linux-kernel - Re: [PATCH 4/7] iio: as73211: copy/release available integration times to fix race

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Message-ID: <20241006151808.1310db7d@jic23-huawei>
Date: Sun, 6 Oct 2024 15:18:08 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Matteo Martelli <matteomartelli3@...il.com>
Cc: Lars-Peter Clausen <lars@...afoo.de>, Michael Hennerich
 <Michael.Hennerich@...log.com>, Alisa-Dariana Roman
 <alisa.roman@...log.com>, Christian Eggers <ceggers@...i.de>, Peter Rosin
 <peda@...ntia.se>, Paul Cercueil <paul@...pouillou.net>, Sebastian Reichel
 <sre@...nel.org>, linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-mips@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH 4/7] iio: as73211: copy/release available integration
 times to fix race

On Thu, 03 Oct 2024 19:34:09 +0200
Matteo Martelli <matteomartelli3@...il.com> wrote:

> While available integration times are being printed to sysfs by iio core
> (iio_read_channel_info_avail), the sampling frequency might be changed.
> This could cause the buffer shared with iio core to be corrupted. To
> prevent it, make a copy of the integration times buffer and free it in
> the read_avail_release_resource callback.
> 
> Signed-off-by: Matteo Martelli <matteomartelli3@...il.com>
> ---
>  drivers/iio/light/as73211.c | 23 ++++++++++++++++++++---
>  1 file changed, 20 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iio/light/as73211.c b/drivers/iio/light/as73211.c
> index be0068081ebbbb37fdfb252b67a77b302ff725f6..520c898e0ff9c530b4fdd45589559f9014d7992c 100644
> --- a/drivers/iio/light/as73211.c
> +++ b/drivers/iio/light/as73211.c
> @@ -493,17 +493,33 @@ static int as73211_read_avail(struct iio_dev *indio_dev, struct iio_chan_spec co
>  		*type = IIO_VAL_INT;
>  		return IIO_AVAIL_LIST;
>  
> -	case IIO_CHAN_INFO_INT_TIME:
> +	case IIO_CHAN_INFO_INT_TIME: {
>  		*length = ARRAY_SIZE(data->int_time_avail);
> -		*vals = data->int_time_avail;
>  		*type = IIO_VAL_INT_PLUS_MICRO;
> -		return IIO_AVAIL_LIST;
>  
> +		guard(mutex)(&data->mutex);
> +
> +		*vals = kmemdup_array(data->int_time_avail, *length,
> +				      sizeof(int), GFP_KERNEL);
> +		if (!*vals)
> +			return -ENOMEM;
> +
> +		return IIO_AVAIL_LIST;
> +	}
>  	default:
>  		return -EINVAL;
>  	}
>  }
>  
> +static void as73211_read_avail_release_res(struct iio_dev *indio_dev,
> +					   struct iio_chan_spec const *chan,
> +					   const int *vals, long mask)
> +{
> +	if (mask == IIO_CHAN_INFO_INT_TIME)
> +		kfree(vals);
> +}
> +
Trivial but one blank line is enough.  If there is no other feedback on the
series I can tidy this up whilst applying.

> +
>  static int _as73211_write_raw(struct iio_dev *indio_dev,
>  			       struct iio_chan_spec const *chan __always_unused,
>  			       int val, int val2, long mask)
> @@ -699,6 +715,7 @@ static irqreturn_t as73211_trigger_handler(int irq __always_unused, void *p)
>  static const struct iio_info as73211_info = {
>  	.read_raw = as73211_read_raw,
>  	.read_avail = as73211_read_avail,
> +	.read_avail_release_resource = as73211_read_avail_release_res,
>  	.write_raw = as73211_write_raw,
>  };
>  
>