linux-kernel - Re: [appleir] BUG: unable to handle kernel NULL pointer dereference

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Date:	Wed, 6 Nov 2013 16:38:26 +0100 (CET)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Luis Henriques <luis.henriques@...onical.com>
Cc:	Benjamin Tissoires <benjamin.tissoires@...hat.com>,
	linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
	James Henstridge <james.henstridge@...onical.com>,
	Fabien André <fabien.andre@...il.com>,
	Bastien Nocera <hadess@...ess.net>
Subject: Re: [appleir] BUG: unable to handle kernel NULL pointer
 dereference

On Tue, 29 Oct 2013, Luis Henriques wrote:

> James has reported a NULL pointer dereference[1] on the appleir
> driver.  From the bug report[2] it looks like it is 100%
> reproducible using a 3.12-rc6 kernel simply by pressing any button on
> the IR remote.
> 
> >From the stack trace, it looks like input_event is invoked with the
> input_dev parameter set to NULL, which seems to indicate that
> appleir_input_configured is never invoked.
> 
> Any ideas?
> 
> [1] https://launchpadlibrarian.net/154942024/macmini-oops.jpg
> [2] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1244505

[ adding some more CCs ]

Okay, so apparently we didn't register with input, but only hiddev / 
hidraw.

appleir 0003:05AC:8240.0005: hiddev0,hidraw4: USB HID v1.11 Device [Apple Computer, Inc. IR Receiver] on usb-0000:00:1d.3-2/input0

Therefore ->input_configured() callback has never been called, and thus we 
oops due to appleir->input_dev being NULL when the first raw event is 
reported.

Could you please provide report descriptor of the device?

The driver apparently relies on it being registered with hid-input, but 
for some reason that doesn't happen.

-- 
Jiri Kosina
SUSE Labs
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