linux-kernel - Re: Flaws with "UIO: Add the User IO core code"

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Date:	Sat, 28 Apr 2007 13:39:27 +0200
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Greg Kroah-Hartman <gregkh@...e.de>, linux-kernel@...r.kernel.org,
	torvalds@...l.org, Benedikt Spranger <b.spranger@...utronix.de>
Subject: Re: Flaws with "UIO: Add the User IO core code"

On Sat, 2007-04-28 at 00:19 +0100, Alan Cox wrote:
> > +static ssize_t uio_read(struct file *filep, char __user *buf,
> > +			size_t count, loff_t *ppos)
> > +{
> > +	struct uio_listener *listener = filep->private_data;
> > +	struct uio_device *idev = listener->dev;
> > +	DECLARE_WAITQUEUE(wait, current);
> > +	ssize_t retval;
> > +	int event_count;
> > +
> > +	if (idev->info->irq == UIO_IRQ_NONE)
> > +		return -EIO;
> > +
> > +	if (count != sizeof(int))
> > +		return -EINVAL;
> 
> AFAIK we don't currently have any platform that runs binaries with
> different sizes of "int" but this is a) an unsigned value anyway, and b)
> should be a fixed type (eg u32)

Good point.

> Otherwise it looks ok at the momenmt, although there is a real nasty
> waiting for anyone who tries to use it. At the point open is possible or
> IRQs can be enabled you are safe in the core merged as idev->info is
> always valid, but any driver module trying to go back via info->uio_dev
> has a NULL pointer for an early IRQ or open event.
> 
> This means that the fasync support in the current code is basically
> unusable until this is fixed

We'll fix that ASAP.

	tglx


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