src/udev/udev-node.c

   1 /*
   2  * Copyright (C) 2003-2010 Kay Sievers <kay.sievers@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 #define TMP_FILE_EXT                ".udev-tmp"
  35
  36 static int node_symlink(struct udev *udev, const char *node, const char *slink)
  37 {
  38         struct stat stats;
  39         char target[UTIL_PATH_SIZE];
  40         char *s;
  41         size_t l;
  42         char slink_tmp[UTIL_PATH_SIZE + sizeof(TMP_FILE_EXT)];
  43         int i = 0;
  44         int tail = 0;
  45         int err = 0;
  46
  47         /* use relative link */
  48         target[0] = '\0';
  49         while (node[i] && (node[i] == slink[i])) {
  50                 if (node[i] == '/')
  51                         tail = i+1;
  52                 i++;
  53         }
  54         s = target;
  55         l = sizeof(target);
  56         while (slink[i] != '\0') {
  57                 if (slink[i] == '/')
  58                         l = util_strpcpy(&s, l, "../");
  59                 i++;
  60         }
  61         l = util_strscpy(s, l, &node[tail]);
  62         if (l == 0) {
  63                 err = -EINVAL;
  64                 goto exit;
  65         }
  66
  67         /* preserve link with correct target, do not replace node of other device */
  68         if (lstat(slink, &stats) == 0) {
  69                 if (S_ISBLK(stats.st_mode) || S_ISCHR(stats.st_mode)) {
  70                         log_error("conflicting device node '%s' found, link to '%s' will not be created\n", slink, node);
  71                         goto exit;
  72                 } else if (S_ISLNK(stats.st_mode)) {
  73                         char buf[UTIL_PATH_SIZE];
  74                         int len;
  75
  76                         len = readlink(slink, buf, sizeof(buf));
  77                         if (len > 0 && len < (int)sizeof(buf)) {
  78                                 buf[len] = '\0';
  79                                 if (strcmp(target, buf) == 0) {
  80                                         log_debug("preserve already existing symlink '%s' to '%s'\n", slink, target);
  81                                         label_fix(slink, true, false);
  82                                         utimensat(AT_FDCWD, slink, NULL, AT_SYMLINK_NOFOLLOW);
  83                                         goto exit;
  84                                 }
  85                         }
  86                 }
  87         } else {
  88                 log_debug("creating symlink '%s' to '%s'\n", slink, target);
  89                 do {
  90                         err = mkdir_parents_label(slink, 0755);
  91                         if (err != 0 && err != -ENOENT)
  92                                 break;
  93                         label_context_set(slink, S_IFLNK);
  94                         err = symlink(target, slink);
  95                         if (err != 0)
  96                                 err = -errno;
  97                         label_context_clear();
  98                 } while (err == -ENOENT);
  99                 if (err == 0)
 100                         goto exit;
 101         }
 102
 103         log_debug("atomically replace '%s'\n", slink);
 104         util_strscpyl(slink_tmp, sizeof(slink_tmp), slink, TMP_FILE_EXT, NULL);
 105         unlink(slink_tmp);
 106         do {
 107                 err = mkdir_parents_label(slink_tmp, 0755);
 108                 if (err != 0 && err != -ENOENT)
 109                         break;
 110                 label_context_set(slink_tmp, S_IFLNK);
 111                 err = symlink(target, slink_tmp);
 112                 if (err != 0)
 113                         err = -errno;
 114                 label_context_clear();
 115         } while (err == -ENOENT);
 116         if (err != 0) {
 117                 log_error("symlink '%s' '%s' failed: %m\n", target, slink_tmp);
 118                 goto exit;
 119         }
 120         err = rename(slink_tmp, slink);
 121         if (err != 0) {
 122                 log_error("rename '%s' '%s' failed: %m\n", slink_tmp, slink);
 123                 unlink(slink_tmp);
 124         }
 125 exit:
 126         return err;
 127 }
 128
 129 /* find device node of device with highest priority */
 130 static const char *link_find_prioritized(struct udev_device *dev, bool add, const char *stackdir, char *buf, size_t bufsize)
 131 {
 132         struct udev *udev = udev_device_get_udev(dev);
 133         DIR *dir;
 134         int priority = 0;
 135         const char *target = NULL;
 136
 137         if (add) {
 138                 priority = udev_device_get_devlink_priority(dev);
 139                 util_strscpy(buf, bufsize, udev_device_get_devnode(dev));
 140                 target = buf;
 141         }
 142
 143         dir = opendir(stackdir);
 144         if (dir == NULL)
 145                 return target;
 146         for (;;) {
 147                 struct udev_device *dev_db;
 148                 struct dirent *dent;
 149
 150                 dent = readdir(dir);
 151                 if (dent == NULL || dent->d_name[0] == '\0')
 152                         break;
 153                 if (dent->d_name[0] == '.')
 154                         continue;
 155
 156                 log_debug("found '%s' claiming '%s'\n", dent->d_name, stackdir);
 157
 158                 /* did we find ourself? */
 159                 if (strcmp(dent->d_name, udev_device_get_id_filename(dev)) == 0)
 160                         continue;
 161
 162                 dev_db = udev_device_new_from_id_filename(udev, dent->d_name);
 163                 if (dev_db != NULL) {
 164                         const char *devnode;
 165
 166                         devnode = udev_device_get_devnode(dev_db);
 167                         if (devnode != NULL) {
 168                                 if (target == NULL || udev_device_get_devlink_priority(dev_db) > priority) {
 169                                         log_debug("'%s' claims priority %i for '%s'\n",
 170                                                   udev_device_get_syspath(dev_db), udev_device_get_devlink_priority(dev_db), stackdir);
 171                                         priority = udev_device_get_devlink_priority(dev_db);
 172                                         util_strscpy(buf, bufsize, devnode);
 173                                         target = buf;
 174                                 }
 175                         }
 176                         udev_device_unref(dev_db);
 177                 }
 178         }
 179         closedir(dir);
 180         return target;
 181 }
 182
 183 /* manage "stack of names" with possibly specified device priorities */
 184 static void link_update(struct udev_device *dev, const char *slink, bool add)
 185 {
 186         struct udev *udev = udev_device_get_udev(dev);
 187         char name_enc[UTIL_PATH_SIZE];
 188         char filename[UTIL_PATH_SIZE * 2];
 189         char dirname[UTIL_PATH_SIZE];
 190         const char *target;
 191         char buf[UTIL_PATH_SIZE];
 192
 193         util_path_encode(slink + strlen("/dev"), name_enc, sizeof(name_enc));
 194         util_strscpyl(dirname, sizeof(dirname), "/run/udev/links/", name_enc, NULL);
 195         util_strscpyl(filename, sizeof(filename), dirname, "/", udev_device_get_id_filename(dev), NULL);
 196
 197         if (!add && unlink(filename) == 0)
 198                 rmdir(dirname);
 199
 200         target = link_find_prioritized(dev, add, dirname, buf, sizeof(buf));
 201         if (target == NULL) {
 202                 log_debug("no reference left, remove '%s'\n", slink);
 203                 if (unlink(slink) == 0)
 204                         util_delete_path(udev, slink);
 205         } else {
 206                 log_debug("creating link '%s' to '%s'\n", slink, target);
 207                 node_symlink(udev, target, slink);
 208         }
 209
 210         if (add) {
 211                 int err;
 212
 213                 do {
 214                         int fd;
 215
 216                         err = mkdir_parents(filename, 0755);
 217                         if (err != 0 && err != -ENOENT)
 218                                 break;
 219                         fd = open(filename, O_WRONLY|O_CREAT|O_CLOEXEC|O_TRUNC|O_NOFOLLOW, 0444);
 220                         if (fd >= 0)
 221                                 close(fd);
 222                         else
 223                                 err = -errno;
 224                 } while (err == -ENOENT);
 225         }
 226 }
 227
 228 void udev_node_update_old_links(struct udev_device *dev, struct udev_device *dev_old)
 229 {
 230         struct udev_list_entry *list_entry;
 231
 232         /* update possible left-over symlinks */
 233         udev_list_entry_foreach(list_entry, udev_device_get_devlinks_list_entry(dev_old)) {
 234                 const char *name = udev_list_entry_get_name(list_entry);
 235                 struct udev_list_entry *list_entry_current;
 236                 int found;
 237
 238                 /* check if old link name still belongs to this device */
 239                 found = 0;
 240                 udev_list_entry_foreach(list_entry_current, udev_device_get_devlinks_list_entry(dev)) {
 241                         const char *name_current = udev_list_entry_get_name(list_entry_current);
 242
 243                         if (strcmp(name, name_current) == 0) {
 244                                 found = 1;
 245                                 break;
 246                         }
 247                 }
 248                 if (found)
 249                         continue;
 250
 251                 log_debug("update old name, '%s' no longer belonging to '%s'\n",
 252                      name, udev_device_get_devpath(dev));
 253                 link_update(dev, name, 0);
 254         }
 255 }
 256
 257 static int node_fixup(struct udev_device *dev, mode_t mode, uid_t uid, gid_t gid)
 258 {
 259         const char *devnode = udev_device_get_devnode(dev);
 260         dev_t devnum = udev_device_get_devnum(dev);
 261         struct stat stats;
 262         int err = 0;
 263
 264         if (strcmp(udev_device_get_subsystem(dev), "block") == 0)
 265                 mode |= S_IFBLK;
 266         else
 267                 mode |= S_IFCHR;
 268
 269         if (lstat(devnode, &stats) != 0) {
 270                 err = -errno;
 271                 log_debug("can not stat() node '%s' (%m)\n", devnode);
 272                 goto out;
 273         }
 274
 275         if (((stats.st_mode & S_IFMT) != (mode & S_IFMT)) || (stats.st_rdev != devnum)) {
 276                 err = -EEXIST;
 277                 log_debug("found node '%s' with non-matching devnum %s, skip handling\n",
 278                           udev_device_get_devnode(dev), udev_device_get_id_filename(dev));
 279                 goto out;
 280         }
 281
 282         if ((stats.st_mode & 0777) != (mode & 0777) || stats.st_uid != uid || stats.st_gid != gid) {
 283                 log_debug("set permissions %s, %#o, uid=%u, gid=%u\n", devnode, mode, uid, gid);
 284                 chmod(devnode, mode);
 285                 chown(devnode, uid, gid);
 286         } else {
 287                 log_debug("preserve permissions %s, %#o, uid=%u, gid=%u\n", devnode, mode, uid, gid);
 288         }
 289
 290         /*
 291          * Set initial selinux file context only on add events.
 292          * We set the proper context on bootup (triger) or for newly
 293          * added devices, but we don't change it later, in case
 294          * something else has set a custom context in the meantime.
 295          */
 296         if (strcmp(udev_device_get_action(dev), "add") == 0)
 297             label_fix(devnode, true, false);
 298
 299         /* always update timestamp when we re-use the node, like on media change events */
 300         utimensat(AT_FDCWD, devnode, NULL, 0);
 301 out:
 302         return err;
 303 }
 304
 305 void udev_node_add(struct udev_device *dev, mode_t mode, uid_t uid, gid_t gid)
 306 {
 307         struct udev *udev = udev_device_get_udev(dev);
 308         char filename[UTIL_PATH_SIZE];
 309         struct udev_list_entry *list_entry;
 310
 311         log_debug("handling device node '%s', devnum=%s, mode=%#o, uid=%d, gid=%d\n",
 312                   udev_device_get_devnode(dev), udev_device_get_id_filename(dev), mode, uid, gid);
 313
 314         if (node_fixup(dev, mode, uid, gid) < 0)
 315                 return;
 316
 317         /* always add /dev/{block,char}/$major:$minor */
 318         snprintf(filename, sizeof(filename), "/dev/%s/%u:%u",
 319                  strcmp(udev_device_get_subsystem(dev), "block") == 0 ? "block" : "char",
 320                  major(udev_device_get_devnum(dev)), minor(udev_device_get_devnum(dev)));
 321         node_symlink(udev, udev_device_get_devnode(dev), filename);
 322
 323         /* create/update symlinks, add symlinks to name index */
 324         udev_list_entry_foreach(list_entry, udev_device_get_devlinks_list_entry(dev)) {
 325                 if (udev_list_entry_get_num(list_entry))
 326                         /* simple unmanaged link name */
 327                         node_symlink(udev, udev_device_get_devnode(dev), udev_list_entry_get_name(list_entry));
 328                 else
 329                         link_update(dev, udev_list_entry_get_name(list_entry), 1);
 330         }
 331 }
 332
 333 void udev_node_remove(struct udev_device *dev)
 334 {
 335         struct udev_list_entry *list_entry;
 336         char filename[UTIL_PATH_SIZE];
 337
 338         /* remove/update symlinks, remove symlinks from name index */
 339         udev_list_entry_foreach(list_entry, udev_device_get_devlinks_list_entry(dev))
 340                 link_update(dev, udev_list_entry_get_name(list_entry), 0);
 341
 342         /* remove /dev/{block,char}/$major:$minor */
 343         snprintf(filename, sizeof(filename), "/dev/%s/%u:%u",
 344                  strcmp(udev_device_get_subsystem(dev), "block") == 0 ? "block" : "char",
 345                  major(udev_device_get_devnum(dev)), minor(udev_device_get_devnum(dev)));
 346         unlink(filename);
 347 }