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iio: ak8975: Fix NULL pointer exception on early interrupt
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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 torvalds#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: <[email protected]>
Fixes: 94a6d5c ("iio:ak8975 Implement data ready interrupt handling")
Signed-off-by: Krzysztof Kozlowski <[email protected]>
Tested-by: Gregor Boirie <[email protected]>
Signed-off-by: Jonathan Cameron <[email protected]>
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@krzk @jic23
krzk authored and jic23 committed Apr 17, 2016
1 parent bf16200 commit 07d2390
Showing 1 changed file with 2 additions and 2 deletions.
4 changes: 2 additions & 2 deletions drivers/iio/magnetometer/ak8975.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand All @@ -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;
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