375 lines
15 KiB
C
375 lines
15 KiB
C
/*
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* Copyright (C) 2003-2013 Kay Sievers <kay@vrfy.org>
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <errno.h>
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#include <fcntl.h>
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#include <stdbool.h>
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#include <stddef.h>
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#include <stdio.h>
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#include <string.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include "dirent-util.h"
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#include "format-util.h"
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#include "fs-util.h"
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#include "selinux-util.h"
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#include "smack-util.h"
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#include "stdio-util.h"
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#include "string-util.h"
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#include "udev.h"
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static int node_symlink(struct udev_device *dev, const char *node, const char *slink) {
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struct stat stats;
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char target[UTIL_PATH_SIZE];
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char *s;
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size_t l;
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char slink_tmp[UTIL_PATH_SIZE + 32];
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int i = 0;
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int tail = 0;
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int err = 0;
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/* use relative link */
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target[0] = '\0';
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while (node[i] && (node[i] == slink[i])) {
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if (node[i] == '/')
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tail = i+1;
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i++;
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}
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s = target;
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l = sizeof(target);
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while (slink[i] != '\0') {
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if (slink[i] == '/')
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l = strpcpy(&s, l, "../");
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i++;
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}
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l = strscpy(s, l, &node[tail]);
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if (l == 0) {
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err = -EINVAL;
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goto exit;
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}
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/* preserve link with correct target, do not replace node of other device */
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if (lstat(slink, &stats) == 0) {
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if (S_ISBLK(stats.st_mode) || S_ISCHR(stats.st_mode)) {
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log_error("conflicting device node '%s' found, link to '%s' will not be created", slink, node);
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goto exit;
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} else if (S_ISLNK(stats.st_mode)) {
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char buf[UTIL_PATH_SIZE];
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int len;
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len = readlink(slink, buf, sizeof(buf));
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if (len > 0 && len < (int)sizeof(buf)) {
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buf[len] = '\0';
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if (streq(target, buf)) {
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log_debug("preserve already existing symlink '%s' to '%s'", slink, target);
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label_fix(slink, true, false);
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utimensat(AT_FDCWD, slink, NULL, AT_SYMLINK_NOFOLLOW);
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goto exit;
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}
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}
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}
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} else {
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log_debug("creating symlink '%s' to '%s'", slink, target);
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do {
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err = mkdir_parents_label(slink, 0755);
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if (err != 0 && err != -ENOENT)
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break;
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mac_selinux_create_file_prepare(slink, S_IFLNK);
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err = symlink(target, slink);
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if (err != 0)
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err = -errno;
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mac_selinux_create_file_clear();
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} while (err == -ENOENT);
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if (err == 0)
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goto exit;
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}
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log_debug("atomically replace '%s'", slink);
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strscpyl(slink_tmp, sizeof(slink_tmp), slink, ".tmp-", udev_device_get_id_filename(dev), NULL);
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unlink(slink_tmp);
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do {
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err = mkdir_parents_label(slink_tmp, 0755);
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if (err != 0 && err != -ENOENT)
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break;
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mac_selinux_create_file_prepare(slink_tmp, S_IFLNK);
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err = symlink(target, slink_tmp);
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if (err != 0)
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err = -errno;
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mac_selinux_create_file_clear();
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} while (err == -ENOENT);
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if (err != 0) {
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log_error_errno(errno, "symlink '%s' '%s' failed: %m", target, slink_tmp);
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goto exit;
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}
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err = rename(slink_tmp, slink);
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if (err != 0) {
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log_error_errno(errno, "rename '%s' '%s' failed: %m", slink_tmp, slink);
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unlink(slink_tmp);
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}
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exit:
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return err;
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}
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/* find device node of device with highest priority */
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static const char *link_find_prioritized(struct udev_device *dev, bool add, const char *stackdir, char *buf, size_t bufsize) {
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struct udev *udev = udev_device_get_udev(dev);
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DIR *dir;
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struct dirent *dent;
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int priority = 0;
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const char *target = NULL;
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if (add) {
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priority = udev_device_get_devlink_priority(dev);
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strscpy(buf, bufsize, udev_device_get_devnode(dev));
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target = buf;
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}
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dir = opendir(stackdir);
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if (dir == NULL)
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return target;
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FOREACH_DIRENT_ALL(dent, dir, break) {
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struct udev_device *dev_db;
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if (dent->d_name[0] == '\0')
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break;
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if (dent->d_name[0] == '.')
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continue;
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log_debug("found '%s' claiming '%s'", dent->d_name, stackdir);
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/* did we find ourself? */
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if (streq(dent->d_name, udev_device_get_id_filename(dev)))
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continue;
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dev_db = udev_device_new_from_device_id(udev, dent->d_name);
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if (dev_db != NULL) {
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const char *devnode;
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devnode = udev_device_get_devnode(dev_db);
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if (devnode != NULL) {
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if (target == NULL || udev_device_get_devlink_priority(dev_db) > priority) {
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log_debug("'%s' claims priority %i for '%s'",
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udev_device_get_syspath(dev_db), udev_device_get_devlink_priority(dev_db), stackdir);
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priority = udev_device_get_devlink_priority(dev_db);
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strscpy(buf, bufsize, devnode);
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target = buf;
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}
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}
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udev_device_unref(dev_db);
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}
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}
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closedir(dir);
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return target;
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}
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/* manage "stack of names" with possibly specified device priorities */
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static void link_update(struct udev_device *dev, const char *slink, bool add) {
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char name_enc[UTIL_PATH_SIZE];
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char filename[UTIL_PATH_SIZE * 2];
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char dirname[UTIL_PATH_SIZE];
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const char *target;
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char buf[UTIL_PATH_SIZE];
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util_path_encode(slink + strlen("/dev"), name_enc, sizeof(name_enc));
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strscpyl(dirname, sizeof(dirname), "/run/udev/links/", name_enc, NULL);
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strscpyl(filename, sizeof(filename), dirname, "/", udev_device_get_id_filename(dev), NULL);
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if (!add && unlink(filename) == 0)
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rmdir(dirname);
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target = link_find_prioritized(dev, add, dirname, buf, sizeof(buf));
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if (target == NULL) {
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log_debug("no reference left, remove '%s'", slink);
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if (unlink(slink) == 0)
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rmdir_parents(slink, "/");
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} else {
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log_debug("creating link '%s' to '%s'", slink, target);
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node_symlink(dev, target, slink);
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}
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if (add) {
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int err;
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do {
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int fd;
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err = mkdir_parents(filename, 0755);
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if (err != 0 && err != -ENOENT)
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break;
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fd = open(filename, O_WRONLY|O_CREAT|O_CLOEXEC|O_TRUNC|O_NOFOLLOW, 0444);
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if (fd >= 0)
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close(fd);
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else
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err = -errno;
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} while (err == -ENOENT);
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}
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}
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void udev_node_update_old_links(struct udev_device *dev, struct udev_device *dev_old) {
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struct udev_list_entry *list_entry;
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/* update possible left-over symlinks */
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udev_list_entry_foreach(list_entry, udev_device_get_devlinks_list_entry(dev_old)) {
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const char *name = udev_list_entry_get_name(list_entry);
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struct udev_list_entry *list_entry_current;
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int found;
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/* check if old link name still belongs to this device */
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found = 0;
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udev_list_entry_foreach(list_entry_current, udev_device_get_devlinks_list_entry(dev)) {
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const char *name_current = udev_list_entry_get_name(list_entry_current);
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if (streq(name, name_current)) {
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found = 1;
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break;
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}
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}
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if (found)
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continue;
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log_debug("update old name, '%s' no longer belonging to '%s'",
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name, udev_device_get_devpath(dev));
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link_update(dev, name, false);
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}
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}
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static int node_permissions_apply(struct udev_device *dev, bool apply,
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mode_t mode, uid_t uid, gid_t gid,
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struct udev_list *seclabel_list) {
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const char *devnode = udev_device_get_devnode(dev);
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dev_t devnum = udev_device_get_devnum(dev);
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struct stat stats;
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struct udev_list_entry *entry;
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int err = 0;
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if (streq(udev_device_get_subsystem(dev), "block"))
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mode |= S_IFBLK;
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else
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mode |= S_IFCHR;
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if (lstat(devnode, &stats) != 0) {
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err = log_debug_errno(errno, "can not stat() node '%s' (%m)", devnode);
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goto out;
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}
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if (((stats.st_mode & S_IFMT) != (mode & S_IFMT)) || (stats.st_rdev != devnum)) {
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err = -EEXIST;
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log_debug("found node '%s' with non-matching devnum %s, skip handling",
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udev_device_get_devnode(dev), udev_device_get_id_filename(dev));
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goto out;
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}
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if (apply) {
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bool selinux = false;
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bool smack = false;
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if ((stats.st_mode & 0777) != (mode & 0777) || stats.st_uid != uid || stats.st_gid != gid) {
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log_debug("set permissions %s, %#o, uid=%u, gid=%u", devnode, mode, uid, gid);
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err = chmod(devnode, mode);
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if (err < 0)
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log_warning_errno(errno, "setting mode of %s to %#o failed: %m", devnode, mode);
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err = chown(devnode, uid, gid);
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if (err < 0)
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log_warning_errno(errno, "setting owner of %s to uid=%u, gid=%u failed: %m", devnode, uid, gid);
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} else {
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log_debug("preserve permissions %s, %#o, uid=%u, gid=%u", devnode, mode, uid, gid);
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}
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/* apply SECLABEL{$module}=$label */
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udev_list_entry_foreach(entry, udev_list_get_entry(seclabel_list)) {
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const char *name, *label;
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int r;
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name = udev_list_entry_get_name(entry);
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label = udev_list_entry_get_value(entry);
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if (streq(name, "selinux")) {
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selinux = true;
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r = mac_selinux_apply(devnode, label);
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if (r < 0)
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log_error_errno(r, "SECLABEL: failed to set SELinux label '%s': %m", label);
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else
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log_debug("SECLABEL: set SELinux label '%s'", label);
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} else if (streq(name, "smack")) {
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smack = true;
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r = mac_smack_apply(devnode, SMACK_ATTR_ACCESS, label);
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if (r < 0)
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log_error_errno(r, "SECLABEL: failed to set SMACK label '%s': %m", label);
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else
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log_debug("SECLABEL: set SMACK label '%s'", label);
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} else
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log_error("SECLABEL: unknown subsystem, ignoring '%s'='%s'", name, label);
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}
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/* set the defaults */
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if (!selinux)
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mac_selinux_fix(devnode, true, false);
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if (!smack)
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mac_smack_apply(devnode, SMACK_ATTR_ACCESS, NULL);
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}
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/* always update timestamp when we re-use the node, like on media change events */
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utimensat(AT_FDCWD, devnode, NULL, 0);
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out:
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return err;
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}
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void udev_node_add(struct udev_device *dev, bool apply,
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mode_t mode, uid_t uid, gid_t gid,
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struct udev_list *seclabel_list) {
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char filename[sizeof("/dev/block/:") + 2*DECIMAL_STR_MAX(unsigned)];
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struct udev_list_entry *list_entry;
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log_debug("handling device node '%s', devnum=%s, mode=%#o, uid="UID_FMT", gid="GID_FMT,
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udev_device_get_devnode(dev), udev_device_get_id_filename(dev), mode, uid, gid);
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if (node_permissions_apply(dev, apply, mode, uid, gid, seclabel_list) < 0)
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return;
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/* always add /dev/{block,char}/$major:$minor */
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xsprintf(filename, "/dev/%s/%u:%u",
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streq(udev_device_get_subsystem(dev), "block") ? "block" : "char",
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major(udev_device_get_devnum(dev)),
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minor(udev_device_get_devnum(dev)));
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node_symlink(dev, udev_device_get_devnode(dev), filename);
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/* create/update symlinks, add symlinks to name index */
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udev_list_entry_foreach(list_entry, udev_device_get_devlinks_list_entry(dev))
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link_update(dev, udev_list_entry_get_name(list_entry), true);
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}
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void udev_node_remove(struct udev_device *dev) {
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struct udev_list_entry *list_entry;
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char filename[sizeof("/dev/block/:") + 2*DECIMAL_STR_MAX(unsigned)];
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/* remove/update symlinks, remove symlinks from name index */
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udev_list_entry_foreach(list_entry, udev_device_get_devlinks_list_entry(dev))
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link_update(dev, udev_list_entry_get_name(list_entry), false);
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/* remove /dev/{block,char}/$major:$minor */
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xsprintf(filename, "/dev/%s/%u:%u",
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streq(udev_device_get_subsystem(dev), "block") ? "block" : "char",
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major(udev_device_get_devnum(dev)),
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minor(udev_device_get_devnum(dev)));
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unlink(filename);
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}
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