Merge tag 'gpio-fixes-for-v5.18-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux

Pull gpio fix from Bartosz Golaszewski:

 - fix a race condition with consumers accessing the fields of GPIO IRQ
   chips before they're fully initialized

* tag 'gpio-fixes-for-v5.18-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux:
  gpio: Restrict usage of GPIO chip irq members before initialization

2 files changed, 28 insertions, 0 deletions

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index e59884cc12a7..085348e08986 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 98c93510640e..874aabd270c9 100644
--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -222,6 +222,15 @@ 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