From: Andreas Dannenberg <dannenberg@ti.com>
To: David Frey <dpfrey@gmail.com>
Cc: <linux-iio@vger.kernel.org>
Subject: Re: [PATCH] iio: light: opt3001: fix mutex unlock race
Date: Fri, 20 Sep 2019 12:40:37 -0500 [thread overview]
Message-ID: <20190920174037.6zfjcx36bejhoa5v@jiji> (raw)
In-Reply-To: <20190919225418.20512-1-dpfrey@gmail.com>
David,
On Thu, Sep 19, 2019 at 03:54:18PM -0700, David Frey wrote:
> 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@gmail.com>
> ---
Good find, thanks for the submission.
Reviewed-by: Andreas Dannenberg <dannenberg@ti.com>
--
Andreas Dannenberg
Texas Instruments Inc
> drivers/iio/light/opt3001.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iio/light/opt3001.c b/drivers/iio/light/opt3001.c
> index e666879007d2..92004a2563ea 100644
> --- a/drivers/iio/light/opt3001.c
> +++ b/drivers/iio/light/opt3001.c
> @@ -686,6 +686,7 @@ static irqreturn_t opt3001_irq(int irq, void *_iio)
> 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)
> mutex_lock(&opt->lock);
> @@ -720,13 +721,16 @@ static irqreturn_t opt3001_irq(int irq, void *_iio)
> }
> opt->result = ret;
> opt->result_ready = true;
> - wake_up(&opt->result_ready_queue);
> + wake_result_ready_queue = true;
> }
>
> out:
> if (!opt->ok_to_ignore_lock)
> mutex_unlock(&opt->lock);
>
> + if (wake_result_ready_queue)
> + wake_up(&opt->result_ready_queue);
> +
> return IRQ_HANDLED;
> }
>
> --
> 2.23.0
>
next prev parent reply other threads:[~2019-09-20 17:40 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-19 22:54 [PATCH] iio: light: opt3001: fix mutex unlock race David Frey
2019-09-20 17:40 ` Andreas Dannenberg [this message]
2019-10-05 15:09 ` Jonathan Cameron
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