On Mon, Aug 20, 2012 at 09:44:40PM +0100, Alan M Butler wrote:
> On 20 August 2012 19:48, Fabio Estevam <fabio.estevam@xxxxxxxxxxxxx> wrote:
> > Commit 30161f6b2e7d1 (Input: gpio_keys - clean up device tree parser)
> > introduced the following kernel crash for a dt based kernel:
> > ..
> > Unable to handle kernel NULL pointer dereference at virtual address 00000004
> > pgd = 80004000
> > [00000004] *pgd=00000000
> > Internal error: Oops: 805 [#1] ARM
> > Modules linked in:
> > CPU: 0 Not tainted (3.5.0-next-20120802+ #1366)
> > PC is at gpio_keys_probe+0x154/0x8c0
> > LR is at of_gpiochip_find_and_xlate+0x54/0x70
> > pc : [<803ddbac>] lr : [<801ed2f4>] psr: 60000013
> > sp : 9f851df8 ip : 00000002 fp : 9f851e5c
> > r10: 9f873d00 r9 : 00000001 r8 : 9fa2f900
> > r7 : 809c0920 r6 : 9f873d08 r5 : 00000000 r4 : 809c09d4
> > r3 : 805af10c r2 : 000000c0 r1 : 9f851db4 r0 : 000000d5
> > Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment kernel
> > Control: 10c5387d Table: 90004019 DAC: 00000015
> > Process swapper (pid: 1, stack limit = 0x9f8502e8)
> > Stack: (0x9f851df8 to 0x9f852000)
> > ....
> >
> > The reason for the crash was due to 'button = &pdata->buttons[i++];'
> > returning a NULL pointer, and then 'button' was accessed afterwards
> > without checking for NULL.
> >
> > Fix this by correctly assigning 'pdata->buttons' and also add a NULL
> > pointer check for 'button' pointer.
> >
> > Signed-off-by: Fabio Estevam <fabio.estevam@xxxxxxxxxxxxx>
> > ---
> > Changes since v1:
> > - Fix the location of 'button = pdata->buttons'. This fixes the probing of multiple keys.
> >
> > drivers/input/keyboard/gpio_keys.c | 13 ++++++++++---
> > 1 file changed, 10 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/input/keyboard/gpio_keys.c b/drivers/input/keyboard/gpio_keys.c
> > index 6ee68ec..c90c152 100644
> > --- a/drivers/input/keyboard/gpio_keys.c
> > +++ b/drivers/input/keyboard/gpio_keys.c
> > @@ -559,7 +559,6 @@ gpio_keys_get_devtree_pdata(struct device *dev)
> > struct gpio_keys_button *button;
> > int error;
> > int nbuttons;
> > - int i;
> >
> > node = dev->of_node;
> > if (!node) {
> > @@ -580,9 +579,12 @@ gpio_keys_get_devtree_pdata(struct device *dev)
> > goto err_out;
> > }
> >
> > + pdata->buttons = (struct gpio_keys_button *) (pdata + 1);
> > + pdata->nbuttons = nbuttons;
> > +
> > pdata->rep = !!of_get_property(node, "autorepeat", NULL);
> > + button = pdata->buttons;
> >
> > - i = 0;
> > for_each_child_of_node(node, pp) {
> > enum of_gpio_flags flags;
> >
> > @@ -592,7 +594,10 @@ gpio_keys_get_devtree_pdata(struct device *dev)
> > continue;
> > }
> >
> > - button = &pdata->buttons[i++];
> > + if (!button) {
> > + error = -ENOMEM;
> > + goto err_free_pdata;
> > + }
This tests impossible condition.
> >
> > button->gpio = of_get_gpio_flags(pp, 0, &flags);
> > button->active_low = flags & OF_GPIO_ACTIVE_LOW;
> > @@ -614,6 +619,8 @@ gpio_keys_get_devtree_pdata(struct device *dev)
> > if (of_property_read_u32(pp, "debounce-interval",
> > &button->debounce_interval))
> > button->debounce_interval = 5;
> > +
> > + button++;
> > }
> >
> > if (pdata->nbuttons == 0) {
> > --
> > 1.7.9.5
> >
> >
>
> Tested-by: Alan M Butler <alanbutty12@xxxxxxxxx>
I took the part initializing pdata->buttons and pdata->nbuttons and
folded it into the offending patch.
Thank you!
--
Dmitry
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