/* SPDX-License-Identifier: GPL-2.0-or-later */ /* * Copyright © 2009 Canonical Ltd. * Copyright © 2009 Scott James Remnant */ #include #include "alloc-util.h" #include "device-private.h" #include "device-util.h" #include "dirent-util.h" #include "fd-util.h" #include "fs-util.h" #include "mkdir.h" #include "parse-util.h" #include "rm-rf.h" #include "stdio-util.h" #include "string-util.h" #include "udev-util.h" #include "udev-watch.h" int device_new_from_watch_handle_at(sd_device **ret, int dirfd, int wd) { char path_wd[STRLEN("/run/udev/watch/") + DECIMAL_STR_MAX(int)]; _cleanup_free_ char *id = NULL; int r; assert(ret); if (wd < 0) return -EBADF; if (dirfd >= 0) { xsprintf(path_wd, "%d", wd); r = readlinkat_malloc(dirfd, path_wd, &id); } else { xsprintf(path_wd, "/run/udev/watch/%d", wd); r = readlink_malloc(path_wd, &id); } if (r < 0) return r; return sd_device_new_from_device_id(ret, id); } int udev_watch_restore(int inotify_fd) { _cleanup_closedir_ DIR *dir = NULL; int r; /* Move any old watches directory out of the way, and then restore the watches. */ assert(inotify_fd >= 0); (void) rm_rf("/run/udev/watch.old", REMOVE_ROOT); if (rename("/run/udev/watch", "/run/udev/watch.old") < 0) { if (errno == ENOENT) return 0; r = log_warning_errno(errno, "Failed to move watches directory '/run/udev/watch/'. " "Old watches will not be restored: %m"); goto finalize; } dir = opendir("/run/udev/watch.old"); if (!dir) { r = log_warning_errno(errno, "Failed to open old watches directory '/run/udev/watch.old/'. " "Old watches will not be restored: %m"); goto finalize; } FOREACH_DIRENT_ALL(de, dir, break) { _cleanup_(sd_device_unrefp) sd_device *dev = NULL; int wd; /* For backward compatibility, read symlink from watch handle to device ID. This is necessary * when udevd is restarted after upgrading from v248 or older. The new format (ID -> wd) was * introduced by e7f781e473f5119bf9246208a6de9f6b76a39c5d (v249). */ if (dot_or_dot_dot(de->d_name)) continue; if (safe_atoi(de->d_name, &wd) < 0) continue; r = device_new_from_watch_handle_at(&dev, dirfd(dir), wd); if (r < 0) { log_full_errno(r == -ENODEV ? LOG_DEBUG : LOG_WARNING, r, "Failed to create sd_device object from saved watch handle '%i', ignoring: %m", wd); continue; } (void) udev_watch_begin(inotify_fd, dev); } r = 0; finalize: (void) rm_rf("/run/udev/watch.old", REMOVE_ROOT); return r; } static int udev_watch_clear(sd_device *dev, int dirfd, int *ret_wd) { _cleanup_free_ char *wd_str = NULL, *buf = NULL; const char *id; int wd = -1, r; assert(dev); assert(dirfd >= 0); r = device_get_device_id(dev, &id); if (r < 0) return log_device_debug_errno(dev, r, "Failed to get device ID: %m"); /* 1. read symlink ID -> wd */ r = readlinkat_malloc(dirfd, id, &wd_str); if (r == -ENOENT) { if (ret_wd) *ret_wd = -1; return 0; } if (r < 0) { log_device_debug_errno(dev, r, "Failed to read symlink '/run/udev/watch/%s': %m", id); goto finalize; } r = safe_atoi(wd_str, &wd); if (r < 0) { log_device_debug_errno(dev, r, "Failed to parse watch handle from symlink '/run/udev/watch/%s': %m", id); goto finalize; } if (wd < 0) { r = log_device_debug_errno(dev, SYNTHETIC_ERRNO(EBADF), "Invalid watch handle %i.", wd); goto finalize; } /* 2. read symlink wd -> ID */ r = readlinkat_malloc(dirfd, wd_str, &buf); if (r < 0) { log_device_debug_errno(dev, r, "Failed to read symlink '/run/udev/watch/%s': %m", wd_str); goto finalize; } /* 3. check if the symlink wd -> ID is owned by the device. */ if (!streq(buf, id)) { r = log_device_debug_errno(dev, SYNTHETIC_ERRNO(ENOENT), "Symlink '/run/udev/watch/%s' is owned by another device '%s'.", wd_str, buf); goto finalize; } /* 4. remove symlink wd -> ID. * In the above, we already confirmed that the symlink is owned by us. Hence, no other workers remove * the symlink and cannot create a new symlink with the same filename but to a different ID. Hence, * the removal below is safe even the steps in this function are not atomic. */ if (unlinkat(dirfd, wd_str, 0) < 0 && errno != ENOENT) log_device_debug_errno(dev, errno, "Failed to remove '/run/udev/watch/%s', ignoring: %m", wd_str); if (ret_wd) *ret_wd = wd; r = 1; finalize: /* 5. remove symlink ID -> wd. * The file is always owned by the device. Hence, it is safe to remove it unconditionally. */ if (unlinkat(dirfd, id, 0) < 0 && errno != ENOENT) log_device_debug_errno(dev, errno, "Failed to remove '/run/udev/watch/%s', ignoring: %m", id); return r; } int udev_watch_begin(int inotify_fd, sd_device *dev) { char wd_str[DECIMAL_STR_MAX(int)]; _cleanup_close_ int dirfd = -EBADF; const char *devnode, *id; int wd, r; assert(inotify_fd >= 0); assert(dev); /* Ignore the request of watching the device node on remove event, as the device node specified by * DEVNAME= has already been removed, and may already be assigned to another device. Consider the * case e.g. a USB stick memory was unplugged and then another one is plugged. */ if (device_for_action(dev, SD_DEVICE_REMOVE)) return 0; r = sd_device_get_devname(dev, &devnode); if (r < 0) return log_device_debug_errno(dev, r, "Failed to get device node: %m"); r = device_get_device_id(dev, &id); if (r < 0) return log_device_debug_errno(dev, r, "Failed to get device ID: %m"); r = dirfd = open_mkdir_at(AT_FDCWD, "/run/udev/watch", O_CLOEXEC | O_RDONLY, 0755); if (r < 0) return log_device_debug_errno(dev, r, "Failed to create and open '/run/udev/watch/': %m"); /* 1. Clear old symlinks */ (void) udev_watch_clear(dev, dirfd, NULL); /* 2. Add inotify watch */ log_device_debug(dev, "Adding watch on '%s'", devnode); wd = inotify_add_watch(inotify_fd, devnode, IN_CLOSE_WRITE); if (wd < 0) return log_device_debug_errno(dev, errno, "Failed to watch device node '%s': %m", devnode); xsprintf(wd_str, "%d", wd); /* 3. Create new symlinks */ if (symlinkat(wd_str, dirfd, id) < 0) { r = log_device_debug_errno(dev, errno, "Failed to create symlink '/run/udev/watch/%s' to '%s': %m", id, wd_str); goto on_failure; } if (symlinkat(id, dirfd, wd_str) < 0) { /* Possibly, the watch handle is previously assigned to another device, and udev_watch_end() * is not called for the device yet. */ r = log_device_debug_errno(dev, errno, "Failed to create symlink '/run/udev/watch/%s' to '%s': %m", wd_str, id); goto on_failure; } return 0; on_failure: (void) unlinkat(dirfd, id, 0); (void) inotify_rm_watch(inotify_fd, wd); return r; } int udev_watch_end(int inotify_fd, sd_device *dev) { _cleanup_close_ int dirfd = -EBADF; int wd, r; assert(dev); /* This may be called by 'udevadm test'. In that case, inotify_fd is not initialized. */ if (inotify_fd < 0) return 0; if (sd_device_get_devname(dev, NULL) < 0) return 0; dirfd = RET_NERRNO(open("/run/udev/watch", O_CLOEXEC | O_DIRECTORY | O_NOFOLLOW | O_RDONLY)); if (dirfd == -ENOENT) return 0; if (dirfd < 0) return log_device_debug_errno(dev, dirfd, "Failed to open '/run/udev/watch/': %m"); /* First, clear symlinks. */ r = udev_watch_clear(dev, dirfd, &wd); if (r <= 0) return r; /* Then, remove inotify watch. */ log_device_debug(dev, "Removing watch handle %i.", wd); (void) inotify_rm_watch(inotify_fd, wd); return 0; }