src/nspawn/nspawn-cgroup.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <sys/mount.h>
   4
   5 #include "alloc-util.h"
   6 #include "cgroup-setup.h"
   7 #include "fd-util.h"
   8 #include "fileio.h"
   9 #include "format-util.h"
  10 #include "fs-util.h"
  11 #include "mkdir.h"
  12 #include "mount-util.h"
  13 #include "mountpoint-util.h"
  14 #include "nspawn-cgroup.h"
  15 #include "nspawn-mount.h"
  16 #include "path-util.h"
  17 #include "rm-rf.h"
  18 #include "string-util.h"
  19 #include "strv.h"
  20 #include "user-util.h"
  21 #include "util.h"
  22
  23 static int chown_cgroup_path(const char *path, uid_t uid_shift) {
  24         _cleanup_close_ int fd = -1;
  25         const char *fn;
  26
  27         fd = open(path, O_RDONLY|O_CLOEXEC|O_DIRECTORY);
  28         if (fd < 0)
  29                 return -errno;
  30
  31         FOREACH_STRING(fn,
  32                        ".",
  33                        "cgroup.clone_children",
  34                        "cgroup.controllers",
  35                        "cgroup.events",
  36                        "cgroup.procs",
  37                        "cgroup.stat",
  38                        "cgroup.subtree_control",
  39                        "cgroup.threads",
  40                        "notify_on_release",
  41                        "tasks")
  42                 if (fchownat(fd, fn, uid_shift, uid_shift, 0) < 0)
  43                         log_full_errno(errno == ENOENT ? LOG_DEBUG :  LOG_WARNING, errno,
  44                                        "Failed to chown \"%s/%s\", ignoring: %m", path, fn);
  45
  46         return 0;
  47 }
  48
  49 int chown_cgroup(pid_t pid, CGroupUnified unified_requested, uid_t uid_shift) {
  50         _cleanup_free_ char *path = NULL, *fs = NULL;
  51         int r;
  52
  53         r = cg_pid_get_path(NULL, pid, &path);
  54         if (r < 0)
  55                 return log_error_errno(r, "Failed to get container cgroup path: %m");
  56
  57         r = cg_get_path(SYSTEMD_CGROUP_CONTROLLER, path, NULL, &fs);
  58         if (r < 0)
  59                 return log_error_errno(r, "Failed to get file system path for container cgroup: %m");
  60
  61         r = chown_cgroup_path(fs, uid_shift);
  62         if (r < 0)
  63                 return log_error_errno(r, "Failed to chown() cgroup %s: %m", fs);
  64
  65         if (unified_requested == CGROUP_UNIFIED_SYSTEMD || (unified_requested == CGROUP_UNIFIED_NONE && cg_unified_controller(SYSTEMD_CGROUP_CONTROLLER) > 0)) {
  66                 _cleanup_free_ char *lfs = NULL;
  67                 /* Always propagate access rights from unified to legacy controller */
  68
  69                 r = cg_get_path(SYSTEMD_CGROUP_CONTROLLER_LEGACY, path, NULL, &lfs);
  70                 if (r < 0)
  71                         return log_error_errno(r, "Failed to get file system path for container cgroup: %m");
  72
  73                 r = chown_cgroup_path(lfs, uid_shift);
  74                 if (r < 0)
  75                         return log_error_errno(r, "Failed to chown() cgroup %s: %m", lfs);
  76         }
  77
  78         return 0;
  79 }
  80
  81 int sync_cgroup(pid_t pid, CGroupUnified unified_requested, uid_t uid_shift) {
  82         _cleanup_free_ char *cgroup = NULL;
  83         char tree[] = "/tmp/unifiedXXXXXX", pid_string[DECIMAL_STR_MAX(pid) + 1];
  84         bool undo_mount = false;
  85         const char *fn;
  86         int r, unified_controller;
  87
  88         unified_controller = cg_unified_controller(SYSTEMD_CGROUP_CONTROLLER);
  89         if (unified_controller < 0)
  90                 return log_error_errno(unified_controller, "Failed to determine whether the systemd hierarchy is unified: %m");
  91         if ((unified_controller > 0) == (unified_requested >= CGROUP_UNIFIED_SYSTEMD))
  92                 return 0;
  93
  94         /* When the host uses the legacy cgroup setup, but the
  95          * container shall use the unified hierarchy, let's make sure
  96          * we copy the path from the name=systemd hierarchy into the
  97          * unified hierarchy. Similar for the reverse situation. */
  98
  99         r = cg_pid_get_path(SYSTEMD_CGROUP_CONTROLLER, pid, &cgroup);
 100         if (r < 0)
 101                 return log_error_errno(r, "Failed to get control group of " PID_FMT ": %m", pid);
 102
 103         /* In order to access the unified hierarchy we need to mount it */
 104         if (!mkdtemp(tree))
 105                 return log_error_errno(errno, "Failed to generate temporary mount point for unified hierarchy: %m");
 106
 107         if (unified_controller > 0)
 108                 r = mount_verbose(LOG_ERR, "cgroup", tree, "cgroup",
 109                                   MS_NOSUID|MS_NOEXEC|MS_NODEV, "none,name=systemd,xattr");
 110         else
 111                 r = mount_verbose(LOG_ERR, "cgroup", tree, "cgroup2",
 112                                   MS_NOSUID|MS_NOEXEC|MS_NODEV, NULL);
 113         if (r < 0)
 114                 goto finish;
 115
 116         undo_mount = true;
 117
 118         /* If nspawn dies abruptly the cgroup hierarchy created below
 119          * its unit isn't cleaned up. So, let's remove it
 120          * https://github.com/systemd/systemd/pull/4223#issuecomment-252519810 */
 121         fn = strjoina(tree, cgroup);
 122         (void) rm_rf(fn, REMOVE_ROOT|REMOVE_ONLY_DIRECTORIES);
 123
 124         fn = strjoina(tree, cgroup, "/cgroup.procs");
 125
 126         sprintf(pid_string, PID_FMT, pid);
 127         r = write_string_file(fn, pid_string, WRITE_STRING_FILE_DISABLE_BUFFER|WRITE_STRING_FILE_MKDIR_0755);
 128         if (r < 0) {
 129                 log_error_errno(r, "Failed to move process: %m");
 130                 goto finish;
 131         }
 132
 133         fn = strjoina(tree, cgroup);
 134         r = chown_cgroup_path(fn, uid_shift);
 135         if (r < 0)
 136                 log_error_errno(r, "Failed to chown() cgroup %s: %m", fn);
 137 finish:
 138         if (undo_mount)
 139                 (void) umount_verbose(tree);
 140
 141         (void) rmdir(tree);
 142         return r;
 143 }
 144
 145 int create_subcgroup(pid_t pid, bool keep_unit, CGroupUnified unified_requested) {
 146         _cleanup_free_ char *cgroup = NULL;
 147         CGroupMask supported;
 148         const char *payload;
 149         int r;
 150
 151         assert(pid > 1);
 152
 153         /* In the unified hierarchy inner nodes may only contain subgroups, but not processes. Hence, if we running in
 154          * the unified hierarchy and the container does the same, and we did not create a scope unit for the container
 155          * move us and the container into two separate subcgroups.
 156          *
 157          * Moreover, container payloads such as systemd try to manage the cgroup they run in in full (i.e. including
 158          * its attributes), while the host systemd will only delegate cgroups for children of the cgroup created for a
 159          * delegation unit, instead of the cgroup itself. This means, if we'd pass on the cgroup allocated from the
 160          * host systemd directly to the payload, the host and payload systemd might fight for the cgroup
 161          * attributes. Hence, let's insert an intermediary cgroup to cover that case too.
 162          *
 163          * Note that we only bother with the main hierarchy here, not with any secondary ones. On the unified setup
 164          * that's fine because there's only one hierarchy anyway and controllers are enabled directly on it. On the
 165          * legacy setup, this is fine too, since delegation of controllers is generally not safe there, hence we won't
 166          * do it. */
 167
 168         r = cg_mask_supported(&supported);
 169         if (r < 0)
 170                 return log_error_errno(r, "Failed to determine supported controllers: %m");
 171
 172         if (keep_unit)
 173                 r = cg_pid_get_path(SYSTEMD_CGROUP_CONTROLLER, 0, &cgroup);
 174         else
 175                 r = cg_pid_get_path(SYSTEMD_CGROUP_CONTROLLER, pid, &cgroup);
 176         if (r < 0)
 177                 return log_error_errno(r, "Failed to get our control group: %m");
 178
 179         payload = strjoina(cgroup, "/payload");
 180         r = cg_create_and_attach(SYSTEMD_CGROUP_CONTROLLER, payload, pid);
 181         if (r < 0)
 182                 return log_error_errno(r, "Failed to create %s subcgroup: %m", payload);
 183
 184         if (keep_unit) {
 185                 const char *supervisor;
 186
 187                 supervisor = strjoina(cgroup, "/supervisor");
 188                 r = cg_create_and_attach(SYSTEMD_CGROUP_CONTROLLER, supervisor, 0);
 189                 if (r < 0)
 190                         return log_error_errno(r, "Failed to create %s subcgroup: %m", supervisor);
 191         }
 192
 193         /* Try to enable as many controllers as possible for the new payload. */
 194         (void) cg_enable_everywhere(supported, supported, cgroup, NULL);
 195         return 0;
 196 }
 197
 198 /* Retrieve existing subsystems. This function is called in a new cgroup
 199  * namespace.
 200  */
 201 static int get_process_controllers(Set **ret) {
 202         _cleanup_set_free_ Set *controllers = NULL;
 203         _cleanup_fclose_ FILE *f = NULL;
 204         int r;
 205
 206         assert(ret);
 207
 208         f = fopen("/proc/self/cgroup", "re");
 209         if (!f)
 210                 return errno == ENOENT ? -ESRCH : -errno;
 211
 212         for (;;) {
 213                 _cleanup_free_ char *line = NULL;
 214                 char *e, *l;
 215
 216                 r = read_line(f, LONG_LINE_MAX, &line);
 217                 if (r < 0)
 218                         return r;
 219                 if (r == 0)
 220                         break;
 221
 222                 l = strchr(line, ':');
 223                 if (!l)
 224                         continue;
 225
 226                 l++;
 227                 e = strchr(l, ':');
 228                 if (!e)
 229                         continue;
 230
 231                 *e = 0;
 232
 233                 if (STR_IN_SET(l, "", "name=systemd", "name=unified"))
 234                         continue;
 235
 236                 r = set_put_strdup(&controllers, l);
 237                 if (r < 0)
 238                         return r;
 239         }
 240
 241         *ret = TAKE_PTR(controllers);
 242
 243         return 0;
 244 }
 245
 246 static int mount_legacy_cgroup_hierarchy(
 247                 const char *dest,
 248                 const char *controller,
 249                 const char *hierarchy,
 250                 bool read_only) {
 251
 252         const char *to, *fstype, *opts;
 253         int r;
 254
 255         to = strjoina(strempty(dest), "/sys/fs/cgroup/", hierarchy);
 256
 257         r = path_is_mount_point(to, dest, 0);
 258         if (r < 0 && r != -ENOENT)
 259                 return log_error_errno(r, "Failed to determine if %s is mounted already: %m", to);
 260         if (r > 0)
 261                 return 0;
 262
 263         (void) mkdir_p(to, 0755);
 264
 265         /* The superblock mount options of the mount point need to be
 266          * identical to the hosts', and hence writable... */
 267         if (streq(controller, SYSTEMD_CGROUP_CONTROLLER_HYBRID)) {
 268                 fstype = "cgroup2";
 269                 opts = NULL;
 270         } else if (streq(controller, SYSTEMD_CGROUP_CONTROLLER_LEGACY)) {
 271                 fstype = "cgroup";
 272                 opts = "none,name=systemd,xattr";
 273         } else {
 274                 fstype = "cgroup";
 275                 opts = controller;
 276         }
 277
 278         r = mount_verbose(LOG_ERR, "cgroup", to, fstype, MS_NOSUID|MS_NOEXEC|MS_NODEV, opts);
 279         if (r < 0)
 280                 return r;
 281
 282         /* ... hence let's only make the bind mount read-only, not the superblock. */
 283         if (read_only) {
 284                 r = mount_verbose(LOG_ERR, NULL, to, NULL,
 285                                   MS_BIND|MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_RDONLY, NULL);
 286                 if (r < 0)
 287                         return r;
 288         }
 289
 290         return 1;
 291 }
 292
 293 /* Mount a legacy cgroup hierarchy when cgroup namespaces are supported. */
 294 static int mount_legacy_cgns_supported(
 295                 const char *dest,
 296                 CGroupUnified unified_requested,
 297                 bool userns,
 298                 uid_t uid_shift,
 299                 uid_t uid_range,
 300                 const char *selinux_apifs_context) {
 301
 302         _cleanup_set_free_ Set *controllers = NULL;
 303         const char *cgroup_root = "/sys/fs/cgroup", *c;
 304         int r;
 305
 306         (void) mkdir_p(cgroup_root, 0755);
 307
 308         /* Mount a tmpfs to /sys/fs/cgroup if it's not mounted there yet. */
 309         r = path_is_mount_point(cgroup_root, dest, AT_SYMLINK_FOLLOW);
 310         if (r < 0)
 311                 return log_error_errno(r, "Failed to determine if /sys/fs/cgroup is already mounted: %m");
 312         if (r == 0) {
 313                 _cleanup_free_ char *options = NULL;
 314
 315                 /* When cgroup namespaces are enabled and user namespaces are
 316                  * used then the mount of the cgroupfs is done *inside* the new
 317                  * user namespace. We're root in the new user namespace and the
 318                  * kernel will happily translate our uid/gid to the correct
 319                  * uid/gid as seen from e.g. /proc/1/mountinfo. So we simply
 320                  * pass uid 0 and not uid_shift to tmpfs_patch_options().
 321                  */
 322                 r = tmpfs_patch_options("mode=755" TMPFS_LIMITS_SYS_FS_CGROUP, 0, selinux_apifs_context, &options);
 323                 if (r < 0)
 324                         return log_oom();
 325
 326                 r = mount_verbose(LOG_ERR, "tmpfs", cgroup_root, "tmpfs",
 327                                   MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME, options);
 328                 if (r < 0)
 329                         return r;
 330         }
 331
 332         r = cg_all_unified();
 333         if (r < 0)
 334                 return r;
 335         if (r > 0)
 336                 goto skip_controllers;
 337
 338         r = get_process_controllers(&controllers);
 339         if (r < 0)
 340                 return log_error_errno(r, "Failed to determine cgroup controllers: %m");
 341
 342         for (;;) {
 343                 _cleanup_free_ const char *controller = NULL;
 344
 345                 controller = set_steal_first(controllers);
 346                 if (!controller)
 347                         break;
 348
 349                 r = mount_legacy_cgroup_hierarchy("", controller, controller, !userns);
 350                 if (r < 0)
 351                         return r;
 352
 353                 /* When multiple hierarchies are co-mounted, make their
 354                  * constituting individual hierarchies a symlink to the
 355                  * co-mount.
 356                  */
 357                 c = controller;
 358                 for (;;) {
 359                         _cleanup_free_ char *target = NULL, *tok = NULL;
 360
 361                         r = extract_first_word(&c, &tok, ",", 0);
 362                         if (r < 0)
 363                                 return log_error_errno(r, "Failed to extract co-mounted cgroup controller: %m");
 364                         if (r == 0)
 365                                 break;
 366
 367                         if (streq(controller, tok))
 368                                 break;
 369
 370                         target = path_join("/sys/fs/cgroup/", tok);
 371                         if (!target)
 372                                 return log_oom();
 373
 374                         r = symlink_idempotent(controller, target, false);
 375                         if (r == -EINVAL)
 376                                 return log_error_errno(r, "Invalid existing symlink for combined hierarchy: %m");
 377                         if (r < 0)
 378                                 return log_error_errno(r, "Failed to create symlink for combined hierarchy: %m");
 379                 }
 380         }
 381
 382 skip_controllers:
 383         if (unified_requested >= CGROUP_UNIFIED_SYSTEMD) {
 384                 r = mount_legacy_cgroup_hierarchy("", SYSTEMD_CGROUP_CONTROLLER_HYBRID, "unified", false);
 385                 if (r < 0)
 386                         return r;
 387         }
 388
 389         r = mount_legacy_cgroup_hierarchy("", SYSTEMD_CGROUP_CONTROLLER_LEGACY, "systemd", false);
 390         if (r < 0)
 391                 return r;
 392
 393         if (!userns)
 394                 return mount_verbose(LOG_ERR, NULL, cgroup_root, NULL,
 395                                      MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME|MS_RDONLY, "mode=755");
 396
 397         return 0;
 398 }
 399
 400 /* Mount legacy cgroup hierarchy when cgroup namespaces are unsupported. */
 401 static int mount_legacy_cgns_unsupported(
 402                 const char *dest,
 403                 CGroupUnified unified_requested,
 404                 bool userns,
 405                 uid_t uid_shift,
 406                 uid_t uid_range,
 407                 const char *selinux_apifs_context) {
 408
 409         _cleanup_set_free_free_ Set *controllers = NULL;
 410         const char *cgroup_root;
 411         int r;
 412
 413         cgroup_root = prefix_roota(dest, "/sys/fs/cgroup");
 414
 415         (void) mkdir_p(cgroup_root, 0755);
 416
 417         /* Mount a tmpfs to /sys/fs/cgroup if it's not mounted there yet. */
 418         r = path_is_mount_point(cgroup_root, dest, AT_SYMLINK_FOLLOW);
 419         if (r < 0)
 420                 return log_error_errno(r, "Failed to determine if /sys/fs/cgroup is already mounted: %m");
 421         if (r == 0) {
 422                 _cleanup_free_ char *options = NULL;
 423
 424                 r = tmpfs_patch_options("mode=755" TMPFS_LIMITS_SYS_FS_CGROUP, uid_shift == 0 ? UID_INVALID : uid_shift, selinux_apifs_context, &options);
 425                 if (r < 0)
 426                         return log_oom();
 427
 428                 r = mount_verbose(LOG_ERR, "tmpfs", cgroup_root, "tmpfs",
 429                                   MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME, options);
 430                 if (r < 0)
 431                         return r;
 432         }
 433
 434         r = cg_all_unified();
 435         if (r < 0)
 436                 return r;
 437         if (r > 0)
 438                 goto skip_controllers;
 439
 440         r = cg_kernel_controllers(&controllers);
 441         if (r < 0)
 442                 return log_error_errno(r, "Failed to determine cgroup controllers: %m");
 443
 444         for (;;) {
 445                 _cleanup_free_ char *controller = NULL, *origin = NULL, *combined = NULL;
 446
 447                 controller = set_steal_first(controllers);
 448                 if (!controller)
 449                         break;
 450
 451                 origin = path_join("/sys/fs/cgroup/", controller);
 452                 if (!origin)
 453                         return log_oom();
 454
 455                 r = readlink_malloc(origin, &combined);
 456                 if (r == -EINVAL) {
 457                         /* Not a symbolic link, but directly a single cgroup hierarchy */
 458
 459                         r = mount_legacy_cgroup_hierarchy(dest, controller, controller, true);
 460                         if (r < 0)
 461                                 return r;
 462
 463                 } else if (r < 0)
 464                         return log_error_errno(r, "Failed to read link %s: %m", origin);
 465                 else {
 466                         _cleanup_free_ char *target = NULL;
 467
 468                         target = path_join(dest, origin);
 469                         if (!target)
 470                                 return log_oom();
 471
 472                         /* A symbolic link, a combination of controllers in one hierarchy */
 473
 474                         if (!filename_is_valid(combined)) {
 475                                 log_warning("Ignoring invalid combined hierarchy %s.", combined);
 476                                 continue;
 477                         }
 478
 479                         r = mount_legacy_cgroup_hierarchy(dest, combined, combined, true);
 480                         if (r < 0)
 481                                 return r;
 482
 483                         r = symlink_idempotent(combined, target, false);
 484                         if (r == -EINVAL)
 485                                 return log_error_errno(r, "Invalid existing symlink for combined hierarchy: %m");
 486                         if (r < 0)
 487                                 return log_error_errno(r, "Failed to create symlink for combined hierarchy: %m");
 488                 }
 489         }
 490
 491 skip_controllers:
 492         if (unified_requested >= CGROUP_UNIFIED_SYSTEMD) {
 493                 r = mount_legacy_cgroup_hierarchy(dest, SYSTEMD_CGROUP_CONTROLLER_HYBRID, "unified", false);
 494                 if (r < 0)
 495                         return r;
 496         }
 497
 498         r = mount_legacy_cgroup_hierarchy(dest, SYSTEMD_CGROUP_CONTROLLER_LEGACY, "systemd", false);
 499         if (r < 0)
 500                 return r;
 501
 502         return mount_verbose(LOG_ERR, NULL, cgroup_root, NULL,
 503                              MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME|MS_RDONLY, "mode=755");
 504 }
 505
 506 static int mount_unified_cgroups(const char *dest) {
 507         const char *p;
 508         int r;
 509
 510         assert(dest);
 511
 512         p = prefix_roota(dest, "/sys/fs/cgroup");
 513
 514         (void) mkdir_p(p, 0755);
 515
 516         r = path_is_mount_point(p, dest, AT_SYMLINK_FOLLOW);
 517         if (r < 0)
 518                 return log_error_errno(r, "Failed to determine if %s is mounted already: %m", p);
 519         if (r > 0) {
 520                 p = prefix_roota(dest, "/sys/fs/cgroup/cgroup.procs");
 521                 if (access(p, F_OK) >= 0)
 522                         return 0;
 523                 if (errno != ENOENT)
 524                         return log_error_errno(errno, "Failed to determine if mount point %s contains the unified cgroup hierarchy: %m", p);
 525
 526                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
 527                                        "%s is already mounted but not a unified cgroup hierarchy. Refusing.", p);
 528         }
 529
 530         return mount_verbose(LOG_ERR, "cgroup", p, "cgroup2", MS_NOSUID|MS_NOEXEC|MS_NODEV, NULL);
 531 }
 532
 533 int mount_cgroups(
 534                 const char *dest,
 535                 CGroupUnified unified_requested,
 536                 bool userns,
 537                 uid_t uid_shift,
 538                 uid_t uid_range,
 539                 const char *selinux_apifs_context,
 540                 bool use_cgns) {
 541
 542         if (unified_requested >= CGROUP_UNIFIED_ALL)
 543                 return mount_unified_cgroups(dest);
 544         if (use_cgns)
 545                 return mount_legacy_cgns_supported(dest, unified_requested, userns, uid_shift, uid_range, selinux_apifs_context);
 546
 547         return mount_legacy_cgns_unsupported(dest, unified_requested, userns, uid_shift, uid_range, selinux_apifs_context);
 548 }
 549
 550 static int mount_systemd_cgroup_writable_one(const char *root, const char *own) {
 551         int r;
 552
 553         assert(root);
 554         assert(own);
 555
 556         /* Make our own cgroup a (writable) bind mount */
 557         r = mount_verbose(LOG_ERR, own, own, NULL, MS_BIND, NULL);
 558         if (r < 0)
 559                 return r;
 560
 561         /* And then remount the systemd cgroup root read-only */
 562         return mount_verbose(LOG_ERR, NULL, root, NULL,
 563                              MS_BIND|MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_RDONLY, NULL);
 564 }
 565
 566 int mount_systemd_cgroup_writable(
 567                 const char *dest,
 568                 CGroupUnified unified_requested) {
 569
 570         _cleanup_free_ char *own_cgroup_path = NULL;
 571         const char *root, *own;
 572         int r;
 573
 574         assert(dest);
 575
 576         r = cg_pid_get_path(NULL, 0, &own_cgroup_path);
 577         if (r < 0)
 578                 return log_error_errno(r, "Failed to determine our own cgroup path: %m");
 579
 580         /* If we are living in the top-level, then there's nothing to do... */
 581         if (path_equal(own_cgroup_path, "/"))
 582                 return 0;
 583
 584         if (unified_requested >= CGROUP_UNIFIED_ALL) {
 585
 586                 root = prefix_roota(dest, "/sys/fs/cgroup");
 587                 own = strjoina(root, own_cgroup_path);
 588
 589         } else {
 590
 591                 if (unified_requested >= CGROUP_UNIFIED_SYSTEMD) {
 592                         root = prefix_roota(dest, "/sys/fs/cgroup/unified");
 593                         own = strjoina(root, own_cgroup_path);
 594
 595                         r = mount_systemd_cgroup_writable_one(root, own);
 596                         if (r < 0)
 597                                 return r;
 598                 }
 599
 600                 root = prefix_roota(dest, "/sys/fs/cgroup/systemd");
 601                 own = strjoina(root, own_cgroup_path);
 602         }
 603
 604         return mount_systemd_cgroup_writable_one(root, own);
 605 }