linux-kernel - Re: mfd: lpc_ich: NULL pointer dereference at (second) module removal

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Date:	Mon, 19 Nov 2012 09:30:31 -0600
From:	Peter Tyser <ptyser@...-inc.com>
To:	Samuel Ortiz <sameo@...ux.intel.com>
Cc:	Paul Bolle <pebolle@...cali.nl>, linux-kernel@...r.kernel.org
Subject: Re: mfd: lpc_ich: NULL pointer dereference at (second) module
 removal

Hi Samuel,

> > On Fri, 2012-11-09 at 14:19 +0100, Paul Bolle wrote:
> > > 0) I can trigger a NULL pointer dereference if I remove the lpc_ich
> > > module. This seems to only happen if I remove it for the second time
> > > (ie, remove the module, insert it and remove it again). This happens
> > > both on i686 and x86_64 (different setups, as inserting the module
> > > triggers different messages about the initialization of the MFD cells on
> > > these machines). Both machines are running v3.6.6.
> > 
> > I believe this is caused by the fact that non-MFD devices get attached
> > to the same parent as the iTCO_wdt driver, which is an MFD.  When the
> > MFD code attempts unregister the MFD drivers, it oops when the non-MFD
> > devices are accessed since they don't have the mfd_cell node.
> That's probably correct. I just merged commit
> 5dc4dda91c86ef82bd53d77e5de50ec095b33e46 into my for-next branch and that one
> could fix that issue. Could you guys please give it a go ? This is the actual
> patch:
> 
> From 5dc4dda91c86ef82bd53d77e5de50ec095b33e46 Mon Sep 17 00:00:00 2001
> From: Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
> Date: Fri, 9 Nov 2012 16:15:28 +0000
> Subject: [PATCH] mfd: Only unregister platform devices allocated by the mfd
>  core
> 
> mfd_remove_devices would iterate over all devices sharing a parent with
> an mfd device regardless of whether they were allocated by the mfd core
> or not. This especially caused problems when the device structure was
> not contained within a platform_device, because to_platform_device is
> used on each device pointer.
> 
> This patch defines a device_type for mfd devices and checks this is
> present from mfd_remove_devices_fn before processing the device.
> 
> Signed-off-by: Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
> Reviewed-by: Mark Brown <broonie@...nsource.wolfsonmicro.com>
> Signed-off-by: Samuel Ortiz <sameo@...ux.intel.com>

Tested-by: Peter Tyser <ptyser@...-inc.com>

Looks good to me.

Best,
Peter

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