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Date: Wed, 26 Jul 2006 03:31:05 -0700
From: Andrew Morton <akpm@osdl.org>
To: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Cc: linux-kernel@vger.kernel.org, davem@davemloft.net, drepper@redhat.com,
       netdev@vger.kernel.org
Subject: Re: [1/4] kevent: core files.
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On Wed, 26 Jul 2006 13:18:15 +0400
Evgeniy Polyakov <johnpol@2ka.mipt.ru> 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;