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-rw-r--r--src/udev/udev-node.c528
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;
+}
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