src/core/mount-setup.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /***
   3   Copyright 2010 Lennart Poettering
   4 ***/
   5
   6 #include <errno.h>
   7 #include <ftw.h>
   8 #include <stdlib.h>
   9 #include <sys/mount.h>
  10 #include <sys/statvfs.h>
  11 #include <unistd.h>
  12
  13 #include "alloc-util.h"
  14 #include "bus-util.h"
  15 #include "cgroup-util.h"
  16 #include "dev-setup.h"
  17 #include "efivars.h"
  18 #include "fileio.h"
  19 #include "fs-util.h"
  20 #include "label.h"
  21 #include "log.h"
  22 #include "macro.h"
  23 #include "missing.h"
  24 #include "mkdir.h"
  25 #include "mount-setup.h"
  26 #include "mount-util.h"
  27 #include "path-util.h"
  28 #include "set.h"
  29 #include "smack-util.h"
  30 #include "strv.h"
  31 #include "user-util.h"
  32 #include "util.h"
  33 #include "virt.h"
  34
  35 typedef enum MountMode {
  36         MNT_NONE           = 0,
  37         MNT_FATAL          = 1 << 0,
  38         MNT_IN_CONTAINER   = 1 << 1,
  39         MNT_CHECK_WRITABLE = 1 << 2,
  40 } MountMode;
  41
  42 typedef struct MountPoint {
  43         const char *what;
  44         const char *where;
  45         const char *type;
  46         const char *options;
  47         unsigned long flags;
  48         bool (*condition_fn)(void);
  49         MountMode mode;
  50 } MountPoint;
  51
  52 /* The first three entries we might need before SELinux is up. The
  53  * fourth (securityfs) is needed by IMA to load a custom policy. The
  54  * other ones we can delay until SELinux and IMA are loaded. When
  55  * SMACK is enabled we need smackfs, too, so it's a fifth one. */
  56 #if ENABLE_SMACK
  57 #define N_EARLY_MOUNT 5
  58 #else
  59 #define N_EARLY_MOUNT 4
  60 #endif
  61
  62 static const MountPoint mount_table[] = {
  63         { "sysfs",       "/sys",                      "sysfs",      NULL,                      MS_NOSUID|MS_NOEXEC|MS_NODEV,
  64           NULL,          MNT_FATAL|MNT_IN_CONTAINER },
  65         { "proc",        "/proc",                     "proc",       NULL,                      MS_NOSUID|MS_NOEXEC|MS_NODEV,
  66           NULL,          MNT_FATAL|MNT_IN_CONTAINER },
  67         { "devtmpfs",    "/dev",                      "devtmpfs",   "mode=755",                MS_NOSUID|MS_STRICTATIME,
  68           NULL,          MNT_FATAL|MNT_IN_CONTAINER },
  69         { "securityfs",  "/sys/kernel/security",      "securityfs", NULL,                      MS_NOSUID|MS_NOEXEC|MS_NODEV,
  70           NULL,          MNT_NONE                   },
  71 #if ENABLE_SMACK
  72         { "smackfs",     "/sys/fs/smackfs",           "smackfs",    "smackfsdef=*",            MS_NOSUID|MS_NOEXEC|MS_NODEV,
  73           mac_smack_use, MNT_FATAL                  },
  74         { "tmpfs",       "/dev/shm",                  "tmpfs",      "mode=1777,smackfsroot=*", MS_NOSUID|MS_NODEV|MS_STRICTATIME,
  75           mac_smack_use, MNT_FATAL                  },
  76 #endif
  77         { "tmpfs",       "/dev/shm",                  "tmpfs",      "mode=1777",               MS_NOSUID|MS_NODEV|MS_STRICTATIME,
  78           NULL,          MNT_FATAL|MNT_IN_CONTAINER },
  79         { "devpts",      "/dev/pts",                  "devpts",     "mode=620,gid=" STRINGIFY(TTY_GID), MS_NOSUID|MS_NOEXEC,
  80           NULL,          MNT_IN_CONTAINER           },
  81 #if ENABLE_SMACK
  82         { "tmpfs",       "/run",                      "tmpfs",      "mode=755,smackfsroot=*",  MS_NOSUID|MS_NODEV|MS_STRICTATIME,
  83           mac_smack_use, MNT_FATAL                  },
  84 #endif
  85         { "tmpfs",       "/run",                      "tmpfs",      "mode=755",                MS_NOSUID|MS_NODEV|MS_STRICTATIME,
  86           NULL,          MNT_FATAL|MNT_IN_CONTAINER },
  87         { "cgroup2",     "/sys/fs/cgroup",            "cgroup2",    "nsdelegate",              MS_NOSUID|MS_NOEXEC|MS_NODEV,
  88           cg_is_unified_wanted, MNT_IN_CONTAINER|MNT_CHECK_WRITABLE },
  89         { "cgroup2",     "/sys/fs/cgroup",            "cgroup2",    NULL,                      MS_NOSUID|MS_NOEXEC|MS_NODEV,
  90           cg_is_unified_wanted, MNT_IN_CONTAINER|MNT_CHECK_WRITABLE },
  91         { "tmpfs",       "/sys/fs/cgroup",            "tmpfs",      "mode=755",                MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME,
  92           cg_is_legacy_wanted, MNT_FATAL|MNT_IN_CONTAINER },
  93         { "cgroup2",     "/sys/fs/cgroup/unified",    "cgroup2",    "nsdelegate",              MS_NOSUID|MS_NOEXEC|MS_NODEV,
  94           cg_is_hybrid_wanted, MNT_IN_CONTAINER|MNT_CHECK_WRITABLE },
  95         { "cgroup2",     "/sys/fs/cgroup/unified",    "cgroup2",    NULL,                      MS_NOSUID|MS_NOEXEC|MS_NODEV,
  96           cg_is_hybrid_wanted, MNT_IN_CONTAINER|MNT_CHECK_WRITABLE },
  97         { "cgroup",      "/sys/fs/cgroup/systemd",    "cgroup",     "none,name=systemd,xattr", MS_NOSUID|MS_NOEXEC|MS_NODEV,
  98           cg_is_legacy_wanted, MNT_IN_CONTAINER     },
  99         { "cgroup",      "/sys/fs/cgroup/systemd",    "cgroup",     "none,name=systemd",       MS_NOSUID|MS_NOEXEC|MS_NODEV,
 100           cg_is_legacy_wanted, MNT_FATAL|MNT_IN_CONTAINER },
 101         { "pstore",      "/sys/fs/pstore",            "pstore",     NULL,                      MS_NOSUID|MS_NOEXEC|MS_NODEV,
 102           NULL,          MNT_NONE                   },
 103 #if ENABLE_EFI
 104         { "efivarfs",    "/sys/firmware/efi/efivars", "efivarfs",   NULL,                      MS_NOSUID|MS_NOEXEC|MS_NODEV,
 105           is_efi_boot,   MNT_NONE                   },
 106 #endif
 107         { "bpf",         "/sys/fs/bpf",               "bpf",        "mode=700",                MS_NOSUID|MS_NOEXEC|MS_NODEV,
 108           NULL,          MNT_NONE,                  },
 109 };
 110
 111 /* These are API file systems that might be mounted by other software,
 112  * we just list them here so that we know that we should ignore them */
 113
 114 static const char ignore_paths[] =
 115         /* SELinux file systems */
 116         "/sys/fs/selinux\0"
 117         /* Container bind mounts */
 118         "/proc/sys\0"
 119         "/dev/console\0"
 120         "/proc/kmsg\0";
 121
 122 bool mount_point_is_api(const char *path) {
 123         unsigned i;
 124
 125         /* Checks if this mount point is considered "API", and hence
 126          * should be ignored */
 127
 128         for (i = 0; i < ELEMENTSOF(mount_table); i ++)
 129                 if (path_equal(path, mount_table[i].where))
 130                         return true;
 131
 132         return path_startswith(path, "/sys/fs/cgroup/");
 133 }
 134
 135 bool mount_point_ignore(const char *path) {
 136         const char *i;
 137
 138         NULSTR_FOREACH(i, ignore_paths)
 139                 if (path_equal(path, i))
 140                         return true;
 141
 142         return false;
 143 }
 144
 145 static int mount_one(const MountPoint *p, bool relabel) {
 146         int r, priority;
 147
 148         assert(p);
 149
 150         priority = (p->mode & MNT_FATAL) ? LOG_ERR : LOG_DEBUG;
 151
 152         if (p->condition_fn && !p->condition_fn())
 153                 return 0;
 154
 155         /* Relabel first, just in case */
 156         if (relabel)
 157                 (void) label_fix(p->where, LABEL_IGNORE_ENOENT|LABEL_IGNORE_EROFS);
 158
 159         r = path_is_mount_point(p->where, NULL, AT_SYMLINK_FOLLOW);
 160         if (r < 0 && r != -ENOENT) {
 161                 log_full_errno(priority, r, "Failed to determine whether %s is a mount point: %m", p->where);
 162                 return (p->mode & MNT_FATAL) ? r : 0;
 163         }
 164         if (r > 0)
 165                 return 0;
 166
 167         /* Skip securityfs in a container */
 168         if (!(p->mode & MNT_IN_CONTAINER) && detect_container() > 0)
 169                 return 0;
 170
 171         /* The access mode here doesn't really matter too much, since
 172          * the mounted file system will take precedence anyway. */
 173         if (relabel)
 174                 (void) mkdir_p_label(p->where, 0755);
 175         else
 176                 (void) mkdir_p(p->where, 0755);
 177
 178         log_debug("Mounting %s to %s of type %s with options %s.",
 179                   p->what,
 180                   p->where,
 181                   p->type,
 182                   strna(p->options));
 183
 184         if (mount(p->what,
 185                   p->where,
 186                   p->type,
 187                   p->flags,
 188                   p->options) < 0) {
 189                 log_full_errno(priority, errno, "Failed to mount %s at %s: %m", p->type, p->where);
 190                 return (p->mode & MNT_FATAL) ? -errno : 0;
 191         }
 192
 193         /* Relabel again, since we now mounted something fresh here */
 194         if (relabel)
 195                 (void) label_fix(p->where, 0);
 196
 197         if (p->mode & MNT_CHECK_WRITABLE) {
 198                 if (access(p->where, W_OK) < 0) {
 199                         r = -errno;
 200
 201                         (void) umount(p->where);
 202                         (void) rmdir(p->where);
 203
 204                         log_full_errno(priority, r, "Mount point %s not writable after mounting: %m", p->where);
 205                         return (p->mode & MNT_FATAL) ? r : 0;
 206                 }
 207         }
 208
 209         return 1;
 210 }
 211
 212 static int mount_points_setup(unsigned n, bool loaded_policy) {
 213         unsigned i;
 214         int r = 0;
 215
 216         for (i = 0; i < n; i ++) {
 217                 int j;
 218
 219                 j = mount_one(mount_table + i, loaded_policy);
 220                 if (j != 0 && r >= 0)
 221                         r = j;
 222         }
 223
 224         return r;
 225 }
 226
 227 int mount_setup_early(void) {
 228         assert_cc(N_EARLY_MOUNT <= ELEMENTSOF(mount_table));
 229
 230         /* Do a minimal mount of /proc and friends to enable the most
 231          * basic stuff, such as SELinux */
 232         return mount_points_setup(N_EARLY_MOUNT, false);
 233 }
 234
 235 int mount_cgroup_controllers(char ***join_controllers) {
 236         _cleanup_set_free_free_ Set *controllers = NULL;
 237         bool has_argument = !!join_controllers;
 238         int r;
 239
 240         if (!cg_is_legacy_wanted())
 241                 return 0;
 242
 243         /* Mount all available cgroup controllers that are built into the kernel. */
 244
 245         if (!has_argument)
 246                 /* The defaults:
 247                  * mount "cpu" + "cpuacct" together, and "net_cls" + "net_prio".
 248                  *
 249                  * We'd like to add "cpuset" to the mix, but "cpuset" doesn't really
 250                  * work for groups with no initialized attributes.
 251                  */
 252                 join_controllers = (char**[]) {
 253                         STRV_MAKE("cpu", "cpuacct"),
 254                         STRV_MAKE("net_cls", "net_prio"),
 255                         NULL,
 256                 };
 257
 258         r = cg_kernel_controllers(&controllers);
 259         if (r < 0)
 260                 return log_error_errno(r, "Failed to enumerate cgroup controllers: %m");
 261
 262         for (;;) {
 263                 _cleanup_free_ char *options = NULL, *controller = NULL, *where = NULL;
 264                 MountPoint p = {
 265                         .what = "cgroup",
 266                         .type = "cgroup",
 267                         .flags = MS_NOSUID|MS_NOEXEC|MS_NODEV,
 268                         .mode = MNT_IN_CONTAINER,
 269                 };
 270                 char ***k = NULL;
 271
 272                 controller = set_steal_first(controllers);
 273                 if (!controller)
 274                         break;
 275
 276                 for (k = join_controllers; *k; k++)
 277                         if (strv_find(*k, controller))
 278                                 break;
 279
 280                 if (*k) {
 281                         char **i, **j;
 282
 283                         for (i = *k, j = *k; *i; i++) {
 284
 285                                 if (!streq(*i, controller)) {
 286                                         _cleanup_free_ char *t;
 287
 288                                         t = set_remove(controllers, *i);
 289                                         if (!t) {
 290                                                 if (has_argument)
 291                                                         free(*i);
 292                                                 continue;
 293                                         }
 294                                 }
 295
 296                                 *(j++) = *i;
 297                         }
 298
 299                         *j = NULL;
 300
 301                         options = strv_join(*k, ",");
 302                         if (!options)
 303                                 return log_oom();
 304                 } else
 305                         options = TAKE_PTR(controller);
 306
 307                 where = strappend("/sys/fs/cgroup/", options);
 308                 if (!where)
 309                         return log_oom();
 310
 311                 p.where = where;
 312                 p.options = options;
 313
 314                 r = mount_one(&p, true);
 315                 if (r < 0)
 316                         return r;
 317
 318                 if (r > 0 && *k) {
 319                         char **i;
 320
 321                         for (i = *k; *i; i++) {
 322                                 _cleanup_free_ char *t = NULL;
 323
 324                                 t = strappend("/sys/fs/cgroup/", *i);
 325                                 if (!t)
 326                                         return log_oom();
 327
 328                                 r = symlink(options, t);
 329                                 if (r >= 0) {
 330 #ifdef SMACK_RUN_LABEL
 331                                         _cleanup_free_ char *src;
 332                                         src = strappend("/sys/fs/cgroup/", options);
 333                                         if (!src)
 334                                                 return log_oom();
 335                                         r = mac_smack_copy(t, src);
 336                                         if (r < 0 && r != -EOPNOTSUPP)
 337                                                 return log_error_errno(r, "Failed to copy smack label from %s to %s: %m", src, t);
 338 #endif
 339                                 } else if (errno != EEXIST)
 340                                         return log_error_errno(errno, "Failed to create symlink %s: %m", t);
 341                         }
 342                 }
 343         }
 344
 345         /* Now that we mounted everything, let's make the tmpfs the
 346          * cgroup file systems are mounted into read-only. */
 347         (void) mount("tmpfs", "/sys/fs/cgroup", "tmpfs", MS_REMOUNT|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME|MS_RDONLY, "mode=755");
 348
 349         return 0;
 350 }
 351
 352 #if HAVE_SELINUX || ENABLE_SMACK
 353 static int nftw_cb(
 354                 const char *fpath,
 355                 const struct stat *sb,
 356                 int tflag,
 357                 struct FTW *ftwbuf) {
 358
 359         /* No need to label /dev twice in a row... */
 360         if (_unlikely_(ftwbuf->level == 0))
 361                 return FTW_CONTINUE;
 362
 363         (void) label_fix(fpath, 0);
 364
 365         /* /run/initramfs is static data and big, no need to
 366          * dynamically relabel its contents at boot... */
 367         if (_unlikely_(ftwbuf->level == 1 &&
 368                       tflag == FTW_D &&
 369                       streq(fpath, "/run/initramfs")))
 370                 return FTW_SKIP_SUBTREE;
 371
 372         return FTW_CONTINUE;
 373 };
 374
 375 static int relabel_cgroup_filesystems(void) {
 376         int r;
 377         struct statfs st;
 378
 379         r = cg_all_unified();
 380         if (r == 0) {
 381                 /* Temporarily remount the root cgroup filesystem to give it a proper label. Do this
 382                    only when the filesystem has been already populated by a previous instance of systemd
 383                    running from initrd. Otherwise don't remount anything and leave the filesystem read-write
 384                    for the cgroup filesystems to be mounted inside. */
 385                 if (statfs("/sys/fs/cgroup", &st) < 0)
 386                         return log_error_errno(errno, "Failed to determine mount flags for /sys/fs/cgroup: %m");
 387
 388                 if (st.f_flags & ST_RDONLY)
 389                         (void) mount(NULL, "/sys/fs/cgroup", NULL, MS_REMOUNT, NULL);
 390
 391                 (void) label_fix("/sys/fs/cgroup", 0);
 392                 (void) nftw("/sys/fs/cgroup", nftw_cb, 64, FTW_MOUNT|FTW_PHYS|FTW_ACTIONRETVAL);
 393
 394                 if (st.f_flags & ST_RDONLY)
 395                         (void) mount(NULL, "/sys/fs/cgroup", NULL, MS_REMOUNT|MS_RDONLY, NULL);
 396
 397         } else if (r < 0)
 398                 return log_error_errno(r, "Failed to determine whether we are in all unified mode: %m");
 399
 400         return 0;
 401 }
 402 #endif
 403
 404 int mount_setup(bool loaded_policy) {
 405         int r = 0;
 406
 407         r = mount_points_setup(ELEMENTSOF(mount_table), loaded_policy);
 408         if (r < 0)
 409                 return r;
 410
 411 #if HAVE_SELINUX || ENABLE_SMACK
 412         /* Nodes in devtmpfs and /run need to be manually updated for
 413          * the appropriate labels, after mounting. The other virtual
 414          * API file systems like /sys and /proc do not need that, they
 415          * use the same label for all their files. */
 416         if (loaded_policy) {
 417                 usec_t before_relabel, after_relabel;
 418                 char timespan[FORMAT_TIMESPAN_MAX];
 419
 420                 before_relabel = now(CLOCK_MONOTONIC);
 421
 422                 (void) nftw("/dev", nftw_cb, 64, FTW_MOUNT|FTW_PHYS|FTW_ACTIONRETVAL);
 423                 (void) nftw("/dev/shm", nftw_cb, 64, FTW_MOUNT|FTW_PHYS|FTW_ACTIONRETVAL);
 424                 (void) nftw("/run", nftw_cb, 64, FTW_MOUNT|FTW_PHYS|FTW_ACTIONRETVAL);
 425
 426                 r = relabel_cgroup_filesystems();
 427                 if (r < 0)
 428                         return r;
 429
 430                 after_relabel = now(CLOCK_MONOTONIC);
 431
 432                 log_info("Relabelled /dev, /run and /sys/fs/cgroup in %s.",
 433                          format_timespan(timespan, sizeof(timespan), after_relabel - before_relabel, 0));
 434         }
 435 #endif
 436
 437         /* Create a few default symlinks, which are normally created
 438          * by udevd, but some scripts might need them before we start
 439          * udevd. */
 440         dev_setup(NULL, UID_INVALID, GID_INVALID);
 441
 442         /* Mark the root directory as shared in regards to mount propagation. The kernel defaults to "private", but we
 443          * think it makes more sense to have a default of "shared" so that nspawn and the container tools work out of
 444          * the box. If specific setups need other settings they can reset the propagation mode to private if
 445          * needed. Note that we set this only when we are invoked directly by the kernel. If we are invoked by a
 446          * container manager we assume the container manager knows what it is doing (for example, because it set up
 447          * some directories with different propagation modes). */
 448         if (detect_container() <= 0)
 449                 if (mount(NULL, "/", NULL, MS_REC|MS_SHARED, NULL) < 0)
 450                         log_warning_errno(errno, "Failed to set up the root directory for shared mount propagation: %m");
 451
 452         /* Create a few directories we always want around, Note that sd_booted() checks for /run/systemd/system, so
 453          * this mkdir really needs to stay for good, otherwise software that copied sd-daemon.c into their sources will
 454          * misdetect systemd. */
 455         (void) mkdir_label("/run/systemd", 0755);
 456         (void) mkdir_label("/run/systemd/system", 0755);
 457
 458         /* Set up inaccessible (and empty) file nodes of all types */
 459         (void) mkdir_label("/run/systemd/inaccessible", 0000);
 460         (void) mknod("/run/systemd/inaccessible/reg", S_IFREG | 0000, 0);
 461         (void) mkdir_label("/run/systemd/inaccessible/dir", 0000);
 462         (void) mkfifo("/run/systemd/inaccessible/fifo", 0000);
 463         (void) mknod("/run/systemd/inaccessible/sock", S_IFSOCK | 0000, 0);
 464
 465         /* The following two are likely to fail if we lack the privs for it (for example in an userns environment, if
 466          * CAP_SYS_MKNOD is missing, or if a device node policy prohibit major/minor of 0 device nodes to be
 467          * created). But that's entirely fine. Consumers of these files should carry fallback to use a different node
 468          * then, for example /run/systemd/inaccessible/sock, which is close enough in behaviour and semantics for most
 469          * uses. */
 470         (void) mknod("/run/systemd/inaccessible/chr", S_IFCHR | 0000, makedev(0, 0));
 471         (void) mknod("/run/systemd/inaccessible/blk", S_IFBLK | 0000, makedev(0, 0));
 472
 473         return 0;
 474 }