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
  34 static int node_symlink(struct udev_device *dev, const char *node, const char *slink)
  35 {
  36         struct stat stats;
  37         char target[UTIL_PATH_SIZE];
  38         char *s;
  39         size_t l;
  40         char slink_tmp[UTIL_PATH_SIZE + 32];
  41         int i = 0;
  42         int tail = 0;
  43         int err = 0;
  44
  45         /* use relative link */
  46         target[0] = '\0';
  47         while (node[i] && (node[i] == slink[i])) {
  48                 if (node[i] == '/')
  49                         tail = i+1;
  50                 i++;
  51         }
  52         s = target;
  53         l = sizeof(target);
  54         while (slink[i] != '\0') {
  55                 if (slink[i] == '/')
  56                         l = strpcpy(&s, l, "../");
  57                 i++;
  58         }
  59         l = strscpy(s, l, &node[tail]);
  60         if (l == 0) {
  61                 err = -EINVAL;
  62                 goto exit;
  63         }
  64
  65         /* preserve link with correct target, do not replace node of other device */
  66         if (lstat(slink, &stats) == 0) {
  67                 if (S_ISBLK(stats.st_mode) || S_ISCHR(stats.st_mode)) {
  68                         log_error("conflicting device node '%s' found, link to '%s' will not be created\n", slink, node);
  69                         goto exit;
  70                 } else if (S_ISLNK(stats.st_mode)) {
  71                         char buf[UTIL_PATH_SIZE];
  72                         int len;
  73
  74                         len = readlink(slink, buf, sizeof(buf));
  75                         if (len > 0 && len < (int)sizeof(buf)) {
  76                                 buf[len] = '\0';
  77                                 if (streq(target, buf)) {
  78                                         log_debug("preserve already existing symlink '%s' to '%s'\n", slink, target);
  79                                         label_fix(slink, true, false);
  80                                         utimensat(AT_FDCWD, slink, NULL, AT_SYMLINK_NOFOLLOW);
  81                                         goto exit;
  82                                 }
  83                         }
  84                 }
  85         } else {
  86                 log_debug("creating symlink '%s' to '%s'\n", slink, target);
  87                 do {
  88                         err = mkdir_parents_label(slink, 0755);
  89                         if (err != 0 && err != -ENOENT)
  90                                 break;
  91                         label_context_set(slink, S_IFLNK);
  92                         err = symlink(target, slink);
  93                         if (err != 0)
  94                                 err = -errno;
  95                         label_context_clear();
  96                 } while (err == -ENOENT);
  97                 if (err == 0)
  98                         goto exit;
  99         }
 100
 101         log_debug("atomically replace '%s'\n", slink);
 102         strscpyl(slink_tmp, sizeof(slink_tmp), slink, ".tmp-", udev_device_get_id_filename(dev), NULL);
 103         unlink(slink_tmp);
 104         do {
 105                 err = mkdir_parents_label(slink_tmp, 0755);
 106                 if (err != 0 && err != -ENOENT)
 107                         break;
 108                 label_context_set(slink_tmp, S_IFLNK);
 109                 err = symlink(target, slink_tmp);
 110                 if (err != 0)
 111                         err = -errno;
 112                 label_context_clear();
 113         } while (err == -ENOENT);
 114         if (err != 0) {
 115                 log_error("symlink '%s' '%s' failed: %m\n", target, slink_tmp);
 116                 goto exit;
 117         }
 118         err = rename(slink_tmp, slink);
 119         if (err != 0) {
 120                 log_error("rename '%s' '%s' failed: %m\n", slink_tmp, slink);
 121                 unlink(slink_tmp);
 122         }
 123 exit:
 124         return err;
 125 }
 126
 127 /* find device node of device with highest priority */
 128 static const char *link_find_prioritized(struct udev_device *dev, bool add, const char *stackdir, char *buf, size_t bufsize)
 129 {
 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'\n", 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'\n",
 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 {
 184         struct udev *udev = udev_device_get_udev(dev);
 185         char name_enc[UTIL_PATH_SIZE];
 186         char filename[UTIL_PATH_SIZE * 2];
 187         char dirname[UTIL_PATH_SIZE];
 188         const char *target;
 189         char buf[UTIL_PATH_SIZE];
 190
 191         util_path_encode(slink + strlen("/dev"), name_enc, sizeof(name_enc));
 192         strscpyl(dirname, sizeof(dirname), "/run/udev/links/", name_enc, NULL);
 193         strscpyl(filename, sizeof(filename), dirname, "/", udev_device_get_id_filename(dev), NULL);
 194
 195         if (!add && unlink(filename) == 0)
 196                 rmdir(dirname);
 197
 198         target = link_find_prioritized(dev, add, dirname, buf, sizeof(buf));
 199         if (target == NULL) {
 200                 log_debug("no reference left, remove '%s'\n", slink);
 201                 if (unlink(slink) == 0)
 202                         util_delete_path(udev, slink);
 203         } else {
 204                 log_debug("creating link '%s' to '%s'\n", slink, target);
 205                 node_symlink(dev, target, slink);
 206         }
 207
 208         if (add) {
 209                 int err;
 210
 211                 do {
 212                         int fd;
 213
 214                         err = mkdir_parents(filename, 0755);
 215                         if (err != 0 && err != -ENOENT)
 216                                 break;
 217                         fd = open(filename, O_WRONLY|O_CREAT|O_CLOEXEC|O_TRUNC|O_NOFOLLOW, 0444);
 218                         if (fd >= 0)
 219                                 close(fd);
 220                         else
 221                                 err = -errno;
 222                 } while (err == -ENOENT);
 223         }
 224 }
 225
 226 void udev_node_update_old_links(struct udev_device *dev, struct udev_device *dev_old)
 227 {
 228         struct udev_list_entry *list_entry;
 229
 230         /* update possible left-over symlinks */
 231         udev_list_entry_foreach(list_entry, udev_device_get_devlinks_list_entry(dev_old)) {
 232                 const char *name = udev_list_entry_get_name(list_entry);
 233                 struct udev_list_entry *list_entry_current;
 234                 int found;
 235
 236                 /* check if old link name still belongs to this device */
 237                 found = 0;
 238                 udev_list_entry_foreach(list_entry_current, udev_device_get_devlinks_list_entry(dev)) {
 239                         const char *name_current = udev_list_entry_get_name(list_entry_current);
 240
 241                         if (streq(name, name_current)) {
 242                                 found = 1;
 243                                 break;
 244                         }
 245                 }
 246                 if (found)
 247                         continue;
 248
 249                 log_debug("update old name, '%s' no longer belonging to '%s'\n",
 250                      name, udev_device_get_devpath(dev));
 251                 link_update(dev, name, false);
 252         }
 253 }
 254
 255 static int node_permissions_apply(struct udev_device *dev, bool apply, mode_t mode, uid_t uid, gid_t gid)
 256 {
 257         const char *devnode = udev_device_get_devnode(dev);
 258         dev_t devnum = udev_device_get_devnum(dev);
 259         struct stat stats;
 260         int err = 0;
 261
 262         if (streq(udev_device_get_subsystem(dev), "block"))
 263                 mode |= S_IFBLK;
 264         else
 265                 mode |= S_IFCHR;
 266
 267         if (lstat(devnode, &stats) != 0) {
 268                 err = -errno;
 269                 log_debug("can not stat() node '%s' (%m)\n", devnode);
 270                 goto out;
 271         }
 272
 273         if (((stats.st_mode & S_IFMT) != (mode & S_IFMT)) || (stats.st_rdev != devnum)) {
 274                 err = -EEXIST;
 275                 log_debug("found node '%s' with non-matching devnum %s, skip handling\n",
 276                           udev_device_get_devnode(dev), udev_device_get_id_filename(dev));
 277                 goto out;
 278         }
 279
 280         if (apply) {
 281                 if ((stats.st_mode & 0777) != (mode & 0777) || stats.st_uid != uid || stats.st_gid != gid) {
 282                         log_debug("set permissions %s, %#o, uid=%u, gid=%u\n", devnode, mode, uid, gid);
 283                         chmod(devnode, mode);
 284                         chown(devnode, uid, gid);
 285                 } else {
 286                         log_debug("preserve permissions %s, %#o, uid=%u, gid=%u\n", devnode, mode, uid, gid);
 287                 }
 288                 label_fix(devnode, true, false);
 289         }
 290
 291         /* always update timestamp when we re-use the node, like on media change events */
 292         utimensat(AT_FDCWD, devnode, NULL, 0);
 293 out:
 294         return err;
 295 }
 296
 297 void udev_node_add(struct udev_device *dev, bool apply, mode_t mode, uid_t uid, gid_t gid)
 298 {
 299         char filename[UTIL_PATH_SIZE];
 300         struct udev_list_entry *list_entry;
 301
 302         log_debug("handling device node '%s', devnum=%s, mode=%#o, uid=%d, gid=%d\n",
 303                   udev_device_get_devnode(dev), udev_device_get_id_filename(dev), mode, uid, gid);
 304
 305         if (node_permissions_apply(dev, apply, mode, uid, gid) < 0)
 306                 return;
 307
 308         /* always add /dev/{block,char}/$major:$minor */
 309         snprintf(filename, sizeof(filename), "/dev/%s/%u:%u",
 310                  streq(udev_device_get_subsystem(dev), "block") ? "block" : "char",
 311                  major(udev_device_get_devnum(dev)), minor(udev_device_get_devnum(dev)));
 312         node_symlink(dev, udev_device_get_devnode(dev), filename);
 313
 314         /* create/update symlinks, add symlinks to name index */
 315         udev_list_entry_foreach(list_entry, udev_device_get_devlinks_list_entry(dev))
 316                         link_update(dev, udev_list_entry_get_name(list_entry), true);
 317 }
 318
 319 void udev_node_remove(struct udev_device *dev)
 320 {
 321         struct udev_list_entry *list_entry;
 322         char filename[UTIL_PATH_SIZE];
 323
 324         /* remove/update symlinks, remove symlinks from name index */
 325         udev_list_entry_foreach(list_entry, udev_device_get_devlinks_list_entry(dev))
 326                 link_update(dev, udev_list_entry_get_name(list_entry), false);
 327
 328         /* remove /dev/{block,char}/$major:$minor */
 329         snprintf(filename, sizeof(filename), "/dev/%s/%u:%u",
 330                  streq(udev_device_get_subsystem(dev), "block") ? "block" : "char",
 331                  major(udev_device_get_devnum(dev)), minor(udev_device_get_devnum(dev)));
 332         unlink(filename);
 333 }