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SubjectRe: [PATCH v3] gpio: Restrict usage of GPIO chip irq members before initialization
On Mon, Mar 21, 2022 at 2:33 PM Shreeya Patel
<shreeya.patel@collabora.com> 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 <shreeya.patel@collabora.com>
> ---
>
> 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

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