text: #include <linux/fanotify.h>
  #include <linux/fcntl.h>
  #include <linux/file.h>
  #include <linux/fs.h>
  #include <linux/anon_inodes.h>
  #include <linux/fsnotify_backend.h>
  #include <linux/init.h>
  #include <linux/mount.h>
  #include <linux/namei.h>
  #include <linux/poll.h>
  #include <linux/security.h>
  #include <linux/syscalls.h>
  #include <linux/slab.h>
  #include <linux/types.h>
  #include <linux/uaccess.h>
  
  #include <asm/ioctls.h>
  
  #include "../../mount.h"
  
  #define FANOTIFY_DEFAULT_MAX_EVENTS	16384
  #define FANOTIFY_DEFAULT_MAX_MARKS	8192
  #define FANOTIFY_DEFAULT_MAX_LISTENERS	128
  
  extern const struct fsnotify_ops fanotify_fsnotify_ops;
  
  static struct kmem_cache *fanotify_mark_cache __read_mostly;
  static struct kmem_cache *fanotify_response_event_cache __read_mostly;
  
  struct fanotify_response_event {
  	struct list_head list;
  	__s32 fd;
  	struct fsnotify_event *event;
  };
  
  /*
   * Get an fsnotify notification event if one exists and is small
   * enough to fit in "count". Return an error pointer if the count
   * is not large enough.
   *
   * Called with the group->notification_mutex held.
   */
  static struct fsnotify_event *get_one_event(struct fsnotify_group *group,
  					    size_t count)
  {
  	BUG_ON(!mutex_is_locked(&group->notification_mutex));
  
  	pr_debug("%s: group=%p count=%zd\n", __func__, group, count);
  
  	if (fsnotify_notify_queue_is_empty(group))
  		return NULL;
  
  	if (FAN_EVENT_METADATA_LEN > count)
  		return ERR_PTR(-EINVAL);
  
  	/* held the notification_mutex the whole time, so this is the
  	 * same event we peeked above */
  	return fsnotify_remove_notify_event(group);
  }
  
  static int create_fd(struct fsnotify_group *group, struct fsnotify_event *event)
  {
  	int client_fd;
  	struct dentry *dentry;
  	struct vfsmount *mnt;
  	struct file *new_file;
  
  	pr_debug("%s: group=%p event=%p\n", __func__, group, event);
  
  	client_fd = get_unused_fd();
  	if (client_fd < 0)
  		return client_fd;
  
  	if (event->data_type != FSNOTIFY_EVENT_PATH) {
  		WARN_ON(1);
  		put_unused_fd(client_fd);
  		return -EINVAL;
  	}
  
  	/*
  	 * we need a new file handle for the userspace program so it can read even if it was
  	 * originally opened O_WRONLY.
  	 */
  	dentry = dget(event->path.dentry);
  	mnt = mntget(event->path.mnt);
  	/* it's possible this event was an overflow event.  in that case dentry and mnt
  	 * are NULL;  That's fine, just don't call dentry open */
  	if (dentry && mnt)
  		new_file = dentry_open(dentry, mnt,
  				       group->fanotify_data.f_flags | FMODE_NONOTIFY,
  				       current_cred());
  	else
  		new_file = ERR_PTR(-EOVERFLOW);
  	if (IS_ERR(new_file)) {
  		/*
  		 * we still send an event even if we can't open the file.  this
  		 * can happen when say tasks are gone and we try to open their
  		 * /proc files or we try to open a WRONLY file like in sysfs
  		 * we just send the errno to userspace since there isn't much
  		 * else we can do.
  		 */
  		put_unused_fd(client_fd);
  		client_fd = PTR_ERR(new_file);
  	} else {
  		fd_install(client_fd, new_file);
  	}
  
  	return client_fd;
  }
  
  static int fill_event_metadata(struct fsnotify_group *group,
  				   struct fanotify_event_metadata *metadata,
  				   struct fsnotify_event *event)
  {
  	int ret = 0;
  
  	pr_debug("%s: group=%p metadata=%p event=%p\n", __func__,
  		 group, metadata, event);
  
  	metadata->event_len = FAN_EVENT_METADATA_LEN;
  	metadata->metadata_len = FAN_EVENT_METADATA_LEN;
  	metadata->vers = FANOTIFY_METADATA_VERSION;
  	metadata->mask = event->mask & FAN_ALL_OUTGOING_EVENTS;
  	metadata->pid = pid_vnr(event->tgid);
  	if (unlikely(event->mask & FAN_Q_OVERFLOW))
  		metadata->fd = FAN_NOFD;
  	else {
  		metadata->fd = create_fd(group, event);
  		if (metadata->fd < 0)
  			ret = metadata->fd;
  	}
  
  	return ret;
  }
  
  #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
  static struct fanotify_response_event *dequeue_re(struct fsnotify_group *group,
  						  __s32 fd)
  {
  	struct fanotify_response_event *re, *return_re = NULL;
  
  	mutex_lock(&group->fanotify_data.access_mutex);
  	list_for_each_entry(re, &group->fanotify_data.access_list, list) {
  		if (re->fd != fd)
  			continue;
  
  		list_del_init(&re->list);
  		return_re = re;
  		break;
  	}
  	mutex_unlock(&group->fanotify_data.access_mutex);
  
  	pr_debug("%s: found return_re=%p\n", __func__, return_re);
  
  	return return_re;
  }
  
  static int process_access_response(struct fsnotify_group *group,
  				   struct fanotify_response *response_struct)
  {
  	struct fanotify_response_event *re;
  	__s32 fd = response_struct->fd;
  	__u32 response = response_struct->response;
  
  	pr_debug("%s: group=%p fd=%d response=%d\n", __func__, group,
  		 fd, response);
  	/*
  	 * make sure the response is valid, if invalid we do nothing and either
  	 * userspace can send a valid response or we will clean it up after the
  	 * timeout
  	 */
  	switch (response) {
  	case FAN_ALLOW:
  	case FAN_DENY:
  		break;
  	default:
  		return -EINVAL;
  	}
  
  	if (fd < 0)
  		return -EINVAL;
  
  	re = dequeue_re(group, fd);
  	if (!re)
  		return -ENOENT;
  
  	re->event->response = response;
  
  	wake_up(&group->fanotify_data.access_waitq);
  
  	kmem_cache_free(fanotify_response_event_cache, re);
  
  	return 0;
  }
  
  static int prepare_for_access_response(struct fsnotify_group *group,
  				       struct fsnotify_event *event,
  				       __s32 fd)
  {
  	struct fanotify_response_event *re;
  
  	if (!(event->mask & FAN_ALL_PERM_EVENTS))
  		return 0;
  
  	re = kmem_cache_alloc(fanotify_response_event_cache, GFP_KERNEL);
  	if (!re)
  		return -ENOMEM;
  
  	re->event = event;
  	re->fd = fd;
  
  	mutex_lock(&group->fanotify_data.access_mutex);
  
  	if (atomic_read(&group->fanotify_data.bypass_perm)) {
  		mutex_unlock(&group->fanotify_data.access_mutex);
  		kmem_cache_free(fanotify_response_event_cache, re);
  		event->response = FAN_ALLOW;
  		return 0;
  	}
  		
  	list_add_tail(&re->list, &group->fanotify_data.access_list);
  	mutex_unlock(&group->fanotify_data.access_mutex);
  
  	return 0;
  }
  
  static void remove_access_response(struct fsnotify_group *group,
  				   struct fsnotify_event *event,
  				   __s32 fd)
  {
  	struct fanotify_response_event *re;
  
  	if (!(event->mask & FAN_ALL_PERM_EVENTS))
  		return;
  
  	re = dequeue_re(group, fd);
  	if (!re)
  		return;
  
  	BUG_ON(re->event != event);
  
  	kmem_cache_free(fanotify_response_event_cache, re);
  
  	return;
  }
  #else
  static int prepare_for_access_response(struct fsnotify_group *group,
  				       struct fsnotify_event *event,
  				       __s32 fd)
  {
  	return 0;
  }
  
  static void remove_access_response(struct fsnotify_group *group,
  				   struct fsnotify_event *event,
  				   __s32 fd)
  {
  	return;
  }
  #endif
  
  static ssize_t copy_event_to_user(struct fsnotify_group *group,
  				  struct fsnotify_event *event,
  				  char __user *buf)
  {
  	struct fanotify_event_metadata fanotify_event_metadata;
  	int fd, ret;
  
  	pr_debug("%s: group=%p event=%p\n", __func__, group, event);
  
  	ret = fill_event_metadata(group, &fanotify_event_metadata, event);
  	if (ret < 0)
  		goto out;
  
  	fd = fanotify_event_metadata.fd;
  	ret = prepare_for_access_response(group, event, fd);
  	if (ret)
  		goto out_close_fd;
  
  	ret = -EFAULT;
  	if (copy_to_user(buf, &fanotify_event_metadata,
  			 fanotify_event_metadata.event_len))
  		goto out_kill_access_response;
  
  	return fanotify_event_metadata.event_len;
  
  out_kill_access_response:
  	remove_access_response(group, event, fd);
  out_close_fd:
  	if (fd != FAN_NOFD)
  		sys_close(fd);
  out:
  #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
  	if (event->mask & FAN_ALL_PERM_EVENTS) {
  		event->response = FAN_DENY;
  		wake_up(&group->fanotify_data.access_waitq);
  	}
  #endif
  	return ret;
  }
  
  /* intofiy userspace file descriptor functions */
  static unsigned int fanotify_poll(struct file *file, poll_table *wait)
  {
  	struct fsnotify_group *group = file->private_data;
  	int ret = 0;
  
  	poll_wait(file, &group->notification_waitq, wait);
  	mutex_lock(&group->notification_mutex);
  	if (!fsnotify_notify_queue_is_empty(group))
  		ret = POLLIN | POLLRDNORM;
  	mutex_unlock(&group->notification_mutex);
  
  	return ret;
  }
  
  static ssize_t fanotify_read(struct file *file, char __user *buf,
  			     size_t count, loff_t *pos)
  {
  	struct fsnotify_group *group;
  	struct fsnotify_event *kevent;
  	char __user *start;
  	int ret;
  	DEFINE_WAIT(wait);
  
  	start = buf;
  	group = file->private_data;
  
  	pr_debug("%s: group=%p\n", __func__, group);
  
  	while (1) {
  		prepare_to_wait(&group->notification_waitq, &wait, TASK_INTERRUPTIBLE);
  
  		mutex_lock(&group->notification_mutex);
  		kevent = get_one_event(group, count);
  		mutex_unlock(&group->notification_mutex);
  
  		if (kevent) {
  			ret = PTR_ERR(kevent);
  			if (IS_ERR(kevent))
  				break;
  			ret = copy_event_to_user(group, kevent, buf);
  			fsnotify_put_event(kevent);
  			if (ret < 0)
  				break;
  			buf += ret;
  			count -= ret;
  			continue;
  		}
  
  		ret = -EAGAIN;
  		if (file->f_flags & O_NONBLOCK)
  			break;
  		ret = -ERESTARTSYS;
  		if (signal_pending(current))
  			break;
  
  		if (start != buf)
  			break;
  
  		schedule();
  	}
  
  	finish_wait(&group->notification_waitq, &wait);
  	if (start != buf && ret != -EFAULT)
  		ret = buf - start;
  	return ret;
  }
  
  static ssize_t fanotify_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
  {
  #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
  	struct fanotify_response response = { .fd = -1, .response = -1 };
  	struct fsnotify_group *group;
  	int ret;
  
  	group = file->private_data;
  
  	if (count > sizeof(response))
  		count = sizeof(response);
  
  	pr_debug("%s: group=%p count=%zu\n", __func__, group, count);
  
  	if (copy_from_user(&response, buf, count))
  		return -EFAULT;
  
  	ret = process_access_response(group, &response);
  	if (ret < 0)
  		count = ret;
  
  	return count;
  #else
  	return -EINVAL;
  #endif
  }
  
  static int fanotify_release(struct inode *ignored, struct file *file)
  {
  	struct fsnotify_group *group = file->private_data;
  
  #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
  	struct fanotify_response_event *re, *lre;
  
  	mutex_lock(&group->fanotify_data.access_mutex);
  
  	atomic_inc(&group->fanotify_data.bypass_perm);
  
  	list_for_each_entry_safe(re, lre, &group->fanotify_data.access_list, list) {
  		pr_debug("%s: found group=%p re=%p event=%p\n", __func__, group,
  			 re, re->event);
  
  		list_del_init(&re->list);
  		re->event->response = FAN_ALLOW;
  
  		kmem_cache_free(fanotify_response_event_cache, re);
  	}
  	mutex_unlock(&group->fanotify_data.access_mutex);
  
  	wake_up(&group->fanotify_data.access_waitq);
  #endif
  	/* matches the fanotify_init->fsnotify_alloc_group */
  	fsnotify_put_group(group);
  
  	return 0;
  }
  
  static long fanotify_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
  {
  	struct fsnotify_group *group;
  	struct fsnotify_event_holder *holder;
  	void __user *p;
  	int ret = -ENOTTY;
  	size_t send_len = 0;
  
  	group = file->private_data;
  
  	p = (void __user *) arg;
  
  	switch (cmd) {
  	case FIONREAD:
  		mutex_lock(&group->notification_mutex);
  		list_for_each_entry(holder, &group->notification_list, event_list)
  			send_len += FAN_EVENT_METADATA_LEN;
  		mutex_unlock(&group->notification_mutex);
  		ret = put_user(send_len, (int __user *) p);
  		break;
  	}
  
  	return ret;
  }
  
  static const struct file_operations fanotify_fops = {
  	.poll		= fanotify_poll,
  	.read		= fanotify_read,
  	.write		= fanotify_write,
  	.fasync		= NULL,
  	.release	= fanotify_release,
  	.unlocked_ioctl	= fanotify_ioctl,
  	.compat_ioctl	= fanotify_ioctl,
  	.llseek		= noop_llseek,
  };
  
  static void fanotify_free_mark(struct fsnotify_mark *fsn_mark)
  {
  	kmem_cache_free(fanotify_mark_cache, fsn_mark);
  }
  
  static int fanotify_find_path(int dfd, const char __user *filename,
  			      struct path *path, unsigned int flags)
  {
  	int ret;
  
  	pr_debug("%s: dfd=%d filename=%p flags=%x\n", __func__,
  		 dfd, filename, flags);
  
  	if (filename == NULL) {
  		struct file *file;
  		int fput_needed;
  
  		ret = -EBADF;
  		file = fget_light(dfd, &fput_needed);
  		if (!file)
  			goto out;
  
  		ret = -ENOTDIR;
  		if ((flags & FAN_MARK_ONLYDIR) &&
  		    !(S_ISDIR(file->f_path.dentry->d_inode->i_mode))) {
  			fput_light(file, fput_needed);
  			goto out;
  		}
  
  		*path = file->f_path;
  		path_get(path);
  		fput_light(file, fput_needed);
  	} else {
  		unsigned int lookup_flags = 0;
  
  		if (!(flags & FAN_MARK_DONT_FOLLOW))
  			lookup_flags |= LOOKUP_FOLLOW;
  		if (flags & FAN_MARK_ONLYDIR)
  			lookup_flags |= LOOKUP_DIRECTORY;
  
  		ret = user_path_at(dfd, filename, lookup_flags, path);
  		if (ret)
  			goto out;
  	}
  
  	/* you can only watch an inode if you have read permissions on it */
  	ret = inode_permission(path->dentry->d_inode, MAY_READ);
  	if (ret)
  		path_put(path);
  out:
  	return ret;
  }
  
  static __u32 fanotify_mark_remove_from_mask(struct fsnotify_mark *fsn_mark,
  					    __u32 mask,
  					    unsigned int flags)
  {
  	__u32 oldmask;
  
  	spin_lock(&fsn_mark->lock);
  	if (!(flags & FAN_MARK_IGNORED_MASK)) {
  		oldmask = fsn_mark->mask;
  		fsnotify_set_mark_mask_locked(fsn_mark, (oldmask & ~mask));
  	} else {
  		oldmask = fsn_mark->ignored_mask;
  		fsnotify_set_mark_ignored_mask_locked(fsn_mark, (oldmask & ~mask));
  	}
  	spin_unlock(&fsn_mark->lock);
  
  	if (!(oldmask & ~mask))
  		fsnotify_destroy_mark(fsn_mark);
  
  	return mask & oldmask;
  }
  
  static int fanotify_remove_vfsmount_mark(struct fsnotify_group *group,
  					 struct vfsmount *mnt, __u32 mask,
  					 unsigned int flags)
  {
  	struct fsnotify_mark *fsn_mark = NULL;
  	__u32 removed;
  
  	fsn_mark = fsnotify_find_vfsmount_mark(group, mnt);
  	if (!fsn_mark)
  		return -ENOENT;
  
  	removed = fanotify_mark_remove_from_mask(fsn_mark, mask, flags);
  	fsnotify_put_mark(fsn_mark);
  	if (removed & real_mount(mnt)->mnt_fsnotify_mask)
  		fsnotify_recalc_vfsmount_mask(mnt);
  
  	return 0;
  }
  
  static int fanotify_remove_inode_mark(struct fsnotify_group *group,
  				      struct inode *inode, __u32 mask,
  				      unsigned int flags)
  {
  	struct fsnotify_mark *fsn_mark = NULL;
  	__u32 removed;
  
  	fsn_mark = fsnotify_find_inode_mark(group, inode);
  	if (!fsn_mark)
  		return -ENOENT;
  
  	removed = fanotify_mark_remove_from_mask(fsn_mark, mask, flags);
  	/* matches the fsnotify_find_inode_mark() */
  	fsnotify_put_mark(fsn_mark);
  	if (removed & inode->i_fsnotify_mask)
  		fsnotify_recalc_inode_mask(inode);
  
  	return 0;
  }
  
  static __u32 fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark,
  				       __u32 mask,
  				       unsigned int flags)
  {
  	__u32 oldmask = -1;
  
  	spin_lock(&fsn_mark->lock);
  	if (!(flags & FAN_MARK_IGNORED_MASK)) {
  		oldmask = fsn_mark->mask;
  		fsnotify_set_mark_mask_locked(fsn_mark, (oldmask | mask));
  	} else {
  		__u32 tmask = fsn_mark->ignored_mask | mask;
  		fsnotify_set_mark_ignored_mask_locked(fsn_mark, tmask);
  		if (flags & FAN_MARK_IGNORED_SURV_MODIFY)
  			fsn_mark->flags |= FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY;
  	}
  
  	if (!(flags & FAN_MARK_ONDIR)) {
  		__u32 tmask = fsn_mark->ignored_mask | FAN_ONDIR;
  		fsnotify_set_mark_ignored_mask_locked(fsn_mark, tmask);
  	}
  
  	spin_unlock(&fsn_mark->lock);
  
  	return mask & ~oldmask;
  }
  
  static int fanotify_add_vfsmount_mark(struct fsnotify_group *group,
  				      struct vfsmount *mnt, __u32 mask,
  				      unsigned int flags)
  {
  	struct fsnotify_mark *fsn_mark;
  	__u32 added;
  	int ret = 0;
  
  	fsn_mark = fsnotify_find_vfsmount_mark(group, mnt);
  	if (!fsn_mark) {
  		if (atomic_read(&group->num_marks) > group->fanotify_data.max_marks)
  			return -ENOSPC;
  
  		fsn_mark = kmem_cache_alloc(fanotify_mark_cache, GFP_KERNEL);
  		if (!fsn_mark)
  			return -ENOMEM;
  
  		fsnotify_init_mark(fsn_mark, fanotify_free_mark);
  		ret = fsnotify_add_mark(fsn_mark, group, NULL, mnt, 0);
  		if (ret)
  			goto err;
  	}
  	added = fanotify_mark_add_to_mask(fsn_mark, mask, flags);
  
  	if (added & ~real_mount(mnt)->mnt_fsnotify_mask)
  		fsnotify_recalc_vfsmount_mask(mnt);
  err:
  	fsnotify_put_mark(fsn_mark);
  	return ret;
  }
  
  static int fanotify_add_inode_mark(struct fsnotify_group *group,
  				   struct inode *inode, __u32 mask,
  				   unsigned int flags)
  {
  	struct fsnotify_mark *fsn_mark;
  	__u32 added;
  	int ret = 0;
  
  	pr_debug("%s: group=%p inode=%p\n", __func__, group, inode);
  
  	/*
  	 * If some other task has this inode open for write we should not add
  	 * an ignored mark, unless that ignored mark is supposed to survive
  	 * modification changes anyway.
  	 */
  	if ((flags & FAN_MARK_IGNORED_MASK) &&
  	    !(flags & FAN_MARK_IGNORED_SURV_MODIFY) &&
  	    (atomic_read(&inode->i_writecount) > 0))
  		return 0;
  
  	fsn_mark = fsnotify_find_inode_mark(group, inode);
  	if (!fsn_mark) {
  		if (atomic_read(&group->num_marks) > group->fanotify_data.max_marks)
  			return -ENOSPC;
  
  		fsn_mark = kmem_cache_alloc(fanotify_mark_cache, GFP_KERNEL);
  		if (!fsn_mark)
  			return -ENOMEM;
  
  		fsnotify_init_mark(fsn_mark, fanotify_free_mark);
  		ret = fsnotify_add_mark(fsn_mark, group, inode, NULL, 0);
  		if (ret)
  			goto err;
  	}
  	added = fanotify_mark_add_to_mask(fsn_mark, mask, flags);
  
  	if (added & ~inode->i_fsnotify_mask)
  		fsnotify_recalc_inode_mask(inode);
  err:
  	fsnotify_put_mark(fsn_mark);
  	return ret;
  }
  
  /* fanotify syscalls */
  SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
  {
  	struct fsnotify_group *group;
  	int f_flags, fd;
  	struct user_struct *user;
  
  	pr_debug("%s: flags=%d event_f_flags=%d\n",
  		__func__, flags, event_f_flags);
  
  	if (!capable(CAP_SYS_ADMIN))
  		return -EPERM;
  
  	if (flags & ~FAN_ALL_INIT_FLAGS)
  		return -EINVAL;
  
  	user = get_current_user();
  	if (atomic_read(&user->fanotify_listeners) > FANOTIFY_DEFAULT_MAX_LISTENERS) {
  		free_uid(user);
  		return -EMFILE;
  	}
  
  	f_flags = O_RDWR | FMODE_NONOTIFY;
  	if (flags & FAN_CLOEXEC)
  		f_flags |= O_CLOEXEC;
  	if (flags & FAN_NONBLOCK)
  		f_flags |= O_NONBLOCK;
  
  	/* fsnotify_alloc_group takes a ref.  Dropped in fanotify_release */
  	group = fsnotify_alloc_group(&fanotify_fsnotify_ops);
  	if (IS_ERR(group)) {
  		free_uid(user);
  		return PTR_ERR(group);
  	}
  
  	group->fanotify_data.user = user;
  	atomic_inc(&user->fanotify_listeners);
  
  	group->fanotify_data.f_flags = event_f_flags;
  #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
  	mutex_init(&group->fanotify_data.access_mutex);
  	init_waitqueue_head(&group->fanotify_data.access_waitq);
  	INIT_LIST_HEAD(&group->fanotify_data.access_list);
  	atomic_set(&group->fanotify_data.bypass_perm, 0);
  #endif
  	switch (flags & FAN_ALL_CLASS_BITS) {
  	case FAN_CLASS_NOTIF:
  		group->priority = FS_PRIO_0;
  		break;
  	case FAN_CLASS_CONTENT:
  		group->priority = FS_PRIO_1;
  		break;
  	case FAN_CLASS_PRE_CONTENT:
  		group->priority = FS_PRIO_2;
  		break;
  	default:
  		fd = -EINVAL;
  		goto out_put_group;
  	}
  
  	if (flags & FAN_UNLIMITED_QUEUE) {
  		fd = -EPERM;
  		if (!capable(CAP_SYS_ADMIN))
  			goto out_put_group;
  		group->max_events = UINT_MAX;
  	} else {
  		group->max_events = FANOTIFY_DEFAULT_MAX_EVENTS;
  	}
  
  	if (flags & FAN_UNLIMITED_MARKS) {
  		fd = -EPERM;
  		if (!capable(CAP_SYS_ADMIN))
  			goto out_put_group;
  		group->fanotify_data.max_marks = UINT_MAX;
  	} else {
  		group->fanotify_data.max_marks = FANOTIFY_DEFAULT_MAX_MARKS;
  	}
  
  	fd = anon_inode_getfd("[fanotify]", &fanotify_fops, group, f_flags);
  	if (fd < 0)
  		goto out_put_group;
  
  	return fd;
  
  out_put_group:
  	fsnotify_put_group(group);
  	return fd;
  }
  
  SYSCALL_DEFINE(fanotify_mark)(int fanotify_fd, unsigned int flags,
  			      __u64 mask, int dfd,
  			      const char  __user * pathname)
  {
  	struct inode *inode = NULL;
  	struct vfsmount *mnt = NULL;
  	struct fsnotify_group *group;
  	struct file *filp;
  	struct path path;
  	int ret, fput_needed;
  
  	pr_debug("%s: fanotify_fd=%d flags=%x dfd=%d pathname=%p mask=%llx\n",
  		 __func__, fanotify_fd, flags, dfd, pathname, mask);
  
  	/* we only use the lower 32 bits as of right now. */
  	if (mask & ((__u64)0xffffffff << 32))
  		return -EINVAL;
  
  	if (flags & ~FAN_ALL_MARK_FLAGS)
  		return -EINVAL;
  	switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE | FAN_MARK_FLUSH)) {
  	case FAN_MARK_ADD:		/* fallthrough */
  	case FAN_MARK_REMOVE:
  		if (!mask)
  			return -EINVAL;
  	case FAN_MARK_FLUSH:
  		break;
  	default:
  		return -EINVAL;
  	}
  
  	if (mask & FAN_ONDIR) {
  		flags |= FAN_MARK_ONDIR;
  		mask &= ~FAN_ONDIR;
  	}
  
  #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
  	if (mask & ~(FAN_ALL_EVENTS | FAN_ALL_PERM_EVENTS | FAN_EVENT_ON_CHILD))
  #else
  	if (mask & ~(FAN_ALL_EVENTS | FAN_EVENT_ON_CHILD))
  #endif
  		return -EINVAL;
  
  	filp = fget_light(fanotify_fd, &fput_needed);
  	if (unlikely(!filp))
  		return -EBADF;
  
  	/* verify that this is indeed an fanotify instance */
  	ret = -EINVAL;
  	if (unlikely(filp->f_op != &fanotify_fops))
  		goto fput_and_out;
  	group = filp->private_data;
  
  	/*
  	 * group->priority == FS_PRIO_0 == FAN_CLASS_NOTIF.  These are not
  	 * allowed to set permissions events.
  	 */
  	ret = -EINVAL;
  	if (mask & FAN_ALL_PERM_EVENTS &&
  	    group->priority == FS_PRIO_0)
  		goto fput_and_out;
  
  	ret = fanotify_find_path(dfd, pathname, &path, flags);
  	if (ret)
  		goto fput_and_out;
  
  	/* inode held in place by reference to path; group by fget on fd */
  	if (!(flags & FAN_MARK_MOUNT))
  		inode = path.dentry->d_inode;
  	else
  		mnt = path.mnt;
  
  	/* create/update an inode mark */
  	switch (flags & (FAN_MARK_ADD | FAN_MARK_REMOVE | FAN_MARK_FLUSH)) {
  	case FAN_MARK_ADD:
  		if (flags & FAN_MARK_MOUNT)
  			ret = fanotify_add_vfsmount_mark(group, mnt, mask, flags);
  		else
  			ret = fanotify_add_inode_mark(group, inode, mask, flags);
  		break;
  	case FAN_MARK_REMOVE:
  		if (flags & FAN_MARK_MOUNT)
  			ret = fanotify_remove_vfsmount_mark(group, mnt, mask, flags);
  		else
  			ret = fanotify_remove_inode_mark(group, inode, mask, flags);
  		break;
  	case FAN_MARK_FLUSH:
  		if (flags & FAN_MARK_MOUNT)
  			fsnotify_clear_vfsmount_marks_by_group(group);
  		else
  			fsnotify_clear_inode_marks_by_group(group);
  		break;
  	default:
  		ret = -EINVAL;
  	}
  
  	path_put(&path);
  fput_and_out:
  	fput_light(filp, fput_needed);
  	return ret;
  }
  
  #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
  asmlinkage long SyS_fanotify_mark(long fanotify_fd, long flags, __u64 mask,
  				  long dfd, long pathname)
  {
  	return SYSC_fanotify_mark((int) fanotify_fd, (unsigned int) flags,
  				  mask, (int) dfd,
  				  (const char  __user *) pathname);
  }
  SYSCALL_ALIAS(sys_fanotify_mark, SyS_fanotify_mark);
  #endif
  
  /*
   * fanotify_user_setup - Our initialization function.  Note that we cannot return
   * error because we have compiled-in VFS hooks.  So an (unlikely) failure here
   * must result in panic().
   */
  static int __init fanotify_user_setup(void)
  {
  	fanotify_mark_cache = KMEM_CACHE(fsnotify_mark, SLAB_PANIC);
  	fanotify_response_event_cache = KMEM_CACHE(fanotify_response_event,
  						   SLAB_PANIC);
  
  	return 0;
  }
  device_initcall(fanotify_user_setup);
  