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-rw-r--r--src/shared/mount-setup.c574
1 files changed, 574 insertions, 0 deletions
diff --git a/src/shared/mount-setup.c b/src/shared/mount-setup.c
new file mode 100644
index 0000000..6882b62
--- /dev/null
+++ b/src/shared/mount-setup.c
@@ -0,0 +1,574 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <stdlib.h>
+#include <sys/mount.h>
+#include <sys/statvfs.h>
+#include <unistd.h>
+
+#include "alloc-util.h"
+#include "bus-util.h"
+#include "cgroup-setup.h"
+#include "cgroup-util.h"
+#include "conf-files.h"
+#include "dev-setup.h"
+#include "dirent-util.h"
+#include "efi-loader.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "fs-util.h"
+#include "label.h"
+#include "log.h"
+#include "macro.h"
+#include "mkdir-label.h"
+#include "mount-setup.h"
+#include "mount-util.h"
+#include "mountpoint-util.h"
+#include "nulstr-util.h"
+#include "path-util.h"
+#include "recurse-dir.h"
+#include "set.h"
+#include "smack-util.h"
+#include "strv.h"
+#include "user-util.h"
+#include "virt.h"
+
+typedef enum MountMode {
+ MNT_NONE = 0,
+ MNT_FATAL = 1 << 0,
+ MNT_IN_CONTAINER = 1 << 1,
+ MNT_CHECK_WRITABLE = 1 << 2,
+ MNT_FOLLOW_SYMLINK = 1 << 3,
+} MountMode;
+
+typedef struct MountPoint {
+ const char *what;
+ const char *where;
+ const char *type;
+ const char *options;
+ unsigned long flags;
+ bool (*condition_fn)(void);
+ MountMode mode;
+} MountPoint;
+
+/* The first three entries we might need before SELinux is up. The
+ * fourth (securityfs) is needed by IMA to load a custom policy. The
+ * other ones we can delay until SELinux and IMA are loaded. When
+ * SMACK is enabled we need smackfs, too, so it's a fifth one. */
+#if ENABLE_SMACK
+#define N_EARLY_MOUNT 5
+#else
+#define N_EARLY_MOUNT 4
+#endif
+
+static const MountPoint mount_table[] = {
+ { "proc", "/proc", "proc", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
+ NULL, MNT_FATAL|MNT_IN_CONTAINER|MNT_FOLLOW_SYMLINK },
+ { "sysfs", "/sys", "sysfs", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
+ NULL, MNT_FATAL|MNT_IN_CONTAINER },
+ { "devtmpfs", "/dev", "devtmpfs", "mode=755" TMPFS_LIMITS_DEV, MS_NOSUID|MS_STRICTATIME,
+ NULL, MNT_FATAL|MNT_IN_CONTAINER },
+ { "securityfs", "/sys/kernel/security", "securityfs", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
+ NULL, MNT_NONE },
+#if ENABLE_SMACK
+ { "smackfs", "/sys/fs/smackfs", "smackfs", "smackfsdef=*", MS_NOSUID|MS_NOEXEC|MS_NODEV,
+ mac_smack_use, MNT_FATAL },
+ { "tmpfs", "/dev/shm", "tmpfs", "mode=1777,smackfsroot=*", MS_NOSUID|MS_NODEV|MS_STRICTATIME,
+ mac_smack_use, MNT_FATAL },
+#endif
+ { "tmpfs", "/dev/shm", "tmpfs", "mode=1777", MS_NOSUID|MS_NODEV|MS_STRICTATIME,
+ NULL, MNT_FATAL|MNT_IN_CONTAINER },
+ { "devpts", "/dev/pts", "devpts", "mode=620,gid=" STRINGIFY(TTY_GID), MS_NOSUID|MS_NOEXEC,
+ NULL, MNT_IN_CONTAINER },
+#if ENABLE_SMACK
+ { "tmpfs", "/run", "tmpfs", "mode=755,smackfsroot=*" TMPFS_LIMITS_RUN, MS_NOSUID|MS_NODEV|MS_STRICTATIME,
+ mac_smack_use, MNT_FATAL },
+#endif
+ { "tmpfs", "/run", "tmpfs", "mode=755" TMPFS_LIMITS_RUN, MS_NOSUID|MS_NODEV|MS_STRICTATIME,
+ NULL, MNT_FATAL|MNT_IN_CONTAINER },
+ { "cgroup2", "/sys/fs/cgroup", "cgroup2", "nsdelegate,memory_recursiveprot", MS_NOSUID|MS_NOEXEC|MS_NODEV,
+ cg_is_unified_wanted, MNT_IN_CONTAINER|MNT_CHECK_WRITABLE },
+ { "cgroup2", "/sys/fs/cgroup", "cgroup2", "nsdelegate", MS_NOSUID|MS_NOEXEC|MS_NODEV,
+ cg_is_unified_wanted, MNT_IN_CONTAINER|MNT_CHECK_WRITABLE },
+ { "cgroup2", "/sys/fs/cgroup", "cgroup2", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
+ cg_is_unified_wanted, MNT_IN_CONTAINER|MNT_CHECK_WRITABLE },
+ { "tmpfs", "/sys/fs/cgroup", "tmpfs", "mode=755" TMPFS_LIMITS_SYS_FS_CGROUP, MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME,
+ cg_is_legacy_wanted, MNT_FATAL|MNT_IN_CONTAINER },
+ { "cgroup2", "/sys/fs/cgroup/unified", "cgroup2", "nsdelegate", MS_NOSUID|MS_NOEXEC|MS_NODEV,
+ cg_is_hybrid_wanted, MNT_IN_CONTAINER|MNT_CHECK_WRITABLE },
+ { "cgroup2", "/sys/fs/cgroup/unified", "cgroup2", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
+ cg_is_hybrid_wanted, MNT_IN_CONTAINER|MNT_CHECK_WRITABLE },
+ { "cgroup", "/sys/fs/cgroup/systemd", "cgroup", "none,name=systemd,xattr", MS_NOSUID|MS_NOEXEC|MS_NODEV,
+ cg_is_legacy_wanted, MNT_IN_CONTAINER },
+ { "cgroup", "/sys/fs/cgroup/systemd", "cgroup", "none,name=systemd", MS_NOSUID|MS_NOEXEC|MS_NODEV,
+ cg_is_legacy_wanted, MNT_FATAL|MNT_IN_CONTAINER },
+#if ENABLE_PSTORE
+ { "pstore", "/sys/fs/pstore", "pstore", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
+ NULL, MNT_NONE },
+#endif
+#if ENABLE_EFI
+ { "efivarfs", "/sys/firmware/efi/efivars", "efivarfs", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
+ is_efi_boot, MNT_NONE },
+#endif
+ { "bpf", "/sys/fs/bpf", "bpf", "mode=700", MS_NOSUID|MS_NOEXEC|MS_NODEV,
+ NULL, MNT_NONE, },
+};
+
+bool mount_point_is_api(const char *path) {
+ unsigned i;
+
+ /* Checks if this mount point is considered "API", and hence
+ * should be ignored */
+
+ for (i = 0; i < ELEMENTSOF(mount_table); i ++)
+ if (path_equal(path, mount_table[i].where))
+ return true;
+
+ return path_startswith(path, "/sys/fs/cgroup/");
+}
+
+bool mount_point_ignore(const char *path) {
+ /* These are API file systems that might be mounted by other software, we just list them here so that
+ * we know that we should ignore them. */
+ FOREACH_STRING(i,
+ /* SELinux file systems */
+ "/sys/fs/selinux",
+ /* Container bind mounts */
+ "/dev/console",
+ "/proc/kmsg",
+ "/proc/sys",
+ "/proc/sys/kernel/random/boot_id")
+ if (path_equal(path, i))
+ return true;
+
+ if (path_startswith(path, "/run/host")) /* All mounts passed in from the container manager are
+ * something we better ignore. */
+ return true;
+
+ return false;
+}
+
+static int mount_one(const MountPoint *p, bool relabel) {
+ int r, priority;
+
+ assert(p);
+
+ priority = (p->mode & MNT_FATAL) ? LOG_ERR : LOG_DEBUG;
+
+ if (p->condition_fn && !p->condition_fn())
+ return 0;
+
+ /* Relabel first, just in case */
+ if (relabel)
+ (void) label_fix(p->where, LABEL_IGNORE_ENOENT|LABEL_IGNORE_EROFS);
+
+ r = path_is_mount_point(p->where, NULL, AT_SYMLINK_FOLLOW);
+ if (r < 0 && r != -ENOENT) {
+ log_full_errno(priority, r, "Failed to determine whether %s is a mount point: %m", p->where);
+ return (p->mode & MNT_FATAL) ? r : 0;
+ }
+ if (r > 0)
+ return 0;
+
+ /* Skip securityfs in a container */
+ if (!(p->mode & MNT_IN_CONTAINER) && detect_container() > 0)
+ return 0;
+
+ /* The access mode here doesn't really matter too much, since
+ * the mounted file system will take precedence anyway. */
+ if (relabel)
+ (void) mkdir_p_label(p->where, 0755);
+ else
+ (void) mkdir_p(p->where, 0755);
+
+ log_debug("Mounting %s to %s of type %s with options %s.",
+ p->what,
+ p->where,
+ p->type,
+ strna(p->options));
+
+ if (FLAGS_SET(p->mode, MNT_FOLLOW_SYMLINK))
+ r = RET_NERRNO(mount(p->what, p->where, p->type, p->flags, p->options));
+ else
+ r = mount_nofollow(p->what, p->where, p->type, p->flags, p->options);
+ if (r < 0) {
+ log_full_errno(priority, r, "Failed to mount %s at %s: %m", p->type, p->where);
+ return (p->mode & MNT_FATAL) ? r : 0;
+ }
+
+ /* Relabel again, since we now mounted something fresh here */
+ if (relabel)
+ (void) label_fix(p->where, 0);
+
+ if (p->mode & MNT_CHECK_WRITABLE) {
+ if (access(p->where, W_OK) < 0) {
+ r = -errno;
+
+ (void) umount2(p->where, UMOUNT_NOFOLLOW);
+ (void) rmdir(p->where);
+
+ log_full_errno(priority, r, "Mount point %s not writable after mounting: %m", p->where);
+ return (p->mode & MNT_FATAL) ? r : 0;
+ }
+ }
+
+ return 1;
+}
+
+static int mount_points_setup(unsigned n, bool loaded_policy) {
+ unsigned i;
+ int r = 0;
+
+ for (i = 0; i < n; i ++) {
+ int j;
+
+ j = mount_one(mount_table + i, loaded_policy);
+ if (j != 0 && r >= 0)
+ r = j;
+ }
+
+ return r;
+}
+
+int mount_setup_early(void) {
+ assert_cc(N_EARLY_MOUNT <= ELEMENTSOF(mount_table));
+
+ /* Do a minimal mount of /proc and friends to enable the most
+ * basic stuff, such as SELinux */
+ return mount_points_setup(N_EARLY_MOUNT, false);
+}
+
+static const char *join_with(const char *controller) {
+
+ static const char* const pairs[] = {
+ "cpu", "cpuacct",
+ "net_cls", "net_prio",
+ NULL
+ };
+
+ assert(controller);
+
+ /* This will lookup which controller to mount another controller with. Input is a controller name, and output
+ * is the other controller name. The function works both ways: you can input one and get the other, and input
+ * the other to get the one. */
+
+ STRV_FOREACH_PAIR(x, y, pairs) {
+ if (streq(controller, *x))
+ return *y;
+ if (streq(controller, *y))
+ return *x;
+ }
+
+ return NULL;
+}
+
+static int symlink_controller(const char *target, const char *alias) {
+ const char *a;
+ int r;
+
+ assert(target);
+ assert(alias);
+
+ a = strjoina("/sys/fs/cgroup/", alias);
+
+ r = symlink_idempotent(target, a, false);
+ if (r < 0)
+ return log_error_errno(r, "Failed to create symlink %s: %m", a);
+
+#if HAVE_SMACK_RUN_LABEL
+ const char *p;
+
+ p = strjoina("/sys/fs/cgroup/", target);
+
+ r = mac_smack_copy(a, p);
+ if (r < 0 && r != -EOPNOTSUPP)
+ return log_error_errno(r, "Failed to copy smack label from %s to %s: %m", p, a);
+#endif
+
+ return 0;
+}
+
+int mount_cgroup_controllers(void) {
+ _cleanup_set_free_ Set *controllers = NULL;
+ int r;
+
+ if (!cg_is_legacy_wanted())
+ return 0;
+
+ /* Mount all available cgroup controllers that are built into the kernel. */
+ r = cg_kernel_controllers(&controllers);
+ if (r < 0)
+ return log_error_errno(r, "Failed to enumerate cgroup controllers: %m");
+
+ for (;;) {
+ _cleanup_free_ char *options = NULL, *controller = NULL, *where = NULL;
+ const char *other_controller;
+ MountPoint p = {
+ .what = "cgroup",
+ .type = "cgroup",
+ .flags = MS_NOSUID|MS_NOEXEC|MS_NODEV,
+ .mode = MNT_IN_CONTAINER,
+ };
+
+ controller = set_steal_first(controllers);
+ if (!controller)
+ break;
+
+ /* Check if we shall mount this together with another controller */
+ other_controller = join_with(controller);
+ if (other_controller) {
+ _cleanup_free_ char *c = NULL;
+
+ /* Check if the other controller is actually available in the kernel too */
+ c = set_remove(controllers, other_controller);
+ if (c) {
+
+ /* Join the two controllers into one string, and maintain a stable ordering */
+ if (strcmp(controller, other_controller) < 0)
+ options = strjoin(controller, ",", other_controller);
+ else
+ options = strjoin(other_controller, ",", controller);
+ if (!options)
+ return log_oom();
+ }
+ }
+
+ /* The simple case, where there's only one controller to mount together */
+ if (!options)
+ options = TAKE_PTR(controller);
+
+ where = path_join("/sys/fs/cgroup", options);
+ if (!where)
+ return log_oom();
+
+ p.where = where;
+ p.options = options;
+
+ r = mount_one(&p, true);
+ if (r < 0)
+ return r;
+
+ /* Create symlinks from the individual controller names, in case we have a joined mount */
+ if (controller)
+ (void) symlink_controller(options, controller);
+ if (other_controller)
+ (void) symlink_controller(options, other_controller);
+ }
+
+ /* Now that we mounted everything, let's make the tmpfs the cgroup file systems are mounted into read-only. */
+ (void) mount_nofollow("tmpfs", "/sys/fs/cgroup", "tmpfs", MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME|MS_RDONLY, "mode=755" TMPFS_LIMITS_SYS_FS_CGROUP);
+
+ return 0;
+}
+
+#if HAVE_SELINUX || ENABLE_SMACK
+static int relabel_cb(
+ RecurseDirEvent event,
+ const char *path,
+ int dir_fd,
+ int inode_fd,
+ const struct dirent *de,
+ const struct statx *sx,
+ void *userdata) {
+
+ switch (event) {
+
+ case RECURSE_DIR_LEAVE:
+ case RECURSE_DIR_SKIP_MOUNT:
+ /* If we already saw this dirent when entering it or this is a dirent that on a different
+ * mount, don't relabel it. */
+ return RECURSE_DIR_CONTINUE;
+
+ case RECURSE_DIR_ENTER:
+ /* /run/initramfs is static data and big, no need to dynamically relabel its contents at boot... */
+ if (path_equal(path, "/run/initramfs"))
+ return RECURSE_DIR_SKIP_ENTRY;
+
+ _fallthrough_;
+
+ default:
+ /* Otherwise, label it, even if we had trouble stat()ing it and similar. SELinux can figure this out */
+ (void) label_fix(path, 0);
+ return RECURSE_DIR_CONTINUE;
+ }
+}
+
+static int relabel_tree(const char *path) {
+ int r;
+
+ r = recurse_dir_at(AT_FDCWD, path, 0, UINT_MAX, RECURSE_DIR_ENSURE_TYPE|RECURSE_DIR_SAME_MOUNT, relabel_cb, NULL);
+ if (r < 0)
+ log_debug_errno(r, "Failed to recursively relabel '%s': %m", path);
+
+ return r;
+}
+
+static int relabel_cgroup_filesystems(void) {
+ int r;
+ struct statfs st;
+
+ r = cg_all_unified();
+ if (r == 0) {
+ /* Temporarily remount the root cgroup filesystem to give it a proper label. Do this
+ only when the filesystem has been already populated by a previous instance of systemd
+ running from initrd. Otherwise don't remount anything and leave the filesystem read-write
+ for the cgroup filesystems to be mounted inside. */
+ if (statfs("/sys/fs/cgroup", &st) < 0)
+ return log_error_errno(errno, "Failed to determine mount flags for /sys/fs/cgroup: %m");
+
+ if (st.f_flags & ST_RDONLY)
+ (void) mount_nofollow(NULL, "/sys/fs/cgroup", NULL, MS_REMOUNT, NULL);
+
+ (void) label_fix("/sys/fs/cgroup", 0);
+ (void) relabel_tree("/sys/fs/cgroup");
+
+ if (st.f_flags & ST_RDONLY)
+ (void) mount_nofollow(NULL, "/sys/fs/cgroup", NULL, MS_REMOUNT|MS_RDONLY, NULL);
+
+ } else if (r < 0)
+ return log_error_errno(r, "Failed to determine whether we are in all unified mode: %m");
+
+ return 0;
+}
+
+static int relabel_extra(void) {
+ _cleanup_strv_free_ char **files = NULL;
+ int r, c = 0;
+
+ /* Support for relabelling additional files or directories after loading the policy. For this, code in the
+ * initrd simply has to drop in *.relabel files into /run/systemd/relabel-extra.d/. We'll read all such files
+ * expecting one absolute path by line and will relabel each (and everyone below that in case the path refers
+ * to a directory). These drop-in files are supposed to be absolutely minimal, and do not understand comments
+ * and such. After the operation succeeded the files are removed, and the drop-in directory as well, if
+ * possible.
+ */
+
+ r = conf_files_list(&files, ".relabel", NULL,
+ CONF_FILES_FILTER_MASKED | CONF_FILES_REGULAR,
+ "/run/systemd/relabel-extra.d/");
+ if (r < 0)
+ return log_error_errno(r, "Failed to enumerate /run/systemd/relabel-extra.d/, ignoring: %m");
+
+ STRV_FOREACH(file, files) {
+ _cleanup_fclose_ FILE *f = NULL;
+
+ f = fopen(*file, "re");
+ if (!f) {
+ log_warning_errno(errno, "Failed to open %s, ignoring: %m", *file);
+ continue;
+ }
+
+ for (;;) {
+ _cleanup_free_ char *line = NULL;
+
+ r = read_line(f, LONG_LINE_MAX, &line);
+ if (r < 0) {
+ log_warning_errno(r, "Failed to read %s, ignoring: %m", *file);
+ break;
+ }
+ if (r == 0) /* EOF */
+ break;
+
+ path_simplify(line);
+
+ if (!path_is_normalized(line)) {
+ log_warning("Path to relabel is not normalized, ignoring: %s", line);
+ continue;
+ }
+
+ if (!path_is_absolute(line)) {
+ log_warning("Path to relabel is not absolute, ignoring: %s", line);
+ continue;
+ }
+
+ log_debug("Relabelling additional file/directory '%s'.", line);
+ (void) label_fix(line, 0);
+ (void) relabel_tree(line);
+ c++;
+ }
+
+ if (unlink(*file) < 0)
+ log_warning_errno(errno, "Failed to remove %s, ignoring: %m", *file);
+ }
+
+ /* Remove when we complete things. */
+ if (rmdir("/run/systemd/relabel-extra.d") < 0 &&
+ errno != ENOENT)
+ log_warning_errno(errno, "Failed to remove /run/systemd/relabel-extra.d/ directory: %m");
+
+ return c;
+}
+#endif
+
+int mount_setup(bool loaded_policy, bool leave_propagation) {
+ int r;
+
+ r = mount_points_setup(ELEMENTSOF(mount_table), loaded_policy);
+ if (r < 0)
+ return r;
+
+#if HAVE_SELINUX || ENABLE_SMACK
+ /* Nodes in devtmpfs and /run need to be manually updated for
+ * the appropriate labels, after mounting. The other virtual
+ * API file systems like /sys and /proc do not need that, they
+ * use the same label for all their files. */
+ if (loaded_policy) {
+ usec_t before_relabel, after_relabel;
+ int n_extra;
+
+ before_relabel = now(CLOCK_MONOTONIC);
+
+ FOREACH_STRING(i, "/dev", "/dev/shm", "/run")
+ (void) relabel_tree(i);
+
+ (void) relabel_cgroup_filesystems();
+
+ n_extra = relabel_extra();
+
+ after_relabel = now(CLOCK_MONOTONIC);
+
+ log_info("Relabelled /dev, /dev/shm, /run, /sys/fs/cgroup%s in %s.",
+ n_extra > 0 ? ", additional files" : "",
+ FORMAT_TIMESPAN(after_relabel - before_relabel, 0));
+ }
+#endif
+
+ /* Create a few default symlinks, which are normally created
+ * by udevd, but some scripts might need them before we start
+ * udevd. */
+ dev_setup(NULL, UID_INVALID, GID_INVALID);
+
+ /* Mark the root directory as shared in regards to mount propagation. The kernel defaults to "private", but we
+ * think it makes more sense to have a default of "shared" so that nspawn and the container tools work out of
+ * the box. If specific setups need other settings they can reset the propagation mode to private if
+ * needed. Note that we set this only when we are invoked directly by the kernel. If we are invoked by a
+ * container manager we assume the container manager knows what it is doing (for example, because it set up
+ * some directories with different propagation modes). */
+ if (detect_container() <= 0 && !leave_propagation)
+ if (mount(NULL, "/", NULL, MS_REC|MS_SHARED, NULL) < 0)
+ log_warning_errno(errno, "Failed to set up the root directory for shared mount propagation: %m");
+
+ /* Create a few directories we always want around, Note that sd_booted() checks for /run/systemd/system, so
+ * this mkdir really needs to stay for good, otherwise software that copied sd-daemon.c into their sources will
+ * misdetect systemd. */
+ (void) mkdir_label("/run/systemd", 0755);
+ (void) mkdir_label("/run/systemd/system", 0755);
+
+ /* Make sure we have a mount point to hide in sandboxes */
+ (void) mkdir_label("/run/credentials", 0755);
+
+ /* Also create /run/systemd/inaccessible nodes, so that we always have something to mount
+ * inaccessible nodes from. If we run in a container the host might have created these for us already
+ * in /run/host/inaccessible/. Use those if we can, since that way we likely get access to block/char
+ * device nodes that are inaccessible, and if userns is used to nodes that are on mounts owned by a
+ * userns outside the container and thus nicely read-only and not remountable. */
+ if (access("/run/host/inaccessible/", F_OK) < 0) {
+ if (errno != ENOENT)
+ log_debug_errno(errno, "Failed to check if /run/host/inaccessible exists, ignoring: %m");
+
+ (void) make_inaccessible_nodes("/run/systemd", UID_INVALID, GID_INVALID);
+ } else
+ (void) symlink("../host/inaccessible", "/run/systemd/inaccessible");
+
+ return 0;
+}
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