On Wed, 26 Jul 2006 13:18:15 +0400
Evgeniy Polyakov [off-list ref] wrote:

+static int kevent_ctl_process(struct file *file, 
+		struct kevent_user_control *ctl, void __user *arg)
+{
+	int err;
+	struct kevent_user *u = file->private_data;
+
+	if (!u)
+		return -EINVAL;
+
+	switch (ctl->cmd) {
+		case KEVENT_CTL_ADD:
+			err = kevent_user_ctl_add(u, ctl, 
+					arg+sizeof(struct kevent_user_control));
+			break;
+		case KEVENT_CTL_REMOVE:
+			err = kevent_user_ctl_remove(u, ctl, 
+					arg+sizeof(struct kevent_user_control));
+			break;
+		case KEVENT_CTL_MODIFY:
+			err = kevent_user_ctl_modify(u, ctl, 
+					arg+sizeof(struct kevent_user_control));
+			break;
+		case KEVENT_CTL_WAIT:
+			err = kevent_user_wait(file, u, ctl, arg);
+			break;
+		case KEVENT_CTL_INIT:
+			err = kevent_ctl_init();
+		default:
+			err = -EINVAL;
+			break;
+	}
+
+	return err;
+}

Please indent the body of the switch one tabstop to the left.

+asmlinkage long sys_kevent_ctl(int fd, void __user *arg)
+{
+	int err, fput_needed;
+	struct kevent_user_control ctl;
+	struct file *file;
+
+	if (copy_from_user(&ctl, arg, sizeof(struct kevent_user_control)))
+		return -EINVAL;
+
+	if (ctl.cmd == KEVENT_CTL_INIT)
+		return kevent_ctl_init();
+
+	file = fget_light(fd, &fput_needed);
+	if (!file)
+		return -ENODEV;
+
+	err = kevent_ctl_process(file, &ctl, arg);
+
+	fput_light(file, fput_needed);
+	return err;
+}

If the user passes this an fd which was obtained via means other than
kevent_ctl_init(), the kernel will explode.  Do

	if (file->f_fop != &kevent_user_fops)
		return -EINVAL;