linux-kernel - Re: [PATCH] driver core: fix race with userland in device

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Message-ID: <20140809142045.GA21904@kroah.com>
Date:	Sat, 9 Aug 2014 07:20:45 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Sergey Klyaus <Sergey.Klyaus@...e-IT.Ru>,
	Oliver Neukum <oneukum@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] driver core: fix race with userland in device_add()

On Wed, Aug 06, 2014 at 04:18:38PM -0400, Alan Stern wrote:
> On Wed, 6 Aug 2014, Sergey Klyaus wrote:
> 
> > Hello.
> > 
> > I wrote a patch that fixes the problem that described above, here are a 
> > patch for 3.16.0+ kernel (cloned from GitHub today). Maybe that "if 
> > (MAJOR(dev->devt)) " part has to go even after BUS_NOTIFY_ADD_DEVICE abd 
> > KOBJ_ADD? I put it before it, because there is no rollback code in 
> > device_add() for that part.
> 
> I think this is fine.  However, I suspect the order of the other calls
> there isn't totally right.  For instance, the
> 
> 	if (parent)
> 		klist_add_tail(&dev->p->knode_parent,
> 			       &parent->p->klist_children);
> 
> part should probably be the first thing after we know the routine can't 
> abort.
> 
> I guess the time when bus_probe_device() gets called doesn't matter 
> much, because the driver might not even be loaded at this point.  But 
> what about all the dev->class stuff at the end of device_add()?  Should 
> that happen before any uevents are sent out?
> 
> Greg, have you looked at this?

I haven't, thanks for pointing it out, I'll put it on my list of things
to do this week.

greg k-h
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