BugLink: https://bugs.launchpad.net/bugs/2007581

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 (backported from commit 5467801f1fcbdc46bc7298a84dbf3ca1ff2a7320) Signed-off-by: Asmaa Mnebhi asmaa@nvidia.com --- 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 abdf448b11a3..e4d47e00c392 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -2146,6 +2146,16 @@ static int gpiochip_to_irq(struct gpio_chip *chip, unsigned offset) { struct irq_domain *domain = chip->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 (!chip->irq.initialized) + return -EPROBE_DEFER; +#endif + if (!gpiochip_irqchip_irq_valid(chip, offset)) return -ENXIO;

@@ -2321,6 +2331,15 @@ static int gpiochip_add_irqchip(struct gpio_chip *gpiochip,

acpi_gpiochip_request_interrupts(gpiochip);

+ /* + * Using barrier() here to prevent compiler from reordering + * gc->irq.initialized before initialization of above + * GPIO chip irq members. + */ + barrier(); + + gpiochip->irq.initialized = true; + return 0; }

diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h index 5dd9c982e2cb..15418caf76fc 100644 --- a/include/linux/gpio/driver.h +++ b/include/linux/gpio/driver.h @@ -201,6 +201,15 @@ struct gpio_irq_chip { */ bool threaded;

+ /** + * @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