From 55cd6a5237b1dc1fbef0d1a23d36de7dcba01aa0 Mon Sep 17 00:00:00 2001 From: Luke Shumaker Date: Tue, 13 Jun 2017 22:40:53 -0400 Subject: nspawn: Move cgroup mount stuff from nspawn-mount.c to nspawn-cgroup.c --- src/nspawn/nspawn-cgroup.c | 369 ++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 368 insertions(+), 1 deletion(-) (limited to 'src/nspawn/nspawn-cgroup.c') diff --git a/src/nspawn/nspawn-cgroup.c b/src/nspawn/nspawn-cgroup.c index 44be995252..7f3f4340a1 100644 --- a/src/nspawn/nspawn-cgroup.c +++ b/src/nspawn/nspawn-cgroup.c @@ -22,14 +22,19 @@ #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 "path-util.h" #include "rm-rf.h" #include "string-util.h" #include "strv.h" +#include "user-util.h" #include "util.h" +#include "nspawn-cgroup.h" +#include "nspawn-mount.h" + static int chown_cgroup_path(const char *path, uid_t uid_shift) { _cleanup_close_ int fd = -1; const char *fn; @@ -182,3 +187,365 @@ int create_subcgroup(pid_t pid, 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_controllers(Set *subsystems) { + _cleanup_fclose_ FILE *f = NULL; + char line[LINE_MAX]; + + assert(subsystems); + + f = fopen("/proc/self/cgroup", "re"); + if (!f) + return errno == ENOENT ? -ESRCH : -errno; + + FOREACH_LINE(line, f, return -errno) { + int r; + char *e, *l, *p; + + l = strchr(line, ':'); + if (!l) + continue; + + l++; + e = strchr(l, ':'); + if (!e) + continue; + + *e = 0; + + if (STR_IN_SET(l, "", "name=systemd")) + continue; + + p = strdup(l); + if (!p) + return -ENOMEM; + + r = set_consume(subsystems, p); + if (r < 0) + return r; + } + + return 0; +} + +static int mount_legacy_cgroup_hierarchy(const char *dest, const char *controller, const char *hierarchy, + CGroupUnified unified_requested, bool read_only) { + const char *to, *fstype, *opts; + int r; + + to = strjoina(strempty(dest), "/sys/fs/cgroup/", hierarchy); + + r = path_is_mount_point(to, 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)) { + if (unified_requested >= CGROUP_UNIFIED_SYSTEMD) { + fstype = "cgroup2"; + opts = NULL; + } else { + 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( + 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, 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; + } + + if (cg_all_unified() > 0) + goto skip_controllers; + + controllers = set_new(&string_hash_ops); + if (!controllers) + return log_oom(); + + r = get_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, unified_requested, !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; + + target = prefix_root("/sys/fs/cgroup", tok); + if (!target) + return log_oom(); + + if (streq(controller, tok)) + break; + + 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: + r = mount_legacy_cgroup_hierarchy("", SYSTEMD_CGROUP_CONTROLLER, "systemd", unified_requested, 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, 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; + } + + if (cg_all_unified() > 0) + goto skip_controllers; + + controllers = set_new(&string_hash_ops); + if (!controllers) + return log_oom(); + + 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, unified_requested, 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, unified_requested, 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: + r = mount_legacy_cgroup_hierarchy(dest, SYSTEMD_CGROUP_CONTROLLER, "systemd", unified_requested, 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, 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); + else if (use_cgns) + return mount_legacy_cgns_supported(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); +} + +int mount_systemd_cgroup_writable( + const char *dest, + CGroupUnified unified_requested) { + + _cleanup_free_ char *own_cgroup_path = NULL; + const char *systemd_root, *systemd_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) { + systemd_own = strjoina(dest, "/sys/fs/cgroup", own_cgroup_path); + systemd_root = prefix_roota(dest, "/sys/fs/cgroup"); + } else { + systemd_own = strjoina(dest, "/sys/fs/cgroup/systemd", own_cgroup_path); + systemd_root = prefix_roota(dest, "/sys/fs/cgroup/systemd"); + } + + /* Make our own cgroup a (writable) bind mount */ + r = mount_verbose(LOG_ERR, systemd_own, systemd_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, systemd_root, NULL, + MS_BIND|MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_RDONLY, NULL); +} -- cgit v1.2.3-54-g00ecf