /* This is the empty unified hierarchy. */
                        if (ops->hierarchies[i]->controllers && !ops->hierarchies[i]->controllers[0])
                                return ops->hierarchies[i];

                        continue;
                }

                /*
                 * Handle controllers with significant implementation changes
                 * from cgroup to cgroup2.
                 */
                if (pure_unified_layout(ops)) {
                        if (strcmp(controller, "devices") == 0) {
                                if (ops->unified->bpf_device_controller)
                                        return ops->unified;

                                break;
                        } else if (strcmp(controller, "freezer") == 0) {
                                if (ops->unified->freezer_controller)
                                        return ops->unified;

                                break;
                        }
                }

                if (string_in_list(ops->hierarchies[i]->controllers, controller))
                        return ops->hierarchies[i];
        }

        if (controller)
                WARN("There is no useable %s controller", controller);
        else
                WARN("There is no empty unified cgroup hierarchy");

        return ret_set_errno(NULL, ENOENT);
}

/* Taken over modified from the kernel sources. */
#define NBITS 32 /* bits in uint32_t */
#define DIV_ROUND_UP(n, d) (((n) + (d)-1) / (d))
#define BITS_TO_LONGS(nr) DIV_ROUND_UP(nr, NBITS)

static void set_bit(unsigned bit, uint32_t *bitarr)
{
        bitarr[bit / NBITS] |= (1 << (bit % NBITS));
}

static void clear_bit(unsigned bit, uint32_t *bitarr)
{
        bitarr[bit / NBITS] &= ~(1 << (bit % NBITS));
}

static bool is_set(unsigned bit, uint32_t *bitarr)
{
        return (bitarr[bit / NBITS] & (1 << (bit % NBITS))) != 0;
}

/* Create cpumask from cpulist aka turn:
 *
 *      0,2-3
 *
 * into bit array
 *
 *      1 0 1 1
 */
static uint32_t *lxc_cpumask(char *buf, size_t nbits)
{
        __do_free uint32_t *bitarr = NULL;
        char *token;
        size_t arrlen;

        arrlen = BITS_TO_LONGS(nbits);
        bitarr = calloc(arrlen, sizeof(uint32_t));
        if (!bitarr)
                return ret_set_errno(NULL, ENOMEM);

        lxc_iterate_parts(token, buf, ",") {
                errno = 0;
                unsigned end, start;
                char *range;

                start = strtoul(token, NULL, 0);
                end = start;
                range = strchr(token, '-');
                if (range)
                        end = strtoul(range + 1, NULL, 0);

                if (!(start <= end))
                        return ret_set_errno(NULL, EINVAL);

                if (end >= nbits)
                        return ret_set_errno(NULL, EINVAL);

                while (start <= end)
                        set_bit(start++, bitarr);
        }

        return move_ptr(bitarr);
}

/* Turn cpumask into simple, comma-separated cpulist. */
static char *lxc_cpumask_to_cpulist(uint32_t *bitarr, size_t nbits)
{
        __do_free_string_list char **cpulist = NULL;
        char numstr[INTTYPE_TO_STRLEN(size_t)] = {0};
        int ret;

        for (size_t i = 0; i <= nbits; i++) {
                if (!is_set(i, bitarr))
                        continue;

                ret = snprintf(numstr, sizeof(numstr), "%zu", i);
                if (ret < 0 || (size_t)ret >= sizeof(numstr))
                        return NULL;

                ret = lxc_append_string(&cpulist, numstr);
                if (ret < 0)
                        return ret_set_errno(NULL, ENOMEM);
        }

        if (!cpulist)
                return ret_set_errno(NULL, ENOMEM);

        return lxc_string_join(",", (const char **)cpulist, false);
}

static ssize_t get_max_cpus(char *cpulist)
{
        char *c1, *c2;
        char *maxcpus = cpulist;
        size_t cpus = 0;

        c1 = strrchr(maxcpus, ',');
        if (c1)
                c1++;

        c2 = strrchr(maxcpus, '-');
        if (c2)
                c2++;

        if (!c1 && !c2)
                c1 = maxcpus;
        else if (c1 > c2)
                c2 = c1;
        else if (c1 < c2)
                c1 = c2;
        else if (!c1 && c2)
                c1 = c2;

        errno = 0;
        cpus = strtoul(c1, NULL, 0);
        if (errno != 0)
                return -1;

        return cpus;
}

#define __ISOL_CPUS "/sys/devices/system/cpu/isolated"
#define __OFFLINE_CPUS "/sys/devices/system/cpu/offline"
static bool cg_legacy_filter_and_set_cpus(const char *parent_cgroup,
                                          char *child_cgroup, bool am_initialized)
{
        __do_free char *cpulist = NULL, *fpath = NULL, *isolcpus = NULL,
                       *offlinecpus = NULL, *posscpus = NULL;
        __do_free uint32_t *isolmask = NULL, *offlinemask = NULL,
                           *possmask = NULL;
        int ret;
        ssize_t i;
        ssize_t maxisol = 0, maxoffline = 0, maxposs = 0;
        bool flipped_bit = false;

        fpath = must_make_path(parent_cgroup, "cpuset.cpus", NULL);
        posscpus = read_file_at(-EBADF, fpath);
        if (!posscpus)
                return log_error_errno(false, errno, "Failed to read file \"%s\"", fpath);

        /* Get maximum number of cpus found in possible cpuset. */
        maxposs = get_max_cpus(posscpus);
        if (maxposs < 0 || maxposs >= INT_MAX - 1)
                return false;

        if (file_exists(__ISOL_CPUS)) {
                isolcpus = read_file_at(-EBADF, __ISOL_CPUS);
                if (!isolcpus)
                        return log_error_errno(false, errno, "Failed to read file \"%s\"", __ISOL_CPUS);

                if (isdigit(isolcpus[0])) {
                        /* Get maximum number of cpus found in isolated cpuset. */
                        maxisol = get_max_cpus(isolcpus);
                        if (maxisol < 0 || maxisol >= INT_MAX - 1)
                                return false;
                }

                if (maxposs < maxisol)
                        maxposs = maxisol;
                maxposs++;
        } else {
                TRACE("The path \""__ISOL_CPUS"\" to read isolated cpus from does not exist");
        }

        if (file_exists(__OFFLINE_CPUS)) {
                offlinecpus = read_file_at(-EBADF, __OFFLINE_CPUS);
                if (!offlinecpus)
                        return log_error_errno(false, errno, "Failed to read file \"%s\"", __OFFLINE_CPUS);

                if (isdigit(offlinecpus[0])) {
                        /* Get maximum number of cpus found in offline cpuset. */
                        maxoffline = get_max_cpus(offlinecpus);
                        if (maxoffline < 0 || maxoffline >= INT_MAX - 1)
                                return false;
                }

                if (maxposs < maxoffline)
                        maxposs = maxoffline;
                maxposs++;
        } else {
                TRACE("The path \""__OFFLINE_CPUS"\" to read offline cpus from does not exist");
        }

        if ((maxisol == 0) && (maxoffline == 0)) {
                cpulist = move_ptr(posscpus);
                goto copy_parent;
        }

        possmask = lxc_cpumask(posscpus, maxposs);
        if (!possmask)
                return log_error_errno(false, errno, "Failed to create cpumask for possible cpus");

        if (maxisol > 0) {
                isolmask = lxc_cpumask(isolcpus, maxposs);
                if (!isolmask)
                        return log_error_errno(false, errno, "Failed to create cpumask for isolated cpus");
        }

        if (maxoffline > 0) {
                offlinemask = lxc_cpumask(offlinecpus, maxposs);
                if (!offlinemask)
                        return log_error_errno(false, errno, "Failed to create cpumask for offline cpus");
        }

        for (i = 0; i <= maxposs; i++) {
                if ((isolmask && !is_set(i, isolmask)) ||
                    (offlinemask && !is_set(i, offlinemask)) ||
                    !is_set(i, possmask))
                        continue;

                flipped_bit = true;
                clear_bit(i, possmask);
        }

        if (!flipped_bit) {
                cpulist = lxc_cpumask_to_cpulist(possmask, maxposs);
                TRACE("No isolated or offline cpus present in cpuset");
        } else {
                cpulist = move_ptr(posscpus);
                TRACE("Removed isolated or offline cpus from cpuset");
        }
        if (!cpulist)
                return log_error_errno(false, errno, "Failed to create cpu list");

copy_parent:
        if (!am_initialized) {
                ret = lxc_write_openat(child_cgroup, "cpuset.cpus", cpulist, strlen(cpulist));
                if (ret < 0)
                        return log_error_errno(false,
                                               errno, "Failed to write cpu list to \"%s/cpuset.cpus\"",
                                               child_cgroup);

                TRACE("Copied cpu settings of parent cgroup");
        }

        return true;
}

/* Copy contents of parent(@path)/@file to @path/@file */
static bool copy_parent_file(const char *parent_cgroup,
                             const char *child_cgroup, const char *file)
{
        __do_free char *parent_file = NULL, *value = NULL;
        int len = 0;
        int ret;

        parent_file = must_make_path(parent_cgroup, file, NULL);
        len = lxc_read_from_file(parent_file, NULL, 0);
        if (len <= 0)
                return log_error_errno(false, errno, "Failed to determine buffer size");

        value = must_realloc(NULL, len + 1);
        value[len] = '\0';
        ret = lxc_read_from_file(parent_file, value, len);
        if (ret != len)
                return log_error_errno(false, errno, "Failed to read from parent file \"%s\"", parent_file);

        ret = lxc_write_openat(child_cgroup, file, value, len);
        if (ret < 0 && errno != EACCES)
                return log_error_errno(false, errno, "Failed to write \"%s\" to file \"%s/%s\"",
                                       value, child_cgroup, file);
        return true;
}

static inline bool is_unified_hierarchy(const struct hierarchy *h)
{
        return h->version == CGROUP2_SUPER_MAGIC;
}

/*
 * Initialize the cpuset hierarchy in first directory of @cgroup_leaf and set
 * cgroup.clone_children so that children inherit settings. Since the
 * h->base_path is populated by init or ourselves, we know it is already
 * initialized.
 *
 * returns -1 on error, 0 when we didn't created a cgroup, 1 if we created a
 * cgroup.
 */
static int cg_legacy_handle_cpuset_hierarchy(struct hierarchy *h,
                                             const char *cgroup_leaf)
{
        __do_free char *parent_cgroup = NULL, *child_cgroup = NULL, *dup = NULL;
        __do_close int cgroup_fd = -EBADF;
        int fret = -1;
        int ret;
        char v;
        char *leaf, *slash;

        if (is_unified_hierarchy(h))
                return 0;

        if (!string_in_list(h->controllers, "cpuset"))
                return 0;

        if (!cgroup_leaf)
                return ret_set_errno(-1, EINVAL);

        dup = strdup(cgroup_leaf);
        if (!dup)
                return ret_set_errno(-1, ENOMEM);

        parent_cgroup = must_make_path(h->mountpoint, h->container_base_path, NULL);

        leaf = dup;
        leaf += strspn(leaf, "/");
        slash = strchr(leaf, '/');
        if (slash)
                *slash = '\0';
        child_cgroup = must_make_path(parent_cgroup, leaf, NULL);
        if (slash)
                *slash = '/';

        fret = 1;
        ret = mkdir(child_cgroup, 0755);
        if (ret < 0) {
                if (errno != EEXIST)
                        return log_error_errno(-1, errno, "Failed to create directory \"%s\"", child_cgroup);

                fret = 0;
        }

        cgroup_fd = lxc_open_dirfd(child_cgroup);
        if (cgroup_fd < 0)
                return -1;

        ret = lxc_readat(cgroup_fd, "cgroup.clone_children", &v, 1);
        if (ret < 0)
                return log_error_errno(-1, errno, "Failed to read file \"%s/cgroup.clone_children\"", child_cgroup);

        /* Make sure any isolated cpus are removed from cpuset.cpus. */
        if (!cg_legacy_filter_and_set_cpus(parent_cgroup, child_cgroup, v == '1'))
                return log_error_errno(-1, errno, "Failed to remove isolated cpus");

        /* Already set for us by someone else. */
        if (v == '1')
                TRACE("\"cgroup.clone_children\" was already set to \"1\"");

        /* copy parent's settings */
        if (!copy_parent_file(parent_cgroup, child_cgroup, "cpuset.mems"))
                return log_error_errno(-1, errno, "Failed to copy \"cpuset.mems\" settings");

        /* Set clone_children so children inherit our settings */
        ret = lxc_writeat(cgroup_fd, "cgroup.clone_children", "1", 1);
        if (ret < 0)
                return log_error_errno(-1, errno, "Failed to write 1 to \"%s/cgroup.clone_children\"", child_cgroup);

        return fret;
}

/* Given two null-terminated lists of strings, return true if any string is in
 * both.
 */
static bool controller_lists_intersect(char **l1, char **l2)
{
        if (!l1 || !l2)
                return false;

        for (int i = 0; l1[i]; i++)
                if (string_in_list(l2, l1[i]))
                        return true;

        return false;
}

/* For a null-terminated list of controllers @clist, return true if any of those
 * controllers is already listed the null-terminated list of hierarchies @hlist.
 * Realistically, if one is present, all must be present.
 */
static bool controller_list_is_dup(struct hierarchy **hlist, char **clist)
{
        if (!hlist)
                return false;

        for (int i = 0; hlist[i]; i++)
                if (controller_lists_intersect(hlist[i]->controllers, clist))
                        return true;

        return false;
}

/* Return true if the controller @entry is found in the null-terminated list of
 * hierarchies @hlist.
 */
static bool controller_found(struct hierarchy **hlist, char *entry)
{
        if (!hlist)
                return false;

        for (int i = 0; hlist[i]; i++)
                if (string_in_list(hlist[i]->controllers, entry))
                        return true;

        return false;
}

/* Return true if all of the controllers which we require have been found.  The
 * required list is  freezer and anything in lxc.cgroup.use.
 */
static bool all_controllers_found(struct cgroup_ops *ops)
{
        struct hierarchy **hlist;

        if (!ops->cgroup_use)
                return true;

        hlist = ops->hierarchies;
        for (char **cur = ops->cgroup_use; cur && *cur; cur++)
                if (!controller_found(hlist, *cur))
                        return log_error(false, "No %s controller mountpoint found", *cur);

        return true;
}

/* Get the controllers from a mountinfo line There are other ways we could get
 * this info. For lxcfs, field 3 is /cgroup/controller-list. For cgroupfs, we
 * could parse the mount options. But we simply assume that the mountpoint must
 * be /sys/fs/cgroup/controller-list
 */
static char **cg_hybrid_get_controllers(char **klist, char **nlist, char *line,
                                        int type)
{
        /* The fourth field is /sys/fs/cgroup/comma-delimited-controller-list
         * for legacy hierarchies.
         */
        __do_free_string_list char **aret = NULL;
        int i;
        char *p2, *tok;
        char *p = line, *sep = ",";

        for (i = 0; i < 4; i++) {
                p = strchr(p, ' ');
                if (!p)
                        return NULL;
                p++;
        }

        /* Note, if we change how mountinfo works, then our caller will need to
         * verify /sys/fs/cgroup/ in this field.
         */
        if (strncmp(p, DEFAULT_CGROUP_MOUNTPOINT "/", 15) != 0)
                return log_warn(NULL, "Found hierarchy not under " DEFAULT_CGROUP_MOUNTPOINT ": \"%s\"", p);

        p += 15;
        p2 = strchr(p, ' ');
        if (!p2)
                return log_error(NULL, "Corrupt mountinfo");
        *p2 = '\0';

        if (type == CGROUP_SUPER_MAGIC) {
                __do_free char *dup = NULL;

                /* strdup() here for v1 hierarchies. Otherwise
                 * lxc_iterate_parts() will destroy mountpoints such as
                 * "/sys/fs/cgroup/cpu,cpuacct".
                 */
                dup = must_copy_string(p);
                if (!dup)
                        return NULL;

                lxc_iterate_parts(tok, dup, sep)
                        must_append_controller(klist, nlist, &aret, tok);
        }
        *p2 = ' ';

        return move_ptr(aret);
}

static char **cg_unified_make_empty_controller(void)
{
        __do_free_string_list char **aret = NULL;
        int newentry;

        newentry = append_null_to_list((void ***)&aret);
        aret[newentry] = NULL;
        return move_ptr(aret);
}

static char **cg_unified_get_controllers(int dfd, const char *file)
{
        __do_free char *buf = NULL;
        __do_free_string_list char **aret = NULL;
        char *sep = " \t\n";
        char *tok;

        buf = read_file_at(dfd, file);
        if (!buf)
                return NULL;

        lxc_iterate_parts(tok, buf, sep) {
                int newentry;
                char *copy;

                newentry = append_null_to_list((void ***)&aret);
                copy = must_copy_string(tok);
                aret[newentry] = copy;
        }

        return move_ptr(aret);
}

static struct hierarchy *add_hierarchy(struct hierarchy ***h, char **clist, char *mountpoint,
                                       char *container_base_path, int type)
{
        struct hierarchy *new;
        int newentry;

        new = zalloc(sizeof(*new));
        if (!new)
                return ret_set_errno(NULL, ENOMEM);
        new->controllers = clist;
        new->mountpoint = mountpoint;
        new->container_base_path = container_base_path;
        new->version = type;
        new->cgfd_con = -EBADF;
        new->cgfd_limit = -EBADF;
        new->cgfd_mon = -EBADF;

        newentry = append_null_to_list((void ***)h);
        (*h)[newentry] = new;
        return new;
}

/* Get a copy of the mountpoint from @line, which is a line from
 * /proc/self/mountinfo.
 */
static char *cg_hybrid_get_mountpoint(char *line)
{
        char *p = line, *sret = NULL;
        size_t len;
        char *p2;

        for (int i = 0; i < 4; i++) {
                p = strchr(p, ' ');
                if (!p)
                        return NULL;
                p++;
        }

        if (strncmp(p, DEFAULT_CGROUP_MOUNTPOINT "/", 15) != 0)
                return NULL;

        p2 = strchr(p + 15, ' ');
        if (!p2)
                return NULL;
        *p2 = '\0';

        len = strlen(p);
        sret = must_realloc(NULL, len + 1);
        memcpy(sret, p, len);
        sret[len] = '\0';

        return sret;
}

/* Given a multi-line string, return a null-terminated copy of the current line. */
static char *copy_to_eol(char *p)
{
        char *p2, *sret;
        size_t len;

        p2 = strchr(p, '\n');
        if (!p2)
                return NULL;

        len = p2 - p;
        sret = must_realloc(NULL, len + 1);
        memcpy(sret, p, len);
        sret[len] = '\0';

        return sret;
}

/* cgline: pointer to character after the first ':' in a line in a \n-terminated
 * /proc/self/cgroup file. Check whether controller c is present.
 */
static bool controller_in_clist(char *cgline, char *c)
{
        __do_free char *tmp = NULL;
        char *tok, *eol;
        size_t len;

        eol = strchr(cgline, ':');
        if (!eol)
                return false;

        len = eol - cgline;
        tmp = must_realloc(NULL, len + 1);
        memcpy(tmp, cgline, len);
        tmp[len] = '\0';

        lxc_iterate_parts(tok, tmp, ",")
                if (strcmp(tok, c) == 0)
                        return true;

        return false;
}

/* @basecginfo is a copy of /proc/$$/cgroup. Return the current cgroup for
 * @controller.
 */
static char *cg_hybrid_get_current_cgroup(char *basecginfo, char *controller,
                                          int type)
{
        char *p = basecginfo;

        for (;;) {
                bool is_cgv2_base_cgroup = false;

                /* cgroup v2 entry in "/proc/<pid>/cgroup": "0::/some/path" */
                if ((type == CGROUP2_SUPER_MAGIC) && (*p == '0'))
                        is_cgv2_base_cgroup = true;

                p = strchr(p, ':');
                if (!p)
                        return NULL;
                p++;

                if (is_cgv2_base_cgroup || (controller && controller_in_clist(p, controller))) {
                        p = strchr(p, ':');
                        if (!p)
                                return NULL;
                        p++;
                        return copy_to_eol(p);
                }

                p = strchr(p, '\n');
                if (!p)
                        return NULL;
                p++;
        }
}

static void must_append_string(char ***list, char *entry)
{
        int newentry;
        char *copy;

        newentry = append_null_to_list((void ***)list);
        copy = must_copy_string(entry);
        (*list)[newentry] = copy;
}

static int get_existing_subsystems(char ***klist, char ***nlist)
{
        __do_free char *line = NULL;
        __do_fclose FILE *f = NULL;
        size_t len = 0;

        f = fopen("/proc/self/cgroup", "re");
        if (!f)
                return -1;

        while (getline(&line, &len, f) != -1) {
                char *p, *p2, *tok;
                p = strchr(line, ':');
                if (!p)
                        continue;
                p++;
                p2 = strchr(p, ':');
                if (!p2)
                        continue;
                *p2 = '\0';

                /* If the kernel has cgroup v2 support, then /proc/self/cgroup
                 * contains an entry of the form:
                 *
                 *      0::/some/path
                 *
                 * In this case we use "cgroup2" as controller name.
                 */
                if ((p2 - p) == 0) {
                        must_append_string(klist, "cgroup2");
                        continue;
                }

                lxc_iterate_parts(tok, p, ",") {
                        if (strncmp(tok, "name=", 5) == 0)
                                must_append_string(nlist, tok);
                        else
                                must_append_string(klist, tok);
                }
        }

        return 0;
}

static char *trim(char *s)
{
        size_t len;

        len = strlen(s);
        while ((len > 1) && (s[len - 1] == '\n'))
                s[--len] = '\0';

        return s;
}

static void lxc_cgfsng_print_hierarchies(struct cgroup_ops *ops)
{
        int i;
        struct hierarchy **it;

        if (!ops->hierarchies) {
                TRACE("  No hierarchies found");
                return;
        }

        TRACE("  Hierarchies:");
        for (i = 0, it = ops->hierarchies; it && *it; it++, i++) {
                int j;
                char **cit;

                TRACE("  %d: base_cgroup: %s", i, (*it)->container_base_path ? (*it)->container_base_path : "(null)");
                TRACE("      mountpoint:  %s", (*it)->mountpoint ? (*it)->mountpoint : "(null)");
                TRACE("      controllers:");
                for (j = 0, cit = (*it)->controllers; cit && *cit; cit++, j++)
                        TRACE("      %d: %s", j, *cit);
        }
}

static void lxc_cgfsng_print_basecg_debuginfo(char *basecginfo, char **klist,
                                              char **nlist)
{
        int k;
        char **it;

        TRACE("basecginfo is:");
        TRACE("%s", basecginfo);

        for (k = 0, it = klist; it && *it; it++, k++)
                TRACE("kernel subsystem %d: %s", k, *it);

        for (k = 0, it = nlist; it && *it; it++, k++)
                TRACE("named subsystem %d: %s", k, *it);
}

static int cgroup_tree_remove(struct hierarchy **hierarchies, const char *container_cgroup)
{
        if (!container_cgroup || !hierarchies)
                return 0;

        for (int i = 0; hierarchies[i]; i++) {
                struct hierarchy *h = hierarchies[i];
                int ret;

                if (!h->container_limit_path)
                        continue;

                ret = lxc_rm_rf(h->container_limit_path);
                if (ret < 0)
                        WARN("Failed to destroy \"%s\"", h->container_limit_path);

                if (h->container_limit_path != h->container_full_path)
                        free_disarm(h->container_limit_path);
                free_disarm(h->container_full_path);
        }

        return 0;
}

struct generic_userns_exec_data {
        struct hierarchy **hierarchies;
        const char *container_cgroup;
        struct lxc_conf *conf;
        uid_t origuid; /* target uid in parent namespace */
        char *path;
};

static int cgroup_tree_remove_wrapper(void *data)
{
        struct generic_userns_exec_data *arg = data;
        uid_t nsuid = (arg->conf->root_nsuid_map != NULL) ? 0 : arg->conf->init_uid;
        gid_t nsgid = (arg->conf->root_nsgid_map != NULL) ? 0 : arg->conf->init_gid;
        int ret;

        if (!lxc_setgroups(0, NULL) && errno != EPERM)
                return log_error_errno(-1, errno, "Failed to setgroups(0, NULL)");

        ret = setresgid(nsgid, nsgid, nsgid);
        if (ret < 0)
                return log_error_errno(-1, errno, "Failed to setresgid(%d, %d, %d)",
                                       (int)nsgid, (int)nsgid, (int)nsgid);

        ret = setresuid(nsuid, nsuid, nsuid);
        if (ret < 0)
                return log_error_errno(-1, errno, "Failed to setresuid(%d, %d, %d)",
                                       (int)nsuid, (int)nsuid, (int)nsuid);

        return cgroup_tree_remove(arg->hierarchies, arg->container_cgroup);
}

__cgfsng_ops static void cgfsng_payload_destroy(struct cgroup_ops *ops,
                                                struct lxc_handler *handler)
{
        int ret;

        if (!ops) {
                ERROR("Called with uninitialized cgroup operations");
                return;
        }

        if (!ops->hierarchies)
                return;

        if (!handler) {
                ERROR("Called with uninitialized handler");
                return;
        }

        if (!handler->conf) {
                ERROR("Called with uninitialized conf");
                return;
        }

#ifdef HAVE_STRUCT_BPF_CGROUP_DEV_CTX
        ret = bpf_program_cgroup_detach(handler->cgroup_ops->cgroup2_devices);
        if (ret < 0)
                WARN("Failed to detach bpf program from cgroup");
#endif

        if (!lxc_list_empty(&handler->conf->id_map)) {
                struct generic_userns_exec_data wrap = {
                        .conf                   = handler->conf,
                        .container_cgroup       = ops->container_cgroup,
                        .hierarchies            = ops->hierarchies,
                        .origuid                = 0,
                };
                ret = userns_exec_1(handler->conf, cgroup_tree_remove_wrapper,
                                    &wrap, "cgroup_tree_remove_wrapper");
        } else {
                ret = cgroup_tree_remove(ops->hierarchies, ops->container_cgroup);
        }
        if (ret < 0)
                SYSWARN("Failed to destroy cgroups");
}

__cgfsng_ops static void cgfsng_monitor_destroy(struct cgroup_ops *ops,
                                                struct lxc_handler *handler)
{
        int len;
        char pidstr[INTTYPE_TO_STRLEN(pid_t)];
        const struct lxc_conf *conf;

        if (!ops) {
                ERROR("Called with uninitialized cgroup operations");
                return;
        }

        if (!ops->hierarchies)
                return;

        if (!handler) {
                ERROR("Called with uninitialized handler");
                return;
        }

        if (!handler->conf) {
                ERROR("Called with uninitialized conf");
                return;
        }
        conf = handler->conf;

        len = snprintf(pidstr, sizeof(pidstr), "%d", handler->monitor_pid);
        if (len < 0 || (size_t)len >= sizeof(pidstr))
                return;

        for (int i = 0; ops->hierarchies[i]; i++) {
                __do_free char *pivot_path = NULL;
                struct hierarchy *h = ops->hierarchies[i];
                size_t offset;
                int ret;

                if (!h->monitor_full_path)
                        continue;

                /* Monitor might have died before we entered the cgroup. */
                if (handler->monitor_pid <= 0) {
                        WARN("No valid monitor process found while destroying cgroups");
                        goto try_lxc_rm_rf;
                }

                if (conf->cgroup_meta.monitor_pivot_dir)
                        pivot_path = must_make_path(h->mountpoint, h->container_base_path,
                                                    conf->cgroup_meta.monitor_pivot_dir, CGROUP_PIVOT, NULL);
                else if (conf->cgroup_meta.monitor_dir)
                        pivot_path = must_make_path(h->mountpoint, h->container_base_path,
                                                    conf->cgroup_meta.monitor_dir, CGROUP_PIVOT, NULL);
                else if (conf->cgroup_meta.dir)
                        pivot_path = must_make_path(h->mountpoint, h->container_base_path,
                                                    conf->cgroup_meta.dir, CGROUP_PIVOT, NULL);
                else
                        pivot_path = must_make_path(h->mountpoint, h->container_base_path,
                                                    CGROUP_PIVOT, NULL);

                offset = strlen(h->mountpoint) + strlen(h->container_base_path);

                if (cg_legacy_handle_cpuset_hierarchy(h, pivot_path + offset))
                        SYSWARN("Failed to initialize cpuset %s/" CGROUP_PIVOT, pivot_path);

                ret = mkdir_p(pivot_path, 0755);
                if (ret < 0 && errno != EEXIST) {
                        ERROR("Failed to create %s", pivot_path);
                        goto try_lxc_rm_rf;
                }

                ret = lxc_write_openat(pivot_path, "cgroup.procs", pidstr, len);
                if (ret != 0) {
                        SYSWARN("Failed to move monitor %s to \"%s\"", pidstr, pivot_path);
                        continue;
                }

try_lxc_rm_rf:
                ret = lxc_rm_rf(h->monitor_full_path);
                if (ret < 0)
                        WARN("Failed to destroy \"%s\"", h->monitor_full_path);
        }
}

static int mkdir_eexist_on_last(const char *dir, mode_t mode)
{
        const char *tmp = dir;
        const char *orig = dir;
        size_t orig_len;

        orig_len = strlen(dir);
        do {
                __do_free char *makeme = NULL;
                int ret;
                size_t cur_len;

                dir = tmp + strspn(tmp, "/");
                tmp = dir + strcspn(dir, "/");

                cur_len = dir - orig;
                makeme = strndup(orig, cur_len);
                if (!makeme)
                        return ret_set_errno(-1, ENOMEM);

                ret = mkdir(makeme, mode);
                if (ret < 0 && ((errno != EEXIST) || (orig_len == cur_len)))
                        return log_warn_errno(-1, errno, "Failed to create directory \"%s\"", makeme);
        } while (tmp != dir);

        return 0;
}

static bool cgroup_tree_create(struct cgroup_ops *ops, struct lxc_conf *conf,
                               struct hierarchy *h, const char *cgroup_tree,
                               const char *cgroup_leaf, bool payload,
                               const char *cgroup_limit_dir)
{
        __do_free char *path = NULL, *limit_path = NULL;
        int ret, ret_cpuset;

        path = must_make_path(h->mountpoint, h->container_base_path, cgroup_leaf, NULL);
        if (dir_exists(path))
                return log_warn_errno(false, errno, "The %s cgroup already existed", path);

        ret_cpuset = cg_legacy_handle_cpuset_hierarchy(h, cgroup_leaf);
        if (ret_cpuset < 0)
                return log_error_errno(false, errno, "Failed to handle legacy cpuset controller");

        if (payload && cgroup_limit_dir) {
                /* with isolation both parts need to not already exist */
                limit_path = must_make_path(h->mountpoint,
                                            h->container_base_path,
                                            cgroup_limit_dir, NULL);

                ret = mkdir_eexist_on_last(limit_path, 0755);
                if (ret < 0)
                        return log_debug_errno(false,
                                              errno, "Failed to create %s limiting cgroup",
                                              limit_path);

                h->cgfd_limit = lxc_open_dirfd(limit_path);
                if (h->cgfd_limit < 0)
                        return log_error_errno(false, errno,
                                               "Failed to open %s", path);
                h->container_limit_path = move_ptr(limit_path);

                /*
                 * With isolation the devices legacy cgroup needs to be
                 * iinitialized early, as it typically contains an 'a' (all)
                 * line, which is not possible once a subdirectory has been
                 * created.
                 */
                if (string_in_list(h->controllers, "devices") &&
                    !ops->setup_limits_legacy(ops, conf, true))
                        return log_error(false, "Failed to setup legacy device limits");
        }

        ret = mkdir_eexist_on_last(path, 0755);
        if (ret < 0) {
                /*
                 * This is the cpuset controller and
                 * cg_legacy_handle_cpuset_hierarchy() has created our target
                 * directory for us to ensure correct initialization.
                 */
                if (ret_cpuset != 1 || cgroup_tree)
                        return log_debug_errno(false, errno, "Failed to create %s cgroup", path);
        }

        if (payload) {
                h->cgfd_con = lxc_open_dirfd(path);
                if (h->cgfd_con < 0)
                        return log_error_errno(false, errno, "Failed to open %s", path);
                h->container_full_path = move_ptr(path);
                if (h->cgfd_limit < 0)
                        h->cgfd_limit = h->cgfd_con;
                if (!h->container_limit_path)
                        h->container_limit_path = h->container_full_path;
        } else {
                h->cgfd_mon = lxc_open_dirfd(path);
                if (h->cgfd_mon < 0)
                        return log_error_errno(false, errno, "Failed to open %s", path);
                h->monitor_full_path = move_ptr(path);
        }

        return true;
}

static void cgroup_tree_leaf_remove(struct hierarchy *h, bool payload)
{
        __do_free char *full_path = NULL, *__limit_path = NULL;
        char *limit_path = NULL;

        if (payload) {
                __lxc_unused __do_close int fd = move_fd(h->cgfd_con);
                full_path = move_ptr(h->container_full_path);
                limit_path = move_ptr(h->container_limit_path);
                if (limit_path != full_path)
                        __limit_path = limit_path;
        } else {
                __lxc_unused __do_close int fd = move_fd(h->cgfd_mon);
                full_path = move_ptr(h->monitor_full_path);
        }

        if (full_path && rmdir(full_path))
                SYSWARN("Failed to rmdir(\"%s\") cgroup", full_path);
        if (limit_path && rmdir(limit_path))
                SYSWARN("Failed to rmdir(\"%s\") cgroup", limit_path);
}

/*
 * Check we have no lxc.cgroup.dir, and that lxc.cgroup.dir.limit_prefix is a
 * proper prefix directory of lxc.cgroup.dir.payload.
 *
 * Returns the prefix length if it is set, otherwise zero on success.
 */
static bool check_cgroup_dir_config(struct lxc_conf *conf)
{
        const char *monitor_dir = conf->cgroup_meta.monitor_dir,
                   *container_dir = conf->cgroup_meta.container_dir,
                   *namespace_dir = conf->cgroup_meta.namespace_dir;

        /* none of the new options are set, all is fine */
        if (!monitor_dir && !container_dir && !namespace_dir)
                return true;

        /* some are set, make sure lxc.cgroup.dir is not also set*/
        if (conf->cgroup_meta.dir)
                return log_error_errno(false, EINVAL,
                        "lxc.cgroup.dir conflicts with lxc.cgroup.dir.payload/monitor");

        /* make sure both monitor and payload are set */
        if (!monitor_dir || !container_dir)
                return log_error_errno(false, EINVAL,
                        "lxc.cgroup.dir.payload and lxc.cgroup.dir.monitor must both be set");

        /* namespace_dir may be empty */
        return true;
}

__cgfsng_ops static bool cgfsng_monitor_create(struct cgroup_ops *ops, struct lxc_handler *handler)
{
        __do_free char *monitor_cgroup = NULL, *__cgroup_tree = NULL;
        const char *cgroup_tree;
        int idx = 0;
        int i;
        size_t len;
        char *suffix = NULL;
        struct lxc_conf *conf;

        if (!ops)
                return ret_set_errno(false, ENOENT);

        if (!ops->hierarchies)
                return true;

        if (ops->monitor_cgroup)
                return ret_set_errno(false, EEXIST);

        if (!handler || !handler->conf)
                return ret_set_errno(false, EINVAL);

        conf = handler->conf;

        if (!check_cgroup_dir_config(conf))
                return false;

        if (conf->cgroup_meta.monitor_dir) {
                cgroup_tree = NULL;
                monitor_cgroup = strdup(conf->cgroup_meta.monitor_dir);
        } else if (conf->cgroup_meta.dir) {
                cgroup_tree = conf->cgroup_meta.dir;
                monitor_cgroup = must_concat(&len, conf->cgroup_meta.dir, "/",
                                             DEFAULT_MONITOR_CGROUP_PREFIX,
                                             handler->name,
                                             CGROUP_CREATE_RETRY, NULL);
        } else if (ops->cgroup_pattern) {
                __cgroup_tree = lxc_string_replace("%n", handler->name, ops->cgroup_pattern);
                if (!__cgroup_tree)
                        return ret_set_errno(false, ENOMEM);

                cgroup_tree = __cgroup_tree;
                monitor_cgroup = must_concat(&len, cgroup_tree, "/",
                                             DEFAULT_MONITOR_CGROUP,
                                             CGROUP_CREATE_RETRY, NULL);
        } else {
                cgroup_tree = NULL;
                monitor_cgroup = must_concat(&len, DEFAULT_MONITOR_CGROUP_PREFIX,
                                             handler->name,
                                             CGROUP_CREATE_RETRY, NULL);
        }
        if (!monitor_cgroup)
                return ret_set_errno(false, ENOMEM);

        if (!conf->cgroup_meta.monitor_dir) {
                suffix = monitor_cgroup + len - CGROUP_CREATE_RETRY_LEN;
                *suffix = '\0';
        }
        do {
                if (idx && suffix)
                        sprintf(suffix, "-%d", idx);

                for (i = 0; ops->hierarchies[i]; i++) {
                        if (cgroup_tree_create(ops, handler->conf,
                                               ops->hierarchies[i], cgroup_tree,
                                               monitor_cgroup, false, NULL))
                                continue;

                        DEBUG("Failed to create cgroup \"%s\"", ops->hierarchies[i]->monitor_full_path ?: "(null)");
                        for (int j = 0; j < i; j++)
                                cgroup_tree_leaf_remove(ops->hierarchies[j], false);

                        idx++;
                        break;
                }
        } while (ops->hierarchies[i] && idx > 0 && idx < 1000 && suffix);

        if (idx == 1000 || (!suffix && idx != 0))
                return log_error_errno(false, ERANGE, "Failed to create monitor cgroup");

        ops->monitor_cgroup = move_ptr(monitor_cgroup);
        return log_info(true, "The monitor process uses \"%s\" as cgroup", ops->monitor_cgroup);
}

/*
 * Try to create the same cgroup in all hierarchies. Start with cgroup_pattern;
 * next cgroup_pattern-1, -2, ..., -999.
 */
__cgfsng_ops static bool cgfsng_payload_create(struct cgroup_ops *ops, struct lxc_handler *handler)
{
        __do_free char *container_cgroup = NULL,
                       *__cgroup_tree = NULL,
                       *limiting_cgroup = NULL;
        const char *cgroup_tree;
        int idx = 0;
        int i;
        size_t len;
        char *suffix = NULL;
        struct lxc_conf *conf;

        if (!ops)
                return ret_set_errno(false, ENOENT);

        if (!ops->hierarchies)
                return true;

        if (ops->container_cgroup)
                return ret_set_errno(false, EEXIST);

        if (!handler || !handler->conf)
                return ret_set_errno(false, EINVAL);

        conf = handler->conf;

        if (!check_cgroup_dir_config(conf))
                return false;

        if (conf->cgroup_meta.container_dir) {
                cgroup_tree = NULL;

                limiting_cgroup = strdup(conf->cgroup_meta.container_dir);
                if (!limiting_cgroup)
                        return ret_set_errno(false, ENOMEM);

                if (conf->cgroup_meta.namespace_dir) {
                        container_cgroup = must_make_path(limiting_cgroup,
                                                          conf->cgroup_meta.namespace_dir,
                                                          NULL);
                } else {
                        /* explicit paths but without isolation */
                        container_cgroup = move_ptr(limiting_cgroup);
                }
        } else if (conf->cgroup_meta.dir) {
                cgroup_tree = conf->cgroup_meta.dir;
                container_cgroup = must_concat(&len, cgroup_tree, "/",
                                             DEFAULT_PAYLOAD_CGROUP_PREFIX,
                                             handler->name,
                                             CGROUP_CREATE_RETRY, NULL);
        } else if (ops->cgroup_pattern) {
                __cgroup_tree = lxc_string_replace("%n", handler->name, ops->cgroup_pattern);
                if (!__cgroup_tree)
                        return ret_set_errno(false, ENOMEM);

                cgroup_tree = __cgroup_tree;
                container_cgroup = must_concat(&len, cgroup_tree, "/",
                                               DEFAULT_PAYLOAD_CGROUP,
                                               CGROUP_CREATE_RETRY, NULL);
        } else {
                cgroup_tree = NULL;
                container_cgroup = must_concat(&len, DEFAULT_PAYLOAD_CGROUP_PREFIX,
                                             handler->name,
                                             CGROUP_CREATE_RETRY, NULL);
        }
        if (!container_cgroup)
                return ret_set_errno(false, ENOMEM);

        if (!conf->cgroup_meta.container_dir) {
                suffix = container_cgroup + len - CGROUP_CREATE_RETRY_LEN;
                *suffix = '\0';
        }
        do {
                if (idx && suffix)
                        sprintf(suffix, "-%d", idx);

                for (i = 0; ops->hierarchies[i]; i++) {
                        if (cgroup_tree_create(ops, handler->conf,
                                               ops->hierarchies[i], cgroup_tree,
                                               container_cgroup, true,
                                               limiting_cgroup))
                                continue;

                        DEBUG("Failed to create cgroup \"%s\"", ops->hierarchies[i]->container_full_path ?: "(null)");
                        for (int j = 0; j < i; j++)
                                cgroup_tree_leaf_remove(ops->hierarchies[j], true);

                        idx++;
                        break;
                }
        } while (ops->hierarchies[i] && idx > 0 && idx < 1000 && suffix);

        if (idx == 1000 || (!suffix && idx != 0))
                return log_error_errno(false, ERANGE, "Failed to create container cgroup");

        ops->container_cgroup = move_ptr(container_cgroup);
        INFO("The container process uses \"%s\" as cgroup", ops->container_cgroup);
        return true;
}

__cgfsng_ops static bool cgfsng_monitor_enter(struct cgroup_ops *ops,
                                              struct lxc_handler *handler)
{
        int monitor_len, transient_len = 0;
        char monitor[INTTYPE_TO_STRLEN(pid_t)],
            transient[INTTYPE_TO_STRLEN(pid_t)];

        if (!ops)
                return ret_set_errno(false, ENOENT);

        if (!ops->hierarchies)
                return true;

        if (!ops->monitor_cgroup)
                return ret_set_errno(false, ENOENT);

        if (!handler || !handler->conf)
                return ret_set_errno(false, EINVAL);

        monitor_len = snprintf(monitor, sizeof(monitor), "%d", handler->monitor_pid);
        if (handler->transient_pid > 0)
                transient_len = snprintf(transient, sizeof(transient), "%d", handler->transient_pid);

        for (int i = 0; ops->hierarchies[i]; i++) {
                struct hierarchy *h = ops->hierarchies[i];
                int ret;

                ret = lxc_writeat(h->cgfd_mon, "cgroup.procs", monitor, monitor_len);
                if (ret)
                        return log_error_errno(false, errno, "Failed to enter cgroup \"%s\"", h->monitor_full_path);

                if (handler->transient_pid <= 0)
                        return true;

                ret = lxc_writeat(h->cgfd_mon, "cgroup.procs", transient, transient_len);
                if (ret)
                        return log_error_errno(false, errno, "Failed to enter cgroup \"%s\"", h->monitor_full_path);

                /*
                 * we don't keep the fds for non-unified hierarchies around
                 * mainly because we don't make use of them anymore after the
                 * core cgroup setup is done but also because there are quite a
                 * lot of them.
                 */
                if (!is_unified_hierarchy(h))
                        close_prot_errno_disarm(h->cgfd_mon);
        }
        handler->transient_pid = -1;

        return true;
}

__cgfsng_ops static bool cgfsng_payload_enter(struct cgroup_ops *ops,
                                              struct lxc_handler *handler)
{
        int len;
        char pidstr[INTTYPE_TO_STRLEN(pid_t)];

        if (!ops)
                return ret_set_errno(false, ENOENT);

        if (!ops->hierarchies)
                return true;

        if (!ops->container_cgroup)
                return ret_set_errno(false, ENOENT);

        if (!handler || !handler->conf)
                return ret_set_errno(false, EINVAL);

        len = snprintf(pidstr, sizeof(pidstr), "%d", handler->pid);

        for (int i = 0; ops->hierarchies[i]; i++) {
                struct hierarchy *h = ops->hierarchies[i];
                int ret;

                if (is_unified_hierarchy(h) && handler->clone_flags & CLONE_INTO_CGROUP)
                        continue;

                ret = lxc_writeat(h->cgfd_con, "cgroup.procs", pidstr, len);
                if (ret != 0)
                        return log_error_errno(false, errno, "Failed to enter cgroup \"%s\"", h->container_full_path);
        }

        return true;
}

static int fchowmodat(int dirfd, const char *path, uid_t chown_uid,
                      gid_t chown_gid, mode_t chmod_mode)
{
        int ret;

        ret = fchownat(dirfd, path, chown_uid, chown_gid,
                       AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW);
        if (ret < 0)
                return log_warn_errno(-1,
                                      errno, "Failed to fchownat(%d, %s, %d, %d, AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW )",
                                      dirfd, path, (int)chown_uid,
                                      (int)chown_gid);

        ret = fchmodat(dirfd, (*path != '\0') ? path : ".", chmod_mode, 0);
        if (ret < 0)
                return log_warn_errno(-1, errno, "Failed to fchmodat(%d, %s, %d, AT_SYMLINK_NOFOLLOW)",
                                      dirfd, path, (int)chmod_mode);

        return 0;
}

/* chgrp the container cgroups to container group.  We leave
 * the container owner as cgroup owner.  So we must make the
 * directories 775 so that the container can create sub-cgroups.
 *
 * Also chown the tasks and cgroup.procs files.  Those may not
 * exist depending on kernel version.
 */
static int chown_cgroup_wrapper(void *data)
{
        int ret;
        uid_t destuid;
        struct generic_userns_exec_data *arg = data;
        uid_t nsuid = (arg->conf->root_nsuid_map != NULL) ? 0 : arg->conf->init_uid;
        gid_t nsgid = (arg->conf->root_nsgid_map != NULL) ? 0 : arg->conf->init_gid;

        if (!lxc_setgroups(0, NULL) && errno != EPERM)
                return log_error_errno(-1, errno, "Failed to setgroups(0, NULL)");

        ret = setresgid(nsgid, nsgid, nsgid);
        if (ret < 0)
                return log_error_errno(-1, errno, "Failed to setresgid(%d, %d, %d)",
                                       (int)nsgid, (int)nsgid, (int)nsgid);

        ret = setresuid(nsuid, nsuid, nsuid);
        if (ret < 0)
                return log_error_errno(-1, errno, "Failed to setresuid(%d, %d, %d)",
                                       (int)nsuid, (int)nsuid, (int)nsuid);

        destuid = get_ns_uid(arg->origuid);
        if (destuid == LXC_INVALID_UID)
                destuid = 0;

        for (int i = 0; arg->hierarchies[i]; i++) {
                int dirfd = arg->hierarchies[i]->cgfd_con;

                (void)fchowmodat(dirfd, "", destuid, nsgid, 0775);

                /*
                 * Failures to chown() these are inconvenient but not
                 * detrimental We leave these owned by the container launcher,
                 * so that container root can write to the files to attach.  We
                 * chmod() them 664 so that container systemd can write to the
                 * files (which systemd in wily insists on doing).
                 */

                if (arg->hierarchies[i]->version == CGROUP_SUPER_MAGIC)
                        (void)fchowmodat(dirfd, "tasks", destuid, nsgid, 0664);

                (void)fchowmodat(dirfd, "cgroup.procs", destuid, nsgid, 0664);

                if (arg->hierarchies[i]->version != CGROUP2_SUPER_MAGIC)
                        continue;

                for (char **p = arg->hierarchies[i]->cgroup2_chown; p && *p; p++)
                        (void)fchowmodat(dirfd, *p, destuid, nsgid, 0664);
        }

        return 0;
}

__cgfsng_ops static bool cgfsng_chown(struct cgroup_ops *ops,
                                      struct lxc_conf *conf)
{
        struct generic_userns_exec_data wrap;

        if (!ops)
                return ret_set_errno(false, ENOENT);

        if (!ops->hierarchies)
                return true;

        if (!ops->container_cgroup)
                return ret_set_errno(false, ENOENT);

        if (!conf)
                return ret_set_errno(false, EINVAL);

        if (lxc_list_empty(&conf->id_map))
                return true;

        wrap.origuid = geteuid();
        wrap.path = NULL;
        wrap.hierarchies = ops->hierarchies;
        wrap.conf = conf;

        if (userns_exec_1(conf, chown_cgroup_wrapper, &wrap, "chown_cgroup_wrapper") < 0)
                return log_error_errno(false, errno, "Error requesting cgroup chown in new user namespace");

        return true;
}

__cgfsng_ops static void cgfsng_payload_finalize(struct cgroup_ops *ops)
{
        if (!ops)
                return;

        if (!ops->hierarchies)
                return;

        for (int i = 0; ops->hierarchies[i]; i++) {
                struct hierarchy *h = ops->hierarchies[i];
                /*
                 * we don't keep the fds for non-unified hierarchies around
                 * mainly because we don't make use of them anymore after the
                 * core cgroup setup is done but also because there are quite a
                 * lot of them.
                 */
                if (!is_unified_hierarchy(h))
                        close_prot_errno_disarm(h->cgfd_con);
        }

        /*
         * The checking for freezer support should obviously be done at cgroup
         * initialization time but that doesn't work reliable. The freezer
         * controller has been demoted (rightly so) to a simple file located in
         * each non-root cgroup. At the time when the container is created we
         * might still be located in /sys/fs/cgroup and so checking for
         * cgroup.freeze won't tell us anything because this file doesn't exist
         * in the root cgroup. We could then iterate through /sys/fs/cgroup and
         * find an already existing cgroup and then check within that cgroup
         * for the existence of cgroup.freeze but that will only work on
         * systemd based hosts. Other init systems might not manage cgroups and
         * so no cgroup will exist. So we defer until we have created cgroups
         * for our container which means we check here.
         */
        if (pure_unified_layout(ops) &&
            !faccessat(ops->unified->cgfd_con, "cgroup.freeze", F_OK,
                       AT_SYMLINK_NOFOLLOW)) {
                TRACE("Unified hierarchy supports freezer");
                ops->unified->freezer_controller = 1;
        }
}

/* cgroup-full:* is done, no need to create subdirs */
static inline bool cg_mount_needs_subdirs(int type)
{
        return !(type >= LXC_AUTO_CGROUP_FULL_RO);
}

/* After $rootfs/sys/fs/container/controller/the/cg/path has been created,
 * remount controller ro if needed and bindmount the cgroupfs onto
 * control/the/cg/path.
 */
static int cg_legacy_mount_controllers(int type, struct hierarchy *h,
                                       char *controllerpath, char *cgpath,
                                       const char *container_cgroup)
{
        __do_free char *sourcepath = NULL;
        int ret, remount_flags;
        int flags = MS_BIND;

        if (type == LXC_AUTO_CGROUP_RO || type == LXC_AUTO_CGROUP_MIXED) {
                ret = mount(controllerpath, controllerpath, "cgroup", MS_BIND, NULL);
                if (ret < 0)
                        return log_error_errno(-1, errno, "Failed to bind mount \"%s\" onto \"%s\"",
                                               controllerpath, controllerpath);

                remount_flags = add_required_remount_flags(controllerpath,
                                                           controllerpath,
                                                           flags | MS_REMOUNT);
                ret = mount(controllerpath, controllerpath, "cgroup",
                            remount_flags | MS_REMOUNT | MS_BIND | MS_RDONLY,
                            NULL);
                if (ret < 0)
                        return log_error_errno(-1, errno, "Failed to remount \"%s\" ro", controllerpath);

                INFO("Remounted %s read-only", controllerpath);
        }

        sourcepath = must_make_path(h->mountpoint, h->container_base_path,
                                    container_cgroup, NULL);
        if (type == LXC_AUTO_CGROUP_RO)
                flags |= MS_RDONLY;

        ret = mount(sourcepath, cgpath, "cgroup", flags, NULL);
        if (ret < 0)
                return log_error_errno(-1, errno, "Failed to mount \"%s\" onto \"%s\"",
                                       h->controllers[0], cgpath);
        INFO("Mounted \"%s\" onto \"%s\"", h->controllers[0], cgpath);

        if (flags & MS_RDONLY) {
                remount_flags = add_required_remount_flags(sourcepath, cgpath,
                                                           flags | MS_REMOUNT);
                ret = mount(sourcepath, cgpath, "cgroup", remount_flags, NULL);
                if (ret < 0)
                        return log_error_errno(-1, errno, "Failed to remount \"%s\" ro", cgpath);
                INFO("Remounted %s read-only", cgpath);
        }

        INFO("Completed second stage cgroup automounts for \"%s\"", cgpath);
        return 0;
}

/* __cg_mount_direct
 *
 * Mount cgroup hierarchies directly without using bind-mounts. The main
 * uses-cases are mounting cgroup hierarchies in cgroup namespaces and mounting
 * cgroups for the LXC_AUTO_CGROUP_FULL option.
 */
static int __cg_mount_direct(int type, struct hierarchy *h,
                             const char *controllerpath)
{
         __do_free char *controllers = NULL;
         char *fstype = "cgroup2";
         unsigned long flags = 0;
         int ret;

         flags |= MS_NOSUID;
         flags |= MS_NOEXEC;
         flags |= MS_NODEV;
         flags |= MS_RELATIME;

         if (type == LXC_AUTO_CGROUP_RO || type == LXC_AUTO_CGROUP_FULL_RO)
                 flags |= MS_RDONLY;

         if (h->version != CGROUP2_SUPER_MAGIC) {
                 controllers = lxc_string_join(",", (const char **)h->controllers, false);
                 if (!controllers)
                         return -ENOMEM;
                 fstype = "cgroup";
        }

        ret = mount("cgroup", controllerpath, fstype, flags, controllers);
        if (ret < 0)
                return log_error_errno(-1, errno, "Failed to mount \"%s\" with cgroup filesystem type %s",
                                       controllerpath, fstype);

        DEBUG("Mounted \"%s\" with cgroup filesystem type %s", controllerpath, fstype);
        return 0;
}

static inline int cg_mount_in_cgroup_namespace(int type, struct hierarchy *h,
                                               const char *controllerpath)
{
        return __cg_mount_direct(type, h, controllerpath);
}

static inline int cg_mount_cgroup_full(int type, struct hierarchy *h,
                                       const char *controllerpath)
{
        if (type < LXC_AUTO_CGROUP_FULL_RO || type > LXC_AUTO_CGROUP_FULL_MIXED)
                return 0;

        return __cg_mount_direct(type, h, controllerpath);
}

__cgfsng_ops static bool cgfsng_mount(struct cgroup_ops *ops,
                                      struct lxc_handler *handler,
                                      const char *root, int type)
{
        __do_free char *cgroup_root = NULL;
        bool has_cgns = false, wants_force_mount = false;
        int ret;

        if (!ops)
                return ret_set_errno(false, ENOENT);

        if (!ops->hierarchies)
                return true;

        if (!handler || !handler->conf)
                return ret_set_errno(false, EINVAL);

        if ((type & LXC_AUTO_CGROUP_MASK) == 0)
                return true;

        if (type & LXC_AUTO_CGROUP_FORCE) {
                type &= ~LXC_AUTO_CGROUP_FORCE;
                wants_force_mount = true;
        }

        if (!wants_force_mount) {
                wants_force_mount = !lxc_wants_cap(CAP_SYS_ADMIN, handler->conf);

                /*
                 * Most recent distro versions currently have init system that
                 * do support cgroup2 but do not mount it by default unless
                 * explicitly told so even if the host is cgroup2 only. That
                 * means they often will fail to boot. Fix this by pre-mounting
                 * cgroup2 by default. We will likely need to be doing this a
                 * few years until all distros have switched over to cgroup2 at
                 * which point we can safely assume that their init systems
                 * will mount it themselves.
                 */
                if (pure_unified_layout(ops))
                        wants_force_mount = true;
        }

        has_cgns = cgns_supported();
        if (has_cgns && !wants_force_mount)
                return true;

        if (type == LXC_AUTO_CGROUP_NOSPEC)
                type = LXC_AUTO_CGROUP_MIXED;
        else if (type == LXC_AUTO_CGROUP_FULL_NOSPEC)
                type = LXC_AUTO_CGROUP_FULL_MIXED;

        cgroup_root = must_make_path(root, DEFAULT_CGROUP_MOUNTPOINT, NULL);
        if (ops->cgroup_layout == CGROUP_LAYOUT_UNIFIED) {
                if (has_cgns && wants_force_mount) {
                        /*
                         * If cgroup namespaces are supported but the container
                         * will not have CAP_SYS_ADMIN after it has started we
                         * need to mount the cgroups manually.
                         */
                        return cg_mount_in_cgroup_namespace(type, ops->unified, cgroup_root) == 0;
                }

                return cg_mount_cgroup_full(type, ops->unified, cgroup_root) == 0;
        }

        /*
         * Mount a tmpfs over DEFAULT_CGROUP_MOUNTPOINT. Note that we're
         * relying on RESOLVE_BENEATH so we need to skip the leading "/" in the
         * DEFAULT_CGROUP_MOUNTPOINT define.
         */
        ret = safe_mount_beneath(root, NULL,
                                 DEFAULT_CGROUP_MOUNTPOINT_RELATIVE,
                                 "tmpfs",
                                 MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_RELATIME,
                                 "size=10240k,mode=755");
        if (ret < 0) {
                if (errno != ENOSYS)
                        return log_error_errno(false, errno,
                                               "Failed to mount tmpfs on %s",
                                               DEFAULT_CGROUP_MOUNTPOINT);

                ret = safe_mount(NULL, cgroup_root, "tmpfs",
                                 MS_NOSUID | MS_NODEV | MS_NOEXEC | MS_RELATIME,
                                 "size=10240k,mode=755", root);
        }
        if (ret < 0)
                return false;

        for (int i = 0; ops->hierarchies[i]; i++) {
                __do_free char *controllerpath = NULL, *path2 = NULL;
                struct hierarchy *h = ops->hierarchies[i];
                char *controller = strrchr(h->mountpoint, '/');

                if (!controller)
                        continue;
                controller++;

                controllerpath = must_make_path(cgroup_root, controller, NULL);
                if (dir_exists(controllerpath))
                        continue;

                ret = mkdir(controllerpath, 0755);
                if (ret < 0)
                        return log_error_errno(false, errno, "Error creating cgroup path: %s", controllerpath);

                if (has_cgns && wants_force_mount) {
                        /* If cgroup namespaces are supported but the container
                         * will not have CAP_SYS_ADMIN after it has started we
                         * need to mount the cgroups manually.
                         */
                        ret = cg_mount_in_cgroup_namespace(type, h, controllerpath);
                        if (ret < 0)
                                return false;

                        continue;
                }

                ret = cg_mount_cgroup_full(type, h, controllerpath);
                if (ret < 0)
                        return false;

                if (!cg_mount_needs_subdirs(type))
                        continue;

                path2 = must_make_path(controllerpath, h->container_base_path,
                                       ops->container_cgroup, NULL);
                ret = mkdir_p(path2, 0755);
                if (ret < 0)
                        return false;

                ret = cg_legacy_mount_controllers(type, h, controllerpath,
                                                  path2, ops->container_cgroup);
                if (ret < 0)
                        return false;
        }

        return true;
}

/* Only root needs to escape to the cgroup of its init. */
__cgfsng_ops static bool cgfsng_escape(const struct cgroup_ops *ops,
                                       struct lxc_conf *conf)
{
        if (!ops)
                return ret_set_errno(false, ENOENT);

        if (!ops->hierarchies)
                return true;

        if (!conf)
                return ret_set_errno(false, EINVAL);

        if (conf->cgroup_meta.relative || geteuid())
                return true;

        for (int i = 0; ops->hierarchies[i]; i++) {
                __do_free char *fullpath = NULL;
                int ret;

                fullpath =
                    must_make_path(ops->hierarchies[i]->mountpoint,
                                   ops->hierarchies[i]->container_base_path,
                                   "cgroup.procs", NULL);
                ret = lxc_write_to_file(fullpath, "0", 2, false, 0666);
                if (ret != 0)
                        return log_error_errno(false, errno, "Failed to escape to cgroup \"%s\"", fullpath);
        }

        return true;
}

__cgfsng_ops static int cgfsng_num_hierarchies(struct cgroup_ops *ops)
{
        int i = 0;

        if (!ops)
                return ret_set_errno(-1, ENOENT);

        if (!ops->hierarchies)
                return 0;

        for (; ops->hierarchies[i]; i++)
                ;

        return i;
}

__cgfsng_ops static bool cgfsng_get_hierarchies(struct cgroup_ops *ops, int n,
                                                char ***out)
{
        int i;

        if (!ops)
                return ret_set_errno(false, ENOENT);

        if (!ops->hierarchies)
                return ret_set_errno(false, ENOENT);

        /* sanity check n */
        for (i = 0; i < n; i++)
                if (!ops->hierarchies[i])
                        return ret_set_errno(false, ENOENT);

        *out = ops->hierarchies[i]->controllers;

        return true;
}

static bool cg_legacy_freeze(struct cgroup_ops *ops)
{
        struct hierarchy *h;

        h = get_hierarchy(ops, "freezer");
        if (!h)
                return ret_set_errno(-1, ENOENT);

        return lxc_write_openat(h->container_full_path, "freezer.state",
                                "FROZEN", STRLITERALLEN("FROZEN"));
}

static int freezer_cgroup_events_cb(int fd, uint32_t events, void *cbdata,
                                    struct lxc_epoll_descr *descr)
{
        __do_close int duped_fd = -EBADF;
        __do_free char *line = NULL;
        __do_fclose FILE *f = NULL;
        int state = PTR_TO_INT(cbdata);
        size_t len;
        const char *state_string;

        duped_fd = dup(fd);
        if (duped_fd < 0)
                return LXC_MAINLOOP_ERROR;

        if (lseek(duped_fd, 0, SEEK_SET) < (off_t)-1)
                return LXC_MAINLOOP_ERROR;

        f = fdopen(duped_fd, "re");
        if (!f)
                return LXC_MAINLOOP_ERROR;
        move_fd(duped_fd);

        if (state == 1)
                state_string = "frozen 1";
        else
                state_string = "frozen 0";

        while (getline(&line, &len, f) != -1)
                if (strncmp(line, state_string, STRLITERALLEN("frozen") + 2) == 0)
                        return LXC_MAINLOOP_CLOSE;

        return LXC_MAINLOOP_CONTINUE;
}

static int cg_unified_freeze_do(struct cgroup_ops *ops, int timeout,
                                const char *state_string,
                                int state_num,
                                const char *epoll_error,
                                const char *wait_error)
{
        __do_close int fd = -EBADF;
        call_cleaner(lxc_mainloop_close) struct lxc_epoll_descr *descr_ptr = NULL;
        int ret;
        struct lxc_epoll_descr descr;
        struct hierarchy *h;

        h = ops->unified;
        if (!h)
                return ret_set_errno(-1, ENOENT);

        if (!h->container_full_path)
                return ret_set_errno(-1, EEXIST);

        if (timeout != 0) {
                __do_free char *events_file = NULL;

                events_file = must_make_path(h->container_full_path, "cgroup.events", NULL);
                fd = open(events_file, O_RDONLY | O_CLOEXEC);
                if (fd < 0)
                        return log_error_errno(-1, errno, "Failed to open cgroup.events file");

                ret = lxc_mainloop_open(&descr);
                if (ret)
                        return log_error_errno(-1, errno, "%s", epoll_error);

                /* automatically cleaned up now */
                descr_ptr = &descr;

                ret = lxc_mainloop_add_handler_events(&descr, fd, EPOLLPRI, freezer_cgroup_events_cb, INT_TO_PTR(state_num));
                if (ret < 0)
                        return log_error_errno(-1, errno, "Failed to add cgroup.events fd handler to mainloop");
        }

        ret = lxc_write_openat(h->container_full_path, "cgroup.freeze", state_string, 1);
        if (ret < 0)
                return log_error_errno(-1, errno, "Failed to open cgroup.freeze file");

        if (timeout != 0 && lxc_mainloop(&descr, timeout))
                return log_error_errno(-1, errno, "%s", wait_error);

        return 0;
}

static int cg_unified_freeze(struct cgroup_ops *ops, int timeout)
{
        return cg_unified_freeze_do(ops, timeout, "1", 1,
                "Failed to create epoll instance to wait for container freeze",
                "Failed to wait for container to be frozen");
}

__cgfsng_ops static int cgfsng_freeze(struct cgroup_ops *ops, int timeout)
{
        if (!ops->hierarchies)
                return ret_set_errno(-1, ENOENT);

        if (ops->cgroup_layout != CGROUP_LAYOUT_UNIFIED)
                return cg_legacy_freeze(ops);

        return cg_unified_freeze(ops, timeout);
}

static int cg_legacy_unfreeze(struct cgroup_ops *ops)
{
        struct hierarchy *h;

        h = get_hierarchy(ops, "freezer");
        if (!h)
                return ret_set_errno(-1, ENOENT);

        return lxc_write_openat(h->container_full_path, "freezer.state",
                                "THAWED", STRLITERALLEN("THAWED"));
}

static int cg_unified_unfreeze(struct cgroup_ops *ops, int timeout)
{
        return cg_unified_freeze_do(ops, timeout, "0", 0,
                "Failed to create epoll instance to wait for container unfreeze",
                "Failed to wait for container to be unfrozen");
}

__cgfsng_ops static int cgfsng_unfreeze(struct cgroup_ops *ops, int timeout)
{
        if (!ops->hierarchies)
                return ret_set_errno(-1, ENOENT);

        if (ops->cgroup_layout != CGROUP_LAYOUT_UNIFIED)
                return cg_legacy_unfreeze(ops);

        return cg_unified_unfreeze(ops, timeout);
}

static const char *cgfsng_get_cgroup_do(struct cgroup_ops *ops,
                                        const char *controller, bool limiting)
{
        struct hierarchy *h;

        h = get_hierarchy(ops, controller);
        if (!h)
                return log_warn_errno(NULL, ENOENT, "Failed to find hierarchy for controller \"%s\"",
                                      controller ? controller : "(null)");

        if (limiting)
                return h->container_limit_path
                           ? h->container_limit_path + strlen(h->mountpoint)
                           : NULL;

        return h->container_full_path
                   ? h->container_full_path + strlen(h->mountpoint)
                   : NULL;
}

__cgfsng_ops static const char *cgfsng_get_cgroup(struct cgroup_ops *ops,
                                                  const char *controller)
{
    return cgfsng_get_cgroup_do(ops, controller, false);
}

__cgfsng_ops static const char *cgfsng_get_limiting_cgroup(struct cgroup_ops *ops,
                                                           const char *controller)
{
    return cgfsng_get_cgroup_do(ops, controller, true);
}

/* Given a cgroup path returned from lxc_cmd_get_cgroup_path, build a full path,
 * which must be freed by the caller.
 */
static inline char *build_full_cgpath_from_monitorpath(struct hierarchy *h,
                                                       const char *inpath,
                                                       const char *filename)
{
        return must_make_path(h->mountpoint, inpath, filename, NULL);
}

static int cgroup_attach_leaf(const struct lxc_conf *conf, int unified_fd, pid_t pid)
{
        int idx = 1;
        int ret;
        char pidstr[INTTYPE_TO_STRLEN(int64_t) + 1];
        size_t pidstr_len;

        /* Create leaf cgroup. */
        ret = mkdirat(unified_fd, ".lxc", 0755);
        if (ret < 0 && errno != EEXIST)
                return log_error_errno(-1, errno, "Failed to create leaf cgroup \".lxc\"");

        pidstr_len = sprintf(pidstr, INT64_FMT, (int64_t)pid);
        ret = lxc_writeat(unified_fd, ".lxc/cgroup.procs", pidstr, pidstr_len);
        if (ret < 0)
                ret = lxc_writeat(unified_fd, "cgroup.procs", pidstr, pidstr_len);
        if (ret == 0)
                return 0;

        /* this is a non-leaf node */
        if (errno != EBUSY)
                return log_error_errno(-1, errno, "Failed to attach to unified cgroup");

        do {
                bool rm = false;
                char attach_cgroup[STRLITERALLEN(".lxc-/cgroup.procs") + INTTYPE_TO_STRLEN(int) + 1];
                char *slash = attach_cgroup;

                ret = snprintf(attach_cgroup, sizeof(attach_cgroup), ".lxc-%d/cgroup.procs", idx);
                if (ret < 0 || (size_t)ret >= sizeof(attach_cgroup))
                        return ret_errno(EIO);

                /*
                 * This shouldn't really happen but the compiler might complain
                 * that a short write would cause a buffer overrun. So be on
                 * the safe side.
                 */
                if (ret < STRLITERALLEN(".lxc-/cgroup.procs"))
                        return log_error_errno(-EINVAL, EINVAL, "Unexpected short write would cause buffer-overrun");

                slash += (ret - STRLITERALLEN("/cgroup.procs"));
                *slash = '\0';

                ret = mkdirat(unified_fd, attach_cgroup, 0755);
                if (ret < 0 && errno != EEXIST)
                        return log_error_errno(-1, errno, "Failed to create cgroup %s", attach_cgroup);
                if (ret == 0)
                        rm = true;

                *slash = '/';

                ret = lxc_writeat(unified_fd, attach_cgroup, pidstr, pidstr_len);
                if (ret == 0)
                        return 0;

                if (rm && unlinkat(unified_fd, attach_cgroup, AT_REMOVEDIR))
                        SYSERROR("Failed to remove cgroup \"%d(%s)\"", unified_fd, attach_cgroup);

                /* this is a non-leaf node */
                if (errno != EBUSY)
                        return log_error_errno(-1, errno, "Failed to attach to unified cgroup");

                idx++;
        } while (idx < 1000);

        return log_error_errno(-1, errno, "Failed to attach to unified cgroup");
}

static int cgroup_attach_create_leaf(const struct lxc_conf *conf,
                                     int unified_fd, int *sk_fd)
{
        __do_close int sk = *sk_fd, target_fd0 = -EBADF, target_fd1 = -EBADF;
        int target_fds[2];
        ssize_t ret;

        /* Create leaf cgroup. */
        ret = mkdirat(unified_fd, ".lxc", 0755);
        if (ret < 0 && errno != EEXIST)
                return log_error_errno(-1, errno, "Failed to create leaf cgroup \".lxc\"");

        target_fd0 = openat(unified_fd, ".lxc/cgroup.procs", O_WRONLY | O_CLOEXEC | O_NOFOLLOW);
        if (target_fd0 < 0)
                return log_error_errno(-errno, errno, "Failed to open \".lxc/cgroup.procs\"");
        target_fds[0] = target_fd0;

        target_fd1 = openat(unified_fd, "cgroup.procs", O_WRONLY | O_CLOEXEC | O_NOFOLLOW);
        if (target_fd1 < 0)
                return log_error_errno(-errno, errno, "Failed to open \".lxc/cgroup.procs\"");
        target_fds[1] = target_fd1;

        ret = lxc_abstract_unix_send_fds(sk, target_fds, 2, NULL, 0);
        if (ret <= 0)
                return log_error_errno(-errno, errno, "Failed to send \".lxc/cgroup.procs\" fds %d and %d",
                                       target_fd0, target_fd1);

        return log_debug(0, "Sent target cgroup fds %d and %d", target_fd0, target_fd1);
}

static int cgroup_attach_move_into_leaf(const struct lxc_conf *conf,
                                        int *sk_fd, pid_t pid)
{
        __do_close int sk = *sk_fd, target_fd0 = -EBADF, target_fd1 = -EBADF;
        int target_fds[2];
        char pidstr[INTTYPE_TO_STRLEN(int64_t) + 1];
        size_t pidstr_len;
        ssize_t ret;

        ret = lxc_abstract_unix_recv_fds(sk, target_fds, 2, NULL, 0);
        if (ret <= 0)
                return log_error_errno(-1, errno, "Failed to receive target cgroup fd");
        target_fd0 = target_fds[0];
        target_fd1 = target_fds[1];

        pidstr_len = sprintf(pidstr, INT64_FMT, (int64_t)pid);

        ret = lxc_write_nointr(target_fd0, pidstr, pidstr_len);
        if (ret > 0 && ret == pidstr_len)
                return log_debug(0, "Moved process into target cgroup via fd %d", target_fd0);

        ret = lxc_write_nointr(target_fd1, pidstr, pidstr_len);
        if (ret > 0 && ret == pidstr_len)
                return log_debug(0, "Moved process into target cgroup via fd %d", target_fd1);

        return log_debug_errno(-1, errno, "Failed to move process into target cgroup via fd %d and %d",
                               target_fd0, target_fd1);
}

struct userns_exec_unified_attach_data {
        const struct lxc_conf *conf;
        int unified_fd;
        int sk_pair[2];
        pid_t pid;
};

static int cgroup_unified_attach_child_wrapper(void *data)
{
        struct userns_exec_unified_attach_data *args = data;

        if (!args->conf || args->unified_fd < 0 || args->pid <= 0 ||
            args->sk_pair[0] < 0 || args->sk_pair[1] < 0)
                return ret_errno(EINVAL);

        close_prot_errno_disarm(args->sk_pair[0]);
        return cgroup_attach_create_leaf(args->conf, args->unified_fd,
                                         &args->sk_pair[1]);
}

static int cgroup_unified_attach_parent_wrapper(void *data)
{
        struct userns_exec_unified_attach_data *args = data;

        if (!args->conf || args->unified_fd < 0 || args->pid <= 0 ||
            args->sk_pair[0] < 0 || args->sk_pair[1] < 0)
                return ret_errno(EINVAL);

        close_prot_errno_disarm(args->sk_pair[1]);
        return cgroup_attach_move_into_leaf(args->conf, &args->sk_pair[0],
                                            args->pid);
}

int cgroup_attach(const struct lxc_conf *conf, const char *name,
                  const char *lxcpath, pid_t pid)
{
        __do_close int unified_fd = -EBADF;
        int ret;

        if (!conf || !name || !lxcpath || pid <= 0)
                return ret_errno(EINVAL);

        unified_fd = lxc_cmd_get_cgroup2_fd(name, lxcpath);
        if (unified_fd < 0)
                return ret_errno(EBADF);

        if (!lxc_list_empty(&conf->id_map)) {
                struct userns_exec_unified_attach_data args = {
                        .conf           = conf,
                        .unified_fd     = unified_fd,
                        .pid            = pid,
                };

                ret = socketpair(PF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, args.sk_pair);
                if (ret < 0)
                        return -errno;

                ret = userns_exec_minimal(conf,
                                          cgroup_unified_attach_parent_wrapper,
                                          &args,
                                          cgroup_unified_attach_child_wrapper,
                                          &args);
        } else {
                ret = cgroup_attach_leaf(conf, unified_fd, pid);
        }

        return ret;
}

/* Technically, we're always at a delegation boundary here (This is especially
 * true when cgroup namespaces are available.). The reasoning is that in order
 * for us to have been able to start a container in the first place the root
 * cgroup must have been a leaf node. Now, either the container's init system
 * has populated the cgroup and kept it as a leaf node or it has created
 * subtrees. In the former case we will simply attach to the leaf node we
 * created when we started the container in the latter case we create our own
 * cgroup for the attaching process.
 */
static int __cg_unified_attach(const struct hierarchy *h,
                               const struct lxc_conf *conf, const char *name,
                               const char *lxcpath, pid_t pid,
                               const char *controller)
{
        __do_close int unified_fd = -EBADF;
        __do_free char *path = NULL, *cgroup = NULL;
        int ret;

        if (!conf || !name || !lxcpath || pid <= 0)
                return ret_errno(EINVAL);

        ret = cgroup_attach(conf, name, lxcpath, pid);
        if (ret == 0)
                return log_trace(0, "Attached to unified cgroup via command handler");
        if (ret != -EBADF)
                return log_error_errno(ret, errno, "Failed to attach to unified cgroup");

        /* Fall back to retrieving the path for the unified cgroup. */
        cgroup = lxc_cmd_get_cgroup_path(name, lxcpath, controller);
        /* not running */
        if (!cgroup)
                return 0;

        path = must_make_path(h->mountpoint, cgroup, NULL);

        unified_fd = open(path, O_PATH | O_DIRECTORY | O_CLOEXEC);
        if (unified_fd < 0)
                return ret_errno(EBADF);

        if (!lxc_list_empty(&conf->id_map)) {
                struct userns_exec_unified_attach_data args = {
                        .conf           = conf,
                        .unified_fd     = unified_fd,
                        .pid            = pid,
                };

                ret = socketpair(PF_LOCAL, SOCK_STREAM | SOCK_CLOEXEC, 0, args.sk_pair);
                if (ret < 0)
                        return -errno;

                ret = userns_exec_minimal(conf,
                                          cgroup_unified_attach_parent_wrapper,
                                          &args,
                                          cgroup_unified_attach_child_wrapper,
                                          &args);
        } else {
                ret = cgroup_attach_leaf(conf, unified_fd, pid);
        }

        return ret;
}

__cgfsng_ops static bool cgfsng_attach(struct cgroup_ops *ops,
                                       const struct lxc_conf *conf,
                                       const char *name, const char *lxcpath,
                                       pid_t pid)
{
        int len, ret;
        char pidstr[INTTYPE_TO_STRLEN(pid_t)];

        if (!ops)
                return ret_set_errno(false, ENOENT);

        if (!ops->hierarchies)
                return true;

        len = snprintf(pidstr, sizeof(pidstr), "%d", pid);
        if (len < 0 || (size_t)len >= sizeof(pidstr))
                return false;

        for (int i = 0; ops->hierarchies[i]; i++) {
                __do_free char *fullpath = NULL, *path = NULL;
                struct hierarchy *h = ops->hierarchies[i];

                if (h->version == CGROUP2_SUPER_MAGIC) {
                        ret = __cg_unified_attach(h, conf, name, lxcpath, pid,
                                                  h->controllers[0]);
                        if (ret < 0)
                                return false;

                        continue;
                }

                path = lxc_cmd_get_cgroup_path(name, lxcpath, h->controllers[0]);
                /* not running */
                if (!path)
                        return false;

                fullpath = build_full_cgpath_from_monitorpath(h, path, "cgroup.procs");
                ret = lxc_write_to_file(fullpath, pidstr, len, false, 0666);
                if (ret < 0)
                        return log_error_errno(false, errno, "Failed to attach %d to %s",
                                               (int)pid, fullpath);
        }

        return true;
}

/* Called externally (i.e. from 'lxc-cgroup') to query cgroup limits.  Here we
 * don't have a cgroup_data set up, so we ask the running container through the
 * commands API for the cgroup path.
 */
__cgfsng_ops static int cgfsng_get(struct cgroup_ops *ops, const char *filename,
                                     char *value, size_t len, const char *name,
                                     const char *lxcpath)
{
        __do_free char *path = NULL;
        __do_free char *controller = NULL;
        char *p;
        struct hierarchy *h;
        int ret = -1;

        if (!ops)
                return ret_set_errno(-1, ENOENT);

        controller = must_copy_string(filename);
        p = strchr(controller, '.');
        if (p)
                *p = '\0';

        path = lxc_cmd_get_limiting_cgroup_path(name, lxcpath, controller);
        /* not running */
        if (!path)
                return -1;

        h = get_hierarchy(ops, controller);
        if (h) {
                __do_free char *fullpath = NULL;

                fullpath = build_full_cgpath_from_monitorpath(h, path, filename);
                ret = lxc_read_from_file(fullpath, value, len);
        }

        return ret;
}

static int device_cgroup_parse_access(struct device_item *device, const char *val)
{
        for (int count = 0; count < 3; count++, val++) {
                switch (*val) {
                case 'r':
                        device->access[count] = *val;
                        break;
                case 'w':
                        device->access[count] = *val;
                        break;
                case 'm':
                        device->access[count] = *val;
                        break;
                case '\n':
                case '\0':
                        count = 3;
                        break;
                default:
                        return ret_errno(EINVAL);
                }
        }

        return 0;
}

static int device_cgroup_rule_parse(struct device_item *device, const char *key,
                                    const char *val)
{
        int count, ret;
        char temp[50];

        if (strcmp("devices.allow", key) == 0)
                device->allow = 1;
        else
                device->allow = 0;

        if (strcmp(val, "a") == 0) {
                /* global rule */
                device->type = 'a';
                device->major = -1;
                device->minor = -1;
                device->global_rule = device->allow
                                          ? LXC_BPF_DEVICE_CGROUP_DENYLIST
                                          : LXC_BPF_DEVICE_CGROUP_ALLOWLIST;
                device->allow = -1;
                return 0;
        }

        /* local rule */
        device->global_rule = LXC_BPF_DEVICE_CGROUP_LOCAL_RULE;

        switch (*val) {
        case 'a':
                __fallthrough;
        case 'b':
                __fallthrough;
        case 'c':
                device->type = *val;
                break;
        default:
                return -1;
        }

        val++;
        if (!isspace(*val))
                return -1;
        val++;
        if (*val == '*') {
                device->major = -1;
                val++;
        } else if (isdigit(*val)) {
                memset(temp, 0, sizeof(temp));
                for (count = 0; count < sizeof(temp) - 1; count++) {
                        temp[count] = *val;
                        val++;
                        if (!isdigit(*val))
                                break;
                }
                ret = lxc_safe_int(temp, &device->major);
                if (ret)
                        return -1;
        } else {
                return -1;
        }
        if (*val != ':')
                return -1;
        val++;

        /* read minor */
        if (*val == '*') {
                device->minor = -1;
                val++;
        } else if (isdigit(*val)) {
                memset(temp, 0, sizeof(temp));
                for (count = 0; count < sizeof(temp) - 1; count++) {
                        temp[count] = *val;
                        val++;
                        if (!isdigit(*val))
                                break;
                }
                ret = lxc_safe_int(temp, &device->minor);
                if (ret)
                        return -1;
        } else {
                return -1;
        }
        if (!isspace(*val))
                return -1;

        return device_cgroup_parse_access(device, ++val);
}

/* Called externally (i.e. from 'lxc-cgroup') to set new cgroup limits.  Here we
 * don't have a cgroup_data set up, so we ask the running container through the
 * commands API for the cgroup path.
 */
__cgfsng_ops static int cgfsng_set(struct cgroup_ops *ops,
                                     const char *key, const char *value,
                                     const char *name, const char *lxcpath)
{
        __do_free char *path = NULL;
        __do_free char *controller = NULL;
        char *p;
        struct hierarchy *h;
        int ret = -1;

        if (!ops || !key || !value || !name || !lxcpath)
                return ret_errno(ENOENT);

        controller = must_copy_string(key);
        p = strchr(controller, '.');
        if (p)
                *p = '\0';

        if (pure_unified_layout(ops) && strcmp(controller, "devices") == 0) {
                struct device_item device = {};

                ret = device_cgroup_rule_parse(&device, key, value);
                if (ret < 0)
                        return log_error_errno(-1, EINVAL, "Failed to parse device string %s=%s",
                                               key, value);

                ret = lxc_cmd_add_bpf_device_cgroup(name, lxcpath, &device);
                if (ret < 0)
                        return -1;

                return 0;
        }

        path = lxc_cmd_get_limiting_cgroup_path(name, lxcpath, controller);
        /* not running */
        if (!path)
                return -1;

        h = get_hierarchy(ops, controller);
        if (h) {
                __do_free char *fullpath = NULL;

                fullpath = build_full_cgpath_from_monitorpath(h, path, key);
                ret = lxc_write_to_file(fullpath, value, strlen(value), false, 0666);
        }

        return ret;
}

/* take devices cgroup line
 *    /dev/foo rwx
 * and convert it to a valid
 *    type major:minor mode
 * line. Return <0 on error. Dest is a preallocated buffer long enough to hold
 * the output.
 */
static int device_cgroup_rule_parse_devpath(struct device_item *device,
                                            const char *devpath)
{
        __do_free char *path = NULL;
        char *mode = NULL;
        int n_parts, ret;
        char *p;
        struct stat sb;

        path = must_copy_string(devpath);

        /*
         * Read path followed by mode. Ignore any trailing text.
         * A '    # comment' would be legal. Technically other text is not
         * legal, we could check for that if we cared to.
         */
        for (n_parts = 1, p = path; *p; p++) {
                if (*p != ' ')
                        continue;
                *p = '\0';

                if (n_parts != 1)
                        break;
                p++;
                n_parts++;

                while (*p == ' ')
                        p++;

                mode = p;

                if (*p == '\0')
                        return ret_set_errno(-1, EINVAL);
        }

        if (!mode)
                return ret_errno(EINVAL);

        if (device_cgroup_parse_access(device, mode) < 0)
                return -1;

        ret = stat(path, &sb);
        if (ret < 0)
                return ret_set_errno(-1, errno);

        mode_t m = sb.st_mode & S_IFMT;
        switch (m) {
        case S_IFBLK:
                device->type = 'b';
                break;
        case S_IFCHR:
                device->type = 'c';
                break;
        default:
                return log_error_errno(-1, EINVAL, "Unsupported device type %i for \"%s\"", m, path);
        }

        device->major = MAJOR(sb.st_rdev);
        device->minor = MINOR(sb.st_rdev);
        device->allow = 1;
        device->global_rule = LXC_BPF_DEVICE_CGROUP_LOCAL_RULE;

        return 0;
}

static int convert_devpath(const char *invalue, char *dest)
{
        struct device_item device = {};
        int ret;

        ret = device_cgroup_rule_parse_devpath(&device, invalue);
        if (ret < 0)
                return -1;

        ret = snprintf(dest, 50, "%c %d:%d %s", device.type, device.major,
                       device.minor, device.access);
        if (ret < 0 || ret >= 50)
                return log_error_errno(-1, ENAMETOOLONG, "Error on configuration value \"%c %d:%d %s\" (max 50 chars)",
                                       device.type, device.major, device.minor, device.access);

        return 0;
}

/* Called from setup_limits - here we have the container's cgroup_data because
 * we created the cgroups.
 */
static int cg_legacy_set_data(struct cgroup_ops *ops, const char *filename,
                              const char *value, bool is_cpuset)
{
        __do_free char *controller = NULL;
        char *p;
        /* "b|c <2^64-1>:<2^64-1> r|w|m" = 47 chars max */
        char converted_value[50];
        struct hierarchy *h;

        controller = must_copy_string(filename);
        p = strchr(controller, '.');
        if (p)
                *p = '\0';

        if (strcmp("devices.allow", filename) == 0 && value[0] == '/') {
                int ret;

                ret = convert_devpath(value, converted_value);
                if (ret < 0)
                        return ret;
                value = converted_value;
        }

        h = get_hierarchy(ops, controller);
        if (!h)
                return log_error_errno(-ENOENT, ENOENT, "Failed to setup limits for the \"%s\" controller. The controller seems to be unused by \"cgfsng\" cgroup driver or not enabled on the cgroup hierarchy", controller);

        if (is_cpuset) {
                int ret = lxc_write_openat(h->container_full_path, filename, value, strlen(value));
                if (ret)
                        return ret;
        }
        return lxc_write_openat(h->container_limit_path, filename, value, strlen(value));
}

__cgfsng_ops static bool cgfsng_setup_limits_legacy(struct cgroup_ops *ops,
                                                    struct lxc_conf *conf,
                                                    bool do_devices)
{
        __do_free struct lxc_list *sorted_cgroup_settings = NULL;
        struct lxc_list *cgroup_settings = &conf->cgroup;
        struct lxc_list *iterator, *next;
        struct lxc_cgroup *cg;
        bool ret = false;

        if (!ops)
                return ret_set_errno(false, ENOENT);

        if (!conf)
                return ret_set_errno(false, EINVAL);

        cgroup_settings = &conf->cgroup;
        if (lxc_list_empty(cgroup_settings))
                return true;

        if (!ops->hierarchies)
                return ret_set_errno(false, EINVAL);

        if (pure_unified_layout(ops))
                return log_warn_errno(true, EINVAL, "Ignoring legacy cgroup limits on pure cgroup2 system");

        sorted_cgroup_settings = sort_cgroup_settings(cgroup_settings);
        if (!sorted_cgroup_settings)
                return false;

        lxc_list_for_each(iterator, sorted_cgroup_settings) {
                cg = iterator->elem;

                if (do_devices == !strncmp("devices", cg->subsystem, 7)) {
                        if (cg_legacy_set_data(ops, cg->subsystem, cg->value, strncmp("cpuset", cg->subsystem, 6) == 0)) {
                                if (do_devices && (errno == EACCES || errno == EPERM)) {
                                        SYSWARN("Failed to set \"%s\" to \"%s\"", cg->subsystem, cg->value);
                                        continue;
                                }
                                SYSERROR("Failed to set \"%s\" to \"%s\"", cg->subsystem, cg->value);
                                goto out;
                        }
                        DEBUG("Set controller \"%s\" set to \"%s\"", cg->subsystem, cg->value);
                }
        }

        ret = true;
        INFO("Limits for the legacy cgroup hierarchies have been setup");
out:
        lxc_list_for_each_safe(iterator, sorted_cgroup_settings, next) {
                lxc_list_del(iterator);
                free(iterator);
        }

        return ret;
}

/*
 * Some of the parsing logic comes from the original cgroup device v1
 * implementation in the kernel.
 */
static int bpf_device_cgroup_prepare(struct cgroup_ops *ops,
                                     struct lxc_conf *conf, const char *key,
                                     const char *val)
{
#ifdef HAVE_STRUCT_BPF_CGROUP_DEV_CTX
        struct device_item device_item = {};
        int ret;

        if (strcmp("devices.allow", key) == 0 && *val == '/')
                ret = device_cgroup_rule_parse_devpath(&device_item, val);
        else
                ret = device_cgroup_rule_parse(&device_item, key, val);
        if (ret < 0)
                return log_error_errno(-1, EINVAL, "Failed to parse device string %s=%s", key, val);

        ret = bpf_list_add_device(conf, &device_item);
        if (ret < 0)
                return -1;
#endif
        return 0;
}

__cgfsng_ops static bool cgfsng_setup_limits(struct cgroup_ops *ops,
                                             struct lxc_handler *handler)
{
        struct lxc_list *cgroup_settings, *iterator;
        struct hierarchy *h;
        struct lxc_conf *conf;

        if (!ops)
                return ret_set_errno(false, ENOENT);

        if (!ops->hierarchies)
                return true;

        if (!ops->container_cgroup)
                return ret_set_errno(false, EINVAL);

        if (!handler || !handler->conf)
                return ret_set_errno(false, EINVAL);
        conf = handler->conf;

        cgroup_settings = &conf->cgroup2;
        if (lxc_list_empty(cgroup_settings))
                return true;

        if (!pure_unified_layout(ops))
                return log_warn_errno(true, EINVAL, "Ignoring cgroup2 limits on legacy cgroup system");

        if (!ops->unified)
                return false;
        h = ops->unified;

        lxc_list_for_each (iterator, cgroup_settings) {
                struct lxc_cgroup *cg = iterator->elem;
                int ret;

                if (strncmp("devices", cg->subsystem, 7) == 0)
                        ret = bpf_device_cgroup_prepare(ops, conf, cg->subsystem, cg->value);
                else
                        ret = lxc_write_openat(h->container_limit_path, cg->subsystem, cg->value, strlen(cg->value));
                if (ret < 0)
                        return log_error_errno(false, errno, "Failed to set \"%s\" to \"%s\"", cg->subsystem, cg->value);

                TRACE("Set \"%s\" to \"%s\"", cg->subsystem, cg->value);
        }

        return log_info(true, "Limits for the unified cgroup hierarchy have been setup");
}

__cgfsng_ops static bool cgfsng_devices_activate(struct cgroup_ops *ops, struct lxc_handler *handler)
{
#ifdef HAVE_STRUCT_BPF_CGROUP_DEV_CTX
        __do_bpf_program_free struct bpf_program *prog = NULL;
        int ret;
        struct lxc_conf *conf;
        struct hierarchy *unified;
        struct lxc_list *it;
        struct bpf_program *prog_old;

        if (!ops)
                return ret_set_errno(false, ENOENT);

        if (!ops->hierarchies)
                return true;

        if (!ops->container_cgroup)
                return ret_set_errno(false, EEXIST);

        if (!handler || !handler->conf)
                return ret_set_errno(false, EINVAL);
        conf = handler->conf;

        unified = ops->unified;
        if (!unified || !unified->bpf_device_controller ||
            !unified->container_full_path || lxc_list_empty(&conf->devices))
                return true;

        prog = bpf_program_new(BPF_PROG_TYPE_CGROUP_DEVICE);
        if (!prog)
                return log_error_errno(false, ENOMEM, "Failed to create new bpf program");

        ret = bpf_program_init(prog);
        if (ret)
                return log_error_errno(false, ENOMEM, "Failed to initialize bpf program");

        lxc_list_for_each(it, &conf->devices) {
                struct device_item *cur = it->elem;

                ret = bpf_program_append_device(prog, cur);
                if (ret)
                        return log_error_errno(false, ENOMEM, "Failed to add new rule to bpf device program: type %c, major %d, minor %d, access %s, allow %d, global_rule %d",
                                               cur->type,
                                               cur->major,
                                               cur->minor,
                                               cur->access,
                                               cur->allow,
                                               cur->global_rule);
                TRACE("Added rule to bpf device program: type %c, major %d, minor %d, access %s, allow %d, global_rule %d",
                      cur->type,
                      cur->major,
                      cur->minor,
                      cur->access,
                      cur->allow,
                      cur->global_rule);
        }

        ret = bpf_program_finalize(prog);
        if (ret)
                return log_error_errno(false, ENOMEM, "Failed to finalize bpf program");

        ret = bpf_program_cgroup_attach(prog, BPF_CGROUP_DEVICE,
                                        unified->container_limit_path,
                                        BPF_F_ALLOW_MULTI);
        if (ret)
                return log_error_errno(false, ENOMEM, "Failed to attach bpf program");

        /* Replace old bpf program. */
        prog_old = move_ptr(ops->cgroup2_devices);
        ops->cgroup2_devices = move_ptr(prog);
        prog = move_ptr(prog_old);
#endif
        return true;
}

static bool __cgfsng_delegate_controllers(struct cgroup_ops *ops, const char *cgroup)
{
        __do_free char *add_controllers = NULL, *base_path = NULL;
        __do_free_string_list char **parts = NULL;
        struct hierarchy *unified = ops->unified;
        ssize_t parts_len;
        char **it;
        size_t full_len = 0;

        if (!ops->hierarchies || !pure_unified_layout(ops) ||
            !unified->controllers[0])
                return true;

        /* For now we simply enable all controllers that we have detected by
         * creating a string like "+memory +pids +cpu +io".
         * TODO: In the near future we might want to support "-<controller>"
         * etc. but whether supporting semantics like this make sense will need
         * some thinking.
         */
        for (it = unified->controllers; it && *it; it++) {
                full_len += strlen(*it) + 2;
                add_controllers = must_realloc(add_controllers, full_len + 1);

                if (unified->controllers[0] == *it)
                        add_controllers[0] = '\0';

                (void)strlcat(add_controllers, "+", full_len + 1);
                (void)strlcat(add_controllers, *it, full_len + 1);

                if ((it + 1) && *(it + 1))
                        (void)strlcat(add_controllers, " ", full_len + 1);
        }

        parts = lxc_string_split(cgroup, '/');
        if (!parts)
                return false;

        parts_len = lxc_array_len((void **)parts);
        if (parts_len > 0)
                parts_len--;

        base_path = must_make_path(unified->mountpoint, unified->container_base_path, NULL);
        for (ssize_t i = -1; i < parts_len; i++) {
                int ret;
                __do_free char *target = NULL;

                if (i >= 0)
                        base_path = must_append_path(base_path, parts[i], NULL);
                target = must_make_path(base_path, "cgroup.subtree_control", NULL);
                ret = lxc_writeat(-1, target, add_controllers, full_len);
                if (ret < 0)
                        return log_error_errno(false, errno, "Could not enable \"%s\" controllers in the unified cgroup \"%s\"",
                                               add_controllers, target);
                TRACE("Enable \"%s\" controllers in the unified cgroup \"%s\"", add_controllers, target);
        }

        return true;
}

__cgfsng_ops static bool cgfsng_monitor_delegate_controllers(struct cgroup_ops *ops)
{
        if (!ops)
                return ret_set_errno(false, ENOENT);

        return __cgfsng_delegate_controllers(ops, ops->monitor_cgroup);
}

__cgfsng_ops static bool cgfsng_payload_delegate_controllers(struct cgroup_ops *ops)
{
        if (!ops)
                return ret_set_errno(false, ENOENT);

        return __cgfsng_delegate_controllers(ops, ops->container_cgroup);
}

static bool cgroup_use_wants_controllers(const struct cgroup_ops *ops,
                                       char **controllers)
{
        if (!ops->cgroup_use)
                return true;

        for (char **cur_ctrl = controllers; cur_ctrl && *cur_ctrl; cur_ctrl++) {
                bool found = false;

                for (char **cur_use = ops->cgroup_use; cur_use && *cur_use; cur_use++) {
                        if (strcmp(*cur_use, *cur_ctrl) != 0)
                                continue;

                        found = true;
                        break;
                }

                if (found)
                        continue;

                return false;
        }

        return true;
}

static void cg_unified_delegate(char ***delegate)
{
        __do_free char *buf = NULL;
        char *standard[] = {"cgroup.subtree_control", "cgroup.threads", NULL};
        char *token;
        int idx;

        buf = read_file_at(-EBADF, "/sys/kernel/cgroup/delegate");
        if (!buf) {
                for (char **p = standard; p && *p; p++) {
                        idx = append_null_to_list((void ***)delegate);
                        (*delegate)[idx] = must_copy_string(*p);
                }
                SYSWARN("Failed to read /sys/kernel/cgroup/delegate");
                return;
        }

        lxc_iterate_parts(token, buf, " \t\n") {
                /*
                 * We always need to chown this for both cgroup and
                 * cgroup2.
                 */
                if (strcmp(token, "cgroup.procs") == 0)
                        continue;

                idx = append_null_to_list((void ***)delegate);
                (*delegate)[idx] = must_copy_string(token);
        }
}

/* At startup, parse_hierarchies finds all the info we need about cgroup
 * mountpoints and current cgroups, and stores it in @d.
 */
static int cg_hybrid_init(struct cgroup_ops *ops, bool relative, bool unprivileged)
{
        __do_free char *basecginfo = NULL, *line = NULL;
        __do_free_string_list char **klist = NULL, **nlist = NULL;
        __do_fclose FILE *f = NULL;
        int ret;
        size_t len = 0;

        /* Root spawned containers escape the current cgroup, so use init's
         * cgroups as our base in that case.
         */
        if (!relative && (geteuid() == 0))
                basecginfo = read_file_at(-EBADF, "/proc/1/cgroup");
        else
                basecginfo = read_file_at(-EBADF, "/proc/self/cgroup");
        if (!basecginfo)
                return ret_set_errno(-1, ENOMEM);

        ret = get_existing_subsystems(&klist, &nlist);
        if (ret < 0)
                return log_error_errno(-1, errno, "Failed to retrieve available legacy cgroup controllers");

        f = fopen("/proc/self/mountinfo", "re");
        if (!f)
                return log_error_errno(-1, errno, "Failed to open \"/proc/self/mountinfo\"");

        lxc_cgfsng_print_basecg_debuginfo(basecginfo, klist, nlist);

        while (getline(&line, &len, f) != -1) {
                __do_free char *base_cgroup = NULL, *mountpoint = NULL;
                __do_free_string_list char **controller_list = NULL;
                int type;
                bool writeable;
                struct hierarchy *new;

                type = get_cgroup_version(line);
                if (type == 0)
                        continue;

                if (type == CGROUP2_SUPER_MAGIC && ops->unified)
                        continue;

                if (ops->cgroup_layout == CGROUP_LAYOUT_UNKNOWN) {
                        if (type == CGROUP2_SUPER_MAGIC)
                                ops->cgroup_layout = CGROUP_LAYOUT_UNIFIED;
                        else if (type == CGROUP_SUPER_MAGIC)
                                ops->cgroup_layout = CGROUP_LAYOUT_LEGACY;
                } else if (ops->cgroup_layout == CGROUP_LAYOUT_UNIFIED) {
                        if (type == CGROUP_SUPER_MAGIC)
                                ops->cgroup_layout = CGROUP_LAYOUT_HYBRID;
                } else if (ops->cgroup_layout == CGROUP_LAYOUT_LEGACY) {
                        if (type == CGROUP2_SUPER_MAGIC)
                                ops->cgroup_layout = CGROUP_LAYOUT_HYBRID;
                }

                controller_list = cg_hybrid_get_controllers(klist, nlist, line, type);
                if (!controller_list && type == CGROUP_SUPER_MAGIC)
                        continue;

                if (type == CGROUP_SUPER_MAGIC)
                        if (controller_list_is_dup(ops->hierarchies, controller_list)) {
                                TRACE("Skipping duplicating controller");
                                continue;
                        }

                mountpoint = cg_hybrid_get_mountpoint(line);
                if (!mountpoint) {
                        WARN("Failed parsing mountpoint from \"%s\"", line);
                        continue;
                }

                if (type == CGROUP_SUPER_MAGIC)
                        base_cgroup = cg_hybrid_get_current_cgroup(basecginfo, controller_list[0], CGROUP_SUPER_MAGIC);
                else
                        base_cgroup = cg_hybrid_get_current_cgroup(basecginfo, NULL, CGROUP2_SUPER_MAGIC);
                if (!base_cgroup) {
                        WARN("Failed to find current cgroup");
                        continue;
                }

                trim(base_cgroup);
                prune_init_scope(base_cgroup);
                if (type == CGROUP2_SUPER_MAGIC)
                        writeable = test_writeable_v2(mountpoint, base_cgroup);
                else
                        writeable = test_writeable_v1(mountpoint, base_cgroup);
                if (!writeable) {
                        TRACE("The %s group is not writeable", base_cgroup);
                        continue;
                }

                if (type == CGROUP2_SUPER_MAGIC) {
                        char *cgv2_ctrl_path;

                        cgv2_ctrl_path = must_make_path(mountpoint, base_cgroup,
                                                        "cgroup.controllers",
                                                        NULL);

                        controller_list = cg_unified_get_controllers(-EBADF, cgv2_ctrl_path);
                        free(cgv2_ctrl_path);
                        if (!controller_list) {
                                controller_list = cg_unified_make_empty_controller();
                                TRACE("No controllers are enabled for "
                                      "delegation in the unified hierarchy");
                        }
                }

                /* Exclude all controllers that cgroup use does not want. */
                if (!cgroup_use_wants_controllers(ops, controller_list)) {
                        TRACE("Skipping controller");
                        continue;
                }

                new = add_hierarchy(&ops->hierarchies, move_ptr(controller_list), move_ptr(mountpoint), move_ptr(base_cgroup), type);
                if (!new)
                        return log_error_errno(-1, errno, "Failed to add cgroup hierarchy");
                if (type == CGROUP2_SUPER_MAGIC && !ops->unified) {
                        if (unprivileged)
                                cg_unified_delegate(&new->cgroup2_chown);
                        ops->unified = new;
                }
        }

        TRACE("Writable cgroup hierarchies:");
        lxc_cgfsng_print_hierarchies(ops);

        /* verify that all controllers in cgroup.use and all crucial
         * controllers are accounted for
         */
        if (!all_controllers_found(ops))
                return log_error_errno(-1, ENOENT, "Failed to find all required controllers");

        return 0;
}

/* Get current cgroup from /proc/self/cgroup for the cgroupfs v2 hierarchy. */
static char *cg_unified_get_current_cgroup(bool relative)
{
        __do_free char *basecginfo = NULL;
        char *copy;
        char *base_cgroup;

        if (!relative && (geteuid() == 0))
                basecginfo = read_file_at(-EBADF, "/proc/1/cgroup");
        else
                basecginfo = read_file_at(-EBADF, "/proc/self/cgroup");
        if (!basecginfo)
                return NULL;

        base_cgroup = strstr(basecginfo, "0::/");
        if (!base_cgroup)
                return NULL;

        base_cgroup = base_cgroup + 3;
        copy = copy_to_eol(base_cgroup);
        if (!copy)
                return NULL;

        return trim(copy);
}

static int cg_unified_init(struct cgroup_ops *ops, bool relative,
                           bool unprivileged)
{
        __do_close int cgroup_root_fd = -EBADF;
        __do_free char *base_cgroup = NULL, *controllers_path = NULL;
        __do_free_string_list char **delegatable;
        __do_free struct hierarchy *new = NULL;
        int ret;

        ret = unified_cgroup_hierarchy();
        if (ret == -ENOMEDIUM)
                return ret_errno(ENOMEDIUM);

        if (ret != CGROUP2_SUPER_MAGIC)
                return 0;

        base_cgroup = cg_unified_get_current_cgroup(relative);
        if (!base_cgroup)
                return ret_errno(EINVAL);
        if (!relative)
                prune_init_scope(base_cgroup);

        cgroup_root_fd = openat(-EBADF, DEFAULT_CGROUP_MOUNTPOINT,
                                O_NOCTTY | O_CLOEXEC | O_NOFOLLOW | O_DIRECTORY);
        if (cgroup_root_fd < 0)
                return -errno;

        /*
         * We assume that the cgroup we're currently in has been delegated to
         * us and we are free to further delege all of the controllers listed
         * in cgroup.controllers further down the hierarchy.
         */
        controllers_path = must_make_path_relative(base_cgroup, "cgroup.controllers", NULL);
        delegatable = cg_unified_get_controllers(cgroup_root_fd, controllers_path);
        if (!delegatable)
                delegatable = cg_unified_make_empty_controller();
        if (!delegatable[0])
                TRACE("No controllers are enabled for delegation");

        /* TODO: If the user requested specific controllers via lxc.cgroup.use
         * we should verify here. The reason I'm not doing it right is that I'm
         * not convinced that lxc.cgroup.use will be the future since it is a
         * global property. I much rather have an option that lets you request
         * controllers per container.
         */

        new = add_hierarchy(&ops->hierarchies,
                            move_ptr(delegatable),
                            must_copy_string(DEFAULT_CGROUP_MOUNTPOINT),
                            move_ptr(base_cgroup),
                            CGROUP2_SUPER_MAGIC);
        if (!new)
                return log_error_errno(-1, errno, "Failed to add unified cgroup hierarchy");

        if (unprivileged)
                cg_unified_delegate(&new->cgroup2_chown);

        if (bpf_devices_cgroup_supported())
                new->bpf_device_controller = 1;

        ops->cgroup_layout = CGROUP_LAYOUT_UNIFIED;
        ops->unified = move_ptr(new);

        return CGROUP2_SUPER_MAGIC;
}

static int cg_init(struct cgroup_ops *ops, struct lxc_conf *conf)
{
        int ret;
        const char *tmp;
        bool relative = conf->cgroup_meta.relative;

        tmp = lxc_global_config_value("lxc.cgroup.use");
        if (tmp) {
                __do_free char *pin = NULL;
                char *chop, *cur;

                pin = must_copy_string(tmp);
                chop = pin;

                lxc_iterate_parts(cur, chop, ",")
                        must_append_string(&ops->cgroup_use, cur);
        }

        ret = cg_unified_init(ops, relative, !lxc_list_empty(&conf->id_map));
        if (ret < 0)
                return -1;

        if (ret == CGROUP2_SUPER_MAGIC)
                return 0;

        return cg_hybrid_init(ops, relative, !lxc_list_empty(&conf->id_map));
}

__cgfsng_ops static int cgfsng_data_init(struct cgroup_ops *ops)
{
        const char *cgroup_pattern;

        if (!ops)
                return ret_set_errno(-1, ENOENT);

        /* copy system-wide cgroup information */
        cgroup_pattern = lxc_global_config_value("lxc.cgroup.pattern");
        if (cgroup_pattern && strcmp(cgroup_pattern, "") != 0)
                ops->cgroup_pattern = must_copy_string(cgroup_pattern);

        return 0;
}

struct cgroup_ops *cgfsng_ops_init(struct lxc_conf *conf)
{
        __do_free struct cgroup_ops *cgfsng_ops = NULL;

        cgfsng_ops = zalloc(sizeof(struct cgroup_ops));
        if (!cgfsng_ops)
                return ret_set_errno(NULL, ENOMEM);

        cgfsng_ops->cgroup_layout = CGROUP_LAYOUT_UNKNOWN;

        if (cg_init(cgfsng_ops, conf))
                return NULL;

        cgfsng_ops->data_init                           = cgfsng_data_init;
        cgfsng_ops->payload_destroy                     = cgfsng_payload_destroy;
        cgfsng_ops->monitor_destroy                     = cgfsng_monitor_destroy;
        cgfsng_ops->monitor_create                      = cgfsng_monitor_create;
        cgfsng_ops->monitor_enter                       = cgfsng_monitor_enter;
        cgfsng_ops->monitor_delegate_controllers        = cgfsng_monitor_delegate_controllers;
        cgfsng_ops->payload_delegate_controllers        = cgfsng_payload_delegate_controllers;
        cgfsng_ops->payload_create                      = cgfsng_payload_create;
        cgfsng_ops->payload_enter                       = cgfsng_payload_enter;
        cgfsng_ops->payload_finalize                    = cgfsng_payload_finalize;
        cgfsng_ops->escape                              = cgfsng_escape;
        cgfsng_ops->num_hierarchies                     = cgfsng_num_hierarchies;
        cgfsng_ops->get_hierarchies                     = cgfsng_get_hierarchies;
        cgfsng_ops->get_cgroup                          = cgfsng_get_cgroup;
        cgfsng_ops->get                                 = cgfsng_get;
        cgfsng_ops->set                                 = cgfsng_set;
        cgfsng_ops->freeze                              = cgfsng_freeze;
        cgfsng_ops->unfreeze                            = cgfsng_unfreeze;
        cgfsng_ops->setup_limits_legacy                 = cgfsng_setup_limits_legacy;
        cgfsng_ops->setup_limits                        = cgfsng_setup_limits;
        cgfsng_ops->driver                              = "cgfsng";
        cgfsng_ops->version                             = "1.0.0";
        cgfsng_ops->attach                              = cgfsng_attach;
        cgfsng_ops->chown                               = cgfsng_chown;
        cgfsng_ops->mount                               = cgfsng_mount;
        cgfsng_ops->devices_activate                    = cgfsng_devices_activate;
        cgfsng_ops->get_limiting_cgroup                 = cgfsng_get_limiting_cgroup;

        return move_ptr(cgfsng_ops);
}