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src/udev/udev-node.c
791 строка
29 KB
Simon de Vlieger
label: plumb label_context through LabelOps
31 июл 2026, 10:49
31 июл 2026, 10:49
6b0e3ea
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/* SPDX-License-Identifier: GPL-2.0-or-later */ #include <sys/file.h> #include <sys/stat.h> #include <unistd.h> #include "sd-id128.h" #include "alloc-util.h" #include "device-private.h" #include "device-util.h" #include "devnum-util.h" #include "dirent-util.h" #include "errno-util.h" #include "escape.h" #include "fd-util.h" #include "fileio.h" #include "format-util.h" #include "fs-util.h" #include "hashmap.h" #include "hexdecoct.h" #include "label-util.h" #include "mkdir.h" #include "parse-util.h" #include "path-util.h" #include "selinux-util.h" #include "siphash24.h" #include "smack-util.h" #include "string-util.h" #include "strv.h" #include "udev-node.h" #include "user-util.h" #define UDEV_NODE_HASH_KEY SD_ID128_MAKE(b9,6a,f1,ce,40,31,44,1a,9e,19,ec,8b,ae,f3,e3,2f) static int node_remove_symlink(sd_device *dev, const char *slink) { assert(dev); assert(slink); if (unlink(slink) < 0 && errno != ENOENT) return log_device_debug_errno(dev, errno, "Failed to remove '%s': %m", slink); (void) rmdir_parents(slink, "/dev"); return 0; } static int node_create_symlink(sd_device *dev, const char *devnode, const char *slink) { struct stat st; int r; assert(dev); assert(slink); if (!devnode) { r = sd_device_get_devname(dev, &devnode); if (r < 0) return log_device_debug_errno(dev, r, "Failed to get device node: %m"); } if (lstat(slink, &st) >= 0) { if (!S_ISLNK(st.st_mode)) return log_device_debug_errno(dev, SYNTHETIC_ERRNO(EEXIST), "Conflicting inode '%s' found, symlink to '%s' will not be created.", slink, devnode); } else if (errno != ENOENT) return log_device_debug_errno(dev, errno, "Failed to lstat() '%s': %m", slink); r = mkdir_parents_label(slink, 0755); if (r < 0) return log_device_debug_errno(dev, r, "Failed to create parent directory of '%s': %m", slink); /* use relative link */ r = symlinkat_atomic_full(devnode, AT_FDCWD, slink, SYMLINK_MAKE_RELATIVE|SYMLINK_LABEL); if (r < 0) return log_device_debug_errno(dev, r, "Failed to create symlink '%s' to '%s': %m", slink, devnode); log_device_debug(dev, "Successfully created symlink '%s' to '%s'", slink, devnode); return 0; } static int stack_directory_read_one(int dirfd, const char *id, char **devnode, int *priority) { int r; assert(dirfd >= 0); assert(id); assert(priority); /* This reads priority and device node from the symlink under /run/udev/links/ directory. * If 'devnode' is NULL, obtained priority is always set to '*priority'. If 'devnode' is non-NULL, * this updates '*devnode' and '*priority' if the obtained one has a higher priority. */ _cleanup_free_ char *buf = NULL; r = readlinkat_malloc(dirfd, id, &buf); if (r < 0) return r == -ENOENT ? -ENODEV : r; char *colon = strchr(buf, ':'); if (!colon || colon == buf) return -EINVAL; *colon = '\0'; /* Of course, this check is racy, but it is not necessary to be perfect. Even if the device * node will be removed after this check, we will receive 'remove' uevent, and the invalid * symlink will be removed during processing the event. The check is just for shortening the * timespan that the symlink points to a non-existing device node. */ if (access(colon + 1, F_OK) < 0) return -ENODEV; int tmp_prio; r = safe_atoi(buf, &tmp_prio); if (r < 0) return r; if (devnode) { if (*devnode && tmp_prio <= *priority) return 0; /* Unchanged */ r = free_and_strdup(devnode, colon + 1); if (r < 0) return r; } *priority = tmp_prio; return 1; /* Updated */ } static int stack_directory_find_prioritized_devnode(sd_device *dev, int dirfd, bool add, char **ret) { _cleanup_closedir_ DIR *dir = NULL; _cleanup_free_ char *devnode = NULL; int r, priority; const char *id; assert(dev); assert(dirfd >= 0); assert(ret); /* Find device node of device with highest priority. This returns 1 if a device found, 0 if no * device found, or a negative errno on error. */ if (add) { const char *n; r = device_get_devlink_priority(dev, &priority); if (r < 0) return r; r = sd_device_get_devname(dev, &n); if (r < 0) return r; devnode = strdup(n); if (!devnode) return -ENOMEM; } dir = xopendirat(dirfd, /* path= */ NULL, /* flags= */ 0); if (!dir) return -errno; r = sd_device_get_device_id(dev, &id); if (r < 0) return r; FOREACH_DIRENT(de, dir, break) { /* skip ourself */ if (streq(de->d_name, id)) continue; r = stack_directory_read_one(dirfd, de->d_name, &devnode, &priority); if (r < 0 && r != -ENODEV) log_debug_errno(r, "Failed to read '%s', ignoring: %m", de->d_name); } *ret = TAKE_PTR(devnode); return !!*ret; } static int link_search_and_update(sd_device *dev, const char *slink, int dirfd, bool add) { int r; assert(dev); assert(slink); assert(dirfd >= 0); _cleanup_free_ char *devnode = NULL; r = stack_directory_find_prioritized_devnode(dev, dirfd, add, &devnode); if (r < 0) return log_device_debug_errno(dev, r, "Failed to determine device node with the highest priority for '%s': %m", slink); if (r > 0) return node_create_symlink(dev, devnode, slink); log_device_debug(dev, "No reference left for '%s', removing", slink); return node_remove_symlink(dev, slink); } static int stack_directory_update(sd_device *dev, int fd, bool add) { const char *id; int r; assert(dev); assert(fd >= 0); r = sd_device_get_device_id(dev, &id); if (r < 0) return r; if (add) { _cleanup_free_ char *data = NULL, *buf = NULL; const char *devname; int priority; r = sd_device_get_devname(dev, &devname); if (r < 0) return r; r = device_get_devlink_priority(dev, &priority); if (r < 0) return r; if (asprintf(&data, "%i:%s", priority, devname) < 0) return -ENOMEM; if (readlinkat_malloc(fd, id, &buf) >= 0 && streq(buf, data)) return 0; /* Unchanged. */ (void) unlinkat(fd, id, 0); if (symlinkat(data, fd, id) < 0) return -errno; } else { if (unlinkat(fd, id, 0) < 0) { if (errno == ENOENT) return 0; /* Unchanged. */ return -errno; } } return 1; /* Updated. */ } size_t udev_node_escape_path(const char *src, char *dest, size_t size) { size_t i, j; uint64_t h; assert(src); assert(dest); assert(size >= 12); for (i = 0, j = 0; src[i] != '\0'; i++) { if (src[i] == '/') { if (j+4 >= size - 12 + 1) goto toolong; memcpy(&dest[j], "\\x2f", 4); j += 4; } else if (src[i] == '\\') { if (j+4 >= size - 12 + 1) goto toolong; memcpy(&dest[j], "\\x5c", 4); j += 4; } else { if (j+1 >= size - 12 + 1) goto toolong; dest[j] = src[i]; j++; } } dest[j] = '\0'; return j; toolong: /* If the input path is too long to encode as a filename, then let's suffix with a string * generated from the hash of the path. */ h = siphash24_string(src, UDEV_NODE_HASH_KEY.bytes); for (unsigned k = 0; k <= 10; k++) dest[size - k - 2] = urlsafe_base64char((h >> (k * 6)) & 63); dest[size - 1] = '\0'; return size - 1; } static int stack_directory_get_name(const char *slink, char **ret) { _cleanup_free_ char *s = NULL; char name_enc[NAME_MAX+1]; const char *name; int r; assert(slink); assert(ret); r = path_simplify_alloc(slink, &s); if (r < 0) return r; if (!path_is_normalized(s)) return -EINVAL; name = path_startswith(s, "/dev"); if (empty_or_root(name)) return -EINVAL; udev_node_escape_path(name, name_enc, sizeof(name_enc)); return strdup_to(ret, name_enc); } static int stack_directory_open_and_lock( sd_device *dev, const char *slink, char **ret_dirpath, int *ret_dirfd, LockFile *ret_lockfile) { _cleanup_(release_lock_file) LockFile lockfile = LOCK_FILE_INIT; _cleanup_close_ int dirfd = -EBADF; _cleanup_free_ char *name = NULL, *dirpath = NULL, *lockname = NULL; int r; assert(dev); assert(slink); assert(ret_dirpath); assert(ret_dirfd); assert(ret_lockfile); r = stack_directory_get_name(slink, &name); if (r < 0) return log_device_debug_errno(dev, r, "Failed to build stack directory name for '%s': %m", slink); FOREACH_STRING(s, "/run/udev/links/", "/run/udev/links.lock/") { r = mkdir_p(s, 0755); if (r < 0) return log_device_debug_errno(dev, r, "Failed to create '%s': %m", s); } /* 1. Take a lock for the stack directory. */ lockname = path_join("/run/udev/links.lock/", name); if (!lockname) return -ENOMEM; r = make_lock_file(lockname, LOCK_EX, &lockfile); if (r < 0) return log_device_debug_errno(dev, r, "Failed to create and lock '%s': %m", lockname); /* 2. Create and open the stack directory. Do not create the stack directory before taking a lock, * otherwise the directory may be removed by another worker. */ dirpath = path_join("/run/udev/links/", name); if (!dirpath) return -ENOMEM; dirfd = open_mkdir(dirpath, O_CLOEXEC | O_DIRECTORY | O_NOFOLLOW | O_RDONLY, 0755); if (dirfd < 0) return log_device_debug_errno(dev, dirfd, "Failed to open stack directory '%s': %m", dirpath); *ret_dirpath = TAKE_PTR(dirpath); *ret_dirfd = TAKE_FD(dirfd); *ret_lockfile = TAKE_GENERIC(lockfile, LockFile, LOCK_FILE_INIT); return 0; } static int node_get_current(const char *slink, int dirfd, char **ret_id, int *ret_prio) { _cleanup_(sd_device_unrefp) sd_device *dev = NULL; _cleanup_free_ char *id_dup = NULL; const char *id; int r; assert(slink); assert(dirfd >= 0); assert(ret_id); r = sd_device_new_from_devname(&dev, slink); if (r < 0) return r; r = sd_device_get_device_id(dev, &id); if (r < 0) return r; id_dup = strdup(id); if (!id_dup) return -ENOMEM; if (ret_prio) { r = stack_directory_read_one(dirfd, id, NULL, ret_prio); if (r < 0) return r; } *ret_id = TAKE_PTR(id_dup); return 0; } static int link_update(sd_device *dev, const char *slink, bool add) { /* On cleaning up, * 1. close the stack directory, * 2. remove the stack directory if it is empty, * 3. then finally release the lock. * Hence, the variables must be declared in the reverse order. */ _cleanup_(release_lock_file) LockFile lockfile = LOCK_FILE_INIT; /* #3 */ _cleanup_(rmdir_and_freep) char *dirpath = NULL; /* #2 */ _cleanup_close_ int dirfd = -EBADF; /* #1 */ _cleanup_free_ char *current_id = NULL; int r, current_prio; assert(dev); assert(slink); r = stack_directory_open_and_lock(dev, slink, &dirpath, &dirfd, &lockfile); if (r < 0) return r; if (add) { r = node_get_current(slink, dirfd, ¤t_id, ¤t_prio); if (r < 0 && !ERRNO_IS_DEVICE_ABSENT_OR_EMPTY(r)) return log_device_debug_errno(dev, r, "Failed to get the current device node priority for '%s': %m", slink); } r = stack_directory_update(dev, dirfd, add); if (r < 0) return log_device_debug_errno(dev, r, "Failed to update stack directory for '%s': %m", slink); if (!add) { _cleanup_free_ char *target = NULL; /* Especially on 'remove' event, the device ID obtained by node_get_current() may not be * reliable, as the device node and/or device number may be reused. Hence, let's read the * devlink here and if it points to our device node, then we need to update the devlink. If * it points to another device node, then it is already owned by another device, hence we * should not touch it and keep it as is. */ r = readlink_malloc(slink, &target); if (r < 0) { if (r != -ENOENT) log_device_debug_errno(dev, r, "Failed to read symbolic link '%s', ignoring: %m", slink); /* The devlink does not exist. Let's find the most suitable owner, and create the * devlink. This is typically not necessary and does nothing, but for safety in the * case that the devlink is removed manually. */ return link_search_and_update(dev, slink, dirfd, add); } const char *node; r = sd_device_get_devname(dev, &node); if (r < 0) return log_device_debug_errno(dev, r, "Failed to get device node: %m"); if (streq(node, target)) /* owned by us, needs to update. */ return link_search_and_update(dev, slink, dirfd, add); /* The devlink does not point to our device node. For extra safety, let's validate the * current devlink, in case that the devlink is manually modified by user. */ if (!path_startswith(target, "/dev/")) { log_device_debug(dev, "Symbolic link '%s' points to '%s' which is outside of '/dev/', updating it.", slink, target); return link_search_and_update(dev, slink, dirfd, add); } struct stat st; if (lstat(target, &st) < 0) { if (errno != ENOENT) log_device_debug_errno(dev, errno, "Failed to stat '%s', ignoring: %m", target); /* The current target device is also already removed? Let's update. */ return link_search_and_update(dev, slink, dirfd, add); } if (!IN_SET(st.st_mode & S_IFMT, S_IFBLK, S_IFCHR)) { log_device_debug(dev, "Symbolic link '%s' points to '%s' which is not a device node, updating it.", slink, target); return link_search_and_update(dev, slink, dirfd, add); } return 0; /* the devlink is owned by another device, and we should keep it as is. */ } if (!current_id) /* The requested devlink does not exist, or the target device does not exist and the devlink * points to a non-existing device. Let's search the device that has the highest priority, * and update the devlink. */ return link_search_and_update(dev, slink, dirfd, add); const char *id; r = sd_device_get_device_id(dev, &id); if (r < 0) return log_device_debug_errno(dev, r, "Failed to get device id: %m"); int prio; r = device_get_devlink_priority(dev, &prio); if (r < 0) return log_device_debug_errno(dev, r, "Failed to get devlink priority: %m"); if (streq(current_id, id)) { if (current_prio <= prio) /* The devlink is ours and already exists, and the new priority is equal or higher * than the previous. Hence, it is not necessary to recreate it. */ return 0; /* The devlink priority is downgraded. Another device may have a higher priority now. Let's * find the device node with the highest priority. */ return link_search_and_update(dev, slink, dirfd, add); } if (current_prio > prio) /* The devlink with a higher priority already exists and is owned by another device. Hence, * it is not necessary to recreate it. */ return 0; /* This device has the equal or a higher priority than the current. Let's create the devlink to our * device node. */ return node_create_symlink(dev, /* devnode= */ NULL, slink); } static int device_get_devpath_by_devnum(sd_device *dev, char **ret) { dev_t devnum; int r; assert(dev); assert(ret); r = sd_device_get_devnum(dev, &devnum); if (r < 0) return r; r = device_in_subsystem(dev, "block"); if (r < 0) return r; return device_path_make_major_minor(r > 0 ? S_IFBLK : S_IFCHR, devnum, ret); } int udev_node_update(sd_device *dev, sd_device *dev_old) { _cleanup_free_ char *filename = NULL; int r; assert(dev); assert(dev_old); /* update possible left-over symlinks */ FOREACH_DEVICE_DEVLINK(dev_old, devlink) { /* check if old link name still belongs to this device */ if (device_has_devlink(dev, devlink)) continue; log_device_debug(dev, "Removing/updating old device symlink '%s', which is no longer belonging to this device.", devlink); r = link_update(dev, devlink, /* add= */ false); if (r < 0) log_device_warning_errno(dev, r, "Failed to remove/update device symlink '%s', ignoring: %m", devlink); } /* create/update symlinks, add symlinks to name index */ FOREACH_DEVICE_DEVLINK(dev, devlink) { r = link_update(dev, devlink, /* add= */ true); if (r < 0) log_device_warning_errno(dev, r, "Failed to create/update device symlink '%s', ignoring: %m", devlink); } r = device_get_devpath_by_devnum(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 */ r = node_create_symlink(dev, /* devnode= */ NULL, filename); if (r < 0) return log_device_warning_errno(dev, r, "Failed to create device symlink '%s': %m", filename); return 0; } int udev_node_remove(sd_device *dev) { _cleanup_free_ char *filename = NULL; int r; assert(dev); /* remove/update symlinks, remove symlinks from name index */ FOREACH_DEVICE_DEVLINK(dev, devlink) { r = link_update(dev, devlink, /* add= */ false); if (r < 0) log_device_warning_errno(dev, r, "Failed to remove/update device symlink '%s', ignoring: %m", devlink); } r = device_get_devpath_by_devnum(dev, &filename); if (r < 0) return log_device_debug_errno(dev, r, "Failed to get device path: %m"); /* remove /dev/{block,char}/$major:$minor */ return node_remove_symlink(dev, filename); } static int udev_node_apply_permissions_impl( sd_device *dev, /* can be NULL, only used for logging. */ int node_fd, const char *devnode, bool apply_mac, mode_t mode, uid_t uid, gid_t gid, OrderedHashmap *seclabel_list) { bool apply_mode, apply_uid, apply_gid; struct stat stats; int r; assert(node_fd >= 0); assert(devnode); if (fstat(node_fd, &stats) < 0) return log_device_debug_errno(dev, errno, "cannot stat() node %s: %m", devnode); /* If group is set, but mode is not set, "upgrade" mode for the group. */ if (mode == MODE_INVALID && gid_is_valid(gid) && gid > 0) mode = 0660; 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_full(node_fd, NULL, devnode, LABEL_IGNORE_ENOENT, /* label_context= */ NULL); 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 0; } int udev_node_apply_permissions( sd_device *dev, bool apply_mac, mode_t mode, uid_t uid, gid_t gid, OrderedHashmap *seclabel_list) { const char *devnode; _cleanup_close_ int node_fd = -EBADF; 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"); node_fd = sd_device_open(dev, O_PATH|O_CLOEXEC); if (node_fd < 0) { if (ERRNO_IS_DEVICE_ABSENT_OR_EMPTY(node_fd)) { log_device_debug_errno(dev, node_fd, "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, node_fd, "Cannot open node %s: %m", devnode); } return udev_node_apply_permissions_impl(dev, node_fd, devnode, apply_mac, mode, uid, gid, seclabel_list); } int static_node_apply_permissions( const char *name, mode_t mode, uid_t uid, gid_t gid, char **tags) { _cleanup_free_ char *unescaped_filename = NULL; _cleanup_close_ int node_fd = -EBADF; const char *devnode; struct stat stats; int r; assert(name); if (uid == UID_INVALID && gid == GID_INVALID && mode == MODE_INVALID && !tags) return 0; devnode = strjoina("/dev/", name); node_fd = open(devnode, O_PATH|O_CLOEXEC); if (node_fd < 0) { bool ignore = ERRNO_IS_DEVICE_ABSENT_OR_EMPTY(errno); log_full_errno(ignore ? LOG_DEBUG : LOG_WARNING, errno, "Failed to open device node '%s'%s: %m", devnode, ignore ? ", ignoring" : ""); return ignore ? 0 : -errno; } if (fstat(node_fd, &stats) < 0) return log_error_errno(errno, "Failed to stat %s: %m", devnode); if (!S_ISBLK(stats.st_mode) && !S_ISCHR(stats.st_mode)) { log_warning("%s is neither block nor character device, ignoring.", devnode); return 0; } if (!strv_isempty(tags)) { unescaped_filename = xescape(name, "/."); if (!unescaped_filename) return log_oom(); } /* export the tags to a directory as symlinks, allowing otherwise dead nodes to be tagged */ STRV_FOREACH(t, tags) { _cleanup_free_ char *p = NULL; p = path_join("/run/udev/static_node-tags/", *t, unescaped_filename); if (!p) return log_oom(); r = mkdir_parents(p, 0755); if (r < 0) return log_error_errno(r, "Failed to create parent directory for %s: %m", p); r = symlink(devnode, p); if (r < 0 && errno != EEXIST) return log_error_errno(errno, "Failed to create symlink %s -> %s: %m", p, devnode); } return udev_node_apply_permissions_impl(NULL, node_fd, devnode, false, mode, uid, gid, NULL); }