/* SPDX-License-Identifier: GPL-2.0+ */ /* * Copyright (C) 2003-2013 Kay Sievers * * 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 . */ #include #include #include #include #include #include #include #include #include "device-nodes.h" #include "dirent-util.h" #include "format-util.h" #include "fs-util.h" #include "selinux-util.h" #include "smack-util.h" #include "stdio-util.h" #include "string-util.h" #include "udev.h" static int node_symlink(struct udev_device *dev, 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 + 32]; 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 = strpcpy(&s, l, "../"); i++; } l = 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", 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 (streq(target, buf)) { log_debug("preserve already existing symlink '%s' to '%s'", 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'", slink, target); do { err = mkdir_parents_label(slink, 0755); if (!IN_SET(err, 0, -ENOENT)) break; mac_selinux_create_file_prepare(slink, S_IFLNK); err = symlink(target, slink); if (err != 0) err = -errno; mac_selinux_create_file_clear(); } while (err == -ENOENT); if (err == 0) goto exit; } log_debug("atomically replace '%s'", slink); strscpyl(slink_tmp, sizeof(slink_tmp), slink, ".tmp-", udev_device_get_id_filename(dev), NULL); unlink(slink_tmp); do { err = mkdir_parents_label(slink_tmp, 0755); if (!IN_SET(err, 0, -ENOENT)) break; mac_selinux_create_file_prepare(slink_tmp, S_IFLNK); err = symlink(target, slink_tmp); if (err != 0) err = -errno; mac_selinux_create_file_clear(); } while (err == -ENOENT); if (err != 0) { log_error_errno(errno, "symlink '%s' '%s' failed: %m", target, slink_tmp); goto exit; } err = rename(slink_tmp, slink); if (err != 0) { log_error_errno(errno, "rename '%s' '%s' failed: %m", 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; struct dirent *dent; int priority = 0; const char *target = NULL; if (add) { priority = udev_device_get_devlink_priority(dev); strscpy(buf, bufsize, udev_device_get_devnode(dev)); target = buf; } dir = opendir(stackdir); if (dir == NULL) return target; FOREACH_DIRENT_ALL(dent, dir, break) { struct udev_device *dev_db; if (dent->d_name[0] == '\0') break; if (dent->d_name[0] == '.') continue; log_debug("found '%s' claiming '%s'", dent->d_name, stackdir); /* did we find ourself? */ if (streq(dent->d_name, udev_device_get_id_filename(dev))) 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'", udev_device_get_syspath(dev_db), udev_device_get_devlink_priority(dev_db), stackdir); priority = udev_device_get_devlink_priority(dev_db); 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) { 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)); strscpyl(dirname, sizeof(dirname), "/run/udev/links/", name_enc, NULL); 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'", slink); if (unlink(slink) == 0) rmdir_parents(slink, "/"); } else { log_debug("creating link '%s' to '%s'", slink, target); node_symlink(dev, target, slink); } if (add) { int err; do { int fd; err = mkdir_parents(filename, 0755); if (!IN_SET(err, 0, -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 (streq(name, name_current)) { found = 1; break; } } if (found) continue; log_debug("update old name, '%s' no longer belonging to '%s'", name, udev_device_get_devpath(dev)); link_update(dev, name, false); } } static int node_permissions_apply(struct udev_device *dev, bool apply, mode_t mode, uid_t uid, gid_t gid, struct udev_list *seclabel_list) { const char *devnode = udev_device_get_devnode(dev); dev_t devnum = udev_device_get_devnum(dev); struct stat stats; struct udev_list_entry *entry; int err = 0; if (streq(udev_device_get_subsystem(dev), "block")) mode |= S_IFBLK; else mode |= S_IFCHR; if (lstat(devnode, &stats) != 0) { err = log_debug_errno(errno, "can not stat() node '%s' (%m)", 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", udev_device_get_devnode(dev), udev_device_get_id_filename(dev)); goto out; } if (apply) { bool selinux = false; bool smack = false; 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", devnode, mode, uid, gid); err = chmod(devnode, mode); if (err < 0) log_warning_errno(errno, "setting mode of %s to %#o failed: %m", devnode, mode); err = chown(devnode, uid, gid); if (err < 0) log_warning_errno(errno, "setting owner of %s to uid=%u, gid=%u failed: %m", devnode, uid, gid); } else { log_debug("preserve permissions %s, %#o, uid=%u, gid=%u", devnode, mode, uid, gid); } /* apply SECLABEL{$module}=$label */ udev_list_entry_foreach(entry, udev_list_get_entry(seclabel_list)) { const char *name, *label; int r; name = udev_list_entry_get_name(entry); label = udev_list_entry_get_value(entry); if (streq(name, "selinux")) { selinux = true; r = mac_selinux_apply(devnode, label); if (r < 0) log_error_errno(r, "SECLABEL: failed to set SELinux label '%s': %m", label); else log_debug("SECLABEL: set SELinux label '%s'", label); } else if (streq(name, "smack")) { smack = true; r = mac_smack_apply(devnode, SMACK_ATTR_ACCESS, label); if (r < 0) log_error_errno(r, "SECLABEL: failed to set SMACK label '%s': %m", label); else log_debug("SECLABEL: set SMACK label '%s'", label); } else log_error("SECLABEL: unknown subsystem, ignoring '%s'='%s'", name, label); } /* set the defaults */ if (!selinux) mac_selinux_fix(devnode, true, false); if (!smack) mac_smack_apply(devnode, SMACK_ATTR_ACCESS, NULL); } /* 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, bool apply, mode_t mode, uid_t uid, gid_t gid, struct udev_list *seclabel_list) { char filename[DEV_NUM_PATH_MAX]; struct udev_list_entry *list_entry; log_debug("handling device node '%s', devnum=%s, mode=%#o, uid="UID_FMT", gid="GID_FMT, udev_device_get_devnode(dev), udev_device_get_id_filename(dev), mode, uid, gid); if (node_permissions_apply(dev, apply, mode, uid, gid, seclabel_list) < 0) return; /* always add /dev/{block,char}/$major:$minor */ xsprintf_dev_num_path(filename, streq(udev_device_get_subsystem(dev), "block") ? "block" : "char", udev_device_get_devnum(dev)); node_symlink(dev, 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[DEV_NUM_PATH_MAX]; /* 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 */ xsprintf_dev_num_path(filename, streq(udev_device_get_subsystem(dev), "block") ? "block" : "char", udev_device_get_devnum(dev)); unlink(filename); }