From 07d2390e36ee5b3265e9cc8305f2a106c8721e16 Mon Sep 17 00:00:00 2001 From: Krzysztof Kozlowski Date: Mon, 4 Apr 2016 14:54:59 +0900 Subject: [PATCH] iio: ak8975: Fix NULL pointer exception on early interrupt In certain probe conditions the interrupt came right after registering the handler causing a NULL pointer exception because of uninitialized waitqueue: $ udevadm trigger i2c-gpio i2c-gpio-1: using pins 143 (SDA) and 144 (SCL) i2c-gpio i2c-gpio-3: using pins 53 (SDA) and 52 (SCL) Unable to handle kernel NULL pointer dereference at virtual address 00000000 pgd = e8b38000 [00000000] *pgd=00000000 Internal error: Oops: 5 [#1] SMP ARM Modules linked in: snd_soc_i2s(+) i2c_gpio(+) snd_soc_idma snd_soc_s3c_dma snd_soc_core snd_pcm_dmaengine snd_pcm snd_timer snd soundcore ac97_bus spi_s3c64xx pwm_samsung dwc2 exynos_adc phy_exynos_usb2 exynosdrm exynos_rng rng_core rtc_s3c CPU: 0 PID: 717 Comm: data-provider-m Not tainted 4.6.0-rc1-next-20160401-00011-g1b8d87473b9e-dirty #101 Hardware name: SAMSUNG EXYNOS (Flattened Device Tree) (...) (__wake_up_common) from [] (__wake_up+0x38/0x4c) (__wake_up) from [] (ak8975_irq_handler+0x28/0x30) (ak8975_irq_handler) from [] (handle_irq_event_percpu+0x88/0x140) (handle_irq_event_percpu) from [] (handle_irq_event+0x44/0x68) (handle_irq_event) from [] (handle_edge_irq+0xf0/0x19c) (handle_edge_irq) from [] (generic_handle_irq+0x24/0x34) (generic_handle_irq) from [] (exynos_eint_gpio_irq+0x50/0x68) (exynos_eint_gpio_irq) from [] (handle_irq_event_percpu+0x88/0x140) (handle_irq_event_percpu) from [] (handle_irq_event+0x44/0x68) (handle_irq_event) from [] (handle_fasteoi_irq+0xb4/0x194) (handle_fasteoi_irq) from [] (generic_handle_irq+0x24/0x34) (generic_handle_irq) from [] (__handle_domain_irq+0x5c/0xb4) (__handle_domain_irq) from [] (gic_handle_irq+0x54/0x94) (gic_handle_irq) from [] (__irq_usr+0x50/0x80) The bug was reproduced on exynos4412-trats2 (with a max77693 device also using i2c-gpio) after building max77693 as a module. Cc: Fixes: 94a6d5cf7caa ("iio:ak8975 Implement data ready interrupt handling") Signed-off-by: Krzysztof Kozlowski Tested-by: Gregor Boirie Signed-off-by: Jonathan Cameron --- drivers/iio/magnetometer/ak8975.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/iio/magnetometer/ak8975.c b/drivers/iio/magnetometer/ak8975.c index 9c5c9ef3f1dad2..3b23a850c930d7 100644 --- a/drivers/iio/magnetometer/ak8975.c +++ b/drivers/iio/magnetometer/ak8975.c @@ -462,6 +462,8 @@ static int ak8975_setup_irq(struct ak8975_data *data) int rc; int irq; + init_waitqueue_head(&data->data_ready_queue); + clear_bit(0, &data->flags); if (client->irq) irq = client->irq; else @@ -477,8 +479,6 @@ static int ak8975_setup_irq(struct ak8975_data *data) return rc; } - init_waitqueue_head(&data->data_ready_queue); - clear_bit(0, &data->flags); data->eoc_irq = irq; return rc;