gpiolib: Fix irq_disable() semantics

The implementation if .irq_disable() which kicks in between
the gpiolib and the driver is not properly mimicking the
expected semantics of the irqchip core: the irqchip will
call .irq_disable() if that exists, else it will call
mask_irq() which first checks if .irq_mask() is defined
before calling it.

Since we are calling it unconditionally, we get this bug
from drivers/pinctrl/qcom/pinctrl-ssbi-gpio.c, as it only
defines .irq_mask_ack and not .irq_mask:

  Unable to handle kernel NULL pointer dereference at virtual address 00000000
  pgd = (ptrval)
  (...)
  PC is at 0x0
  LR is at gpiochip_irq_disable+0x20/0x30

Fix this by only calling .irq_mask() if it exists.

Cc: Brian Masney <masneyb@onstation.org>
Cc: Hans Verkuil <hans.verkuil@cisco.com>
Cc: stable@vger.kernel.org
Reviewed-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Fixes: 461c1a7d4733 ("gpiolib: override irq_enable/disable")
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20200306132326.1329640-1-linus.walleij@linaro.org

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 4d0106ceeba7bb24d3a21177356cacf6a82f69eb..00fb91feba7086e77827e16e84aee8494b62986f 100644 (file)
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2306,9 +2306,16 @@ static void gpiochip_irq_disable(struct irq_data *d)
 {
        struct gpio_chip *chip = irq_data_get_irq_chip_data(d);
 
+       /*
+        * Since we override .irq_disable() we need to mimic the
+        * behaviour of __irq_disable() in irq/chip.c.
+        * First call .irq_disable() if it exists, else mimic the
+        * behaviour of mask_irq() which calls .irq_mask() if
+        * it exists.
+        */
        if (chip->irq.irq_disable)
                chip->irq.irq_disable(d);
-       else
+       else if (chip->irq.chip->irq_mask)
                chip->irq.chip->irq_mask(d);
        gpiochip_disable_irq(chip, d->hwirq);
 }