[PATCH 5.16 241/285] gpio: Restrict usage of GPIO chip irq members before initialization

Greg Kroah-Hartman
2022-04-12T08:40:39Z

From: Shreeya Patel <shreeya.patel@collabora.com>

commit 5467801f1fcbdc46bc7298a84dbf3ca1ff2a7320 upstream.

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>
Cc: stable@vger.kernel.org
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/gpio/gpiolib.c | 19 +++++++++++++++++++
include/linux/gpio/driver.h | 9 +++++++++
2 files changed, 28 insertions(+)

--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1368,6 +1368,16 @@ static int gpiochip_to_irq(struct gpio_c
{
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;

@@ -1557,6 +1567,15 @@ static int gpiochip_add_irqchip(struct g

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;
}

--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -219,6 +219,15 @@ 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
* a particular driver wants to clear IRQ related registers