GPIO chip irq members are exposed before they could be completely
initialized and this leads to race conditions.
One such issue was observed for the gc->irq.domain variable which
was accessed through the I2C interface in gpiochip_to_irq() before
it could be initialized by gpiochip_add_irqchip(). This resulted in
Kernel NULL pointer dereference.
Following are the logs for reference :-
kernel: Call Trace:
kernel: gpiod_to_irq+0x53/0x70
kernel: acpi_dev_gpio_irq_get_by+0x113/0x1f0
kernel: i2c_acpi_get_irq+0xc0/0xd0
kernel: i2c_device_probe+0x28a/0x2a0
kernel: really_probe+0xf2/0x460
kernel: RIP: 0010:gpiochip_to_irq+0x47/0xc0
To avoid such scenarios, restrict usage of GPIO chip irq members before
they are completely initialized.
Signed-off-by: Shreeya Patel <[email protected]>
---
Changes in v3
- Move the gc->irq.initialized check inside gpiochip_to_irq().
- Rename gc to GPIO chip.
- Add barrier() to avoid compiler reordering.
Changes in v2
- Make gc_irq_initialized flag a member of gpio_irq_chip structure.
- Make use of barrier() to avoid reordering of flag initialization
before other gc irq members are initialized.
drivers/gpio/gpiolib.c | 19 +++++++++++++++++++
include/linux/gpio/driver.h | 9 +++++++++
2 files changed, 28 insertions(+)
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index defb7c464b87..4ff68f48b87f 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1404,6 +1404,16 @@ static int gpiochip_to_irq(struct gpio_chip *gc, unsigned int offset)
{
struct irq_domain *domain = gc->irq.domain;
+#ifdef CONFIG_GPIOLIB_IRQCHIP
+ /*
+ * Avoid race condition with other code, which tries to lookup
+ * an IRQ before the irqchip has been properly registered,
+ * i.e. while gpiochip is still being brought up.
+ */
+ if (!gc->irq.initialized)
+ return -EPROBE_DEFER;
+#endif
+
if (!gpiochip_irqchip_irq_valid(gc, offset))
return -ENXIO;
@@ -1593,6 +1603,15 @@ static int gpiochip_add_irqchip(struct gpio_chip *gc,
acpi_gpiochip_request_interrupts(gc);
+ /*
+ * Using barrier() here to prevent compiler from reordering
+ * gc->irq.initialized before initialization of above
+ * GPIO chip irq members.
+ */
+ barrier();
+
+ gc->irq.initialized = true;
+
return 0;
}
diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
index b0728c8ad90c..f8996b46f430 100644
--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -218,6 +218,15 @@ struct gpio_irq_chip {
*/
bool per_parent_data;
+ /**
+ * @initialized:
+ *
+ * Flag to track GPIO chip irq member's initialization.
+ * This flag will make sure GPIO chip irq members are not used
+ * before they are initialized.
+ */
+ bool initialized;
+
/**
* @init_hw: optional routine to initialize hardware before
* an IRQ chip will be added. This is quite useful when
--
2.30.2
On Mon, Mar 21, 2022 at 2:33 PM Shreeya Patel
<[email protected]> wrote:
> GPIO chip irq members are exposed before they could be completely
> initialized and this leads to race conditions.
>
> One such issue was observed for the gc->irq.domain variable which
> was accessed through the I2C interface in gpiochip_to_irq() before
> it could be initialized by gpiochip_add_irqchip(). This resulted in
> Kernel NULL pointer dereference.
>
> Following are the logs for reference :-
>
> kernel: Call Trace:
> kernel: gpiod_to_irq+0x53/0x70
> kernel: acpi_dev_gpio_irq_get_by+0x113/0x1f0
> kernel: i2c_acpi_get_irq+0xc0/0xd0
> kernel: i2c_device_probe+0x28a/0x2a0
> kernel: really_probe+0xf2/0x460
> kernel: RIP: 0010:gpiochip_to_irq+0x47/0xc0
>
> To avoid such scenarios, restrict usage of GPIO chip irq members before
> they are completely initialized.
>
> Signed-off-by: Shreeya Patel <[email protected]>
Reviewed-by: Linus Walleij <[email protected]>
Yours,
Linus Walleij
On Mon, Mar 21, 2022 at 2:33 PM Shreeya Patel
<[email protected]> wrote:
>
> GPIO chip irq members are exposed before they could be completely
> initialized and this leads to race conditions.
>
> One such issue was observed for the gc->irq.domain variable which
> was accessed through the I2C interface in gpiochip_to_irq() before
> it could be initialized by gpiochip_add_irqchip(). This resulted in
> Kernel NULL pointer dereference.
>
> Following are the logs for reference :-
>
> kernel: Call Trace:
> kernel: gpiod_to_irq+0x53/0x70
> kernel: acpi_dev_gpio_irq_get_by+0x113/0x1f0
> kernel: i2c_acpi_get_irq+0xc0/0xd0
> kernel: i2c_device_probe+0x28a/0x2a0
> kernel: really_probe+0xf2/0x460
> kernel: RIP: 0010:gpiochip_to_irq+0x47/0xc0
>
> To avoid such scenarios, restrict usage of GPIO chip irq members before
> they are completely initialized.
>
> Signed-off-by: Shreeya Patel <[email protected]>
> ---
>
> Changes in v3
> - Move the gc->irq.initialized check inside gpiochip_to_irq().
> - Rename gc to GPIO chip.
> - Add barrier() to avoid compiler reordering.
>
> Changes in v2
> - Make gc_irq_initialized flag a member of gpio_irq_chip structure.
> - Make use of barrier() to avoid reordering of flag initialization
> before other gc irq members are initialized.
>
>
> drivers/gpio/gpiolib.c | 19 +++++++++++++++++++
> include/linux/gpio/driver.h | 9 +++++++++
> 2 files changed, 28 insertions(+)
>
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index defb7c464b87..4ff68f48b87f 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -1404,6 +1404,16 @@ static int gpiochip_to_irq(struct gpio_chip *gc, unsigned int offset)
> {
> struct irq_domain *domain = gc->irq.domain;
>
> +#ifdef CONFIG_GPIOLIB_IRQCHIP
> + /*
> + * Avoid race condition with other code, which tries to lookup
> + * an IRQ before the irqchip has been properly registered,
> + * i.e. while gpiochip is still being brought up.
> + */
> + if (!gc->irq.initialized)
> + return -EPROBE_DEFER;
> +#endif
> +
> if (!gpiochip_irqchip_irq_valid(gc, offset))
> return -ENXIO;
>
> @@ -1593,6 +1603,15 @@ static int gpiochip_add_irqchip(struct gpio_chip *gc,
>
> acpi_gpiochip_request_interrupts(gc);
>
> + /*
> + * Using barrier() here to prevent compiler from reordering
> + * gc->irq.initialized before initialization of above
> + * GPIO chip irq members.
> + */
> + barrier();
> +
> + gc->irq.initialized = true;
> +
> return 0;
> }
>
> diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
> index b0728c8ad90c..f8996b46f430 100644
> --- a/include/linux/gpio/driver.h
> +++ b/include/linux/gpio/driver.h
> @@ -218,6 +218,15 @@ struct gpio_irq_chip {
> */
> bool per_parent_data;
>
> + /**
> + * @initialized:
> + *
> + * Flag to track GPIO chip irq member's initialization.
> + * This flag will make sure GPIO chip irq members are not used
> + * before they are initialized.
> + */
> + bool initialized;
> +
> /**
> * @init_hw: optional routine to initialize hardware before
> * an IRQ chip will be added. This is quite useful when
> --
> 2.30.2
>
I queued it for fixes, let's backport it to stable.
Bart