linux-kernel - Re: [PATCH 5/5] uio: Implement hotunplug support, using libunload

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Date:	Fri, 24 Sep 2010 10:11:09 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	"Hans J. Koch" <hjk@...utronix.de>
Cc:	Greg Kroah-Hartman <gregkh@...e.de>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 5/5] uio: Implement hotunplug support, using libunload

"Hans J. Koch" <hjk@...utronix.de> writes:

> On Mon, Sep 20, 2010 at 12:24:19AM -0700, Eric W. Biederman 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;
>> +	struct uio_device *idev = listener_idev(listener);
>>  	DECLARE_WAITQUEUE(wait, current);
>>  	ssize_t retval;
>>  	s32 event_count;
>>  
>> -	if (!idev->info->irq)
>> +	if (!unload_trylock(&idev->unload))
>>  		return -EIO;
>>  
>> +	retval = -EIO;
>> +	if (!idev->info->irq)
>> +		goto out;
>> +
>> +	retval = -EIO;
>>  	if (count != sizeof(s32))
>> -		return -EINVAL;
>> +		goto out;
>
> No. uio_read() should return -EINVAL if count != sizeof(s32). This is
> simply wrong userspace code that passes in an illegal value, so it's
> not an IO error but an invalid parameter.
> BTW, you use -EINVAL in the same situation in uio_write()...

Apologies.  That was a typo.  It was my intention to preserve the
existing return codes.

Eric
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