[PATCH 4.4 66/79] iio: light: opt3001: fix mutex unlock race

From: Greg Kroah-Hartman
Date: Wed Oct 16 2019 - 18:20:45 EST

From: David Frey <dpfrey@xxxxxxxxx>

commit 82f3015635249a8c8c45bac303fd84905066f04f upstream.

When an end-of-conversion interrupt is received after performing a
single-shot reading of the light sensor, the driver was waking up the
result ready queue before checking opt->ok_to_ignore_lock to determine
if it should unlock the mutex. The problem occurred in the case where
the other thread woke up and changed the value of opt->ok_to_ignore_lock
to false prior to the interrupt thread performing its read of the
variable. In this case, the mutex would be unlocked twice.

Signed-off-by: David Frey <dpfrey@xxxxxxxxx>
Reviewed-by: Andreas Dannenberg <dannenberg@xxxxxx>
Fixes: 94a9b7b1809f ("iio: light: add support for TI's opt3001 light sensor")
Cc: <Stable@xxxxxxxxxxxxxxx>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

drivers/iio/light/opt3001.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

--- a/drivers/iio/light/opt3001.c
+++ b/drivers/iio/light/opt3001.c
@@ -646,6 +646,7 @@ static irqreturn_t opt3001_irq(int irq,
struct iio_dev *iio = _iio;
struct opt3001 *opt = iio_priv(iio);
int ret;
+ bool wake_result_ready_queue = false;

if (!opt->ok_to_ignore_lock)
@@ -680,13 +681,16 @@ static irqreturn_t opt3001_irq(int irq,
opt->result = ret;
opt->result_ready = true;
- wake_up(&opt->result_ready_queue);
+ wake_result_ready_queue = true;

if (!opt->ok_to_ignore_lock)

+ if (wake_result_ready_queue)
+ wake_up(&opt->result_ready_queue);