linux-kernel - Re: [PATCH] iio: chemical: sps30: Add Null pointer check

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Message-ID: <20241019122133.13d59dfb@jic23-huawei>
Date: Sat, 19 Oct 2024 12:21:33 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Karan Sanghavi <karansanghvi98@...il.com>
Cc: Tomasz Duszynski <tduszyns@...il.com>, Lars-Peter Clausen
 <lars@...afoo.de>, linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
 Shuah Khan <skhan@...uxfoundation.org>, Karan Sanghavi
 <karansanghavi98@...il.com>
Subject: Re: [PATCH] iio: chemical: sps30: Add Null pointer check

On Fri, 18 Oct 2024 18:54:42 +0000
Karan Sanghavi <karansanghvi98@...il.com> wrote:

> Add a Null pointer check before assigning and incrementing
> the null pointer
> 
> Signed-off-by: Karan Sanghavi <karansanghvi98@...il.com>

It would be a bug if rsp_size was anything other than 0 and rsp is NULL.
So this looks like a false positive as the loop will never be
entered.

How did you find it, in particular have you managed to trigger this
in the driver?

Jonathan


> ---
>  drivers/iio/chemical/sps30_i2c.c | 20 +++++++++++---------
>  1 file changed, 11 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/iio/chemical/sps30_i2c.c b/drivers/iio/chemical/sps30_i2c.c
> index 1b21b6bcd0e7..d2142e4c748c 100644
> --- a/drivers/iio/chemical/sps30_i2c.c
> +++ b/drivers/iio/chemical/sps30_i2c.c
> @@ -105,16 +105,18 @@ static int sps30_i2c_command(struct sps30_state *state, u16 cmd, void *arg, size
>  		return ret;
>  
>  	/* validate received data and strip off crc bytes */
> -	tmp = rsp;
> -	for (i = 0; i < rsp_size; i += 3) {
> -		crc = crc8(sps30_i2c_crc8_table, buf + i, 2, CRC8_INIT_VALUE);
> -		if (crc != buf[i + 2]) {
> -			dev_err(state->dev, "data integrity check failed\n");
> -			return -EIO;
> +	if (rsp) {
> +		tmp = rsp;
> +		for (i = 0; i < rsp_size; i += 3) {
> +			crc = crc8(sps30_i2c_crc8_table, buf + i, 2, CRC8_INIT_VALUE);
> +			if (crc != buf[i + 2]) {
> +				dev_err(state->dev, "data integrity check failed\n");
> +				return -EIO;
> +			}
> +
> +			*tmp++ = buf[i];
> +			*tmp++ = buf[i + 1];
>  		}
> -
> -		*tmp++ = buf[i];
> -		*tmp++ = buf[i + 1];
>  	}
>  
>  	return 0;
> 
> ---
> base-commit: f2493655d2d3d5c6958ed996b043c821c23ae8d3
> change-id: 20241018-cid1593398badshift-9c512a3b92d9
> 
> Best regards,