udev-node.c revision 48a849ee17fb25e0001bfcc0f28a4aa633d016a1
/*
* Copyright (C) 2003-2010 Kay Sievers <kay@vrfy.org>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <stddef.h>
#include <stdbool.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <grp.h>
#include <dirent.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <sys/types.h>
#include "udev.h"
#define TMP_FILE_EXT ".udev-tmp"
static int node_symlink(struct udev *udev, const char *node, const char *slink)
{
struct stat stats;
char target[UTIL_PATH_SIZE];
char *s;
size_t l;
char slink_tmp[UTIL_PATH_SIZE + sizeof(TMP_FILE_EXT)];
int i = 0;
int tail = 0;
int err = 0;
/* use relative link */
target[0] = '\0';
while (node[i] && (node[i] == slink[i])) {
if (node[i] == '/')
tail = i+1;
i++;
}
s = target;
l = sizeof(target);
while (slink[i] != '\0') {
if (slink[i] == '/')
l = util_strpcpy(&s, l, "../");
i++;
}
l = util_strscpy(s, l, &node[tail]);
if (l == 0) {
err = -EINVAL;
goto exit;
}
/* preserve link with correct target, do not replace node of other device */
if (lstat(slink, &stats) == 0) {
if (S_ISBLK(stats.st_mode) || S_ISCHR(stats.st_mode)) {
log_error("conflicting device node '%s' found, link to '%s' will not be created\n", slink, node);
goto exit;
} else if (S_ISLNK(stats.st_mode)) {
char buf[UTIL_PATH_SIZE];
int len;
len = readlink(slink, buf, sizeof(buf));
if (len > 0 && len < (int)sizeof(buf)) {
buf[len] = '\0';
if (strcmp(target, buf) == 0) {
log_debug("preserve already existing symlink '%s' to '%s'\n", slink, target);
label_fix(slink, true, false);
utimensat(AT_FDCWD, slink, NULL, AT_SYMLINK_NOFOLLOW);
goto exit;
}
}
}
} else {
log_debug("creating symlink '%s' to '%s'\n", slink, target);
do {
err = mkdir_parents_label(slink, 0755);
if (err != 0 && err != -ENOENT)
break;
label_context_set(slink, S_IFLNK);
err = symlink(target, slink);
if (err != 0)
err = -errno;
label_context_clear();
} while (err == -ENOENT);
if (err == 0)
goto exit;
}
log_debug("atomically replace '%s'\n", slink);
util_strscpyl(slink_tmp, sizeof(slink_tmp), slink, TMP_FILE_EXT, NULL);
unlink(slink_tmp);
do {
err = mkdir_parents_label(slink_tmp, 0755);
if (err != 0 && err != -ENOENT)
break;
label_context_set(slink_tmp, S_IFLNK);
err = symlink(target, slink_tmp);
if (err != 0)
err = -errno;
label_context_clear();
} while (err == -ENOENT);
if (err != 0) {
log_error("symlink '%s' '%s' failed: %m\n", target, slink_tmp);
goto exit;
}
err = rename(slink_tmp, slink);
if (err != 0) {
log_error("rename '%s' '%s' failed: %m\n", slink_tmp, slink);
unlink(slink_tmp);
}
exit:
return err;
}
/* find device node of device with highest priority */
static const char *link_find_prioritized(struct udev_device *dev, bool add, const char *stackdir, char *buf, size_t bufsize)
{
struct udev *udev = udev_device_get_udev(dev);
DIR *dir;
int priority = 0;
const char *target = NULL;
if (add) {
priority = udev_device_get_devlink_priority(dev);
util_strscpy(buf, bufsize, udev_device_get_devnode(dev));
target = buf;
}
dir = opendir(stackdir);
if (dir == NULL)
return target;
for (;;) {
struct udev_device *dev_db;
struct dirent *dent;
dent = readdir(dir);
if (dent == NULL || dent->d_name[0] == '\0')
break;
if (dent->d_name[0] == '.')
continue;
log_debug("found '%s' claiming '%s'\n", dent->d_name, stackdir);
/* did we find ourself? */
if (strcmp(dent->d_name, udev_device_get_id_filename(dev)) == 0)
continue;
dev_db = udev_device_new_from_device_id(udev, dent->d_name);
if (dev_db != NULL) {
const char *devnode;
devnode = udev_device_get_devnode(dev_db);
if (devnode != NULL) {
if (target == NULL || udev_device_get_devlink_priority(dev_db) > priority) {
log_debug("'%s' claims priority %i for '%s'\n",
udev_device_get_syspath(dev_db), udev_device_get_devlink_priority(dev_db), stackdir);
priority = udev_device_get_devlink_priority(dev_db);
util_strscpy(buf, bufsize, devnode);
target = buf;
}
}
udev_device_unref(dev_db);
}
}
closedir(dir);
return target;
}
/* manage "stack of names" with possibly specified device priorities */
static void link_update(struct udev_device *dev, const char *slink, bool add)
{
struct udev *udev = udev_device_get_udev(dev);
char name_enc[UTIL_PATH_SIZE];
char filename[UTIL_PATH_SIZE * 2];
char dirname[UTIL_PATH_SIZE];
const char *target;
char buf[UTIL_PATH_SIZE];
util_path_encode(slink + strlen("/dev"), name_enc, sizeof(name_enc));
util_strscpyl(dirname, sizeof(dirname), "/run/udev/links/", name_enc, NULL);
util_strscpyl(filename, sizeof(filename), dirname, "/", udev_device_get_id_filename(dev), NULL);
if (!add && unlink(filename) == 0)
rmdir(dirname);
target = link_find_prioritized(dev, add, dirname, buf, sizeof(buf));
if (target == NULL) {
log_debug("no reference left, remove '%s'\n", slink);
if (unlink(slink) == 0)
util_delete_path(udev, slink);
} else {
log_debug("creating link '%s' to '%s'\n", slink, target);
node_symlink(udev, target, slink);
}
if (add) {
int err;
do {
int fd;
err = mkdir_parents(filename, 0755);
if (err != 0 && err != -ENOENT)
break;
fd = open(filename, O_WRONLY|O_CREAT|O_CLOEXEC|O_TRUNC|O_NOFOLLOW, 0444);
if (fd >= 0)
close(fd);
else
err = -errno;
} while (err == -ENOENT);
}
}
void udev_node_update_old_links(struct udev_device *dev, struct udev_device *dev_old)
{
struct udev_list_entry *list_entry;
/* update possible left-over symlinks */
udev_list_entry_foreach(list_entry, udev_device_get_devlinks_list_entry(dev_old)) {
const char *name = udev_list_entry_get_name(list_entry);
struct udev_list_entry *list_entry_current;
int found;
/* check if old link name still belongs to this device */
found = 0;
udev_list_entry_foreach(list_entry_current, udev_device_get_devlinks_list_entry(dev)) {
const char *name_current = udev_list_entry_get_name(list_entry_current);
if (strcmp(name, name_current) == 0) {
found = 1;
break;
}
}
if (found)
continue;
log_debug("update old name, '%s' no longer belonging to '%s'\n",
name, udev_device_get_devpath(dev));
link_update(dev, name, false);
}
}
static int node_fixup(struct udev_device *dev, mode_t mode, uid_t uid, gid_t gid)
{
const char *devnode = udev_device_get_devnode(dev);
dev_t devnum = udev_device_get_devnum(dev);
struct stat stats;
int err = 0;
if (strcmp(udev_device_get_subsystem(dev), "block") == 0)
mode |= S_IFBLK;
else
mode |= S_IFCHR;
if (lstat(devnode, &stats) != 0) {
err = -errno;
log_debug("can not stat() node '%s' (%m)\n", devnode);
goto out;
}
if (((stats.st_mode & S_IFMT) != (mode & S_IFMT)) || (stats.st_rdev != devnum)) {
err = -EEXIST;
log_debug("found node '%s' with non-matching devnum %s, skip handling\n",
udev_device_get_devnode(dev), udev_device_get_id_filename(dev));
goto out;
}
/*
* Set permissions and selinux file context only on add events. We always
* set it on bootup (coldplug) with "trigger --action=add" for all devices
* and for any newly added devices (hotplug). We don't want to change it
* later, in case something else has applied custom settings in the meantime.
*/
if (strcmp(udev_device_get_action(dev), "add") == 0) {
if ((stats.st_mode & 0777) != (mode & 0777) || stats.st_uid != uid || stats.st_gid != gid) {
log_debug("set permissions %s, %#o, uid=%u, gid=%u\n", devnode, mode, uid, gid);
chmod(devnode, mode);
chown(devnode, uid, gid);
} else {
log_debug("preserve permissions %s, %#o, uid=%u, gid=%u\n", devnode, mode, uid, gid);
}
label_fix(devnode, true, false);
}
/* always update timestamp when we re-use the node, like on media change events */
utimensat(AT_FDCWD, devnode, NULL, 0);
out:
return err;
}
void udev_node_add(struct udev_device *dev, mode_t mode, uid_t uid, gid_t gid)
{
struct udev *udev = udev_device_get_udev(dev);
char filename[UTIL_PATH_SIZE];
struct udev_list_entry *list_entry;
log_debug("handling device node '%s', devnum=%s, mode=%#o, uid=%d, gid=%d\n",
udev_device_get_devnode(dev), udev_device_get_id_filename(dev), mode, uid, gid);
if (node_fixup(dev, mode, uid, gid) < 0)
return;
/* always add /dev/{block,char}/$major:$minor */
snprintf(filename, sizeof(filename), "/dev/%s/%u:%u",
strcmp(udev_device_get_subsystem(dev), "block") == 0 ? "block" : "char",
major(udev_device_get_devnum(dev)), minor(udev_device_get_devnum(dev)));
node_symlink(udev, udev_device_get_devnode(dev), filename);
/* create/update symlinks, add symlinks to name index */
udev_list_entry_foreach(list_entry, udev_device_get_devlinks_list_entry(dev))
link_update(dev, udev_list_entry_get_name(list_entry), true);
}
void udev_node_remove(struct udev_device *dev)
{
struct udev_list_entry *list_entry;
char filename[UTIL_PATH_SIZE];
/* remove/update symlinks, remove symlinks from name index */
udev_list_entry_foreach(list_entry, udev_device_get_devlinks_list_entry(dev))
link_update(dev, udev_list_entry_get_name(list_entry), false);
/* remove /dev/{block,char}/$major:$minor */
snprintf(filename, sizeof(filename), "/dev/%s/%u:%u",
strcmp(udev_device_get_subsystem(dev), "block") == 0 ? "block" : "char",
major(udev_device_get_devnum(dev)), minor(udev_device_get_devnum(dev)));
unlink(filename);
}