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/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
* Copyright © 2009 Canonical Ltd.
* Copyright © 2009 Scott James Remnant <scott@netsplit.com>
*/
#include <sys/inotify.h>
#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-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);
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 = 0;
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': %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 = -1;
const char *devnode, *id;
int wd, r;
assert(inotify_fd >= 0);
assert(dev);
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 = -1;
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;
}
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