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

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Message-ID: <20070428001923.15074234@the-village.bc.nu>
Date:	Sat, 28 Apr 2007 00:19:23 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Greg Kroah-Hartman <gregkh@...e.de>
Cc:	linux-kernel@...r.kernel.org, torvalds@...l.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Benedikt Spranger <b.spranger@...utronix.de>,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: Flaws with "UIO: Add the User IO core code"

> +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)

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

Alan
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