linux-kernel - Re: [PATCH v2] iio: magnetometer: rm3100: add boundary check for the value read from RM3100_REG

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Date: Mon, 1 Jan 2024 18:05:49 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: zhouzhouyi@...il.com
Cc: songqiang1304521@...il.com, lars@...afoo.de, linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org, "zhili.liu" <zhili.liu@...s.com.cn>
Subject: Re: [PATCH v2] iio: magnetometer: rm3100: add boundary check for
 the value read from RM3100_REG_TMRC

On Sun, 31 Dec 2023 22:56:44 +0800
zhouzhouyi@...il.com wrote:

> From: "zhili.liu" <zhili.liu@...s.com.cn>
> 
> Recently, we encounter kernel crash in function rm3100_common_probe
> caused by out of bound access of array rm3100_samp_rates (because of
> underlying hardware failures). Add boundary check to prevent out of
> bound access.
> 
> Suggested-by: Zhouyi Zhou <zhouzhouyi@...il.com>
> Signed-off-by: zhili.liu <zhili.liu@...s.com.cn>
Please provide a Fixes tag so we know how far back to backport this.

Seems like a reasonable bit of hardening against potential hardware issues.
However it would be cleaner with a local variable used for the index.
See inline.


Jonathan

> ---
> The format of the previous patch was a bit problematic,
> we are sending it again.
> 
> Sorry for the trouble.
> 
> Thank you very much.
> --
>  drivers/iio/magnetometer/rm3100-core.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/iio/magnetometer/rm3100-core.c b/drivers/iio/magnetometer/rm3100-core.c
> index 69938204456f..fc50b6d4a334 100644
> --- a/drivers/iio/magnetometer/rm3100-core.c
> +++ b/drivers/iio/magnetometer/rm3100-core.c
> @@ -586,6 +586,12 @@ int rm3100_common_probe(struct device *dev, struct regmap *regmap, int irq)
>  	ret = regmap_read(regmap, RM3100_REG_TMRC, &tmp);
>  	if (ret < 0)
>  		return ret;
> +
> +	if (tmp < RM3100_SAMP_NUM || tmp - RM3100_TMRC_OFFSET >= RM3100_SAMP_NUM) {
Just a local variable of
int samp_rate_index = tmp - RM3100_TMRC_OFFSET;
Check that for negative or >=  RM3100_SAMP_NUM 
> +		dev_err(dev, "The value read from RM3100_REG_TMRC is invalid!\n");
> +		return -EINVAL;
> +	}
> +
>  	/* Initializing max wait time, which is double conversion time. */
>  	data->conversion_time = rm3100_samp_rates[tmp - RM3100_TMRC_OFFSET][2]
>  				* 2;