linux-kernel - RE: [PATCH] i2c: dev: prevent adapter retries being set as minus value

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Date:   Mon, 7 Jan 2019 12:36:15 +0000
From:   Zeng Yi（曾毅） <yizeng@...micro.com>
To:     Wolfram Sang <wsa@...-dreams.de>
CC:     "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] i2c: dev: prevent adapter retries being set as minus
 value

Hi Wolfram Sang,

Thank you very much for your review and kindly suggestions, would you please see my comments below:

Best Regards,
Yi Zeng
+86-21-60336588 ext. 8686


-----Original Message-----
From: Wolfram Sang [mailto:wsa@...-dreams.de] 
Sent: Friday, January 04, 2019 3:30 AM
To: Zeng Yi（曾毅）
Cc: linux-i2c@...r.kernel.org; linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i2c: dev: prevent adapter retries being set as minus value

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?
Yes, I am very glad to do this fix. I will add the changes to the previous patch.

> Signed-off-by: Yi Zeng <yizeng@...micro.com>
> ---
>  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.
Thank you, I will drop it in the updates.

> +		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.
Thank you very much for your suggestion, I think this is much better than the previous.

Kind regards,

   Wolfram