Re: [PATCH] i2c: dev: prevent adapter retries being set as minus value

[Wolfram Sang]

Hi Yi Zeng,

On Fri, Dec 21, 2018 at 05:32:06PM +0800, Yi Zeng wrote:
> If set adapter->retries to minus value from user space via ioctl,
> will make __i2c_transfer and __i2c_smbus_xfer jump the calling to
> adapter->algo->master_xfer and adapter->algo->smbus_xfer that
> registered by the underlying bus drivers, and return value 0 to
> all the callers. The bus driver will never be accessed anymore by
> all users, besides, the users may still get successful return value
> with no any error or information log print out.

Thanks! The issue you observed is correct. It also applies to
I2C_TIMEOUT. Would you mind fixing it there as well?

> Signed-off-by: Yi Zeng <yizeng@xxxxxxxxxxxx>
> ---
>  drivers/i2c/i2c-dev.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c
> index 1aca742..c349f58 100644
> --- a/drivers/i2c/i2c-dev.c
> +++ b/drivers/i2c/i2c-dev.c
> @@ -470,6 +470,14 @@ static long i2cdev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
>  					  data_arg.data);
>  	}
>  	case I2C_RETRIES:
> +		/*
> +		 * The adapter->retries is defined as int type, and as
> +		 * the upper limit for times of i2c transfer retry when
> +		 * get -EAGAIN, it should not be set as minus value.
> +		 */

I usually like comments explaining the situiation. However, here I think
it is pretty clear that the code does just sanity checks. So, I think we
can drop it.

> +		if ((int)arg < 0)
> +			return -EINVAL;

Minor nit: I'd think this is a little more readable

	if (arg > INT_MAX)
			return -EINVAL

But I have no strong opinion here.

Kind regards,

   Wolfram

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