linux-kernel - Re: [PATCH] uio: Fix uio driver to refcount device

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Message-ID: <55006668.20202@brocade.com>
Date:	Wed, 11 Mar 2015 15:59:36 +0000
From:	Brian Russell <brian.russell@...cade.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Brian Russell <brussell@...cade.com>
CC:	"Hans J. Koch" <hjk@...sjkoch.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] uio: Fix uio driver to refcount device



On 11/03/15 15:43, Greg Kroah-Hartman wrote:
> On Wed, Mar 11, 2015 at 03:31:42PM +0000, Brian Russell wrote:
>> Protect uio driver from crashing if its owner is hot unplugged while there
>> are open fds.
>> Signed-off-by: Brian Russell <brussell@...cade.com>
> 
> Minor nit, you need a blank line before your s-o-b: line.
> 

Ack.

> 
> 
>> ---
>>  drivers/uio/uio.c | 8 +++++++-
>>  1 file changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
>> index 6276f13..70ce015 100644
>> --- a/drivers/uio/uio.c
>> +++ b/drivers/uio/uio.c
>> @@ -434,9 +434,11 @@ static int uio_open(struct inode *inode, struct file *filep)
>>  		goto out;
>>  	}
>>  
>> +	get_device(idev);
> 
> What is the real oops caused when a device is removed?  Protecting this
> with a reference count seems ok, but it seems "heavy".
> 

I'm seeing it with PCI hotplug. The PCI subsystem calls remove and the owner module in turn calls uio_unregister_device while app stil has open fds.

Brian

> thanks,
> 
> greg k-h
> 
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