diff options
Diffstat (limited to 'src/udev/udev-node.c')
| -rw-r--r-- | src/udev/udev-node.c | 528 |
1 files changed, 528 insertions, 0 deletions
diff --git a/src/udev/udev-node.c b/src/udev/udev-node.c new file mode 100644 index 0000000..b8b93ee --- /dev/null +++ b/src/udev/udev-node.c @@ -0,0 +1,528 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ + +#include <errno.h> +#include <fcntl.h> +#include <stdbool.h> +#include <stddef.h> +#include <sys/stat.h> +#include <unistd.h> + +#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; +} |