Flaws with "UIO: Add the User IO core code"

[Alan Cox <alan@lxorguk.ukuu.org.uk>]

> +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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