From: Shreeya Patel <shreeya.patel@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
Signed-off-by: Bartosz Golaszewski <brgl@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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;
@@ -1552,6 +1562,15 @@ 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
@@ -225,6 +225,15 @@ struct gpio_irq_chip {
unsigned int ngpios);
/**
+ * @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;
+
+ /**
* @valid_mask:
*
* If not %NULL, holds bitmask of GPIOs which are valid to be included
