linux-kernel - Re: [PATCH] hwmon:(stts751) buffer overread on wrong chip configuration

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Date:   Thu, 10 Aug 2017 09:15:22 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Anton Vasilyev <vasilyev@...ras.ru>
Cc:     Jean Delvare <jdelvare@...e.com>, linux-hwmon@...r.kernel.org,
        linux-kernel@...r.kernel.org, ldv-project@...uxtesting.org
Subject: Re: [PATCH] hwmon:(stts751) buffer overread on wrong chip
 configuration

On Thu, Aug 10, 2017 at 06:23:34PM +0300, Anton Vasilyev wrote:
> If stts751 hw by some reason reports conversion rate bigger then 9:
> 	ret = i2c_smbus_read_byte_data(priv->client, STTS751_REG_RATE);
> then dereference stts751_intervals[priv->interval] leads to buffer
> overread.
> 
> The path adds sanity check for value read from chip.
> 
> Found by Linux Driver Verification project (linuxtesting.org).
> 
> Signed-off-by: Anton Vasilyev <vasilyev@...ras.ru>
> ---
>  drivers/hwmon/stts751.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/hwmon/stts751.c b/drivers/hwmon/stts751.c
> index d56251d..f6eddbd 100644
> --- a/drivers/hwmon/stts751.c
> +++ b/drivers/hwmon/stts751.c
> @@ -718,6 +718,10 @@ static int stts751_read_chip_config(struct stts751_priv *priv)
>  	ret = i2c_smbus_read_byte_data(priv->client, STTS751_REG_RATE);
>  	if (ret < 0)
>  		return ret;
> +	if (ret > ARRAY_SIZE(stts751_intervals)) {

Great catch, but should this be >= ?

Guenter

> +		dev_err(priv->dev, "Unrecognized conversion rate 0x%x\n", ret);
> +		return -ENODEV;
> +	}
>  	priv->interval = ret;
>  
>  	ret = stts751_read_reg16(priv, &priv->event_max,
> -- 
> 2.7.4
>