patch "iio: ak8975: Fix NULL pointer exception on early interrupt" added to staging-linus

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    iio: ak8975: Fix NULL pointer exception on early interrupt

to my staging git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git
in the staging-linus branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.

If you have any questions about this process, please let me know.


>From 07d2390e36ee5b3265e9cc8305f2a106c8721e16 Mon Sep 17 00:00:00 2001
From: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Date: Mon, 4 Apr 2016 14:54:59 +0900
Subject: 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 [<c0379624>] (__wake_up+0x38/0x4c)
(__wake_up) from [<c0a41d30>] (ak8975_irq_handler+0x28/0x30)
(ak8975_irq_handler) from [<c0386720>] (handle_irq_event_percpu+0x88/0x140)
(handle_irq_event_percpu) from [<c038681c>] (handle_irq_event+0x44/0x68)
(handle_irq_event) from [<c0389c40>] (handle_edge_irq+0xf0/0x19c)
(handle_edge_irq) from [<c0385e04>] (generic_handle_irq+0x24/0x34)
(generic_handle_irq) from [<c05ee360>] (exynos_eint_gpio_irq+0x50/0x68)
(exynos_eint_gpio_irq) from [<c0386720>] (handle_irq_event_percpu+0x88/0x140)
(handle_irq_event_percpu) from [<c038681c>] (handle_irq_event+0x44/0x68)
(handle_irq_event) from [<c0389a70>] (handle_fasteoi_irq+0xb4/0x194)
(handle_fasteoi_irq) from [<c0385e04>] (generic_handle_irq+0x24/0x34)
(generic_handle_irq) from [<c03860b4>] (__handle_domain_irq+0x5c/0xb4)
(__handle_domain_irq) from [<c0301774>] (gic_handle_irq+0x54/0x94)
(gic_handle_irq) from [<c030c910>] (__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: <stable@vger.kernel.org>
Fixes: 94a6d5cf7caa ("iio:ak8975 Implement data ready interrupt handling")
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Tested-by: Gregor Boirie <gregor.boirie@parrot.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
---
 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 9c5c9ef3f1da..3b23a850c930 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;
-- 
2.8.0