diff options
Diffstat (limited to '')
| -rw-r--r-- | src/nspawn/nspawn-cgroup.c | 606 |
1 files changed, 606 insertions, 0 deletions
diff --git a/src/nspawn/nspawn-cgroup.c b/src/nspawn/nspawn-cgroup.c new file mode 100644 index 0000000..6c47ab6 --- /dev/null +++ b/src/nspawn/nspawn-cgroup.c @@ -0,0 +1,606 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ + +#include <sys/mount.h> + +#include "alloc-util.h" +#include "cgroup-setup.h" +#include "fd-util.h" +#include "fileio.h" +#include "format-util.h" +#include "fs-util.h" +#include "mkdir.h" +#include "mount-util.h" +#include "mountpoint-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) { + _cleanup_close_ int fd = -1; + + fd = open(path, O_RDONLY|O_CLOEXEC|O_DIRECTORY); + if (fd < 0) + return -errno; + + FOREACH_STRING(fn, + ".", + "cgroup.clone_children", + "cgroup.controllers", + "cgroup.events", + "cgroup.procs", + "cgroup.stat", + "cgroup.subtree_control", + "cgroup.threads", + "memory.oom.group", + "memory.reclaim", + "notify_on_release", + "tasks") + if (fchownat(fd, fn, uid_shift, uid_shift, 0) < 0) + log_full_errno(errno == ENOENT ? LOG_DEBUG : LOG_WARNING, errno, + "Failed to chown \"%s/%s\", ignoring: %m", path, fn); + + return 0; +} + +int chown_cgroup(pid_t pid, CGroupUnified unified_requested, uid_t uid_shift) { + _cleanup_free_ char *path = NULL, *fs = NULL; + int r; + + r = cg_pid_get_path(NULL, pid, &path); + if (r < 0) + return log_error_errno(r, "Failed to get container cgroup path: %m"); + + r = cg_get_path(SYSTEMD_CGROUP_CONTROLLER, path, NULL, &fs); + if (r < 0) + return log_error_errno(r, "Failed to get file system path for container cgroup: %m"); + + r = chown_cgroup_path(fs, uid_shift); + if (r < 0) + return log_error_errno(r, "Failed to chown() cgroup %s: %m", fs); + + if (unified_requested == CGROUP_UNIFIED_SYSTEMD || (unified_requested == CGROUP_UNIFIED_NONE && cg_unified_controller(SYSTEMD_CGROUP_CONTROLLER) > 0)) { + _cleanup_free_ char *lfs = NULL; + /* Always propagate access rights from unified to legacy controller */ + + r = cg_get_path(SYSTEMD_CGROUP_CONTROLLER_LEGACY, path, NULL, &lfs); + if (r < 0) + return log_error_errno(r, "Failed to get file system path for container cgroup: %m"); + + r = chown_cgroup_path(lfs, uid_shift); + if (r < 0) + return log_error_errno(r, "Failed to chown() cgroup %s: %m", lfs); + } + + return 0; +} + +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; + const char *fn; + int r, unified_controller; + + unified_controller = cg_unified_controller(SYSTEMD_CGROUP_CONTROLLER); + if (unified_controller < 0) + return log_error_errno(unified_controller, "Failed to determine whether the systemd hierarchy is unified: %m"); + if ((unified_controller > 0) == (unified_requested >= CGROUP_UNIFIED_SYSTEMD)) + return 0; + + /* When the host uses the legacy cgroup setup, but the + * container shall use the unified hierarchy, let's make sure + * we copy the path from the name=systemd hierarchy into the + * unified hierarchy. Similar for the reverse situation. */ + + r = cg_pid_get_path(SYSTEMD_CGROUP_CONTROLLER, pid, &cgroup); + if (r < 0) + return log_error_errno(r, "Failed to get control group of " PID_FMT ": %m", pid); + + /* In order to access the unified hierarchy we need to mount it */ + if (!mkdtemp(tree)) + return log_error_errno(errno, "Failed to generate temporary mount point for unified hierarchy: %m"); + + if (unified_controller > 0) + r = mount_nofollow_verbose(LOG_ERR, "cgroup", tree, "cgroup", + MS_NOSUID|MS_NOEXEC|MS_NODEV, "none,name=systemd,xattr"); + else + r = mount_nofollow_verbose(LOG_ERR, "cgroup", tree, "cgroup2", + MS_NOSUID|MS_NOEXEC|MS_NODEV, NULL); + if (r < 0) + goto finish; + + undo_mount = true; + + /* If nspawn dies abruptly the cgroup hierarchy created below + * its unit isn't cleaned up. So, let's remove it + * https://github.com/systemd/systemd/pull/4223#issuecomment-252519810 */ + fn = strjoina(tree, cgroup); + (void) rm_rf(fn, REMOVE_ROOT|REMOVE_ONLY_DIRECTORIES); + + fn = strjoina(tree, cgroup, "/cgroup.procs"); + + sprintf(pid_string, PID_FMT, pid); + r = write_string_file(fn, pid_string, WRITE_STRING_FILE_DISABLE_BUFFER|WRITE_STRING_FILE_MKDIR_0755); + if (r < 0) { + log_error_errno(r, "Failed to move process: %m"); + goto finish; + } + + fn = strjoina(tree, cgroup); + r = chown_cgroup_path(fn, uid_shift); + if (r < 0) + log_error_errno(r, "Failed to chown() cgroup %s: %m", fn); +finish: + if (undo_mount) + (void) umount_verbose(LOG_ERR, tree, UMOUNT_NOFOLLOW); + + (void) rmdir(tree); + return r; +} + +int create_subcgroup(pid_t pid, bool keep_unit, CGroupUnified unified_requested) { + _cleanup_free_ char *cgroup = NULL; + CGroupMask supported; + const char *payload; + int r; + + assert(pid > 1); + + /* In the unified hierarchy inner nodes may only contain subgroups, but not processes. Hence, if we running in + * the unified hierarchy and the container does the same, and we did not create a scope unit for the container + * move us and the container into two separate subcgroups. + * + * Moreover, container payloads such as systemd try to manage the cgroup they run in full (i.e. including + * its attributes), while the host systemd will only delegate cgroups for children of the cgroup created for a + * delegation unit, instead of the cgroup itself. This means, if we'd pass on the cgroup allocated from the + * host systemd directly to the payload, the host and payload systemd might fight for the cgroup + * attributes. Hence, let's insert an intermediary cgroup to cover that case too. + * + * Note that we only bother with the main hierarchy here, not with any secondary ones. On the unified setup + * that's fine because there's only one hierarchy anyway and controllers are enabled directly on it. On the + * legacy setup, this is fine too, since delegation of controllers is generally not safe there, hence we won't + * do it. */ + + r = cg_mask_supported(&supported); + if (r < 0) + return log_error_errno(r, "Failed to determine supported controllers: %m"); + + if (keep_unit) + r = cg_pid_get_path(SYSTEMD_CGROUP_CONTROLLER, 0, &cgroup); + else + r = cg_pid_get_path(SYSTEMD_CGROUP_CONTROLLER, pid, &cgroup); + if (r < 0) + return log_error_errno(r, "Failed to get our control group: %m"); + + payload = strjoina(cgroup, "/payload"); + r = cg_create_and_attach(SYSTEMD_CGROUP_CONTROLLER, payload, pid); + if (r < 0) + return log_error_errno(r, "Failed to create %s subcgroup: %m", payload); + + if (keep_unit) { + const char *supervisor; + + supervisor = strjoina(cgroup, "/supervisor"); + r = cg_create_and_attach(SYSTEMD_CGROUP_CONTROLLER, supervisor, 0); + if (r < 0) + return log_error_errno(r, "Failed to create %s subcgroup: %m", supervisor); + } + + /* Try to enable as many controllers as possible for the new payload. */ + (void) cg_enable_everywhere(supported, supported, cgroup, NULL); + return 0; +} + +/* Retrieve existing subsystems. This function is called in a new cgroup + * namespace. + */ +static int get_process_controllers(Set **ret) { + _cleanup_set_free_ Set *controllers = NULL; + _cleanup_fclose_ FILE *f = NULL; + int r; + + assert(ret); + + 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; + + (void) 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_nofollow_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_nofollow_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_ 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" TMPFS_LIMITS_SYS_FS_CGROUP, 0, selinux_apifs_context, &options); + if (r < 0) + return log_oom(); + + r = mount_nofollow_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 = path_join("/sys/fs/cgroup/", tok); + if (!target) + return log_oom(); + + r = symlink_idempotent(controller, target, false); + 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_nofollow_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_ 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" TMPFS_LIMITS_SYS_FS_CGROUP, uid_shift == 0 ? UID_INVALID : uid_shift, selinux_apifs_context, &options); + if (r < 0) + return log_oom(); + + r = mount_nofollow_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 = path_join("/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 = path_join(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, false); + 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_nofollow_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); + + return log_error_errno(SYNTHETIC_ERRNO(EINVAL), + "%s is already mounted but not a unified cgroup hierarchy. Refusing.", p); + } + + return mount_nofollow_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_nofollow_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_nofollow_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); +} |