linux-kernel - Re: [PATCH v2] hid-appleir: Fix kernel panic due to null pointer

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Message-ID: <20140701065021.GA887@mguzik.redhat.com>
Date:	Tue, 1 Jul 2014 08:50:22 +0200
From:	Mateusz Guzik <mguzik@...hat.com>
To:	Jiri Kosina <jkosina@...e.cz>
Cc:	Nicholas Krause <xerofoify@...il.com>, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] hid-appleir: Fix kernel panic due to null pointer

On Tue, Jul 01, 2014 at 08:39:06AM +0200, Jiri Kosina wrote:
> On Mon, 30 Jun 2014, Nicholas Krause wrote:
> 
> > Fixes a null pointer in appleir_input_configured due to reading
> > into wrong size array. Changed the variable to input_dev->keycodemax.
> 
> This is a stale changelog from the previous buggy version.
> 
> > Signed-off-by: Nicholas Krause <xerofoify@...il.com>
> > ---
> >  drivers/hid/hid-appleir.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/hid/hid-appleir.c b/drivers/hid/hid-appleir.c
> > index 0e6a42d..cc02df4 100644
> > --- a/drivers/hid/hid-appleir.c
> > +++ b/drivers/hid/hid-appleir.c
> > @@ -272,7 +272,7 @@ static void appleir_input_configured(struct hid_device *hid,
> >  	input_dev->evbit[0] = BIT(EV_KEY) | BIT(EV_REP);
> >  
> >  	memcpy(appleir->keymap, appleir_key_table, sizeof(appleir->keymap));
> > -	for (i = 0; i < ARRAY_SIZE(appleir_key_table); i++)
> > +	for (i = 0; i < appleir->keymap; i++)
> 
> This is wrong. appleir->keymap is an array, and you want to count its 
> elements.
> 

But where the claim of 'null pointer' is coming from (or reading/writing
past the array for that matter)?

Replacing appleir_key_table with appleir->keymap is a noop anyway
because:
unsigned short keymap[ARRAY_SIZE(appleir_key_table)];

although one may argue is slightly nicer since it is used in memcpy line
earlier.
-- 
Mateusz Guzik
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