/* SPDX-License-Identifier: GPL-2.0-or-later */ #include #include #include #include #include #include #include "alloc-util.h" #include "device-nodes.h" #include "device-private.h" #include "device-util.h" #include "dirent-util.h" #include "fd-util.h" #include "format-util.h" #include "fs-util.h" #include "libudev-util.h" #include "mkdir.h" #include "path-util.h" #include "selinux-util.h" #include "smack-util.h" #include "stat-util.h" #include "stdio-util.h" #include "string-util.h" #include "strxcpyx.h" #include "udev-node.h" #include "user-util.h" #define LINK_UPDATE_MAX_RETRIES 128 static int node_symlink(sd_device *dev, const char *node, const char *slink) { _cleanup_free_ char *slink_dirname = NULL, *target = NULL; const char *id_filename, *slink_tmp; struct stat stats; int r; assert(dev); assert(node); assert(slink); slink_dirname = dirname_malloc(slink); if (!slink_dirname) return log_oom(); /* use relative link */ r = path_make_relative(slink_dirname, node, &target); if (r < 0) return log_device_error_errno(dev, r, "Failed to get relative path from '%s' to '%s': %m", slink, node); /* 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)) return log_device_error_errno(dev, SYNTHETIC_ERRNO(EOPNOTSUPP), "Conflicting device node '%s' found, link to '%s' will not be created.", slink, node); else if (S_ISLNK(stats.st_mode)) { _cleanup_free_ char *buf = NULL; if (readlink_malloc(slink, &buf) >= 0 && streq(target, buf)) { log_device_debug(dev, "Preserve already existing symlink '%s' to '%s'", slink, target); (void) label_fix(slink, LABEL_IGNORE_ENOENT); (void) utimensat(AT_FDCWD, slink, NULL, AT_SYMLINK_NOFOLLOW); return 0; } } } else { log_device_debug(dev, "Creating symlink '%s' to '%s'", slink, target); do { r = mkdir_parents_label(slink, 0755); if (!IN_SET(r, 0, -ENOENT)) break; mac_selinux_create_file_prepare(slink, S_IFLNK); if (symlink(target, slink) < 0) r = -errno; mac_selinux_create_file_clear(); } while (r == -ENOENT); if (r == 0) return 0; if (r < 0) log_device_debug_errno(dev, r, "Failed to create symlink '%s' to '%s', trying to replace '%s': %m", slink, target, slink); } log_device_debug(dev, "Atomically replace '%s'", slink); r = device_get_id_filename(dev, &id_filename); if (r < 0) return log_device_error_errno(dev, r, "Failed to get id_filename: %m"); slink_tmp = strjoina(slink, ".tmp-", id_filename); (void) unlink(slink_tmp); do { r = mkdir_parents_label(slink_tmp, 0755); if (!IN_SET(r, 0, -ENOENT)) break; mac_selinux_create_file_prepare(slink_tmp, S_IFLNK); if (symlink(target, slink_tmp) < 0) r = -errno; mac_selinux_create_file_clear(); } while (r == -ENOENT); if (r < 0) return log_device_error_errno(dev, r, "Failed to create symlink '%s' to '%s': %m", slink_tmp, target); if (rename(slink_tmp, slink) < 0) { r = log_device_error_errno(dev, errno, "Failed to rename '%s' to '%s': %m", slink_tmp, slink); (void) unlink(slink_tmp); } else /* Tell caller that we replaced already existing symlink. */ r = 1; return r; } /* find device node of device with highest priority */ static int link_find_prioritized(sd_device *dev, bool add, const char *stackdir, char **ret) { _cleanup_closedir_ DIR *dir = NULL; _cleanup_free_ char *target = NULL; struct dirent *dent; int r, priority = 0; assert(!add || dev); assert(stackdir); assert(ret); if (add) { const char *devnode; r = device_get_devlink_priority(dev, &priority); if (r < 0) return r; r = sd_device_get_devname(dev, &devnode); if (r < 0) return r; target = strdup(devnode); if (!target) return -ENOMEM; } dir = opendir(stackdir); if (!dir) { if (target) { *ret = TAKE_PTR(target); return 0; } return -errno; } FOREACH_DIRENT_ALL(dent, dir, break) { _cleanup_(sd_device_unrefp) sd_device *dev_db = NULL; const char *devnode, *id_filename; int db_prio = 0; if (dent->d_name[0] == '\0') break; if (dent->d_name[0] == '.') continue; log_device_debug(dev, "Found '%s' claiming '%s'", dent->d_name, stackdir); if (device_get_id_filename(dev, &id_filename) < 0) continue; /* did we find ourself? */ if (streq(dent->d_name, id_filename)) continue; if (sd_device_new_from_device_id(&dev_db, dent->d_name) < 0) continue; if (sd_device_get_devname(dev_db, &devnode) < 0) continue; if (device_get_devlink_priority(dev_db, &db_prio) < 0) continue; if (target && db_prio <= priority) continue; log_device_debug(dev_db, "Device claims priority %i for '%s'", db_prio, stackdir); r = free_and_strdup(&target, devnode); if (r < 0) return r; priority = db_prio; } if (!target) return -ENOENT; *ret = TAKE_PTR(target); return 0; } /* manage "stack of names" with possibly specified device priorities */ static int link_update(sd_device *dev, const char *slink, bool add) { _cleanup_free_ char *filename = NULL, *dirname = NULL; char name_enc[PATH_MAX]; const char *id_filename; int i, r, retries; assert(dev); assert(slink); r = device_get_id_filename(dev, &id_filename); if (r < 0) return log_device_debug_errno(dev, r, "Failed to get id_filename: %m"); util_path_encode(slink + STRLEN("/dev"), name_enc, sizeof(name_enc)); dirname = path_join("/run/udev/links/", name_enc); if (!dirname) return log_oom(); filename = path_join(dirname, id_filename); if (!filename) return log_oom(); if (!add) { if (unlink(filename) == 0) (void) rmdir(dirname); } else for (;;) { _cleanup_close_ int fd = -1; r = mkdir_parents(filename, 0755); if (!IN_SET(r, 0, -ENOENT)) return r; fd = open(filename, O_WRONLY|O_CREAT|O_CLOEXEC|O_TRUNC|O_NOFOLLOW, 0444); if (fd >= 0) break; if (errno != ENOENT) return -errno; } /* If the database entry is not written yet we will just do one iteration and possibly wrong symlink * will be fixed in the second invocation. */ retries = sd_device_get_is_initialized(dev) > 0 ? LINK_UPDATE_MAX_RETRIES : 1; for (i = 0; i < retries; i++) { _cleanup_free_ char *target = NULL; struct stat st1 = {}, st2 = {}; r = stat(dirname, &st1); if (r < 0 && errno != ENOENT) return -errno; r = link_find_prioritized(dev, add, dirname, &target); if (r == -ENOENT) { log_device_debug(dev, "No reference left, removing '%s'", slink); if (unlink(slink) == 0) (void) rmdir_parents(slink, "/"); break; } else if (r < 0) return log_device_error_errno(dev, r, "Failed to determine highest priority symlink: %m"); r = node_symlink(dev, target, slink); if (r < 0) { (void) unlink(filename); break; } else if (r == 1) /* We have replaced already existing symlink, possibly there is some other device trying * to claim the same symlink. Let's do one more iteration to give us a chance to fix * the error if other device actually claims the symlink with higher priority. */ continue; /* Skip the second stat() if the first failed, stat_inode_unmodified() would return false regardless. */ if ((st1.st_mode & S_IFMT) != 0) { r = stat(dirname, &st2); if (r < 0 && errno != ENOENT) return -errno; if (stat_inode_unmodified(&st1, &st2)) break; } } return i < LINK_UPDATE_MAX_RETRIES ? 0 : -ELOOP; } int udev_node_update_old_links(sd_device *dev, sd_device *dev_old) { const char *name, *devpath; int r; assert(dev); assert(dev_old); r = sd_device_get_devpath(dev, &devpath); if (r < 0) return log_device_debug_errno(dev, r, "Failed to get devpath: %m"); /* update possible left-over symlinks */ FOREACH_DEVICE_DEVLINK(dev_old, name) { const char *name_current; bool found = false; /* check if old link name still belongs to this device */ FOREACH_DEVICE_DEVLINK(dev, name_current) if (streq(name, name_current)) { found = true; break; } if (found) continue; log_device_debug(dev, "Updating old name, '%s' no longer belonging to '%s'", name, devpath); link_update(dev, name, false); } return 0; } static int node_permissions_apply(sd_device *dev, bool apply_mac, mode_t mode, uid_t uid, gid_t gid, OrderedHashmap *seclabel_list) { const char *devnode, *subsystem, *id_filename = NULL; bool apply_mode, apply_uid, apply_gid; _cleanup_close_ int node_fd = -1; struct stat stats; dev_t devnum; int r; assert(dev); r = sd_device_get_devname(dev, &devnode); if (r < 0) return log_device_debug_errno(dev, r, "Failed to get devname: %m"); r = sd_device_get_subsystem(dev, &subsystem); if (r < 0) return log_device_debug_errno(dev, r, "Failed to get subsystem: %m"); r = sd_device_get_devnum(dev, &devnum); if (r < 0) return log_device_debug_errno(dev, r, "Failed to get devnum: %m"); (void) device_get_id_filename(dev, &id_filename); if (streq(subsystem, "block")) mode |= S_IFBLK; else mode |= S_IFCHR; node_fd = open(devnode, O_PATH|O_NOFOLLOW|O_CLOEXEC); if (node_fd < 0) { if (errno == ENOENT) { log_device_debug_errno(dev, errno, "Device node %s is missing, skipping handling.", devnode); return 0; /* This is necessarily racey, so ignore missing the device */ } return log_device_debug_errno(dev, errno, "Cannot open node %s: %m", devnode); } if (fstat(node_fd, &stats) < 0) return log_device_debug_errno(dev, errno, "cannot stat() node %s: %m", devnode); if ((mode != MODE_INVALID && (stats.st_mode & S_IFMT) != (mode & S_IFMT)) || stats.st_rdev != devnum) { log_device_debug(dev, "Found node '%s' with non-matching devnum %s, skipping handling.", devnode, id_filename); return 0; /* We might process a device that already got replaced by the time we have a look * at it, handle this gracefully and step away. */ } apply_mode = mode != MODE_INVALID && (stats.st_mode & 0777) != (mode & 0777); apply_uid = uid_is_valid(uid) && stats.st_uid != uid; apply_gid = gid_is_valid(gid) && stats.st_gid != gid; if (apply_mode || apply_uid || apply_gid || apply_mac) { bool selinux = false, smack = false; const char *name, *label; if (apply_mode || apply_uid || apply_gid) { log_device_debug(dev, "Setting permissions %s, uid=" UID_FMT ", gid=" GID_FMT ", mode=%#o", devnode, uid_is_valid(uid) ? uid : stats.st_uid, gid_is_valid(gid) ? gid : stats.st_gid, mode != MODE_INVALID ? mode & 0777 : stats.st_mode & 0777); r = fchmod_and_chown(node_fd, mode, uid, gid); if (r < 0) log_device_full_errno(dev, r == -ENOENT ? LOG_DEBUG : LOG_ERR, r, "Failed to set owner/mode of %s to uid=" UID_FMT ", gid=" GID_FMT ", mode=%#o: %m", devnode, uid_is_valid(uid) ? uid : stats.st_uid, gid_is_valid(gid) ? gid : stats.st_gid, mode != MODE_INVALID ? mode & 0777 : stats.st_mode & 0777); } else log_device_debug(dev, "Preserve permissions of %s, uid=" UID_FMT ", gid=" GID_FMT ", mode=%#o", devnode, uid_is_valid(uid) ? uid : stats.st_uid, gid_is_valid(gid) ? gid : stats.st_gid, mode != MODE_INVALID ? mode & 0777 : stats.st_mode & 0777); /* apply SECLABEL{$module}=$label */ ORDERED_HASHMAP_FOREACH_KEY(label, name, seclabel_list) { int q; if (streq(name, "selinux")) { selinux = true; q = mac_selinux_apply_fd(node_fd, devnode, label); if (q < 0) log_device_full_errno(dev, q == -ENOENT ? LOG_DEBUG : LOG_ERR, q, "SECLABEL: failed to set SELinux label '%s': %m", label); else log_device_debug(dev, "SECLABEL: set SELinux label '%s'", label); } else if (streq(name, "smack")) { smack = true; q = mac_smack_apply_fd(node_fd, SMACK_ATTR_ACCESS, label); if (q < 0) log_device_full_errno(dev, q == -ENOENT ? LOG_DEBUG : LOG_ERR, q, "SECLABEL: failed to set SMACK label '%s': %m", label); else log_device_debug(dev, "SECLABEL: set SMACK label '%s'", label); } else log_device_error(dev, "SECLABEL: unknown subsystem, ignoring '%s'='%s'", name, label); } /* set the defaults */ if (!selinux) (void) mac_selinux_fix_fd(node_fd, devnode, LABEL_IGNORE_ENOENT); if (!smack) (void) mac_smack_apply_fd(node_fd, SMACK_ATTR_ACCESS, NULL); } /* always update timestamp when we re-use the node, like on media change events */ r = futimens_opath(node_fd, NULL); if (r < 0) log_device_debug_errno(dev, r, "Failed to adjust timestamp of node %s: %m", devnode); return r; } static int xsprintf_dev_num_path_from_sd_device(sd_device *dev, char **ret) { char filename[DEV_NUM_PATH_MAX], *s; const char *subsystem; dev_t devnum; int r; assert(ret); r = sd_device_get_subsystem(dev, &subsystem); if (r < 0) return r; r = sd_device_get_devnum(dev, &devnum); if (r < 0) return r; xsprintf_dev_num_path(filename, streq(subsystem, "block") ? "block" : "char", devnum); s = strdup(filename); if (!s) return -ENOMEM; *ret = s; return 0; } int udev_node_add(sd_device *dev, bool apply, mode_t mode, uid_t uid, gid_t gid, OrderedHashmap *seclabel_list) { const char *devnode, *devlink; _cleanup_free_ char *filename = NULL; int r; assert(dev); r = sd_device_get_devname(dev, &devnode); if (r < 0) return log_device_debug_errno(dev, r, "Failed to get devnode: %m"); if (DEBUG_LOGGING) { const char *id_filename = NULL; (void) device_get_id_filename(dev, &id_filename); log_device_debug(dev, "Handling device node '%s', devnum=%s", devnode, strnull(id_filename)); } r = node_permissions_apply(dev, apply, mode, uid, gid, seclabel_list); if (r < 0) return r; r = xsprintf_dev_num_path_from_sd_device(dev, &filename); if (r < 0) return log_device_debug_errno(dev, r, "Failed to get device path: %m"); /* always add /dev/{block,char}/$major:$minor */ (void) node_symlink(dev, devnode, filename); /* create/update symlinks, add symlinks to name index */ FOREACH_DEVICE_DEVLINK(dev, devlink) { r = link_update(dev, devlink, true); if (r < 0) log_device_info_errno(dev, r, "Failed to update device symlinks: %m"); } return 0; } int udev_node_remove(sd_device *dev) { _cleanup_free_ char *filename = NULL; const char *devlink; int r; assert(dev); /* remove/update symlinks, remove symlinks from name index */ FOREACH_DEVICE_DEVLINK(dev, devlink) { r = link_update(dev, devlink, false); if (r < 0) log_device_info_errno(dev, r, "Failed to update device symlinks: %m"); } r = xsprintf_dev_num_path_from_sd_device(dev, &filename); if (r < 0) return log_device_debug_errno(dev, r, "Failed to get device path: %m"); /* remove /dev/{block,char}/$major:$minor */ (void) unlink(filename); return 0; }