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-rw-r--r--src/udev/udev-watch.c256
1 files changed, 256 insertions, 0 deletions
diff --git a/src/udev/udev-watch.c b/src/udev/udev-watch.c
new file mode 100644
index 0000000..abd1d8f
--- /dev/null
+++ b/src/udev/udev-watch.c
@@ -0,0 +1,256 @@
+/* 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;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-05 20:01:44 +0000