Re: device_remove_file and disconnect

[matthieu castet <castet.matthieu@free.fr>]

Hi,

Greg KH wrote:
> On Wed, Jun 29, 2005 at 06:59:00PM +0200, matthieu castet wrote:
>
> > Hi,
> >
> > I have a question about sysfs interface.
> >
> > If you open a sysfs file created by a module, then remove it (rmmoding 
> > the module that create this sysfs file), then try to read the opened 
> > file, you often get strange result (segdefault or oppps).
>
>
> What file did you do this for?  The module count should be incremented
> if you do this, to prevent the module from being unloaded.
Ok, but if we unplug a device, then disconnect will be called even if we 
opened a sysfs file.

Couldn't be a race between the moment we read our private data and check 
it is valid and the moment we use it :

Process A (read/write sysfs file) 		Process B (disconnect)
recover our private data from struct device
check it is valid
						free our private data
do operation on private data


> > If it is the first case, I fear that lot's of modules are broken.
>
>
> Remember, only root can unload modules, so it really isn't _that_ big of
> a deal (I can do a lot more damage as root than just oopsing the
> kernel...)
Yes I know, but fewer possible opps won't hurt ;)

thanks

Matthieu
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