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 typedef struct MountPoint {
  39         const char *what;
  40         const char *where;
  41         const char *type;
  42         const char *options;
  43         unsigned long flags;
  44         bool fatal;
  45 } MountPoint;
  46
  47 static const MountPoint mount_table[] = {
  48         { "proc",     "/proc",                  "proc",     NULL,                MS_NOSUID|MS_NOEXEC|MS_NODEV, true },
  49         { "sysfs",    "/sys",                   "sysfs",    NULL,                MS_NOSUID|MS_NOEXEC|MS_NODEV, true },
  50         { "devtmpfs", "/dev",                   "devtmpfs", "mode=755",          MS_NOSUID,                    true },
  51         { "tmpfs",    "/dev/shm",               "tmpfs",    "mode=1777",         MS_NOSUID|MS_NODEV,           true },
  52         { "devpts",   "/dev/pts",               "devpts",   NULL,                MS_NOSUID|MS_NOEXEC,          false },
  53         { "tmpfs",    "/sys/fs/cgroup",         "tmpfs",    "mode=755",          MS_NOSUID|MS_NOEXEC|MS_NODEV, true },
  54         { "cgroup",   "/sys/fs/cgroup/systemd", "cgroup",   "none,name=systemd", MS_NOSUID|MS_NOEXEC|MS_NODEV, true },
  55 };
  56
  57 /* These are API file systems that might be mounted by other software,
  58  * we just list them here so that we know that we should ignore them */
  59
  60 static const char * const ignore_paths[] = {
  61         "/selinux",
  62         "/proc/bus/usb",
  63         "/var/lib/nfs/rpc_pipefs",
  64         "/proc/fs/nfsd"
  65 };
  66
  67 bool mount_point_is_api(const char *path) {
  68         unsigned i;
  69
  70         /* Checks if this mount point is considered "API", and hence
  71          * should be ignored */
  72
  73         for (i = 0; i < ELEMENTSOF(mount_table); i ++)
  74                 if (path_equal(path, mount_table[i].where))
  75                         return true;
  76
  77         return path_startswith(path, "/sys/fs/cgroup/");
  78 }
  79
  80 bool mount_point_ignore(const char *path) {
  81         unsigned i;
  82
  83         for (i = 0; i < ELEMENTSOF(ignore_paths); i++)
  84                 if (path_equal(path, ignore_paths[i]))
  85                         return true;
  86
  87         return false;
  88 }
  89
  90 static int mount_one(const MountPoint *p) {
  91         int r;
  92
  93         assert(p);
  94
  95         if ((r = path_is_mount_point(p->where)) < 0)
  96                 return r;
  97
  98         if (r > 0)
  99                 return 0;
 100
 101         /* The access mode here doesn't really matter too much, since
 102          * the mounted file system will take precedence anyway. */
 103         mkdir_p(p->where, 0755);
 104
 105         log_debug("Mounting %s to %s of type %s with options %s.",
 106                   p->what,
 107                   p->where,
 108                   p->type,
 109                   strna(p->options));
 110
 111         if (mount(p->what,
 112                   p->where,
 113                   p->type,
 114                   p->flags,
 115                   p->options) < 0) {
 116                 log_error("Failed to mount %s: %s", p->where, strerror(errno));
 117                 return p->fatal ? -errno : 0;
 118         }
 119
 120         label_fix(p->where);
 121
 122         return 0;
 123 }
 124
 125 static int mount_cgroup_controllers(void) {
 126         int r;
 127         FILE *f;
 128         char buf [256];
 129
 130         /* Mount all available cgroup controllers that are built into the kernel. */
 131
 132         if (!(f = fopen("/proc/cgroups", "re")))
 133                 return -ENOENT;
 134
 135         /* Ignore the header line */
 136         (void) fgets(buf, sizeof(buf), f);
 137
 138         for (;;) {
 139                 MountPoint p;
 140                 char *controller, *where;
 141                 int enabled = false;
 142
 143                 if (fscanf(f, "%ms %*i %*i %i", &controller, &enabled) != 2) {
 144
 145                         if (feof(f))
 146                                 break;
 147
 148                         log_error("Failed to parse /proc/cgroups.");
 149                         r = -EIO;
 150                         goto finish;
 151                 }
 152
 153                 if (!enabled) {
 154                         free(controller);
 155                         continue;
 156                 }
 157
 158                 if (asprintf(&where, "/sys/fs/cgroup/%s", controller) < 0) {
 159                         free(controller);
 160                         r = -ENOMEM;
 161                         goto finish;
 162                 }
 163
 164                 zero(p);
 165                 p.what = "cgroup";
 166                 p.where = where;
 167                 p.type = "cgroup";
 168                 p.options = controller;
 169                 p.flags = MS_NOSUID|MS_NOEXEC|MS_NODEV;
 170                 p.fatal = false;
 171
 172                 r = mount_one(&p);
 173                 free(controller);
 174                 free(where);
 175
 176                 if (r < 0)
 177                         goto finish;
 178         }
 179
 180         r = 0;
 181
 182 finish:
 183         fclose(f);
 184
 185         return r;
 186 }
 187
 188 static int symlink_and_label(const char *old_path, const char *new_path) {
 189         int r;
 190
 191         assert(old_path);
 192         assert(new_path);
 193
 194         if ((r = label_symlinkfile_set(new_path)) < 0)
 195                 return r;
 196
 197         if (symlink(old_path, new_path) < 0)
 198                 r = -errno;
 199
 200         label_file_clear();
 201
 202         return r;
 203 }
 204
 205 static int nftw_cb(
 206                 const char *fpath,
 207                 const struct stat *sb,
 208                 int tflag,
 209                 struct FTW *ftwbuf) {
 210
 211         /* No need to label /dev twice in a row... */
 212         if (ftwbuf->level == 0)
 213                 return 0;
 214
 215         label_fix(fpath);
 216         return 0;
 217 };
 218
 219 int mount_setup(void) {
 220
 221         const char symlinks[] =
 222                 "/proc/kcore\0"      "/dev/core\0"
 223                 "/proc/self/fd\0"    "/dev/fd\0"
 224                 "/proc/self/fd/0\0"  "/dev/stdin\0"
 225                 "/proc/self/fd/1\0"  "/dev/stdout\0"
 226                 "/proc/self/fd/2\0"  "/dev/stderr\0"
 227                 "\0";
 228
 229         int r;
 230         unsigned i;
 231         const char *j, *k;
 232
 233         for (i = 0; i < ELEMENTSOF(mount_table); i ++)
 234                 if ((r = mount_one(mount_table+i)) < 0)
 235                         return r;
 236
 237         /* Nodes in devtmpfs need to be manually updated for the
 238          * appropriate labels, after mounting. The other virtual API
 239          * file systems do not need. */
 240
 241         if (unlink("/dev/.systemd/relabel-devtmpfs") >= 0)
 242                 nftw("/dev", nftw_cb, 64, FTW_MOUNT|FTW_PHYS);
 243
 244         /* Create a few default symlinks, which are normally created
 245          * bei udevd, but some scripts might need them before we start
 246          * udevd. */
 247
 248         NULSTR_FOREACH_PAIR(j, k, symlinks)
 249                 symlink_and_label(j, k);
 250
 251         return mount_cgroup_controllers();
 252 }