src/mount-setup.c

   1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
   2
   3 /***
   4   This file is part of systemd.
   5
   6   Copyright 2010 Lennart Poettering
   7
   8   systemd is free software; you can redistribute it and/or modify it
   9   under the terms of the GNU General Public License as published by
  10   the Free Software Foundation; either version 2 of the License, or
  11   (at your option) any later version.
  12
  13   systemd is distributed in the hope that it will be useful, but
  14   WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16   General Public License for more details.
  17
  18   You should have received a copy of the GNU General Public License
  19   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  20 ***/
  21
  22 #include <sys/mount.h>
  23 #include <errno.h>
  24 #include <sys/stat.h>
  25 #include <stdlib.h>
  26 #include <string.h>
  27 #include <libgen.h>
  28 #include <assert.h>
  29 #include <unistd.h>
  30 #include <ftw.h>
  31
  32 #include "mount-setup.h"
  33 #include "log.h"
  34 #include "macro.h"
  35 #include "util.h"
  36 #include "label.h"
  37
  38 #ifndef TTY_GID
  39 #define TTY_GID 5
  40 #endif
  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 fatal;
  49 } MountPoint;
  50
  51 static const MountPoint mount_table[] = {
  52         { "proc",     "/proc",                  "proc",     NULL,                MS_NOSUID|MS_NOEXEC|MS_NODEV, true },
  53         { "sysfs",    "/sys",                   "sysfs",    NULL,                MS_NOSUID|MS_NOEXEC|MS_NODEV, true },
  54         { "devtmpfs", "/dev",                   "devtmpfs", "mode=755",          MS_NOSUID,                    true },
  55         { "tmpfs",    "/dev/shm",               "tmpfs",    "mode=1777",         MS_NOSUID|MS_NODEV,           true },
  56         { "devpts",   "/dev/pts",               "devpts",   "mode=620,gid=" STRINGIFY(TTY_GID), MS_NOSUID|MS_NOEXEC, false },
  57         { "tmpfs",    "/run",                   "tmpfs",    "mode=755",          MS_NOSUID|MS_NOEXEC|MS_NODEV, true },
  58         { "tmpfs",    "/sys/fs/cgroup",         "tmpfs",    "mode=755",          MS_NOSUID|MS_NOEXEC|MS_NODEV, false },
  59         { "cgroup",   "/sys/fs/cgroup/systemd", "cgroup",   "none,name=systemd", MS_NOSUID|MS_NOEXEC|MS_NODEV, false },
  60 };
  61
  62 /* These are API file systems that might be mounted by other software,
  63  * we just list them here so that we know that we should ignore them */
  64
  65 static const char * const ignore_paths[] = {
  66         "/selinux",
  67         "/proc/bus/usb",
  68         "/var/lib/nfs/rpc_pipefs",
  69         "/proc/fs/nfsd"
  70 };
  71
  72 bool mount_point_is_api(const char *path) {
  73         unsigned i;
  74
  75         /* Checks if this mount point is considered "API", and hence
  76          * should be ignored */
  77
  78         for (i = 0; i < ELEMENTSOF(mount_table); i ++)
  79                 if (path_equal(path, mount_table[i].where))
  80                         return true;
  81
  82         return path_startswith(path, "/sys/fs/cgroup/");
  83 }
  84
  85 bool mount_point_ignore(const char *path) {
  86         unsigned i;
  87
  88         for (i = 0; i < ELEMENTSOF(ignore_paths); i++)
  89                 if (path_equal(path, ignore_paths[i]))
  90                         return true;
  91
  92         return false;
  93 }
  94
  95 static int mount_one(const MountPoint *p) {
  96         int r;
  97
  98         assert(p);
  99
 100         /* Relabel first, just in case */
 101         label_fix(p->where, true);
 102
 103         if ((r = path_is_mount_point(p->where)) < 0)
 104                 return r;
 105
 106         if (r > 0)
 107                 return 0;
 108
 109         /* The access mode here doesn't really matter too much, since
 110          * the mounted file system will take precedence anyway. */
 111         mkdir_p(p->where, 0755);
 112
 113         log_debug("Mounting %s to %s of type %s with options %s.",
 114                   p->what,
 115                   p->where,
 116                   p->type,
 117                   strna(p->options));
 118
 119         if (mount(p->what,
 120                   p->where,
 121                   p->type,
 122                   p->flags,
 123                   p->options) < 0) {
 124                 log_error("Failed to mount %s: %s", p->where, strerror(errno));
 125                 return p->fatal ? -errno : 0;
 126         }
 127
 128         /* Relabel again, since we now mounted something fresh here */
 129         label_fix(p->where, false);
 130
 131         return 0;
 132 }
 133
 134 static int mount_cgroup_controllers(void) {
 135         int r;
 136         FILE *f;
 137         char buf[LINE_MAX];
 138
 139         /* Mount all available cgroup controllers that are built into the kernel. */
 140
 141         if (!(f = fopen("/proc/cgroups", "re")))
 142                 return -ENOENT;
 143
 144         /* Ignore the header line */
 145         (void) fgets(buf, sizeof(buf), f);
 146
 147         for (;;) {
 148                 MountPoint p;
 149                 char *controller, *where;
 150                 int enabled = false;
 151
 152                 if (fscanf(f, "%ms %*i %*i %i", &controller, &enabled) != 2) {
 153
 154                         if (feof(f))
 155                                 break;
 156
 157                         log_error("Failed to parse /proc/cgroups.");
 158                         r = -EIO;
 159                         goto finish;
 160                 }
 161
 162                 if (!enabled) {
 163                         free(controller);
 164                         continue;
 165                 }
 166
 167                 if (asprintf(&where, "/sys/fs/cgroup/%s", controller) < 0) {
 168                         free(controller);
 169                         r = -ENOMEM;
 170                         goto finish;
 171                 }
 172
 173                 zero(p);
 174                 p.what = "cgroup";
 175                 p.where = where;
 176                 p.type = "cgroup";
 177                 p.options = controller;
 178                 p.flags = MS_NOSUID|MS_NOEXEC|MS_NODEV;
 179                 p.fatal = false;
 180
 181                 r = mount_one(&p);
 182                 free(controller);
 183                 free(where);
 184
 185                 if (r < 0)
 186                         goto finish;
 187         }
 188
 189         r = 0;
 190
 191 finish:
 192         fclose(f);
 193
 194         return r;
 195 }
 196
 197 static int symlink_and_label(const char *old_path, const char *new_path) {
 198         int r;
 199
 200         assert(old_path);
 201         assert(new_path);
 202
 203         if ((r = label_symlinkfile_set(new_path)) < 0)
 204                 return r;
 205
 206         if (symlink(old_path, new_path) < 0)
 207                 r = -errno;
 208
 209         label_file_clear();
 210
 211         return r;
 212 }
 213
 214 static int nftw_cb(
 215                 const char *fpath,
 216                 const struct stat *sb,
 217                 int tflag,
 218                 struct FTW *ftwbuf) {
 219
 220         /* No need to label /dev twice in a row... */
 221         if (ftwbuf->level == 0)
 222                 return 0;
 223
 224         label_fix(fpath, true);
 225         return 0;
 226 };
 227
 228 int mount_setup(void) {
 229
 230         const char symlinks[] =
 231                 "/proc/kcore\0"      "/dev/core\0"
 232                 "/proc/self/fd\0"    "/dev/fd\0"
 233                 "/proc/self/fd/0\0"  "/dev/stdin\0"
 234                 "/proc/self/fd/1\0"  "/dev/stdout\0"
 235                 "/proc/self/fd/2\0"  "/dev/stderr\0";
 236
 237         int r;
 238         unsigned i;
 239         const char *j, *k;
 240
 241         for (i = 0; i < ELEMENTSOF(mount_table); i ++)
 242                 if ((r = mount_one(mount_table+i)) < 0)
 243                         return r;
 244
 245         /* Nodes in devtmpfs and /run need to be manually updated for
 246          * the appropriate labels, after mounting. The other virtual
 247          * API file systems like /sys and /proc do not need that, they
 248          * use the same label for all their files. */
 249         if (unlink("/dev/.systemd-relabel-run-dev") >= 0) {
 250                 nftw("/dev", nftw_cb, 64, FTW_MOUNT|FTW_PHYS);
 251                 nftw("/run", nftw_cb, 64, FTW_MOUNT|FTW_PHYS);
 252         }
 253
 254         /* Create a few default symlinks, which are normally created
 255          * by udevd, but some scripts might need them before we start
 256          * udevd. */
 257         NULSTR_FOREACH_PAIR(j, k, symlinks)
 258                 symlink_and_label(j, k);
 259
 260         /* Create a few directories we always want around */
 261         mkdir("/run/systemd", 0755);
 262
 263         return mount_cgroup_controllers();
 264 }