Merge pull request #9658 from LukeShu/to-upstream/misc-cleanup

nspawn: Miscellaneous touch-up

src/basic/cgroup-util.c

@@ -2384,10 +2384,9 @@ int cg_kernel_controllers(Set **ret) {
 
         assert(ret);
 
-        /* Determines the full list of kernel-known controllers. Might
-         * include controllers we don't actually support, arbitrary
-         * named hierarchies and controllers that aren't currently
-         * accessible (because not mounted). */
+        /* Determines the full list of kernel-known controllers. Might include controllers we don't actually support
+         * and controllers that aren't currently accessible (because not mounted). This does not include "name="
+         * pseudo-controllers. */
 
         controllers = set_new(&string_hash_ops);
         if (!controllers)

src/nspawn/nspawn-cgroup.c

@@ -5,12 +5,16 @@
 #include "alloc-util.h"
 #include "fd-util.h"
 #include "fileio.h"
+#include "fs-util.h"
 #include "mkdir.h"
 #include "mount-util.h"
 #include "nspawn-cgroup.h"
+#include "nspawn-mount.h"
+#include "path-util.h"
 #include "rm-rf.h"
 #include "string-util.h"
 #include "strv.h"
+#include "user-util.h"
 #include "util.h"
 
 static int chown_cgroup_path(const char *path, uid_t uid_shift) {
@@ -71,7 +75,7 @@ int chown_cgroup(pid_t pid, CGroupUnified unified_requested, uid_t uid_shift) {
         return 0;
 }
 
-int sync_cgroup(pid_t pid, CGroupUnified unified_requested, uid_t arg_uid_shift) {
+int sync_cgroup(pid_t pid, CGroupUnified unified_requested, uid_t uid_shift) {
         _cleanup_free_ char *cgroup = NULL;
         char tree[] = "/tmp/unifiedXXXXXX", pid_string[DECIMAL_STR_MAX(pid) + 1];
         bool undo_mount = false;
@@ -125,7 +129,7 @@ int sync_cgroup(pid_t pid, CGroupUnified unified_requested, uid_t arg_uid_shift)
         }
 
         fn = strjoina(tree, cgroup);
-        r = chown_cgroup_path(fn, arg_uid_shift);
+        r = chown_cgroup_path(fn, uid_shift);
         if (r < 0)
                 log_error_errno(r, "Failed to chown() cgroup %s: %m", fn);
 finish:
@@ -188,3 +192,416 @@ int create_subcgroup(pid_t pid, bool keep_unit, CGroupUnified unified_requested)
         (void) cg_enable_everywhere(supported, supported, cgroup);
         return 0;
 }
+
+/* Retrieve existing subsystems. This function is called in a new cgroup
+ * namespace.
+ */
+static int get_process_controllers(Set **ret) {
+        _cleanup_set_free_free_ Set *controllers = NULL;
+        _cleanup_fclose_ FILE *f = NULL;
+        int r;
+
+        assert(ret);
+
+        controllers = set_new(&string_hash_ops);
+        if (!controllers)
+                return -ENOMEM;
+
+        f = fopen("/proc/self/cgroup", "re");
+        if (!f)
+                return errno == ENOENT ? -ESRCH : -errno;
+
+        for (;;) {
+                _cleanup_free_ char *line = NULL;
+                char *e, *l;
+
+                r = read_line(f, LONG_LINE_MAX, &line);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        break;
+
+                l = strchr(line, ':');
+                if (!l)
+                        continue;
+
+                l++;
+                e = strchr(l, ':');
+                if (!e)
+                        continue;
+
+                *e = 0;
+
+                if (STR_IN_SET(l, "", "name=systemd", "name=unified"))
+                        continue;
+
+                r = set_put_strdup(controllers, l);
+                if (r < 0)
+                        return r;
+        }
+
+        *ret = TAKE_PTR(controllers);
+
+        return 0;
+}
+
+static int mount_legacy_cgroup_hierarchy(
+                const char *dest,
+                const char *controller,
+                const char *hierarchy,
+                bool read_only) {
+
+        const char *to, *fstype, *opts;
+        int r;
+
+        to = strjoina(strempty(dest), "/sys/fs/cgroup/", hierarchy);
+
+        r = path_is_mount_point(to, dest, 0);
+        if (r < 0 && r != -ENOENT)
+                return log_error_errno(r, "Failed to determine if %s is mounted already: %m", to);
+        if (r > 0)
+                return 0;
+
+        mkdir_p(to, 0755);
+
+        /* The superblock mount options of the mount point need to be
+         * identical to the hosts', and hence writable... */
+        if (streq(controller, SYSTEMD_CGROUP_CONTROLLER_HYBRID)) {
+                fstype = "cgroup2";
+                opts = NULL;
+        } else if (streq(controller, SYSTEMD_CGROUP_CONTROLLER_LEGACY)) {
+                fstype = "cgroup";
+                opts = "none,name=systemd,xattr";
+        } else {
+                fstype = "cgroup";
+                opts = controller;
+        }
+
+        r = mount_verbose(LOG_ERR, "cgroup", to, fstype, MS_NOSUID|MS_NOEXEC|MS_NODEV, opts);
+        if (r < 0)
+                return r;
+
+        /* ... hence let's only make the bind mount read-only, not the superblock. */
+        if (read_only) {
+                r = mount_verbose(LOG_ERR, NULL, to, NULL,
+                                  MS_BIND|MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_RDONLY, NULL);
+                if (r < 0)
+                        return r;
+        }
+
+        return 1;
+}
+
+/* Mount a legacy cgroup hierarchy when cgroup namespaces are supported. */
+static int mount_legacy_cgns_supported(
+                const char *dest,
+                CGroupUnified unified_requested,
+                bool userns,
+                uid_t uid_shift,
+                uid_t uid_range,
+                const char *selinux_apifs_context) {
+
+        _cleanup_set_free_free_ Set *controllers = NULL;
+        const char *cgroup_root = "/sys/fs/cgroup", *c;
+        int r;
+
+        (void) mkdir_p(cgroup_root, 0755);
+
+        /* Mount a tmpfs to /sys/fs/cgroup if it's not mounted there yet. */
+        r = path_is_mount_point(cgroup_root, dest, AT_SYMLINK_FOLLOW);
+        if (r < 0)
+                return log_error_errno(r, "Failed to determine if /sys/fs/cgroup is already mounted: %m");
+        if (r == 0) {
+                _cleanup_free_ char *options = NULL;
+
+                /* When cgroup namespaces are enabled and user namespaces are
+                 * used then the mount of the cgroupfs is done *inside* the new
+                 * user namespace. We're root in the new user namespace and the
+                 * kernel will happily translate our uid/gid to the correct
+                 * uid/gid as seen from e.g. /proc/1/mountinfo. So we simply
+                 * pass uid 0 and not uid_shift to tmpfs_patch_options().
+                 */
+                r = tmpfs_patch_options("mode=755", 0, selinux_apifs_context, &options);
+                if (r < 0)
+                        return log_oom();
+
+                r = mount_verbose(LOG_ERR, "tmpfs", cgroup_root, "tmpfs",
+                                  MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME, options);
+                if (r < 0)
+                        return r;
+        }
+
+        r = cg_all_unified();
+        if (r < 0)
+                return r;
+        if (r > 0)
+                goto skip_controllers;
+
+        r = get_process_controllers(&controllers);
+        if (r < 0)
+                return log_error_errno(r, "Failed to determine cgroup controllers: %m");
+
+        for (;;) {
+                _cleanup_free_ const char *controller = NULL;
+
+                controller = set_steal_first(controllers);
+                if (!controller)
+                        break;
+
+                r = mount_legacy_cgroup_hierarchy("", controller, controller, !userns);
+                if (r < 0)
+                        return r;
+
+                /* When multiple hierarchies are co-mounted, make their
+                 * constituting individual hierarchies a symlink to the
+                 * co-mount.
+                 */
+                c = controller;
+                for (;;) {
+                        _cleanup_free_ char *target = NULL, *tok = NULL;
+
+                        r = extract_first_word(&c, &tok, ",", 0);
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to extract co-mounted cgroup controller: %m");
+                        if (r == 0)
+                                break;
+
+                        if (streq(controller, tok))
+                                break;
+
+                        target = prefix_root("/sys/fs/cgroup/", tok);
+                        if (!target)
+                                return log_oom();
+
+                        r = symlink_idempotent(controller, target);
+                        if (r == -EINVAL)
+                                return log_error_errno(r, "Invalid existing symlink for combined hierarchy: %m");
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to create symlink for combined hierarchy: %m");
+                }
+        }
+
+skip_controllers:
+        if (unified_requested >= CGROUP_UNIFIED_SYSTEMD) {
+                r = mount_legacy_cgroup_hierarchy("", SYSTEMD_CGROUP_CONTROLLER_HYBRID, "unified", false);
+                if (r < 0)
+                        return r;
+        }
+
+        r = mount_legacy_cgroup_hierarchy("", SYSTEMD_CGROUP_CONTROLLER_LEGACY, "systemd", false);
+        if (r < 0)
+                return r;
+
+        if (!userns)
+                return mount_verbose(LOG_ERR, NULL, cgroup_root, NULL,
+                                     MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME|MS_RDONLY, "mode=755");
+
+        return 0;
+}
+
+/* Mount legacy cgroup hierarchy when cgroup namespaces are unsupported. */
+static int mount_legacy_cgns_unsupported(
+                const char *dest,
+                CGroupUnified unified_requested,
+                bool userns,
+                uid_t uid_shift,
+                uid_t uid_range,
+                const char *selinux_apifs_context) {
+
+        _cleanup_set_free_free_ Set *controllers = NULL;
+        const char *cgroup_root;
+        int r;
+
+        cgroup_root = prefix_roota(dest, "/sys/fs/cgroup");
+
+        (void) mkdir_p(cgroup_root, 0755);
+
+        /* Mount a tmpfs to /sys/fs/cgroup if it's not mounted there yet. */
+        r = path_is_mount_point(cgroup_root, dest, AT_SYMLINK_FOLLOW);
+        if (r < 0)
+                return log_error_errno(r, "Failed to determine if /sys/fs/cgroup is already mounted: %m");
+        if (r == 0) {
+                _cleanup_free_ char *options = NULL;
+
+                r = tmpfs_patch_options("mode=755", uid_shift == 0 ? UID_INVALID : uid_shift, selinux_apifs_context, &options);
+                if (r < 0)
+                        return log_oom();
+
+                r = mount_verbose(LOG_ERR, "tmpfs", cgroup_root, "tmpfs",
+                                  MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME, options);
+                if (r < 0)
+                        return r;
+        }
+
+        r = cg_all_unified();
+        if (r < 0)
+                return r;
+        if (r > 0)
+                goto skip_controllers;
+
+        r = cg_kernel_controllers(&controllers);
+        if (r < 0)
+                return log_error_errno(r, "Failed to determine cgroup controllers: %m");
+
+        for (;;) {
+                _cleanup_free_ char *controller = NULL, *origin = NULL, *combined = NULL;
+
+                controller = set_steal_first(controllers);
+                if (!controller)
+                        break;
+
+                origin = prefix_root("/sys/fs/cgroup/", controller);
+                if (!origin)
+                        return log_oom();
+
+                r = readlink_malloc(origin, &combined);
+                if (r == -EINVAL) {
+                        /* Not a symbolic link, but directly a single cgroup hierarchy */
+
+                        r = mount_legacy_cgroup_hierarchy(dest, controller, controller, true);
+                        if (r < 0)
+                                return r;
+
+                } else if (r < 0)
+                        return log_error_errno(r, "Failed to read link %s: %m", origin);
+                else {
+                        _cleanup_free_ char *target = NULL;
+
+                        target = prefix_root(dest, origin);
+                        if (!target)
+                                return log_oom();
+
+                        /* A symbolic link, a combination of controllers in one hierarchy */
+
+                        if (!filename_is_valid(combined)) {
+                                log_warning("Ignoring invalid combined hierarchy %s.", combined);
+                                continue;
+                        }
+
+                        r = mount_legacy_cgroup_hierarchy(dest, combined, combined, true);
+                        if (r < 0)
+                                return r;
+
+                        r = symlink_idempotent(combined, target);
+                        if (r == -EINVAL)
+                                return log_error_errno(r, "Invalid existing symlink for combined hierarchy: %m");
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to create symlink for combined hierarchy: %m");
+                }
+        }
+
+skip_controllers:
+        if (unified_requested >= CGROUP_UNIFIED_SYSTEMD) {
+                r = mount_legacy_cgroup_hierarchy(dest, SYSTEMD_CGROUP_CONTROLLER_HYBRID, "unified", false);
+                if (r < 0)
+                        return r;
+        }
+
+        r = mount_legacy_cgroup_hierarchy(dest, SYSTEMD_CGROUP_CONTROLLER_LEGACY, "systemd", false);
+        if (r < 0)
+                return r;
+
+        return mount_verbose(LOG_ERR, NULL, cgroup_root, NULL,
+                             MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME|MS_RDONLY, "mode=755");
+}
+
+static int mount_unified_cgroups(const char *dest) {
+        const char *p;
+        int r;
+
+        assert(dest);
+
+        p = prefix_roota(dest, "/sys/fs/cgroup");
+
+        (void) mkdir_p(p, 0755);
+
+        r = path_is_mount_point(p, dest, AT_SYMLINK_FOLLOW);
+        if (r < 0)
+                return log_error_errno(r, "Failed to determine if %s is mounted already: %m", p);
+        if (r > 0) {
+                p = prefix_roota(dest, "/sys/fs/cgroup/cgroup.procs");
+                if (access(p, F_OK) >= 0)
+                        return 0;
+                if (errno != ENOENT)
+                        return log_error_errno(errno, "Failed to determine if mount point %s contains the unified cgroup hierarchy: %m", p);
+
+                log_error("%s is already mounted but not a unified cgroup hierarchy. Refusing.", p);
+                return -EINVAL;
+        }
+
+        return mount_verbose(LOG_ERR, "cgroup", p, "cgroup2", MS_NOSUID|MS_NOEXEC|MS_NODEV, NULL);
+}
+
+int mount_cgroups(
+                const char *dest,
+                CGroupUnified unified_requested,
+                bool userns,
+                uid_t uid_shift,
+                uid_t uid_range,
+                const char *selinux_apifs_context,
+                bool use_cgns) {
+
+        if (unified_requested >= CGROUP_UNIFIED_ALL)
+                return mount_unified_cgroups(dest);
+        if (use_cgns)
+                return mount_legacy_cgns_supported(dest, unified_requested, userns, uid_shift, uid_range, selinux_apifs_context);
+
+        return mount_legacy_cgns_unsupported(dest, unified_requested, userns, uid_shift, uid_range, selinux_apifs_context);
+}
+
+static int mount_systemd_cgroup_writable_one(const char *root, const char *own) {
+        int r;
+
+        assert(root);
+        assert(own);
+
+        /* Make our own cgroup a (writable) bind mount */
+        r = mount_verbose(LOG_ERR, own, own, NULL, MS_BIND, NULL);
+        if (r < 0)
+                return r;
+
+        /* And then remount the systemd cgroup root read-only */
+        return mount_verbose(LOG_ERR, NULL, root, NULL,
+                             MS_BIND|MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_RDONLY, NULL);
+}
+
+int mount_systemd_cgroup_writable(
+                const char *dest,
+                CGroupUnified unified_requested) {
+
+        _cleanup_free_ char *own_cgroup_path = NULL;
+        const char *root, *own;
+        int r;
+
+        assert(dest);
+
+        r = cg_pid_get_path(NULL, 0, &own_cgroup_path);
+        if (r < 0)
+                return log_error_errno(r, "Failed to determine our own cgroup path: %m");
+
+        /* If we are living in the top-level, then there's nothing to do... */
+        if (path_equal(own_cgroup_path, "/"))
+                return 0;
+
+        if (unified_requested >= CGROUP_UNIFIED_ALL) {
+
+                root = prefix_roota(dest, "/sys/fs/cgroup");
+                own = strjoina(root, own_cgroup_path);
+
+        } else {
+
+                if (unified_requested >= CGROUP_UNIFIED_SYSTEMD) {
+                        root = prefix_roota(dest, "/sys/fs/cgroup/unified");
+                        own = strjoina(root, own_cgroup_path);
+
+                        r = mount_systemd_cgroup_writable_one(root, own);
+                        if (r < 0)
+                                return r;
+                }
+
+                root = prefix_roota(dest, "/sys/fs/cgroup/systemd");
+                own = strjoina(root, own_cgroup_path);
+        }
+
+        return mount_systemd_cgroup_writable_one(root, own);
+}

src/nspawn/nspawn-cgroup.h

@@ -9,3 +9,6 @@
 int chown_cgroup(pid_t pid, CGroupUnified unified_requested, uid_t uid_shift);
 int sync_cgroup(pid_t pid, CGroupUnified unified_requested, uid_t uid_shift);
 int create_subcgroup(pid_t pid, bool keep_unit, CGroupUnified unified_requested);
+
+int mount_cgroups(const char *dest, CGroupUnified unified_requested, bool userns, uid_t uid_shift, uid_t uid_range, const char *selinux_apifs_context, bool use_cgns);
+int mount_systemd_cgroup_writable(const char *dest, CGroupUnified unified_requested);

src/nspawn/nspawn-mount.c

@@ -327,19 +327,15 @@ int overlay_mount_parse(CustomMount **l, size_t *n, const char *s, bool read_onl
         return 0;
 }
 
-static int tmpfs_patch_options(
+int tmpfs_patch_options(
                 const char *options,
-                bool userns,
-                uid_t uid_shift, uid_t uid_range,
-                bool patch_ids,
+                uid_t uid_shift,
                 const char *selinux_apifs_context,
                 char **ret) {
 
         char *buf = NULL;
 
-        if ((userns && uid_shift != 0) || patch_ids) {
-                assert(uid_shift != UID_INVALID);
-
+        if (uid_shift != UID_INVALID) {
                 if (asprintf(&buf, "%s%suid=" UID_FMT ",gid=" UID_FMT,
                              strempty(options), options ? "," : "",
                              uid_shift, uid_shift) < 0)
@@ -433,16 +429,14 @@ int mount_sysfs(const char *dest, MountSettingsMask mount_settings) {
         /* Create mountpoint for cgroups. Otherwise we are not allowed since we
          * remount /sys read-only.
          */
-        if (cg_ns_supported()) {
-                x = prefix_roota(top, "/fs/cgroup");
-                (void) mkdir_p(x, 0755);
-        }
+        x = prefix_roota(top, "/fs/cgroup");
+        (void) mkdir_p(x, 0755);
 
         return mount_verbose(LOG_ERR, NULL, top, NULL,
                              MS_BIND|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_REMOUNT|extra_flags, NULL);
 }
 
-static int mkdir_userns(const char *path, mode_t mode, MountSettingsMask mask, uid_t uid_shift) {
+static int mkdir_userns(const char *path, mode_t mode, uid_t uid_shift) {
         int r;
 
         assert(path);
@@ -451,10 +445,7 @@ static int mkdir_userns(const char *path, mode_t mode, MountSettingsMask mask, u
         if (r < 0 && r != -EEXIST)
                 return r;
 
-        if ((mask & MOUNT_USE_USERNS) == 0)
-                return 0;
-
-        if (mask & MOUNT_IN_USERNS)
+        if (uid_shift == UID_INVALID)
                 return 0;
 
         if (lchown(path, uid_shift, uid_shift) < 0)
@@ -463,7 +454,7 @@ static int mkdir_userns(const char *path, mode_t mode, MountSettingsMask mask, u
         return 0;
 }
 
-static int mkdir_userns_p(const char *prefix, const char *path, mode_t mode, MountSettingsMask mask, uid_t uid_shift) {
+static int mkdir_userns_p(const char *prefix, const char *path, mode_t mode, uid_t uid_shift) {
         const char *p, *e;
         int r;
 
@@ -490,17 +481,17 @@ static int mkdir_userns_p(const char *prefix, const char *path, mode_t mode, Mou
                 if (prefix && path_startswith(prefix, t))
                         continue;
 
-                r = mkdir_userns(t, mode, mask, uid_shift);
+                r = mkdir_userns(t, mode, uid_shift);
                 if (r < 0)
                         return r;
         }
 
-        return mkdir_userns(path, mode, mask, uid_shift);
+        return mkdir_userns(path, mode, uid_shift);
 }
 
 int mount_all(const char *dest,
               MountSettingsMask mount_settings,
-              uid_t uid_shift, uid_t uid_range,
+              uid_t uid_shift,
               const char *selinux_apifs_context) {
 
 #define PROC_INACCESSIBLE(path)                                         \
@@ -634,7 +625,7 @@ int mount_all(const char *dest,
                 if (what && r > 0)
                         continue;
 
-                r = mkdir_userns_p(dest, where, 0755, mount_settings, uid_shift);
+                r = mkdir_userns_p(dest, where, 0755, (use_userns && !in_userns) ? uid_shift : UID_INVALID);
                 if (r < 0 && r != -EEXIST) {
                         if (fatal && r != -EROFS)
                                 return log_error_errno(r, "Failed to create directory %s: %m", where);
@@ -649,10 +640,7 @@ int mount_all(const char *dest,
 
                 o = mount_table[k].options;
                 if (streq_ptr(mount_table[k].type, "tmpfs")) {
-                        if (in_userns)
-                                r = tmpfs_patch_options(o, use_userns, 0, uid_range, true, selinux_apifs_context, &options);
-                        else
-                                r = tmpfs_patch_options(o, use_userns, uid_shift, uid_range, false, selinux_apifs_context, &options);
+                        r = tmpfs_patch_options(o, in_userns ? 0 : uid_shift, selinux_apifs_context, &options);
                         if (r < 0)
                                 return log_oom();
                         if (r > 0)
@@ -755,7 +743,7 @@ static int mount_tmpfs(
                         return log_error_errno(r, "Creating mount point for tmpfs %s failed: %m", where);
         }
 
-        r = tmpfs_patch_options(m->options, userns, uid_shift, uid_range, false, selinux_apifs_context, &buf);
+        r = tmpfs_patch_options(m->options, uid_shift == 0 ? UID_INVALID : uid_shift, selinux_apifs_context, &buf);
         if (r < 0)
                 return log_oom();
         options = r > 0 ? buf : m->options;
@@ -860,419 +848,6 @@ int mount_custom(
         return 0;
 }
 
-/* Retrieve existing subsystems. This function is called in a new cgroup
- * namespace.
- */
-static int get_process_controllers(Set **ret) {
-        _cleanup_set_free_free_ Set *controllers = NULL;
-        _cleanup_fclose_ FILE *f = NULL;
-        int r;
-
-        assert(ret);
-
-        controllers = set_new(&string_hash_ops);
-        if (!controllers)
-                return -ENOMEM;
-
-        f = fopen("/proc/self/cgroup", "re");
-        if (!f)
-                return errno == ENOENT ? -ESRCH : -errno;
-
-        for (;;) {
-                _cleanup_free_ char *line = NULL;
-                char *e, *l;
-
-                r = read_line(f, LONG_LINE_MAX, &line);
-                if (r < 0)
-                        return r;
-                if (r == 0)
-                        break;
-
-                l = strchr(line, ':');
-                if (!l)
-                        continue;
-
-                l++;
-                e = strchr(l, ':');
-                if (!e)
-                        continue;
-
-                *e = 0;
-
-                if (STR_IN_SET(l, "", "name=systemd", "name=unified"))
-                        continue;
-
-                r = set_put_strdup(controllers, l);
-                if (r < 0)
-                        return r;
-        }
-
-        *ret = TAKE_PTR(controllers);
-
-        return 0;
-}
-
-static int mount_legacy_cgroup_hierarchy(
-                const char *dest,
-                const char *controller,
-                const char *hierarchy,
-                bool read_only) {
-
-        const char *to, *fstype, *opts;
-        int r;
-
-        to = strjoina(strempty(dest), "/sys/fs/cgroup/", hierarchy);
-
-        r = path_is_mount_point(to, dest, 0);
-        if (r < 0 && r != -ENOENT)
-                return log_error_errno(r, "Failed to determine if %s is mounted already: %m", to);
-        if (r > 0)
-                return 0;
-
-        mkdir_p(to, 0755);
-
-        /* The superblock mount options of the mount point need to be
-         * identical to the hosts', and hence writable... */
-        if (streq(controller, SYSTEMD_CGROUP_CONTROLLER_HYBRID)) {
-                fstype = "cgroup2";
-                opts = NULL;
-        } else if (streq(controller, SYSTEMD_CGROUP_CONTROLLER_LEGACY)) {
-                fstype = "cgroup";
-                opts = "none,name=systemd,xattr";
-        } else {
-                fstype = "cgroup";
-                opts = controller;
-        }
-
-        r = mount_verbose(LOG_ERR, "cgroup", to, fstype, MS_NOSUID|MS_NOEXEC|MS_NODEV, opts);
-        if (r < 0)
-                return r;
-
-        /* ... hence let's only make the bind mount read-only, not the superblock. */
-        if (read_only) {
-                r = mount_verbose(LOG_ERR, NULL, to, NULL,
-                                  MS_BIND|MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_RDONLY, NULL);
-                if (r < 0)
-                        return r;
-        }
-
-        return 1;
-}
-
-/* Mount a legacy cgroup hierarchy when cgroup namespaces are supported. */
-static int mount_legacy_cgns_supported(
-                const char *dest,
-                CGroupUnified unified_requested,
-                bool userns,
-                uid_t uid_shift,
-                uid_t uid_range,
-                const char *selinux_apifs_context) {
-
-        _cleanup_set_free_free_ Set *controllers = NULL;
-        const char *cgroup_root = "/sys/fs/cgroup", *c;
-        int r;
-
-        (void) mkdir_p(cgroup_root, 0755);
-
-        /* Mount a tmpfs to /sys/fs/cgroup if it's not mounted there yet. */
-        r = path_is_mount_point(cgroup_root, dest, AT_SYMLINK_FOLLOW);
-        if (r < 0)
-                return log_error_errno(r, "Failed to determine if /sys/fs/cgroup is already mounted: %m");
-        if (r == 0) {
-                _cleanup_free_ char *options = NULL;
-
-                /* When cgroup namespaces are enabled and user namespaces are
-                 * used then the mount of the cgroupfs is done *inside* the new
-                 * user namespace. We're root in the new user namespace and the
-                 * kernel will happily translate our uid/gid to the correct
-                 * uid/gid as seen from e.g. /proc/1/mountinfo. So we simply
-                 * pass uid 0 and not uid_shift to tmpfs_patch_options().
-                 */
-                r = tmpfs_patch_options("mode=755", userns, 0, uid_range, true, selinux_apifs_context, &options);
-                if (r < 0)
-                        return log_oom();
-
-                r = mount_verbose(LOG_ERR, "tmpfs", cgroup_root, "tmpfs",
-                                  MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME, options);
-                if (r < 0)
-                        return r;
-        }
-
-        r = cg_all_unified();
-        if (r < 0)
-                return r;
-        if (r > 0)
-                goto skip_controllers;
-
-        r = get_process_controllers(&controllers);
-        if (r < 0)
-                return log_error_errno(r, "Failed to determine cgroup controllers: %m");
-
-        for (;;) {
-                _cleanup_free_ const char *controller = NULL;
-
-                controller = set_steal_first(controllers);
-                if (!controller)
-                        break;
-
-                r = mount_legacy_cgroup_hierarchy("", controller, controller, !userns);
-                if (r < 0)
-                        return r;
-
-                /* When multiple hierarchies are co-mounted, make their
-                 * constituting individual hierarchies a symlink to the
-                 * co-mount.
-                 */
-                c = controller;
-                for (;;) {
-                        _cleanup_free_ char *target = NULL, *tok = NULL;
-
-                        r = extract_first_word(&c, &tok, ",", 0);
-                        if (r < 0)
-                                return log_error_errno(r, "Failed to extract co-mounted cgroup controller: %m");
-                        if (r == 0)
-                                break;
-
-                        if (streq(controller, tok))
-                                break;
-
-                        target = prefix_root("/sys/fs/cgroup/", tok);
-                        if (!target)
-                                return log_oom();
-
-                        r = symlink_idempotent(controller, target);
-                        if (r == -EINVAL)
-                                return log_error_errno(r, "Invalid existing symlink for combined hierarchy: %m");
-                        if (r < 0)
-                                return log_error_errno(r, "Failed to create symlink for combined hierarchy: %m");
-                }
-        }
-
-skip_controllers:
-        if (unified_requested >= CGROUP_UNIFIED_SYSTEMD) {
-                r = mount_legacy_cgroup_hierarchy("", SYSTEMD_CGROUP_CONTROLLER_HYBRID, "unified", false);
-                if (r < 0)
-                        return r;
-        }
-
-        r = mount_legacy_cgroup_hierarchy("", SYSTEMD_CGROUP_CONTROLLER_LEGACY, "systemd", false);
-        if (r < 0)
-                return r;
-
-        if (!userns)
-                return mount_verbose(LOG_ERR, NULL, cgroup_root, NULL,
-                                     MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME|MS_RDONLY, "mode=755");
-
-        return 0;
-}
-
-/* Mount legacy cgroup hierarchy when cgroup namespaces are unsupported. */
-static int mount_legacy_cgns_unsupported(
-                const char *dest,
-                CGroupUnified unified_requested,
-                bool userns,
-                uid_t uid_shift,
-                uid_t uid_range,
-                const char *selinux_apifs_context) {
-
-        _cleanup_set_free_free_ Set *controllers = NULL;
-        const char *cgroup_root;
-        int r;
-
-        cgroup_root = prefix_roota(dest, "/sys/fs/cgroup");
-
-        (void) mkdir_p(cgroup_root, 0755);
-
-        /* Mount a tmpfs to /sys/fs/cgroup if it's not mounted there yet. */
-        r = path_is_mount_point(cgroup_root, dest, AT_SYMLINK_FOLLOW);
-        if (r < 0)
-                return log_error_errno(r, "Failed to determine if /sys/fs/cgroup is already mounted: %m");
-        if (r == 0) {
-                _cleanup_free_ char *options = NULL;
-
-                r = tmpfs_patch_options("mode=755", userns, uid_shift, uid_range, false, selinux_apifs_context, &options);
-                if (r < 0)
-                        return log_oom();
-
-                r = mount_verbose(LOG_ERR, "tmpfs", cgroup_root, "tmpfs",
-                                  MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME, options);
-                if (r < 0)
-                        return r;
-        }
-
-        r = cg_all_unified();
-        if (r < 0)
-                return r;
-        if (r > 0)
-                goto skip_controllers;
-
-        r = cg_kernel_controllers(&controllers);
-        if (r < 0)
-                return log_error_errno(r, "Failed to determine cgroup controllers: %m");
-
-        for (;;) {
-                _cleanup_free_ char *controller = NULL, *origin = NULL, *combined = NULL;
-
-                controller = set_steal_first(controllers);
-                if (!controller)
-                        break;
-
-                origin = prefix_root("/sys/fs/cgroup/", controller);
-                if (!origin)
-                        return log_oom();
-
-                r = readlink_malloc(origin, &combined);
-                if (r == -EINVAL) {
-                        /* Not a symbolic link, but directly a single cgroup hierarchy */
-
-                        r = mount_legacy_cgroup_hierarchy(dest, controller, controller, true);
-                        if (r < 0)
-                                return r;
-
-                } else if (r < 0)
-                        return log_error_errno(r, "Failed to read link %s: %m", origin);
-                else {
-                        _cleanup_free_ char *target = NULL;
-
-                        target = prefix_root(dest, origin);
-                        if (!target)
-                                return log_oom();
-
-                        /* A symbolic link, a combination of controllers in one hierarchy */
-
-                        if (!filename_is_valid(combined)) {
-                                log_warning("Ignoring invalid combined hierarchy %s.", combined);
-                                continue;
-                        }
-
-                        r = mount_legacy_cgroup_hierarchy(dest, combined, combined, true);
-                        if (r < 0)
-                                return r;
-
-                        r = symlink_idempotent(combined, target);
-                        if (r == -EINVAL)
-                                return log_error_errno(r, "Invalid existing symlink for combined hierarchy: %m");
-                        if (r < 0)
-                                return log_error_errno(r, "Failed to create symlink for combined hierarchy: %m");
-                }
-        }
-
-skip_controllers:
-        if (unified_requested >= CGROUP_UNIFIED_SYSTEMD) {
-                r = mount_legacy_cgroup_hierarchy(dest, SYSTEMD_CGROUP_CONTROLLER_HYBRID, "unified", false);
-                if (r < 0)
-                        return r;
-        }
-
-        r = mount_legacy_cgroup_hierarchy(dest, SYSTEMD_CGROUP_CONTROLLER_LEGACY, "systemd", false);
-        if (r < 0)
-                return r;
-
-        return mount_verbose(LOG_ERR, NULL, cgroup_root, NULL,
-                             MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME|MS_RDONLY, "mode=755");
-}
-
-static int mount_unified_cgroups(const char *dest) {
-        const char *p;
-        int r;
-
-        assert(dest);
-
-        p = prefix_roota(dest, "/sys/fs/cgroup");
-
-        (void) mkdir_p(p, 0755);
-
-        r = path_is_mount_point(p, dest, AT_SYMLINK_FOLLOW);
-        if (r < 0)
-                return log_error_errno(r, "Failed to determine if %s is mounted already: %m", p);
-        if (r > 0) {
-                p = prefix_roota(dest, "/sys/fs/cgroup/cgroup.procs");
-                if (access(p, F_OK) >= 0)
-                        return 0;
-                if (errno != ENOENT)
-                        return log_error_errno(errno, "Failed to determine if mount point %s contains the unified cgroup hierarchy: %m", p);
-
-                log_error("%s is already mounted but not a unified cgroup hierarchy. Refusing.", p);
-                return -EINVAL;
-        }
-
-        return mount_verbose(LOG_ERR, "cgroup", p, "cgroup2", MS_NOSUID|MS_NOEXEC|MS_NODEV, NULL);
-}
-
-int mount_cgroups(
-                const char *dest,
-                CGroupUnified unified_requested,
-                bool userns,
-                uid_t uid_shift,
-                uid_t uid_range,
-                const char *selinux_apifs_context,
-                bool use_cgns) {
-
-        if (unified_requested >= CGROUP_UNIFIED_ALL)
-                return mount_unified_cgroups(dest);
-        if (use_cgns)
-                return mount_legacy_cgns_supported(dest, unified_requested, userns, uid_shift, uid_range, selinux_apifs_context);
-
-        return mount_legacy_cgns_unsupported(dest, unified_requested, userns, uid_shift, uid_range, selinux_apifs_context);
-}
-
-static int mount_systemd_cgroup_writable_one(const char *root, const char *own) {
-        int r;
-
-        assert(root);
-        assert(own);
-
-        /* Make our own cgroup a (writable) bind mount */
-        r = mount_verbose(LOG_ERR, own, own, NULL, MS_BIND, NULL);
-        if (r < 0)
-                return r;
-
-        /* And then remount the systemd cgroup root read-only */
-        return mount_verbose(LOG_ERR, NULL, root, NULL,
-                             MS_BIND|MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_RDONLY, NULL);
-}
-
-int mount_systemd_cgroup_writable(
-                const char *dest,
-                CGroupUnified unified_requested) {
-
-        _cleanup_free_ char *own_cgroup_path = NULL;
-        const char *root, *own;
-        int r;
-
-        assert(dest);
-
-        r = cg_pid_get_path(NULL, 0, &own_cgroup_path);
-        if (r < 0)
-                return log_error_errno(r, "Failed to determine our own cgroup path: %m");
-
-        /* If we are living in the top-level, then there's nothing to do... */
-        if (path_equal(own_cgroup_path, "/"))
-                return 0;
-
-        if (unified_requested >= CGROUP_UNIFIED_ALL) {
-
-                root = prefix_roota(dest, "/sys/fs/cgroup");
-                own = strjoina(root, own_cgroup_path);
-
-        } else {
-
-                if (unified_requested >= CGROUP_UNIFIED_SYSTEMD) {
-                        root = prefix_roota(dest, "/sys/fs/cgroup/unified");
-                        own = strjoina(root, own_cgroup_path);
-
-                        r = mount_systemd_cgroup_writable_one(root, own);
-                        if (r < 0)
-                                return r;
-                }
-
-                root = prefix_roota(dest, "/sys/fs/cgroup/systemd");
-                own = strjoina(root, own_cgroup_path);
-        }
-
-        return mount_systemd_cgroup_writable_one(root, own);
-}
-
 int setup_volatile_state(
                 const char *directory,
                 VolatileMode mode,
@@ -1301,7 +876,7 @@ int setup_volatile_state(
                 return log_error_errno(errno, "Failed to create %s: %m", directory);
 
         options = "mode=755";
-        r = tmpfs_patch_options(options, userns, uid_shift, uid_range, false, selinux_apifs_context, &buf);
+        r = tmpfs_patch_options(options, uid_shift == 0 ? UID_INVALID : uid_shift, selinux_apifs_context, &buf);
         if (r < 0)
                 return log_oom();
         if (r > 0)
@@ -1334,7 +909,7 @@ int setup_volatile(
                 return log_error_errno(errno, "Failed to create temporary directory: %m");
 
         options = "mode=755";
-        r = tmpfs_patch_options(options, userns, uid_shift, uid_range, false, selinux_apifs_context, &buf);
+        r = tmpfs_patch_options(options, uid_shift == 0 ? UID_INVALID : uid_shift, selinux_apifs_context, &buf);
         if (r < 0)
                 return log_oom();
         if (r > 0)

src/nspawn/nspawn-mount.h

@@ -43,12 +43,9 @@ int bind_mount_parse(CustomMount **l, size_t *n, const char *s, bool read_only);
 int tmpfs_mount_parse(CustomMount **l, size_t *n, const char *s);
 int overlay_mount_parse(CustomMount **l, size_t *n, const char *s, bool read_only);
 
-int mount_all(const char *dest, MountSettingsMask mount_settings, uid_t uid_shift, uid_t uid_range, const char *selinux_apifs_context);
+int mount_all(const char *dest, MountSettingsMask mount_settings, uid_t uid_shift, const char *selinux_apifs_context);
 int mount_sysfs(const char *dest, MountSettingsMask mount_settings);
 
-int mount_cgroups(const char *dest, CGroupUnified unified_requested, bool userns, uid_t uid_shift, uid_t uid_range, const char *selinux_apifs_context, bool use_cgns);
-int mount_systemd_cgroup_writable(const char *dest, CGroupUnified unified_requested);
-
 int mount_custom(const char *dest, CustomMount *mounts, size_t n, bool userns, uid_t uid_shift, uid_t uid_range, const char *selinux_apifs_context);
 
 int setup_volatile(const char *directory, VolatileMode mode, bool userns, uid_t uid_shift, uid_t uid_range, const char *selinux_apifs_context);
@@ -56,3 +53,5 @@ int setup_volatile_state(const char *directory, VolatileMode mode, bool userns,
 
 int pivot_root_parse(char **pivot_root_new, char **pivot_root_old, const char *s);
 int setup_pivot_root(const char *directory, const char *pivot_root_new, const char *pivot_root_old);
+
+int tmpfs_patch_options(const char *options,uid_t uid_shift, const char *selinux_apifs_context, char **ret);

src/nspawn/nspawn.c

@@ -2558,7 +2558,6 @@ static int inner_child(
         r = mount_all(NULL,
                       arg_mount_settings | MOUNT_IN_USERNS,
                       arg_uid_shift,
-                      arg_uid_range,
                       arg_selinux_apifs_context);
         if (r < 0)
                 return r;
@@ -2990,7 +2989,6 @@ static int outer_child(
         r = mount_all(directory,
                       arg_mount_settings,
                       arg_uid_shift,
-                      arg_uid_range,
                       arg_selinux_apifs_context);
         if (r < 0)
                 return r;