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SubjectRe: [PATCH v2] hid-appleir: Fix kernel panic due to null pointer
On Tue, 1 Jul 2014, Mateusz Guzik 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@gmail.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)];

It's not really equivalent. ARRAY_SIZE counts the number of short-sized
elements, sizeof() counts the number of bytes that fit into the data
structure (which is twice as much, as sizeof(unsigned short) == 2).

--
Jiri Kosina
SUSE Labs


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