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 <stdlib.h>
  19 #include <string.h>
  20 #include <stdio.h>
  21 #include <stddef.h>
  22 #include <stdbool.h>
  23 #include <fcntl.h>
  24 #include <unistd.h>
  25 #include <errno.h>
  26 #include <grp.h>
  27 #include <dirent.h>
  28 #include <sys/time.h>
  29 #include <sys/stat.h>
  30 #include <sys/types.h>
  31
  32 #include "udev.h"
  33 #include "smack-util.h"
  34 #include "selinux-util.h"
  35
  36 static int node_symlink(struct udev_device *dev, const char *node, const char *slink) {
  37         struct stat stats;
  38         char target[UTIL_PATH_SIZE];
  39         char *s;
  40         size_t l;
  41         char slink_tmp[UTIL_PATH_SIZE + 32];
  42         int i = 0;
  43         int tail = 0;
  44         int err = 0;
  45
  46         /* use relative link */
  47         target[0] = '\0';
  48         while (node[i] && (node[i] == slink[i])) {
  49                 if (node[i] == '/')
  50                         tail = i+1;
  51                 i++;
  52         }
  53         s = target;
  54         l = sizeof(target);
  55         while (slink[i] != '\0') {
  56                 if (slink[i] == '/')
  57                         l = strpcpy(&s, l, "../");
  58                 i++;
  59         }
  60         l = strscpy(s, l, &node[tail]);
  61         if (l == 0) {
  62                 err = -EINVAL;
  63                 goto exit;
  64         }
  65
  66         /* preserve link with correct target, do not replace node of other device */
  67         if (lstat(slink, &stats) == 0) {
  68                 if (S_ISBLK(stats.st_mode) || S_ISCHR(stats.st_mode)) {
  69                         log_error("conflicting device node '%s' found, link to '%s' will not be created", slink, node);
  70                         goto exit;
  71                 } else if (S_ISLNK(stats.st_mode)) {
  72                         char buf[UTIL_PATH_SIZE];
  73                         int len;
  74
  75                         len = readlink(slink, buf, sizeof(buf));
  76                         if (len > 0 && len < (int)sizeof(buf)) {
  77                                 buf[len] = '\0';
  78                                 if (streq(target, buf)) {
  79                                         log_debug("preserve already existing symlink '%s' to '%s'", slink, target);
  80                                         label_fix(slink, true, false);
  81                                         utimensat(AT_FDCWD, slink, NULL, AT_SYMLINK_NOFOLLOW);
  82                                         goto exit;
  83                                 }
  84                         }
  85                 }
  86         } else {
  87                 log_debug("creating symlink '%s' to '%s'", slink, target);
  88                 do {
  89                         err = mkdir_parents_label(slink, 0755);
  90                         if (err != 0 && err != -ENOENT)
  91                                 break;
  92                         mac_selinux_create_file_prepare(slink, S_IFLNK);
  93                         err = symlink(target, slink);
  94                         if (err != 0)
  95                                 err = -errno;
  96                         mac_selinux_create_file_clear();
  97                 } while (err == -ENOENT);
  98                 if (err == 0)
  99                         goto exit;
 100         }
 101
 102         log_debug("atomically replace '%s'", slink);
 103         strscpyl(slink_tmp, sizeof(slink_tmp), slink, ".tmp-", udev_device_get_id_filename(dev), NULL);
 104         unlink(slink_tmp);
 105         do {
 106                 err = mkdir_parents_label(slink_tmp, 0755);
 107                 if (err != 0 && err != -ENOENT)
 108                         break;
 109                 mac_selinux_create_file_prepare(slink_tmp, S_IFLNK);
 110                 err = symlink(target, slink_tmp);
 111                 if (err != 0)
 112                         err = -errno;
 113                 mac_selinux_create_file_clear();
 114         } while (err == -ENOENT);
 115         if (err != 0) {
 116                 log_error_errno(errno, "symlink '%s' '%s' failed: %m", target, slink_tmp);
 117                 goto exit;
 118         }
 119         err = rename(slink_tmp, slink);
 120         if (err != 0) {
 121                 log_error_errno(errno, "rename '%s' '%s' failed: %m", slink_tmp, slink);
 122                 unlink(slink_tmp);
 123         }
 124 exit:
 125         return err;
 126 }
 127
 128 /* find device node of device with highest priority */
 129 static const char *link_find_prioritized(struct udev_device *dev, bool add, const char *stackdir, char *buf, size_t bufsize) {
 130         struct udev *udev = udev_device_get_udev(dev);
 131         DIR *dir;
 132         int priority = 0;
 133         const char *target = NULL;
 134
 135         if (add) {
 136                 priority = udev_device_get_devlink_priority(dev);
 137                 strscpy(buf, bufsize, udev_device_get_devnode(dev));
 138                 target = buf;
 139         }
 140
 141         dir = opendir(stackdir);
 142         if (dir == NULL)
 143                 return target;
 144         for (;;) {
 145                 struct udev_device *dev_db;
 146                 struct dirent *dent;
 147
 148                 dent = readdir(dir);
 149                 if (dent == NULL || dent->d_name[0] == '\0')
 150                         break;
 151                 if (dent->d_name[0] == '.')
 152                         continue;
 153
 154                 log_debug("found '%s' claiming '%s'", dent->d_name, stackdir);
 155
 156                 /* did we find ourself? */
 157                 if (streq(dent->d_name, udev_device_get_id_filename(dev)))
 158                         continue;
 159
 160                 dev_db = udev_device_new_from_device_id(udev, dent->d_name);
 161                 if (dev_db != NULL) {
 162                         const char *devnode;
 163
 164                         devnode = udev_device_get_devnode(dev_db);
 165                         if (devnode != NULL) {
 166                                 if (target == NULL || udev_device_get_devlink_priority(dev_db) > priority) {
 167                                         log_debug("'%s' claims priority %i for '%s'",
 168                                                   udev_device_get_syspath(dev_db), udev_device_get_devlink_priority(dev_db), stackdir);
 169                                         priority = udev_device_get_devlink_priority(dev_db);
 170                                         strscpy(buf, bufsize, devnode);
 171                                         target = buf;
 172                                 }
 173                         }
 174                         udev_device_unref(dev_db);
 175                 }
 176         }
 177         closedir(dir);
 178         return target;
 179 }
 180
 181 /* manage "stack of names" with possibly specified device priorities */
 182 static void link_update(struct udev_device *dev, const char *slink, bool add) {
 183         char name_enc[UTIL_PATH_SIZE];
 184         char filename[UTIL_PATH_SIZE * 2];
 185         char dirname[UTIL_PATH_SIZE];
 186         const char *target;
 187         char buf[UTIL_PATH_SIZE];
 188
 189         util_path_encode(slink + strlen("/dev"), name_enc, sizeof(name_enc));
 190         strscpyl(dirname, sizeof(dirname), "/run/udev/links/", name_enc, NULL);
 191         strscpyl(filename, sizeof(filename), dirname, "/", udev_device_get_id_filename(dev), NULL);
 192
 193         if (!add && unlink(filename) == 0)
 194                 rmdir(dirname);
 195
 196         target = link_find_prioritized(dev, add, dirname, buf, sizeof(buf));
 197         if (target == NULL) {
 198                 log_debug("no reference left, remove '%s'", slink);
 199                 if (unlink(slink) == 0)
 200                         rmdir_parents(slink, "/");
 201         } else {
 202                 log_debug("creating link '%s' to '%s'", slink, target);
 203                 node_symlink(dev, target, slink);
 204         }
 205
 206         if (add) {
 207                 int err;
 208
 209                 do {
 210                         int fd;
 211
 212                         err = mkdir_parents(filename, 0755);
 213                         if (err != 0 && err != -ENOENT)
 214                                 break;
 215                         fd = open(filename, O_WRONLY|O_CREAT|O_CLOEXEC|O_TRUNC|O_NOFOLLOW, 0444);
 216                         if (fd >= 0)
 217                                 close(fd);
 218                         else
 219                                 err = -errno;
 220                 } while (err == -ENOENT);
 221         }
 222 }
 223
 224 void udev_node_update_old_links(struct udev_device *dev, struct udev_device *dev_old) {
 225         struct udev_list_entry *list_entry;
 226
 227         /* update possible left-over symlinks */
 228         udev_list_entry_foreach(list_entry, udev_device_get_devlinks_list_entry(dev_old)) {
 229                 const char *name = udev_list_entry_get_name(list_entry);
 230                 struct udev_list_entry *list_entry_current;
 231                 int found;
 232
 233                 /* check if old link name still belongs to this device */
 234                 found = 0;
 235                 udev_list_entry_foreach(list_entry_current, udev_device_get_devlinks_list_entry(dev)) {
 236                         const char *name_current = udev_list_entry_get_name(list_entry_current);
 237
 238                         if (streq(name, name_current)) {
 239                                 found = 1;
 240                                 break;
 241                         }
 242                 }
 243                 if (found)
 244                         continue;
 245
 246                 log_debug("update old name, '%s' no longer belonging to '%s'",
 247                      name, udev_device_get_devpath(dev));
 248                 link_update(dev, name, false);
 249         }
 250 }
 251
 252 static int node_permissions_apply(struct udev_device *dev, bool apply,
 253                                   mode_t mode, uid_t uid, gid_t gid,
 254                                   struct udev_list *seclabel_list) {
 255         const char *devnode = udev_device_get_devnode(dev);
 256         dev_t devnum = udev_device_get_devnum(dev);
 257         struct stat stats;
 258         struct udev_list_entry *entry;
 259         int err = 0;
 260
 261         if (streq(udev_device_get_subsystem(dev), "block"))
 262                 mode |= S_IFBLK;
 263         else
 264                 mode |= S_IFCHR;
 265
 266         if (lstat(devnode, &stats) != 0) {
 267                 err = -errno;
 268                 log_debug_errno(errno, "can not stat() node '%s' (%m)", devnode);
 269                 goto out;
 270         }
 271
 272         if (((stats.st_mode & S_IFMT) != (mode & S_IFMT)) || (stats.st_rdev != devnum)) {
 273                 err = -EEXIST;
 274                 log_debug("found node '%s' with non-matching devnum %s, skip handling",
 275                           udev_device_get_devnode(dev), udev_device_get_id_filename(dev));
 276                 goto out;
 277         }
 278
 279         if (apply) {
 280                 bool selinux = false;
 281                 bool smack = false;
 282
 283                 if ((stats.st_mode & 0777) != (mode & 0777) || stats.st_uid != uid || stats.st_gid != gid) {
 284                         log_debug("set permissions %s, %#o, uid=%u, gid=%u", devnode, mode, uid, gid);
 285                         err = chmod(devnode, mode);
 286                         if (err < 0)
 287                                 log_warning_errno(errno, "setting mode of %s to %#o failed: %m", devnode, mode);
 288                         err = chown(devnode, uid, gid);
 289                         if (err < 0)
 290                                 log_warning_errno(errno, "setting owner of %s to uid=%u, gid=%u failed: %m", devnode, uid, gid);
 291                 } else {
 292                         log_debug("preserve permissions %s, %#o, uid=%u, gid=%u", devnode, mode, uid, gid);
 293                 }
 294
 295                 /* apply SECLABEL{$module}=$label */
 296                 udev_list_entry_foreach(entry, udev_list_get_entry(seclabel_list)) {
 297                         const char *name, *label;
 298                         int r;
 299
 300                         name = udev_list_entry_get_name(entry);
 301                         label = udev_list_entry_get_value(entry);
 302
 303                         if (streq(name, "selinux")) {
 304                                 selinux = true;
 305
 306                                 r = mac_selinux_apply(devnode, label);
 307                                 if (r < 0)
 308                                         log_error_errno(r, "SECLABEL: failed to set SELinux label '%s': %m", label);
 309                                 else
 310                                         log_debug("SECLABEL: set SELinux label '%s'", label);
 311
 312                         } else if (streq(name, "smack")) {
 313                                 smack = true;
 314
 315                                 r = mac_smack_apply(devnode, label);
 316                                 if (r < 0)
 317                                         log_error_errno(r, "SECLABEL: failed to set SMACK label '%s': %m", label);
 318                                 else
 319                                         log_debug("SECLABEL: set SMACK label '%s'", label);
 320
 321                         } else
 322                                 log_error("SECLABEL: unknown subsystem, ignoring '%s'='%s'", name, label);
 323                 }
 324
 325                 /* set the defaults */
 326                 if (!selinux)
 327                         mac_selinux_fix(devnode, true, false);
 328                 if (!smack)
 329                         mac_smack_apply(devnode, NULL);
 330         }
 331
 332         /* always update timestamp when we re-use the node, like on media change events */
 333         utimensat(AT_FDCWD, devnode, NULL, 0);
 334 out:
 335         return err;
 336 }
 337
 338 void udev_node_add(struct udev_device *dev, bool apply,
 339                    mode_t mode, uid_t uid, gid_t gid,
 340                    struct udev_list *seclabel_list) {
 341         char filename[UTIL_PATH_SIZE];
 342         struct udev_list_entry *list_entry;
 343
 344         log_debug("handling device node '%s', devnum=%s, mode=%#o, uid="UID_FMT", gid="GID_FMT,
 345                   udev_device_get_devnode(dev), udev_device_get_id_filename(dev), mode, uid, gid);
 346
 347         if (node_permissions_apply(dev, apply, mode, uid, gid, seclabel_list) < 0)
 348                 return;
 349
 350         /* always add /dev/{block,char}/$major:$minor */
 351         snprintf(filename, sizeof(filename), "/dev/%s/%u:%u",
 352                  streq(udev_device_get_subsystem(dev), "block") ? "block" : "char",
 353                  major(udev_device_get_devnum(dev)), minor(udev_device_get_devnum(dev)));
 354         node_symlink(dev, udev_device_get_devnode(dev), filename);
 355
 356         /* create/update symlinks, add symlinks to name index */
 357         udev_list_entry_foreach(list_entry, udev_device_get_devlinks_list_entry(dev))
 358                         link_update(dev, udev_list_entry_get_name(list_entry), true);
 359 }
 360
 361 void udev_node_remove(struct udev_device *dev) {
 362         struct udev_list_entry *list_entry;
 363         char filename[UTIL_PATH_SIZE];
 364
 365         /* remove/update symlinks, remove symlinks from name index */
 366         udev_list_entry_foreach(list_entry, udev_device_get_devlinks_list_entry(dev))
 367                 link_update(dev, udev_list_entry_get_name(list_entry), false);
 368
 369         /* remove /dev/{block,char}/$major:$minor */
 370         snprintf(filename, sizeof(filename), "/dev/%s/%u:%u",
 371                  streq(udev_device_get_subsystem(dev), "block") ? "block" : "char",
 372                  major(udev_device_get_devnum(dev)), minor(udev_device_get_devnum(dev)));
 373         unlink(filename);
 374 }