Re: [PATCH] input: pxa27x_keypad: fix NULL pointer dereference

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

On Tue, Sep 17, 2013 at 09:05:54PM -0700, Mike Dunn wrote:
> On 09/16/2013 10:06 AM, Dmitry Torokhov wrote:
> > On Mon, Sep 16, 2013 at 06:49:53PM +0200, Marek Vasut wrote:
> >> Dear Mike Dunn,
> >>
> >>> A NULL pointer dereference exception occurs in the driver probe function
> >>> when device tree is used.  The pdata pointer will be NULL in this case,
> >>> but the code dereferences it in all cases.  When device tree is used, a
> >>> platform data structure is allocated and initialized, and in all cases
> >>> this pointer is copied to the driver's private data, so the variable being
> >>> tested should be accessed through the driver's private data structure.
> >>>
> >>> Signed-off-by: Mike Dunn <mikedunn@newsguy.com>
> >>> ---
> >>>  drivers/input/keyboard/pxa27x_keypad.c | 6 ++++--
> >>>  1 file changed, 4 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/drivers/input/keyboard/pxa27x_keypad.c
> >>> b/drivers/input/keyboard/pxa27x_keypad.c index 134c3b4..3b2a614 100644
> >>> --- a/drivers/input/keyboard/pxa27x_keypad.c
> >>> +++ b/drivers/input/keyboard/pxa27x_keypad.c
> >>> @@ -795,8 +795,10 @@ static int pxa27x_keypad_probe(struct platform_device
> >>> *pdev) goto failed_put_clk;
> >>>  	}
> >>>
> >>> -	if ((pdata->enable_rotary0 && keypad->rotary_rel_code[0] != -1) ||
> >>> -	    (pdata->enable_rotary1 && keypad->rotary_rel_code[1] != -1)) {
> >>> +	if ((keypad->pdata->enable_rotary0 &&
> >>> +	     keypad->rotary_rel_code[0] != -1) ||
> >>> +	    (keypad->pdata->enable_rotary1 &&
> >>> +	     keypad->rotary_rel_code[1] != -1)) {
> >>>  		input_dev->evbit[0] |= BIT_MASK(EV_REL);
> >>>  	}
> >>
> >> Nice find. Acked-by: Marek Vasut <marex@denx.de>
> > 
> > Excellent booby trap. I would prefer if we explicitly did
> > 
> > 	pdata = keypad->pdata;
> > 
> > after calling the parse DT fucntion with a nice comment, because we
> > somebody might want to rearrange the code and accidentially revert the
> > checks to the original state.
> 
> 
> Yes, that would have been better.  Is someone picking this up?  I'm not familir
> with the input subsystem maintainer (sorry).

That would be yours truly.

> If this will be upstreamed in
> someone's tree, I'll be glad to resubmit with this change.

If you could resubmit that would be great - I do not have the hardware
and I prefer applying patches that were tested, if possible.

Thanks.

-- 
Dmitry