src/udev/udev-node.c

   1 /*
   2  * Copyright (C) 2003-2013 Kay Sievers <kay@vrfy.org>
   3  *
   4  * This program is free software: you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation, either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  16  */
  17
  18 #include <string.h>
  19 #include <stdio.h>
  20 #include <stddef.h>
  21 #include <stdbool.h>
  22 #include <fcntl.h>
  23 #include <unistd.h>
  24 #include <errno.h>
  25 #include <dirent.h>
  26 #include <sys/stat.h>
  27
  28 #include "udev.h"
  29 #include "smack-util.h"
  30 #include "selinux-util.h"
  31 #include "formats-util.h"
  32
  33 static int node_symlink(struct udev_device *dev, const char *node, const char *slink) {
  34         struct stat stats;
  35         char target[UTIL_PATH_SIZE];
  36         char *s;
  37         size_t l;
  38         char slink_tmp[UTIL_PATH_SIZE + 32];
  39         int i = 0;
  40         int tail = 0;
  41         int err = 0;
  42
  43         /* use relative link */
  44         target[0] = '\0';
  45         while (node[i] && (node[i] == slink[i])) {
  46                 if (node[i] == '/')
  47                         tail = i+1;
  48                 i++;
  49         }
  50         s = target;
  51         l = sizeof(target);
  52         while (slink[i] != '\0') {
  53                 if (slink[i] == '/')
  54                         l = strpcpy(&s, l, "../");
  55                 i++;
  56         }
  57         l = strscpy(s, l, &node[tail]);
  58         if (l == 0) {
  59                 err = -EINVAL;
  60                 goto exit;
  61         }
  62
  63         /* preserve link with correct target, do not replace node of other device */
  64         if (lstat(slink, &stats) == 0) {
  65                 if (S_ISBLK(stats.st_mode) || S_ISCHR(stats.st_mode)) {
  66                         log_error("conflicting device node '%s' found, link to '%s' will not be created", slink, node);
  67                         goto exit;
  68                 } else if (S_ISLNK(stats.st_mode)) {
  69                         char buf[UTIL_PATH_SIZE];
  70                         int len;
  71
  72                         len = readlink(slink, buf, sizeof(buf));
  73                         if (len > 0 && len < (int)sizeof(buf)) {
  74                                 buf[len] = '\0';
  75                                 if (streq(target, buf)) {
  76                                         log_debug("preserve already existing symlink '%s' to '%s'", slink, target);
  77                                         label_fix(slink, true, false);
  78                                         utimensat(AT_FDCWD, slink, NULL, AT_SYMLINK_NOFOLLOW);
  79                                         goto exit;
  80                                 }
  81                         }
  82                 }
  83         } else {
  84                 log_debug("creating symlink '%s' to '%s'", slink, target);
  85                 do {
  86                         err = mkdir_parents_label(slink, 0755);
  87                         if (err != 0 && err != -ENOENT)
  88                                 break;
  89                         mac_selinux_create_file_prepare(slink, S_IFLNK);
  90                         err = symlink(target, slink);
  91                         if (err != 0)
  92                                 err = -errno;
  93                         mac_selinux_create_file_clear();
  94                 } while (err == -ENOENT);
  95                 if (err == 0)
  96                         goto exit;
  97         }
  98
  99         log_debug("atomically replace '%s'", slink);
 100         strscpyl(slink_tmp, sizeof(slink_tmp), slink, ".tmp-", udev_device_get_id_filename(dev), NULL);
 101         unlink(slink_tmp);
 102         do {
 103                 err = mkdir_parents_label(slink_tmp, 0755);
 104                 if (err != 0 && err != -ENOENT)
 105                         break;
 106                 mac_selinux_create_file_prepare(slink_tmp, S_IFLNK);
 107                 err = symlink(target, slink_tmp);
 108                 if (err != 0)
 109                         err = -errno;
 110                 mac_selinux_create_file_clear();
 111         } while (err == -ENOENT);
 112         if (err != 0) {
 113                 log_error_errno(errno, "symlink '%s' '%s' failed: %m", target, slink_tmp);
 114                 goto exit;
 115         }
 116         err = rename(slink_tmp, slink);
 117         if (err != 0) {
 118                 log_error_errno(errno, "rename '%s' '%s' failed: %m", slink_tmp, slink);
 119                 unlink(slink_tmp);
 120         }
 121 exit:
 122         return err;
 123 }
 124
 125 /* find device node of device with highest priority */
 126 static const char *link_find_prioritized(struct udev_device *dev, bool add, const char *stackdir, char *buf, size_t bufsize) {
 127         struct udev *udev = udev_device_get_udev(dev);
 128         DIR *dir;
 129         int priority = 0;
 130         const char *target = NULL;
 131
 132         if (add) {
 133                 priority = udev_device_get_devlink_priority(dev);
 134                 strscpy(buf, bufsize, udev_device_get_devnode(dev));
 135                 target = buf;
 136         }
 137
 138         dir = opendir(stackdir);
 139         if (dir == NULL)
 140                 return target;
 141         for (;;) {
 142                 struct udev_device *dev_db;
 143                 struct dirent *dent;
 144
 145                 dent = readdir(dir);
 146                 if (dent == NULL || dent->d_name[0] == '\0')
 147                         break;
 148                 if (dent->d_name[0] == '.')
 149                         continue;
 150
 151                 log_debug("found '%s' claiming '%s'", dent->d_name, stackdir);
 152
 153                 /* did we find ourself? */
 154                 if (streq(dent->d_name, udev_device_get_id_filename(dev)))
 155                         continue;
 156
 157                 dev_db = udev_device_new_from_device_id(udev, dent->d_name);
 158                 if (dev_db != NULL) {
 159                         const char *devnode;
 160
 161                         devnode = udev_device_get_devnode(dev_db);
 162                         if (devnode != NULL) {
 163                                 if (target == NULL || udev_device_get_devlink_priority(dev_db) > priority) {
 164                                         log_debug("'%s' claims priority %i for '%s'",
 165                                                   udev_device_get_syspath(dev_db), udev_device_get_devlink_priority(dev_db), stackdir);
 166                                         priority = udev_device_get_devlink_priority(dev_db);
 167                                         strscpy(buf, bufsize, devnode);
 168                                         target = buf;
 169                                 }
 170                         }
 171                         udev_device_unref(dev_db);
 172                 }
 173         }
 174         closedir(dir);
 175         return target;
 176 }
 177
 178 /* manage "stack of names" with possibly specified device priorities */
 179 static void link_update(struct udev_device *dev, const char *slink, bool add) {
 180         char name_enc[UTIL_PATH_SIZE];
 181         char filename[UTIL_PATH_SIZE * 2];
 182         char dirname[UTIL_PATH_SIZE];
 183         const char *target;
 184         char buf[UTIL_PATH_SIZE];
 185
 186         util_path_encode(slink + strlen("/dev"), name_enc, sizeof(name_enc));
 187         strscpyl(dirname, sizeof(dirname), "/run/udev/links/", name_enc, NULL);
 188         strscpyl(filename, sizeof(filename), dirname, "/", udev_device_get_id_filename(dev), NULL);
 189
 190         if (!add && unlink(filename) == 0)
 191                 rmdir(dirname);
 192
 193         target = link_find_prioritized(dev, add, dirname, buf, sizeof(buf));
 194         if (target == NULL) {
 195                 log_debug("no reference left, remove '%s'", slink);
 196                 if (unlink(slink) == 0)
 197                         rmdir_parents(slink, "/");
 198         } else {
 199                 log_debug("creating link '%s' to '%s'", slink, target);
 200                 node_symlink(dev, target, slink);
 201         }
 202
 203         if (add) {
 204                 int err;
 205
 206                 do {
 207                         int fd;
 208
 209                         err = mkdir_parents(filename, 0755);
 210                         if (err != 0 && err != -ENOENT)
 211                                 break;
 212                         fd = open(filename, O_WRONLY|O_CREAT|O_CLOEXEC|O_TRUNC|O_NOFOLLOW, 0444);
 213                         if (fd >= 0)
 214                                 close(fd);
 215                         else
 216                                 err = -errno;
 217                 } while (err == -ENOENT);
 218         }
 219 }
 220
 221 void udev_node_update_old_links(struct udev_device *dev, struct udev_device *dev_old) {
 222         struct udev_list_entry *list_entry;
 223
 224         /* update possible left-over symlinks */
 225         udev_list_entry_foreach(list_entry, udev_device_get_devlinks_list_entry(dev_old)) {
 226                 const char *name = udev_list_entry_get_name(list_entry);
 227                 struct udev_list_entry *list_entry_current;
 228                 int found;
 229
 230                 /* check if old link name still belongs to this device */
 231                 found = 0;
 232                 udev_list_entry_foreach(list_entry_current, udev_device_get_devlinks_list_entry(dev)) {
 233                         const char *name_current = udev_list_entry_get_name(list_entry_current);
 234
 235                         if (streq(name, name_current)) {
 236                                 found = 1;
 237                                 break;
 238                         }
 239                 }
 240                 if (found)
 241                         continue;
 242
 243                 log_debug("update old name, '%s' no longer belonging to '%s'",
 244                      name, udev_device_get_devpath(dev));
 245                 link_update(dev, name, false);
 246         }
 247 }
 248
 249 static int node_permissions_apply(struct udev_device *dev, bool apply,
 250                                   mode_t mode, uid_t uid, gid_t gid,
 251                                   struct udev_list *seclabel_list) {
 252         const char *devnode = udev_device_get_devnode(dev);
 253         dev_t devnum = udev_device_get_devnum(dev);
 254         struct stat stats;
 255         struct udev_list_entry *entry;
 256         int err = 0;
 257
 258         if (streq(udev_device_get_subsystem(dev), "block"))
 259                 mode |= S_IFBLK;
 260         else
 261                 mode |= S_IFCHR;
 262
 263         if (lstat(devnode, &stats) != 0) {
 264                 err = -errno;
 265                 log_debug_errno(errno, "can not stat() node '%s' (%m)", devnode);
 266                 goto out;
 267         }
 268
 269         if (((stats.st_mode & S_IFMT) != (mode & S_IFMT)) || (stats.st_rdev != devnum)) {
 270                 err = -EEXIST;
 271                 log_debug("found node '%s' with non-matching devnum %s, skip handling",
 272                           udev_device_get_devnode(dev), udev_device_get_id_filename(dev));
 273                 goto out;
 274         }
 275
 276         if (apply) {
 277                 bool selinux = false;
 278                 bool smack = false;
 279
 280                 if ((stats.st_mode & 0777) != (mode & 0777) || stats.st_uid != uid || stats.st_gid != gid) {
 281                         log_debug("set permissions %s, %#o, uid=%u, gid=%u", devnode, mode, uid, gid);
 282                         err = chmod(devnode, mode);
 283                         if (err < 0)
 284                                 log_warning_errno(errno, "setting mode of %s to %#o failed: %m", devnode, mode);
 285                         err = chown(devnode, uid, gid);
 286                         if (err < 0)
 287                                 log_warning_errno(errno, "setting owner of %s to uid=%u, gid=%u failed: %m", devnode, uid, gid);
 288                 } else {
 289                         log_debug("preserve permissions %s, %#o, uid=%u, gid=%u", devnode, mode, uid, gid);
 290                 }
 291
 292                 /* apply SECLABEL{$module}=$label */
 293                 udev_list_entry_foreach(entry, udev_list_get_entry(seclabel_list)) {
 294                         const char *name, *label;
 295                         int r;
 296
 297                         name = udev_list_entry_get_name(entry);
 298                         label = udev_list_entry_get_value(entry);
 299
 300                         if (streq(name, "selinux")) {
 301                                 selinux = true;
 302
 303                                 r = mac_selinux_apply(devnode, label);
 304                                 if (r < 0)
 305                                         log_error_errno(r, "SECLABEL: failed to set SELinux label '%s': %m", label);
 306                                 else
 307                                         log_debug("SECLABEL: set SELinux label '%s'", label);
 308
 309                         } else if (streq(name, "smack")) {
 310                                 smack = true;
 311
 312                                 r = mac_smack_apply(devnode, label);
 313                                 if (r < 0)
 314                                         log_error_errno(r, "SECLABEL: failed to set SMACK label '%s': %m", label);
 315                                 else
 316                                         log_debug("SECLABEL: set SMACK label '%s'", label);
 317
 318                         } else
 319                                 log_error("SECLABEL: unknown subsystem, ignoring '%s'='%s'", name, label);
 320                 }
 321
 322                 /* set the defaults */
 323                 if (!selinux)
 324                         mac_selinux_fix(devnode, true, false);
 325                 if (!smack)
 326                         mac_smack_apply(devnode, NULL);
 327         }
 328
 329         /* always update timestamp when we re-use the node, like on media change events */
 330         utimensat(AT_FDCWD, devnode, NULL, 0);
 331 out:
 332         return err;
 333 }
 334
 335 void udev_node_add(struct udev_device *dev, bool apply,
 336                    mode_t mode, uid_t uid, gid_t gid,
 337                    struct udev_list *seclabel_list) {
 338         char filename[UTIL_PATH_SIZE];
 339         struct udev_list_entry *list_entry;
 340
 341         log_debug("handling device node '%s', devnum=%s, mode=%#o, uid="UID_FMT", gid="GID_FMT,
 342                   udev_device_get_devnode(dev), udev_device_get_id_filename(dev), mode, uid, gid);
 343
 344         if (node_permissions_apply(dev, apply, mode, uid, gid, seclabel_list) < 0)
 345                 return;
 346
 347         /* always add /dev/{block,char}/$major:$minor */
 348         snprintf(filename, sizeof(filename), "/dev/%s/%u:%u",
 349                  streq(udev_device_get_subsystem(dev), "block") ? "block" : "char",
 350                  major(udev_device_get_devnum(dev)), minor(udev_device_get_devnum(dev)));
 351         node_symlink(dev, udev_device_get_devnode(dev), filename);
 352
 353         /* create/update symlinks, add symlinks to name index */
 354         udev_list_entry_foreach(list_entry, udev_device_get_devlinks_list_entry(dev))
 355                         link_update(dev, udev_list_entry_get_name(list_entry), true);
 356 }
 357
 358 void udev_node_remove(struct udev_device *dev) {
 359         struct udev_list_entry *list_entry;
 360         char filename[UTIL_PATH_SIZE];
 361
 362         /* remove/update symlinks, remove symlinks from name index */
 363         udev_list_entry_foreach(list_entry, udev_device_get_devlinks_list_entry(dev))
 364                 link_update(dev, udev_list_entry_get_name(list_entry), false);
 365
 366         /* remove /dev/{block,char}/$major:$minor */
 367         snprintf(filename, sizeof(filename), "/dev/%s/%u:%u",
 368                  streq(udev_device_get_subsystem(dev), "block") ? "block" : "char",
 369                  major(udev_device_get_devnum(dev)), minor(udev_device_get_devnum(dev)));
 370         unlink(filename);
 371 }