src/core/namespace.c

   1 /***
   2   This file is part of systemd.
   3
   4   Copyright 2010 Lennart Poettering
   5
   6   systemd is free software; you can redistribute it and/or modify it
   7   under the terms of the GNU Lesser General Public License as published by
   8   the Free Software Foundation; either version 2.1 of the License, or
   9   (at your option) any later version.
  10
  11   systemd is distributed in the hope that it will be useful, but
  12   WITHOUT ANY WARRANTY; without even the implied warranty of
  13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14   Lesser General Public License for more details.
  15
  16   You should have received a copy of the GNU Lesser General Public License
  17   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  18 ***/
  19
  20 #include <errno.h>
  21 #include <sched.h>
  22 #include <stdio.h>
  23 #include <string.h>
  24 #include <sys/mount.h>
  25 #include <sys/stat.h>
  26 #include <unistd.h>
  27 #include <linux/fs.h>
  28
  29 #include "alloc-util.h"
  30 #include "base-filesystem.h"
  31 #include "dev-setup.h"
  32 #include "fd-util.h"
  33 #include "fs-util.h"
  34 #include "label.h"
  35 #include "loop-util.h"
  36 #include "loopback-setup.h"
  37 #include "missing.h"
  38 #include "mkdir.h"
  39 #include "mount-util.h"
  40 #include "namespace.h"
  41 #include "path-util.h"
  42 #include "selinux-util.h"
  43 #include "socket-util.h"
  44 #include "string-table.h"
  45 #include "string-util.h"
  46 #include "strv.h"
  47 #include "umask-util.h"
  48 #include "user-util.h"
  49 #include "util.h"
  50
  51 #define DEV_MOUNT_OPTIONS (MS_NOSUID|MS_STRICTATIME|MS_NOEXEC)
  52
  53 typedef enum MountMode {
  54         /* This is ordered by priority! */
  55         INACCESSIBLE,
  56         BIND_MOUNT,
  57         BIND_MOUNT_RECURSIVE,
  58         PRIVATE_TMP,
  59         PRIVATE_VAR_TMP,
  60         PRIVATE_DEV,
  61         BIND_DEV,
  62         EMPTY_DIR,
  63         SYSFS,
  64         PROCFS,
  65         READONLY,
  66         READWRITE,
  67 } MountMode;
  68
  69 typedef struct MountEntry {
  70         const char *path_const;   /* Memory allocated on stack or static */
  71         MountMode mode:5;
  72         bool ignore:1;            /* Ignore if path does not exist? */
  73         bool has_prefix:1;        /* Already is prefixed by the root dir? */
  74         bool read_only:1;         /* Shall this mount point be read-only? */
  75         char *path_malloc;        /* Use this instead of 'path' if we had to allocate memory */
  76         const char *source_const; /* The source path, for bind mounts */
  77         char *source_malloc;
  78 } MountEntry;
  79
  80 /* If MountAPIVFS= is used, let's mount /sys and /proc into the it, but only as a fallback if the user hasn't mounted
  81  * something there already. These mounts are hence overriden by any other explicitly configured mounts. */
  82 static const MountEntry apivfs_table[] = {
  83         { "/proc",               PROCFS,       false },
  84         { "/dev",                BIND_DEV,     false },
  85         { "/sys",                SYSFS,        false },
  86 };
  87
  88 /* ProtectKernelTunables= option and the related filesystem APIs */
  89 static const MountEntry protect_kernel_tunables_table[] = {
  90         { "/proc/sys",           READONLY,     false },
  91         { "/proc/sysrq-trigger", READONLY,     true  },
  92         { "/proc/latency_stats", READONLY,     true  },
  93         { "/proc/mtrr",          READONLY,     true  },
  94         { "/proc/apm",           READONLY,     true  }, /* Obsolete API, there's no point in permitting access to this, ever */
  95         { "/proc/acpi",          READONLY,     true  },
  96         { "/proc/timer_stats",   READONLY,     true  },
  97         { "/proc/asound",        READONLY,     true  },
  98         { "/proc/bus",           READONLY,     true  },
  99         { "/proc/fs",            READONLY,     true  },
 100         { "/proc/irq",           READONLY,     true  },
 101         { "/sys",                READONLY,     false },
 102         { "/sys/kernel/debug",   READONLY,     true  },
 103         { "/sys/kernel/tracing", READONLY,     true  },
 104         { "/sys/fs/cgroup",      READWRITE,    false }, /* READONLY is set by ProtectControlGroups= option */
 105         { "/sys/fs/selinux",     READWRITE,    true  },
 106 };
 107
 108 /* ProtectKernelModules= option */
 109 static const MountEntry protect_kernel_modules_table[] = {
 110 #if HAVE_SPLIT_USR
 111         { "/lib/modules",        INACCESSIBLE, true  },
 112 #endif
 113         { "/usr/lib/modules",    INACCESSIBLE, true  },
 114 };
 115
 116 /*
 117  * ProtectHome=read-only table, protect $HOME and $XDG_RUNTIME_DIR and rest of
 118  * system should be protected by ProtectSystem=
 119  */
 120 static const MountEntry protect_home_read_only_table[] = {
 121         { "/home",               READONLY,     true  },
 122         { "/run/user",           READONLY,     true  },
 123         { "/root",               READONLY,     true  },
 124 };
 125
 126 /* ProtectHome=yes table */
 127 static const MountEntry protect_home_yes_table[] = {
 128         { "/home",               INACCESSIBLE, true  },
 129         { "/run/user",           INACCESSIBLE, true  },
 130         { "/root",               INACCESSIBLE, true  },
 131 };
 132
 133 /* ProtectSystem=yes table */
 134 static const MountEntry protect_system_yes_table[] = {
 135         { "/usr",                READONLY,     false },
 136         { "/boot",               READONLY,     true  },
 137         { "/efi",                READONLY,     true  },
 138 };
 139
 140 /* ProtectSystem=full includes ProtectSystem=yes */
 141 static const MountEntry protect_system_full_table[] = {
 142         { "/usr",                READONLY,     false },
 143         { "/boot",               READONLY,     true  },
 144         { "/efi",                READONLY,     true  },
 145         { "/etc",                READONLY,     false },
 146 };
 147
 148 /*
 149  * ProtectSystem=strict table. In this strict mode, we mount everything
 150  * read-only, except for /proc, /dev, /sys which are the kernel API VFS,
 151  * which are left writable, but PrivateDevices= + ProtectKernelTunables=
 152  * protect those, and these options should be fully orthogonal.
 153  * (And of course /home and friends are also left writable, as ProtectHome=
 154  * shall manage those, orthogonally).
 155  */
 156 static const MountEntry protect_system_strict_table[] = {
 157         { "/",                   READONLY,     false },
 158         { "/proc",               READWRITE,    false },      /* ProtectKernelTunables= */
 159         { "/sys",                READWRITE,    false },      /* ProtectKernelTunables= */
 160         { "/dev",                READWRITE,    false },      /* PrivateDevices= */
 161         { "/home",               READWRITE,    true  },      /* ProtectHome= */
 162         { "/run/user",           READWRITE,    true  },      /* ProtectHome= */
 163         { "/root",               READWRITE,    true  },      /* ProtectHome= */
 164 };
 165
 166 static const char *mount_entry_path(const MountEntry *p) {
 167         assert(p);
 168
 169         /* Returns the path of this bind mount. If the malloc()-allocated ->path_buffer field is set we return that,
 170          * otherwise the stack/static ->path field is returned. */
 171
 172         return p->path_malloc ?: p->path_const;
 173 }
 174
 175 static bool mount_entry_read_only(const MountEntry *p) {
 176         assert(p);
 177
 178         return p->read_only || IN_SET(p->mode, READONLY, INACCESSIBLE);
 179 }
 180
 181 static const char *mount_entry_source(const MountEntry *p) {
 182         assert(p);
 183
 184         return p->source_malloc ?: p->source_const;
 185 }
 186
 187 static void mount_entry_done(MountEntry *p) {
 188         assert(p);
 189
 190         p->path_malloc = mfree(p->path_malloc);
 191         p->source_malloc = mfree(p->source_malloc);
 192 }
 193
 194 static int append_access_mounts(MountEntry **p, char **strv, MountMode mode) {
 195         char **i;
 196
 197         assert(p);
 198
 199         /* Adds a list of user-supplied READWRITE/READONLY/INACCESSIBLE entries */
 200
 201         STRV_FOREACH(i, strv) {
 202                 bool ignore = false, needs_prefix = false;
 203                 const char *e = *i;
 204
 205                 /* Look for any prefixes */
 206                 if (startswith(e, "-")) {
 207                         e++;
 208                         ignore = true;
 209                 }
 210                 if (startswith(e, "+")) {
 211                         e++;
 212                         needs_prefix = true;
 213                 }
 214
 215                 if (!path_is_absolute(e))
 216                         return -EINVAL;
 217
 218                 *((*p)++) = (MountEntry) {
 219                         .path_const = e,
 220                         .mode = mode,
 221                         .ignore = ignore,
 222                         .has_prefix = !needs_prefix,
 223                 };
 224         }
 225
 226         return 0;
 227 }
 228
 229 static int append_empty_dir_mounts(MountEntry **p, char **strv) {
 230         char **i;
 231
 232         assert(p);
 233
 234         /* Adds tmpfs mounts to provide readable but empty directories. This is primarily used to implement the
 235          * "/private/" boundary directories for DynamicUser=1. */
 236
 237         STRV_FOREACH(i, strv) {
 238
 239                 *((*p)++) = (MountEntry) {
 240                         .path_const = *i,
 241                         .mode = EMPTY_DIR,
 242                         .ignore = false,
 243                         .has_prefix = false,
 244                         .read_only = true,
 245                 };
 246         }
 247
 248         return 0;
 249 }
 250
 251 static int append_bind_mounts(MountEntry **p, const BindMount *binds, unsigned n) {
 252         unsigned i;
 253
 254         assert(p);
 255
 256         for (i = 0; i < n; i++) {
 257                 const BindMount *b = binds + i;
 258
 259                 *((*p)++) = (MountEntry) {
 260                         .path_const = b->destination,
 261                         .mode = b->recursive ? BIND_MOUNT_RECURSIVE : BIND_MOUNT,
 262                         .read_only = b->read_only,
 263                         .source_const = b->source,
 264                 };
 265         }
 266
 267         return 0;
 268 }
 269
 270 static int append_static_mounts(MountEntry **p, const MountEntry *mounts, unsigned n, bool ignore_protect) {
 271         unsigned i;
 272
 273         assert(p);
 274         assert(mounts);
 275
 276         /* Adds a list of static pre-defined entries */
 277
 278         for (i = 0; i < n; i++)
 279                 *((*p)++) = (MountEntry) {
 280                         .path_const = mount_entry_path(mounts+i),
 281                         .mode = mounts[i].mode,
 282                         .ignore = mounts[i].ignore || ignore_protect,
 283                 };
 284
 285         return 0;
 286 }
 287
 288 static int append_protect_home(MountEntry **p, ProtectHome protect_home, bool ignore_protect) {
 289         assert(p);
 290
 291         switch (protect_home) {
 292
 293         case PROTECT_HOME_NO:
 294                 return 0;
 295
 296         case PROTECT_HOME_READ_ONLY:
 297                 return append_static_mounts(p, protect_home_read_only_table, ELEMENTSOF(protect_home_read_only_table), ignore_protect);
 298
 299         case PROTECT_HOME_YES:
 300                 return append_static_mounts(p, protect_home_yes_table, ELEMENTSOF(protect_home_yes_table), ignore_protect);
 301
 302         default:
 303                 assert_not_reached("Unexpected ProtectHome= value");
 304         }
 305 }
 306
 307 static int append_protect_system(MountEntry **p, ProtectSystem protect_system, bool ignore_protect) {
 308         assert(p);
 309
 310         switch (protect_system) {
 311
 312         case PROTECT_SYSTEM_NO:
 313                 return 0;
 314
 315         case PROTECT_SYSTEM_STRICT:
 316                 return append_static_mounts(p, protect_system_strict_table, ELEMENTSOF(protect_system_strict_table), ignore_protect);
 317
 318         case PROTECT_SYSTEM_YES:
 319                 return append_static_mounts(p, protect_system_yes_table, ELEMENTSOF(protect_system_yes_table), ignore_protect);
 320
 321         case PROTECT_SYSTEM_FULL:
 322                 return append_static_mounts(p, protect_system_full_table, ELEMENTSOF(protect_system_full_table), ignore_protect);
 323
 324         default:
 325                 assert_not_reached("Unexpected ProtectSystem= value");
 326         }
 327 }
 328
 329 static int mount_path_compare(const void *a, const void *b) {
 330         const MountEntry *p = a, *q = b;
 331         int d;
 332
 333         /* If the paths are not equal, then order prefixes first */
 334         d = path_compare(mount_entry_path(p), mount_entry_path(q));
 335         if (d != 0)
 336                 return d;
 337
 338         /* If the paths are equal, check the mode */
 339         if (p->mode < q->mode)
 340                 return -1;
 341
 342         if (p->mode > q->mode)
 343                 return 1;
 344
 345         return 0;
 346 }
 347
 348 static int prefix_where_needed(MountEntry *m, unsigned n, const char *root_directory) {
 349         unsigned i;
 350
 351         /* Prefixes all paths in the bind mount table with the root directory if it is specified and the entry needs
 352          * that. */
 353
 354         if (!root_directory)
 355                 return 0;
 356
 357         for (i = 0; i < n; i++) {
 358                 char *s;
 359
 360                 if (m[i].has_prefix)
 361                         continue;
 362
 363                 s = prefix_root(root_directory, mount_entry_path(m+i));
 364                 if (!s)
 365                         return -ENOMEM;
 366
 367                 free(m[i].path_malloc);
 368                 m[i].path_malloc = s;
 369
 370                 m[i].has_prefix = true;
 371         }
 372
 373         return 0;
 374 }
 375
 376 static void drop_duplicates(MountEntry *m, unsigned *n) {
 377         MountEntry *f, *t, *previous;
 378
 379         assert(m);
 380         assert(n);
 381
 382         /* Drops duplicate entries. Expects that the array is properly ordered already. */
 383
 384         for (f = m, t = m, previous = NULL; f < m + *n; f++) {
 385
 386                 /* The first one wins (which is the one with the more restrictive mode), see mount_path_compare()
 387                  * above. */
 388                 if (previous && path_equal(mount_entry_path(f), mount_entry_path(previous))) {
 389                         log_debug("%s is duplicate.", mount_entry_path(f));
 390                         previous->read_only = previous->read_only || mount_entry_read_only(f); /* Propagate the read-only flag to the remaining entry */
 391                         mount_entry_done(f);
 392                         continue;
 393                 }
 394
 395                 *t = *f;
 396                 previous = t;
 397                 t++;
 398         }
 399
 400         *n = t - m;
 401 }
 402
 403 static void drop_inaccessible(MountEntry *m, unsigned *n) {
 404         MountEntry *f, *t;
 405         const char *clear = NULL;
 406
 407         assert(m);
 408         assert(n);
 409
 410         /* Drops all entries obstructed by another entry further up the tree. Expects that the array is properly
 411          * ordered already. */
 412
 413         for (f = m, t = m; f < m + *n; f++) {
 414
 415                 /* If we found a path set for INACCESSIBLE earlier, and this entry has it as prefix we should drop
 416                  * it, as inaccessible paths really should drop the entire subtree. */
 417                 if (clear && path_startswith(mount_entry_path(f), clear)) {
 418                         log_debug("%s is masked by %s.", mount_entry_path(f), clear);
 419                         mount_entry_done(f);
 420                         continue;
 421                 }
 422
 423                 clear = f->mode == INACCESSIBLE ? mount_entry_path(f) : NULL;
 424
 425                 *t = *f;
 426                 t++;
 427         }
 428
 429         *n = t - m;
 430 }
 431
 432 static void drop_nop(MountEntry *m, unsigned *n) {
 433         MountEntry *f, *t;
 434
 435         assert(m);
 436         assert(n);
 437
 438         /* Drops all entries which have an immediate parent that has the same type, as they are redundant. Assumes the
 439          * list is ordered by prefixes. */
 440
 441         for (f = m, t = m; f < m + *n; f++) {
 442
 443                 /* Only suppress such subtrees for READONLY and READWRITE entries */
 444                 if (IN_SET(f->mode, READONLY, READWRITE)) {
 445                         MountEntry *p;
 446                         bool found = false;
 447
 448                         /* Now let's find the first parent of the entry we are looking at. */
 449                         for (p = t-1; p >= m; p--) {
 450                                 if (path_startswith(mount_entry_path(f), mount_entry_path(p))) {
 451                                         found = true;
 452                                         break;
 453                                 }
 454                         }
 455
 456                         /* We found it, let's see if it's the same mode, if so, we can drop this entry */
 457                         if (found && p->mode == f->mode) {
 458                                 log_debug("%s is redundant by %s", mount_entry_path(f), mount_entry_path(p));
 459                                 mount_entry_done(f);
 460                                 continue;
 461                         }
 462                 }
 463
 464                 *t = *f;
 465                 t++;
 466         }
 467
 468         *n = t - m;
 469 }
 470
 471 static void drop_outside_root(const char *root_directory, MountEntry *m, unsigned *n) {
 472         MountEntry *f, *t;
 473
 474         assert(m);
 475         assert(n);
 476
 477         /* Nothing to do */
 478         if (!root_directory)
 479                 return;
 480
 481         /* Drops all mounts that are outside of the root directory. */
 482
 483         for (f = m, t = m; f < m + *n; f++) {
 484
 485                 if (!path_startswith(mount_entry_path(f), root_directory)) {
 486                         log_debug("%s is outside of root directory.", mount_entry_path(f));
 487                         mount_entry_done(f);
 488                         continue;
 489                 }
 490
 491                 *t = *f;
 492                 t++;
 493         }
 494
 495         *n = t - m;
 496 }
 497
 498 static int mount_private_dev(MountEntry *m) {
 499         static const char devnodes[] =
 500                 "/dev/null\0"
 501                 "/dev/zero\0"
 502                 "/dev/full\0"
 503                 "/dev/random\0"
 504                 "/dev/urandom\0"
 505                 "/dev/tty\0";
 506
 507         char temporary_mount[] = "/tmp/namespace-dev-XXXXXX";
 508         const char *d, *dev = NULL, *devpts = NULL, *devshm = NULL, *devhugepages = NULL, *devmqueue = NULL, *devlog = NULL, *devptmx = NULL;
 509         _cleanup_umask_ mode_t u;
 510         int r;
 511
 512         assert(m);
 513
 514         u = umask(0000);
 515
 516         if (!mkdtemp(temporary_mount))
 517                 return -errno;
 518
 519         dev = strjoina(temporary_mount, "/dev");
 520         (void) mkdir(dev, 0755);
 521         if (mount("tmpfs", dev, "tmpfs", DEV_MOUNT_OPTIONS, "mode=755") < 0) {
 522                 r = -errno;
 523                 goto fail;
 524         }
 525
 526         devpts = strjoina(temporary_mount, "/dev/pts");
 527         (void) mkdir(devpts, 0755);
 528         if (mount("/dev/pts", devpts, NULL, MS_BIND, NULL) < 0) {
 529                 r = -errno;
 530                 goto fail;
 531         }
 532
 533         devptmx = strjoina(temporary_mount, "/dev/ptmx");
 534         if (symlink("pts/ptmx", devptmx) < 0) {
 535                 r = -errno;
 536                 goto fail;
 537         }
 538
 539         devshm = strjoina(temporary_mount, "/dev/shm");
 540         (void) mkdir(devshm, 01777);
 541         r = mount("/dev/shm", devshm, NULL, MS_BIND, NULL);
 542         if (r < 0) {
 543                 r = -errno;
 544                 goto fail;
 545         }
 546
 547         devmqueue = strjoina(temporary_mount, "/dev/mqueue");
 548         (void) mkdir(devmqueue, 0755);
 549         (void) mount("/dev/mqueue", devmqueue, NULL, MS_BIND, NULL);
 550
 551         devhugepages = strjoina(temporary_mount, "/dev/hugepages");
 552         (void) mkdir(devhugepages, 0755);
 553         (void) mount("/dev/hugepages", devhugepages, NULL, MS_BIND, NULL);
 554
 555         devlog = strjoina(temporary_mount, "/dev/log");
 556         (void) symlink("/run/systemd/journal/dev-log", devlog);
 557
 558         NULSTR_FOREACH(d, devnodes) {
 559                 _cleanup_free_ char *dn = NULL;
 560                 struct stat st;
 561
 562                 r = stat(d, &st);
 563                 if (r < 0) {
 564
 565                         if (errno == ENOENT)
 566                                 continue;
 567
 568                         r = -errno;
 569                         goto fail;
 570                 }
 571
 572                 if (!S_ISBLK(st.st_mode) &&
 573                     !S_ISCHR(st.st_mode)) {
 574                         r = -EINVAL;
 575                         goto fail;
 576                 }
 577
 578                 if (st.st_rdev == 0)
 579                         continue;
 580
 581                 dn = strappend(temporary_mount, d);
 582                 if (!dn) {
 583                         r = -ENOMEM;
 584                         goto fail;
 585                 }
 586
 587                 mac_selinux_create_file_prepare(d, st.st_mode);
 588                 r = mknod(dn, st.st_mode, st.st_rdev);
 589                 mac_selinux_create_file_clear();
 590
 591                 if (r < 0) {
 592                         r = -errno;
 593                         goto fail;
 594                 }
 595         }
 596
 597         dev_setup(temporary_mount, UID_INVALID, GID_INVALID);
 598
 599         /* Create the /dev directory if missing. It is more likely to be
 600          * missing when the service is started with RootDirectory. This is
 601          * consistent with mount units creating the mount points when missing.
 602          */
 603         (void) mkdir_p_label(mount_entry_path(m), 0755);
 604
 605         /* Unmount everything in old /dev */
 606         umount_recursive(mount_entry_path(m), 0);
 607         if (mount(dev, mount_entry_path(m), NULL, MS_MOVE, NULL) < 0) {
 608                 r = -errno;
 609                 goto fail;
 610         }
 611
 612         rmdir(dev);
 613         rmdir(temporary_mount);
 614
 615         return 0;
 616
 617 fail:
 618         if (devpts)
 619                 umount(devpts);
 620
 621         if (devshm)
 622                 umount(devshm);
 623
 624         if (devhugepages)
 625                 umount(devhugepages);
 626
 627         if (devmqueue)
 628                 umount(devmqueue);
 629
 630         umount(dev);
 631         rmdir(dev);
 632         rmdir(temporary_mount);
 633
 634         return r;
 635 }
 636
 637 static int mount_bind_dev(MountEntry *m) {
 638         int r;
 639
 640         assert(m);
 641
 642         /* Implements the little brother of mount_private_dev(): simply bind mounts the host's /dev into the service's
 643          * /dev. This is only used when RootDirectory= is set. */
 644
 645         (void) mkdir_p_label(mount_entry_path(m), 0755);
 646
 647         r = path_is_mount_point(mount_entry_path(m), NULL, 0);
 648         if (r < 0)
 649                 return log_debug_errno(r, "Unable to determine whether /dev is already mounted: %m");
 650         if (r > 0) /* make this a NOP if /dev is already a mount point */
 651                 return 0;
 652
 653         if (mount("/dev", mount_entry_path(m), NULL, MS_BIND|MS_REC, NULL) < 0)
 654                 return log_debug_errno(errno, "Failed to bind mount %s: %m", mount_entry_path(m));
 655
 656         return 1;
 657 }
 658
 659 static int mount_sysfs(MountEntry *m) {
 660         int r;
 661
 662         assert(m);
 663
 664         (void) mkdir_p_label(mount_entry_path(m), 0755);
 665
 666         r = path_is_mount_point(mount_entry_path(m), NULL, 0);
 667         if (r < 0)
 668                 return log_debug_errno(r, "Unable to determine whether /sys is already mounted: %m");
 669         if (r > 0) /* make this a NOP if /sys is already a mount point */
 670                 return 0;
 671
 672         /* Bind mount the host's version so that we get all child mounts of it, too. */
 673         if (mount("/sys", mount_entry_path(m), NULL, MS_BIND|MS_REC, NULL) < 0)
 674                 return log_debug_errno(errno, "Failed to mount %s: %m", mount_entry_path(m));
 675
 676         return 1;
 677 }
 678
 679 static int mount_procfs(MountEntry *m) {
 680         int r;
 681
 682         assert(m);
 683
 684         (void) mkdir_p_label(mount_entry_path(m), 0755);
 685
 686         r = path_is_mount_point(mount_entry_path(m), NULL, 0);
 687         if (r < 0)
 688                 return log_debug_errno(r, "Unable to determine whether /proc is already mounted: %m");
 689         if (r > 0) /* make this a NOP if /proc is already a mount point */
 690                 return 0;
 691
 692         /* Mount a new instance, so that we get the one that matches our user namespace, if we are running in one */
 693         if (mount("proc", mount_entry_path(m), "proc", MS_NOSUID|MS_NOEXEC|MS_NODEV, NULL) < 0)
 694                 return log_debug_errno(errno, "Failed to mount %s: %m", mount_entry_path(m));
 695
 696         return 1;
 697 }
 698
 699 static int mount_empty_dir(MountEntry *m) {
 700         assert(m);
 701
 702         /* First, get rid of everything that is below if there is anything. Then, overmount with our new empty dir */
 703
 704         (void) mkdir_p_label(mount_entry_path(m), 0755);
 705         (void) umount_recursive(mount_entry_path(m), 0);
 706
 707         if (mount("tmpfs", mount_entry_path(m), "tmpfs", MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_STRICTATIME, "mode=755") < 0)
 708                 return log_debug_errno(errno, "Failed to mount %s: %m", mount_entry_path(m));
 709
 710         return 1;
 711 }
 712
 713 static int mount_entry_chase(
 714                 const char *root_directory,
 715                 MountEntry *m,
 716                 const char *path,
 717                 char **location) {
 718
 719         char *chased;
 720         int r;
 721
 722         assert(m);
 723
 724         /* Since mount() will always follow symlinks and we need to take the different root directory into account we
 725          * chase the symlinks on our own first. This is called for the destination path, as well as the source path (if
 726          * that applies). The result is stored in "location". */
 727
 728         r = chase_symlinks(path, root_directory,
 729                            IN_SET(m->mode, BIND_MOUNT, BIND_MOUNT_RECURSIVE, PRIVATE_TMP, PRIVATE_VAR_TMP, PRIVATE_DEV, BIND_DEV, EMPTY_DIR, SYSFS, PROCFS) ? CHASE_NONEXISTENT : 0,
 730                            &chased);
 731         if (r == -ENOENT && m->ignore) {
 732                 log_debug_errno(r, "Path %s does not exist, ignoring.", path);
 733                 return 0;
 734         }
 735         if (r < 0)
 736                 return log_debug_errno(r, "Failed to follow symlinks on %s: %m", path);
 737
 738         log_debug("Followed symlinks %s → %s.", path, chased);
 739
 740         free(*location);
 741         *location = chased;
 742
 743         return 1;
 744 }
 745
 746 static int apply_mount(
 747                 const char *root_directory,
 748                 MountEntry *m,
 749                 const char *tmp_dir,
 750                 const char *var_tmp_dir) {
 751
 752         bool rbind = true, make = false;
 753         const char *what;
 754         int r;
 755
 756         assert(m);
 757
 758         r = mount_entry_chase(root_directory, m, mount_entry_path(m), &m->path_malloc);
 759         if (r <= 0)
 760                 return r;
 761
 762         log_debug("Applying namespace mount on %s", mount_entry_path(m));
 763
 764         switch (m->mode) {
 765
 766         case INACCESSIBLE: {
 767                 struct stat target;
 768
 769                 /* First, get rid of everything that is below if there
 770                  * is anything... Then, overmount it with an
 771                  * inaccessible path. */
 772                 (void) umount_recursive(mount_entry_path(m), 0);
 773
 774                 if (lstat(mount_entry_path(m), &target) < 0)
 775                         return log_debug_errno(errno, "Failed to lstat() %s to determine what to mount over it: %m", mount_entry_path(m));
 776
 777                 what = mode_to_inaccessible_node(target.st_mode);
 778                 if (!what) {
 779                         log_debug("File type not supported for inaccessible mounts. Note that symlinks are not allowed");
 780                         return -ELOOP;
 781                 }
 782                 break;
 783         }
 784
 785         case READONLY:
 786         case READWRITE:
 787                 r = path_is_mount_point(mount_entry_path(m), root_directory, 0);
 788                 if (r < 0)
 789                         return log_debug_errno(r, "Failed to determine whether %s is already a mount point: %m", mount_entry_path(m));
 790                 if (r > 0) /* Nothing to do here, it is already a mount. We just later toggle the MS_RDONLY bit for the mount point if needed. */
 791                         return 0;
 792                 /* This isn't a mount point yet, let's make it one. */
 793                 what = mount_entry_path(m);
 794                 break;
 795
 796         case BIND_MOUNT:
 797                 rbind = false;
 798                 /* fallthrough */
 799
 800         case BIND_MOUNT_RECURSIVE:
 801                 /* Also chase the source mount */
 802
 803                 r = mount_entry_chase(root_directory, m, mount_entry_source(m), &m->source_malloc);
 804                 if (r <= 0)
 805                         return r;
 806
 807                 what = mount_entry_source(m);
 808                 make = true;
 809                 break;
 810
 811         case EMPTY_DIR:
 812                 return mount_empty_dir(m);
 813
 814         case PRIVATE_TMP:
 815                 what = tmp_dir;
 816                 make = true;
 817                 break;
 818
 819         case PRIVATE_VAR_TMP:
 820                 what = var_tmp_dir;
 821                 make = true;
 822                 break;
 823
 824         case PRIVATE_DEV:
 825                 return mount_private_dev(m);
 826
 827         case BIND_DEV:
 828                 return mount_bind_dev(m);
 829
 830         case SYSFS:
 831                 return mount_sysfs(m);
 832
 833         case PROCFS:
 834                 return mount_procfs(m);
 835
 836         default:
 837                 assert_not_reached("Unknown mode");
 838         }
 839
 840         assert(what);
 841
 842         if (mount(what, mount_entry_path(m), NULL, MS_BIND|(rbind ? MS_REC : 0), NULL) < 0) {
 843                 bool try_again = false;
 844                 r = -errno;
 845
 846                 if (r == -ENOENT && make) {
 847                         struct stat st;
 848
 849                         /* Hmm, either the source or the destination are missing. Let's see if we can create the destination, then try again */
 850
 851                         if (stat(what, &st) >= 0) {
 852
 853                                 (void) mkdir_parents(mount_entry_path(m), 0755);
 854
 855                                 if (S_ISDIR(st.st_mode))
 856                                         try_again = mkdir(mount_entry_path(m), 0755) >= 0;
 857                                 else
 858                                         try_again = touch(mount_entry_path(m)) >= 0;
 859                         }
 860                 }
 861
 862                 if (try_again) {
 863                         if (mount(what, mount_entry_path(m), NULL, MS_BIND|(rbind ? MS_REC : 0), NULL) < 0)
 864                                 r = -errno;
 865                         else
 866                                 r = 0;
 867                 }
 868
 869                 if (r < 0)
 870                         return log_debug_errno(r, "Failed to mount %s to %s: %m", what, mount_entry_path(m));
 871         }
 872
 873         log_debug("Successfully mounted %s to %s", what, mount_entry_path(m));
 874         return 0;
 875 }
 876
 877 static int make_read_only(MountEntry *m, char **blacklist, FILE *proc_self_mountinfo) {
 878         int r = 0;
 879
 880         assert(m);
 881         assert(proc_self_mountinfo);
 882
 883         if (mount_entry_read_only(m))
 884                 r = bind_remount_recursive_with_mountinfo(mount_entry_path(m), true, blacklist, proc_self_mountinfo);
 885         else if (m->mode == PRIVATE_DEV) { /* Superblock can be readonly but the submounts can't */
 886                 if (mount(NULL, mount_entry_path(m), NULL, MS_REMOUNT|DEV_MOUNT_OPTIONS|MS_RDONLY, NULL) < 0)
 887                         r = -errno;
 888         } else
 889                 return 0;
 890
 891         /* Not that we only turn on the MS_RDONLY flag here, we never turn it off. Something that was marked read-only
 892          * already stays this way. This improves compatibility with container managers, where we won't attempt to undo
 893          * read-only mounts already applied. */
 894
 895         if (r == -ENOENT && m->ignore)
 896                 r = 0;
 897
 898         return r;
 899 }
 900
 901 static bool namespace_info_mount_apivfs(const char *root_directory, const NameSpaceInfo *ns_info) {
 902         assert(ns_info);
 903
 904         /*
 905          * ProtectControlGroups= and ProtectKernelTunables= imply MountAPIVFS=,
 906          * since to protect the API VFS mounts, they need to be around in the
 907          * first place... and RootDirectory= or RootImage= need to be set.
 908          */
 909
 910         /* root_directory should point to a mount point */
 911         return root_directory &&
 912                 (ns_info->mount_apivfs ||
 913                  ns_info->protect_control_groups ||
 914                  ns_info->protect_kernel_tunables);
 915 }
 916
 917 static unsigned namespace_calculate_mounts(
 918                 const char* root_directory,
 919                 const NameSpaceInfo *ns_info,
 920                 char** read_write_paths,
 921                 char** read_only_paths,
 922                 char** inaccessible_paths,
 923                 char** empty_directories,
 924                 const BindMount *bind_mounts,
 925                 unsigned n_bind_mounts,
 926                 const char* tmp_dir,
 927                 const char* var_tmp_dir,
 928                 ProtectHome protect_home,
 929                 ProtectSystem protect_system) {
 930
 931         unsigned protect_home_cnt;
 932         unsigned protect_system_cnt =
 933                 (protect_system == PROTECT_SYSTEM_STRICT ?
 934                  ELEMENTSOF(protect_system_strict_table) :
 935                  ((protect_system == PROTECT_SYSTEM_FULL) ?
 936                   ELEMENTSOF(protect_system_full_table) :
 937                   ((protect_system == PROTECT_SYSTEM_YES) ?
 938                    ELEMENTSOF(protect_system_yes_table) : 0)));
 939
 940         protect_home_cnt =
 941                 (protect_home == PROTECT_HOME_YES ?
 942                  ELEMENTSOF(protect_home_yes_table) :
 943                  ((protect_home == PROTECT_HOME_READ_ONLY) ?
 944                   ELEMENTSOF(protect_home_read_only_table) : 0));
 945
 946         return !!tmp_dir + !!var_tmp_dir +
 947                 strv_length(read_write_paths) +
 948                 strv_length(read_only_paths) +
 949                 strv_length(inaccessible_paths) +
 950                 strv_length(empty_directories) +
 951                 n_bind_mounts +
 952                 ns_info->private_dev +
 953                 (ns_info->protect_kernel_tunables ? ELEMENTSOF(protect_kernel_tunables_table) : 0) +
 954                 (ns_info->protect_control_groups ? 1 : 0) +
 955                 (ns_info->protect_kernel_modules ? ELEMENTSOF(protect_kernel_modules_table) : 0) +
 956                 protect_home_cnt + protect_system_cnt +
 957                 (namespace_info_mount_apivfs(root_directory, ns_info) ? ELEMENTSOF(apivfs_table) : 0);
 958 }
 959
 960 int setup_namespace(
 961                 const char* root_directory,
 962                 const char* root_image,
 963                 const NameSpaceInfo *ns_info,
 964                 char** read_write_paths,
 965                 char** read_only_paths,
 966                 char** inaccessible_paths,
 967                 char** empty_directories,
 968                 const BindMount *bind_mounts,
 969                 unsigned n_bind_mounts,
 970                 const char* tmp_dir,
 971                 const char* var_tmp_dir,
 972                 ProtectHome protect_home,
 973                 ProtectSystem protect_system,
 974                 unsigned long mount_flags,
 975                 DissectImageFlags dissect_image_flags) {
 976
 977         _cleanup_(loop_device_unrefp) LoopDevice *loop_device = NULL;
 978         _cleanup_(decrypted_image_unrefp) DecryptedImage *decrypted_image = NULL;
 979         _cleanup_(dissected_image_unrefp) DissectedImage *dissected_image = NULL;
 980         _cleanup_free_ void *root_hash = NULL;
 981         MountEntry *m, *mounts = NULL;
 982         size_t root_hash_size = 0;
 983         bool make_slave = false;
 984         const char *root;
 985         unsigned n_mounts;
 986         int r = 0;
 987
 988         assert(ns_info);
 989
 990         if (mount_flags == 0)
 991                 mount_flags = MS_SHARED;
 992
 993         if (root_image) {
 994                 dissect_image_flags |= DISSECT_IMAGE_REQUIRE_ROOT;
 995
 996                 if (protect_system == PROTECT_SYSTEM_STRICT && strv_isempty(read_write_paths))
 997                         dissect_image_flags |= DISSECT_IMAGE_READ_ONLY;
 998
 999                 r = loop_device_make_by_path(root_image,
1000                                              dissect_image_flags & DISSECT_IMAGE_READ_ONLY ? O_RDONLY : O_RDWR,
1001                                              &loop_device);
1002                 if (r < 0)
1003                         return r;
1004
1005                 r = root_hash_load(root_image, &root_hash, &root_hash_size);
1006                 if (r < 0)
1007                         return r;
1008
1009                 r = dissect_image(loop_device->fd, root_hash, root_hash_size, dissect_image_flags, &dissected_image);
1010                 if (r < 0)
1011                         return r;
1012
1013                 r = dissected_image_decrypt(dissected_image, NULL, root_hash, root_hash_size, dissect_image_flags, &decrypted_image);
1014                 if (r < 0)
1015                         return r;
1016         }
1017
1018         if (root_directory)
1019                 root = root_directory;
1020         else if (root_image || n_bind_mounts > 0) {
1021
1022                 /* If we are booting from an image, create a mount point for the image, if it's still missing. We use
1023                  * the same mount point for all images, which is safe, since they all live in their own namespaces
1024                  * after all, and hence won't see each other. We also use such a root directory whenever there are bind
1025                  * mounts configured, so that their source mounts are never obstructed by mounts we already applied
1026                  * while we are applying them. */
1027
1028                 root = "/run/systemd/unit-root";
1029                 (void) mkdir_label(root, 0700);
1030         } else
1031                 root = NULL;
1032
1033         n_mounts = namespace_calculate_mounts(
1034                         root,
1035                         ns_info,
1036                         read_write_paths,
1037                         read_only_paths,
1038                         inaccessible_paths,
1039                         empty_directories,
1040                         bind_mounts, n_bind_mounts,
1041                         tmp_dir, var_tmp_dir,
1042                         protect_home, protect_system);
1043
1044         /* Set mount slave mode */
1045         if (root || n_mounts > 0)
1046                 make_slave = true;
1047
1048         if (n_mounts > 0) {
1049                 m = mounts = (MountEntry *) alloca0(n_mounts * sizeof(MountEntry));
1050                 r = append_access_mounts(&m, read_write_paths, READWRITE);
1051                 if (r < 0)
1052                         goto finish;
1053
1054                 r = append_access_mounts(&m, read_only_paths, READONLY);
1055                 if (r < 0)
1056                         goto finish;
1057
1058                 r = append_access_mounts(&m, inaccessible_paths, INACCESSIBLE);
1059                 if (r < 0)
1060                         goto finish;
1061
1062                 r = append_empty_dir_mounts(&m, empty_directories);
1063                 if (r < 0)
1064                         goto finish;
1065
1066                 r = append_bind_mounts(&m, bind_mounts, n_bind_mounts);
1067                 if (r < 0)
1068                         goto finish;
1069
1070                 if (tmp_dir) {
1071                         *(m++) = (MountEntry) {
1072                                 .path_const = "/tmp",
1073                                 .mode = PRIVATE_TMP,
1074                         };
1075                 }
1076
1077                 if (var_tmp_dir) {
1078                         *(m++) = (MountEntry) {
1079                                 .path_const = "/var/tmp",
1080                                 .mode = PRIVATE_VAR_TMP,
1081                         };
1082                 }
1083
1084                 if (ns_info->private_dev) {
1085                         *(m++) = (MountEntry) {
1086                                 .path_const = "/dev",
1087                                 .mode = PRIVATE_DEV,
1088                         };
1089                 }
1090
1091                 if (ns_info->protect_kernel_tunables) {
1092                         r = append_static_mounts(&m, protect_kernel_tunables_table, ELEMENTSOF(protect_kernel_tunables_table), ns_info->ignore_protect_paths);
1093                         if (r < 0)
1094                                 goto finish;
1095                 }
1096
1097                 if (ns_info->protect_kernel_modules) {
1098                         r = append_static_mounts(&m, protect_kernel_modules_table, ELEMENTSOF(protect_kernel_modules_table), ns_info->ignore_protect_paths);
1099                         if (r < 0)
1100                                 goto finish;
1101                 }
1102
1103                 if (ns_info->protect_control_groups) {
1104                         *(m++) = (MountEntry) {
1105                                 .path_const = "/sys/fs/cgroup",
1106                                 .mode = READONLY,
1107                         };
1108                 }
1109
1110                 r = append_protect_home(&m, protect_home, ns_info->ignore_protect_paths);
1111                 if (r < 0)
1112                         goto finish;
1113
1114                 r = append_protect_system(&m, protect_system, false);
1115                 if (r < 0)
1116                         goto finish;
1117
1118                 if (namespace_info_mount_apivfs(root, ns_info)) {
1119                         r = append_static_mounts(&m, apivfs_table, ELEMENTSOF(apivfs_table), ns_info->ignore_protect_paths);
1120                         if (r < 0)
1121                                 goto finish;
1122                 }
1123
1124                 assert(mounts + n_mounts == m);
1125
1126                 /* Prepend the root directory where that's necessary */
1127                 r = prefix_where_needed(mounts, n_mounts, root);
1128                 if (r < 0)
1129                         goto finish;
1130
1131                 qsort(mounts, n_mounts, sizeof(MountEntry), mount_path_compare);
1132
1133                 drop_duplicates(mounts, &n_mounts);
1134                 drop_outside_root(root, mounts, &n_mounts);
1135                 drop_inaccessible(mounts, &n_mounts);
1136                 drop_nop(mounts, &n_mounts);
1137         }
1138
1139         if (unshare(CLONE_NEWNS) < 0) {
1140                 r = -errno;
1141                 goto finish;
1142         }
1143
1144         if (make_slave) {
1145                 /* Remount / as SLAVE so that nothing now mounted in the namespace
1146                    shows up in the parent */
1147                 if (mount(NULL, "/", NULL, MS_SLAVE|MS_REC, NULL) < 0) {
1148                         r = -errno;
1149                         goto finish;
1150                 }
1151         }
1152
1153         /* Try to set up the new root directory before mounting anything there */
1154         if (root)
1155                 (void) base_filesystem_create(root, UID_INVALID, GID_INVALID);
1156
1157         if (root_image) {
1158                 /* A root image is specified, mount it to the right place */
1159                 r = dissected_image_mount(dissected_image, root, dissect_image_flags);
1160                 if (r < 0)
1161                         goto finish;
1162
1163                 if (decrypted_image) {
1164                         r = decrypted_image_relinquish(decrypted_image);
1165                         if (r < 0)
1166                                 goto finish;
1167                 }
1168
1169                 loop_device_relinquish(loop_device);
1170
1171         } else if (root_directory) {
1172
1173                 /* A root directory is specified. Turn its directory into bind mount, if it isn't one yet. */
1174                 r = path_is_mount_point(root, NULL, AT_SYMLINK_FOLLOW);
1175                 if (r < 0)
1176                         goto finish;
1177                 if (r == 0) {
1178                         if (mount(root, root, NULL, MS_BIND|MS_REC, NULL) < 0) {
1179                                 r = -errno;
1180                                 goto finish;
1181                         }
1182                 }
1183
1184         } else if (root) {
1185
1186                 /* Let's mount the main root directory to the root directory to use */
1187                 if (mount("/", root, NULL, MS_BIND|MS_REC, NULL) < 0) {
1188                         r = -errno;
1189                         goto finish;
1190                 }
1191         }
1192
1193         if (n_mounts > 0) {
1194                 _cleanup_fclose_ FILE *proc_self_mountinfo = NULL;
1195                 char **blacklist;
1196                 unsigned j;
1197
1198                 /* Open /proc/self/mountinfo now as it may become unavailable if we mount anything on top of /proc.
1199                  * For example, this is the case with the option: 'InaccessiblePaths=/proc' */
1200                 proc_self_mountinfo = fopen("/proc/self/mountinfo", "re");
1201                 if (!proc_self_mountinfo) {
1202                         r = -errno;
1203                         goto finish;
1204                 }
1205
1206                 /* First round, add in all special mounts we need */
1207                 for (m = mounts; m < mounts + n_mounts; ++m) {
1208                         r = apply_mount(root, m, tmp_dir, var_tmp_dir);
1209                         if (r < 0)
1210                                 goto finish;
1211                 }
1212
1213                 /* Create a blacklist we can pass to bind_mount_recursive() */
1214                 blacklist = newa(char*, n_mounts+1);
1215                 for (j = 0; j < n_mounts; j++)
1216                         blacklist[j] = (char*) mount_entry_path(mounts+j);
1217                 blacklist[j] = NULL;
1218
1219                 /* Second round, flip the ro bits if necessary. */
1220                 for (m = mounts; m < mounts + n_mounts; ++m) {
1221                         r = make_read_only(m, blacklist, proc_self_mountinfo);
1222                         if (r < 0)
1223                                 goto finish;
1224                 }
1225         }
1226
1227         if (root) {
1228                 /* MS_MOVE does not work on MS_SHARED so the remount MS_SHARED will be done later */
1229                 r = mount_move_root(root);
1230                 if (r < 0)
1231                         goto finish;
1232         }
1233
1234         /* Remount / as the desired mode. Not that this will not
1235          * reestablish propagation from our side to the host, since
1236          * what's disconnected is disconnected. */
1237         if (mount(NULL, "/", NULL, mount_flags | MS_REC, NULL) < 0) {
1238                 r = -errno;
1239                 goto finish;
1240         }
1241
1242         r = 0;
1243
1244 finish:
1245         for (m = mounts; m < mounts + n_mounts; m++)
1246                 mount_entry_done(m);
1247
1248         return r;
1249 }
1250
1251 void bind_mount_free_many(BindMount *b, unsigned n) {
1252         unsigned i;
1253
1254         assert(b || n == 0);
1255
1256         for (i = 0; i < n; i++) {
1257                 free(b[i].source);
1258                 free(b[i].destination);
1259         }
1260
1261         free(b);
1262 }
1263
1264 int bind_mount_add(BindMount **b, unsigned *n, const BindMount *item) {
1265         _cleanup_free_ char *s = NULL, *d = NULL;
1266         BindMount *c;
1267
1268         assert(b);
1269         assert(n);
1270         assert(item);
1271
1272         s = strdup(item->source);
1273         if (!s)
1274                 return -ENOMEM;
1275
1276         d = strdup(item->destination);
1277         if (!d)
1278                 return -ENOMEM;
1279
1280         c = realloc_multiply(*b, sizeof(BindMount), *n + 1);
1281         if (!c)
1282                 return -ENOMEM;
1283
1284         *b = c;
1285
1286         c[(*n) ++] = (BindMount) {
1287                 .source = s,
1288                 .destination = d,
1289                 .read_only = item->read_only,
1290                 .recursive = item->recursive,
1291                 .ignore_enoent = item->ignore_enoent,
1292         };
1293
1294         s = d = NULL;
1295         return 0;
1296 }
1297
1298 static int setup_one_tmp_dir(const char *id, const char *prefix, char **path) {
1299         _cleanup_free_ char *x = NULL;
1300         char bid[SD_ID128_STRING_MAX];
1301         sd_id128_t boot_id;
1302         int r;
1303
1304         assert(id);
1305         assert(prefix);
1306         assert(path);
1307
1308         /* We include the boot id in the directory so that after a
1309          * reboot we can easily identify obsolete directories. */
1310
1311         r = sd_id128_get_boot(&boot_id);
1312         if (r < 0)
1313                 return r;
1314
1315         x = strjoin(prefix, "/systemd-private-", sd_id128_to_string(boot_id, bid), "-", id, "-XXXXXX");
1316         if (!x)
1317                 return -ENOMEM;
1318
1319         RUN_WITH_UMASK(0077)
1320                 if (!mkdtemp(x))
1321                         return -errno;
1322
1323         RUN_WITH_UMASK(0000) {
1324                 char *y;
1325
1326                 y = strjoina(x, "/tmp");
1327
1328                 if (mkdir(y, 0777 | S_ISVTX) < 0)
1329                         return -errno;
1330         }
1331
1332         *path = x;
1333         x = NULL;
1334
1335         return 0;
1336 }
1337
1338 int setup_tmp_dirs(const char *id, char **tmp_dir, char **var_tmp_dir) {
1339         char *a, *b;
1340         int r;
1341
1342         assert(id);
1343         assert(tmp_dir);
1344         assert(var_tmp_dir);
1345
1346         r = setup_one_tmp_dir(id, "/tmp", &a);
1347         if (r < 0)
1348                 return r;
1349
1350         r = setup_one_tmp_dir(id, "/var/tmp", &b);
1351         if (r < 0) {
1352                 char *t;
1353
1354                 t = strjoina(a, "/tmp");
1355                 rmdir(t);
1356                 rmdir(a);
1357
1358                 free(a);
1359                 return r;
1360         }
1361
1362         *tmp_dir = a;
1363         *var_tmp_dir = b;
1364
1365         return 0;
1366 }
1367
1368 int setup_netns(int netns_storage_socket[2]) {
1369         _cleanup_close_ int netns = -1;
1370         int r, q;
1371
1372         assert(netns_storage_socket);
1373         assert(netns_storage_socket[0] >= 0);
1374         assert(netns_storage_socket[1] >= 0);
1375
1376         /* We use the passed socketpair as a storage buffer for our
1377          * namespace reference fd. Whatever process runs this first
1378          * shall create a new namespace, all others should just join
1379          * it. To serialize that we use a file lock on the socket
1380          * pair.
1381          *
1382          * It's a bit crazy, but hey, works great! */
1383
1384         if (lockf(netns_storage_socket[0], F_LOCK, 0) < 0)
1385                 return -errno;
1386
1387         netns = receive_one_fd(netns_storage_socket[0], MSG_DONTWAIT);
1388         if (netns == -EAGAIN) {
1389                 /* Nothing stored yet, so let's create a new namespace */
1390
1391                 if (unshare(CLONE_NEWNET) < 0) {
1392                         r = -errno;
1393                         goto fail;
1394                 }
1395
1396                 loopback_setup();
1397
1398                 netns = open("/proc/self/ns/net", O_RDONLY|O_CLOEXEC|O_NOCTTY);
1399                 if (netns < 0) {
1400                         r = -errno;
1401                         goto fail;
1402                 }
1403
1404                 r = 1;
1405
1406         } else if (netns < 0) {
1407                 r = netns;
1408                 goto fail;
1409
1410         } else {
1411                 /* Yay, found something, so let's join the namespace */
1412                 if (setns(netns, CLONE_NEWNET) < 0) {
1413                         r = -errno;
1414                         goto fail;
1415                 }
1416
1417                 r = 0;
1418         }
1419
1420         q = send_one_fd(netns_storage_socket[1], netns, MSG_DONTWAIT);
1421         if (q < 0) {
1422                 r = q;
1423                 goto fail;
1424         }
1425
1426 fail:
1427         (void) lockf(netns_storage_socket[0], F_ULOCK, 0);
1428         return r;
1429 }
1430
1431 static const char *const protect_home_table[_PROTECT_HOME_MAX] = {
1432         [PROTECT_HOME_NO] = "no",
1433         [PROTECT_HOME_YES] = "yes",
1434         [PROTECT_HOME_READ_ONLY] = "read-only",
1435 };
1436
1437 DEFINE_STRING_TABLE_LOOKUP(protect_home, ProtectHome);
1438
1439 static const char *const protect_system_table[_PROTECT_SYSTEM_MAX] = {
1440         [PROTECT_SYSTEM_NO] = "no",
1441         [PROTECT_SYSTEM_YES] = "yes",
1442         [PROTECT_SYSTEM_FULL] = "full",
1443         [PROTECT_SYSTEM_STRICT] = "strict",
1444 };
1445
1446 DEFINE_STRING_TABLE_LOOKUP(protect_system, ProtectSystem);