[PATCH v3] input: touchscreen: wm97xx-core: Fix possible null-pointer dereferences in wm97xx_ts_input_open()

[PATCH v3] input: touchscreen: wm97xx-core: Fix possible null-pointer dereferences in wm97xx_ts_input_open()

[Jia-Ju Bai]

In wm97xx_ts_input_open(), there is an if statement on line 507 to check
whether wm->mach_ops is NULL:
    if (wm->mach_ops && wm->mach_ops->acc_enabled)

When wm->mach_ops is NULL, it is used on line 521:
    wm97xx_init_pen_irq(wm);
        BUG_ON(!wm->mach_ops->irq_enable);
        BUG_ON(!wm->mach_ops->irq_gpio);
        wm97xx_reg_write(..., reg & ~(wm->mach_ops->irq_gpio))

Thus, possible null-pointer dereferences may occur.

To fix these bugs, wm->mach_ops is checked at the beginning of
wm97xx_init_pen_irq().

These bugs found by a static analysis tool STCheck written by us.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
---
v2:
* Add a new check of wm->mach_ops in wm97xx_init_pen_irq().
  Thank Charles for helpful advice.

v3:
* Print a message if wm->mach_ops is NULL in wm97xx_init_pen_irq().
  Thank Charles for helpful advice.

---
 drivers/input/touchscreen/wm97xx-core.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/input/touchscreen/wm97xx-core.c b/drivers/input/touchscreen/wm97xx-core.c
index 0a174bd82915..bf754cb8965c 100644
--- a/drivers/input/touchscreen/wm97xx-core.c
+++ b/drivers/input/touchscreen/wm97xx-core.c
@@ -374,6 +374,11 @@ static int wm97xx_init_pen_irq(struct wm97xx *wm)
 {
 	u16 reg;
 
+	if (!wm->mach_ops) {
+		dev_err(wm->dev, "mach_ops is NULL");
+		return -EINVAL;
+	}
+
 	/* If an interrupt is supplied an IRQ enable operation must also be
 	 * provided. */
 	BUG_ON(!wm->mach_ops->irq_enable);
-- 
2.17.0

Re: [PATCH v3] input: touchscreen: wm97xx-core: Fix possible null-pointer dereferences in wm97xx_ts_input_open()

[Charles Keepax]

On Fri, Jul 26, 2019 at 06:23:26PM +0800, Jia-Ju Bai wrote:
> In wm97xx_ts_input_open(), there is an if statement on line 507 to check
> whether wm->mach_ops is NULL:
>     if (wm->mach_ops && wm->mach_ops->acc_enabled)
> 
> When wm->mach_ops is NULL, it is used on line 521:
>     wm97xx_init_pen_irq(wm);
>         BUG_ON(!wm->mach_ops->irq_enable);
>         BUG_ON(!wm->mach_ops->irq_gpio);
>         wm97xx_reg_write(..., reg & ~(wm->mach_ops->irq_gpio))
> 
> Thus, possible null-pointer dereferences may occur.
> 
> To fix these bugs, wm->mach_ops is checked at the beginning of
> wm97xx_init_pen_irq().
> 
> These bugs found by a static analysis tool STCheck written by us.
> 
> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
> ---
> v2:
> * Add a new check of wm->mach_ops in wm97xx_init_pen_irq().
>   Thank Charles for helpful advice.
> 
> v3:
> * Print a message if wm->mach_ops is NULL in wm97xx_init_pen_irq().
>   Thank Charles for helpful advice.
> 
> ---

Acked-by: Charles Keepax <ckeepax@opensource.cirrus.com>

Thanks,
Charles